MEPS 123:273-280 (1995)  -  doi:10.3354/meps123273

Planktonic communities dwelling inside a submarine cave in the Medes Islands (NW Mediterranean) show a steady decrease in species richness and planktonic biomass along the longitudinal axis from the entrance to the end; the lowest species and biomass values were recorded at the innermost point of the cave. This study considers the role of sedimentation in the formation of this gradient, despite previous works having demonstrated the presence of strong advection of the water inside the cave. To this end, data on planktonic density at different points within the cave at different seasons were used, leading to the developement of a simple diffusion-sedimentation model which allowed us (1) to estimate characteristic times for the formation of particle gradients; in 24 h of simulation or less, gradients as marked as those found in the cave were obtained; these times are in accordance with water renewal times in the cave, calculated in previous works; and (2) to simulate some planktonic (phytozooplankton) gradient profiles; significant correlations for all phytoplankton cases and some for zooplankton profiles were found. The results show that sedimentation is sufficient to explain the establishment of the planktonic gradients inside the cave.

Diffusion-sedimentation model . Caves . Plankton . Gradients