L - Cochin University of Science and Technology

Narayana, 1991 ). Limited input of coarser material in the north may be due to
trapping of coarser material by rivers. During the filtering processes rivers/estuaries
trap coarse size particle and allow only fine particle to escape into the inner shelf.
The sandy nature in the outer shelf may be due to the relict nature of sediments and
the absence of conditions favorable for deposition (Hashimi and Nair, 1981).
The increased percentage of clay in the northern regions in both seasons may
be due to the influence of the river Indus in the north. However, clay content in the
shallow areas of Mormugao area due to the discharge brought by Mandovi and Zuari
Rivers. Harkantra et al., (1980) described 7 major types of substrata with two
differentiated areas as north and south of Mormugao (15° N). Sediment was fine and
dominated by silt and clay in the region north of Mormugao and sandy with little
percentage of silt and clay in the region south of Mormugao. In the present study also
study area could be divided into two parts as fine sediment dominated in the north
and sand dominated in south. Setty and Nigam (1982) found that the inner part of
Gulf of Kutch area hold very fine-grained clayey silt whereas Mumbai region (16-17°
N) was sandy in nature below which sediment was mostly clayey with patches of
sand and silty clay. In Mormugao sector, sandy sediment predominated followed by
clay. The present data agrees well with the above findings.
Seasonal variations in the sediment texture could be due to the monsoonal
flow and also due to the intensity, direction and current speed that makes the
difference in sedimentation.
4.2. Organic matter (OM)
4.2.1. Introduction
Organic content of bottom sediment may be more causal factor than the
sediment grain size in determining infaunal distribution because it is a dominant
source of food for deposit feeders and indirectly for suspension feeders. Organic
matter (hereafter reffered to as OM) may influence benthos through availability of
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