Topic 20Ocean Environments

GEOL 2503Introduction to Oceanography

Major zones of life in a marine ecosystem 2

Some ocean environment facts

• Largest biomass on the planet• Most major groups of organisms

represented• Life originated in oceans

– Earliest fossils – marine algae– All animals have saline body fluids

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Ocean Physical Conditions

• Temperature– Continents 136° to ˗127° F (58° to ˗88° C)– Oceans 81° to 28° F (27° to ˗2° C) little

seasonal variation especially in deep waters• Pressure

– Increases with depth but only minor problem• Salinity

– A limiting factor in some coastal environments

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Energy needed to build organic molecules

• Sunlight for photosynthesis available only in photic zone (<100 -200 m depth). Primary producers - plants.

• Mineral-rich hot springs available in aphotic zone (> 200 m). Primary producers - bacteria (extremophiles). An exciting new ecosystem.

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Ocean Life

• What are some characteristics that enable organisms to live in the sea?

• How is ocean life different from land life?

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Land versus Ocean

Land• structural strength needed to support bodies

against gravity• trees--trunks• animals--skeletons, muscle

Ocean• salt water density similar to tissue of

organisms• structural strength not important except for

breaking wave zones• many delicate and fragile organisms

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Buoyancy

• controlled by density– weight of water displaced

• helps keep floating organisms near surface• supports bodies of bottom dwellers• lessens energy expended by swimmers

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Examples of some floating organisms

• Portuguese Man-of-war jellyfish– secrete gases into a float

• Sargassum seaweed– gas-filled floats

• Chambered nautilus– lives in last chamber– other chambers filled with gas

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Sargassum--brown algae 11

Chambered Nautilus

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Swim Bladders in Fish

• help fish remain neutrally buoyant• some fish gulp air at surface• others release gas directly into swim

bladder• to change depth fish change the amount of

gas in the swim bladder

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Not all fish have swim bladders

• Active, continually swimming predators lack a swim bladder– mackerel, tuna, sharks

• Bottom fish lack a swim bladder

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Body Shape and Flotation• Appendages, spines, ruffles, feathers,

perforated shells help organisms float

Spines Perforations15

Osmosis

• Water molecules move across a semipermeable membrane from region of high concentration of water (lower salinity, fresher) to region of low concentration of water (higher salinity, saltier)

• A gradient-driven process• Skin of living organisms is a semipermeable

membrane• So, if the salt content of organism’s tissues differs

from salinity of sea water, then osmosis will occur16

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Fish and Osmosis

• In fish, the salt concentration in body fluids is between fresh and salt

• Fresh water is tissues moves out of body into the sea (from high water concentration to low)

• Thus, fish must work to prevent dehydration– drink sea water, excrete salt across gills and in

urine18

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Sharks, Rays, and Osmosis

• Body fluids have about the same salt content as ocean

• Sharks and rays (primitive fish) do not have the osmosis problem of other fish

• The same is true of many bottom dwellers– sea cucumbers, sponges

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Salinity may limit distribution• Many species can regulate salt-fluid balance over

only limited salinity ranges• In deep water, salinity is fairly constant• In surface waters, salinity may be a barrier to

migration– coastal waters (estuaries, bays) may have highly

variable salinities• Crabs are successful estuarine animals, can

tolerate variable salinity

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Salinity and Marine Life• Salmon

– spawn in fresh water, adults live in salt water, finally return to fresh water to reproduce

• Atlantic common eel– spawn in Sargasso sea, matures at sea, live as

adults in fresh water• Estuaries, coastal bays

– breeding grounds for many fish and crustaceans that live as adults at sea

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Temperature and Marine Life

• Deep ocean– low and constant

• Surface and close to shore– varies by latitude

• Affects density and viscosity– in cold water, organisms float more easily– in tropics, more appendages, larger surface

area, more gas bubble production, for buoyancy

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Pressure

• Pressure increases 1 atmosphere every 10 meters water depth

• Air-breathing marine mammals and seabirds can dive deeper and for longer than humans because– Streamlined shape (less effort needed)– Store oxygen in muscle tissue– Some have collapsible lungs

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Bioluminescence

• Living organisms producing light• Photophore—light-producing organ

common in mid-depth and deep-water fish

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Bioluminescence—see the Bioluminescence Web Page at http://www.lifesci.ucsb.edu/~biolum/

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Siphonophore—related to jellyfish

• Said to be one of the longest animals on earth and can stretch for more than 40 meters.

• This photo shows only about 10 cm.

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This is a photo of an entire siphonophore taken from an ROV

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Comb Jellies—relatives of jellyfish

• Found near the surface around the world.

• Approximate length 5 cm.

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Dinoflagellates• Much of the

bioluminescence in the sea comes from single-celled algae such as this tropical dinoflagellate.

• Length 1 mm

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Dinoflagellates glow when disturbed. Bioluminescent bays exist where conditions are just right and are major tourist attractions.

Anything that disturbs the water may cause dinoflagellates to bioluminesce.

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Uses of Color

• Transparent—blend in with water (jellyfish and many other plankton)

• Bright colors—match coral• Decoration—camouflage, deception• Color may be used as warning or to attract

mates• In turbid water fish often darker colored

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The coloration of oceanic animals, shown as a function of depth.

