The "higher" taxa are represented in a variety of marine communities...

Despite their need to breath air, these vertebrates are found from the surface down to depths greater than 1000 m

These taxa occur at much lower diversity and abundance in marine environments than other taxa we have discussed

Marine "herps" (turtles, snakes, lizards):

Sea turtles: Classic turtle form, with hard dorsal carapace and ventral plastron forming the "shell". Front and back legs are modified into flippers that propel through the water.

7 species of diverse size and diet occur in tropical and temperate (less so) waters.

Green turtles (named for the color of their fat) are large (250-450 lbs... record 650 lbs). These are the only herbivorous turtle: they eat sea grasses and algae... often maintain regularly "mown" seagrass meadows.

Hawksbill turtles: medium size (95-165 lbs). They often eat sponges, as well as other benthic inverts.

Loggerhead turtles are medium sized (100-180 lbs)... they consume benthic invertebrates (e.g., conch, crab, echinoderms, etc.)

Leatherback turtles are a huge (650-1200 lbs) pelagic species that eats jellies

Kemp's Ridley turtles are small (80-100 lb) carnivores that consume various benthic invertebrates. Highly endangered because of their extremely synchronous nesting behavior

Olive Ridley turtles are also small (to 100 lbs) and found circumtropically

Flatback sea turtle (100 - 150 lbs) is found only in Australia and New Guinea

Sea turtles have long migrations linked to movements to and from specific nesting beaches.

Many populations are endangered: reports from Columbus' time suggest that sea turtles were once much more common

Threats from humans include depredation of eggs, harvest for meat and shell, and destruction of nesting beaches.

Sea turtle reproduction: Males copulate with females offshore, then eggs laid on land above high-tide... females usually deposit eggs several times during the breeding season... laying 100-200 eggs each time.

Hatching occurs about two months later... the juvenile turtles must survive a gauntlet of predators to reach the sea.

Turtles can live 20-30 years... they reach sexual maturity after about 10 years.

Sea snakes are related to cobras and occur throughout the tropical Indo-Pacific (15 genera comprising some 50 spp)

Most are extremely venomous, however, with their small, fixed fangs and relatively docile nature, they pose little threat to humans.

The tail is flattened for propulsion and their lungs are enlarged, allowing them to remain submerged for several hours.

Typically, they prey on fish either by ambush (sit and wait) or active pursuit into cracks and crevices.

Most sea snakes are viviparous, giving birth to their offspring in the open sea. The banded krait is an exception, it lays eggs on land.

Marine lizards: the Galapagos iguana is a large (approx. 1 m in length and 20 lbs) herbivorous lizard that frequents shorelines.

Although they forage subtidally, much of their time is spent above the surface: breeding and egg laying are terrestrial

Saltwater crocodiles:

The most famous examples are found in northern Australia, these large crocodiles measures up to 10 m in length. They eat fish, birds, and mammals, including the occasional human. They have been seen swimming many miles offshore, but typically occur in estuary habitats. The American crocodile is smaller and tends to be associated more with estuary and freshwater habitats, but may be encountered in marine environments as well (though not as far out to sea as the Aussie croc).

 

Marine birds:

Various types of birds occur at the interface between the sea and land or air. All feed upon marine organisms and can be important trophic consumers.

Soaring long-range cruisers: albatross, petrels, fulmars and shearwaters... also known as the tube-noses

Variable in size: from the 4 m wingspan of the wandering albatross to petrels the size of a sparrow.

They drink seawater and excrete excess salt from enlarged nasal glands.

They nest on remote islands and spend much of their time over the open ocean.

Most feed while swimming on the surface... kelp, fish, smaller invertebrates, and the flesh of dead organisms.

Flightless divers of the Southern Hemisphere: penguins (up to 4 ft tall and 80 lbs).

Many are found in extremely southern latitudes... however one species lives at the equator

These gregarious birds aggregate in large breeding rookeries. Each female lays a single egg which is often cared for by the male until hatching... both sexes care for the hatchling.

