Wind-mediated diel variation in flow speed in a Jamaican back reef environment: Effects on ecological processes

Genovese, SJ Witman, JD

BULLETIN OF MARINE SCIENCE 75:2 281-293

The movement of water plays an important role in a number of physiological (e.g., metabolic rate, nutrient uptake) and ecological (e.g., foraging, fertilization) processes for coral reef organisms. In the back reef of Discovery Bay, Jamaica, daytime mean flow speeds were on average, 61% greater than at night during a given 24 hr period. Wind speed was a significant predictor of flow speed in these shallow water environments, with the variation in wind speed able to explain 30% of the variation in flow speed. Porter’s (1985) yearlong wind speed record in Discovery Bay indicated that the time of maximum daily wind speed occurred during daylight hours for 93% of the year. Activity of the fireworm, Hermodice carunculata (Pallas, 1766), represented by total abundance in six, 1 x 30 m transects was negatively correlated with flow speed. Atmospheric and oceanographic conditions enhancing wind-dependent water flow in back reef environments include prevalent tradewinds and negligible tidal currents, which suggests that the diel variation in flow speed documented for Discovery Bay may be a common phenomenon in similar environments. Such predictable environmental variability may be an important selective agent shaping the evolution of diel rhythms of reef invertebrates and algae. Therefore, recent atmospheric and climatological shifts (e.g., frequency of El Nino events, global climate change) may exert additional selective pressure on the organisms found in these environments.

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