CH 4, CH 7, CH 16

Continental Shelf / Neritic Zone Unit

Nature of Water

Physical properties of water excellent solvent high boiling point and freezing point denser in its liquid form than in its solid form supports marine organisms through buoyancy provides a medium for chemical reactions necessary

for life (photosynthesis).

Nature of Water

Structure of a water molecule 2 H (hydrogen) atoms covalently bonded to 1 O

(oxygen) atom polar—different parts of the molecule have different

electrical charges (H as positive charge and the O has a negative charge).

Nature of Water

Freezing point and boiling point hydrogen bonds—weak attractive forces between

slightly positive H atoms of one molecule and slightly negative O ends of nearby molecules

responsible for high freezing/boiling points. Doesn’t take very cold temps to turn into a solid, hence the high freezing point. Takes a lot of energy (high heat) to break the hydrogen bond, hence the high boiling point.

Nature of Water

Water as a solvent polar nature keeps solute’s ions in solution

Allows salt molecules (NaCl) dissolve in water water cannot dissolve non-polar molecules

Oil has non-polar molecules, which is why oil and water do not mix.

Nature of Water

Cohesion, adhesion, and capillary action Cohesion – water sticking to water

Due to hydrogen bonds Allows for surface tension

adhesion—attraction of water to surfaces of objects that carry electrical charges, which allows it to make things wet

capillary action—the ability of water to rise in narrow spaces, owing to adhesion

Nature of Water

Specific heat water has a high specific heat (amount of heat energy

needed to raise 1 g 1o C) Takes a lot of heat to raise water temp by 1 degree. This

why it takes a while for the oceans to heat up in warmer months.

Water and light different wavelengths (colors) of light penetrate to

different depths Reds/oranges/yellows do not go as deep as blues and

greens

Nature of Water

Chemical properties of water pH scale measures acidity/alkalinity pH scale goes from 0-14. Anything below 7 is acidic

and anything above 7 is alkaline or basic. ocean’s pH is slightly alkaline or basic (average 8)

owing to bicarbonate and carbonate ions organisms’ internal and external pH affect life

processes such as metabolism and growth

Salt Water

Composition of seawater 6 ions make up 99% of dissolved salts in the ocean:

sodium (Na+) magnesium (Mg2+) calcium (Ca2+) potassium (K+) chloride (Cl-) sulfate (SO4

2-) trace elements—present in concentrations of less than

1 part per million

Salt WaterSalinity: measurement of salt ions in

water seawater = 3.5% salt, 96.5% water expressed as in g per kg water or parts per

thousand Average ocean salinity is 35 ppt or 35 g/kg (not 3.5%)

Salinity can only change when freshwater is added or removed, not the addition or removal of salt.

Salt Water

salinity can change as a result of evaporation, precipitation, freezing, thawing, and freshwater runoff from land

10o N-10o S = low salinity (heavy rainfall) The more freshwater added the lower the salinity

areas around 30o N and 30o S = high salinity (evaporation) The more freshwater removed the higher the salinity

from 50o = low salinity (heavy rainfall) The more freshwater added the lower the salinity

poles = high salinity (freezing) The more freshwater removed the higher the salinity

Salt Water

Cycling of sea salts sea salt originally from earth’s crust ocean composition has remained the same owing to

balance between addition through runoff and removal. Salts are added at the same rate they are removed.

salts removed in many ways: sinking or depositing on land by sea spray evaporites concentration in tissues of organisms harvested for

food adsorption—process of ions sticking to surface of fine

particles, which sink into sediments

Salt Water

Gases in seawater gases from biological processes

oxygen is a by-product of photosynthesis most organisms use O, release CO2 just below sunlit surface waters is the oxygen-minimum

zone

Ocean Heating and Cooling

Earth’s energy budget energy input

sun’s radiant energy heats earth’s surface spherical shape + presence of the atmosphere cause the

amount of radiant energy reaching earth’s surface to decrease with increasing latitude. The farther away from the equator the colder it is.

Ocean Heating and Cooling

Earth’s energy budget energy output

excess energy absorbed by the earth is transferred to the atmosphere by evaporation and radiation

accumulation of greenhouse gases can prevent heat energy from radiating back to space Greenhouse effect is natural and very important to

survival of most organisms. Too many greenhouse gases (H2O, CO2, CH3, ect) can

cause too much heat to get trapped leading to global warming.

