Buzz's Marine Life of Puget Sound: May 7, 2015

Thursday, May 7, 2015

SEA OTTERS AND DETRITUS AND EVERYTHING ELSE

Sea Otters are known as a keystone species. This simply means that like the keystone in an arch once removed the entire structure will collapse. In the case of the Sea Otter it is often simplified by saying the otters eat herbivores (sea urchins, snails, chitons, limpets) that feed on kelp thus protecting the kelp beds from being overgrazed which would lead to the destruction of habitat and food resources for many marine species......basically without the otters the very productive and diverse world of the kelp forest would disappear. This has been documented in the real world.

So let's follow the energy flow in the kelp forest and see just what might be a stake here.

KELP FOREST ENERGY FLOW (PACIFIC COAST N. AMERICA):

(Energy flows from 1 to 7)

1. SUNLIGHT (AND NUTRIENTS)

2. KELP and other Seaweeds (mostly large brown seaweeds)

3. KELP DETRITUS (small bits of dead kelp WITH BACTERIA)

4. DETRITIVORES (GAMMARID AMPHIPODS, ISOPODS, OTHER SMALL CRUSTACEANS)

5. 45 SPECIES of INSHORE AND MIGRATORY FISHES THAT FEED ON DETRITIVORES

6. FISH EATING FISHES, RIVER OTTERS, SEALS, SEA LIONS, DOLPHINS, PORPOISES,

BALEEN WHALES, VARIOUS SEA BIRDS, BALD EAGLES, OSPREY

7. KILLER WHALES (ORCA)

The key to the entire ecosystem is, of course, KELP. In the natural world of shallow water Pacific coast of N. America the major organism tasked with controlling the populations of kelp eating herbivores is the SEA OTTER.

NOTE: While other predators (Sea Stars, snails, crabs) also prey on the herbivores they have not demonstrated the ability to keep the herbivore populations in check to protect the kelp beds in the absence of the Sea Otter.