Taxonomic and functional patterns of fish assemblages in oceanic and estuarine beaches along the Brazilian coast: a latitudinal, regional, and local approach
Biodiversity, functional characteristics, sandy beaches, ichthyofauna
Biodiversity analyses conducted at different spatial scales are essential for understanding the
contribution of large-scale processes to local biodiversity patterns and may elucidate the
connection between local and regional species richness. Regional and historical processes can
influence local communities, and species interactions at the local level can affect the
availability of these species in the regional pool. The use of beaches by young fish constitutes
an important process in the ecology of shallow coastal zones, encompassing the period of use
of different types of beaches by different fish groups during the early life stage or even the
entire life cycle.
The present study aims to investigate processes and patterns of young fish assemblages on
oceanic beaches and estuarine beaches (e.g., bays, estuaries) at three scales: local scale,
focusing on the coast of Rio de Janeiro, in Sepetiba and Ilha Grande Bays, based on primary
data; regional scale (Tropical, Transition, and Warm Temperate zones); and latitudinal scale,
based on information from each location along the coast, from the Amazon estuary to Chuí,
addressing the following themes:
In Chapter 1 (Taxonomic and functional patterns of ß-diversity in coastal fish assemblages on
the Brazilian coast: a latitudinal and regional approach to community assembly), a latitudinal
and regional approach will be undertaken to investigate the importance of niche and neutral
processes in determining the assembly of young fish communities. This involves analyzing the
relationship between taxonomic and functional ß-diversity decomposition separately for
oceanic and estuarine beaches. We hypothesize that the neutral process will be more
important at the latitudinal scale, the niche process will be more important at the regional
scale (Transition and Warm Temperate), and the neutral process will be more important in the
tropical zone due to the presence of different marine currents. We also hypothesize that these
patterns may vary between the analyzed sandy beach environments, with estuarine beaches
prevailing in local environmental forces and gradients, unlike oceanic beaches with less
defined environmental gradients.
In Chapter 2 (Characteristic-environment relationship of coastal fish assemblages in a
latitudinal approach), relationships between the occurrence of fish species, their functional
characteristics, and environmental variables were evaluated on a latitudinal scale on oceanic
and estuarine beaches along the Brazilian coast. The hypothesis tested is that the functional
characteristics of fish and environmental variables will not be randomly distributed between
oceanic and estuarine beaches on a latitudinal scale.
In Chapter 3 (Use of different types of beaches by young fish assemblages in two large bay
systems, Sepetiba and Ilha Grande, in the state of Rio de Janeiro), the structure of the
ichthyofauna was evaluated and compared between the two bays and the spatial gradient
within each bay (continental beaches, beaches on islands near the continent, and beaches on
larger and distant islands). The hypothesis tested is that the structure of the ichthyofauna will
differ between the two bays due to their different hydrological and environmental
characteristics, and there will be a spatial gradient (continental beaches, beaches on islands
near the continent, and beaches on larger and distant islands) in each bay conditioning the
structure of the communities.