Responses of freshwater molluscs to environmental factors in Southern Brazil wetlands

Abstract

Freshwater molluscs play an important role in aquatic ecosystems, providing food for many fish species and vertebrates. Investigations on factors that determine mollusc species richness and distribution in wetland systems are scarce in the Neotropical region. The main goal of this study was to determine how much variation in mollusc richness and composition is explained by area, hydroperiod, altitude, water conductivity, and dominant aquatic vegetation. This survey was performed in an extensive area of a Neotropical region (~280,000 km 2 in southern Brazil), with a large number of wetland systems (111) and covering a wide gradient of altitude and wetland surface area. The mollusc richness was positively associated with wetland area and negatively associated with altitude. The richness and composition of the freshwater molluscs were similar between permanent and intermittent wetlands and it did not differ significantly between aquatic bed and emergent wetlands. The first three axes of CCA explained 16.2% of the total variation in the composition of the freshwater mollusc observed. The variation in the composition had a correlation with wetland area, altitude and water conductivity. Our results showed that the wetlands are important habitats for molluscs in southern Brazil, and that the richness and the composition of molluscs were associated with area, altitude, water conductivity and dominant vegetation.Keywords: wetland area, altitude, hydroperiod, aquatic vegetation, neotropical region. Respostas de moluscos límnicos a fatores ambientais em áreas úmidas do sul do Brasil ResumoMoluscos límnicos desempenham um papel importante em ecossistemas aquáticos, fornecendo alimento para diversos peixes e vertebrados. Investigações sobre os fatores que determinam a riqueza e a distribuição das espécies de moluscos em áreas úmidas são escassos na região neotropical. O principal objetivo deste estudo foi determinar a variação na riqueza e na composição de moluscos em função da área, hidroperíodo, altitude, condutividade da água e tipo de vegetação aquática dominante. Este estudo foi desenvolvido em uma extensa área Neotropical (~280.000 km 2 no sul do Brasil), com um elevado número de áreas úmidas (111) e compreendeu um amplo gradiente de altitude e tamanho de áreas úmidas. A riqueza de moluscos foi positivamente relacionada com o tamanho da área úmida e negativamente relacionada com a altitude. A riqueza e a composição de moluscos foram similares entre áreas úmidas permanentes e intermitentes e não diferiram significativamente entre áreas úmidas herbáceas e emergentes. Os três primeiros eixos da CCA explicaram 16,2% da variação na composição de moluscos. A variação na composição foi correlacionada com a área, altitude e condutividade da água. Nossos resultados mostraram que as áreas úmidas são ecossistemas importantes para os moluscos límnicos no sul do Brasil e que a riqueza e a composição de moluscos estiveram relacionadas à área, altitude, condutividade da água e tipo de vegetação aquática dominante.Palavras-cha...

Mollusks (Gastropoda and Bivalvia) of the Multiple-Use Reserve Martín García Island, Río de la Plata River: biodiversity and ecology

“…Because the temperature of the air and the concentration of dissolved solids contained redundant information (inflation factors >20), these parameters were not considered in the analysis (Ter Braak, 1986;Ter Braak and Verdonschot, 1995;Külköylüoğlu, 2003;2005;Külköylüoğlu and Dügel, 2004;Maltchik et al,2010). The mean value of each environmental variable together with data on the species abundance from eight sampling stations were used in the CCA (Kovach, 1998).…”

Environmental influences on the composition and structure of the freshwater mussels in shallow lakes in the Cuiabá River floodplain

“…In southern Brazil, Mansur et al (1991) and Pereira et al (2000) recorded, respectively, 13 native bivalve species (nine occurring in lakes and 11 in lotic environments) and 19 species, of which only six occurred in lentic environments such as those of the present study. Maltchik et al (2010) recorded only bivalve's species of the Sphaeriidae for wetlands of this region. Our results indicate that the structure of the bivalve assemblages in the lakes of the Cuiabá floodplain was determined by characteristics of the bottom and that there was an interaction between the factors of organic matter and sediment granulometry, which confirms some of the findings reported by other authors (Strayer, 1993;Layzer and Madison, 1995;McRae et al, 2004).…”

“…The variables of ecological importance in the substratum include the physical structure (granulometric composition), organic content, stability and heterogeneity (Callisto and Esteves, 1996). Factors such as dissolved oxygen, hydrogen potential (pH) (McMahon, 1991), water conductivity and hydroperiod (Maltchik et al, 2010) may also be involved in the distribution of bivalves. The limitation of many bivalves to shallow habitats, when in lentic waters, is related to their low tolerance to hypoxia (Burky, 1983).…”

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“…However, some studies have revealed toxicity of most substances is affected by such factors as DO, water hardness and pH (Økland, 1990;Duft et al 2007). The comparative studies in aquatic molluscs have revealed that species' distributions are restricted by environmental conditions (Hunter, 1961;Økland, 1969;Dussart, 1976, Dillon, 2000Maltchik et al 2010;Zeybek et al 2012). As some are edible, many being agricultural pests or hosts to parasitic organisms, they have parasitological importance (Şeşen and Yıldırım.…”