Nutrient enrichment caused by in situ fish farms at Eilat, Red Sea is detrimental to coral reproduction.

Recent studies report conflicting results concerning the effects of eutrophication on coral reproduction. The present study examines reproductive effort in the brooding coral Stylophora pistillata exposed to chronic eutrophication caused by in situ fish cages (FC) in the northern Gulf of Eilat (Aqaba). Histological studies of 20 S. pistillata colonies transplanted to each of two study sites, one close to the nutrient enriched FC site and the other at a reference site (IUI), 8 km southwest of the FC site, show that, overall, corals from the FC site have a significantly higher percentage of polyps containing oocytes and testes than corals from the IUI site. However, average oocyte size and the percentage of oocytes reaching the size at which fertilization occurs (i.e., >200 microm) were both significantly greater in colonies at the IUI site compared to the FC site. As the reproductive season progressed, colonies at the IUI site exhibited a decrease in the percentage of polyps containing oocytes, concomitant with an increase in the number of polyps containing planulae, indicating successful development of oocytes into planulae. In contrast, in colonies at the FC site oocyte numbers were greatest at the end of the reproductive season, and overall, numbers of planulae were significantly lower compared with the IUI colonies, suggesting relative failure of oocyte maturation, fertilization and ensuing larval development. The significantly higher lipid content found during the reproduction season in IUI colonies compared with FC colonies corroborates this assertion. This data strongly suggest that nutrients released from the fish farms have adverse effects on successful production of larvae of S. pistillata. In view of the recent severe deterioration of the coral reefs of Eilat and their present critical state of health, the only chance for their renewal is the use of immediate, prudent and rational protection measures against all man-made perturbations.

[1]  T. Patarnello,et al.  Effects of pollution on heterozygosity in the barnacle Balanus amphitrite Darwin (Cirripedia: Thoracica) , 1991 .

[2]  P. Davies,et al.  Effects of elevated nitrogen and phosphorus on coral reef growth1 , 1979 .

[3]  B. Rinkevich,et al.  'Fair is foul and foul is fair': response to a critique , 2003 .

[4]  T. Tomascik,et al.  Effects of eutrophication on reef-building corals , 1985 .

[5]  J. Erez,et al.  Monitoring the Health of Coral Reef Ecosystems Using Community Metabolism , 2004 .

[6]  B. Rinkevich,et al.  Effects of particulate matter released by a fish farm (Eilat, Red Sea) on survival and growth of Stylophora pistillata coral nubbins. , 2003, Marine Pollution Bulletin.

[7]  Yossi Loya,et al.  The Coral Reefs of Eilat — Past, Present and Future: Three Decades of Coral Community Structure Studies , 2004 .

[8]  Y. Loya,et al.  In situ eutrophication caused by fish farms in the northern Gulf of Eilat (Aqaba) is beneficial for its coral reefs: a critique , 2003 .

[9]  T. Hughes.  Catastrophes, Phase Shifts, and Large-Scale Degradation of a Caribbean Coral Reef , 1994, Science.

[10]  A. Szmant.  Nutrient enrichment on coral reefs: Is it a major cause of coral reef decline? , 2002 .

[11]  B. Lapointe.  Nutrient thresholds for bottom‐up control of macroalgal blooms on coral reefs in Jamaica and southeast Florida , 1997 .

[12]  W. Dennison,et al.  ENCORE: the effect of nutrient enrichment on coral reefs. Synthesis of results and conclusions. , 2001, Marine pollution bulletin.

[13]  P. Harrison,et al.  Reproduction, dispersal and recruitment of scleractinian corals , 1990 .

[14]  R. Grigg,et al.  Natural and anthropogenic disturbance on coral reefs , 1990 .

[15]  S. Ward,et al.  Impact of elevated ammonium on reproduction in two Hawaiian scleractinian corals with different life history patterns. , 2002, Marine pollution bulletin.

[16]  R. Ormond,et al.  Coral death from sewage and phosphate pollution at Aqaba, Red Sea , 1982 .

[17]  B. Lazar,et al.  Vertical mixing and coral death in the Red Sea following the eruption of Mount Pinatubo , 1995, Nature.

[18]  Y. Loya,et al.  The Reproduction of the Red Sea Coral Stylophora pistillata. I. Gonads and Planulae , 1979 .

[19]  L. McCook.  Macroalgae, nutrients and phase shifts on coral reefs: scientific issues and management consequences for the Great Barrier Reef , 1999, Coral Reefs.

