Potencial de utilização de anfípodes caprelídeos (Crustacea - Peracarida) como bioindicadores de compostos organoestânicos no litoral norte de São Paulo

Abstract

The caprellid amphipods are small crustaceans, usually with 0.1 to 3 cm long, belonging to the suborder Caprellidea. The caprellids have an important ecological function, because in addition to providing the connection between primary producers and higher trophic levels, they are sensitive to environmental variations, toxins and pollutants. Among these pollutants, organotin compounds, such as the tributyltin (TBT) stands out. The TBT is commonly used as active ingredient in biocides. Its wider application, however, is in the hulls of vessels due to its anti-fouling effect. Due to these factors, TBT and its derivatives (dibutyltin - DBT and monobutyltin - MBT) have caused environmental contamination in the marine environment, especially in the sediment and water, from areas with high boat traffic, like marinas and harbors. As the detection limits of organotins, such as TBT, through the normal analytical methods are relatively high, the use of marine organisms in the monitoring of these compounds are interesting because, besides accumulating these compounds, lower trophic level organisms such as caprellid amphipods, have higher concentrations of TBT. Therein, the aim of this study was evaluate the potential use of caprellids as bioindicators of OTs in the northern coast of São Paulo State. For this, two samplings were performed (December 2009 and March 2010) at three beaches (Fortaleza, Lázaro and Lamberto) from Ubatuba, SP. Ten individual fronds of Sargassum were collected per beach in each period to characterize the structure of caprellid assemblages. The environmental conditions of the beaches were evaluated by measurements of hydrodynamics, temperature, dissolved oxygen, turbidity and organic matter in water. The fronds were fixed, washed and examined and the organisms were identified to species level. For organotin evaluation, fifty fronds of Sargassum were collected, per beach, in each sampling period, from which caprellids were removed for analysis. In laboratory, the caprellids were stored in aluminum foil, frozen and sent to the organotin compounds analysis. The samples were then homogenized, and passed through an analytical procedure before analysis in a gas chromatography with pulsed flame photometric detector (GC-PFPD). To describe the caprellid assemblages, the density, species richness and indexes of diversity and evenness were calculated. Some differences in environmental conditions among beaches and between sampling periods were recorded. A total of 384 caprellids of nine different species were collected. The Lázaro beach had the highest density, richness, and diversity. Despite this species richness, only two species (Caprella danilevskii and Caprella dilatata) could be used in the organotin analyses, because of the amount of mass required by the method. High concentrations of TBT were found in the samples of C. danilevskii (above 200 ng Sn/g), whereas for C. dilatata the values were from below the detection limit up to 35 ng Sn/g. It is expected that with the implementation of new legislation in Brazil, there is a decrease in concentrations of TBT in the coastal areas of the country. However, the monitoring of TBT concentrations is still needed and the results obtained indicate that caprellids C. danilevskii stands out as an efficient bioindicator of TBT contamination in littoral north of São Paulo and another areas of Brazilian littoral, because this species besides concentrating this compound, can be easily collected, occurs in a wide variety of environmental conditions and is widely distributed in the country.