Cristina Stenert

Environmental predictors of macroinvertebrate communities in coastal wetlands of southern Brazil

The rapid degradation of wetlands worldwide accentuates the urgent need for ecological data to help manage and protect the threatened biodiversity in the remaining often-fragmented wetlands. In the Neotropics where fragmentation is common, environmental factors structuring aquatic macroinvertebrate communities are poorly known. We tested the hypothesis that physical features, such as wetland area, habitat diversity, water depth and temperature, and water and sediment chemistry are important correlates with richness, density and composition of wetland macroinvertebrate assemblages in Brazil. If so, do these correlations differ between summer and winter? A total of 16 895 individuals across 61 families were collected. Richness was positively associated with habitat diversity and water depth and negatively associated with water temperature. Macroinvertebrate density was negatively associated with water depth, and positively correlated with habitat diversity, percentage of sediment organic matter and water conductivity. Macroinvertebrate composition was associated mainly with wetland area and habitat diversity in the wetlands studied; these relationships persisted in both seasons. Our data illustrate environmental factors that potentially structure and maintain aquatic macroinvertebrate biodiversity in southern Brazil wetlands, and should be managed because 90% of these ecosystems have already been lost as a result of human activities.

Influence of area, altitude and hydroperiod on macroinvertebrate communities in southern Brazil wetlands

Wetlands are important ecosystems in southern Brazil because they show high productivity and biological diversity. However, conservative data indicate that ~90% of the wetlands have disappeared as a result of agricultural expansion. In this sense, the understanding of species composition and richness patterns in fragmented and natural wetlands is a priority for biodiversity conservation strategies. The main goal of the present study was to determine how much variation in macroinvertebrate richness and composition is explained by wetland area, hydroperiod and altitude. This survey was carried out in an extensive area of the Neotropical region (~280000 km2 – southern Brazil) with a large number of wetland systems (72) and covering a wide gradient of altitude and wetland surface area. The macroinvertebrate richness was higher in permanent wetlands than intermittent ones, and intermittent wetlands supported a macroinvertebrate composition that clearly differed from those of permanent wetlands. Macroinvertebrate richness was positively affected by wetland area; however, this relationship was significant only in permanent wetlands. There is a need to promote conservation of all wetland systems in southern Brazil, regardless of their hydroperiod and area. These arguments are essential to develop conservation and management programs of wetlands in this region.

Species-area relationship and environmental predictors of fish communities in coastal freshwater wetlands of southern Brazil

In the Neotropics where fragmentation is common, environmental factors structuring fish communities are poorly known. In this study two hypotheses were tested in 13 coastal wetlands of southern Brazil: 1) physical features (such as wetland area, habitat diversity, water depth and temperature, and water and sediment chemistry) are important determinants of richness, density and composition of fish assemblages; and 2) species richness and composition of fish assemblages differ between wetlands with different hydroperiods (i.e. permanent versus intermittent). A total of 1,597 individuals distributed among 20 species were collected. Richness was positively associated with wetland area and water depth and it was negatively associated with water conductivity. The species-area power function explained 27.3% of the variation in richness. Fish richness was similar between permanent and intermittent wetlands. The density was negatively associated with water depth and temperature, and it was positively correlated with water nitrate concentration. The first three axes from the CCA accounted for 55.5% of total variation in fish composition. The most important variables related to fish composition were percentage of sediment organic matter, phosphorus concentration, habitat diversity and water depth. Composition of fish species changed among permanent and intermittent wetlands. Understanding the environmental factors that shape and maintain the biodiversity in these ecosystems is essential to develop conservation and management programs of wetlands in this region, where more than 90% of wetland systems have already been lost due to anthropogenic activities.

Diversity and Distribution of Chironomid Larvae in Wetlands in Southern Brazil

Abstract Chironomidae is a cosmopolitan family of dipteran insects occurring in all zoogeographical regions of the world. The family is quite diverse and the objective of this study was to examine diversity of chironomid larvae in 115 wetlands in an extensive area of Neotropical region (∼220,000 km2, southern Brazil) by analysis of richness and composition in different wetland subsystems, types and classes. Also examined were effects of wetland area, altitude, water conductivity and nutrients on these community descriptors. A total of 36 genera was found, with Chironominae showing the greatest richness, followed by Tanypodinae and Orthocladiinae. The richness and composition changed between wetland subsystems, types and classes. However, no single parameter strongly influenced the chironomid richness and composition in this broad spatial scale survey. The broad spatial scale and details of this study make it an important contribution to knowledge of chironomid diversity in the Neotropical region.

Responses of freshwater molluscs to environmental factors in Southern Brazil wetlands

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 (approximately 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.

Development of a multimetric index based on aquatic macroinvertebrate communities to assess water quality of rice fields in southern Brazil

In the last decade, dozens of indices based on macroinvertebrates were developed to evaluate lotic ecosystems. In contrast, very few of these indices have been applied in lentic ecosystems. Natural wetlands in southern Brazil are increasingly threatened by the expansion of irrigated rice. The main objective of this study was to develop a multimetric index based on macroinvertebrates to evaluate the water quality of natural wetlands and rice fields in southern Brazil. Three samplings were carried out over the rice growth cycle in four conventional and four biodynamic rice fields, and four natural wetlands. The wetlands were considered as reference sites, and the conventional and biodynamic rice crops were considered as manipulated sites at different levels of degradation. Seven metrics were included in the final index after passing though sensitivity and correlation tests. The results indicated that our index has a power to detect a gradient of variation in water quality. Natural wetlands had the best water quality, biodynamic crops had intermediate water quality, and the conventional crops had the lowest water quality. We believe that development of this macroinvertebrate-based multimetric index of water quality could be an important tool for monitoring natural wetlands and rice crops in southern Brazil.