They feed on shellfish, fish, krill, small squid, and other shallow-water inverts.

Large, usually coastal, fishing birds with hooked beaks: pelicans, cormorants, boobies (or gannets), frigate birds, and tropicbirds

Expandable gular pouch (most obvious in pelicans) aids in the capture of fish.

Pelicans and boobies dive from heights up to 100 m and achieve depths of 10 m.

Cormorants, strong swimmers, are "domesticated" and used by Japanese to capture fish.

Frigate birds and tropic birds glean prey by swooping down and plucking food from the surface on the wing.

Nearshore waders and perchers: shorebirds, gulls, auks, terns, puffins, and guillemots

These smaller birds often walk or wade in intertidal habitats. Many feed on benthic invertebrates by probing the sediment with their long bills. Large aggregations may drive prey below harvestable depths... reducing prey intake rates.

 

Marine mammals:

There are three major groups of independently derived marine mammals: cetaceans (whales and porpoises), pinnipeds (seals, sea lions, etc) and sirenians (manatees). As with all mammals, they are homeotherms.... most have blubber or fur for insulation.

Many cetaceans and pinnipeds these can dive to extreme depths. They avoid the bends by never achieving a "supersaturated" state of gas absorption that would allow bubble formation in their blood. They also exhale much of the air before diving and collapse their lungs at 25-50 m. With no air in the lungs, nitrogen cannot enter the blood stream.

Cetaceans: whales and porpoises

Most are extremely vocal and social. Sounds are used for echolocation, communication, and perhaps for prey capture.

Two main groups: toothed whales and baleen whales

Toothed whales and porpoises (Odontoceti) have teeth like most mammals

Orca (killer whales) live in social pods and specialize on certain prey types (e.g. fish, pinnipeds, other whales)

Sperm whales are large carnivores that also swim in pods... they consume giant squid, fish, and krill

Beluga whales are medium sized whales that prey on fish and smaller marine mammals

Porpoises and dolphins are small, fast carnivores that prey on fish and invertebrates

Baleen whales (Mysticeti) sieve large zooplankton such as krill from the water using strips of fibrous baleen

Right whales (e.g. bowhead whales) are continuous "ram" feeders... moving continuously through prey of moderate distribution and abundance

Rorqual or finback whales (e.g. blue whales) are intermittent "ram" feeders.... feeding selectively on dense aggregations of prey that they may produce by herding and bubbles...

Grey whales are somewhat between these two groups and are classified separately, they may feed on swimming crabs and benthic invertebrates

 

Pinnipeds: seals, sea lions, elephant seals, and walrus

All are carnivores... walrus use their tusks to uproot mollusks from the seabed

Sea lions have external ears and walk on their hind flippers while seals lack ears and drag their hind quarters.

Sexual dimorphism is common: In species where males compete for access to females, males can be twice as large as females

Sirenians: manatees and dugongs

These large, sluggish herbivores graze on algae, seagrasses, and other aquatic vegetation in shallow tropical waters

They are most closely related to hyraxes and elephants

All are endangered, threatened by boat propellers and hunting for their meat and oil (this drove the Stellar' sea cow, a resident of the northern Pacific, extinct within 27 years of its discovery in 1741!)

Manatees

Three species of manatee are found in the tropical Atlantic.

West Indian manatee (Trichechus manatus)

Amazonian manatee (Trichechus inunguis)

West African manatee (Trichechus senegalensis)

Some manatee facts:

Female manatees become sexually mature at five years of age... males mature at approximately nine.

Gestation is approximately 13 months. Females produce a single calf every two to five years; twins are rare.

Mothers nurse their young for a long period and a calf may remain dependent on its mother for up to two years.

Dugongs (Dugong dugong) occur in the Red Sea and Australia. Males have tusks.

NOTE: Sea otters are grouped in the weasel family, however they spend most of their life in nearshore waters where they feed on various benthic invertebrates, particularly mollusks and echinoderms

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