Benthic assemblages for ecological evaluation of Lake Manzala, Mediterranean Sea, Egypt.
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AuthorEl Komi, Mohamed Mohamed
Creative CommonsAttribution-ShareAlike 4.0 International
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AbstractLake Manzalah one of the northern Nile Delta in Egypt is the largest lake, which lies between the lakes Borollus and Bardaweel and connects to the Mediterranean Sea. It has an area of current 250 thousand acres. It contains many islands particularly along the south-western region forming of semi-enclosed basins and it is characterized by dense submerged hydrophytes as Pomatogeton pectinals; Ceratophyllum demersum and floating hyacinth Eichhornia crassipes. Seven major drains are loading directly in the south to the west. Lake Manzalah-bottomed shallow (0.5-1m), brackish water (3-18‰ and is suffering from the phenomenon of high nutrition (eutrophication) due to increased rates of nutrients and organic matter. So some sources of wastes discharges such as sewage and industrial waste and agricultural activity pour directly into the lake, especially the southern region (Bahr El Baqar Drain). The study aims to study the distribution of benthic organisms in the lake and knowledge of the relationship between the types and aggregates benthic food ecosystem as the important food sources' for some aquatic organisms, especially economic fish and crustaceans in study stations. Bottom sediment samples were collected from 11 sites by grab sampler covering different environments lake and from 4 drains consists mostly of organic materials (sludge) is made up of waste sewage, industrial, agricultural waste plants, and calcareous shells empty. Results indicate for examining configuration qualitative macro benthic recording the 16 species of aquatic plants and invertebrates where empty calcareous shells were more frequent. The abundance of macrobenthic organisms at different sampling sites along Lake Manzala can be ranked as follows: Ostracoda (45.4%, 1010 ind/m2) > submerged plants (12.9%, 287 tufts/m2) > Amphipoda (9.2%, 207 ind ∕m2) > Polychaetes (7%, 110 ind ∕m2) Bivalves (5.9%, 132 ind ∕m2). The biomass of benthic assemblages at different sampling sites can also be ranked as follows: at ST5 (18.1%, 4433 ind ∕m2) > St6 (11.3%, 2772 ind ∕m2) > ST8 (9.8%, 2405 ind ∕m2) > ST3 (9.2%, 2247) > ST7 (8.7%, 2122 ind ∕m2). The biomass of benthic assemblages at different sampling sites can also be ranked as follows: echinoderms (52%) > molluscs (27%) > crustaceans (16%) > polychaetes (2%) > other groups (3%). Due to the increase of pollutants extensively loaded into the drains are the possible factors having affecting the constituents’ structures of benthos. Sites of sampling study were evenly spread (J’ > 0.8) only at sites 6 and 8, moderate diversity (H’ > 1.00) was at most sites and show lower value at sites 3 and 11 and 0 at site 1. The abiotic environmental effects in the lake are general to those generally observed in other areas influenced by organic wastes, namely, changes in the physic-chemical properties of the sediments and low oxygen concentrations in the bottom water due to the decomposition of organic materials.
JournalPakistan Journal of Marine Sciences
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