Spatio-temporal variation in sediment ecosystem processes and roles of key biota in the Scheldt estuary

Mud, Microbes, and Macrofauna: Seasonal Dynamics of the Iron Biogeochemical Cycle in an Intertidal Mudflat

“…We observed spatial and temporal heterogeneity in both porewater dissolved Fe(II) and highly reactive Fe (Fe HR ) sedimentary pools over the seasonal cycle that are primarily controlled by the master variable, temperature. We infer that changes in temperature influence both animal feeding and irrigational behavior (Esselink and Zwarts, 1989;Kristensen, 2001;Fang et al, 2019) as well as the direct influence of temperature on increased microbial iron oxidation and reduction. The sedimentary microbial communities were relatively stable throughout the seasonal cycle with a major demarcation between surface (0-5 cm) and subsurface sediments (5-10 cm).…”

“…We hypothesize that this change is due to several key biogeochemical processes, which are controlled by the master variable, temperature, over the seasonal cycle. Changes in irrigation rates that likely occur throughout the year (Fang et al, 2019) will have profound effects on the exchange of solutes as well as the control of the pools of sedimentary Fe HR -when irrigational activity increases, concomitant microbial oxygen consuming process, such as microaerobic bacterial iron oxidation and aerobic carbon mineralization increase. When irrigation activity is low, the pools of sedimentary Fe HR are depleted in the winter months.…”

Spatial and temporal variations of sediments in a subtropical microtidal estuary

“…In addition to the direct effect of environmental agents, the influence of benthic organisms on the erosion of fine sediments must be considered (Fang et al, 2019;Hillman et al, 2020). Organisms comprising the microphytobenthos like diatoms, and macrofaunal species like polychaetes secrete mucus that can perform a resistance force against erosion processes, by increasing the cohesion among grains (Fang et al, 2019;Hillman et al, 2020). Bivalves, amphipods and decapod crustaceans, in contrast, tend to destabilize the sediment in the construction of its galleries (Kornman & De Deckere, 1998;Dyer et al, 2000).…”

“…Field measurements in some shallow estuarine zones (e.g. in the Deben estuary-England, Westerschelde estuary-Netherlands, Severn estuary-Great Britain) also show that the erodibility of cohesive sediments depends on its physical properties, such as sediment grain size and apparent density, and on biological variables, such as microphytobenthos and macroalgae sediment stabilization (Widdows et al, 2004;Fang et al, 2019). Thus, the seasonal cycle of erosion and deposition is reinforced by the biological cycles (van der Wal et al, 2010;Fang et al, 2019).…”

Mud, microbes, and macrofauna: seasonal dynamics of the iron biogeochemical cycle in an intertidal mudflat

“…We observed spatial and temporal heterogeneity in both porewater dissolved Fe(II) and 559 highly reactive Fe (FeHR) sedimentary pools over the seasonal cycle that are primarily controlled 560 by the master variable, temperature. We infer that changes in temperature influence both animal 561 feeding and irrigational behavior (Kristensen, 2001;Fang et al, 2019) as well as the direct 562 influence of temperature on increased microbial iron oxidation and reduction. Thus, the timing 563 and spatial extent of macrobiota-microbiota relationships can provide information about the 564 potential increase or decrease of iron biogeochemical transformations in coastal sediments.…”