Title
Long-term changes in coral colony size distributions on Kenyan reefs under different management regimes and across the 1998 bleaching event
Author(s)
McClanahan, T.R.; Ateweberhan, M.; Omukoto, J.
Published
2008
Publisher
Marine Biology
Abstract
Colony size is an important life-history characteristic of corals and changes in colony size will have significant effects on coral populations. This study summarizes ~21,000 haphazard colony size measurements of 26 common coral taxa (mostly coral genera) collected annually between 1992 and 2006 in seven Kenyan reef lagoons. There was a major coral bleaching and mortality event in early 1998 and all seven reefs were affected. The seven locations include two long-protected Marine National Parks (Malindi and Watamu), one relatively recently established park (Mombasa), and four unprotected locations (Vipingo, Kanamai, Ras Iwatine, and Diani). They span about 150 km and represent three distinct fishery management regimes: old protected (OP), newly protected (NP), and unprotected (UP). Seventeen taxa had statistically significant different sizes for comparisons of the management regimes, with only one genus, Pavona, having larger sizes in the unprotected reefs. The size of eight coral genera showed a significant time and management interaction, and size frequency differences that existed in management areas prior to 1998 were further increased after the bleaching event. Time alone was a significant factor for eleven genera, and in all cases colonies were smaller after 1998. For most taxa, colony size distributions were significantly skewed and had right-tailed distributions. After 1998, the right-tailed distributions of Acropora, Hydnophora, and Montipora were significantly reduced. Most taxa had peaky distributions and only Acropora experienced a statistically significant change from peaky to flat. The mean sizes of taxa were not related to their mortality across 1998, which indicates that the size effect was within rather than between taxa. Astreopora and Platygyra were well-sampled taxa that did not show an effect of management, but had reduced median sizes across 1998. Consequently, no taxa were tolerant of both fishing and bleaching disturbances and the combined effect was to reduce the size of all corals. © 2007 Springer-Verlag.
Keywords
bleaching; colony; coral reef; fishery management; lagoon; long-term change; marine park; measurement method; mortality; size distribution; size effect; Africa; Coast Province; Diani Reef; East Africa; Kanamai Reef; Kenya; Malindi Marine Park; Mombasa; Ras Iwatine; Sub-Saharan Africa; Vipingo Reef; Watamu Marine National Park; Acropora; Anthozoa; Astreopora; Hydnophora; Montipora; Pavona; Platygyra
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