Nekton
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
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
The Epipelagic Environment This is a challenging environment to live in - Extreme 3 dimensionality
- No solid substrate
- No landmarks to use for navigation
Adaptations of the Nekton To be successful, nektonic animals must develop:
Staying Afloat Like plankton, nekton also incorporate lipids into their tissue Sharks concentrate high oil levels in a large liver
Staying Afloat
Staying Afloat
Staying Afloat
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
A Swimming Machine
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
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
Defense Mechanisms - This is a very intense selective pressure, everyone is evolving mechanisms of defense
Sense Organs
Defense Mechanisms
Defense Mechanisms
Defense Mechanisms
Defense Mechanisms
Defense Mechanisms Behavior - Schooling behavior is a method of protection for small fish
Flying Fish - Use modified pectoral fins for gliding above the surface
Migrations Why are migrations made? - Many animals undergo extensive migrations usually for feeding or reproduction
Tuna Migrations
Baleen Whale Migrations
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
The Subtidal Life on the Continental Shelf
The Continental Shelf
Exclusive Economic Zone Biologically, the continental shelf is the richest area of the ocean Countries have extended their borders to protect natural resources
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
Sampling the Benthic Habitat
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
Abiotic Factors Abiotic factors are linked to two fundamental characteristics of the shelf: Temperature Currents
Recruitment & Lifestyles
Soft-bottom Subtidal Communities - There is little primary production so the filter feeders and suspension feeders rely on detritus flushed from estuaries
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
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
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
Kelp Distribution
Kelp Structure
Kelp Zonation
North Atlantic Kelps
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