Temperature fluctuations do not have an important effect
on species composition, while salinity is the main physical
parameter that can be attributed to the plankton diversity
and acts as a limiting factorthatinfluencesthe distribution of
plankton community as reported by Sridhar et al.
(2006). Large salinity oscillations in the harbour were
recorded spatially and temporally, ranging from 22.7 PSU
(St. 2) to 38.6 PSU (St. 7). Values were noticeably high in
winter and autumn but drops in spring and causing a stress
condition and a resultant loss of biodiversity. The marked
reduction in salinity values may be due to the huge quantities
of discharged water, or may be due to the disposal of ballast
water. This appeared by the lowest average salinity values
recorded at stations 1 and 2, both under direct wastewaters
influence, while the highest average salinity values were
generally recorded at stations 5 and 10. In the long term,
average salinity decreased from 37.0 PSU in 1985 (Nessim and
Tadros, 1986)to 35.3 PSUin 1999—2000 (Dorgham et al., 2004),
and still as the latter average value during the present study.