Abstract
Changes of the plankton community in a shallow, subtropical lagoonal system and its relation to environmental conditions were investigated during an annual cycle to provide information on its spatial and seasonal variation pattern. The study carried out at four sites (three in the Peixe lagoon and one in the Ruivo lagoon), which are located in the Lagoa do Peixe National Park, southern Brazil. The system has a temporary connection to the Atlantic Ocean by a narrow channel. The phytoplankton density was higher in the Peixe lagoon whereas the specific richness was higher in the Ruivo lagoon which is also a site with the lower salinity. The phytoplankton biomass near the channel showed seasonal variation with the highest value in fall and lowest in winter. Zooplankton richness was inversely correlated with salinity, and had the highest values in the Ruivo lagoon. Ordination analysis indicated seasonal and spatial patterns in plankton community in this lagoonal system, related to variation in salinity. In addition, the wind action and precipitation were important factors on the spatial and seasonal salinity changes in the lagoon with direct influence on the plankton community dynamics.
Highlights
The management of the park is under the direction of the Chico Mendes Institute for Biodiversity Conservation (ICMbio, Instituto Chico Mendes de Conservação da Biodiversidade) and the municipalities of Mostardas and Tavares
The Peixe and Ruivo lagoons are dynamic systems strongly influenced by salinity fluctuations due to precipitation and evaporation in the area, freshwater inflow from the adjacent wetland and farms, and seawater introduction through removal of the sand bar that divides the lagoon from the ocean
The Peixe lagoon was more saline in summer, which is to be expected in these shallow systems due to higher temperature and evaporation
Summary
Spatial and seasonal heterogeneity of phytoplankton are regular features in coastal lagoons in different parts of the world, and has been the focus of studies in temperate (Armi et al 2010, Chapman et al 1998, Ramdani et al 2009), tropical (Melo and Suzuki 1998, Melo et al 2007, Varona-Cordero et al 2010), and subtropical zones (Bergesch and Odebrecht 1987, Callegaro et al 1981, Conde and Sommaruga 1999, Odebrecht and Abreu 1998, Odebrecht et al 2010a, Torgan 1997, Torgan et al 2000, 2006). Spatial variation in species composition occurred due to changes in salinity and nutrients, caused by the opening and closing of channels (Melo and Suzuki 1998, Melo et al 2007) or other environmental variables, mainly salinity (Varona-Cordero et al 2010)
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