Distribution of benthic communities affected by human activities in the west coast of Alexandria, Mediterranean Sea, Egypt | ||||
| Egyptian Journal of Aquatic Biology and Fisheries | ||||
| Article 3, Volume 16, Issue 1, January 2012, Page 41-59 PDF (268.86 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/ejabf.2012.2110 | ||||
 View on SCiNiTO | ||||
| Author | ||||
| Mohamed El-Komi | ||||
| National Institute of Oceanography and Fisheries, Alexandria, Egypt | ||||
| Abstract | ||||
| In the framework of marine ecosystem evaluation, this study was carried out where sediment microorganisms were collected bimonthly from 16 sites over one year in the western coast of Alexandria. This area comprises different human activities (urban sewage, agriculture irrigation, industrial wastes, petroleum spill, tourist stress, fishing and commercial navigation). Macrobenthos communities are well indicators of water and sediment quality. Bottom invertebrate’s diversity, comparison of benthos communities at different sampling sites and the biomass were determined as well as the numerical abundance of benthos in comparison to the different environmental parameters. Discharging of chemical pollutants in coastal waters leads to significant degradation in the water quality that altered the macro invertebrates’ diversity indices. The most western sites are less stressed area indicating low diversity rather than the stressed area close to the main sources of pollutants discharge that has relatively high pollution and generally with good diversity. The benthic communities are dominated by few species of pollution tolerance which are used as indicators of polluted sediments such as free-living nematodes and polychaetes. The regional distribution of benthic invertebrate’s communities varied at different sites and over the period of collections that total abundance ranged from 959 to 8444 ind./m2 with an annual average of 3072 ind./m2 and seven benthos groups can be sequenced as follows: Nematodes 46% > polychaetes 22% > amphipods 13.8% >cirripedes 4.8% > oligochaetes 4% > gastropods 3.0% > bivalves 1.5%. On the other hand, biomass of benthic structure has an annual average of 155 g/m2, where six predomination benthic groups can be ranked in the following sequence: Cirripedes 33.5% > Algae 30.6% > Gastropods 12.7% > Bivalves 9.1% > Sea grass 7.0% > Polychaetes 1.7%. At the different sites, the general structure of species number of benthos groups indicated that Polychaeta was the most common group comprising 27 species of 80 the total number of taxa. The values of species diversity (H`) had relatively moderate diversity (1.3 – 2.02) at most stations and in general the decline in diversity is primarily attributed to the uneven distribution of individuals among the species. On the other hand, the species diversity was only 1.6 at Site 2 though it was the richest that may be attributed to the number of species. Values of the evenness index indicated that sites 1, 8, 9, 10 were highly diverse in benthic communities. The Swartz’s dominance index value indicated less stress with high diversity and number of species. The area located close to the outfall of the two main drains are characterized by having distinct eutrophication level leading to significant increase in the species richness and mean abundance of benthic communities of the tolerant species. Continuous monitoring and assessing of macrobenthic communities is needed to determine the short and long-term changes in the marine ecosystem that are essential for fisheries management along the coastal region. | ||||
| Keywords | ||||
| macro benthos; impact of pollution; biodiversity; benthic communities; Polychaetes; bivalves; Crustaceans | ||||
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