MAY 2011
OCEANOGRAPHY Ch # 12
Marine Life and the Marine Environment
Introduction
Wide variety of organisms – Microscopic to the size of the Blue Whale. Most live in the upper
column of water through which light penetrates.
Advantages in the marine Ecosystem – Water is necessary for all life
Disadvantage – Hi density of water makes it difficult in which to maneuver.
12 – 1. What are the living things and how are they classified?
Life – Consumes energy from its environment, can replicate itself. Water must be part of it. It
has to have a membrane with which to separate itself from its environment. It responds to
stimuli, adapts to the environment and is carbon based. Can capture, store and transmit
energy, and change thru time.
Three Domains (of life)
Bacteria
Archaea – simple microscopic, bacteria- like.
Eukarya – complex, multicellular animals and plants, fungi
Five Kingdoms of organisms
Monera – single cell, lacks discrete nucleus and internal organelles. Inhabit shallow
coastal water.
Plantae – plants, multicelled, photosynthesize.
Animalia – multicell animals, vary from sponges to complex vertebrates.
Fungi - > 100,000 species, < one half are marine. Live in the intertidal zone.
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Protectista – Single and multicelled organisms that have nuclei. Includes algae and
protozoa.
12 – 2. How are marine organisms classified?
According to habitat and movement.
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Plankton – Floaters. Are abundant and most important. Most abundant biomass.
Types include: Phytoplankton- self feeding; Zooplankton – animals;
Bacterioplankton.
Nekton – Swimmers, capable of independent movement; adult fish , squid, marine
mammals, reptiles. Their range of movement is limited to their range of tolerances.
Benthos – bottom dwellers. Infauna lives buried in the bottom sediment.
Hydrothermal Vent Biocommunities (1977) live on chemicals.
12 – 3. How many marine species exist?
1.75 Million species. Estimate 3 – 100 Million undiscovered . 250,000 marine species.
Few species in the marine envir because it is more stable than the terrestrial. (uniform
conditions in the ocean.
Species in the pelagic and benthic environments. Only 2% live in the pelagic and 98% in the
Benthic. The sea floor has more habitats.
12 – 4. How are marine Organisms adapted for the physical conditions of the Ocean?
Organisms are not pressured to adapt to the Temp, Press, Salinity and Turbidity because
conditions are relatively uniform.
Need for physical; support : Land plants have roots to anchor to the ground. Animals have a
skeleton and appendages to support weight. In the Ocean, water supports plants and animals.
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Viscosity – internal resistance to flow, and is affected by temp. Single celled animals
float in colder water, higher viscosity, has less need for extensions to maintain their
positions near the surface. Warm water species have ornate appendages.
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Importance of size. Phyto plankton has basic requirements, namely:
To stay in upper part of water column where solar radiation is available, where
nutrients are available. To efficiently make use of nutrients and expel waste.
Size and shape help to meet the requirements without the need for specialized multiple cells
Resistance to sinking increases as the ratio of sfc area to mass increases. Diatoms have unusual
appendages to increase sfc area to keep afloat. Other organisms produce a drop of oil which
lowers their overall density and increases buoyancy.
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Viscosity and streamlining. As size increases, viscosity ceases to enhance survival and
becomes an obstacle. Streamlining offers the least resistance to fluid flow.
Temperature. Heat capacity of water is much greater than that of land. This causes
land to heat up by a much greater amount much more rapidly than water. Ocean
warming is reduced due to evaporation. Radiation penetration is greater in water
and heat is distributed throughout. Contrast, Radiation on land is absorbed only in
the upper few inches. Unlike land, water mixes thru currents, waves and tides. And
heat is transferred to other areas.
Compare warm and cold water species. Density and viscosity in cold water is greater – leads to
difference in species.
Floating organisms in warm water are smaller
Warm water species have ornate plumage to increase surface area
Warm water increases biological activity, growth is faster and life span is shorter.
More species in warm water, but total biomass of plankton in cold water exceeds that
in warm.
Organisms have a very narrow range of tolerance – Stenothermal. But shallow water
organisms have a wide range of tolerance – Eurythermal.
Salinity. In the open ocean, organisms are adapted to a constant salinity – stenohaline. Those
in coastal waters are euryhaline.
Extraction of salt
Diatoms extract Silica to Construct Hard body parts for protection. Forams and corals, mollusks
extract CaCO3
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Diffusion – nutrients moving from areas of concentration. Organisms have a permeable cell wall
for nutrients entering and for waste disposal.
Osmosis – molecules of water diffuse from low to high concentrations thru a semi-permeable
membrane.
Isotonic – both organism and water are equally saline. The organism is isotonic.
Hypertonic – sea water has a lower salinity than the organism, and will pass thru the
skin into the organism with the higher salinity.
Hypotonic – Organism has a lower salinity.
During osmosis Nutrient molecules move from concentrated regions to the cell. Waste
molecules move from the cell to the surrounding water.
Marine vs fresh water (Osmosis)
Marine fish is hypotonic or less salty than the water. They drink ocean water and
excrete salt thru their gills.
Fresh water fish are hypertonic. They do not drink water. Their cells have the ability to
absorb salt. They excrete large volumes of very dilute urine to reduce the water content of their
cells.
Dissolved gases.
The amount of dissolved gases increases as the temp of sea water decreases. In hi lat
areas there is an abundant CO2 and O2 dissolved. Supplies deep sea organisms with O2.
Organisms extract O2 thru their gills, exchange CO2 for O2 directly from sea water.
Water’s high transparency
The max penetration of light is a 1000 met. But depends on turbidity, plankton content,
time of day and latitude. Consequently, many organisms have good eyesight. Helps to locate
food
To combat predators, many organisms make them selves transparent or have large teeth, give
off toxins, or have great speed or size. Others use camouflage- counter shading or disruptive
coloration,
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Pressure
Increases 14.7#/inch square with every 10 meters depth. Most marine organisms do not have
large compressible air pockets inside their bodies.
12 -5. The Main divisions of the Marine Environment.
Pelagic – Neritic , extending from shoreline to 200 met deep water.
Oceanic – beyond 200 meters.
Oceanic can be divided into biozones
Epipelagic – to 200 met, only place where there is sufficient sunlight for
photosynthesis. O2 decreases significantly below this depth.
Mesopelagic (200 – 1000 met) Often has high nutrient content. Many organisms
are capable of bioluminescence in this zone.
Bathy pelagic and Abyssal pelagic zones represent 75% of the living space in the
ocean. Habitat of many blind fish, small predators. Food supply is less than the higher zones,
mostly detritus. Animals feed on each other, all have large mouths and large teeth. O2 levels
increase due to deep sea currents.
Benthic – Sea bottom envir. Supratidal. Is the transitional area from the land to the sea.
The rest of the benthic province is:
Subneritic – Littoral or intertidal
Sublittoral - Inner to a depth at which algae can no longer grow –50 met.
Outer to the seaward edge of the shelf.
Sub Oceanic – Bathyal 200 – 4000 met
Abyssal 4000 – 6000 met. Covered by soft sediments, clay
Hadal -> 6000 met.
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