[20]  Evan N. Edinger,et al.  Normal Coral Growth Rates on Dying Reefs: Are Coral Growth Rates Good Indicators of Reef Health? , 2000 .

[21]  P. Harrison,et al.  Elevated levels of nitrogen and phosphorus reduce fertilisation success of gametes from scleractinian reef corals , 2001 .

[22]  Y. Loya,et al.  Deterioration Index (DI): a suggested criterion for assessing the health of coral communities. , 2004, Marine pollution bulletin.

[23]  W. Wiebe,et al.  Biogeochemical nutrient cycles in coral-reef ecosystems , 1990 .

[24]  William J. Kimmerer,et al.  Kaneohe Bay Sewage Diversion Experiment: Perspectives on Ecosystem Responses to Nutritional Perturbation , 1981 .

[25]  P. Hallock,et al.  The role of nutrient availability in bioerosion: Consequences to carbonate buildups , 1988 .

[26]  T. Done.  Phase shifts in coral reef communities and their ecological significance , 1992, Hydrobiologia.

[27]  L. McCook,et al.  Competition between corals and algae on coral reefs: a review of evidence and mechanisms , 2001, Coral Reefs.

[28]  R. Richmond.  Reproduction and Recruitment in Corals: Critical Links in the Persistence of Reefs , 1997 .

[29]  J. Jaubert,et al.  Effect of nutrient enrichment on growth and photosynthesis of the zooxanthellate coral Stylophora pistillata , 2000, Coral Reefs.

[30]  P. Bell,et al.  Eutrophication and coral reefs—some examples in the Great Barrier Reef lagoon , 1992 .

[31]  Semion Kaganovsky,et al.  Mass Transport from Pollution Sources to Remote Coral Reefs in Eilat (Gulf of Aqaba, Red Sea) , 1999 .

[32]  P. Sammarco,et al.  Effects of temperature and ammonium on larval development and survivorship in a scleractinian coral (Diploriastrigosa) , 2003 .

[33]  Y. Loya,et al.  The reproduction of the Red Sea Coral Stylophora pistillata.II.Synchronization in breeding and seasonality of planulae shedding. , 1979 .

[34]  O. Hoegh‐Guldberg,et al.  Response of a scleractinian coral, Stylophora pistillata, to iron and nitrate enrichment. , 2001, Journal of experimental marine biology and ecology.

[35]  B. Rinkevich,et al.  Survival, growth and gonad development of two hermatypic corals subjected to in situ fish-farm nutrient enrichment , 2003 .

[36]  Z. Dubinsky,et al.  Effects of Nutrient Enrichment and Water Motion on the Coral Pocillopora damicornis , 1991 .

[37]  A. Robertson,et al.  Review of research relevant to the conservation of shallow tropical marine ecosystems , 1989 .

[38]  P. Davies,et al.  Nitrate increases zooxanthellae population density and reduces skeletogenesis in corals , 1996 .

[39]  Growth response of the reef coral Acropora longicyathus to elevated inorganic nutrients: do responses to nutrients vary among coral taxa? , 2002 .

[40]  Y. Loya,et al.  Coral Health and Disease , 2004, Springer Berlin Heidelberg.

[41]  Y..  The Reproduction of the Red Sea Coral Stylophora pistillata , 2022 .

[42]  R. Grigg,et al.  Coral reefs in an urban embayment in Hawaii: a complex case history controlled by natural and anthropogenic stress , 1995, Coral Reefs.

[43]  R. Pastorok,et al.  Effects of sewage pollution on coral-reef communities , 1985 .

[44]  J. Bruno,et al.  Nutrient enrichment can increase the severity of coral diseases , 2003 .

[45]  F. Sander,et al.  Effects of eutrophication on reef-building corals , 1987 .

[46]  Harrison,et al.  Changes in gametogenesis and fecundity of acroporid corals that were exposed to elevated nitrogen and phosphorus during the ENCORE experiment. , 2000, Journal of experimental marine biology and ecology.

[47]  B. Willis,et al.  Reproductive energy investment in corals: scaling with module size , 2003, Oecologia.

[48]  J. Burkholder,et al.  Emerging marine diseases--climate links and anthropogenic factors. , 1999, Science.

[49]  P. Harrison,et al.  The effects of elevated nutrients on settlement of coral larvae during the ENCORE experiment , 1997 .

[50]  Z. Dubinsky,et al.  Marine pollution and coral reefs , 1996 .

[51]  G. Wefer,et al.  A 200-year coral stable oxygen isotope record from a high-latitude reef off Western Australia , 1999, Coral Reefs.