Accomplished Swimmers What are Nektonic Animals? Organisms that have developed powers of locomotion; capable of movement at will

Nekton

• Accomplished Swimmers

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

• 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

Defense Mechanisms

Defense Mechanisms

Defense Mechanisms

Defense Mechanisms

• Color and Camouflage

• Countershading - dark dorsal side, light ventrally

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
• Salmon
• Sea Turtles

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
• Magnetite (Fe3O4) crystals transduce the geomagnetic field to the nervous system

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:

• Ergerg
• Earert

• Temperature

• Currents

• Turbulence

Recruitment & Lifestyles

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

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

Sea Grass Food Web

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