KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY

COLLEGE OF AGRICULTURE AND NATURAL RESOURCES

DEPARTMENT OF FISHERIES AND WATERSHED MANAGEMENT

HEAVY METAL CONCENTRATION IN THE SEDIMENTS AND FLESH OF BOE DRUM (Pteroscion peli) AND GREATER

AMBERJACK (Seriola dumerili) FROM THE KORLE LAGOON ESTUARY, ACCRA, GHANA.

A THESIS SUBMITTED TO THE FACULTY OF RENEWABLE NATURAL RESOURCES IN PARTIAL FULFILMENT OF THE

REQUIRMENTS FOR THE AWARD OF BACHELOR OF SCIENCE DEGREE IN NATURAL RESOURCE MANAGEMENT

ABOAGYE HACKMAN RICHARD

MAY 2012

i

ABSTRACT

The Korle Lagoon in Accra, Ghana, has become one of the most polluted water bodies on

earth. Different aquatic organisms often respond to external contamination in different

ways, where the quantity and form of the element in water, sediment, or food will

determine the degree of accumulation. The concentration of copper (Cu), Lead (Pb), Zinc

(Zn), and Cadmium (Cd) in the flesh of Pteroscion peli and Seriola dumerili were

assessed from October 2011 to January 2012. Eight fishes were sampled for each fish

species. Sediments were taken from three different sites on a monthly basis at the estuary

of the Korle lagoon. Samples collected were digested with a di-acid of the ratio 9; 4 of

nitric acid and perchloric acid respectively. Heavy metal was determined using the

Atomic Adsorption Spectrophometer (AAS). Heavy metal concentrations in sediment

were below the National Oceanic and Atmospheric Administration (NOAA) Sediment

Quality Guideline for Estuaries over the period and ranked in the order: Pb> Zn> Cu>

Cd. The result of this research showed that heavy metals were continuously deposited and

removed from sediments into the water column of the Korle lagoon estuary. Also the

study indicated that the levels of metal in the flesh of Seriola dumerili and Pteroscion

peli were low for, copper and zinc but higher for Lead and Cadmium as compared to the

World Health Organization Standard (2005). Heavy metal concentrations in the flesh of

S. Dumerili and P. peli in relation to size revealed that both sizes accumulated higher lead

and cadmium concentrations and lower Zinc and Copper concentration. The present study

showed that consumption of fish from the Korle Lagoon estuary should be prohibited and

should be discouraged because of the high levels of Pb and Cd in the flesh of Seriola

dumerili and Pteroscion peli in both small and large sizes.

ii

ACKNOWLEDGMENT

I thank the most high God for the strength and calm through the perplexing times during my

study.

I wish to express my deepest appreciation to my supervisor, Dr Nelson W Agbo, for his

invaluable comments and excellent supervision. I must also thank him for the cordial relations

showed towards me, which was very helpful and very much cherished.

My thanks also goes to Mr Kwasi Adu Obirikorang for being my second supervisor, assisting me

on field, laboratory and in putting this together.

I wish to thank Mr Napoleon Jackson and Mr Douglas for their assistance in the laboratory. I

thank my mum, Miss Monica Hackman so much for her inspiration, motivation and financial

assistance in putting this thesis together. My thanks also go to the entire membership of Christ

Apostolic Church, Odorkor Official Town Assembly for their prayers into this dissertation.

My sincere thanks also go to the following persons Mary Abena Yamoah, Enoch Adjei Mensah

and Solomon Antwi for their diverse assistance in the preparation of this dissertation.

My special thanks go to Mr. Daniel, Maame Awotwe, Sister Violet and all fishers of the Korle

Lagoon Estuary.

iii

TABLE OF CONTENT

CONTENT PAGE

ABSTRACT.............................................................................................................................ii

ACKNOWLEDGEMENT.....................................................................................................iii

TABLE OF CONTENT…………………………………………………………………………………….iv

LIST OF TABLES.................................................................................................................vii

LIST OF PLATES................................................................................................................viii

LIST OF FIGURES................................................................................................................ix

1.0. INTRODUCTION...................................................................................................1

1.1. Justification............................................................................................................3

1.2. OBJECTIVES........................................................................................................5

2.0. LITERATURE REVIEW.....................................................................................6

2.1. Global Water Pollution.........................................................................................6

2.1.1. Environmental Aquatic Pollution...................................................................8

2.2. Heavy Metals..........................................................................................................9

2.2.1. Source of Heavy Metals................................................................................10

2.2.2. Sediments and Heavy Metals in Estuaries....................................................11

2.3. Some Common Heavy Metals.............................................................................12

2.3.1. Copper...........................................................................................................12

2.3.2. Lead..............................................................................................................14

2.3.3. Zinc...............................................................................................................15

2.3.4. Cadmium.......................................................................................................16

2.4. Bio-Importance of Heavy Metals to Humans....................................................17

2.4.1. Effect of bioaccumulation on humans..........................................................18

2.5. Lagoon Pollution in Ghana.................................................................................20

2.6. State of the Korle lagoon.....................................................................................21

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2.6.1. Heavy metal sources to the lagoon...............................................................22

2.6.2. Effect of Korle lagoon pollution...................................................................23

2.6.3. Activities at the estuary................................................................................24

2.7. Fish Species...........................................................................................................24

2.7.1. Seriola spp....................................................................................................25

2.7.2. Pteroscion peli..............................................................................................26

3.0. METHODOLOGY..............................................................................................28

3.1. Description of the study area..............................................................................28

3.2. Sample collection.................................................................................................29

3.3. Heavy Metal Analysis..........................................................................................32

3.3.1. Sample Digestion..........................................................................................33

3.3.2. Sediment digestion........................................................................................34

3.3.3. Determination of heavy metal concentration................................................35

3.3.4. Measurement of Physicochemical Water Parameters...................................36

4.0. RESULTS.............................................................................................................37

4.1. Heavy metal concentrations in Sediment Samples...........................................37

4.2. Heavy metal concentrations in Pteroscion peli.................................................38

4.3. Heavy metal concentration in Seriola dumerili................................................40

4.4. Heavy metals in the flesh of P. peli and the S. dumerili in relation to sizes. . .41

4.4.1. Pteroscion peli..............................................................................................42

4.4.2. Seriola dumerili............................................................................................43

4.5. Physicochemical Parameters of the Korle lagoon.............................................44

5.0. DISCUSSION.......................................................................................................45

5.1. Heavy Metal Concentration in Sediments.........................................................45

5.2. Heavy Metal effect in fish species.......................................................................47

5.3. Variation in Metal Concentrations in Relation to Body Size..........................48

6.0. CONCLUSIONS..................................................................................................49

6.1. RECOMMENDATIONS....................................................................................49v

REFERENCES..................................................................................................................51

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LIST OF TABLES

TABLE PAGE

Table 4.1 Heavy metal concentration (μg/g ww) concentration in the sediment

from the Korle lagoon estuary.............................................................. 37

Table 4.2 Heavy metal concentration (μg/g ww) in the flesh of Pteroscion peli

from the Korle lagoon estuary............................................................... 38

Table 4.3 Heavy metal concentration (μg/g ww) in the flesh of Seriola dumerili

from the Korle lagoon estuary....... ...................................................... 40

Table 4.4 Physiochemical parameters ......................................................................43

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LISTS OF PLATES

PLATES PAGE

Plate 1 Pteroscion peli ……………………………………………………………..

