Metacomunidade fitoplanctônica na Baía de Camamu, Bahia, Brasil

Abstract

The metacommunity theory arose with an interest in investigating how local and regional processes interact in the structure of the community and the importance of environmental and spatial factors in determining this structure. However, this focus has not been addressed in tropical estuarine regions for phytoplankton communities, formed by the main group of primary producers of aquatic ecosystems. Thus, the present study aimed to investigate how environmental filters and spatial predictors influence the structure of the phytoplankton metacommunity of lotic systems that flow into Camamu Bay. For this, we use two complementary approaches, one based on the mechanisms through Redundancy Analysis (pRDA) and the other based on the standards with the application of a hierarchical test called Elements of Metacommunity Structure (EMS). Sampling was carried out in April and October 2013, thus contemplating a dry and a rainy period. The distribution of the ten collection points in the Maraú, Orojó and Serinhaém rivers occurred along the salinity gradient, where qualitative and quantitative samples of phytoplankton were collected; water samples for nutrient analysis: silicate, phosphate, nitrate, ammonia and total nitrogen; and physical-chemical parameters were measured: pH, dissolved oxygen, salinity, temperature and total dissolved solids. The analyses indicated three patterns of metacommunity: Gleasonian, Clementsian and Quasi-nested, with a change in the pattern between the dry and rainy periods. Only the Maraú River exhibited the Gleasonian pattern in both periods. As for the mechanisms, only in the rivers Serinhaém (rainy and dry) and Maraú (rainy) there was a predominance of total variation explained by the shared influence of environmental and spatial predictors. In the Orojó (rainy and dry) and Maraú (dry) rivers, the proportion of variance not explained by the measured variables (waste) was high. Thus, we found that changes in rainfall patterns interfered with the structures of phytoplankton communities, but we cannot infer which variables were important in structuring these communities.