Seasonal and spatial patterns of deeply buried calanoid copepods on the Amazon shelf: Evidence for periodic erosional/depositional cycles

Seasonal sampling of Amazon shelf deposits revealed that calanoid copepods as well as other pelagic zooplankton were often buried along with benthic infauna throughout the upper ~25 cm of the sea-bed. During February through March, the period of rising to peak riverine discharge and maximum trade wind stress, shelf-wide maxima occur in numbers and depth of burial. Buried copepods were present in all stations with abundances reaching 5168 copepods m^-3 in the 10-25-cm depth interval off the river mouth in 18 m of water (Station RMT-2). The intact nature of the buried copepods and presence of phytoplankton within the digestive tracts of many, supports the notion that burial was sudden and rapid (~hours). In contrast, from August to October, the period of falling to low riverine discharge and minimum wind stress, burial of zooplankters was restricted to stations along a southern transect (ST) and at the innermost river mouth station (RMT-1). Burrowing macroinfauna, meiofauna and bacterial inventories increase dramatically at all shelf stations during the time of minimum zooplankton burial. Successful recolonization by benthos and lack of entrainment of water-column organisms show that the bottom is most stable during seasons of falling to low river flow. Sedimentologic and chemical, as well as biological, evidence indicates rapid turnover of ~20-30 cm of the sea-bed during rising- and peak-flow periods when the sea-bed is most unstable.