29

Plate 2 Seriola dumerili ………………………………………………………….... 29

Plate 3 Beach seining at the Korle lagoon estuary ……………………………..... 30

Plate 4 Obtaining samples from fishers ………………………………………….. 30

Plate 5 Some Pteroscion peli obtained …………………………………………… 30

Plate 6 Some Seriola dumerili obtained ………………………………………….. 30

Plate 7 Sampling point (A) ……………………………………………………….. 31

Plate 8 Sampling point (B) ……………………………………………………….. 32

Plate 9 Sampling point (C) ……………………………………………………….. 32

Plate 10 Total length of Seriola dumerili being taken …………………………… 33

Plate 11 Sediment being air dried ………………………………………………… 34

Plate 12 some containers containing digested sample …………………………... 35

Plate 13 Water quality parameter being taken insutu ………………………... 36

viii

LISTS OF FIGURES

FIGURES PAGE

Fig 3.1 Study area and its environs..............................................................................28

Fig 4.1 Variation in Cu, Pd, Cd and Zn concentration in the flesh of Pteroscion peli

from the Korle lagoon estuary.........................................................................41

Fig 4.2 Variation in Cu, Pb, Cd and Zn concentration in the flesh of Seriola dumerili

from the Korle lagoon estuary.........................................................................42

ix

CHAPTER ONE

1.0. INTRODUCTION

The coastline of Ghana is abundantly endowed with many lagoonal resources and is of

major significance for domestic, spiritual and economic activities. In recent times, the

coast of Ghana is encountering serious environmental challenges. These problems are in

response to rapid demographic changes and growth of industrial activities along the

coast. This development has coincided with the establishment of human settlements

which lack credible sanitary infrastructure to give adequate support to waste disposal

(Karikari, 2005). This has led to degradation of water quality leading to loss of the

ecological integrity of most lagoons.

Korle lagoon is one such lagoon in Accra, Ghana which used to support a vibrant

artisanal fishery with attendant socio-economic activities for the communities living

around the lagoon up to the 1980’s when uncontrolled pollution from domestic and

industrial sources severely impacted on the Lagoon’s fishery and nearly led to its

collapse. According to Entsua-Mensah et al. (2004), the Korle Lagoon estuary still

supports artisanal fisheries which play an important role in the economy of some coastal

inhabitants, especially during the off-season for marine fishing. The Lagoon also serves

as breeding grounds for some fish species.

Heavy metals are intrinsic, natural constituents of our environment. They are generally

present in small amounts in natural aquatic environments. Apart from the natural sources,

several anthropogenic activities also contribute to metal concentrations in the

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environment (Woo, et al., 1993). An activity that massively contributes to the pollution

of the lagoon with heavy metal is the local and crude methods of recycling electronic

waste (e-waste) to retrieve its metallic components. According to Aanstoos et al (1998)

electronic waste consist of 32 different metals at different percentage mass. An

excessively high metal concentration in the sediments of Korle lagoon has been reported

(Greenpeace 2008).

Copper and Zinc were selected based their importance to living organisms. Lead and

Cadmium was selected base on their toxicity in small concentrations.

Different aquatic organisms often respond to external contamination in different ways,

where the quantity and form of the element in water, sediment, or food will determine the

degree of accumulation (Begum et al., 2009).

The degree of contamination depend on pollutant type, fish species, sampling location,

trophic level and their mode of feeding (Asuquo et al. 2004).

Species in relatively low trophic levels are exposed to comparatively lower heavy metal

concentration. Fishes in the upper food web position are prone to accumulate more heavy

metals through bio magnification (Al- Yousuf et al 2000) contamination, although plants

can accumulate metals in high levels (Peakall et al 2003).

2

1.1. Justification

The Korle Lagoon in Accra, Ghana, has become one of the most polluted water bodies on

earth. It is the principal outlet through which all major drainage channels in the city

empty their wastes into the sea. Large amounts of untreated industrial waste emptied into

surface drains has led to severe pollution in the lagoon and disrupted its natural ecology.

The increased levels of industrial activity and consumption by the urban population lead

to the generation of copious quantities of waste (Boadi & Kuitunen. 2002).

Agbogbloshie, a suburb of Ghana’s capital, Accra, and just adjacent the lagoon is a

known destination for legal and illegal  electronic waste (e-waste) dumping from

industrialized nations, often referred to as a "digital dumping ground". Millions of tons of

e-waste are processed each year in the local recycling workshops. A study by Greenpeace

(2008) revealed excessively high metal concentrations in the soils of the open burning

grounds and in the sediments of the lagoon.

Contaminated sediments do not always remain at the bottom of a water body. Anything

that stirs up the water, such as dredging and upwelling, can resuspend sediments.

Resuspension may mean that all animals in the water, and not just the bottom-dwelling

organisms, will be directly exposed to toxic contaminants (Begum, et al., 2009).

Fishes often accumulate large amounts of these metals in polluted areas. They assimilate

these heavy metals through ingestion of suspended particulates, food materials and

sometimes by constant ion exchange process of dissolved metals across lipophilic

3

membranes like the gills and adsorption of dissolved metals on tissue and membrane

surfaces (Begum, et al., 2009). Bio magnification can result in fish at the top of food chain

containing hundreds more heavy metals than it appears in the water or in any single fish

they eat.

Seriola dumerili and Pteroscion peli are important fish species in the Korle lagoon

fishery and are in high demand by the inhabitants of Accra especially those around the

Korle lagoon. Inhabitants often prefer large sizes of Seriola dumerili and small sizes of

Pteroscion peli. Since these species are carnivores they could possibly accumulate heavy

metals which could be detrimental to those who consume them.

In small quantities, certain heavy metals are nutritionally essential for a healthy life.

Some of these are referred to as the trace elements (e.g., iron, copper, manganese, and

zinc). These elements, or some form of them, are commonly found naturally in

foodstuffs, in fruits and vegetables, and in commercially available multivitamin products

(International Occupational Safety and Health Information Centre, 1999) but high

quantities of these toxic metals may cause defects like memory loss, high blood pressure,

poor concentration, aggressive behaviour, sleeplessness and a number of other defects

(Aneum, 2010).

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1.2. OBJECTIVES

Based on the above reasons the objectives of this study were:

To assess the concentration of zinc, lead, copper and cadmium in the sediment and flesh

of Pteroscion peli and Seriola dumerili.

To examine variations in heavy metal concentration in the flesh of the Pteroscion peli

and Seriola dumerili in relation to size.

5

CHAPTER 2

2.0. LITERATURE REVIEW

2.1. Global Water Pollution

Every day, 2 million tons of sewage, industrial and agricultural waste is discharged into

the world’s water (UN-WWAP, 2003), the equivalent of the weight of the entire human

population of 6.8 billion people. The UN estimates that the amount of wastewater

produced annually is about 1,500 km3, six times more water than exists in all the rivers

of the world (UN-WWAP, 2003). Lack of adequate sanitation contaminates water

courses worldwide and is one of the most significant forms of water pollution.

Worldwide, 2.5 billion people live without improved sanitation (UNICEF and WHO,

2008). Over 70% of these people, who lack sanitation, live in Asia. Sub-Saharan Africa is

slowest of the world’s regions in achieving improved sanitation: only 31 percent of

residents have access to improved sanitation in 2006. Eighteen percent of the world’s

population, or 1.2 billion people, defecate in the open. Open defecation significantly

compromises quality in nearby water bodies and poses an extreme human health risk

(UNICEF and WHO, 2008).

The effects of water pollution is said to be the leading cause of death for humans

across the globe, moreover, water pollution affects our oceans, lakes, rivers, and

drinking water, making it a widespread and global concern (Scipeeps, 2009). Since

the population of cities in the developing world are rising rapidly (Grobicki, 2001) and

in-order to meet the ever increasing demand for food, other services for human

6

development including rapid urbanization and industrial growth, many unplanned

interventions have been made in water bodies in many parts of the world (Vass, 2007).

Polluted water consists of Industrial discharged effluents, sewage water, rain water

pollution (Ashraf et al, 2010) and pollution by agriculture or households cause

damage to human health or the environment (European Public Health Alliance, 2009).

This water pollution affects the health and quality of soils and vegetation, (Carter, 1985).

Some water pollution effects are recognized immediately, whereas others don’t show

up for months or years (Ashraf et al, 2010). There has been widespread decline in

biological health in inland (non-coastal) waters. Globally, 24 percent of mammals and 12

percent of birds connected to inland waters are considered threatened (UN-WWAP,

2003).

In some regions, more than 50% of native freshwater fish species are at risk of extinction,

and nearly one-third of the world’s amphibians are at risk of extinction. Freshwater

ecosystems sustain a disproportionately large number of identified species, but are

increasingly threatened by a host of water quality problems (Vié et al, 2009).

Seventy percent of industrial wastes in developing countries are disposed of untreated

into waters where they contaminate existing water supplies, (UN-Water, 2009). Roughly

one unit of mercury is emitted into the environment for every unit of gold produced by

small-scale miners; a total of as much as 1000 tons of mercury is emitted each year

(UNEP/GRID-Arendal, 2009).

