ZONATION AND SEASONAL-VARIATION OF THE INTERTIDAL MACROFAUNA ON A SANDY BEACH OF PARANA STATE, BRAZIL

The intertidal macrofauna of an exposed sandy beach was studied from January 1987 to January 1988, in Barrancos, Parana State (SE Brazil). The sediments consisted of well-sorted fine sand, with a mean grain size of 150 um. Finer and better-selected sand grains were found near the dunes. The profile of the studied beach had a slope of 1.25 degrees to 2.00 degrees. The morphodynamics modal state of the beach was characterized as dissipative (Ohm = 8.2). Thirty-five species were collected throughout the study. Four intertidal zones were identified by their macrofauna: a dry sand zone characterized by Bledius bonariensis and Orchestoidea brasiliensis; a retention zone by Tholozodium rhombofrontalis, Euzonus furciferus and Excirolana armata; a resurgence zone by Scolelepis squamata, Puelche sp A and Donax hanleyanus; and a saturation zone by Donax gemmula, Bathyporeiapus ruffoi, Hemipodus olivieri, Lepidopa richmondi, Pinnixa patagoniensis, Puelche sp B and Hastula salleana. This zonation scheme was persistent throughout the year. Despite spatial variations, the distribution of characteristic species was centered in their own zones, Significant variation in population densities and species richness occurred between late winter and early summer, suggesting a species recruitment.