Oceanologia (Mar 2003)
Ecological indices as a tool for assessing pollution in El-Dekhaila Harbour (Alexandria, Egypt)
Abstract
Statistical analyses of data concerning the phytoplankton standing crop andbiomass were applied as a tool for assessing pollution in El-Dekhaila Harbour.Univariate and multivariate analysis showed a succession of three clustersassociated with salinity and temperature variations. The first and thirdclusters comprised mainly diatoms and dinoflagellates. The second cluster,richer in species, was dominated by brackish water cyanophytes, chlorophytesand euglenophytes. The diversity index ranged from 0.08 to 2.41. A highdiversity was associated with high evenness, reflecting the multidominancepattern of cluster (2). On the other hand, multiple correlations betweensalinity and standing crop, richness and evenness, were negative andsignificant, but positive with the diversity index. The ABC curve showed thatthe k-dominance curve for numerical abundance extends above that for thebiomass when clusters 1 and 3 are dominant. Both curves coincide more orless for another segment of the curve but when cluster 2 becomes dominantthe numerical abundance curve runs below that of the biomass. Sucha pattern may indicate unpolluted or moderate to heavily polluted conditionsin El-Dekhaila Harbour. The present study reveals that the combination of univariate andmultivariate analysis with the ABC curve provides a promising tool forthe characterization of phytoplankton dynamics under stress conditions.On the other hand, the phytoplankton community in El-Dekhaila Harbouris stressed not by the inflow of brackish water but rather by the inflow ofsea water. This is indicated by the higher diversity and evenness, and bythe ABC curve during the dominance of cluster (2).