7

2.1.1. Environmental Aquatic Pollution

The pressure of increasing population, growth of industries, urbanization, energy

intensive life style, loss of forest cover, lack of environmental awareness, lack of

implementation of environmental rules and regulations and environment improvement

plans, untreated effluent discharge from industries and municipalities, use of non-

biodegradable pesticides/fungicides/ herbicides/insecticides, use of chemical fertilizers

instead of organic manures, etc are causing water pollution. The pollutants from

industrial discharge and sewage besides finding their way to surface water reservoirs and

rivers are also percolating into the ground to pollute ground water sources (Trivedi,

2008).

The polluted water may have undesirable colour, odour, taste, turbidity, organic matter

contents, harmful chemical contents, toxic and heavy metals, pesticides, oily matters,

industrial waste products, radioactivity, high Total Dissolved Solids (TDS), acids,

alkalises domestic sewage content, virus, bacteria, protozoa, rotifers, worms, etc. The

organic content may be biodegradable or non-biodegradable. Pollution of surface waters

(rivers, lakes, and ponds), ground waters, and sea water are all harmful for human and

animal health. Pollution of the drinking water and that of food chain is by far the most

worry-some aspect (Kant, 2005).

Toxic chemical substances introduced into the environment may be transported by

the air, water and living organisms and may become a part of the natural

biogeochemical cycle and accumulate in the food chain (Gadzała-Kopciuch, 2004).

Some of the pollutants like lead (Pb), arsenic (As), mercury (Hg), chromium (Cr)

specially hexavalent chromium, nickel (Ni), barium (Ba), cadmium (Cd), cobalt (Co),

8

selenium (Se), vanadium (V), oils and grease, pesticides, etc are very harmful, toxic and

poisonous even in ppb (parts per billion) range (Lucky, 2002). There are some minerals

which are useful for human and animal health in small doses beyond which these are

toxic. Zinc (Zn), copper (Cu), iron (Fe), etc fall into this category. For agriculture, some

elements like zinc, copper, manganese (Mn), sulphur (S), iron, boron (B), together with

phosphates, nitrates, urea, potassium, etc are useful in prescribed quantities. There are

some compounds like cyanides, thiocyanides, phenolic compounds, fluorides, radioactive

substances, etc which are harmful for humans as well as animals (Kudesia, 2002).

Water bodies contaminated by heavy metals may lead to bioaccumulation in the food

chain of an estuarine environment. Such contaminants are transported from its sources

through river system and deposited downstream. Since most of the pollutants could be

mixed and become suspended solid and bottom sediment through sedimentation,

therefore estuary is a potential sink for these pollutants over a long period of time

(Morrisey et al., 2003).

2.2. Heavy Metals

Heavy metals are metals or, in some cases, metalloids which are stable and have a density

greater than 4.5 g/cm 3 and their compounds (UNECE, 1998).

Low concentration of metals in water might not necessary reflect that the area is pollution

free. The biotic life in such an area might have accumulated the metals from water from

time to time. Such a situation could be observed from the higher concentration of heavy

metals in the tissue of organisms found in the estuary (Abdullah, 2007).

9

Higher concentrations of heavy metals (such as Cd, Pb, Cu and Zn) in the sediment of an

estuary concur with the pattern of those metals found in the tissues of estuary organisms

(Abdullah, 2007).

2.2.1. Source of Heavy Metals

Heavy metals differ in their chemical properties, and are used widely in electronic

components, machinery and materials. Consequently, they are emitted to the environment

from a variety of anthropogenic sources to supplement natural background geochemical

sources. Some of the oldest cases of environmental pollution in the world were caused by

heavy metal extraction and use, for example, copper, mercury and lead mining, smelting

The amounts of most heavy metals deposited to the surface of the Earth are many times

greater than depositions from natural background sources. Combustion processes are the

most important sources of heavy metals, particularly, power generation, smelting,

incineration and the internal combustion engine (Battarbee, 1988).

Common Metals and their sources also include:

Lead: leaded gasoline, tire wear, lubricating oil and grease, bearing wear

Zinc: tire wear, motor oil, grease, brake emissions, corrosion of galvanized parts

Copper: bearing wear, engine parts, brake emissions

Cadmium: tire wear, fuel burning, batteries (Kiliç, 2011).

10

2.2.2. Sediments and Heavy Metals in Estuaries

Estuaries are important zones of sediment transfer between fluvial and marine systems,

often forming sinks for sediment moving downstream, alongshore or landwards and

consequently for dissolved and particulate contaminants from recreational, farming,

manufacturing and extractive industries, both on land and offshore (Morrisey et al, 2003).

Heavy metals in sediments represent a combinational effect of chemical, biological and

physical processes occurring in fluvial, estuarine, and coastal environments. Surface

sediments integrate these changes that occur in the water column and act both as a

repository and source of suspended materials. Spatial variations of heavy metals in the

surface sediments are the results of these processes (Lin, et al, 2003).

Heavy metals generally exist in two phases in estuarine waters, i.e., in the dissolved

phase in the water column and in the particulate phase adsorbed on the sediments. The

behaviour of heavy metals in the aquatic environment is strongly influenced by

adsorption to organic and inorganic particles. The dissolved fraction of heavy metals may

be transported through the water column via the processes of advection and dispersion,

while the particulate fraction may be transported with the sediments, which are governed

by sediment dynamics. The partition of heavy metals between the dissolved and adsorbed

particulate phases depends on the physical and chemical characteristics of the suspended

particles as well as various ambient conditions, such as: salinity, pH, and the types and

concentrations of dissolved organic matter (Wu et al., 2005).

11

Fine sediments, acting as a source (or sink) for the organic chemical and heavy metals

entering (or leaving) the water column with sediments contaminated by the heavy metals,

pose a potential threat to the aquatic environment. Resuspension of contaminated bed

sediments caused by strong tidal currents may release a significant amount of heavy

metals into the water column, and this desorption of contaminants from their particulate

phase can have a pronounced impact on the aquatic environment and ecosystem (Zagar,

2006).

Although estuaries are sinks for contaminants from the terrestrial environment, there is

significant transport of marine material up-estuary as bed load sediment whilst fine-

grained terrestrial material may be transported seawards in suspension. Major movement

of contaminants from estuaries onto the continental shelf probably occurs only during

floods and storms and, in general, the impact on shelf seas is relatively minor and

confined to the coastal zone (Ridgway et al, 2000).

2.3. Some Common Heavy Metals

Several metals are found in the ecosystem in trace amounts and these metals are of great

importance to living organisms.

2.3.1. Copper

Copper exist in the natural water system either in the form as the cupric (Cu 2+) ion or

complexes with inorganic anions or organic ligands or as a suspended particle when

present as precipitates or absorbed to organic matter ( Mance et al 1984). It can also be

12

adsorbed to bottom sediments or exist as settled precipitate. The concentration of each of

these forms depends on complex interaction of many variables including the

concentration of copper and hardness, alkalinity, salinity, pH and concentration of

bicarbonate, bicarbonate sulphide, phosphate organic ligands and other metal ions.

Copper is an essential element to all living organisms, and because of that both

deficiency and excess have consequence for the integrity of biochemical functions. The

main biological role of copper is as an ingredient, normally in the prosthetic group, of

oxidizing enzymes which are important in oxidation-reduction processes (Moolenaar,

1998).

Complexes formed by copper are more stable than other metals such as cadmium, lead

and zinc. The high concentration of particulate matter in most estuaries will facilitate

removal of copper from solution by adsorption to suspended particles which in turn may

be deposited and accumulate in sediments.

Estuarine sediments are thought to be the most important depositional site for particulate

copper transported from rivers, although remobilization may occur when sediments is

disturbed. The remaining dissolve copper in the water column is likely to be present

either as an organic complex or as a cupric ion. Copper in the cupric form is the most bio

available (Grimwood, 1997). Copper is readily accumulated by plants and animals.

Whole –body concentration tends to decrease with increasing trophic level. it is also

regulated or immobilized in many species and is not biomagnified in food chains to any

significant extent (CCREM.,1987).

13

2.3.2. Lead

Lead is a micro element naturally present in trace amounts in all biological materials,

thus, in soil, water, plants and animals. It has no physiological function in the organism.

