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The prevalence of crustaceans, such as fiddler crabs, in tropical mudflats can provide functional equivalence to the burrowing worms of temperate regions.

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Seagrass meadows provide a range of important ecosystem functions that can be influenced by anthropogenic pressures. Sediment loading from coastal land use mismanagement can elevate turbidity and reduce seabed light levels, thereby impacting seagrass primary productivity and meadow health. Less understood is the impact of elevated turbidity on the nutrient removal capacity of seagrass, which is a key ecosystem function. Here, we use in situ benthic chambers to show that elevated turbidity is associated with lower nutrient (NH 4 + ) removal within intertidal seagrass meadows. Our results suggest that reductions in sediment loading to improve water clarity may increase the nutrient removal capacity of intertidal seagrass meadows influenced by light limitation. When quantifying important ecosystem functions such as nutrient removal by seagrass it is important to consider this context dependency.

Coastal ocean acidification research is dominated by laboratory-based studies that cannot necessarily predict real-world ecosystem response given its complexity. We enriched coastal sediments with increasing quantities of organic matter in the field to identify the effects of eutrophication-induced acidification on benthic structure and function, and assess whether biogenic calcium carbonate (CaCO 3 ) would alter the response. Along the eutrophication gradient we observed declines in macrofauna biodiversity and impaired benthic net primary productivity and sediment nutrient cycling. CaCO 3 addition did not alter the macrofauna community response, but significantly dampened negative effects on function (e.g. net autotrophy occurred at higher levels of organic matter enrichment in +CaCO 3 treatments than −CaCO 3 (1400 vs 950 g dw m −2 )). By identifying the links between eutrophication, sediment biogeochemistry and benthic ecosystem structure and function in situ , our study represents a crucial step forward in understanding the ecological effects of coastal acidification and the role of biogenic CaCO 3 in moderating responses.