Abstract :
Nocturnal variations of zooplankton abundance and hydrographic conditions were examined at three locations (centre, north shore and south shore) in Phosphorescent Bay, Puerto Rico, from May 1992 through April 1993. Seven taxa accounted for approximately 96% of the annual mean zooplankton abundance:Oithonaspp. (43•5%),Acartia tonsa(31•5%), copepod nauplii (8•8%),Paracalanusspp.(6•7%), gastropod veligers (2•5%), larvaceans (1•7%) andPseudo-diaptomus cokeri(1•6%). Copepods dominated numerically throughout the year and comprised 94•3% of total zooplankton. Higher abundance of zooplankton (mean±1 SD=252 259±176 797 individuals m−3) was associated with cool water temperatures (24•9–27•4 °C) and dry conditions (0•3–2•9 cm precipitation/month) which prevailed between December and March relative to the period between April and November (warm/wet season) (mean±1 SD=59 773±26 861 individuals m−3), when temperature and precipitation were higher (27•3–30•3 °C, 3•1–20•6 cm month−1). Fluctuations of zooplankton populations, particularly copepods, followed progressive increments in chlorophyllaconcentrations. This abundance pattern was consistent at the three sampling stations. Zooplankton abundance was higher on the north shore of the bay. The taxonomic composition of zooplankton was similar at the sampling stations studied.
