Pollution in Coastal and Shelf Pollution in Coastal and Shelf Seas:Seas:

An OverviewHuge topic; 766,000 hits on Google!

What is pollution (UN version)?

“Marine pollution is the introduction by humans into the marine environment, directly or indirectly, of substances or energy that can lead to deleterious effects on e.g. biological systems, human health, fisheries, or reduce the quality of the environment for use by the leisure industry”

An overview of key points, Some of more important topics in more detail (* ) Case study of Black Sea.

Types of pollutants- major categories

Heat (power stations; impact on species composition & > bacterial respiration)

Sewage discharges (high organic carbon, plus other materials)

Nutrients* (at high levels)Metals*Hydrocarbons/oil*Chlorinated compounds, and other synthetic organics (endocrine disrupters, herbicides, unknown organics etc.)•Plastics/garbageRadio-nuclides (power/reprocessing plants- Cs-137, Sb-125, Chernobyl Cs-134)

Some pollutants may be naturally presentHowever, Human activity often has enhanced

releases, e.g.

Metals released from mine spoil Eutrophication may enhance occurrence of toxin release from HABs, (Harmful Algal Blooms)Natural oil seeps

Origins of pollutants:

Domestic effluents

Industrial effluents [direct (outfalls) and indirect (e.g. via atmosphere)]

Ship origin (sinking tankers, washing tanks, anti-fouling agents etc)

Impact of pollutantsFunction of toxicitySub-lethal effects- pressure on species Bio-accumulation through food web

Control of Marine Pollution requires knowledge of:

Pathways by which pollutants reach the coastal and shelf seasRates of inputs and dispersal of pollutantsForms in which pollutants occur and how they behave in marine systems

It is clear that knowledge of relevant marine physics, biology, chemistry and geology/sedimentology are all needed to provide an interdisciplinary view of pollutioninterdisciplinary view of pollution.

NoteNote that as the coastal and Shelf seas systems that as the coastal and Shelf seas systems are open to inputs from land and atmospheric are open to inputs from land and atmospheric

source, controlling pollution here is synonymous source, controlling pollution here is synonymous with controlling with controlling Global PollutionGlobal Pollution!!

From Simpson, 1994

Recent estimates of impact of human activities on P fluxes = 2.4 X pre-human

Nutrients in coastal waters

Referring to N, P and Si, as essential nutrients for phytoplankton growth

Major input through rivers, although atmosphere can be important for N (ammonia, nitrate)

Human impact principally through use of fertilisers and detergents

Nitrate in the southern North Sea 1989, µM

Phytoplankton, organic carbon inputs, bacteria and oxygen demand

(highly simplified!)

algae

bacteria

N PCO2

oxygen

Oxidation provides energy

respiration

Dead organic matter

supplies

produces Human

s

Low or no oxygen:EutrophicEutrophic conditions

Sewage/C inputs

Increase in biomass, on dying high bacterial respiration and oxygen reduction = EutrophicationImpact in terms of fish mortality, red-tide incidence etc.

Particularly important when no or limited mixing with oxygenated watersMajor impact in restricted exchange environments (e.g. Baltic Sea)

Can be large-scale impact – e.g. Gulf of MexicoControls include reduced use of fertilisers, ban on P based detergents

Oxygen minimum zone (shaded) that develops annually in response to nutrient and other inputs to the Gulf of Mexico

•Example of metals released from mining in Spain

Metals as Pollutants in the coastal

zone

•Mining since Roman times, of Iberian pyrite belt in Andalucia

•Build up of mine tailings- residue after most metals removed from sulphide ores, but still high metal content•Sulphides oxidised in air- products sulphate and acid!

•Very low pH waters

•Tailing dams typically contain acid (pH2) waters and sulphide sludge

•Background source of Zn and other heavy metals to S Spanish coastal waters

•Zn signal can be followed for very long distances and into Mediterranean Sea

•Los Frailes mine spill, April 1998, released circa 6 x 106 m3 sludge and water released into Guadiamar river

•Concern over damaging Doñana Park (UNESCO world biosphere reserve)

•1.5 m thick layer of sludge covered 4000-5000 Ha of flood plain but was diverted from park

Image showing grey layer of metal laden sludge deposited on the flood plain of the Guadiamar.

(c/o Dr E. Achterberg)

Strait of Gibraltar

Main rivers draining mining areas

Manganese

Copper

Oil pollution

•Crude oil formed from organic remains of dead organisms over geologic time-scales.

Thousands of organic compounds may be present

50-98% of compounds hydrocarbons (C and H only)

Class ofhydrocarbon

Toxic? Biodegradable?

Alkane (chains) Relatively non-toxic Many organisms canbiodegrade

Cycloalkanes (30-60% of petroleum)

Toxic Very resistant tobio-degradation

Aromatic (2-4% ofpetroleum)

Generally highlytoxic

Few microbes candegrade thesecompounds

Oil introduced into marine environment through variety of routes:

Major incidents- sinking tankers- most Washing out tanks at sea (now banned)Land based inputs

Fate of Crude oil spilt on seawater:

Fate and behaviour of spilt crude oil will depend on composition (origin)

As oil is hydrophobic and < dense that water, will form thin layer at interface with atmosphere

100-200L of oil will cover 1 km2 to about 0.1 µm- thicker if major spill

Film moves with wind and tides

Evaporation- Generally the lower the molecular weight, the more volatile the

compound. Evaporation greatest in first few hours after a spill, but can

continue for months as compounds evaporate in MW sequence Evaporation function of T, wind action (directly related) For large spills most important factor for oil disappearance

Dissolution- The lighter fractions dissolve most easily Micro droplets may also form Dissolved/micro droplets more readily destroyed by UV

Emulsification- With adequate agitation, water absorbed by oil“chocolate mousse”

Microbial Biodegradation- Major ultimate process by which oil destroyed Oil degrading bacteria typically small in number; takes time for

numbers to build up Degradation function of T, nutrient availability etc.Fate of residual oil at sea- Formation of ubiquitous “tar balls”- gradual

physical/photochemical/ microbial degradation Oil may be entrained with denser particles and sink

Beaching- Most dramatic evidence of spills Once in sediments, slow degradation

Oil pollution impacts Larger organisms major impact on e.g. birds Benthic and inter-tidal organisms- variable

response depending on species, level ofcontamination etc.

Strategies to deal with Oil Spills If remains offshore, shore line impact limited Containment for use particularly near shore, ports etc Dispersants have been used to aid break-up and degradation-

however some dispersants may be more toxic than oil!!

Ultimately leave to natural processes to remove with time, the oilresidues

Examples of legislation to reduce pollution:

Tri- butyl Tin (TBT)

•Major impact on certain molluscs

•Impact on oyster growth (deformed shells; reduced growth)

•Now banned, even on larger vessels

Banning of “over the side” dumping of garbage at sea (1988)