Resumo:
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.
