Lev Fishelson

Ecology and distribution of the benthic fauna in the shallow waters of the Red Sea

Approximately 500 animal species and plants are listed as being the most typical for the infratidal and shallow subtidal benthic fauna of the Red Sea. Most of them are divided into communities typical for various soft and hard substrata, and at different water depths. The oceanographic conditions and the development of several of the communities are discussed in general terms.

Ecology of coral reefs in the Gulf of Aqaba (Red Sea) influenced by pollution

Summary1.This paper summarizes observations performed during 1966, 1968, and 1972, on coral reef flats 7 km south of Eliat (Gulf of Aqaba, Red Sea). The aim of this research was to describe the change in numbers of living coral colonies found on the coral tables in connection with pollution occuring in this habitat. A transect technique, developed by Loya and Slobodkin (1971) was used in this research.2.In each of the three years, 19 ten metre transects were performed in various directions, on the same coral tables.3.In 1966, 541 living coral colonies were counted in a total of 190 m of transects. At the identical place, this number had decreased to only 195, in 1972. The decrease in corals was found to be accompanied by a prominant increase in algae growth, that expend and develop, thus covering the coral specimens.4.Especially sensitive to algal development are the branching micropolypal, coral species, that are the representatives of the genera Acropora, Seriatopora, and Stylophora. Of the above three genera counted in 1966, only 10 out of 192 colonies were found intact, in 1972.5.The high mortality of corals in this locality occured during the years in which an oil terminal plus a mineral and phosphate loading harbour were developed at Eilat.6.The frequent oil spills, together with the phosphate dust that reaches the sea, seem to be the factors that cause eutrophication in the shallow lagoon waters of the coral region, and thus the development of algae on the coast of corals is stimulated.

Ecological and biological phenomena influencing coral-species composition on the reef tables at Eilat (Gulf of Aqaba, Red Sea)

Observations performed on coral colonies damaged during a very low tide on the shallow-water reef tables at Eilat (Red Sea), showed that most colonies are able to regenerate if parts of the living tissue remain intact on the skeletons. Brain-like corals, such asFavia favus andPlatygyra lamellina, were found to be more resistant to dessication than the delicate bush-like forms. It was also observed that the exposed skeletons of corals were immediately covered by a successive group of algae with a rich invertebrate epifauna among them. It is postulated that unpredicted extreme low water, occurring once in several years, could be the factor that prevents crowding on the reef tables, thus keeping high the level of coralspecies diversity.

Marine molluscs and fish as biomarkers of pollution stress in littoral regions of the Red Sea, Mediterranean Sea and North Sea

Abstract The intensive development of industry and urban structures along the seashores of the world, as well as the immense increase in marine transportation and other activities, has resulted in the deposition of thousands of new chemicals and organic compounds, endangering the existence of organisms and ecosystems. The conventional single biomarker methods used in ecological assessment studies cannot provide an adequate base for environmental health assessment, management and sustainability planning. The present study uses a set of novel biochemical, physiological, cytogenetic and morphological methods to characterize the state of health of selected molluscs and fish along the shores of the German North Sea, as well as the Israeli Mediterranean and Red Sea. The methods include measurement of activity of multixenobiotic resistance-mediated transporter (MXRtr) and the system of active transport of organic anions (SATOA) as indicators of antixenobiotic defence; glutathione S-transferase (GST) activity as an indicator of biotransformation of xenobiotics; DNA unwinding as a marker of genotoxicity; micronucleus test for clastogenicity; levels of phagocytosis for immunotoxicity; cholinesterase (ChE) activity and level of catecholamines as indicators of neurotoxicity; permeability of external epithelia to anionic hydrophilic probe, intralysosomal accumulation of cationic amphiphilic probe and activity of non-specific esterases as indicators of cell/tissue viability. Complete histopathological examination was used for diagnostics of environmental pathology. The obtained data show that the activity of the defensive pumps, MXRtr and SATOA in the studied organisms was significantly higher in the surface epithelia of molluscs from a polluted site than that of the same species from control, unpolluted stations, providing clear evidence of response to stress. Enhanced frequency of DNA lesions (alkaline and acidic DNA unwinding) and micronucleus-containing cells was significantly higher in samples from polluted sites in comparison to those from the clean sites that exhibited genotoxic and clastogenic activity of the pollutants. In all the studied molluscs a negative correlation was found between the MXRtr levels of activity and the frequency of micronucleus-containing hemocytes. The expression of this was in accordance with the level of pollution. The complete histopathological examination demonstrates significantly higher frequencies of pathological alterations in organs of animals from polluted sites. A strong negative correlation was found between the frequency of these alterations and MXRtr activity in the same specimens. In addition to these parameters, a decrease in the viability was noted in molluscs from the polluted sites, but ChE activities remained similar at most sites. The methods applied in our study unmasked numerous early cryptic responses and negative alterations of health in populations of marine biota sampled from the polluted sites. This demonstrates that genotoxic, clastogenic and pathogenic xenobiotics are present and act in the studied sites and this knowledge can provide a reliable base for consideration for sustainable development.

