Zooplankton of highly eutrophic, sewage polluted coastal lagoons off Jeddah, central Red Sea

Abstract EN

The occu rrence and abundance of zoo plankton in sewage pollut ed coas ta l areas of Jedd ah in Al-Arbaeen and AI-Shabab lagoon s were st udied monthly during the period November 1990 to October 199 1.

Based on the physicochemical parameter s studied in both lagoon s (i.e.

sa linity , pH and disso lved oxygen), the environment of Al-Shabab lagoon was comparative ly less , polluted than that of Al-Ar baeen lagoon, In Al-Arbaeen lagoon surface value s of salinity and di ssolved oxygen var ied between 8'1<0 and :\7'1<0 (mean 26.6%0) and 0.04 mg/I and 7, I mg/ I (mea n 1.83 rng/l ); the co rres ponding values in AISh abab lagoon were: 16'1<0 and 4 1%0(mean 33%<.) and 0.29 mg/l and 9A l mg/ I (mean 4.

11 mg/ l).

Generally a signifi cant posit ive co rrel ation was found between each o f d issol ved ox ygen and pH wi th salinity.

Howe ver , the IOtaJ zooplankton crop in Al-Shabab lagoon (average 1850 ind/nr') was re lat ivel y lower than in Al-Arbaeen lagoon (ave rage 3560 ind/rn '), The standing crop of co pep od s in Al-Arbaeen and Al-Shabab lagoons were 86% and 34% of the total zoo plankton resp ecti vely.

The low standing cro p of Al-Shabab lagoon was due to the low copepod de nsit y.

In both lagoons the cope pod populations were not di ver sified taxonom ically and only a limited numbe r of species were reco rded.

Of calanoid spec ies: Pseudodiaptomus sp.

(was the most dominant species co nstit uting on averag e more tha n 90% of the tota l co pepods).

ClauSO('(/ /W IlIS spp ..

Parucalanus purvus.

Parucalanus spp, Oitlumu /l W III .

Oithona helogolcuulica.

Corycueus speriosus were the main cyclopoid species record ed only in Al-Shabab lagoon.

Ove r 50 copepod spec ies were recorded in the co llected samples at the offsho re station in Al-Qita Al-Kabera.

Holoplnnktonic gro ups other than copcpods, i.e, tintinnids and rou ters .

constituted 10, I% of the average zooplankton community in Al-Arbaee n and 34% in Al-Shabab lagoon.

The mero planklOlI ic groups recorded in both lagoons were limited : cirri peds larvae and gas tropod s vclige rs we re the most impo rtan t constituting on the average 4% and 30% of the total zoo plankton in Al-Arbaeen and Al -Shabab lagoon s respec tive ly.