CONICET | Buscador de Institutos y Recursos Humanos

Among the predators, fish are prevalent in intertidalsoft-bottom zones, and many create substantial interruptionsin the sediment surface through their feeding, thus affectingthe movement of fluids in the sediment-water interface andtherefore the rates of deposition and local erosion. This studywas designed to determine whether or not Micropogoniasfurnieri?an ecologically significant benthophagic southwesternAtlantic Ocean predator?modified erosion and/or sedimentationprocesses in salt marshes. The results indicated thatthis species exhibited a preference for areas without vegetationcover at the time of feeding since a greater abundance of pitswas found in those environments. Moreover, the volume analysisof the pits in the two areas indicated that the size of thefish that had foraged in the sediment was significantly larger in the nonvegetated areas. The results of the M. furnieri-exclusionexperiment indicated that the presence of this sciaenidneither resulted in a decrease in benthic organisms in thenonvegetated areas nor affected the vertical distribution ofthe infauna. When M. furnieri was excluded, the sedimentexhibited higher critical-shearing and frictional-velocityvalues than in areas where M. furnieri had access and thereforewas less likely to be eroded. The data from these experimentsenabled us to conclude that the foraging action ofM. furnieri modified the stability of the sediment as a resultof the predatory pressure that the fish exerted on the organismsinhabiting the salt marshes, thus resulting in the generation ofelliptical depressions. That modification of the sediment stabilitywas evidenced in two principal ways: (i) a negativeeffect on the microphytobenthic organisms that decreasedthe concentration of extracellular polymeric substances inthe sediment and (ii) an increased roughness of the bottomand increased percentage of sand in the particle compositionof the sediment, where the fish had foraged.

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