Barreira química para a dispersão da ictiofauna: uma análise do rio Tietê e seus tributários
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2024-02-26
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Universidade Estadual Paulista (Unesp)
Resumo
Ao longo do tempo, barreiras artificiais para a dispersão das espécies surgiram como consequência do crescimento populacional e do desenvolvimento econômico da sociedade. No caso dos ambientes aquáticos, sabe-se que diferentes tipos de distúrbios antrópicos podem influenciar nesse processo, sendo a poluição um importante fator modificador da estruturação da biota regional, principalmente da ictiofauna. A bacia do rio Tietê, que possui um longo histórico de degradação ambiental, apresenta, em seu trecho médio, ambientes contrastantes em termos de qualidade de água. Contudo, estes sistemas fluviais estão amplamente interligados, sem quaisquer barreiras físicas naturais ou artificiais que possam interferir na livre circulação dos organismos. Nesse contexto, o objetivo deste trabalho foi avaliar as limitações que ocorrem no processo de dispersão da fauna de peixes dessa bacia, entre o rio Tietê e seus afluentes diretos (rio Sorocaba, rio Capivari e rio do Peixe), devido à poluição das águas do rio principal. O estudo se baseou em inventários da comunidade íctica por meio de redes de espera, seus atributos ecológicos e na determinação simultânea das variáveis limnológicas no final das estações chuvosa (abril de 2019) e seca (outubro de 2019). Para ambos os períodos de amostragem, a análise de componentes principais (ACP) mostrou uma clara diferença na qualidade da água do rio principal (pior condição) em comparação com os afluentes (melhor condição). Essa diferença também foi evidenciada através do nMDS baseado na composição da ictiofauna dos rios, com a diversidade de espécies muito maior nos tributários (11 a 14 spp.) em relação ao rio Tietê (3 a 4 spp.). A análise do DistLM mostrou que existe uma correlação significativa entre as variáveis limnológicas e a estrutura da ictiofauna apenas na estação chuvosa, o que pode ser explicado pela diferença marcante nas condições ambientais, especialmente neste período. Os resultados mostram que os efeitos da poluição atuam como uma barreira química para a dispersão de organismos sensíveis, ou menos tolerantes, e demonstram a urgência de implementar medidas de mitigação da poluição na bacia do Rio Tietê.
Over time, artificial barriers to species dispersal have emerged as a consequence of population growth and the economic development of society. In the case of aquatic environments, it is known that different types of anthropic disturbances can influence this process, with pollution being an important modifying factor for the structuring of the regional biota, especially the ichthyofauna. The Tietê River basin, which has a long history of environmental degradation, exhibits, in its middle section, contrasting environments in terms of water quality. However, these river systems are widely interconnected, without any natural or artificial physical barriers that could interfere with the free movement of the organisms. In this context, the goal of this work was to evaluate the limitations that occur in the process of dispersal of the fish fauna of this basin, between the Tietê River and its direct tributaries (Sorocaba River, Capivari River, and Peixe River), due to the water pollution of the main river. The study was based on the fish community's inventories through gillnets, their ecological attributes, and the simultaneous determination of limnological variables, during late rainy (April 2019) and dry seasons (October 2019). For both sampling periods, the Principal Component Analysis (PCA) showed a clear difference in the water quality of the main river (worst condition) compared to the tributaries (better condition). This difference was also evidenced through the nMDS based on the composition of the rivers' ichthyofauna, with a much higher species diversity in the tributaries (11 to 14 spp.) compared to the Tietê River (3 to 4 spp.). The DistLM analysis showed that there is a significant correlation between the limnological variables and the structure of the ichthyofauna only in the rainy season, which can be explained by the marked difference in the environmental conditions, especially during this period. The results show that the pollution effects act as a chemical barrier to the dispersal of sensitive, or less tolerant, organisms and demonstrate the urgency of implementing pollution mitigation measures in the Tietê River basin.
Over time, artificial barriers to species dispersal have emerged as a consequence of population growth and the economic development of society. In the case of aquatic environments, it is known that different types of anthropic disturbances can influence this process, with pollution being an important modifying factor for the structuring of the regional biota, especially the ichthyofauna. The Tietê River basin, which has a long history of environmental degradation, exhibits, in its middle section, contrasting environments in terms of water quality. However, these river systems are widely interconnected, without any natural or artificial physical barriers that could interfere with the free movement of the organisms. In this context, the goal of this work was to evaluate the limitations that occur in the process of dispersal of the fish fauna of this basin, between the Tietê River and its direct tributaries (Sorocaba River, Capivari River, and Peixe River), due to the water pollution of the main river. The study was based on the fish community's inventories through gillnets, their ecological attributes, and the simultaneous determination of limnological variables, during late rainy (April 2019) and dry seasons (October 2019). For both sampling periods, the Principal Component Analysis (PCA) showed a clear difference in the water quality of the main river (worst condition) compared to the tributaries (better condition). This difference was also evidenced through the nMDS based on the composition of the rivers' ichthyofauna, with a much higher species diversity in the tributaries (11 to 14 spp.) compared to the Tietê River (3 to 4 spp.). The DistLM analysis showed that there is a significant correlation between the limnological variables and the structure of the ichthyofauna only in the rainy season, which can be explained by the marked difference in the environmental conditions, especially during this period. The results show that the pollution effects act as a chemical barrier to the dispersal of sensitive, or less tolerant, organisms and demonstrate the urgency of implementing pollution mitigation measures in the Tietê River basin.
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Barreira ecológica, Degradação ambiental, Dispersão dos peixes, Poluição das águas, Ecological barrier, Environmental degradation, Fish dispersal, Water pollution