Mohsen M. El-Sherbiny

High Mortality of Red Sea Zooplankton under Ambient Solar Radiation

High solar radiation along with extreme transparency leads to high penetration of solar radiation in the Red Sea, potentially harmful to biota inhabiting the upper water column, including zooplankton. Here we show, based on experimental assessments of solar radiation dose-mortality curves on eight common taxa, the mortality of zooplankton in the oligotrophic waters of the Red Sea to increase steeply with ambient levels of solar radiation in the Red Sea. Responses curves linking solar radiation doses with zooplankton mortality were evaluated by exposing organisms, enclosed in quartz bottles, allowing all the wavelengths of solar radiation to penetrate, to five different levels of ambient solar radiation (100%, 21.6%, 7.2%, 3.2% and 0% of solar radiation). The maximum mortality rates under ambient solar radiation levels averaged (±standard error of the mean, SEM) 18.4±5.8% h−1, five-fold greater than the average mortality in the dark for the eight taxa tested. The UV-B radiation required for mortality rates to reach ½of maximum values averaged (±SEM) 12±5.6 h−1% of incident UVB radiation, equivalent to the UV-B dose at 19.2±2.7 m depth in open coastal Red Sea waters. These results confirm that Red Sea zooplankton are highly vulnerable to ambient solar radiation, as a consequence of the combination of high incident radiation and high water transparency allowing deep penetration of damaging UV-B radiation. These results provide evidence of the significance of ambient solar radiation levels as a stressor of marine zooplankton communities in tropical, oligotrophic waters. Because the oligotrophic ocean extends across 70% of the ocean surface, solar radiation can be a globally-significant stressor for the ocean ecosystem, by constraining zooplankton use of the upper levels of the water column and, therefore, the efficiency of food transfer up the food web in the oligotrophic ocean.

Latitudinal environmental gradients and diel variability influence abundance and community structure of Chaetognatha in Red Sea coral reefs

The Red Sea has been recognized as a unique region to study the effects of ecohydrographic gradients at a basin-wide scale. Its gradient of temperature and salinity relates to the Indian Ocean monsoon and associated wind-driven transport of fertile and plankton-rich water in winter from the Gulf of Aden into the Red Sea. Subsequent evaporation and thermohaline circulation increase the salinity and decrease water temperatures toward the North. Compared with other ocean systems, however, relatively little is known about the zooplankton biodiversity of the Red Sea and how this relates to Red Sea latitudinal gradients. Among the most abundant zooplankton taxa are Chaetognatha, which play an important role as secondary consumers in most marine food webs. Since Chaetognatha are sensitive to changes in temperature and salinity, we surmised latitudinal changes in their biodiversity, community structure and diel variability along the coast of Saudi Arabia. Samples were collected at nine coral reefs spanning approximately 1500 km, from the Gulf of Aqaba in the northern Red Sea to the Farasan Archipelago in the southern Red Sea. Thirteen Chaetognatha species belonging to two families (Sagittidae and Krohnittidae) were identified. Latitudinal environmental changes and availability of prey (i.e. Copepoda, Crustacea) altered Chaetognatha density and distribution. The cosmopolitan epiplanktonic Flaccisagitta enflata (38.1%) dominated the Chaetognatha community, and its abundance gradually decreased from South to North. Notable were two mesopelagic species (Decipisagitta decipiens and Caecosagitta macrocephala) in the near-reef surface mixed layers at some sites. This was related to wind-induced upwelling of deep water into the coral reefs providing evidence of trophic oceanic subsidies. Most Sagittidae occurred in higher abundances at night, whereas Krohnittidae were more present during the day. Chaetognatha with developing (stage II) or mature ovaries (stage III) were more active at night, demonstrating stage-specific diel vertical migration as a potential predator avoidance strategy.

Strong Sensitivity of Red Sea Zooplankton to UV-B Radiation

The impacts of UV-B radiation to Red Sea coastal zooplankton was assessed experimentally at the time (May/June) of peak UV-B radiation, using the most abundant zooplankton species in the community (eight copepod genera, a cladoceran, an ostracod, a cumacean, and two meroplankton, including crab zoeae and megalopa). Mortality rates increased greatly in the presence of ambient UV-B radiation for all species tested except for Labidocera, Macrosetella, and the crab megalopa larvae. Mortality rates declined, on average, threefold when UV-B radiation was removed. These results provide evidence that Red Sea zooplankton are highly vulnerable to ambient levels of UV-B radiation.

