Marine Ecology

• Biology – finally!• Why do we care?

– Fishing– Water quality– Diversity of species– Medicines

Ocean Habitats• Two major marine provinces

– Benthic = bottom– Pelagic = water column

BREAK

Benthic Zone• Littoral or Intertidal zone – area between

high and low tide• Sublittoral zone – from low tide to shelf

break, ~continental shelf• Bathyal zone – shelf break to 2000 m• Abyssal zone – from 2000 to 6000 m• Hadal zone – sea floor deeper than 6000 m,

trenches

Pelagic Zone

• Neritic zone – shallow water above the continental shelf

• Oceanic zone – deep water of open ocean beyond the shelf break

Oceanic Zones

• Epipelagic – from surface to 200 m, the maximum depth of light penetration

• Mesopelagic – between 200 and 1000 m, no light

• Bathypelagic zone – between 1000 and 2000 m

• Abyssalpelagic zone – between 2000 and 6000 m

• Hadalpelagic zone – greater than 6000 m, trenches

Percentage of Marine Habitats

Volume (%)Depth (m)Zone

1>6000Hadal752000-6000Abyssal16200-2000Bathyal80-200Sublittoral

Benthic<1>6000Hadalpelagic542000-6000Abyssalpelagic151000-2000Bathypelagic28200-1000Mesopelagic30-200Epipelagic

Pelagic

Light Zones• Yet another way to classify the ocean• Photic zone

– light is sufficient for photosynthesis– to 100 (or 200 m)

• Dysphotic zone – light is too weak for photosynthesis– twilight zone– < 5% sunlight– 100 to 200 m

• Aphotic zone – no light

Classification of Organisms• Kingdom

– Phylum• Class

– Order- Family

- Genus - Species

• Genus names are capitalized• Genus and Species are italicized

– Homo sapiens

Major Marine Kingdoms

• Monera– Bacteria and blue-green algae

• Protista– Single-celled organisms

• Fungi– Multicelled organisms, which feed on

decay and are not plants or animals

• Metaphyta– Plants that are attached to the sea floor

• Metazoa– All multicellular animals

Monera• Bacteria

– Important for decomposition, synthesis of organic compounds, and release of nutrients

• Blue-green algae– Single cells, which lack a nucleus and

convert ammonia and nitrogen into nitrates and nitrites

Protista• Single celled organisms with a nucleus• Plants and animals

– Foraminifera, coccoliths, diatoms, radiolaria dinoflagellates

• Generate deep sea oozes – carbonates and silicates

Fungi

• Abundant in the intertidal zone• Not as diverse as on land• Important in decomposition

Metaphyta• Plants that grow attached to the sea floor

– Red, brown, and green algae– Advanced plants of salt marshes and coastal

swamps

• Only found in shallow areas where bottom is in the photic zone

Metazoa

• Mollusks – clams, oysters, snails, squid

• Arthropods – barnacles, crab, shrimp• Analids – polychaete worms• Ctenophores – comb jellies• Brachiopods – lamp shells• Echinoderms – starfish, sea urchins,

sea cucumbers• Chordates – fishes, sea turtles, seals

and whales– o Whales, seals, and dolphins are

mammals – warm blooded – Class Mammalia

– o Sharks and fish - cold-blooded –Classes Chondrichthyes and Pisces

– Sea turtles – Class Reptilia

Metazoa• All multicellular animals

Classification by Lifestyle

• Plankton – animals that float and have no ability to propel themselves against the current– Phytoplankton

• plants• Primarly productivity through

photosynthesis

– Zooplankton • Animals• Eat the phytoplankton

– Some can migrate vertically

• Nekton – active swimmers– Marine fish, reptiles, mammals, birds…– Larger ones can swim against currents– Distribution controlled by T and S

Classification by Lifestyle

• Benthos – Epifauna - live on the bottom– Infauna – live within the bottom

sediments– Note: fauna signifies animals not plants

• Plants are restricted to photic zone• Bacteria and animals survive at all

depths, including trenches

Classification by Lifestyle• One Problem: some animals start as

planktonic or benthic or even nekton and change to nekton or benthic

Basic Ecology

• Ecosystem– The total environment including the

biota (all living organisms) and non-living physical and chemical aspects

Basic Ecology• Environmental factors affecting life

– Temperature– Salinity– Pressure– Nutrients– Dissolved gasses– Currents– Light– Suspended sediments– Substrate (bottom material)– River inflow– Tides– Waves

