Amazon River discharge impacts deep‐sea meiofauna

Abstract

In this study, we show that the deep‐sea meiofauna community at the Brazilian Equatorial Margin (BEM) is strongly influenced by the Amazon River. Our comparison across four deep ocean basins including Amazon, Pará‐Maranhão, Barreirinhas, and Ceará showed that the former supports a completely distinct meiofaunal community. Meiofaunal richness increased with increasing distance from the Amazon, reflecting changes in sediment proprieties among basins. Total phytopigment content at Amazon sediments was threefold higher than at other basins. The chlorophyll a/Phaeo mean ratio, however, was lower than 1, suggesting a predominant degraded bulk organic matter derived from the Amazon River discharge. Nematode assemblages from Amazon strongly differed from the other basins mostly due to higher genus richness, trophic diversity, and variations in the abundance of Sabatieria, which in turn led into higher dissimilarity values and turnover rate. Furthermore, the bathymetric distribution of nematode assemblages at Amazon and Ceará basins differed significantly among depth zones, especially due to the higher abundance and diversity at Amazon basin. Our findings show that the Amazon River plays a critical role in structuring and shaping the deep‐sea meiofauna and nematode biodiversity at the BEM. Increasing impacts on the Amazon rainforest will certainly affect the amount of freshwater discharge, and the quantity and quality of organic material transported to the Atlantic Ocean, which in turn will have effects on the deep‐sea communities.

Nematode communities along a bathymetric transect in the deep eastern Fram Strait (Arctic Ocean): interrelations between diversity, function and environment

“…In some cases, a more linear decrease in diversity with depth (Trebukhova et al, 2013;Grzelak et al, 2017), no correlation between diversity and depth (Danovaro et al, 2009;Armenteros et al, 2022) or even an increase in diversity with depth (dos Santos et al, 2020) have been reported. Hydrodynamic regimes at local scales that regulate the food availability for meiobenthos have been discussed as one of the drivers behind this phenomenon (dos Santos et al, 2020;Pereira et al, 2022). Apart from the more linear decline in diversity and the use of Hill diversity (Hill, 1973) instead of Shannon diversity by Grzelak et al (2017), the magnitude of the decline of the different indices is comparable to our results.…”

Sunken trees in the deep sea link terrestrial and marine biodiversity

“…Markedly, deep‐sea ecosystems are linked to terrestrial systems. Major river sheds can significantly increase carbon input into the deep oceans (Schlünz & Schneider, 2000) affecting biodiversity (Pereira, Castellões, & Netto, 2022). The deep sea is also connected to terrestrial systems by a wooden pathway through which anthropogenic impacts on land can alter the deep oceans (McClain et al, 2016; McClain & Barry, 2014; Turner, 1973; Voight, 2007).…”