DISTRIBUTION OF PHYTOPLANKTON INFRONT OF ROSETTA NILE BRANCH (EGYPT)

DISTRIBUTION OF PHYTOPLANKTON INFRONT OF ROSETTA
NILE BRANCH (EGYPT)
AMIN A. SAMAAN, RAMSES R. ABDALLA

AND WAGDY L. GERGIS

Institute of Oceanography and Fisheries, Alexandria.

ABSTRACT
Quantitative and qualitative estimations. of the
phytoplankton community infront of Rosetta Nlle Branch
(Egypt) have been carried out for four seasons. The release
of fresh water in the winter increased the numbers of
phytoplankton to an average of 94990 cell/l. The summer
sustained the lowest standing crop (265 cell/l), due. to
the development of thermal stratification and nutrlent
depletion from the photic zone. The community was composed
mainly of diatoms which constituted numerlcally about 99.7%
of the total population. Among the diatoms recorde~. o~lY
8 species appeared as dominant forms. The estimated dlversl:Y
was reversely related to the degree of daminance of cert~ln
species rather than to the number of the total specles
contributing the standing crop. The average annual va~ue
of the phytoplankton standing crop along the Rosetta sectlon
amounted to 27054 cell/l. This relatively high value was
due to the freash water discharged into the area.