Thursday 25 August 2005

PB6

PTH0151
Spatial variability and community structure of the intertidal rocky shore biota of the coast of Ghana
Armah, Ayaa k¹, Quaye, Audrey k¹, Allotey, Lloyd¹, Lamptey, Emmanuel¹, Sekurancis O K²
1 Department Of Oceanography & Fisheries, University of Ghana, Legon, Ghana
2 Department of Botany, University of Ghana, Legon, Ghana
Author email: akarmah@ug.edu.gh
The rocky shores of Ghana are flanked by several hundred kilometres of sandy beaches making them unique habitats along the Gulf of Guinea from Cote d'Ivoire to Western Cameroon. A quantitative description of the community structure and spatial variability of rocky shore organisms on the coast of Ghana was carried out from December, 2003 to January, 2004. The entire rocky shore, which runs in a west to east direction, was divided into three broad zones (western, central and eastern) within which four random study sites were located in each zone. The study focused on ascertaining species spatial variability and tested spatial differences between the three zones. Four vertical transects were randomly laid at each site and 1x 1 m2 quadrat placed continuously on the transects from the lower shore to the upper rocky stretch during periods of low tide. Species percentage cover and abundance were estimated in each quadrat. Data were subjected to statistical analysis using multivariate techniques. The distribution pattern observed showed a marked distinction between sites at the western zone to those at the central and eastern zones (Bray-Curtis Similarity). Significant difference, though weak, was found between the three zones (ANOSIM). Within zone variations were very pronounced at the western than the central and eastern. There was a spatial declivity in species cumulative dominance from eastern zone to the western zone. Diversity indices measured showed a slight troughing and peaking between the zones. The differences in the community structure between the western zone and, central and eastern zones may be attributed to hydrographic factors including the predominant easterly Guinea Current and to a lesser extent anthropogenic perturbations. We propose long-term monitoring studies to determine the scale of natural spatial and temporal variability, as well as locations of rare species encountered during the studies.

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