Seasonal recruitment of the hydroid Podocoryna loyola (Hydractiniidae) in the Paranaguá Bay, South of Brazil

Knowledge about the seasonal patterns of recruitment and growth of a non-native species is a precondition to forecast its effect on the native community. The aim of this study was to analyse the seasonality of the hydrozoan Podocoryna loyola, a possible non-native hydroid species in southern Brazilian estuaries, on sets of polyethylene plates, submerged every three months over four years (April 2009 to April 2013), in the Paranagua Bay. The species' abundance was measured as cover, area and number of colonies. These measures showed the same pattern of variation over the seasonal cycles, with higher values occurring in the warmer seasons. A high percentage of colonies with gonozooids also occurred in the warmer seasons, except in the first year, explaining the reduction in the number and cover of colonies at the beginning of the second year. Atypical salinity conditions in the summer/autumn of the second year may have caused the absence of P. loyola until the spring of the next year. Beyond the influence of temperature and salinity on P. loyola seasonality, negative correlations between bryozoans and the hydroid in warmer seasons indicated a mutual influence on the growth of these sheet-like species over the plates.