Salt marshes provide critical ecosystem services and functions including habitat provision and coastal community protection from storms. Chronic disturbances (e.g., anthropogenic inputs, climate change) and episodic disturbances (e.g., storms, oil spills) can affect the species composition and abundances of salt marsh biota, thus influencing ecosystem function and service provision. One such disturbance typical of the northeastern USA is annual nor'easter storms which deposit ice-rafted sediments on the salt marsh surface. In the winter of 2018, however, the extratropical cyclone, winter storm Grayson, deposited sediments equivalent to 15 years of accumulation on portions of the Great Marsh in Ipswich, Massachusetts, USA, potentially causing historic impacts. The recovery of the plant and invertebrate communities were evaluated 3 months, 6 months, and 18 months post ice-rafting from winter storm Grayson. We hypothesized sediment deposits would smother underlying plants, surface-dwelling invertebrates (i.e., epifauna), and surface-feeding infauna, such as polychaetes, although we expected little to no impact to subsurface-feeding infauna, such as oligochaetes. As predicted, plant, epifauna, and surface-feeding infauna were all impacted initially by sediment deposition, with lower abundances in deposits than in references, whereas subsurface-feeding infauna were unaffected. Despite historic volumes of sediment deposited by winter storm Grayson, we saw full recovery of the biotic community within 18 months. Sediment deposits had a maximum thickness of 6.5 cm and were patchily distributed throughout the marsh, and quick revegetation and invertebrate recolonization may ultimately have been from nearby, undisturbed areas. The fast recovery of the biotic community suggests minimal impacts to ecosystem services and functions and indicates an overarching resilience of the salt marsh to natural disturbances such as nor'easters.

The Atlantic marsh fiddler crab, Minuca pugnax (Smith, 1870), is a climate migrant that recently expanded its range northward into the Gulf of Maine. We tracked the M. pugnax population within the Great Marsh, in northeastern Massachusetts, USA, since it was first detected in 2014 using burrow counts. Because burrow counts can overestimate fiddler-crab density, we used camera traps to determine the relationship between burrow densities and fiddler-crab densities in 2019. The burrow count surveys show a six-fold increase in the density of M. pugnax in the Great Marsh from 2014 to 2019. Results indicates that the fiddler-crab population in the expanded range is established and growing. Based on burrow counts, however, the density of M. pugnax in the expanded range (6 burrows m–2) remains much lower than those found in the historical range (up to 300 burrows m–2). Based on the camera traps, we determined that burrow counts overestimated fiddler-crab densities by 47% in 2019. There was, on average, one crab detected for every two burrows observed. This result suggests that estimates of densities of M. pugnax based on burrow counts should be reduced by half. Minuca pugnax is an ecosystem engineer that can influence saltmarsh functioning and the magnitude of that influence is related to its density. Our results imply that the populations of M. pugnax in the expanded range are currently having minor impacts on marshes relative to larger populations in the historical range, but their impact will increase as the populations grow.

It is well known that species across the world are expanding or shifting their ranges because of climate change. Yet, we know little about their impact on the habitats they colonize. In an observational study, we examined the effect of the fiddler crab Minuca pugnax (Smith, 1870) on benthic microalgal biomass in salt marshes in its expanded range (northeastern Massachusetts, USA). We found that plots with M. pugnax had, on average, 74% lower diatom biomass and 77% lower cyanobacteria biomass than plots without M. pugnax. Our results indicate that this climate migrant can impact saltmarsh functioning by limiting benthic microalgal biomass.

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