1. Accomplished Swimmers
Nekton
Accomplished Swimmers
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2. What are Nektonic Animals?
Organisms that have developed powers of locomotion; capable of movement at will
These are the animals that we are most familiar with:
Vertebrates
Invertebrates
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3. Nekton Feeding Biology
Practically all members of the nekton are carnivorous
Planktivorous
Toothed whales, tuna, and sharks are general carnivores eating both other vertebrates and invertebrates
Piscivorous
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4. The Epipelagic Environment
This is a challenging environment to live in
Extreme 3 dimensionality
No solid substrate
No landmarks to use for navigation
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5. Adaptations of the Nekton
To be successful, nektonic animals must develop:
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6. Staying Afloat
Like plankton, nekton also incorporate lipids into their tissue
Sharks concentrate high oil levels in a large liver
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7. Staying Afloat Fishes use stiff fin elements with movable spines
These fins are used as wings to generate lift
Heterocercal tails are used in sharks to generate lifts
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8. Staying Afloat
Hammerhead sharks possess a large wing (hydrofoil) on the front of their head
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9. Staying Afloat Image source: http://www.pskf.ca/sd/images/dcp_4932.jpg
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10. Faster Swimming Speeds
All nektonic animals are evolving mechanisms to swim faster
In many cases, speed is what determines if the prey escapes or if the predator eats
Adaptations are directed towards decreasing drag and increasing forward propulsion
Elimination of protuberances and a streamlined body shape helps
Fast swimmers tuck fins into grooves
The caudal fin provides the major component of thrust
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11. A Swimming Machine
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12. Faster Swimming Speeds
The best swimmers contain a high amount of red muscle
Red muscle gets its color from a high concentration of myoglobin which is great at storing oxygen
Red muscle is best used for long periods of exertion
A difference seen when you compare a tuna versus a flounder
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13. Faster Swimming Speeds
Some pelagic sharks and large tuna have the ability to conserve the heat their muscles generate
This trick of the circulatory system allows cold oxygenated blood to pass closely with the warm deoxygenated blood
There is a transfer of heat to the cold blood before it enters the muscle
Benefit: a warm muscle is more efficient than a cold muscle
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14. Defense Mechanisms There is no cover to hide in the epipelagic
This is a very intense selective pressure, everyone is evolving mechanisms of defense
Sense Organs
Sight
Lateral line
Otoliths
Echolocation
Ampullae of Lorenzini
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15. Defense Mechanisms
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16. Defense Mechanisms
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17. Defense Mechanisms
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18. Defense Mechanisms Color and Camouflage
Countershading - dark dorsal side, light ventrally
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19. Defense Mechanisms Behavior Flying Fish
Schooling behavior is a method of protection for small fish
Flying Fish
Use modified pectoral fins for gliding above the surface
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20. Migrations Why are migrations made?
Many animals undergo extensive migrations usually for feeding or reproduction
Salmon
Sea Turtles
Tuna undergo extensive migrations to fully exploit food resources
Marine mammals (baleen whales) make migrations in a north and south fashion for feeding and calf rearing
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21. Tuna Migrations
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22. Baleen Whale Migrations
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23. Migrations How do marine animals make migrations?
Use variations in water temperature
Walker et al. (1984) found tuna use the earth’s weak geomagnetic field
Magnetite (Fe3O4) crystals transduce the geomagnetic field to the nervous system
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24. Life on the Continental Shelf
The Subtidal
Life on the Continental Shelf
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25. The Continental Shelf
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26. Exclusive Economic Zone
Biologically, the continental shelf is the richest area of the ocean
Countries have extended their borders to protect natural resources
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27. Shelf Habitats
The continental shelf shares many similarities with the intertidal community
Unlike the intertidal, the animals that live on the shelf are never exposed to air
The deeper areas have different physical conditions
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28. Sampling the Benthic Habitat
Grabs
Dredges
Bottom trawls
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29. Soft-Bottom Subtidal Communities
This substrate dominates the world’s continental shelves
Animals that live here share many traits with animals that live in the sandy intertidal
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30. Abiotic Factors
Abiotic factors are linked to two fundamental characteristics of the shelf:
Ergerg
Earert
Temperature
Currents
Turbulence
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31. Recruitment & Lifestyles
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33. Soft-bottom Subtidal Communities
Notable absence of large plants and algae
There is little primary production so the filter feeders and suspension feeders rely on detritus flushed from estuaries
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34. Seagrass beds Areas that are carpeted by flowering plants
They develop best in sheltered shallow areas along the coast
Eel grass is our most common representative
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35. Seagrasses
Thick mats of eel grass provide lots of habitat for animals to hide
By stabilizing the sediment it decreases the turbidity
Dead sea grasses provide lots of detritus that benefit suspension, deposit and filter feeders
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36. Sea Grass Food Web
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37. Hard-Bottom Subtidal Communities
Animals that are present have the same characteristics as those of the rocky intertidal
Red and brown algae dominate
Zonation related to sunlight penetration
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38. Kelp Distribution
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39. Kelp Structure
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41. Kelp Zonation
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42. North Atlantic Kelps
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