Predawn episodes of mass spawning by green algae (up to nine species in five genera on a single morning) intermittently cloud Caribbean waters. Species-and sex-specific bouts of anisogamous gamete release occurred synchronously and predictably on a given morning, with closely related species spawning at different times. Algal sexual reproduction was seasonal, but, unlike the mass-spawning behavior of other sessile marine organisms, showed no lunar or tidal cycling. The discovery of mass-spawning behavior by these algae has important implications for future studies of the reproductive ecology and speciation of a vital, yet poorly understood, component of the coral reef community.Oiphonous green algae (order Bryopsidales) currently thriving on coral reefs throughout the world are a vital component of the reef community. As large, abundant primary producers, they help anchor one of the world's most complex trophic networks by providing food and shelter to countless reef organisms (J). As competitors for space with corals and other benthic organisms (2), their shifting abundance provides an index of reef health (3). Their complex

Recent field observations of highly organized, species‐ and sex‐specific patterns of synchronous gamete release by tropical green algae (Bryopsidales) invite a variety of future studies into the ecology and life histories of an important component of tropical reef communities. This paper details sexual reproduction by 22 algal species within five common genera (Caulerpa, Halimeda, Penicillus, Rhipocephalus, and Udotea), including field observations on the spatial occurrence, timing, and color changes associated with fertility, data on gamete size and behavior, and descriptions of coincident changes in local species abundances.  Ecologically ephemeral episodes of sexual reproduction involved macroscopic changes that reliably indicated developmental state and sexual identity. The time from onset of fertility to gamete release was 36 h (Halimeda), 48 h (Caulerpa, Penicillus, and Rhipocephalus), or 96 h (Udotea). All species produced flagellated, negatively buoyant, anisogamous gametes. Microgametes of all species were similar in size; however, considerable species‐specific differences were seen in the size of macrogametes. In Caulerpa, Halimeda, and Udotea flabellum (Ellis and Solander) Lamouroux, the volumetric ratio of macrogametes to microgametes ranged from 2:1 to 45: 1, whereas more extreme levels of anisogamy (104: 1) were observed for Penicillus spp., Rhipocephalus phoenix (Ellis and Solander) Kuetzing, and other Udotea spp. The macrogametes of Caulerpa and Halimeda showed strong positive phototaxis.  Although only a subset (generally about 5%) of the thalli representing each species released gametes on a given morning, most species underwent bouts of sexual reproduction on numerous occasions during the seasonal peak of reproductive activity (March–May). As might be expected for holocarpic species, dramatic declines in local algal abundance coincided with these periods. The density of sand‐dwelling genera such as Penicillus fell by 80– 90% during this 3‐month period in 1997. Similar declines in the cover of sprawling species such as Caulerpa racemosa ((Forsskal) J. Agardh) exposed large (35–50 m2) sections of previously overgrown reef substrate.

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The foraging of female Thomson's gazelles (Gazella thomsoni) on shortgrass plains was monitored over one annual cycle in southwestern Kenya. Sward dry green biomasses and protein densities were estimated regularly throughout the study site. Changes in protein densities with season and locale were strongly correlated with underlying changes in grass physiognomy: sward height and dry green bulk biomass density were particularly important and were found to vary inversely. The relationship between bite rates and underlying sward parameters varied with season: gazelle bite rates in the dry season were positively correlated with underlying dry green biomass and protein densities, as predicted by either the Process 1 or Process 2 foraging model of Spalinger and Hobbs. Nonlinear regressions of within—bout bite rates on these model equations significantly explained 21.8 and 23.7% of the dry season variance, respectively. In contrast, bite rates in the early wet season showed significant negative correlations with underlying protein densities: the fit of the within—bout bite rate data to Spalinger and Hobbs' Process 3 model explained 18.4% of the overall variation. The late wet season showed a flat (insignificant) relationship between bite rates and protein levels and was thus intermediate between early wet— and later dry—season patterns. Logistic regression of the type of correlation between bite rate and protein density (positive, flat, negative) on two principal components of grass physiognomy suggested that a component heavily weighting sward height was the major correlate of foraging process, whereas a second major component heavily weighting bulk density and other grass quality measures was less critical. At least during this single annual cycle, shorter swards were associated with Processes 1 or 2, whereas taller swards showed Process 3 foraging. One interpretation of these results is that sward height modulates bite mass, which in turn plays the major role in controlling foraging process. Whether the switching point remains the same in subsequent years or not, the results make it clear that the direction of the bite rate vs. foraging density relationship can change markedly with season, as predicted by the Spalinger and Hobbs models.