Taxonomical and ecological characteristics of the desmids placoderms in reservoir: analyzing the spatial and temporal distribution

AIM: This study aimed to evaluate the influence of river-dam axis and abiotic factors on the composition of Closteriaceae, Gonatozygaceae, Mesotaeniaceae and Peniaceae in a tropical reservoir METHODS: Water samples for physical, chemical and periphyton analysis were collected in April and August 2002 in different regions along the axis of the river-dam of Rosana Reservoir, River Basin Paranapanema. The substrates collected, always in the litoranea region, were petioles of Eichhornia azurea (Swartz) Kunth. To examine the relationship of abiotic variables with reservoir zones and between the floristic composition of desmids, we used principal component analysis (PCA) and canonical correspondence analysis (CCA RESULTS: The results of the PCA explained 81.3% of the total variability in the first two axes. In the first axis, the variables of conductivity, water temperature and the pH were related to the sampling regions of April with higher values, while for the month of August, nitrate, total phosphorus and dissolved oxygen showed higher values. We identified 20 taxa, distributed in the genera Closterium (14), Gonatozygon (4), Netrium (1) and Penium (1). Spatially, the higher taxa were recorded in the lacustrine region for both collection periods. The canonical correspondence analysis (CCA) summarized 62.2% of total data variability of taxa in the first two axes, and in August, Closterium incurvum Brébisson, C. cornu Ehrenberg ex Ralfs and Gonatozygon monotaenium De Bary, were related to higher values of turbidity and nitrate to the lacustrine and intermediate regions CONCLUSION: Thus, the formation of groups was due to the regions along the longitudinal axis, then the seasonal period, which must be related to the low current velocity, the higher values of temperature and the water transparency, especially in late summer OBJETIVO: Com este trabalho objetivou-se avaliar a influência do eixo rio-barragem e dos fatores abióticos sobre a composição de Closteriaceae, Gonatozygaceae, Mesotaeniaceae e Peniaceae em um reservatório tropical. MÉTODOS: Amostras físicas e químicas da água e de perifíton foram coletadas nos meses de abril e agosto de 2002, em distintas regiões ao longo do eixo rio-barragem do reservatório de Rosana, Bacia do Rio Paranapanema. Os substratos coletados, sempre na região litorânea, foram pecíolos de Eichhornia azurea (Swartz) Kunth. Para analisar a relação das variáveis abióticas com as regiões do reservatório e entre a composição florística d