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ENCORE: the effect of nutrient enrichment on coral reefs: synthesis of results and conclusions
Koop, K.; Booth, D.; Broadbent, A.; Brodie, J.; Bucher, D.; Capone, D.; Coll, J.; Dennison, W.; Erdmann, M.; Harrison, P.; Hoegh-Guldberg, O.; Hutchings, P.; Jones, G.B.; Larkum, A.W.D.; O'Neil, J.; Steven, A.; Tentori, E.; Ward, S.; Williamson, J.; Yellowlees, D. (2001). ENCORE: the effect of nutrient enrichment on coral reefs: synthesis of results and conclusions. Mar. Pollut. Bull. 42(2): 91-120
In: Marine Pollution Bulletin. Macmillan: London. ISSN 0025-326X, more
Peer reviewed article  

Available in  Authors 

    Biota; Coastal waters; Coral; Coral reefs; Environmental impact; Eutrophication; Lethal limits; Marine environment; Mortality; Nitrogen; Nutrients (mineral); Phosphorus; Pollution effects; Pollution indicators; Recruitment; Skeleton; Sublethal effects; Toxicity; Water pollution; Zooxanthellae; Acropora aspera (Dana, 1846) [WoRMS]; Acropora longicyathus (Milne Edwards, 1860) [WoRMS]; Pocillopora damicornis (Linnaeus, 1758) [WoRMS]; ISEW, Australia, Queensland [Marine Regions]; ISEW, Great Barrier Reef, One Tree I. [Marine Regions]; Marine

Authors  Top 
  • Koop, K.
  • Booth, D.
  • Broadbent, A.
  • Brodie, J.
  • Bucher, D.
  • Capone, D.
  • Coll, J.
  • Dennison, W.
  • Erdmann, M.
  • Harrison, P.
  • Hoegh-Guldberg, O.
  • Hutchings, P.
  • Jones, G.B.
  • Larkum, A.W.D.
  • O'Neil, J.
  • Steven, A.
  • Tentori, E.
  • Ward, S.
  • Williamson, J.
  • Yellowlees, D.

    Coral reef degradation resulting from nutrient enrichment of coastal waters is of increasing global concern. Although effects of nutrients on coral reef organisms have been demonstrated in the laboratory, there is little direct evidence of nutrient effects on coral reef biota in situ. The ENCORE experiment investigated responses of coral reef organisms and processes to controlled additions of dissolved inorganic nitrogen (N) and/or phosphorus (P) on an offshore reef (One Tree Island) at the southern end of the Great Barrier Reef, Australia. A multi-disciplinary team assessed a variety of factors focusing on nutrient dynamics and biotic responses. A controlled and replicated experiment [using nutrient enrichment] was conducted over two years using twelve small patch reefs ponded at low tide by a coral rim. A variety of biotic processes, assessed over a year during this initial nutrient loading phase, were not significantly affected, with the exception of coral reproduction, which was affected in all nutrient treatments. In Acropora longicyathus and A. Aspera, fewer successfully developed embryos were formed, and in A. Longicyathus fertilization rates and lipid levels decreased. Encrusting algae incorporated virtually none of the added nutrients. Organisms containing endosymbiotic zooxanthellae (corals and giant clams) assimilated dissolved nutrients rapidly and were responsive to added nutrients. Coral mortality, not detected during the initial low-loading phase, became evident with increased nutrient dosage, particularly in Pocillopora damicornis. Nitrogen additions stunted coral growth, and phosphorus additions had a variable effect. Coral calcification rate and linear extension increased in the presence of added phosphorus but skeletal density was reduced, making corals more susceptible to breakage. Settlement of all coral larvae was reduced in nitrogen treatments, yet settlement of larvae from brooded species was enhanced in phosphorus treatments. Recruitment of stomatopods, benthic crustaceans living in coral rubble, was reduced in nitrogen and nitrogen plus phosphorus treatments. Grazing rates and reproductive effort of various fish species were not affected by the nutrient treatments. Microbial nitrogen transformations in sediments were responsive to nutrient loading with nitrogen fixation significantly increased in phosphorus treatments and denitrification increased in all treatments to which nitrogen had been added. Rates of bioerosion and grazing showed no significant effects of added nutrients. ENCORE has shown that reef organisms and processes investigated in situ were impacted by elevated nutrients. Impacts were dependent on dose level, whether nitrogen and/or phosphorus were elevated and were often species-specific. The impacts were generally sub-lethal and subtle and the treated reefs at the end of the experiment were visually similar to control reefs.

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