Some sources of lead pollution are those emanating from anthropogenic activities such as

smelting works, application of wastewater treatment sludges to soil, transportation and

also from surface runoffs. Lead pollution sources can also be extended to paints, lead

wastes, cell batteries and lead solders and most do enter the organism through

contaminated food and air (Boakye, 2011). The maximum acceptable toxicant limit for

inorganic lead has been determined for several species under different conditions and

results range from 0.04 mg l-1 to 0.198 mg l-1. The acute toxicity of lead is highly

dependent on the presence of other ions in solution, and the measurement of dissolved

lead in toxicity tests is essential for a realistic result. Organic compounds of lead are more

toxic to fish than inorganic lead salts (WHO, 1995). Lead accumulates in sediments and

can pose a hazard to sediment-dwelling organisms at concentrations above 30.2 mg kg-1,

(according to Canadian Interim Marine Sediment Quality Guidelines).

In aquatic ecosystems, uptake by primary producers and consumers seems to be

determined by the bioavailability of the lead. The uptake and accumulation of lead by

aquatic organisms from water and sediment are influenced by various environmental

factors, such as temperature, salinity, and pH, as well as humic and alginic acid content.

In many organisms, it is unclear whether lead is adsorbed onto the organism or actually

taken up. Consumers take up lead from their contaminated food, often to high

concentrations, but without biomagnifications (WHO 1995).

14

Lead uptake by fish reaches equilibrium only after a number of weeks of exposure. Lead

is accumulated mostly in gill, liver, kidney, and bone. Fish eggs show increasing lead

levels with increased exposure concentration, and there are indications that lead is present

on the egg surface but not accumulated in the embryo. Also young stages of fish are more

susceptible to lead than adults or eggs. Typical symptoms of lead toxicity include spinal

deformity and blackening of the caudal region. In contrast to inorganic lead compounds,

tetra alkyl lead is rapidly taken up by fish and rapidly eliminated after the end of the

exposure (WHO 1995).

2.3.3. Zinc

Zinc is one of the most ubiquitous and mobile heavy metals and is transported in natural

waters in both dissolved forms and associated with suspended particles (Mance et al,

1989). In estuaries where concentration of suspended particles is greater, zinc

accumulates particularly in anaerobic sediments. A greater proportion is adsorbed to the

suspended particles (CCREM, 1987).

In low salinity areas of estuaries, zinc can be mobilized on particles by microbial

degradation of organic matter and displacement by calcium and magnesium. In high

turbidity, greater levels of zinc associated with suspended sediments is deposited with

flocculated particles where it can and where it can particularly accumulate in anaerobic

sediments. The toxicity and bioaccumulation of zinc is greater at lower salinity (Hunt et

al, 1992) and invertebrates generally have high concentrations than fish species. Zinc

accumulates in sediments and can pose hazard to sediment dwelling organisms at

concentration above 125mg/kg.

15

Zinc is an essential element for many marine organisms and as such is readily bio

accumulated. Several species of crustaceans are able to regulate the uptake of zinc but at

higher concentration, this process appears to breakdown leading to an influx of zinc also

according to (NAS, 1979), gills of fish are physically damaged by high concentrations of

zinc. Organisms can take up zinc which is reflected in the bioaccumulation factor but

may not reflect in the tissue (Hunt et al 1992).

2.3.4. Cadmium

Cadmium is a relatively volatile element not essential to plants, animals and humans. Its

presence in organisms is unwanted and harmful. An increased level of cadmium in the

air, water and soil increases its uptake by organisms (Järup, 2003). Cadmium uptake from

water by aquatic organisms is extremely variable and depends on the species and various

environmental conditions, such as water hardness (notably the calcium ion and zinc

concentration), salinity, temperature, pH, and organic matter content. The majority of

chelating agents decrease cadmium uptake but some, such as dithiocarbamates and

xanthates, increase uptake. Increasing temperature increases the uptake and toxic impact,

whereas increasing salinity or water hardness decreases them. Acute lethal effects for

marine organisms have been noted as low as 16 µg l-1 (WHO ,1992). Cadmium is

toxic because it has some similarities with zinc that is an essential element; it is a typical

example of a cumulative poison (Järup, 2003). Cadmium is toxic to a wide range of

micro-organisms. The presence of sediment, high concentrations of dissolved salts or

organic matter all reduces the toxic impact. The main effect is on growth and replication.

16

An increase in toxicity as temperature increases and salinity decreases has been noted.

This implies that the same cadmium concentration may have the potential to cause

greater toxicity to estuarine rather than to marine species. At low concentrations (10

µg cadmium l-1), cadmium inhibits ion transport systems and induces

metallothionein synthesis (< 1 &micro;g cadmium l-1) in freshwater fish. Cadmium

toxicity has been found to be variable in fish, with salmonids being particularly

susceptible to cadmium. Sub-lethal effects in fish, notably malformation of the spine,

have been reported. The most susceptible life-stages are the embryo and early larva,

while eggs are the least susceptible. There is no consistent interaction between cadmium

and zinc in fish (WHO 1992). Cadmium bio accumulates in organisms with the main

uptake routes being dissolved cadmium from the water column and cadmium associated

with prey items.

2.4. Bio-Importance of Heavy Metals to Humans

Some heavy metals (like Zinc and Copper) have been reported to be of bio-importance to

man and their daily medicinal and dietary allowances. Their tolerance limits in drinking

and potable waters have also been reported, However, some others (like Cadmium and

Lead, ) have been reported to have no known bio-importance in human biochemistry and

physiology and consumption even at very low concentrations can be toxic (Holum, 1983;

Fosmire, 1990; McCluggage, 1991; Ferner, 2001; European Union, 2002; Nolan, 2003;

Young, 2005). Even for those that have bio-importance, dietary intakes have to be

maintained at regulatory limits, as excesses will result in poisoning or toxicity, which is

17

evident by certain reported medical symptoms that are clinically diagnosable (Fosmire,

1990; Nolan, 2003; Young, 2005). Zinc is a ‘masculine’ element that balances copper in

the body, and is essential for male reproductive activity (Nolan, 2003). It serves as a co-

factor for dehydrogenating enzymes and in carbonic anhydrase (Holum, 1983). Zinc

deficiency causes anaemia and retardation of growth and development (McCluggage,

1991). Calcium is a very vital element in human metabolism. It is the chief element in the

production of very strong bones and teeth in mammals. Its tolerance limit is high relative

to other bio-useful metals, that is, at 50 mg/l of drinking water .The daily dietary

requirement of calcium soars at the highest across both sexes and all ages of humans

accommodated at higher doses in the body because its concentration in the blood is well

regulated by thyrocalcitonin and parathormone hormones (Holum, 1983). Lead and

cadmium have been reported not to have any known function in human biochemistry or

physiology, and do not occur naturally in living organisms (Lenntech, 2004). Hence

dietary intakes of these metals, even at very low concentrations can be very harmful

because they bio accumulate.

2.4.1. Effect of bioaccumulation on humans

The bio toxic effects of heavy metals refer to the harmful effects of heavy metals to the

body when consumed above the bio-recommended limits. Although individual metals

exhibit specific signs of their toxicity, the following have been reported as general signs

associated with cadmium, lead, zinc, and copper poisoning: gastrointestinal disorders,

diarrhoea, stomatitis, tremor, hemoglobinuria causing a rust–red colour to stool, ataxia,

18

paralysis, vomiting and convulsion, depression, and pneumonia when volatile vapours

and fumes are inhaled (McCluggage, 1991). The nature of effects could be toxic (acute,

chronic or sub-chronic), neurotoxin, carcinogenic, mutagenic or teratogenic. Cadmium is

toxic at extremely low levels. In humans, long term exposure results in renal dysfunction,

characterized by tubular proteinuria. High exposure can lead to obstructive lung disease,

cadmium pneumonitis, resulting from inhaled dusts and fumes. It is characterized by

chest pain, cough with foamy and bloody sputum, and death of the lining of the lung

tissues because of excessive accumulation of watery fluids. Cadmium is also associated

with bone defects, viz; osteomalacia, osteoporosis and spontaneous fractures, increased

blood pressure and myocardic dysfunctions. Depending on the severity of exposure, the

symptoms of effects include nausea, vomiting, abdominal cramps, dyspnea and muscular

weakness. Severe exposure may result in pulmonary oedema and death. Pulmonary

effects (emphysema, bronchiolitis and alveolitis) and renal effects may occur following

subchronic inhalation exposure to cadmium and its compounds (McCluggage, 1991;

INECAR, 2000; European Union, 2002; Young, 2005).