Temperature Effects

• Can control distribution, degree of activity, and reproduction of an organism

• Temperature controls the rate of chemical reactions within organisms, thus their rate of growth and activity– 10oC rise in temperature, doubles the

activity– Polar organisms grow slower,

reproduce less frequently, and live longer than tropical organisms

– Tolerance to variation in temperature varies greatly between species and within an organism’s lifespan

– Temperature can indirectly control organisms by limiting their predators or restricting pathogens

Temperature Effects

• more activity with higher temperature

Clams and Green Crabs

•

Salinity Effects• Can control the distribution of

organisms and force them to migrate in response to changes

• Availability of various dissolved chemicals (calcium and silicon) can limit an organism’s ability to construct shells

• Epipelagic organisms are more tolerant to changes, since they are more accustomed to them

• Marine organisms’ body fluids have the same proportion of salts than sea water, but lower salinity

Diffusion and Osmosis

• Diffusion – physical process whereby molecules move from areas of higher concentration into areas of lower concentration

• Osmosis – movement of water molecules through the cell membrane from where salinity is lower to where it is higher– Can result in dehydration of

surrounding water is more saline (saltier, higher salinity)

– Can result in rupturing of the cell if surrounding water is fresher

• Hydrostatic pressure – P=?gh– Gases are compressible, but water not

Osmoregulation• Control of diffusion through the cell wall

and the maintenance of sufficient body fluids

• Marine organisms– Drink large amounts of water– Chloride cells extract and dispose of excess salt

• Freshwater organisms– Don’t drink– Produce large amounts of dilute urine

Selective Adaptive Strategies• Plants

– 90% of marine plants are algae – Most unicellular and microscopic– Photosynthesis

• Takes CO2 and nutrients and makes organic compounds, O2, and energy

• Chlorophyll needed for photosynthesis– More dense than water and sink, but

have evolved various methods to retard sinking

• Increasing surface area slows down sinking because of frictional drag

• Small size results in a better ratio of drag to mass

• Porous shells and spines increase drag– Holdfasts – anchors that plants use to

hold themselves to the bottom• Don’t bring in nutrients or water like the

roots of land plants

Diatoms

• Thrive in cold, nutrient rich waters of polar region and inshore regions of mid-latitudes

• Plankton bloom –– rapid reproduction– Often in spring

• Single cell in siliceous shell shaped like a pillbox -silicates

Selective Adaptive Strategies

• Zooplankton– Copepods

• Small herbivores (plant eaters) that filter diatoms from the water

• Molt their outer skeleton as they grow• About the size of a grain of rice• Migrate vertically seasonally

– Foramifera• Single celled, microscopic organisms• Calcium carbonate shells - Carbonates • Benthic forms outnumber the pelagic• Their shells are porous and protoplasm

streams from inside the shell to engulf and digest food

Copepods and Foraminifera

Selective Adaptive Strategies• Fishes• Morphology of fish has evolved to

allow them to move through the water easily

Three types of Drag• Surface

– Friction between the surface and the water– Reduced by reducing surface area– Sphere offers least surface drag

• Form– Function of volume of water which must be

displaced– Increases as the cross-sectional area increases– Needle or pencil shape has least form drag

• Turbulent– Created around a body as it moves through a

fluid– Reduced by having a blunt leading edge and a

tapering end– Torpedo has least turbulent drag

Speed in Water• Speed dependent on

– Body length– Beat frequency

• number of times the tail (caudal fin) sweeps back and forth in a unit of time

– Aspect ratio of the caudal fin• AR = (caudal fin height)2/caudal fin area• Low aspect ratio

– Tail is broad – Short, rapid acceleration and good

maneuverability but lots of drag – Good for darting motion

• High aspect ratio– Tail is narrow– Ideal for maintenance of high speed,

bad for maneuverability

Three Basic Body Types• Torpedo shape

– Efficient, high speed cruising

• Elongate– Rapid acceleration

• Circular– High maneuverability

Intertidal benthic Communities

• Vary with the substrate (bottom material)– Rocky – firm, stable material for

attachment, but prevents burrowing– Sandy – mobile and abrasive, but can

be burrowed into– Mud – provides little support, but is

easy to burrow through– Infauna dominate in sand and mud