A sampling program was set up to use benthos as an indicator of environmental impact on shrimp natural populations from August 1999 until February 2001. Meiobenthos and hyperbenthos were investigated quantitatively. It is important to notice that this period has been characterized by anomalous cold conditions during most of 1999 and 2000, and close to normal conditions during 2001. Total density from both benthic communities were analyzed during normal and anomalous conditions as were their responses to changes in environmental factors such as water temperature, salinity, median grain size, chlorophyll a, suspended particulate matter (SPM) and particulate organic matter (POM). Two sampling sites from the original seven were chosen based on one important characteristic: dominant use. The first site is a sandy beach mostly used for tourism (Salinas, 02°12'S 81°00'W); and the second is located in a fishing town (San Pedro, 01°55'53"S, 80°46'55"W). Fifteen meiobenthos taxa were identified. The meiofauna was mainly represented by nematodes which made up the highest population on both beaches. Total meiofauna density ranged from 244 to 2388 ind./10 cm2. Eight higher taxonomic levels of hyperbenthos were found in Salinas and seven in San Pedro, with total densities of 109-14911 ind/100m2 in Salinas, and 199-1672 ind/100m2 in San Pedro. Mysidacea was the most abundant hyperbenthic group, representing between 3.53 and 99.40 % of total density in Salinas and 3.76 - 98.31 % in San Pedro. |