Lead is the most significant toxin of the heavy metals, and the inorganic forms are

absorbed through ingestion by food and water, and inhalation (Ferner, 2001). A notably

serious effect of lead toxicity is its teratogenic effect. Lead poisoning also causes

inhibition of the synthesis of haemoglobin; dysfunctions in the kidneys, joints and

reproductive systems, cardiovascular system and acute and chronic damage to the central

nervous system (CNS) and peripheral nervous system (PNS), (Ogwuebgu and Muhanga,

2005). Other effects include damage to the gastrointestinal tract (GIT) and urinary tract

resulting in bloody urine, neurological disorder and can cause severe and permanent brain 19

damage. While inorganic forms of lead, typically affect the CNS, PNS, GIT and other bio

systems, organic forms predominantly affect the CNS (McCluggage, 1991; INECAR,

2000; Ferner, 2001; Lenntech, 2004). Lead affects children by leading to the poor

development of the grey matter of the brain, thereby resulting in poor intelligence

quotient (IQ) (Udedi, 2003). Its absorption in the body is enhanced by Ca and Zn

deficiencies. Acute and chronic effects of lead result in psychosis.

Zinc has been reported to cause the same signs of illness as does lead, and can easily be

mistakenly diagnosed as lead poisoning (McCluggage, 1991). Zinc is considered to be

relatively non-toxic, especially if taken orally. However, excess amount can cause system

dysfunctions that result in impairment of growth and reproduction (INECAR, 2000;

Nolan, 2003). The clinical signs of zinc toxicities have been reported as vomiting,

diarrhoea, bloody urine, icterus (yellow mucus membrane), liver failure, kidney failure

and anaemia (Fosmire, 1990).

2.5. Lagoon Pollution in Ghana

Presently, Ghana is dealing with the rate of urban periphery settlements which is as a

result of the massive migration of the rural inhabitants to the cities, especially to Accra.

Unfortunately persons in these settlements often lack essential social amenities,

especially those related to sanitation, resulting in heavy environmental pollution. The

contamination of lagoons with heavy metals is a major source of concern since it is a

habitat for fish and other aquatic organisms such as mussels, oysters, prawns and lobsters

which are major sources of protein for most people in Ghana. Heavy metals released into 20

the environment find their way into aquatic systems as a result of direct input,

atmospheric deposition and surface runoffs. Fish species can accumulate these heavy

metals in their tissues at concentrations greater than the ambient water and pose a health

threat to humans who consume them (Armah, 2007).

Natural waters therefore become the key environmental component that suffers massively

from such pollution and this is the current situation epitomized by the Korle lagoon in

Accra. Some years ago the Korle lagoon was of economic importance to the country of

which some were able to reach it outside borders. Some of which were salt, fish and

wood (Armah, 2007).

2.6. State of the Korle lagoon

The Korle lagoon, which is a major run-off water receptacle and a point source of

pollution into the Gulf of Guinea, has been negatively impacted by the uncontrolled

domestic and industrial pollution. Previous water quality surveys indicated that the Korle

lagoon is moderate to grossly polluted water body as evidenced by the physical, chemical

and bacteriological characteristics which can be traced to discharges of domestic and

industrial effluents from inland as well as to the operations of the sewage outfall in the

vicinity of the lagoon’s entrance (Karikari et al, 2007). Up to the 1950s, the Korle

Lagoon supported a thriving fishery, but presently it supports only a few fish species

which include Seriola dumerili and Pteroscion peli, are restricted to its estuary (Biney

and Amuzu, 1995).

21

The increasing pollution of Korle Lagoon is as a result of the rapid urbanization of Accra.

This has been unaccompanied by a significant increase in sanitation facilities. The

process has been assisted by rapid industrialization without regard for environmental

safety. Rapid population growth, enhanced by the facilities and job opportunities,

continues to draw people into Accra. This has resulted in considerable stress on the

already inadequate urban facilities including the housing and basic sanitation amenities.

This situation has led to the development of slums and shantytowns, and the consequent

degradation of the urban environment. With little equipment to manage the refuse,

garbage is collected only in high-income areas (Doe, 2000).

The remaining areas disposed of their garbage in public containers, in open spaces,

streams and drainage systems. The catchment area is surrounded by shantytowns,

including Korle Gonno, Korle Dudor, Adadinkpo and James Town, among many others.

Prominent among these slums is Sodom and Gomorra (Old Fadama), a growing squatter

settlement. The site exhibits poor housing conditions and consists mainly of wooden

shacks (Doe, 2000). There are no sanitation facilities, and people defecate directly into

the lagoon with all kinds of waste being disposed of into the water body.

2.6.1. Heavy metal sources to the lagoon

A major activity that massively contributes to the pollution of the lagoon is the local and

crude methods of recycling electronic waste (e-waste) to retrieve the metallic

components. Agbogbloshie, a suburb of Ghana’s capital, Accra, and just adjacent the

lagoon is a known destination for legal and illegal of electronic waste (e-waste) from

industrialized nations. Often referred to as a "digital dumping ground", millions of tons of

22

e-waste are processed each year in the local recycling workshops. At these workshops, e-

waste is recycled with virtually no regulations, and primarily involves manual

disassembly of the obsolete electronic products and open burning to isolate copper and

other valuable metals from plastics.

Other sources of heavy metals into the Lagoon can be traced to effluent discharged from

domestic and industrial activities. According to Boadi and Kuitunen (2002) and Agodzo

et al, (2003), approximately 60% of the domestic and industrial waste from Accra, the

capital of Ghana, with a population of approximately 4.0 million people, flows into the

Lagoon. Other major potential sources of heavy metal pollution in the Lagoon are the

numerous local metal smelting industries and the small garages and workshops located

within in the vicinity of the Lagoon. Another major source of pollution in the Lagoon is

the Odaw River, a major inlet of the Korle Lagoon. The Odaw River drains the high

density low income areas of Accra and has a large concentration of industries including

breweries, several textile factories and vehicle repair workshops in its catchment.

2.6.2. Effect of Korle lagoon pollution

Severe pollution of the lagoon has resulted in the reduction of aquatic invertebrates and

the complete disappearance of some species from the lagoon’s environs. The break in the

food chain has resulted in the near extinction of both resident and non-resident birds,

which feed and roost in the mangroves and mudflats along the lagoon. The pollution has

also resulted in a fowl stench, which in itself is a disincentive for tourism development.

23

Domestic and industrial pollutants have contributed to increased biochemical oxygen

demand and concentration of toxic chemicals in the water body (Biney and Amuzu,

1995).

2.6.3. Activities at the estuary

Presently however, beach seining and other fishing activities take place at the estuary of

the lagoon and within 500 m offshore and the harvested fish are usually sold to local food

vendors and also to satisfy domestic protein requirements. Although fish from the

estuary of the lagoon are believed to be unwholesome for human consumption, very little

research has been carried out to determine the levels of contaminants in the flesh of the

fish harvested from the Lagoon (Entsua-Mensah, 2004).

2.7. Fish Species

There is a definite pattern in the distribution of fish species on the continental shelf

(Longhurst, 1965). The available data indicate that the distribution of a number of species

is limited by the depth of the thermocline and is influenced by the type of bottom deposits

(sand and silts), and the depths on the continental shelf, the slope of which is variable.

There are discrete ecological fish communities, each of which is fairly homogeneous.

However, there is also ecological and micro geographical heterogeneity of fish

communities. Besides, migration of species from the estuaries and creeks to the open

shelf areas and vice versa is known to occur.

The following fish communities are exploited by the artisanal fishing units:

24

i. the estuarine and creek sciaenid sub-community,

ii. the offshore suprathermoclinal sciaenid sub-community (on soft deposits),

iii. the sparid sub-community (on sandy) (FAO, 1981).

2.7.1. Seriola spp

The genus Seriola is of the family Carangidae, order Perciformes, and class

Actinopterygii. Three species of the genus Seriola are caught at the estuary of the Korle

lagoon with the dominant species being Seriola dumerili.

