Top–down and bottom–up regulation of macroalgal community structure on a Kenyan reef
2009 (English)In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 84, no 3, 331-336 p.Article in journal (Refereed) Published
Top–down and bottom–up regulation in the form of grazing by herbivores and nutrient availability areimportant factors governing macroalgal communities in the coral reef ecosystem. Today, anthropogenicactivities, such as over-harvesting of herbivorous fish and sea urchins and increased nutrient loading, arealtering the interaction of these two structuring forces. The present study was conducted in Kenya andinvestigates the relative importance of herbivory and nutrient loading on macroalgal communitydynamics, by looking at alterations in macroalgal functional groups, species diversity (H0) and biomasswithin experimental quadrats. The experiment was conducted in situ for 42 days during the dry season.Cages excluding large herbivorous fish and sea urchins were used in the study and nutrient addition wasconducted using coated, slow-release fertilizer (nitrogen and phosphorous) at a site where herbivory isgenerally low and nutrient levels are relatively high for the region. Nutrient addition increased tissuenutrient content in the algae, and fertilized quadrats had 24% higher species diversity. Herbivoreexclusion resulted in a 77% increase in algal biomass, mainly attributable to a >1000% increase in corticatedforms. These results are in accordance with similar studies in other regions, but are unique in thatthey indicate that, even when prevailing nutrient levels are relatively high and herbivore pressure isrelatively low, continued anthropogenic disturbance results in further ecological responses and increasedreef degradation.
Place, publisher, year, edition, pages
2009. Vol. 84, no 3, 331-336 p.
macroalgae, grazing, nutrients, coral reefs, community composition, reef degradation
IdentifiersURN: urn:nbn:se:su:diva-45795DOI: 10.1016/j.ecss.2009.03.033ISI: 000270122400006OAI: oai:DiVA.org:su-45795DiVA: diva2:369771