Associações entre peixes, invertebrados bentônicos e variáveis ambientais em um sistema lagunar no Estado do Rio de Janeiro

Abstract

Coastal lagoons are shallow water bodies separated from the sea by any type of barrier or with limited connection with the marine environment through natural or man-made channels. Due to the high productivity, these ecosystems shelter distinct communities as fish and benthic invertebrates, which shows high economic and ecological value. The aim of this work was to evaluate the variation in the structure of the ichthyofauna and benthic invertebrates over environmental gradients during dry and rainy seasons, in addiction to assess eventual association between both biotic groups in the Maricá Lagoon System, located at Maricá city, Rio de Janeiro State. The tested hypothesis is that environmental variables determine the fish and benthic invertebrates’ distribution and that these variables are s influenced by the distance from the sea connection, and that these two communities present significant association Three zones were established to the sampling program according to the distance from the sea connection: Inner Zone (IZ, more distant from the sea conection), Middle Zone (MZ) and Outer Zone (OZ, closer to the connection with the sea ). The collection of biotic material and the environmental variables measurements occurred in July 2018 (dry season) and January 2019 (rainny season). The fish community structure differed significantly among zones, seasons and was significant for the interaction between these two factors (p < 0,05). Higher fish abundance was found in IZ and lower in OZ. Atherinella brasiliensis and Anchoa januaria were the species with most contribution in all zones and seasons. Temperature and salinity were the variables that presented the greatest independent explanatory power among the predictors of species richness (49.29 % and 18.29%, respectively) of the fish community, showing negative and positive correlations, respectively. The benthic invertebrates were significantly different among all studied factors. The greatest abundance was found on IZ and the lowest on OZ. Nereididae were the polychaetes family with most contribution on dry season and on inner and middle zones. Oligoquetas was the invertebrate group that most contributed on rainy season. Capitellidae presented most contribution on OZ. Concerning the benthic invertebrates, salinity and temperature were the variables with greatest independent explanatory power (40,047% and 18.85%, respectively). Contrarily to fishes, salinity showed significantly negative correlation and temperature showed positive correlation with benthic invertebrate. The correlation between these two groups was significative but low, even after the environmental variables control. Fish and benthic invertebrates that share the Maricá Lagoon System are submitted to similar environmental conditioning, that seem to act in different way for each group. Most of the explained variation of the fish community was associated with effects shared by environmental variables and by the spatial-zone structure (16%), and a negligible fraction was explained exclusively by invertebrates (1%). Considering benthic invertebrates, larger fractions (18%) were associated with the effects shared by the three factors (fish, environmental variables and zones), in addition to a significant additional explanation being shared by environmental variables and zone (10%) and by the exclusive explanation of environmental variables (13%).Understand the way that each taxonomic group responds to environmental variables and the spatial structure simultaneously could be an important tool to help decision-making related to the conservation of aquatic ecosystem in different scales.