Raised water temperature enhances benthopelagic links via intensified bioturbation and benthos-mediated nutrient cycling

Eilish M Farrell; Andreas Neumann; Jan Beermann; Alexa Wrede

doi:10.7717/peerj.17047

Raised water temperature enhances benthopelagic links via intensified bioturbation and benthos-mediated nutrient cycling

PeerJ. 2024 Feb 28:12:e17047. doi: 10.7717/peerj.17047. eCollection 2024.

Authors

Eilish M Farrell¹, Andreas Neumann², Jan Beermann¹, Alexa Wrede^{1

2

3}

Affiliations

¹ Benthic Ecology, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Bremen, Germany.
² Aquatic Nutrient Cycles, Helmholtz Centre Hereon, Geesthacht, Hamburg, Germany.
³ Shelf Sea System Ecology, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Helgoland, Germany.

Abstract

Sediment reworking by benthic infauna, namely bioturbation, is of pivotal importance in expansive soft-sediment environments such as the Wadden Sea. Bioturbating fauna facilitate ecosystem functions such as bentho-pelagic coupling and sediment nutrient remineralization capacities. Yet, these benthic fauna are expected to be profoundly affected by current observed rising sea temperatures. In order to predict future changes in ecosystem functioning in soft-sediment environments like the Wadden Sea, knowledge on the underlying processes such as sediment reworking, is crucial. Here, we tested how temperature affects bioturbation and its associated ecosystem processes, such as benthic nutrient fluxes and sediment oxygen consumption, using luminophore tracers and sediment incubation cores. We used a controlled mesocosm experiment set-up with key Wadden Sea benthos species: the burrowing polychaetes Arenicola marina and Hediste diversicolor, the bivalve Cerastoderma edule, and the tube-building polychaete Lanice conchilega. The highest bioturbation rates were observed from A. marina, reaching up to 375 cm²yr^-1; followed by H. diversicolor, with 124 cm²yr^-1 being the peak bioturbation rate for the ragworm. Additionally, the sediment reworking activity of A. marina facilitated nearly double the amount of silicate efflux compared to any other species. Arenicola marina and H. diversicolor accordingly facilitated stronger nutrient effluxes under a warmer temperature than L. conchilega and C. edule. The oxygen uptake of A. marina and H. diversicolor within the sediment incubation cores was correspondingly enhanced with a higher temperature. Thus, increases in sea temperatures may initially be beneficial to ecosystem functioning in the Wadden Sea as faunal bioturbation is definitely expedited, leading to a tighter coupling between the sediment and overlying water column. The enhanced bioturbation activity, oxygen consumption, and facilitated nutrient effluxes from these invertebrates themselves, will aid in the ongoing high levels of primary productivity and organic matter production.

Keywords: Ecosystem function; Mesocosm; Mudflat; Sediment reworking; Wadden Sea.

MeSH terms

Animals
Bivalvia / metabolism
Ecosystem*
Geologic Sediments*
Nutrients / metabolism
Polychaeta* / metabolism
Seawater / chemistry
Temperature*

Grants and funding

Jan Beermann was financially supported by the German Federal Agency for Nature Conservation (BfN) (grant number 3519532201). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.