Primary productivity in the Eastern Harbour of Alexandria
Abstract
In the »Eastern Harbour« of Alexandria monthly measurements (September 1972 to August 1973) of primary production and phytoplankton sampling were performed.
The Secchi-disc visibility was very low and the calculated thickness of the euphotic layer ranged from 8.47 to 17.3 leters.
The vertical profiles show a decrease with depth in primary production and in all cases production is optimum at the depth of abouth 40—50% of incident light transmission.
The montlhy variations in the optimum production and the crop density at the corresponding depth folow the same trend.
The »production efficiency« of the phytoplankton was higher in the erly phase of the bloom than in the subsequent phases.
In the last few years the standing crop density does not follow previous seasonal trend as result of the increasing eutrophication.
The optimum production ranges from 120 to 676 mg C/m3/12 hr, the gross daily production from 351.4 to 3025 mg C/m2 and the year’s production to 584 g C/m2. This is a high level compared to the general values for the Mediterranean.
