Furthermore, in such ecosystems the effect of anthropogenic nutrient inputs are more evident, and phytoplankton abundance is strongly related to such nutrients, mainly nitrogen compounds. In general, the overall average phytoplankton abundance in the study area was 1.45 × 104 cells l−1, this average being 2–4 times lower than in other Egyptian coastal areas, which can have abnormal algal blooms as a consequence of freshwater discharges and other terrestrial sources of nutrients (El Sherif & Gharib 1994, Abdel-Aziz et al. 2006,

Gharib & Dorgham 2006, Shams El-Din & Abdel Halim 2008). In an earlier study, Dowidar (1988) recorded that the algal bloom in the Egyptian coastal area during the winter was due mainly to the low grazing impact of both zooplankton and phytophagous fish (principally sardines), whereas the spring blooms in the present study selleck products coincided with a 6.00°C increase in water temperature from 18.00°C to 24.00°C and a decline in phosphorus concentrations (0.07 ± 0.05 μM). On the other hand, the phytoplankton abundance decreased in winter as a consequence of relatively low temperatures, even though nutrient levels, especially phosphate levels, were high during this period. However, the increase in phytoplankton abundance in spring was also typically nutrient-limited in both the eastern Mediterranean learn more ( Dorgham et al. 1987) and the whole of that sea (

Kideys et al. 1989, Delgado 1990, Polat & Piner 2002). Phytoplankton reflects water quality through changes in its community structure, patterns of distribution and the proportion of sensitive species. Throughout the study, the phytoplankton in the waters off the Matrouh beaches was dominated by diatoms. Similar findings were reported from most Egyptian coastal waters by Shams El-Din & Dorgham (2007) in Abu-Qir bay, Gharib & Dorgham (2006) in the Western Harbour, and Shams El-Din & Abdel Halim (2008) in the coastal waters of three tourist villages in western Alexandria. The decline in Bacillariophyta abundance could be due to nutrient limitation resulting from the lack of phosphorus

and silicates in the water (reactive heptaminol P and Si concentrations were below or near the detection limit). Diatoms were more frequent (common: 84 species, rare: 36 species) than Pyrrophyta (common: 25 species, rare: 27 species). The bloom of Pseudo-nitzschia spp. was probably a response to higher nutrient concentrations. It is known that, in the Western Harbour and at El-Maadia on the Alexandria coast, such blooms have occurred in response to coastal eutrophication ( Abdel-Aziz et al. 2006, Gharib & Dorgham 2006). This hypothesis is supported by the strong positive correlation between Pseudo-nitzschia spp. and the different nutrient salts. Relatively higher phytoplankton abundances were recorded in the Matrouh lagoon (beaches 4–7), the high numbers of diatoms reflecting the general eutrophic nature of this semi-enclosed basin (Labib 1994).