Abstract
Managing coastal ecosystems and preserving socio-ecological functioning require a comprehensive understanding of ecological services provided by resident organisms. Here, we provide novel information on water-filtration activities of endobenthic sandprawns (Callichirus kraussi), which are key ecosystem engineers in South African coasts. We demonstrate experimentally that benthic engineering by sandprawns reduces phytoplankton biomass by roughly 50%. Using long-term estuarine data, we demonstrate similar reductions in phytoplankton biomass (by roughly 70%) in sandprawn-dominated areas. Increased burrow wall chlorophyll-a relative to surface sediments that was evident in experiments suggests that pelagic filtration occurs through bi-directional water pumping and phytoplankton adsorption onto burrow walls. Our findings expand understanding of the ecological relevance of sandprawns and functionally similar organisms, the mechanisms by which they engineer ecosystems and their role in mediating coastal bentho-pelagic coupling. Our findings also highlight the potential for deposit-feeders to be used as nature-based solutions to counter coastal eutrophication.
Highlights
Managing coastal ecosystems and preserving socio-ecological functioning require a comprehensive understanding of ecological services provided by resident organisms
The lower reaches of the system is occupied by dense aggregations (176/m2–240/m2) of the sandprawn Callichirus kraussi, but this biotope accounts for approximately 4.9% of the total area of the system (Figs. 1 and 3)
Conductivity generally increased over time and with increasing sandprawn density, but conductivity increases were minor, with mean levels ranging between 26.7 mS/cm ± 0.41 SE and 30.3 mS/cm ± 0.10 SE over time
Summary
Managing coastal ecosystems and preserving socio-ecological functioning require a comprehensive understanding of ecological services provided by resident organisms. The harnessing of ecological functions and services provided by biological systems to overcome environmental degradation, variously referred to as ecological engineering, nature-based solutions, bioremediation and/ or biomanipulation, is increasing in popularity as a sustainable, nature-based tool that can mitigate nutrient enrichment in coastal ecosystems[12,13,14,15] In this regard, suspension-feeding organisms (e.g. clams and mussels) and coastal vegetation have dominated mitigation narratives, leading to significant investments in conservation, restoration and engineering programs that exploit their water-purification capabilities[12,16,17]. These features suggest that in the presence of dense assemblages of axiid crustaceans, three-dimensional burrow superstructures may function as elaborate below-ground coastal filtration systems
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