Feeding ecology of surgeonfishes (Acanthuridae) in the northern Red Sea, with particular reference to Acanthurus nigrofuscus (Forsskål)

Abstract Three surgeonfishes (Teleostei:Acanthuridae), inhabiting Red Sea reefs near Eilat, Israel, are similar in size and overlap to varying degrees in use of habitat. They differ in diel cycles of feeding behavior, specifics of habitat use and general strategies used to process food. Ctenochaetus striatus (Quoy et Gaimard) spends ≈30% of its time in active feeding on reefs and sandy substrata within its weakly defended home range, ingests both algae and large quantities of inorganic grit, triturates foods in a gizzard-like stomach, fails to retain a bolus of food in the posterior intestine overnight and generally engages in more complex social interactions than do the other species. In contrast, Acanthurus nigrofuscus (Forsskal) and Zebrasoma xanthurum (Blyth) feed 55–70% of the time, do not ingest large quantities of grit, lack the gizzard-like stomach, retain a bolus of food overnight in the posterior gut and exhibit social systems much different than C. striatus. A. nigrofuscus contrasts with the other species by feeding in the shallows next to shore, rather than on fringing reefs, and by forming much larger feeding groups. Groups of A. nigrofuscus feeding at two sites differed in group size, diel cycles of feeding activity and total feeding time·day −1 . These differences do not appear to correlate with differences in food availability or selectivity in feeding. They do correlate with distance from shelter to feeding sites and degree of exposure on the feeding grounds. Body condition (robustness) of A. nigrofuscus declines during summer and autumn despite active feeding, indicating that apparent maximization of feeding time may be insufficient to meet energy and nutrient demands during all seasons. Local differences in physical and biotic conditions on reefs probably serve as a powerful selective pressure for behavioral and ecological plasticity in reef fishes with vagile larvae.

Littoral fauna of the Red Sea: the population of non-scleractinian anthozoans of shallow waters of the Red Sea (Eilat)

Approximately 22 species of sea anemones and 20 species of alcyonarians were found on the reef fringing the shallow water at Eilat (Gulf of Aqaba) and other localities along the Red Sea coast of the Sinai Peninsula. Investigations showed that these 2 groups of non-scleractinian coelenterates from (on different substrates) well identified colonies, part of them inhabiting sandy bottoms, other groups growing on the reef surface. Observations lead to the conclusion that several of the sea anemones and alcyonarians can act, under certain conditions, as factors limiting the development of hermatypic corals. In some areas, several species of the 2 groups of animals are found together with their symbiotic partners, such as fishes and crustaceans.

Behaviour and ecology of a population of Abudefduf saxatilis (Pomacentridae, Teleostei) at Eilat (Red Sea)

Summary This study summarizes investigations on a population of the Sergant Major, Abudefduf saxatilis (Pomacentridae), performed along the coral reef of Eilat, Gulf of Aqaba. Emphasis was placed on the schooling behaviour and reproduction, especially on the analysis of the males action inventory, their frequencies and signicance. 1. Ab. saxatilis inhabiting shallow waters, exhibits long-term reproduction during the summer months (April to August), the individual spending the night separately in coral crevices and gathering after sunrise in groups to feed on plankton. 2. After feeding, the mature fish form a school and start to swim along the coral wall, headed by mature males searching for sites for nesting colonies. Consequently, this appetitive behaviour brings about the establishment of breeding colonies of eight to twenty mature males. 3. Ripe females attracted by special acts of the male enter individual territories and spawn. The entrance of such receptive females changes the action patterns of the male, stimulating the occurrence of the behaviour that leads to fertilization and spawn care. 4. The male spawns with several females consecutively and with each new female the reproductive behavioural pattern is partly renewed. 5. The frequency and correlation analysis of action bonds was found to be strongly connected to the strength of the producing stimulus. 6. During the winter months the schooling disappears and the fish are found in small groups in the littoral all along the reef.

Food habits and prey selection of three species of groupers from the genus Cephalopholis (Serranidae: Teleostei)

SynopsisThis paper describes a study performed in the Gulf of Aqaba on food selectivity and hunting behaviour of three species of sympatric fish from the genusCephalopholis. These fishes occur in the shallow-water coral habitats of the Red Sea and feed on fishes and invertebrates. Of these,C. argus andC. miniata prefer selected fish species (95 and 86% of their diet respectively), whereasC. hemistiktos consumes more invertebrates (36%) and is less selective with respect to fish species. All three species employ various techniques to catch their prey and in situations where their elected food is absent they readily switch to substitute prey species.

Ecology of the northern Red Sea crinoids and their Epi- and Endozoic fauna

Fourteen crinoid species are found along the coral reefs of the northern Red Sea that form aggregations of different species at various depths. The shallowest aggregation consists partly of Lamprometra klunzingeri and Capillaster multiradiatus, occurring subtidal to a depth of 2 to 5 m. Of this group, Heterometra savignii inhabits depths down to 12–15 m. Further down, another group of 10-armed crinoids occurs, dominated by Decametra chadwicki and Oligometra serripinna. The deepest aggregation of crinoids occurs at 45 m; its most common members are Colobometra arabica and Comaster distinctus. Feeding on micro- and nanoplankton, shallow-water crinoids show a circadian activity rhythm; in deeper aggregations (10 to 12 m), this behaviour changes with decreasing illumination, to a diurnal activity rhythm. The symbiotic animals living on crinoids comprise 27 taxons, among them Copepoda (6 species), Mollusca (2 species), Polychaeta (11 species, especially Myzostomida); Ophiurida (1 species), Crustacea, Decapoda (6 species); and the clingfish Lepadichthys lineatus. These symbiotic animals form food webs at various depths, according to the distribution of their crinoid host. The occurrence of Indo-West Pacific and Mediterranean commensals on the same crinoid in the Gulf of Aqaba is of special interest.

Food composition and feeding behavior of shallow-water crinoids at Eilat (Red Sea)

The food of 3 feather-stars, Lamprometra klunzingeriHartlaub, 1890), Heterometra savignii (J. Müller, 1841) and Capillaster multiradiatus (Linnaeus, 1758), from the shallow water of Eilat (Red Sea) was found to be composed of planktonic and semi-benthalic organisms with a strong dominance of zooplankton. Monthly analyses of stomach contents showed seasonal changes in the participation of various systematic units in the diet. Food-comprising organisms were found to be selected according to size, and those measuring up to 400 μ formed 90% of the diet.