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Reproduction in the widely distributed tropical sea urchinEchinometra mathaei(de Blainville) was examined in three Kenyan reef lagoons that differed in substrate cover andE.mathaeipopulation density. Histological examination of the gonads and gonad index measurements for 3 years showed a seasonal reproductive cycle with gametogenesis commencing in July, when temperature and light are at their lowest, and spawning commencing in December and peaking in February to May, when temperature and light reach their annual maxima. Monthly gonad indices correlated significantly with seawater temperature and light intensity. Male urchins had mature gametes for a longer period (8 months) than females (6 months), possibly an adaptive strategy that increases the probability of fertilization. Lunar periodicity was not observed, as male and female gonads were full of gametes on all days of the lunar cycle during the period of spawning. The peak in spawning activity coincides with the peak in phytoplankton abundance, which could ensure high food availability for the planktonic larvae. Gonad weights were significantly higher relative to urchin weight at the reef having the largest mean sizes and lowest population of urchins, indicating availability of food resources for growth and reproduction.E.mathaeiat the reef with the highest density had the smallest urchins and high relative gonad sizes, indicative of a tradeoff between growth and reproduction when food is limited. [ABSTRACT FROM AUTHOR]

Macroalgae were experimentally reduced by approximately 2.5 kg/m2 on eight similar-sized patch reefs of Glovers Reef Atoll, Belize, in September 1998. Four of these reefs were in a protected 'no-take' zone and four were in a 'general use' fishing zone. Eight adjacent reefs (four in each management zone) were also studied as unmanipulated controls to determine the interactive effect of algal reduction and fisheries management on algae, coral, fish, and rates of herbivory. The 16 reefs were sampled five times for 1 year after the manipulation. We found that the no-fishing zone had greater population densities for 13 of 30 species of fish, including four herbivorous species, but lower herbivory levels by sea urchins. However, there was lower stony coral cover and higher macroalgal cover in the 'no-take' zone, both prior to and after the experiment. There were no significant effects of management on the percent cover of fleshy macroalgae. The algal reduction resulted in an increase in six fish species, includingfour herbivores and two which feed on invertebrates. One species, Lutjanus griseus, declined in experimental reefs. Macroalgal biomass quickly recovered from the reduction in both management areas within a few months, and by species-level community measures within 1 year, while stony coral was reduced in all treatments. Coral bleaching and Hurricane Mitch disturbed the site at the beginning of the study periodand may explain the loss of stony coral and rapid increase in erect algae. We suggest that reducing macroalgae, as a technique to restoreturf and encrusting coralline algae and stony corals, may work best after reefs have been fully protected from fishing for a period long enough to allow herbivorous fish to recover (i.e. >5 years). Further ecological studies on Glovers Reef are required to understand the shift from coral to algal dominance that has occurred on this reef in the last 25 years. [ABSTRACT FROM AUTHOR]

Interaction between the El Nino and Indian Ocean dipole ocean-atmosphere quasi-periodic oscillations produced one of the warmest seawatertemperatures on record in 1998. During the warm northeast monsoon inMarch and April, Kenya's shallow coral reefs experienced water temperatures between 30 and 31 deg. C and low winds. This caused large-scale bleaching of hard and soft corals at the end of March, which extended into the cooler months of May and June. Direct observations of coloration in the Mombasa Marine National Park found that the coral genera Acropora, Millepora, Pocillopora, branching Porites and Stylophora showed rapid bleaching and high mortality by the end of May 1998. Other hard coral genera that bleached significantly included Echinopora, Favia, Favites, Galaxea, Hydnophora, Goniopora, Leptoria, Montipora, Platygyra and massive Porites, but mortality was variable among these genera. Astreopora, Coscinarea, Cyphastrea and Pavona were the least responsive genera, with some paling, but little evidence of fullbleaching or significant mortality. We compared changes in reef ecology in four national parks (protected from fishing) with four non-park areas (heavy fishing) to determine how coral mortality and herbivory interact under the two management regimes. Benthic studies using line transects in 16 sites spread across ~150 km of coastline were completed before and 6 to 13 months after the bleaching event and found that the cover of nine hard coral genera including Acropora, Alveopora, Favites, Goniopora, Platygyra, Pocillopora, branching Porites, Stylophora and Tubipora decreased significantly (p<0.04) after the event,usually by >85%, and soft coral cover decreased by \sim75%. One yearafter the bleaching, sites in the national parks experienced 88 and 115% increases in turf and fleshy algal cover, respectively, while reefs outside the parks had a 220% increase in fleshy algal cover with no appreciable change in turf-forming algal cover. There was, however, hig [ABSTRACT FROM AUTHOR]