Ecohydrographic constraints on biodiversity and distribution of phytoplankton and zooplankton in coral reefs of the Red Sea, Saudi Arabia

Abstract

An integral concept of ecological research is the constraint of biodiversity along latitudinal and environmental gradients. The Red Sea features a natural example of a latitudinal gradient of salinity, temperature and nutrient richness. Coral reefs along the Red Sea coasts are supported with allochthonous resources such as oceanic and neritic phytoplankton and zooplankton; however, relatively little is known about how the ecohydrography correlates with plankton biodiversity and abundance. In this article we present the biodiversity of phytoplankton and zooplankton in Red Sea coral reefs. Oceanographic data (temperature, salinity), water samples for nutrient analysis, particulate organic matter, phytoplankton and zooplankton, the latter with special reference to Copepoda (Crustacea), were collected at nine coral reefs over ~1500 km distance along the Red Sea coast of Saudi Arabia. The trophic state of ambient waters [as indicated by chlorophyll a (Chl a)] changed from strong oligotrophy in the north to mesotrophy in the south and was associated with increasing biomasses of Bacillariophyceae, picoeukaryotes and Synechococcus as indicated by pigment fingerprinting (CHEMTAX) and flow cytometry. Net‐phytoplankton microscopy revealed a Trichodesmium erythraeum (Cyanobacteria) bloom north of the Farasan Islands. Several potentially harmful algae, including Dinophysis miles and Gonyaulax spinifera (Dinophyceae), were encountered in larger numbers in the vicinity of the aquaculture facilities at Al Lith. Changes in zooplankton abundance were mainly correlated to the phytoplankton biomass following the latitudinal gradient. The largest zooplankton abundance was observed at the Farasan Archipelago, despite high abundances of copepodites, veligers (Gastropoda larvae) and Chaetognatha at Al Lith. Although the community composition changed over latitude, biodiversity indices of phytoplankton and zooplankton did not exhibit a systematic pattern. As this study constitutes the first current account of the plankton biodiversity in Red Sea coral reefs at a large spatial scale, the results will be informative for ecosystem‐based management along the coastline of Saudi Arabia.

Iron Deficiency in Seagrasses and Macroalgae in the Red Sea Is Unrelated to Latitude and Physiological Performance

“…On the other hand, the lack of a latitudinal pattern described here for seagrasses and macroalgae aligns with the results for productivity of phytoplankton obtained in several research cruises in the Red Sea (Qurban et al, 2017), which showed no clear latitudinal patterns. Hence, whereas the South to North oligotrophication of the Red Sea affects some species of benthic invertebrates on corals reefs (Sawall et al, 2015;Al-Aidaroos et al, 2016) and to a certain extent pelagic phytoplankton Chl a concentrations (Raitsos et al, 2013;Kürten et al, 2015), it is not reflected in iron concentration, Chl a concentration or physiological performance of Red Sea macrophytes.…”

“…This nutrient gradient is associated with a gradual decrease of Chl a concentration in phytoplankton from south to north of the Red Sea (Raitsos et al, 2013;Kürten et al, 2015). This gradient is especially prominent during the summer months and more diffuse during the winter, when wind-driven watermixing replenishes the nutrients in the sea surface in the northern Red Sea (Sofianos and Johns, 2003).…”

“…With a few exceptions (Almahasheer et al, 2016a,b,c), corals and phytoplankton are the main focus of research on primary producers in the Red Sea (Cantin et al, 2010;Ziegler et al, 2014;Kürten et al, 2015;Sawall et al, 2015;Roik et al, 2016;Qurban et al, 2017, among others). However, other important and uncharismatic habitat-forming macrophytes, such as seagrasses and macroalgae within coral reefs , are common but poorly studied in the Red Sea.…”

Physical Mechanisms Routing Nutrients in the Central Red Sea

“…Numerical simulations presented by Zhan et al () indicated that that eddies may considerably impact coastal current variability and cause substantial vertical transport at the coastal boundary due to the interaction with the boundary. The impact of eddies on coral reef communities has been proposed by Robitzch et al (), who infer that eddies may substantially contribute to the dispersal of coral larvae, and by Kürten et al (), who showed that coral reef biota assimilate macronutrients from the oceanic catchment in the Red Sea. As has been observed in the open ocean (Gaube et al, ; McGillicuddy et al, ; Rodríguez et al, ), eddies may appreciably impact primary productivity of the Red Sea.…”

Checklist of phytoplankton species in the Egyptian Red Sea Coast of Hurghada

“…Phytoplankton community structure and species composition in the eastern coast of the Red Sea have been investigated through many studies (Shaikh et al 1986;Khalil and Ibrahim 1988;Touliabah et al 2010;Kürten et al 2015;Devassy et al 2016Devassy et al , 2017. Recently, Ismael (2015) reviewed the phytoplankton and primary productivity status in the Red Sea proper, Suez and Aqaba Gulfs since Halim (1969) and listed 389 species and varieties in the entire Red Sea.…”