From NOAA’s Ocean Explorer: http://oceanexplorer.noaa.gov/explorations/explorations.html33

Colors versus depth• This diagram on the next slide offers a basic

illustration of the depth at which different colors of light penetrate ocean waters.

• Water absorbs warm colors like reds and oranges (known as long wavelength light) and scatters the cooler colors (known as short wavelength light).

• Image courtesy of Kyle Carothers, NOAA-OE • http://oceanexplorer.noaa.gov/explorations/

04deepscope/background/deeplight/media/diagram3.html

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Countershading

• Many fish are colored on the top side but white on bottom

• This is for camouflage• When seen from above they blend in with

sea (or river, lake) bottom• When seen from below during day they

blend in with sun light

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Bottom Types

• Referred to as substrate• Type of ocean bottom

– Rock– Mud– Sand– Gravel

• Different organisms preferred different substrates

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Environmental Zones

• Zone classification of Joel Hedgpeth• Benthic zone—sea bottom• Pelagic zone—water column

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Benthic Environment Zones

• The benthic environment is divided by depth into the following zones: – Littoral (<1%) intertidal- between the tides– Sublittoral (8%) low tide to edge of cont. shelf, 0-200m– Bathyal (16%) 200 – 2000 m– Abyssal (75%) 2000 – 6000 m– Hadal (1%) > 6000 m

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Pelagic Environment Zones–Neritic—Shallow water overlying

continental shelves.–Oceanic—Deep water beyond shelf edge.

• Epipelagic (3%) 0-200 m (surface, illuminated)• Mesopelagic (28%) 200-1000 m• Bathypelagic (15%) 1000-2000 m• Abyssalpelagic (54%) 2000-6000 m• Hadalpelagic (<1%) >6000 m (trenches)

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Marine Provinces

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Marine organisms classified by lifestyle.

• Plankton –float passively, can swim vertically, but not against currents.• They can be divided into phytoplankton (plants) and

zooplankton (animals)• Nekton

– active swimmers (marine fish, reptiles, mammals, birds and others)• Benthos

– live on the bottom (epifauna)– within the bottom sediments (infauna)

• Some organisms cross from one lifestyle to another during their life, for example being planktonic early in life and benthic later (seaweeds, barnacles, clams, many others)

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Feeding Strategies

• Primary Producers (photosynthesis or chemosynthesis)

• Primary Consumers - herbivores• Secondary Consumers – carnivores• Decomposers – break down organic debris

Autotrophs Heterotrophs

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Scientific Classification of Organisms

• Kingdom• -Phylum• -Class• -Order• -Family• -Genus• -Species

Taxonomic Rank

Tiger

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Carnivora

Family Felidae

Genus Panthera

Species tigris

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KINGDOM MONERA

• Simple organisms without a nucleus• Unicellular and colonial• Include the true bacteria (eubacteria) and

cyanobacteria (blue-green algae). • Thus, both decomposers and primary

producers

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KINGDOM PROTISTA

• Mainly single celled organisms; complex cells with a nucleus

– Photosynthetic Plankton (Phytoplankton) - primary producers

– Nonphotosynthetic Plankton (Zooplankton) – primary consumers

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Kelp is a protista that obviously is not unicellular49

KINGDOM PLANTAE

• Multicellular organisms with complex nucleated cells. Photosynthetic primary producers.

• Includes all higher plants. Excludes single celled algae

• Very important on land but unimportant in oceans

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KINGDOM FUNGI

• Multicellular organisms with complex nucleated cells. Decomposers.

• Only important on land

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KINGDOM ANIMALIA

• Multicellular organisms with complex nucleated cells.

• Primary and secondary consumers • Abundant in marine and non-marine

environments.• Includes vertebrates (mainly nekton) and

invertebrates (mainly benthos)

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Animals - 2 main groups• Invertebrates:

–Phylum Porifera–Phylum Cnidaria–Phylum Mollusca–Phylum Echinodermata–Phylum Arthropoda

• Vertebrates–Phylum Chordata

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Animals - Invertebrates• Phylum Porifera

– Sponges, primitive filter feeders• Phylum Cnidaria

– Jellyfish, corals, sea anemones• Phylum Mollusca

– Bivalves - scallops, oysters, mussels, clams– Gastropods – snails, slugs– Cephalopods – squids, octopi

• Phylum Echinodermata– Sea urchins and sea stars

• Phylum Arthropoda– Spiders, scorpions, crabs,

shrimp, insects, millipedes, and more

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Animals - Vertebrates• Phylum Chordata: 50,000 vertebrates• 2 groups

– Jawless forms (Class Agnatha) hagfish, lamprey– Jawed forms – most of the animals we know

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Salinity Terms

• Stenohaline– Organisms withstand only small variation in

salinity– Typically live in open ocean

• Euryhaline– Organisms withstand large variation in salinity– Typically live in coastal waters, e.g., estuaries

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Ocean zones with respect to sunlight penetration

• Euphotic: 0-100m, supports photosynthesis– photic zone

• Disphotic: 100-1000m, barely lit– twilight zone

• Aphotic: below 1000m, truly dark– aphotic

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Dissolved oxygen content

• Hypoxia—low oxygen content in water– less than 2 mg/liter

• Anoxia—no oxygen in water– 0 mg/liter

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