Animals of the Benthic Environment

Animals of the Benthic Environment

Animals of the Benthic Environment

The ocean is home to organisms that have adapted to life in or on the ocean floor. From the shore line to the deepest ocean trenches, these organisms called benthos make up more than 98% of the oceans 250,000 known inhabitants. (Thurman & Trujillo, 2004, p. 458)

The term benthos is derived from the Greek word meaning "the deep" and is used to refer to the organisms at the bottoms of the ocean. The benthic zone is one of the two realms of the ocean. The benthic zone starts at the water's edge called the intertidal zone and extends to deep ocean trenches of the abyssal plain.

Life forms in this zone are called benthos. There are two categories of benthos, epifauna and infauna. Epifauna live on the surface of the ocean while infauna live within the ocean floor. "The diversity of benthic organisms is controlled by the availability of food, temperature, salinity, the nature of the oceans bottom and the stability of the environment". (Gross, p. 332)

The sea floor provides a home to the most diverse group of organisms, and their ability to cope with the physical conditions of the ocean is what makes animals of the benthic environment unique.

The benthic zone is comprised of four areas:

* Rocky Shorelines

* Sediment-Covered Shores

* Shallow Offshore Ocean Floor

* Deep Ocean Floor

The Rocky Shorelines

The rocky shoreline is one of the easiest benthic environments to observe. Organism is these areas are called epifauna and are either attached to the bottom of the sea floor or move across it. The rocky shores are divided into two zones, the spray zone and the intertidal zone.

The spray zone, "which is above the spring high tide line, is covered by water only during storms". (Thurman & Trujillo, 2004, p. 459). In the spray zone, organisms must deal with many adverse conditions. Periwinkle snails have shells which they withdraw into to prevent them from drying out during low tide. Rock lice and sea roaches are found in caves on the floor of sea. These organisms find shelter amount the boulders and rocks during the day and scavenge at night for food.

The intertidal zone has areas that are nearly always dry to areas that are almost always submerged and is divided into three subzones. These subzones are the high tide zone, the middle tide zone and the low tide zone.

Animals that live in the high tide zone are similar to those in the spray zone as they need to protect themselves from drying out. For instance, buckshot barnacles have a four-part shell that shuts tight protecting them during low tide. The middle tide zone, which is has a constant rush of sea water, is occupied by many soft-bodied organism such as the sea anemone and hermit crabs. The low tide zone is most densely inhabited area of the three subzones. Shore crabs are common and hide in the cracks and rocky crevices. Their exoskeletons allow them to spend a lot of time out of the water without drying out.

The Sediment-Covered Shores

"Tidal marshes, beaches, and estuarine shorelines offer a variety of habitants for benthic plants and animals." (Gross, 1987, p. 339). Organisms in this area burrow into the sediment and are called infauna. Burrowing allows a more stable environment for these organisms and it helps keep them hidden from predators.

There are three different types of feeding methods used by the inhabitants of the sediment-covered shores. The first method is called suspension feeding or filter feeding. This is where a siphon is used to filter plankton from the ocean.