Bottom Feeders

The bottom of the ocean. We're not talking that muck you shuffle your feet through at the beach or the sand you swim by on a SCUBA adventure. We're talking deep, deep ocean. An environment of darkness, extreme pressures, cold temperatures, and limited resources. So when a meal drops in, the critters descend for the feast.

A new article, the April issue of Ecology, describes what happens in the deep sea ecosystem when surplus food drops in. Typically, deep sea animals survive on the dead and decaying matter that sinks from above, which is not as much as you may think. The researchers in this study sent a Remotely Operated Vehicle (ROV) down into the deep waters off of the California coast known as Monterey Canyon (northeast Pacific Ocean). This area receives additional food sources in the form of nutrient-rich sediments that slough off the canyon walls. The ROV took video and soil/mud cores of the canyon floor and walls.

The cores from the canyon floor contained nearly 200 species, but as the cores got closer to the walls there were fewer and less diverse species. Odd, especially since the walls of the canyon have more nutrients than the floor. So what causes this habitat heterogeneity?

Closer to the walls there are larger numbers of bigger, mobile animals such as crabs, urchins, sea cucumbers, starfish, etc. These larger animals consume much of the available food. This has major consequences for the smaller animals that depend on those resources, decreasing their numbers by almost half. So, in some cases, more food is not always better, especially if you are small.

Here's the Ecology article:
Craig R. McClain, James P. Barry (2010) Habitat heterogeneity, disturbance, and productivity work in concert to regulate biodiversity in deep submarine canyons. Ecology: Vol. 91, No. 4, pp. 964-976. (DOI: 10.1890/09-0087.1)
and http://www.sciencedaily.com/releases/2010/04/100405111210.htm