Ocean Heating and Cooling

Sea temperature temperature varies daily and seasonally affected by energy absorption at the surface, loss by

evaporation, transfer by currents, warming/cooling of atmosphere, heat loss through radiation

seasonal variations in the amount of solar radiation reaching the earth, especially between 40o and 60o N and S

Winds and Currents

Winds result of horizontal air movements caused by

temperature, density, etc. Air moves up into the atmosphere when it warms b/c it

becomes less dense. Air moves down back towards the earth when it cools b/c it is more dense. This is the cause of winds.

Winds and Currents

Winds Coriolis effect

Occurs due to Earths rotation on axis. path of air mass (winds) appears to curve relative to the

earth’s surface—to the right in the Northern Hemisphere, left in the Southern

Winds and Currents

surface wind patterns 3 convection cells in each hemisphere winds are designated by the direction from which they

are coming northeast trade winds southeast trade winds westerlies polar easterlies

Winds and Currents

Ocean currents surface currents

driven mainly by trade winds (easterlies and westerlies) in each hemisphere

Coriolis effect currents deflected to the right of the prevailing wind

direction in the Northern Hemisphere, to the left in the Southern Hemisphere

gyres—water flow in a circular pattern around the edge of an ocean basin

Ocean Layers and Ocean Mixing

Density—the mass of a substance in a given volume, usually in g/cm3 pure water’s density = 1 g/cm3 salt water’s density = 1.0270 g/cm3

Density of water increases when salinity increases

Density of water increases when temperature decreases

So, the coldest and saltiest water is found at the bottom

Ocean Layers and Ocean Mixing

Characteristics of ocean layers depth 0-100 m: warmed by solar radiation and well

mixed Thermocline: a layer that occurs due to a drastic

decrease in temperature in a short distance. Halocline: a layer that occurs due to a drastic increase

in salinity in a short distance. Pycnocline: where changes in temperature and

salinity create rapid increases in density

Ocean Layers and Ocean Mixing

Vertical mixing (overturn or down and upwelling) vertical overturn results when denser water at

the top of the water column sinks while less-dense water rises

isopycnal—water column that has the same density from top to bottom. No mixing occuring

vertical mixing allows water exchange between surface and deep waters

nutrient-rich bottom water is exchanged for oxygen-rich surface water

Continental Shelves

Average 67 km (40 miles) wideDescend gradually from shore to depths of

130 m (430 feet) at this point, bottom may become steep slope or shear

drop-offRivers carry large amounts of sediment to

coastal seas, providing nutrients that settle on the shelves or are dissolved in the seawater

Plenty of sunlight

Benthic Communities

Role of sediments epifauna are adapted to bottoms composed of coarse

sediments (where currents on the bottom are strong) epifauna—animals that live on surface sediments

infauna are adapted to bottoms of fine sediments (where currents are weak) infauna—animals that burrow in the sediments

Multicellular Algae

Seaweeds are multicellular algae that inhabit the oceans

Major groups of marine macroalgae: red algae (phylum Rhodophyta) brown algae (phylum Phaeophyta) green algae (phylum Chlorophyta)

Distribution of Seaweeds

Most species are benthicBenthic seaweeds define the inner

continental shelf, where they provide food and shelter to the community compensation depth—the depth at which the daily or

seasonal amount of light is sufficient for photosynthesis to supply algal metabolic needs without growth

Distribution is governed primarily by light and temperature

Distribution of Seaweeds

Effects of light on seaweed distribution chromatic adaptation, proposed in the 1800s, was

accepted for 100 years chromatic adaptation—the concept that the distribution

of algae was determined by the light wavelengths absorbed by their accessory photosynthetic pigments, and the depth to which these wavelengths penetrate water

such zonation does not occur distribution depends more on herbivory, competition,

pigment concentration, etc.

Distribution of Seaweeds

Effects of temperature on seaweed distribution diversity of seaweeds is greatest in tropical waters,

less in colder latitudes intertidal algae can be killed if temperatures become

too hot or cold

Structure of Seaweeds

Thallus—the seaweed body, usually composed of photosynthetic cells if most of it is flattened, it may be called a frond or

blade

Holdfast—the structure attaching the thallus to a surface

Stipe—a stem-like region between the holdfast and blade of some seaweeds

Biochemistry of Seaweeds

Photosynthetic pigments All seaweeds have chlorophyll a plus:

chlorophyll b in green algae chlorophyll c in brown algae chlorophyll d in red algae

Chlorophylls absorb blue/red, pass green

Biochemistry of Seaweeds

Composition of cell walls Primarily cellulose May be impregnated with calcium carbonate in

calcareous algae Many seaweeds secrete slimy mucilage (polymers of

several sugars) as a cell covering holds moisture, and may prevent desiccation can be sloughed off to remove organisms

