Benthic “The bottom dwellers”

What’s it like down there? Life forms here tolerate cool temperatures, no light and low oxygen levels, but this depends on the depth of the water. The layer of the soil lining the area is an important part of the benthic zone, as it influences greatly the biological activity there.

What do they do down there? They sink; they don't swim They don't float; they stick to rocks Sometimes they move (often they move very slowly or remain stationary), but mostly they just stick to the bottom Benthic organisms are sinkers.

What lives there? Plants, invertebrates, and fish of all sizes Many benthic organisms are filter feeders that strain suspended organisms and organic matter from the water

That’s a lot. More than 95% of marine organisms are Benthic Most live within the shallow continental shelf

Invertebrates Animals “without a backbone” Examples: Cnidaria (anenomes / Corals) Molluscs (snails, clams, mussels, sea slugs, octupus) Arthropods (lobsters, crabs) Echinoderms (star fish, sand dollars, sea urchins)

Cnidaria: Anenomes

Tubsteris Coral

Corals

Corals

Coral Reefs Coral animals construct coral reefs They do this by secreting hard skeletons of aragonite (type of calcium carbonate)

Mollusks Most have internal or external shells Name means “soft body” Clam

Snails

Sea Slugs

Sea Slugs

Octupus

Arthropods are animals with an exoskeleton and a segmented body, and paired jointed appendages Lobsters Bullseye lobster

Crabs Hermit crabs

Echinoderms Brittle Star

Star Fish

Feather star

Brittle star

Sand Dollars

Sponges Spawning sponge

Comb Jellies Comb Jellies are often mistaken for jellyfish, but they are not jellyfish because they do NOT have stinging cells Instead they have sticky tentacles and oral lobes to capture prey.

With shimmering, iridescent rainbow patterns formed by the diffraction of light from the comb plates, ctenophores are often thought of as some of the most beautiful creatures in the sea! Comb jellies are the largest of all animals that utilize the beating of cilia for locomotion.  It doesn't stop there - with lengths up to 2 mm, ctenophore cilia are the longest of any known.  Each single comb within a row is made up of several thousand cilia, and each row may have dozens of combs, so an individual ctenophore is endowed with many thousands of cilia.  All adult ctenophores possess eight comb rows, which easily distinguish them from any other type of gelatinous animal. .  

Comb jellies

Comb jelly

Marine worms Giant white tube worm Deposit feeders, such as some worms, feed by ingesting sediments from the bay bottom and extracting nutrients.

Vertebrates Fishes (boney and cartilaginous)- They can swim but live mostly near the bottom

How do they stay on the bottom? Holdfasts (algae) Feet (limpets and snails) Cement (barnacles)

Hydrothermal Vents A hydrothermal vent is a geyser on the seafloor. It continuously spews super-hot, mineral-rich water that helps support a diverse community of organisms Ex. Tubeworms and huge clams (Pacific) Ex. eyeless shrimp

-The vents were not discovered until 1977 -Vent organisms rely on a special kind of bacteria, called chemoautotrophs for food

Eye-less shrimp

Black smoker

Video content Benthic – Intertidal Zone