Abstract
The sustainability of mangrove ecosystems requires a knowledge of their spatiotemporal variability as a function of regional properties. The unique coastal ecosystems of the mangrove belt along the coast of the Guianas in South America are influenced by cycles of a massive accretion of mud supplied by the Amazon River and wave induced erosion. This study characterized, for the first time, how benthic infaunal assemblages, as proxies of mechanisms of mangrove resilience, were structured by the natural growth track of Avicennia germinans dominated mangroves in French Guiana. We sampled 4 mobile mud stations and 27 consolidated mud stations distributed over 9 tidal transects from bare to vegetated mudflats colonized by young mangroves during the dry season. We collected a complete dataset of sediment and vegetation variables together with the benthic meso- (>0.25 mm) and macrofauna (>1 mm). We used a combination of eigenvector based multivariate analyses and variance partitioning on this multiple set of variables to identify which environmental variables likely drive the benthic diversity patterns. Mangrove early development increased the alpha and beta diversities of the infaunal communities for the two size classes. A total of 20–30% and 7–12% of the beta diversity are explained by linear and nonlinear spatial variables, respectively. However, 7% to 9% of the variance partioning could be determined by other biotic/abiotic variables, biological interactions or neutral processes, not described here. This study has highlighted the necessity of taking into account mangrove dynamics at suitable spatial scales for benthic biodiversity evaluation and mangrove management or restoration plans.
Highlights
Mangroves are one of the most productive ecosystems along subtropical and tropical coastlines
A remaining part of the beta diversity (7% to 9%) was only defined by nonlinear spatial structures and, not explainable by the variables used in our analysis
Algal mats are known to inhibit copepod larval settlement in other ecosystems [86], we argue that the copepods we observed in greatest abundances at the sediment surface of the early vegetated transects have adapted their grazing activity to concentrate on cyanobacteria [87,88]
Summary
Mangroves are one of the most productive ecosystems along subtropical and tropical coastlines. These systems are threatened by a range of anthropogenic pressures, including deforestation, pollution, and urbanization, and by climate changes, including recurrent. One of the main difficulties for mangrove management and restoration strategies, is the lack of knowledge regarding mangrove ecosystem functioning and its spatial and temporal variabilities. The efficient sustainability of mangroves requires better characterization of these spatial and temporal variabilities as a function of regional characteristics, and in response to the various environmental and anthropogenic pressures that constraint mangrove functioning [9]
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