Macrofauna as a major driver of bentho‐pelagic exchange in the southern North Sea

Abstract

The contribution of sediments to nutrient cycling of the coastal North Sea is strongly controlled by the intensity of fluxes across the sediment water interface. Pore‐water advection is one major exchange mechanism that is well described by models, as it is determined by physical parameters. In contrast, biotransport (i.e., bioirrigation, bioturbation) as the other major transport mechanism is much more complex. Observational data reflecting biotransport, from the German Bight for example, is scarce. We sampled the major sediment provinces of the German Bight repeatedly over the years from 2013 to 2019. By employing ex situ whole core incubations, we established the seasonal and spatial variability of macrofauna‐sustained benthic fluxes of oxygen and nutrients. A multivariate, partial least squares analysis identified faunal activity, in specifically bioturbation and bioirrigation, alongside temperature, as the most important drivers of oxygen and nutrient fluxes. Their combined effect explained 63% of the observed variability in oxygen fluxes, and 36–48% of variability in nutrient fluxes. Additional 10% of the observed variability of fluxes were explained by sediment type and the availability of plankton biomass. Based on our extrapolation by sediment provinces, we conclude that pore‐water advection and macrofaunal activity contributed equally to the total benthic oxygen uptake in the German Bight.

Assessment of Benthic Ecological Quality Status Using Multi-Biotic Indices Based on Macrofaunal Assemblages in a Semi-Enclosed Bay

“…Multi-biotic indices were significantly or highly significantly correlated with pH, organic matter, sediment salinity, and Chl-a content, suggesting that the marine benthic environment is related to pH, and nutrients, which is similar to other studies (Oleszczuk et al, 2021;Toussaint et al, 2021). In the study by Neumann et al (2021), bioturbation and temperature had the highest explanatory power to explain the substantial seasonal variability in observed oxygen and nutrients. The total organic matter content is an important environmental variable for anoxic mineralization (Toussaint et al, 2021).…”

“…The effect of temperature on macrofaunal diversity was also significant in this study, with winter macrofaunal diversity being significantly lower than in other seasons. A number of investigations have concluded that macrofaunal abundance has a highly significant positive correlation with bottom temperature (Shojaei et al, 2015;Neumann et al, 2021), especially in semienclosed bays, which may be related to the drastic changes in bottom temperature (Yang et al, 2021). Multi-biotic indices were significantly or highly significantly correlated with pH, organic matter, sediment salinity, and Chl-a content, suggesting that the marine benthic environment is related to pH, and nutrients, which is similar to other studies (Oleszczuk et al, 2021;Toussaint et al, 2021).…”

Quantifying Importance of Macrobenthos for Benthic‐Pelagic Coupling in a Temperate Coastal Shelf Sea

“…Further elucidation of the tracer experiments is provided in Supporting Information S1. Full details of the incubation method and results are presented byNeumann et al (2021).…”

Benthic alkalinity fluxes from coastal sediments of the Baltic and North seas: comparing approaches and identifying knowledge gaps

“…Aerobic remineraliza-B. Van Dam et al: Benthic alkalinity fluxes from coastal sediments of the Baltic and North seas tion is a key DIC source in physically or biologically ventilated surface sediments (Neumann et al, 2021;Rassmann et al, 2020), followed by microbial sulfate reduction (MSR; Al-Raei et al, 2009). These DIC sources may be further enhanced to varying extents by anaerobic processes like denitrification, as well as iron and manganese reduction, which, like MSR, also produce TA and DIC (e.g., Zeebe and Wolf-Galdrow, 2001).…”

“…For example, large tidal forcing combined with coarsegrained sediments in the southern North Sea could promote advective over diffusive fluxes and increase the oxygen penetration depth (Billerbeck et al, 2006;Al-Raei et al, 2009). Bioturbation and bioirrigation are also especially important in the coastal North Sea and can explain how sediment-water fluxes of oxygen and other elements vary across season and sediment type (Lipka et al, 2018;Gogina et al, 2018;Neumann et al, 2021;Bratek et al, 2020). In contrast, limited tidal forcing combined with finer-grained sediments in the western Baltic Sea could promote stronger biogeochemical zonation and a greater importance of anaerobic over aerobic processes (Böttcher et al, 2000).…”