Short-term variability in primary productivity during a wind-driven diatom bloom in the Gulf of Eilat (Aqaba)

In the northern Gulf of Eilat (Aqaba), sharp increases in the biomass of diatoms and rates of primary production occurred in April 2008. Within 24 h, diatom abundance rose from 8 Ã- 10³ to 228 Ã- 10 ³ cells l^-1, and photosynthetic rates concomitantly doubled from 15 to 35 μg C l^-1 d^-1. Water transparency declined, as indicated by the vertical diffusion attenuation coefficient K ^d for photosynthetically active radiation (PAR), which increased from 0.076 to 0.090 m^-1 and decreased the euphotic depth from 60 to 45 m. During this time, a significant increase in silica deposition by the diatoms was also detected. We attribute the mentioned changes in environmental characteristics to wind-generated surface currents. Strong winds (up to 10 m s^-1) during the measurements enriched the surface layers with unusually high nutrient concentrations within.