The greater amberjack, S. dumerili, is a cosmopolitan species, found in warm waters all

over the world. Its main morphological characteristics are the elongated, fusiform and

slightly laterally compressed body, covered with small scales (cycloids). Their color is

yellow-green in juveniles; in adults it is blue or olivaceous dorsally and silvery to white

on the sides and belly. S. dumerili is a multiple spawning fish, and it may release several

batches of eggs during the same spawning season. The ovary type in this group is

synchronous: at least two size groups of oocytes are present at the same time (Grau

1992). This species is gonochoric without sexual dimorphism, and both sexes are

separated. According to Micale et al. (1993), maturity occurs at three years of age but

functional breeders are 4 and 5 years old for males and females respectively. Marino et

al. (1995) reported the first reproductive season for this species to be at 4 years of age for

both sexes, even though 40% of males are sexually mature at 3 years of age.

25

Japanese amberjack (S. quinqueradiata) are present in the Western Central Pacific

Ocean from Japan and the eastern Korean Peninsula to the Hawaiian Islands. This species

reaches a maximum size of 150 cm TL (male/unsexed) and a maximum weight of 40 kg.

It shows asynchronous oocyte development.

Yellowtail amberjack (Seriola lalandi) are present in Atlantic, Pacific and Western Indian

Oceans. It is considered a circumglobal species, supporting commercial and recreational

fisheries worldwide. This species is a spring-summer spawner, with a multiple group

synchronous oocyte development and, like the greater amberjack (S. dumerili), has the

capacity for multiple spawning within a reproductive season. The smallest size at which

females caught in New Zealand matured was 775 mm FL; 50% reached sexual maturity

at 944 mm, while all were mature at 1 275 mm. McGregor (1995) reported maturity at

580-670 mm. In Australia, according to Gillanders, et al (1999), mature females of this

species appeared at 698 mm (3 years) reaching 50% at 834 mm (4-5 years). The

differences in size between these 2 populations could be attributed to different rearing

conditions.

2.7.2. Pteroscion peli

Belongs to the Class Actinopterygii (ray-finned fishes) order perciformes (Perch-likes) >

family sciaenidae (Drums or croakers). Pteroscion peli occurs only along the West coast

of Africa, from Senegal to Angola, where it is found in mid waters as well as on mud,

sandy mud bottoms in coastal waters and also occurs seasonally in brackish water areas.

Its depth distribution extends from the shoreline to 200 m but the species prefers waters 26

of less than 50 m and is one of the most abundant sciaenids in shallower waters and feeds

on fish, cephalopods, shrimps and annelids (FAO 1986).

27

CHAPTER THREE

3.0. METHODOLOGY

3.1. Description of the study area

The Korle lagoon is a coastal wetland that joins the Gulf of Guinea at a point near Korle

Gonno; a suburb of Accra (Grant, 2006). It serves as the major floodwater conduit for the

Accra Metropolitan Assembly (Fig 3.1), the lagoon is estimated to drain a total catchment

area of 400 km2 (Karikari et al, 1998). The major hydrological input includes the Odaw

River, two huge drains that border the lagoon, and rainfall including runoff. A mixture of

land uses characterizes the areas adjacent to the lagoon (Boadi and Kuitunen, 2002).

Fig 3.1 Korle lagoon and its environs (IMDC, 2011)

28

3.2. Sample collection

Fish samples were obtained from fishers (Plate 3, 4) at the estuary of the Lagoon and

transported on ice in an insulated chest (Plate 1, 2).

Plate 1 Pteroscion peli from the Korle lagoon Estuary

Plate 2 Seriola dumerili from the Korle lagoon Estuary

A total of 8 samples (Plate 5, 6) were obtained monthly for each species over the four

months period. Samples from each species were categorized into two classes based on the

sizes obtained for each; Pteroscion peli (Small ≤14cm and large ≥ 15cm) and Seriola

dumerili (Small ≤24cm and large ≥25 cm) and were stored in a deep freezer prior to the

heavy metal analysis.29

Plate 3 Beach Seining at the Korle lagoon estuary Plate 4 Obtaining samples from fishers

Plate 5 Some Pteroscion peli obtained Plate 6 Some Seriola dumerili obtained

Three sediment sampling sites were selected from site A, site B and site C as shown in

The sediment sample was taken from each site and was divided into three to ensure

accuracy in the result for each site sampled. This was done for the four months study

period; October 2011 to January 2012. The Ekman grab was used in collecting the

sediments samples. At site B and C the Ekman grab was mounted in a boat, after 30

releasing the instrument to the bottom the boat owner dived to trip the over lapping

spring loaded with scoop, the depth of both portion could be between 1 to 4 meters whilst

at point C samples were taken by walking into the water to points where the water

reached the knee and with the Ekman grab sediments were collected. Samples were

stored in plastic bottles and packaged in plastic bags and were kept in a cool, dry and

ventilated room prior to heavy metal analysis.

Sampling point (A) is the area that receives frequent sea water at both low tides and high

tides with no rock deposited on both side (Plate 7).

Plate 7 Sampling point (A)

Sampling point (B) is the area affected by the influx of both fresh water and sea water

and rocks are deposited on the right side of the curved channel (Plate 8).

31

Plate 8 Sampling point (B)

Sampling point (C) is the area that receives fresh water frequently than sea water and also

joins B in a slightly curved channel with rocks deposited on both sides (Plate 9).

Plate 9 Sampling point (C)

3.3. Heavy Metal Analysis

In order to free bonded heavy metals in the flesh of Pteroscion peli, Seriola dumerili and

sediments, wet di-acid digestion was done. All procedures for the analyses were based on

the Association of Analytical Chemist (AOAC 2003) protocol.

32

3.3.1. Sample Digestion

Fish and sediments samples acquired were digested at the same time. Sample digestion is

the removal of organic materials and the conversion of metals present into soluble forms.

3.3.2 Fish digestion

The total length (Plate 10) and body weight of the fish samples after defrosting were

measured with a centimetre rule and weighed with an electric scale (Sartorius model, BP

6100) and labelled after identification. Small part (5grams) of the flesh from its side were

removed and chopped with the aid of stainless steel dissection instruments, while wearing

surgical gloves. After, flesh samples were then digested with a di- acid mixture, (nitric

acid, and perchloric acid in a ratio of 9: 4).

Plate 10 Total length of Seriola dumerili being taken

One gram of the chopped flesh samples was separately taken and placed in a 100ml

volumetric flask. Ten millilitres of di acid mixture was added. The content was mixed by

swirling in the volumetric flask. The flask was then placed on a hotplate in a fume hood

and heated starting at 90oC and raised to 200oC. Heating continued until the production of

a red NO2 fume ceases. The contents were further heated until the volume was reduced to

33

3-4ml and became colourless without being dry. It was made to cool to room

temperature. The volume was made up with distilled water and filtered with a Whatmann

filter paper. The filtrate was then diluted to 50ml mark in a volumetric flask with double

distilled water. It was then poured into small containers. The containers containing the

digested samples were kept at 4˚c in a refrigerator prior to heavy metal analysis (Plate

12).

3.3.2. Sediment digestion

Sediment samples were labelled (according to their location) on the field and air dried at

room temperature. Sediments were dried on a plastic sheet (Plate 11).

Plate 11 Sediments being air dried at room temperature

The dried materials were grounded to pass through a 63µm sieve and stored in plastic

bottles. Digestion was done for the sediments as it was done for the fish flesh samples

above at the Faculty of Renewable Natural Resources.

34

Plate 12 Some containers containing digested samples

3.3.3. Determination of heavy metal concentration

Heavy metal analysis was done at the Anglo Gold Ashanti Laboratory. The

concentrations of copper, cadmium, lead, and zinc, were determined with the aid of flame

Atomic Absorption Spectroscopy, (AAS) (SpectrAA 220 model).

A blank solution of the di-acid and distilled water used which contained no analyte

element was made and after, a series of calibrated solutions of the di acid and distilled

water containing known amounts of analyte element (the standards) were also made. The

blank and standards were atomized in turn, with their respective responds measured.

Graph of both responses were plotted. The digested samples were then atomized and their

response measured. The concentrations of heavy metal in the sample were known by the

calibration and the absorbance obtained for the unknown.

35

All samples were accompanied by blanks at a rate of one blank per 20 samples. Replicate

analyses were conducted for all the samples to evaluate the precision of the analytical

technique. The results were expressed as total concentration (μg/g wet weight (ww).

