Summary
Large differences in community structure of sea urchins and finfish have been observed in Kenyan reef lagoons. Differences have been attributed to removal of finfish predators through human fishing activities. This study attempted to determine (i) the major sea urchin finfish predators, (ii) the effect of predation on sea-urchin community structure, and (iii) the possible effect of sea urchin increases and finfish decreases on the lagoonal substrate. Six reefs, two protected and four unprotected, were compared for differences in finfish abundance, sea urchin abundance and diversity and substrate cover, diversity and complexity. Comparisons between protected and unprotected reefs indicated that finfish populations were ca. 4 x denser in protected than unprotected reefs. Sea urchin populations were >100 x denser and predation rates on a sea urchin, Echinometra mathaei, were 4 x lower in unprotected than in protected reefs. The balistidae (triggerfish) was the single sea-urchin finfish predator family which had a higher population density in protected than in unprotected reefs. Balistid density was positively correlated with predation rates on tethered E. mathaei (r=0.88; p<0.025) and negatively correlated with total sea-urchin density (r=−0.89; p<0.025) on the six reefs. We conclude from observations that the balistids Balistaphus undulatus and Rhinecanthus aculeatus are the dominant sea-urchin predators. The sea-urchin assemblage had its greatest diversity and species richness at intermediate predation rates and low to intermediate sea-urchin densities. At low predation rates and high sea-urchin density E. mathaei dominated the assemblage's species composition. Preferential predation on the competitive dominant maintains the assemblage's diversity, supporting the compensatory mortality hypothesis (Connell 1978) of coral reef diversity. Protected reefs had greater cover of hard coral, calcareous and coralline algae, and greater substrate diversity and topographic complexity than unprotected reefs which had greater algal turf and sponge cover. Coral cover and topographic complexity were negatively correlated with total sea urchin density. Although experimentation is lacking, these substrate changes may be due to the switch from finfish to sea-urchins as consumers which results from overfishing of finfish. Removal of top invertebrate-eating carnivores appears to have cascading effects on the entire coral reef ecosystem.
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References
Birkeland C (1982) Terrestrial runoff as a cause of outbreaks of Acanthaster planci (Echinodermata: Asteroidea). Mar Biol 69: 175–185
Birkeland C (1988) The influence of echinoderms on coral-reef communities. Echinoderm studies. AA Balkema, Rotterdam
Campbell AC, Dart JKG, Head SM, Ormond RFG (1973) The feeding activity of Echinostrephus molaris (de Blainville) in the central Red Sea. Mar Behav Physiol 2: 155–169
Carpenter RC (1981) Grazing by Diadema antillarum (Philippi) and its effects on the benthic algal community. J Mar Res 39: 749–765
Carpenter RC (1985) Sea urchin mass-mortality: effects on reef algal abundance, species composition, and metabolism and other coral reef herbivores. Proc 5th Int Coral Reef Symp 4: 53–59
Clark AM, Rowe FWE (1971) Monograph of the shallow-water Indo-West Pacific echinoderms British Museum of Natural History Publication 690. Pitman Press, Bath, England
Connell JH (1978) Diversity in tropical rain forests and coral reefs. Science 199: 1302–1310
Crame AJ (1986) Late Pleistocene molluscan assemblages from the coral reefs of the Kenyan coast. Coral Reefs 4: 183–196
Doherty PJ (1983) Tropical territorial damselfishes: is density limited by aggression or recruitment? Ecology 64: 176–190
Downing N, El-Zahr CR (1987) Gut evacuation and filling rates in the rock-boring sea urchin, Echinometra mathaei. Bull Mar Sci 41: 579–584
Ebert TA (1982) Longevity, life history, and relative body wall size in sea urchins. Ecol Monogr 52: 353–394
Glynn PW, Wellington GM, Birkeland C (1979) Coral reef growth in the Galapagos: limitations by sea urchins. Science 203: 47–49
Grigg RW, Polovina JJ, Atkinson MJ (1984) Model of a coral reef ecosystem. III. Resource limitation, community regulation, fisheries yield and resource management. Coral Reefs 3: 23–28
Hamilton HGH, Brakel WH (1984) Structure and coral fauna of East African reefs. Bull Mar Sci 34: 248–266
Hay ME (1984a) Patterns of fish and urchin grazing on Caribbean coral reefs: are previous results typical? Ecology 65: 446–454
