Spatial and seasonal changes in benthic macrofauna from two dissipative sandy beaches in eastern Brazil)

Abstract

Sandy beaches are dynamic ecosystems with strong interaction of sediments, waves and tidal energy, with marked effects on benthic assemblages. Although there are numerous efforts in understanding spatial-temporal variation of benthic macrofauna on sandy beaches along the southern and southeastern Marine Ecoregions in Brazil, there is poor sampling along beaches of the Eastern Marine Ecoregion (EME). Here we examined spatial and temporal scales of variability in benthic macrofauna (> 500 µm) through a hierarchical sampling of two dissipative sandy beaches within the EME between two seasons (winter 2011 and summer 2012). We tested the hypothesis that spatial changes (i.e., meters to hundreds of meters scales) in the structure of benthic assemblages will be more pronounced compared to the weak seasonal fluctuations at this tropical region. We found weak temporal and spatial changes in sediment grain size and beach slope, but differences in macrofaunal assemblages were evident. Contrary to our hypothesis, hierarchical sampling indicated significant changes in macrofaunal composition and density at multiple local scales (meters to hundreds of meters) and on seasonal scales. The macrofauna density and composition was directly related to changes on the sediment organic matter and grain size.

Do natural disturbances have significant effects on sandy beach macrofauna of Southeastern Brazil?

“…The lack of variability in the community richness and density between dry and rainy periods means that assemblage structure is relatively stable over time, with shifts exclusively in species association patterns. This corroborates with the results of other studies in southeastern Brazil, where environmental seasonality is not pronounced Cardoso 2001, Coutinho andBernardino 2017). Oppositely, at temperate and subtropical regions temporal changes on macrofauna structure is usually significant (Leber 1982, Neves et al 2007.…”

Macroinfauna Intermareal Das Praias Arenosas Do Litoral De Aracaju, Sergipe, Região Nordeste Do Brasil = Intertidal Macroinfauna of the Aracaju Sandy Beaches, Sergipe, Northeastern Brazil

“…Contrariando as expectativas de um gradiente latitudinal, o número de espécies registrados nas praias de Aracaju (11°S) não foi maior do que os registrados para praias dissipativas das regiões sudeste e sul do litoral brasileiro. Aqui, considerandose as quatro praias juntas, foi registrado um total de 20 espécies, enquanto que, no litoral do Espírito Santo (19°S) foi registrado um total de 35 espécies (Coutinho & Bernardino, 2017). Já no litoral carioca (22°S), Andrade et al (2016) registraram uma riqueza variando de 19 a 24 espécies.…”

“…Por outro lado, os valores de densidade da macrofauna (entre 65 e 170 ind./m²) nas praias de Aracaju foram extremamente baixos quando comparados aos observados em outras praias das regiões sudeste e sul do Brasil, corroborando com o padrão latitudinal previsto. Valores de densidades (entre 7500 e 21000 ind./m²) registrados no litoral do Espírito Santo (Coutinho & Bernardino, 2017) foram mais de 100 vezes superiores aos registrados em Sergipe. O mesmo se observa para o litoral do Paraná, onde valores médios de densidade giram em torno de 22000 indivíduos/m² (Souza & Gianuca, 1995).…”

Relationships between benthic infauna and groundwater eutrophication on a sandy beach in southern Brazil

“…At a local scale, seasonal variation in the sandy beach morphodynamic can rapidly change the population dynamic of organisms in the benthic community (Defeo et al 2009; Cisneros et al 2011), which is involved in various ecological functions at multiple trophic levels, such as breaking down organic material in the sediment, substrate aeration, nutrient cycling and transferring energy to animals that feed on them (e.g., birds, reptiles and sh) (Campanyà-Llovet et al 2017). Further, these organisms are sensitive to environmental changes, since they have sessile or sedentary habits, and can be used as bioindicators when evaluating impacts caused by many human activities in aquatic environments (Coutinho and Bernardino 2017).…”