The phytoplankton of the Suez Canal

Abstract

      A quantitative and qualitative study of the phytoplankton of the Suez Canal was carried out during summer 1969 and winter 1970. Several fine-net plankton hauls, both vertical and horizontal, together with water samples (2 L each) were taken from Port Said, Bitter Lake and Suez Bay in each season. The population is highly diversified. A total of 273 species and varie­ties were identified from the different regions sampled. Most of them are new records for the Suez Canal. Of the species identified, 182 species and varieties representing 58 genera belong to the diatoms and 88 species representing 17 genera belong to the dinoflagellates. The greater number of species (253) were recorded from Port Said region which harbored about 93 percent of the total number, followed by Suez Bay, 181 species (66 percent), while only 149 species (55 percent) were recorded from the Bitter Lake. A total of 133 species and varieties were widespread throughout the canal; only 20 species were confined to the southern end. About 50 percent (90 species) of the species recorded from Suez Bay may be regarded as new to the Red Sea.

       Many of the species recorded in the canal are perennial, occurring both in summer and winter seasons in one or more of the regions sampled. The number of species occuring in winter was, however, predominantly larger than in summer. As for immigration of plankton organisms through the canal, it was found that at least 12 species of Red Sea origin have crossed the canal northward to Port Said; some of them are now more or less established in the Eastern Mediterranean; while only 6 species have immigrat­ed southward to Suez Bay.

       Quantitatively the standing crop was numerically much higher at Port Said than at Suez in both seasons. The standing crops of Port Said and Bitter Lake regions were numerically higher in summer than in winter (maximum 68,810 cells/L in Port Said in July); while in Suez Bay the winter standing crop was almost twice that of the summer. The winter population was dominated by almost the same species throughout the canal including Rhizo­solenia shrubsolei, R. delicatula, R. alata, Guinardia flaccida, Skeletonema costatum and Leptocylindrus danicus. In summer, the population of Port Said was dominated by Bacteriastrum hyalinum, Chactoceros affinis, C. didymus, C. compressus, Skeletonema costatum, Thalassiosira spp., Rhizosolenia shrub­solei, and Guinardia flaccida, while the populations of Bitter Lake and Suez were both dominated by Rhizosolenia alata, Guinardia flaccida, Rhizosolenia delicatula and Thalassionema nitzschioides. In all regions, the diatoms consti­tuted more than 98 percent by number of the standing crop. The distribution of phytoplankton species in winter and summer in the regions sampled is related to the current regime in the canal.