First record and redescription of Macandrewella cochinensis Gopalakrishnan, 1973 (Copepoda, Scolecitrichidae) from the Red Sea, with notes on swarm formation

Abstract During a study of the epipelagic zooplankton carried out near the fringing reef around Sharm El-Sheikh area, in the northern Red Sea, female and male specimens of the poorly known calanoid copepod Macandrewella cochinensis Gopalakrishnan, 1973 were collected. This is the first record of species occurrence in the Red Sea. Macandrewella cochinensis was previously known only from the offshore water of Cochin, south west of India. The Red Sea specimens are described in details herein to allow their comparison with the specimens from the type locality, because original description of M. cochinensis is incomplete and causes some taxonomic confusion. The most important characters that may have been overlooked in the original description are: shape of projections of the female distolateral prosomal borders, details of morphology of the asymmetrical female genital double-somite and presence of leg 5 in female.

Biodiversity of the community associated with Pocillopora verrucosa (Scleractinia: Pocilloporidae) in the Red Sea

The symbiotic community associated with a scleractinian coral Pocillopora verrucosa has been studied along the Red Sea coast of Saudi Arabia from Al Wajh to the entrance of the Gulf of Aqaba. Forty colonies have been sampled from 2- to 15-m depth in 2 areas, southern and northern. Thirty-six associated species were found, including 15 symbionts and 21 species with uncertain status (SUS). The number of recorded symbiotic species was close to the statistically expected value, while SUS were rare and did not reach the value expected from the Chao 2 model. Species number and abundance positively correlated with the colony volume. Mean abundance of all species and symbionts and the number of SUS per covariate colony volume were higher in the northern area than in the southern area. This may be related to a higher habitat diversity of the surrounding reefs and to the presence of colonies with partially dead tissues in the north. These two factors have a weak impact on symbionts, but strongly affect SUS. The diversity of the pocilloporid-associated communities range from 36 to 127 species along the Indo-Pacific and Tropical East Pacific, with 9 to 19 of them being symbionts. The total species diversity varies owing to the SUS number, while the core of true symbionts includes much fewer species and is less variable. The diversity of Pocillopora symbionts in the Saudi Arabian coast (15 species) is among the highest for the studied areas in the Indo-Pacific.

Editorial: Red Sea biodiversity

The Red Sea is one of the global hotspots for biodiversity and houses a very high endemism rate compared to adjacent marine regions (DiBattista et al. 2016). One of the reasons for this high endemism rate may be the Red Sea being partially isolated by the Gulf of Aden strait of Bab al-Mandab in the south, where environmental conditions like temperature and salinity, as well as shallow depths, limit the spreading of species between the Red Sea and the Indian Ocean (Kemp 2000). For the connection with the Mediterranean through the Suez Canal in the north, a northward, unidirectional spreading of species, the so-called Lessepsian migration, was recorded (Por 2012). Moreover, the Red Sea has long been known to have a warm and salty deep sea with nearly isothermal and isohaline water (around 22°C and 40‰) in large parts of the deep sea (Neumann and McGill 1961), showing a highly specialised and partly endemic fauna. The high diversity of Red Sea species is partially caused by its comparatively high coverage of coral reefs, with more than 16,000 km (Roberts et al. 2002). With regard to this background and due to the fact that an estimation of Red Sea species numbers is still impossible due to the lack of studies, it is a very interesting area for science concerning the exploration of its biodiversity. With this regard, the King Abdulaziz University in Jeddah, Saudi Arabia (KAU) and the Senckenberg Research Institute in Frankfurt am Main, Germany (SRI) started to conduct a scientific research programme in 2011. The main goal of this Red Sea Biodiversity Project is to assess the marine biodiversity of the SaudiArabian coast and deep water of the Red Sea and to build up a reference collection at the King Abdulaziz Marine Museum (KAUMM) and at SRI. Since 2011, species of all marine animal groups have been collected, identified, preserved and catalogued for the reference collections of the KAUMM and SRI. One of the outcomes of these extensive surveys was the discovery of many species being new to the Red Sea or even new to science. As another goal of this research cooperation is the description and publication of the latter, we were looking for an opportunity to publish many of these findings together in one volume, also inviting scientists not (or not yet) involved in the described project to contribute with studies covering a broad range of topics concerning marine biodiversity research, including works on taxonomy and systematics, ecology, ecosystem health and management, long-term trends, neobiota and other related subjects. This endeavour has now come true with this special issue in the journal Marine Biodiversity.

First report of the presence of Acartiabispinosa Carl, 1907 (Copepoda, Calanoida) in a semi-enclosed Bay (Sharm El-Maya), northern Red Sea with some notes on its seasonal variation in abundance and body size.

