Benthic macrofaunal structure and secondary production in tropical estuaries on the Eastern Marine Ecoregion of Brazil

Abstract

Estuaries are highly productive and support diverse benthic assemblages, but few estimates of benthic production are available for most ecosystems. In tropical estuaries mangroves and tidal flats are typical habitats with high spatial heterogeneity of benthic macrofaunal assemblages. However, accessing differences and similarities of benthic assemblages within estuarine habitats and between regional ecosystems may provide scientific support to management of those ecosystems. Here we studied three tropical estuaries in the Eastern Marine Ecoregion of Brazil to assess the spatial variability of benthic assemblages from vegetated (mangroves) and unvegetated (tidal flats) habitats. A nested sampling design was used to determine spatial scales of variability in benthic macrofaunal density, biomass and secondary production. Habitat differences in benthic assemblage composition, biomass, density and secondary production were significant, but also varied between estuaries. Macrofaunal secondary production differed between estuaries and between tidal flat and mangrove habitats, and those differences were related to the composition of benthic assemblages. High benthic production were associated with tidal flats in estuaries with presumable less human impacts, although benthic assemblages from mangrove sediments had similar production irrespective of human disturbances. Given variable levels of human impacts and predicted climate change effects on tropical estuarine assemblages in Eastern Brazil, our data support the use of benthic secondary production to address long-term changes and improved management of estuaries in Eastern Brazil.

Land use impacts on benthic bioturbation potential and carbon burial in Brazilian mangrove ecosystems

“…Eutrophication in Vitória Bay, as revealed by biogeochemical markers (Hadlich et al ), has likely promoted an increased OC and TN burial rates (Sanders et al ), although the input of urban effluents may stimulate soil C remineralization (Suárez‐Abelenda et al ). We also observed a dense plant biomass in soils of fringe Vitória Bay mangroves (> 6500 g m −2 ; Bissoli and Bernardino ), which is a physiological response of mangrove trees to high nutrient input (McKee et al ). We hypothesize that although microbial soil C remineralization may increase with nitrogen input to these urban mangroves, some eutrophic sites may experience increased OC and TN burial as has been noted in the southern Brazil (Sanders et al ).…”

“…Two estuaries represented pristine conditions (Piraquê‐Açu [PA] and Benevente [BE]) and one is a eutrophic metropolitan estuary (Vitória Bay [VB]; Fig. ) (Bissoli and Bernardino ; Hadlich et al ). The Benevente and Piraquê‐Açu mangrove forests were sampled near the seaward region, whereas the Vitória Bay mangrove forest was sampled in the inner estuary as the seaward forests had been lost due to urbanization.…”

“…Benthic macrofauna (> 500 μ m) were sampled ( N = 120 samples) in each estuary during a campaign from August 2014 to September 2014, with macrofaunal abundance and total biomass (ash‐free dry weight [AFDW]) estimated as in Bissoli and Bernardino (). In summary, benthic macrofaunal assemblages were sampled using a nested spatial design on vegetated (mangrove forests) and unvegetated (tidal flats) habitats in the mesohaline sectors (salinity between 18 and 5) of the three estuaries (ICMBIO sampling permit N 24700‐1).…”

“…In summary, benthic macrofaunal assemblages were sampled using a nested spatial design on vegetated (mangrove forests) and unvegetated (tidal flats) habitats in the mesohaline sectors (salinity between 18 and 5) of the three estuaries (ICMBIO sampling permit N 24700‐1). Fauna samples were taken at the same sites where soil cores were taken along three randomly established sampling plots at each site, parallel to the waterline and separated by tens of meters to maintain independence of replicates (Bissoli and Bernardino ). Three replicate faunal samples were sampled within each plot, at a distance of approximately 1 m from each other using a PVC corer with 15 cm internal diameter (0.0177 m 2 area) to a soil depth of 10 cm.…”

“…Three replicate faunal samples were sampled within each plot, at a distance of approximately 1 m from each other using a PVC corer with 15 cm internal diameter (0.0177 m 2 area) to a soil depth of 10 cm. Faunal samples were preserved in 4% formalin and subsequently washed and sieved through a stacked series of sieves (1, 1.4, 2, 2.8, and 4 mm), sorted in the laboratory and identified to family or order level (Bissoli and Bernardino ).…”