3.3.4. Measurement of Physicochemical Water Parameters

Monthly measurement of temperature, salinity, pH, total dissolved solids (TDS),

conductivity and dissolved oxygen (DO) of the Korle Lagoon were taken between the

hours of 7am-10am, using a multi-parameter probe at the 3 sampling site over the four

months period -(YSI 550A model)(Plate 13).

Plate 13 Water Quality parameter been taken insitu

36

CHAPTER FOUR

4.0. RESULTS

4.1. Heavy metal concentrations in Sediment Samples

Copper concentration s were consistently fluctuating over the period and ranged between

4.38 μg/g ww to 5.90 μg/g ww from November 2011 to January 2012. A mean

concentration of 5.12 μg/g ww was recorded for the estuary over the four month period.

Lead concentration increased drastically from a mean value of 2.80 μg/g ww in October

to 39.20 μg/g ww in December 2011. A decrease in the concentration of lead was

recorded for January 2012.

Zinc ranged from 9.46 μg/g ww to 14.66 μg/g ww but this decrease was inconsistent as

concentration declined from 12.44 μg/g ww in November 2011 to 9.46 μg/g ww in

December 2011.

Cadmium concentration fluctuated over the period with highest concentration of 2.50

μg/g ww recorded in December 2011.Heavy metal levels in sediment over the period

ranked in the following order: Pb > Zn >Cu >Cd.

The monthly heavy metal concentrations of the four metals in the sediments of the Korle

lagoon estuary are shown in Table 4.1.

37

Table 4.1. Copper (Cu), Lead (Pb), Zinc (Zn) and Cadmium (Cd) concentration (μg/g ww) in the sediment from the Korle lagoon Estuary.

Month n Cu Pb Zn Cd

October 9 4.41±0.15 2.80±0.96 12.21±4.28 2.33±0.25

November 9 4.38±0.39 2.86±1.49 12.44±3.62 2.26±0.30

December 9 5.80±0.02 39.20±0.46 9.46±0.88 2.50±0.10

January 9 5.90±0.08 38.36±1.69 14.66±0.05 2.23±1.00

Mean 5.12±0.16 20.80±1.15 12.19±2.20 2.33±0.41

NOAA (1995)

ERL 34.00 46.70 150.00 1.20 ERM 270.00 218.00 410.00 9.60National Oceanic and Atmospheric Administration (NOAA), Effect Range low (ERL), Effect Range Medium (ERM) Values are mean± SD, n= number of samples.

4.2. Heavy metal concentrations in Pteroscion peli

Mean concentration of copper in Pteroscion peli over the sampled period was 5.11 μg/g

ww. Copper (Cu) levels increased between 2.83 μg/g ww in November 2011 to 7.65 μg/g

ww January 2012. In October 2011 concentration declined from 3.02 μg/g ww to 2.02

μg/g ww in November 2011. A mean lead (Pb) concentration of 2.73 μg/g ww was

recorded over the study period. An increase and decrease in concentration alternated over

the sampling period. Cadmium (Cd) concentration consistently increased from 1.48 μg/g

ww to 2.91 μg/g ww over the study period. Zinc (Zn) concentration increased from

November 2011 to January 2011 with values ranging between 13.58 μg/g ww to 23.11

38

μg/g ww for both months respectively. Between October 2011 and November 2011

concentration dropped from 14.09 μg/g ww to 13.58 μg/g ww. A mean concentration of

16.41 μg/g ww was recorded over the study period. Mean ± standard deviation of Cu, Pb,

Zn and Cd concentrations (μg/g ww) in the flesh of Pteroscion peli from the Korle

lagoon estuary from October 2011 to January 2012 is presented in Table 4.2.

Table 4.2. Heavy metal concentrations (μg/g ww) in the flesh of Pteroscion peli from

the Korle lagoon estuary

Month n Cu Pb Cd Zn

October 8 3.02 ± 1.20 2.62±1.1.83 1.48± 0.25 14.09±2.80

November 8 2.83 ± 0.42 2.87 ±1.80 1.51±0.29 13.58±1.97

December 8 6.92±0.91 2.51±0.45 2.81±0.22 14.86±4.27

January 8 7.65±0.93 2.95±0.34 2.91±0.15 23.11±6.99

Mean 5.11±0.86 2.73±1.10 2.17±0.22 16.41±4.00

WHO (1983) 10 2.0 2.0 1000

WHO (2005) - 0.5 0.5 1000

World Health Organization (WHO)Values are mean± SD, n= number of samples

39

4.3. Heavy metal concentration in Seriola dumerili

Concentration trend observed in Seriola dumerili varied to that of Pteroscion peli.

Copper (Cu) concentration increased from November 2011 to January 2012 from 3.36

μg/g ww to 6.14 μg/g ww. A mean concentration of 4.43 μg/g ww was recorded over the

period.

Lead (Pb) concentrations over the period fluctuated between 2.07 μg/g ww in December

2011 to 3.01 μg/g ww in November 2011. A decrease in concentration was observed

from October 2011 to November 2011 and that of November 2011 to December 2011.A

mean concentration of 2.54 μg/g ww was recorded over the period.

Cadmium (Cd) level of 1.75 μg/g ww was recorded as the mean concentration over the

sampling period. Cadmium levels in Seriola dumerili were inconsistent over the study

period between 1.35 μg/g ww to 2.95 μg/g ww.

Zinc (Zn) concentrations increased from November 2011 to January 2012 with its level

increasing from 13.43 μg/g ww to 14.98 μg/g ww respectively. A mean concentration of

13.90 μg/g ww was recorded over the study period. Cu, Pb, Zn and Cd concentrations

(μg/g ww) in the flesh of Seriola dumerili from the Korle lagoon estuary is presented in

Table 4.3.

40

Table 4.3. Heavy metal concentrations (μg/g ww) in the flesh of Seriola dumerili from the Korle lagoon estuary

Month n Cu Pb Cd Zn

October 8 3.38 ± 0.76 2.90 ± 2.0 1.42 ± 0.31 13.45 ± 6.26

November 8 3.36 ± 0.32 3.01 ± 2.07 1.35 ± 0.29 13.43 ± 6.34

December 8 4.85±2.32 2.07±0.30 2.31±1.20 13.76±6.04

January 8 6.14±1.52 2.20±0.59 2.95±0.43 14.98±4.66

Mean 4.43 ± 0.87 2.54 ± 0.92 2.03 ± 0.43 13.90 ± 0.78

WHO (1983) 10 2.0 2.0 1000

WHO (2005) - 0.5 0.5 1000

World Health Organization (WHO)Values are mean± SD, n=number of samples

4.4. Heavy metals in the flesh of P. peli and the S. dumerili in relation to sizes

In order to examine variations in heavy metal concentration in the flesh of the two fish

species in relation to size, a plot of total accumulation versus size were carried out for the

two fish species (Fig 4.1 and 4.2).

41

4.4.1. Pteroscion peli

Heavy metal concentration in relation to size of Pteroscion peli increased with increase in

size for October 2011 and December 2011, even though for November 2011, zinc

concentration in Small Pteroscion was higher than that of large size.

In January 2012, copper and zinc concentrations increased in small Pteroscion peli than

in large size Pteroscion peli. Lead concentration in December 2011 was relatively higher

in the small fishes than in large samples (Fig 4.1 below).

Fig 4.1 Variations in Cu, Pb, Cd and Zn concentrations in the flesh of Pteroscion peli in

relation to body size (Small ≤14cm , Large ≥ 15cm)

42

4.4.2. Seriola dumerili

Heavy metal concentration in October 2012 and November 2012 increased with increase

in size as large size Seriola dumerili recorded higher levels than smaller Seriola dumerili.

On the other hand, small fish size fishes had higher concentration of copper and zinc for

December 2011 and January 2012. Lead concentrations in December 2011 were high in

large Seriola dumerili than in small once.

Fig 4.2.Variations in Cu, Pb, Cd and Zn concentrations in the flesh of Seriola dumerili in

relation to body size (Small ≤24cm, large ≥25 cm)

43

4.5. Physicochemical Parameters of the Korle lagoon

Physicochemical parameters for the four months (October 2011 to January 2012)

sampling period was relatively uniform as shown in Table 4.4.

