effect of sewage discharge on phytoplankton diversity in east of Alexandria coastal waters [Egypt]

ABSTRACT

Quantitative estimation of phytoplankton was carried out along the Eastern coast of Alexandria [Egypt] for three seasons, during 1991. The samples were collected from 7 sectors prependicular to the coast line from Kayet Bey to Assafra. Each sector included 3 stations situated at average water depths of 5,20 and 30 m respectively. The phytoplankton comprised 239 species included in 7 classes. the community was composed mainly of diatoms [60.3% of the total population]. The highest standing crop wad recorded in the Eastern Harbour [E.H] [30.8 x 10[3] units.1[-1]] and the lowest at Asafra [15.1 x 10[3] units. L[-1]]. The summer sustained the highest standing crop. The estimated diversity was inversely proportional to the degree of dominance of certain species and lineary related to the number of species contributing the standing crop with a simple regression equations. Multiple regression analysis illustrates also equation models for diversity in both the surface and subsrface water. Diversity index confirms a considerable improvement in the water quality of the investigated area after the construction of the new sewage system in May, 1988, which transferred the waste water discharge away from Alexandria beaches. It averaged 1.98 nats at the inshore stations and this was accompanied with a drop in the concentration of nutrients by about 36% than of the previous records in the same area, 15 years ago