Hay ME (1984b) Predictable spatial escapes from herbivory: how do these affect the evolution of herbivore resistance in tropical marine communities? Oecologia 58: 299–308
Hay ME, Taylor PR (1985) Competition between herbivorous fishes and urchins on Caribbean reefs. Oecologia (Berl) 65: 591–598
Hay ME, Colburn T, Downing D (1983) Spatial and temporal patterns in herbivory on Caribbean reefs. Oecologia 58: 299–308
Hutchings PA (1986) Biological destruction of coral reefs: a review. Coral Reefs 4: 239–252
Khamala CPM (1971) Ecology of Echinometra mathaei (Echinoidea: Echinodermata) at Diani Beach, Kenya. Mar Biol 2: 167–172
Kohn AJ, Leviten PJ (1976) Effect of habitat complexity on population density and species richness in tropical intertidal predatory gastropod assemblages. Oecologia 25: 119–210
Lessios HA, Robertson DR, Cubit JD (1984) Spread of Diadema mass mortalities through the Caribbean. Science 226: 335–337
Lewis SA (1986) The role of herbivorous fishes in the community organization of a Caribbean reef community. Ecol Monogr 51: 183–200
Lubchenco J (1978) Plant species diversity in a marine intertidal community: importance of herbivore food preference and algal competitive abilities. Am Nat 112: 23–39
McClanahan TR (1988a) Coexistence in a sea urchin guild and its implications to coral reef diversity and degradation. Oecologia 77: 210–218
McClanahan TR (1988b) Seasonality in East Africa's coastal waters. Mar Ecol Prog Ser 44: 191–199
McClanahan TR (1989) Kenyan coral reef-associated gastropod fauna: a comparison between protected and unprotected reefs. Mar Ecol Prog Ser 53: 11–20
McClanahan TR, Muthiga NA (1988) Changes in Kenyan coral reef community structure and function due to exploitation. Hydrobiologia 166: 269–276
McClanahan TR, Muthiga NA (1989) Patterns of predation on a sea urchin, Echinometra mathaei (de Blainville), on Kenyan coral reefs. J Exp Mar Biol Ecol 126: 77–94
Morrison D (1988) Comparing fish and urchin grazing in shallow and deeper coral reef algal communities. Ecology 69: 1367–1382
Neudecker S (1979) Effects of grazing and browsing fishes on the zonation of corals in Guam. Ecology 60: 666–672
Ogden JC (1977) Carbonate-sediment production by parrot fish and sea urchins on Caribbean reefs. In: Forst S, Weiss M (eds) Caribbean reef systems: Holocene and ancient. Am Ass Petrol Geol Special paper 4, pp 281–288
Paine RT (1966) Food web complexity and species diversity. Am Nat 100: 65–75
Robertson DR, Gaines SD (1986) Interference competition structures habitat use in a local assemblage of coral reef surgeon-fishes. Ecology 67: 1372–1383
Routledge RD (1979) Diversity indices: which ones are admissible? J Theor Biol 76: 502–515
Sammarco PW (1980) Diadema and its relationship to coral spat mortality: grazing, competition, and biological disturbance. J Exp Mar Biol Ecol 45: 245–272
Scoffin TP, Stern CW, Boucher D, Fryal P, Hawkins CM, Hunter IG, MacGeachy JK (1980) Calcium carbonate budget of a fringing reef on the west coast of Barbados II. Erosion, sediments and internal structure. Bull Mar Sci 30: 475–508
Shulman MJ (1985) Variability in recruitment of coral reef fishes. J Exp Mar Biol Ecol 89: 205–219
Simpson EH (1949) Measurements of diversity. Nature 163: 688
Smith JLB (1965) The sea fishes of southern Africa. Central News Agency, South Africa
Wellington GM (1982) Depth zonation of corals in the Gulf of Panama: control of facilitation by resident reef fishes. Ecol Monogr 52: 223–241
Wilkinson CR, Sammarco PW (1983) Effects of fish grazing and damselfish territoriality. II. Nitrogen fixation. Mar Ecol Prog Ser 13: 15–19
Wilkinson CR, Williams D McB, Sammarco PW, Hogg RW, Trott LA (1984) Rates of nitrogen fixation on coral reefs across the continental shelf of the central Great Barrier Reef. Mar Biol 80: 255–262
Williams AH (1981) An analysis of competitive interaction in a patchy back-reef environment. Ecology 62: 1107–1120
Williams SL, Carpenter RC (1988) Nitrogen-limited primary productivity of coral reef algal turfs: potential contribution of ammonium excreted by Diadema antillarum. Mar Ecol Prog Ser 47: 145–152
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McClanahan, T.R., Shafir, S.H. Causes and consequences of sea urchin abundance and diversity in Kenyan coral reef lagoons. Oecologia 83, 362–370 (1990). https://doi.org/10.1007/BF00317561
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DOI: https://doi.org/10.1007/BF00317561