CH 4, CH 7, CH 16 Continental Shelf / Neritic Zone Unit.
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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
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