Some have a protective cuticle—a multi-layered protein covering

Reproduction in Seaweeds

Asexual reproduction Fragmentation—asexual reproduction in which

the thallus breaks up into pieces, which grow into new algae

drift algae—huge accumulations of seaweeds formed by fragmentation

Asexual reproduction through spore formationSexual reproduction

Sex cells are released in the water

Green Algae

Structure of green algae Most are unicellular or small multicellular filaments,

tubes or sheets Some have a coenocytic thallus consisting of a single

giant cell or a few large cells containing more than 1 nucleus and surrounding a single vacuole the cell grows and the nucleus divides

There is a large diversity of forms among green algae

Green Algae

Response of green algae to herbivory Tolerance: rapid growth and release of huge numbers

of spores and zygotes Avoidance: small size allows them to occupy out-of-

reach crevices Deterrence:

calcium carbonate deposits require strong jaws and fill stomachs with non-nutrient minerals

many produce repulsive toxins

Red Algae

Primarily marine and mostly benthicRed color comes from phycoerythrinsStructure of red algae

Almost all are multicellular Thallus may be blade-like, composed of branching

filaments, or heavily calcified algal turfs—low, dense groups of filamentous and

branched thalli that carpet the seafloor over hard rock or loose sediment

Red Algae

Response of red algae to herbivory making their thalli less edible by incorporating

calcium carbonate changing growth patterns to produce hard-to-graze

forms like algal turfs evolving complex life cycles which allow them to

rapidly replace biomass avoiding herbivores by growing in crevices

Red Algae

Ecological relationships of red algae a few smaller species are:

epiphytes—organisms that grow on algae or plants epizoics—organisms that grow on animal hosts

consolidation—process of cementing loose bits and pieces of coral together red coralline algae precipitate calcium carbonate from

water and aid in consolidation of coral reefs

Red Algae

Commercial uses of red algae phycocolloids (polysaccharides) from cell walls are

valued for gelling or stiffening e.g. agar, carrageenan

Irish moss is eaten in a pudding Porphyra are used in oriental cuisines

e.g. sushi, soups, seasonings cultivated for animal feed or fertilizer in parts of Asia

Brown Algae

Familiar examples: rockweeds kelps sargassum weed

99.7% of species are marine, mostly benthicOlive-brown color comes form the carotenoid

pigment fucoxanthin

Brown Algae

Distribution of brown algae more diverse and abundant along the coastlines of

high latitudes most are temperate sargassum weeds are tropical

Found in the Gulf of Mexico

Brown Algae

Structure of brown algae bladders—gas-filled structures found on larger blades

of brown algae, and used to help buoy the blade and maximize light

cell walls are composed of cellulose and alginates (phycocolloids) that lend strength and flexibility

trumpet cells—specialized cells of kelps that conduct photosynthetic products (e.g. mannitol) to deeper parts of the thallus

Brown Algae

Brown algae as habitat kelp forests house many marine animals sargassum weeds form floating clumps that provide a

home for unique organisms

Commercial products from brown algae thickening agents are made from alginates once used as an iodine source used as food (especially in the Orient) and cattle feed

Kelp Communities

Kelp communities kelp beds

may be underwater forest with canopy and understory; kelp may be distanced or dense

Kelp Communities

Kelp communities kelp life cycles

spores germinate with sufficient light microscopic form establishes itself only if it is not over-

consumed by herbivores stipes grow upward and spread out into a canopy mature kelps constantly grow and erode

Kelp Communities

Kelp communities (continued) kelp community

kelps provide food, shelter or both kelps may increase usable habitat many filter feeders and some herbivores rely on kelp

forests

Kelp Communities

Kelp communities (continued) impact of sea urchins on kelp communities

kelps are a favorite food of sea urchins sea urchins are usually held in check by wave action and

predators decline in predators (e.g. otters) can lead to urchin

population explosion and mass destruction of kelp forests

Neritic Zone: Water Covering Continental Shelf

Food chains in the neritic zone phytoplankton growth is supported by nutrients from

freshwater runoff from land zooplankton feed on phytoplankton

most abundant are copepods (crustaceans) benthic filter feeders eat phytoplankton small fish eat zooplankton large fish eat filter feeders fewer trophic levels than in the open sea

Neritic Zone

Productivity in the neritic zone areas of upwelling, where nutrients are brought from

the ocean floor to the surface where plankton live, are the most productive

Other roles of plankton in coastal seas many animals spend some part of their lives as

members of plankton having planktonic larvae allows sessile organisms to

disperse to new areas