Short - Term Variations in the Abundance of Zooplankton near Coral Reef and Open Water in the Northern Part of Gulf of Aqaba in the Red Sea

Short - Term Variations in the Abundance of Zooplankton near Coral Reef and Open Water in the Northern Part of Gulf of Aqaba in the Red Sea

Raid M Rizik The processes taking place when open-oceanic waters bearing pelagic organisms encounter shallow coastal habitats are virtually unknown. Such processes could potentially be a principal trophic path for benthic (coral-reef) and epibenthic (fish) communities, particularly in oligotrophic regions. This proposed to investigate the processes involved in the coupling between the Open Ocean and coastal habitats in the Gulf of Aqaba. Specifically, we propose to test hypotheses relating high-freguency (minutes, hours, days) fluctuations in zooplankton abundance, ocean currents, animal behavior, and trophic interactions on an ecosystem level. Zooplankton abundance and grazing in short term variation (minutes to weeks) were measured along the Gulf of Aqaba reef and at a near-by, open water site during October 10 and December 2.1999. Role of currents, behavior and localized predation of zooplankton in the generation of the observed variations were also studied. In our experiments zooplankton samples were obtained by filtering the pumped water through 100 m mesh net from the reef and open water sites to compare the temporal variations in the abundance of zooplankton and behavior at the tow above sites. Also two current meters equipped with a temperature sensor were deployed at the reef and away sites to record the average speed, direction and temperature of the current. Our results clearly show that: Zooplankton were less abundant at the reef, compared with the away site because of the zooplankton predation at the reef from the corals and fish. A general increase in zooplankton abundance at the two study sites in the diurnal (during day time )and nocturnal (during night time)samples, from the start of our sampling to its ends coincided with the ennsuing fall mixing and seasonal eutrophication in the northern Gulf of Aqaba. A covariation of zooplankton abundance between the two sites on the scales of both the entire period and on hourly samples within a days. A bundance of zooplankton in a diel cycle was seen at the two sites, with nearly a doubling of zooplankton biomass during night. No correlation was found between the abundance of zooplankton and the component of the currents because of the behavior primarily active swimming of zooplankton in the vertical water column. This study supports earlier reports on the important of zooplankton advection to the nutrition of coral reefs. Grazing at the reef together with physical advection seems to affect temporal variations of the zooplankton at our study sites. Raid M Rizik Supervisors Prof. Ziad Abdeen Prof. Ali Z. Abu Zuhri January 2001    Zajel / An-Najah National University