Does Non-Intentional Flooding of Rice Fields After Cultivation Contribute to Waterbird Conservation in Southern Brazil?

Abstract.— Use of rice fields as complementary habitats to waterbird species was investigated. Three questions were posed (1) does waterbird richness (defined as number of species), abundance and composition differ between rice fields and natural wetlands; (2) do richness, abundance and composition of waterbird species differ between flooded and drained rice fields in the post-harvest season, and (3) do richness, abundance and composition of waterbird species change in rice fields over the rice cultivation cycle? Eight collections were made in eight rice fields with different hydrological conditions after cultivation (four dry and four flooded) and four natural wetlands. Waterbirds were censused using binoculars and one telescope. A total of 76 waterbird species were observed during the study period (2005–2006): 59 species in rice fields and 70 species in natural wetlands. The richness of waterbirds was higher in natural wetlands than flooded and drained rice fields; however, there was no difference between flooded and drained rice fields. The richness of waterbirds did not change over the rice cultivation cycle. Waterbird abundance was higher in natural wetlands than in flooded and drained rice fields. Natural wetlands showed a seasonal pattern of species composition and abundance different from rice fields. Rice fields are used for an important fraction of the waterbird richness in southern Brazil, acting as habitat complementary for biodiversity, but in lower richness and abundance when compared to natural wetlands. The non-intentional flooding of rice fields did not contribute towards waterbird conservation in southern Brazil.

Diversity of chironomid larvae in palustrine wetlands of the coastal plain in the south of Brazil

The Chironomidae of tropical South America are a very rich species, but are scarcely known. The range of environmental conditions under which chironomids are found is more extensive than that of any other group of aquatic insects. The objectives of this study were to carry out a diversity survey of chironomid larvae in wetland systems of the coastal plain in the south of Brazil and to analyze the effects of area, altitude, water conductivity, nitrate and phosphorus concentrations, and the life form of the dominant plant species on chironomid richness and composition. Collections were carried out from March to April in 2002. A total of 30 taxa (23 morphospecies and 7 species) distributed along 23 genera were found, and the Chironominae showed the greatest richness, followed by Tanypodinae and Orthocladiinae. The chironomid richness was higher in the emergent than in the multistratified wetland class. The wetland area, altitude, nitrate and phosphorus concentrations, and water conductivity did not influence the richness of Chironomidae. The Chironomidae genera and species were present in both the wetland classes (emergent and aquatic bed vegetation). However, while Chironominae were more frequent in the emergent than in the aquatic bed wetlands, no difference was observed for Tanypodinae. The aquatic vegetation was an important environmental predictor for chironomid larvae richness in the studied wetlands in the south of Brazil.

Responses of Odonate Communities to Environmental Factors in Southern Brazil Wetlands

Abstract Odonate larvae play an important role in wetland systems, providing food for many fish species and birds. Besides, they are important predators in these ecosystems. However, studies of factors that determine odonate species richness and distribution in wetlands are scarce in the Neotropical region. The objectives of this study were to: 1) conduct a survey of the diversity of odonate larvae in southern Brazil wetlands, and 2) determine how much variation in odonate richness, abundance and composition is explained by wetland area, altitude, water conductivity and nitrate, hydroperiod, and dominant aquatic vegetation in 140 wetlands in an extensive area of the Neotropical region (~280,000 km2, southern Brazil). A total of 4,039 individuals distributed among five families and 28 genera were collected. Libellulidae, Coenagrionidae and Aeshnidae were the families that showed the greatest richness. Erythrodiplax was observed in more than 70% of the sampled wetlands, and comprised 61% of individuals collected. Richness was negatively associated with wetland area and nitrate concentration. Odonate abundance was negatively associated with water conductivity and nitrate, and it was higher in aquatic beds than in emergent wetlands. Richness and abundance were higher in permanent than in intermittent wetlands. Variation in odonate composition was correlated with wetland altitude, area and water conductivity. Hydroperiod and dominant aquatic vegetation also influenced composition. Our results showed that southern Brazil wetlands are important habitats for 28 odonate genera, and that richness, abundance and composition are influenced mainly by hydroperiod, nitrate, and aquatic vegetation type. These results should be seen as important to determine the environmental factors that shape and maintain odonate diversity in southern Brazil wetlands.

Aquatic macrophyte and macroinvertebrate diversity and conservation in wetlands of the Sinos River basin

Wetlands are important sites for biological conservation because they support rich biodiversity and present high productivity. Species-area relationship is an important tool in conservation planning and it has been extensively used for wetland management. This study had as aims: (1) to analyse macrophyte and macroinvertebrate diversity in the fragmented wetlands of the Sinos River basin; and (2) to investigate whether wetland areas could work as a tool for selecting the important habitats for biodiversity conservation. Throughout the study, 56 species of macrophytes and 57 taxa of macroinvertebrates were identified. Macrophyte richness was related to the wetland area, but macroinvertebrate richness, however, was not related to the wetland area. The macrophyte and macroinvertebrate composition were not related to the wetland area. Species composition varied between the regions of the basin and the difference in the species composition occurred mainly by the distribution of macroinvertebrates. With regard to the biodiversity conservation of the Sinos River basin, the wetland area must not be a priority criterion for choosing the important wetlands for conservation. The environmental policies for biodiversity conservation must include management actions focused also on the protection of small wetlands. Moreover, other criteria should be analysed in further research such as habitat diversity, hydroperiod, geographic distribution and connectivity.