Temperature conditions in the lagoon ranged from 26.60°C to 29.10 °C over the period, a

consistent increase in temperature from November 2011 to January 2012 was recorded

Dissolve oxygen levels in the estuary was fairly constant over the sampling period even

though some portions of the estuary recorded very low oxygen levels. pH level over the

sampling period was relatively neutral. A high conductivity of 3901 mg/l was recorded in

January 2012. Salinity levels were low over the sampling months and were relatively

similar for the sampling months. A Total Dissolve Solid value of 1991 μs/cm was

recorded in December and was the highest over the study period.

Table 4.4. The physicochemical parameters of the Korle Lagoon from October, 2011 – January, 2012

Parameter n October November December January

Temperature (°C) 3 26.81±0.59 26.60±0.80 29.10±1.10 28.50±0.10

DO (mg/l) 3 6.10±1.10 6.00±0.41 5.98±0.04 6.00±1.30

TDS ( μs/cm) 3 1748±397.93 1553±495.62 1991±0.05 1901±1.42

Salinity (ppm) 3 15.05± 0.41 14.77± 1.80 16.01± 0.01 15.98± 1.03

Conductivity (mg/l) 3 3588±553.65 3381±158.04 3008±0.01 3901±1.07

pH 3 7.30±0.30 7.16±0.24 7.07±0.86 7.18±1.05

44

Total Dissolve Solids (TDS), Dissolved Oxygen (DO), Values are mean± SD, n=number of data recorded

CHAPTER FIVE

5.0. DISCUSSION

5.1. Heavy Metal Concentration in Sediments

Heavy metals in sediments may represent a combinational effect of chemical, biological

and physical processes occurring in the fluvial, estuarine, and coastal environments.

Fluctuations in the concentrations of heavy metals in the sediment of the Korle lagoon

estuary might be due to the ability of surface sediments to integrate these changes that

occur in the water column and act both as a repository and source of suspended materials.

Spatial variations of heavy metals in the surface sediments are the results of these

processes (Lin, et al 2003). Moreover, heavy metals generally exist in the particulate

phase adsorbed on the sediments. This behaviour of heavy metals in the estuary sediment

may be strongly influenced by adsorption to organic particles (sewage deposited at the

Korle lagoon estuary) and the inorganic particles in the lagoon (Table 4.4).

The particulate fraction may be transported with the sediments, which are governed by

sediment dynamics. Re-suspension of contaminated bed sediments may be caused by

strong tidal currents which may release a significant amount of heavy metals into the

water column (Zagar, 2006).

In addition, the relatively high levels of cadmium in the sediments compared to the Effect

Range Low (ERL) could be due to the high concentrations of dissolved salts or organic

45

matter which reduces its accumulation in sediments. Lead readily accumulates in

sediments and this could be the reason for the high levels recorded over the period.

Sediments are also thought to be the most important depositional site for particulate

copper transported from rivers; although remobilization may occur when sediments are

disturbed. The low copper levels recorded could be due to the regular mixing of the water

column due to its fluvial flow rate. Moreover, during high turbidity, greater levels of zinc

associated with suspended sediments are deposited with flocculated particles where it can

and where it can particularly accumulate in anaerobic sediments (Hunt et al, 1992).

Furthermore, fluctuation of heavy metals in the sediment could be due to the water

chemistry of the Korle lagoon estuary which may controls the rate of adsorption and

desorption of metals to and from sediments. The adsorption process could remove metals

from the water column and store these metals in the substrate. Desorption on the other

hand may return the heavy metals from sediment to the water column where recirculation

and bio assimilation could take place.

High salt concentrations could create increase competition between cations and metals

for binding site. This may cause metals to be driven off from sediments into the overlying

water, and this may often occur at estuary due to river flow inputs and tides.

Decreased redox potential under hypoxic conditions could change the composition of

metal complexes as metals bind to oxygen to form oxides and this could release the

heavy metal ions into the overlying water at the estuary.

pH may increase competition between metals and hydrogen ions for binding site. A lower

pH could also dissolve metal carbonate complexes releasing free ions into the water

46

column (Connell et al, 1984) as a result of the deposition of Sewage into the Korle

lagoon estuary.

According to Long et al. (1995), the concentration of copper, lead and Zinc recorded

occurs below the Effect Range Low value therefore their effects on fishes at the estuary

would rarely be observed. Cadmium concentration recorded was equal to the ERL but

below the ERM, which implies that fishes at the estuary could occasionally be affected

by Cadmium.

5.2. Heavy Metal effect in fish species

The mean concentration of Copper and Zinc in Pteroscion peli and Seriola dumerili were

lower as compared to the World Health Organization standards (2005). Cadmium and

Lead concentration were higher than the standard used. The lower levels of copper in the

flesh of both fishes could be due to the role of copper as an ingredient, normally in the

prosthetic group, of oxidizing enzymes which are important in oxidation-reduction

processes in fishes (Moolenaar, 1998). Also, copper in the cupric form may be the most

bio available (Grimwood, 1997) and could be readily accumulated by the fishes. It may

also be regulated or immobilized in many species and might not be biomagnified in the

food chain to any significant extent (CCREM, 1987).

Low level of Zinc recorded could be due to the up take of zinc readily by the study fish

species which may not reflect in the flesh tissue (Hunt et al, 1992). High level of lead

concentration could be due to the uptake and accumulation of lead by fish from water and

sediment and this may be influenced by various environmental factors. Consumers such

as (Pteroscion peli and Seriola dumerili) may take up lead from their contaminated food, 47

often to high concentrations, but without bio magnifications (WHO, 1995). Lead uptake

by fish could reach equilibrium only after a number of weeks of exposure. Typical

symptoms of lead toxicity include spinal deformity and blackening of the caudal region

as observed in the obtained fish samples. Tetra alkyl lead which is an inorganic lead

compounds may rapidly be taken up by fish and rapidly eliminated after the end of the

exposure (WHO, 1995).

Cadmium bio accumulates in organisms with the main uptake routes being dissolved

cadmium from the water column and cadmium associated with prey items. This could be

the reason for the high levels in Seriola dumerili and Pteroscion peli (WHO, 1992).

5.3. Variation in Metal Concentrations in Relation to Body Size

Large fishes for both species had a higher metal concentration in Pteroscion peli and

Seriola dumerili, but thoroughly there were no variations in metal concentrations between

the two size classes for both fish species and may be due to similarities in bioavailability

of the heavy metals to the two fish species (Pteroscion peli and the Seriola dumerili.)

from the Korle lagoon estuary, since both fish species are piscivorous (Ferreira et al.,

2004).

Smaller fishes might have accumulated high concentrations of heavy metals and this

might be due to their size, their feeding pattern and availability of the heavy metals

(FAO, 2012).

48

CHAPTER SIX

6.0. CONCLUSIONS

Heavy metal levels in fishes sampled were less than what was found in the sediment

samples. Heavy metals in sediment were continuously adsorbed and desorbed from

sediments into the overlying water column. The sediment quality in terms of the heavy

metals was acceptable but could pose a serious risk to the aquatic life of the lagoon

estuary in future if nothing is done to check metal accumulation in the Korle lagoon

estuary sediment.

The four metal concentrations in the flesh of the two fish species were lower for Zinc and

Copper but saw a high concentration for Cadmium and Lead as compared to the World

Health Organization Standard (2005) hence not safe for human consumption.

From the study however, it was also depicted that Pteroscion peli and Seriola dumerili

accumulate heavy metals in their flesh regardless of size.

6.1. RECOMMENDATIONS

The heavy metal concentrations in estuary have to be monitored on a more regular basis

for the effects of pollution on other fish communities. Although fish flesh (muscle) is the

most important part to be used for human consumption, fish skin and liver may also be

consumed to some extent. Target organs such as liver, kidney, gonads and gills, have a

49

tendency to accumulate heavy metals in high values and therefore a study has to be

conducted to assess the concentration of heavy metals in them.

Moreover, Secondary feeders like filter feeders (Mugil cephalus) and other herbivores

fishes from the Korle lagoon estuary could be studied to know their bio accumulation

levels and their magnification in the food chain.

Accumulation of heavy metals in fish flesh may be considered as an important warning

signal for fish health and human consumption. The present study shows that consumption

of fish from the Korle Lagoon estuary should be prohibited and should be discouraged

because of the high levels of Pb and Cd in the flesh of Seriola dumerili and Pteroscion

peli in both small and large sizes.

50

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