Abyssal food-web model indicates faunal carbon flow recovery and impaired microbial loop 26 years after a sediment disturbance experiment

Due to the predicted future demand for critical metals, abyssal plains covered with polymetallic nodules are currently being prospected for deep-seabed mining. Deep-seabed mining will lead to significant sediment disturbance over large spatial scales and for extended periods of time. The environmental impact of a small-scale sediment disturbance was studied during the ‘DISturbance and reCOLonization’ (DISCOL) experiment in the Peru Basin in 1989 when 10.8 km2 of seafloor were ploughed with a plough harrow. Here, we present a detailed description of carbon-based food-web models constructed from various datasets collected in 2015, 26 years after the experiment. Detailed observations of the benthic food web were made at three distinct sites: inside 26-year old plough tracks (IPT, subjected to direct impact from ploughing), outside the plough tracks (OPT, exposed to settling of resuspended sediment), and at reference sites (REF, no impact). The observations were used to develop highly-resolved food-web models for each site that quantified the carbon (C) fluxes between biotic (ranging from prokaryotes to various functional groups in meio-, macro-, and megafauna) and abiotic (e.g. detritus) compartments. The model outputs were used to estimate total system throughput, i.e., the sum of all C flows in the food web (the ‘ecological size’ of the system), and microbial loop functioning, i.e., the C-cycling through the prokaryotic compartment for each site. Both the estimated total system throughput and the microbial loop cycling were significantly reduced (by 16% and 35%, respectively) inside the plough tracks compared to the other two sites. Site differences in modelled faunal respiration varied among the different faunal compartments. Overall, modelled faunal respiration appeared to have recovered to, or exceeded reference values after 26-years. The model results indicate that food-web functioning, and especially the microbial loop, have not recovered from the disturbance that was inflicted on the abyssal site 26 years ago

Data presented in the paper: Is summer growth reduction related to feeding guild? A test for a benthic juvenile flatfish sole (Solea solea) in a temperate coastal area, the western Wadden Sea

Growth performance was analyzed by combining information on individual growth based on otolith daily ring analysis with predictions of maximum growth (= under optimal food conditions) based on a Dynamic Energy Budget model. This research is a combination of collected field data, otolith microstructure analysis and the theoretical growth was calculated by means of four DEB model equations based on the Von Bertalanffy growth model. The enclosed data consist of the collected field data, calculated theoretical growth over time, and calculated realized growth (RG, dimensionless), defined as the ratio between observed size and DEB-predicted maximum size under optimal food conditions

Carbon and nitrogen turnover during a mesocosm experiment with addition of Palmaria decipiens and Desmarestia anceps to sediments from Potter Cove

To understand the fate of the increasing amount of macroalgal detritus in Antarctic shallow subtidal sediments, a mesocosm experiment was conducted to track 13C and 15N labelled macroalgal detritus into the benthic bacterial, meio- and macrofaunal biomass and respiration of sediments from Potter Cove (King George Island). We compared the degradation pathways of two macroalgae species: one considered palatable for herbivores (the red algae Palmaria decipiens), and one considered non-palatable for herbivores (the brown algae Desmarestia anceps). 15 sediment cores were taken from station Faro at 20m water depth. 13C and 15N labelled macroalgae were added to 10 cores: 5 cores received Desmarestia anceps, 5 cores received Palmaria decipiens. 5 cores did not receive any macroalgae and acted as a control. At different points in time, the cores were closed airtight for a dark incubation of 12h, during which oxygen was measured to calculate Total Oxygen Uptake (TOU), next to 13C-DIC, total nutrients and 15N-labelled nutrients (NH4, NOx and N2). The next day, the cores were sacrificed to determine the assimilation of macroalgae detritus in bacteria, microphytobenthos, meiofauna, macrofauna. Also the remaining large (>1mm) macroalgae fragments were recovered and the bulk POC and PN of the sediment was measured. The sampling points are 1d after addition, and 7, 14 and 21 and 26 days after addition of macroalgae detritus