The Benthos

"The length of food chains is a crucial determinate of the functioning of ecosystems," says Alan Tessier, program director in the National Science Foundation (NSF)'s Division of Environmental Biology.

Roughly translated, diversity in an eco-system is of prime importance. This diversity is not limited to the number of levels in a food chain, but the diversity within each level provides a key element of stability to the entire food chain. The lower the level of the food chain, the more important and crucial this diversity becomes.

Biofilm, as indicated in the previous post, forms the true foundation upon which an aquatic food chain is established. Also of extreme importance is what is called the Benthic layer or Benthic zone.

The Benthic zone is the ecological region at the lowest level of a body of water including the sediment surface and some sub-surface layers. This region extends from water’s edge to water’s edge and encompasses the shallow (littoral) regions as well as the deepest (i.e. the profundal region that exists is lakes).Organisms living in this zone are called Benthos. They generally live in close relationship with the substrate bottom; many such organisms are permanently attached to the bottom. The superficial layer of the soil lining the given body of water, the benthic boundary layer or BBL, is an integral part of the benthic zone, as it influences greatly the biological activity which takes place there.

Benthos, in fresh water biology, refers to organisms at the bottom of bodies of water, such as lakes, ponds, rivers, and streams. The population make up of these communities is influenced not only by type of body of water, but also by the depth of the water plus nutrient availability and, of course, pH and temperature.

There are two types of Benthic organisms:

          Epifauna- live on the surface of the bottom

            Infauna- burrow into the sediment on the bottom

Of the two, Epifauna is the most prevalent form found in an eco-system pond, although some Infauna may exist depending on depth of bottom gravel and the amount of sedimentation.

They are also classified as to size:

Microbenthos (<100mm) includes bacteria & protests

Meiobenthos (100-500mm) includes small metazoan (multicellular animals) and larger protists (single cell organisms).

Macrobenthos (>500mm) includes larger metazoa and Megabenthos

          Megabenthos (very large.)  crustaceans, mollusks, etc.

By what they eat:

Herbivores- feeds on plant material

Carnivores/predators- feeds on other benthic organisms

Detritivores- feeds on dead plant and animal material

And how they eat:

Suspension feeders- eats using a mucus-covered appendage that catches particles in water column

Filter feeders- strain particles from the water column

Deposit feeders- ingest sediment and removing the nutrients

In our next post, we will delve deeper into the roles that each individual type plays in the complex world of an aquatic eco-system. It will be the beginning of an interesting journey into a world of such immense activity that, by comparison, the activity level of your fish is like watching paint dry.