Abstract The calanoid copepod, Acartia bispinosa Carl, 1907, is reported for the first time in the Red Sea, where it is found to be an important copepod in the mesozooplankton community structure of the Sharm El-Maya Bay. Female and male are fully redescribed and illustrated of as the mouthparts of this species have never previously been described and figured. Acartia bispinosa was collected in the plankton samples throughout the year and showed two peaks of abundance, a pronounced one in April (4234 individuals m-3), and second smaller peak during November (1784 individuals m-3). The average total length of females varied between 1.32 and 1.53 mm at the end of June and January respectively. For males, the average total length fluctuated between 1.07 and 1.16 mm at end of June and March respectively. Temperature showed an inverse relationship with the body length (P > 0.001) and seemed to be one of the prime factors affecting the body length of both sexes.

A new species of Calanopia (Copepoda, Calanoida, Pontellidae) from the plankton of the central Red Sea

Calanopia tulina sp. nov., a new pontellid copepod, is described from plankton samples collected in Saudi Arabian waters of the Red Sea. The female of the new species differs from other congeners in having the genital operculum located posteroventrally on the genital compound somite and by a slightly asymmetrical leg 5, in which the right leg is slightly shorter than the left one. The male is distinguished by: (1) the presence of a distinct notch on the medial margin of the right prosomal corner; (2) the structure of leg 5, in which the second exopodal segment of the left leg has one medially directed spine and two large laterally directed and curved serrated spines distally; and (3) the first exopodal segment of the right leg has a very small rounded-tip thumb located at the mid-length. The new species is most similar to Calanopia media described from the Red Sea. The presence of the new species in night collection may be due to the diel vertical migration behavior that is known for some species of this genus.

Ontogenetic Changes in Vulnerability of the Prawn Fenneropenaeus indicus to UV-B Radiation Help Explain Ontogenetic Habitat Shifts

The Indian Ocean white prawn (Fenneropenaeus indicus H. Milne Edwards, 1837) is distributed across the Indian Ocean, from southern Africa to northern Australia and the Red Sea, and is also present in all of South-East Asia, where F. indicus is a major commercial fishery species. F. indicus has been domesticated for aquaculture and is extensively cultured in farms throughout South-East Asia, India, the Middle East, Saudi Arabia, and eastern Africa (Ling et al. 1999). F. indicus is a non-burrowing prawn species preferring a sandy or muddy bottom, and although active at both day and night, it has been shown to display clear daily rhythms in activity, being less active at night (Natarajan 1989). F. indicus has a complex ontogenetic developmental cycle involving 12 stages distributed in three planktonic larval forms (6 nauplii stages, N-1 to N-6; 3 zoea stages, Z-1 to Z-3; and 3 mysis stages, M-1 to M-3). F. indicus develops from hatching to the post larva (PL) stage over 10 to 18 days in natural conditions (Muthu et al. 1978) and 13 to 14 days under hatchery conditions (Silas et al 1985). As many decapods, F. indicus also has a tri-phasic life cycle (Pitman and McAlpine 2003). The prawn matures and breeds mostly in offshore coastal waters, and the larvae are advected in the neuston until recruiting to their estuarine habitats (Forbes and Cyrus 1991). The PL grows in coastal estuaries, backwaters, or lagoons with a particular preference for mangrove habitats (De Freitas 1986; Mohan and Siddeek 1996; Ronnback et al. 2002), where they spend the juvenile and sub-adult stages, before migrating to open coastal habitats for breeding. Larvae are often present in the neuston, except in the period of maximum solar radiation. Seasonal studies off Kochi (Arabian Sea, India) showed that F. indicus larvae are rare in the plankton from May to September (George 1962; Rao 1964). Whereas late larval stages, PL, and juveniles inhabit shaded environments, such as mangrove creeks, the larvae are pelagic and can be subjected to high irradiance in the water column in tropical and subtropical regions. Moreover, this species is reared in shallow aquaculture ponds and floating cages (Walford and Lam 1987), which can also receive high solar radiation in tropical and subtropical regions. High light intensities have been reported to be detrimental for the survival of larval stages of penaeid prawn, which are reared under dim light conditions to increase spawning and early survival success in aquaculture (Wurts and Stickney 1984). The shaded habitat of the PL, in mangrove creeks, the low abundance of planktonic larvae during the months of peak solar radiation, and the light-sensitivity of early life stages all point at a vulnerability of F. indicus larvae to high solar radiation and particularly ultraviolet-B (UV-B) radiation as the most damaging component of solar radiation (Hader et al. 2007; Hansson and Hylander 2009). Because of its commercial importance, the physiology, growth, and behavior of F. indicus have been extensively studied (Kutty et al. 1971; Colvin 1976; Emmerson 1984). The resistance of PL to changes in environmental conditions, Communicated by Charles Simenstad