Marine Biology

Substratum

As this area is having very fine particles and flat surface, it is known to retain high amount of interstitial water with in the substrate. This retention of water in its interstitial space for long time leads to the poor exchange of water and high load of microbes in it may results in the formation of anoxic condition below the surface of the sediments. Between the upper aerobic layer and the lower anaerobic layer is a transition zone called the redox potential discontinuity (RPD) layer. Below the RPD zone, sediments are anaerobic and decomposition of organic compounds is by anaerobic bacteria. The anoxic RPD layer is characterized by the gray colour of the sediments; the oxidized layer above is usually brown or yellow; and the anoxic layer is black. In the RPD zone, chemoautotrophic bacteria are the common forms present.