Meteorology and hydrography of a shoaling reef flat on the Caribbean coast of Panama

We describe the seasonal patterns and frequency distributions of meteorological and hydrographic conditions on a windward, shoaling reef flat at Punta Galeta, Panama (9° 24 N lat.), between 1974 and 1985. The factors monitored were wind speed, wind direction, air temperature, rainfall, solar radiation, water level, water temperature, and salinity. All conditions showed strong seasonal periodicity; however, the timing, duration, and amplitude of the seasonal fluctuations differed among years. The greatest variation occurred in 1981 and 1982, leading into an El Niño event. Emergence of the reef flat and extremes of water temperature were the most apparent physiological stresses; both were dependent on mean water levels. The seasonal pattern of emergence time was inversely related to mean water level. Extreme water temperatures only occurred during low water tevels, ranging between 22° to >37°C in depths <15 cm, but staying between 25°C and 30.9°C in depths <35 cm. Water temperatures averaged 1.5°C higher than air temperatures. Although rainfall was 200 to 400 cm year^-1, salinity remained between 24 and 36 ppt, with more than 98% of the records 30 ppt. The relationship of water temperature to depth is consistent with the hypothesis that the physical environment becomes more stressful when a reef reaches sea level and forms a shoaling platform.Mailing address: Smithsonian Tropical Research Institute, APO Miami, Florida 34002-0011, USA