Oceanography- Animals and the Pelagic Environment

What are the different ways animals stay afloat in the ocean?

Buoyancy, Swim Bladders, Swimming

Buoyancy

• Gas containers → swim bladders, phytoplankton gas vaccuoles

• Floating, high SA:V, or appendages with drag

Swim Bladders

• Used by slow moving fish

• Organs fill with oxygen to maintain buoyancy and can fill more to float and deflate to sink

• Two types: Physotomous (Open), Physoclistous (Closed)

Swimming

• For larger animals, propulsion keeps them afloat

• no swim bladder needed, although other adaptations like oil-rich livers in sharks give them more buoyancy (oil is less dense than water)

Zooplankton

Plankton are identified floaters, phyto=plant & zoo=animal

Microscopic Zooplankton

Includes copepods, foraminifera, radiolarians

• Radiolarians have silicious shells, are protozoans, and need external Carbon

• Forams have calcium carbonate shells, are protozoans, and need external Carbon

• Copepods are microscopic-ish, look bug-like, and get up to a few mm long. There are over 7500 species, that all lay eggs, and some are herbivores, carnivores, or parasites.

Macroscopic Zooplankton

• Includes krill, cnidarians, hydrozoans, scyphozoan, chaetognaths(arrow worms), ctenophore(comb jellies), and salps

• Basically big floaters from a few cm to meters long in colonies(connected), they all float with the current and can’t swim faster than it. -

  • Krill: They look shrimp-like and can get up to a few cm long, they are a food source for baleen whale/blue whales. There are over 1500 species and they are abundant off the coast of Antarctica.

    • Cnidarians: include hydrozoans(portuguese man-of-war) and scyphozoans(jellyfish)

Dorsal Fin

Stability

Myomeres (Muscle Tissue Fin)

Provides stability

Caudal Fin

Propulsion

Pectoral / Pelvic Fin

Steering, braking, balance

Anal Fin

Stability

Rounded Fin

- Flexible (soft), good for maneuvering, slow swimmers Ex. Angelfish

Forked Fin

- Somewhat flexible, maneuverable but faster than rounded

Lunate Fin

Fastest fin, rigid, not good for maneuvering,

Ex. Tuna

Truncate Fin

- Somewhat flexible, maneuverable, faster than forked

Ex. Bass

Crusier Fish

Fish that

• actively seek prey (tuna, sharks)

• have mostly red muscle tissue, more myoglobin, tend to need more oxygen, and have a greater metabolic rate (~6 times that of white muscle).

Lunger Fish

Lungers wait for prey and pounce (grouper, etc.)

• mainly white muscle tissue, less myoglobin, require less oxygen, and a slower metabolic rate

Why do deep sea fish look they way they do?

Deep sea fish tend to eat detritus (falling organic matter) or each other and they tend to be small. They look the way they do because they adapt to their environment.

• This can include large teeth, hinged jaws, expandable bodies, huge mouths, and bioluminescence.

Bioluminescence

• Photophores: Light producing organisms

• Luciferin: Pigment that produces light

• Counterillumination: the underside bioluminescence that blends into light filtering down

Overfishing

• In the U.S. waters 80% of 191 commercial fished species are fully overexploited or depleted

• Fisheries resources are typically from continental shelves

• Overfishing: occurs when harvesting takes place so rapidly that majority of the population is sexually immature and unable to reproduce

  • 90% of fish from large species have been removed from oceans so smaller fish are now targets

Standing Stock

Mass present in an ecosystem at a given time

Maximum Sustainable Yield

Maximum fishery biomass that can be removed yearly and still be sustained by the fishery ecosystem

Why do fish form schools

• Fish form schools for protection in the open ocean.

• The percentage of area species cover is less so it makes them harder to find and their continuous change in direction can confuse predators

  • Safety in numbers

How do fish form schools

They use the lateral line system and move together evenly spaced.

Major Groups of Marine Mammals

Carnivora, Sirenia, Cetacena

Carnivora

Otters, bears, pinnipeds/walrus+seals

Cetacea

• Whales, dolphins, porpoises, orca, sperm whale

• Blowholes on top of skull - Horizontal tales (flukes)

Odontocetia (Suborder of Cetacenta)

• toothed whales → dolphins, porpoises, orca, sperm whales

Sirenia

Manatees and dugongs/sea cows - Manatees in coastal areas of tropical Atlantic & Dugongs in coastal areas of the Indian Ocean and Western Pacific -

• Herbivores and eat shallow grasses

• Slow moving (3000lbs)

5 Requirements of Marine Mammals- Nekton

1. Warm blooded

2. Breathes air

3. Has at least 1 stage of development

4. Bears live young

5. Females make milk for young

What adaptions do whales have for living as air breathing animals in the ocean?

• Blow hole

• Large lungs / oxygen stores

• Flexible rib cages for pressure

Difference between baleen and toothed whales- Baleen

Baleen whales (mysticeti) have parallel rows of baleen instead of teeth, baleen is made or keratin. To feed the whales take in alot of water then expel it through the baleen, food like krill stays and water goes through.

• Large since they eat low on the food web

Difference between baleen and toothed whales- Toothed whales

Toothed whales (odontoceti) have rows of teeth and they tend to eat bigger organisms. These whales also use teeth for echolocation

Different groups of musticeti

Gray whales, rorquals, and right whales.

Gray Whales

Bottom feeders 2-5 ventral groves on jaw.

Rorquals

Gulp feeders and include balenopterids and megapterids.

• balenopterids have long slender bodies, flukes with smooth edges, minke (blue fin whales).

• megapterids include humpback whales with uneven trailing edge of fluke, and tubercles with hair.

Right Whales

Use sound to communicate and their calls can travel over 50 km.

Heterocercal

Fin is uneven. The top is larger than the bottom, produces lift (sharks)

Photophores

Light producing organismsBy

Bycatch

Marine organisms that are caught by accident, along with the target species

Odontoceti Examples

Orcas, Sperm Whales

Suborder Mysticeti Examples

Gray whales, rorquals, rightwhales