Lack of correlation between surface macrofauna, meiofauna, erosion threshold and biogeochemical properties of sediments within an intertidal mudflat and mangrove forest

Abstract

This article describes the relationship between 10 selected properties of the sediments (chlorophyll a and b, colloidal and total carbohydrate, water concentration, sediment type, organic matter, erosion threshold and erosion rate) and meio- and macrofauna within and among three different habitats in an urbanized intertidal mudflat/mangrove forest in Tambourine Bay, Sydney Harbour, Australia. Many of the biogeochemical variables were significantly different among habitats, often grading from mudflat to mangrove canopy. In contrast to previous studies, patterns of distribution of macrofauna among habitats were weak. For the meiofauna, only copepods showed any significant difference among habitats, with the greatest numbers in the open mudflat habitat and least under the mangrove canopy. There was a gradient in fauna among the habitats; overall macrofauna abundances were greatest under the mangrove canopy and least on the mudflat, while meiofauna abundance was greatest in the pneumatophore habitat and least under the canopy. Correlations between fauna and properties of sediment were generally weak. When the habitats were analysed separately, some correlations were strengthened but relationships were inconsistent. Thus, while some taxa vary significantly among habitats there was not a strong relationship between biogeochemical properties and either macro- or meiofauna. This suggests that localised factors other than the measured properties of the sediments are driving patterns in fauna at these small scales, which requires further investigation to be unravelled

Structural equation modelling reveals factors regulating surface sediment organic carbon content and CO2 efflux in a subtropical mangrove

“…The increase of sediment water content with the density of crab burrows in our study is in agreement with a study in Argentina, probably due to the bioturbation effect of crabs of loosening sediment structure, increasing hydraulic connectivity, porewater flow, and decreasing sediment firmness (Botto & Iribarne, 2000;Call et al, 2015;Lee, 1999). Estuarine macrobenthos, including crabs, appear to be more abundant in sediment rich in organic matter (Tolhurst et al, 2010). Isotopic analyses (δ 13 C) suggested that microphytobenthos were likely one of the food sources of crabs, although mixed C sources were possible, in a mangrove forest in southeast Queensland, Australia (Guest & Connolly, 2004).…”

“…The significantly higher Chl a in mid mangroves than other locations is likely a reflection of shading, which is highest in the flourishing mid forests. The increase in shading is claimed to give rise to microphytobenthic populations (Tolhurst et al, 2010) , due to avoidance of photo−inhibition.…”

Structure and functional characteristics of the meiofauna community in highly unstable intertidal mudbanks in Suriname and French Guiana (North Atlantic coast of South America)

“…Finally, meiofauna uses only a negligible part of carbon from primary production (Middelburg et al, 2000;Moens et al, 2002;Pinckney et al, 2003;Rzeznik-Orignac and Fichet, 2012;van Oevelen et al, 2006).Food availability also does not appear to limit meiofaunal abundance (no top-down control of MPB [Coull, 1999]). Furthermore, Tolhurst et al (2010) did notfind a correlation between meiofauna and Chl a biomass. It appears that further investigations are needed to assess the primary production and meiofauna grazing rates in order to obtain reliable data of carbon flux in benthic ecosystems of the coasts of the Guianas.…”

The Effect of Shading and Nutrient Addition on the Microphytobenthos, Macrofauna, and Biogeochemical Properties of Intertidal Flat Sediments

“…The canopy of mangrove trees can cast deep shade over the substratum. Previous work has shown that intertidal benthic assemblages differ between muddy substratum that is continuously shaded, periodically shaded and nearby unshaded substratum Tolhurst, 2004, 2007;Tolhurst and Chapman, 2007;Kon et al, 2010Kon et al, , 2011Tolhurst et al, 2010). Leaf litter is the largest constituent of mangrove organic matter contributing to food chains (Lee, 2008), the decomposition of which releases nutrients to the ecosystem (Kamruzzaman et al, 2019), although this release is slower in temperate climates compared to tropical ones (Gladstone-Gallagher et al, 2014a).…”