New England salt marsh recovery: opportunistic colonization of an invasive species and its non-consumptive effects.

Tyler C Coverdale,Eric E Axelman,Mark D Bertness,Eric W Young,Caitlin P Brisson,Andrew H Altieri

doi:10.1371/journal.pone.0073823

Tyler C Coverdale, Eric E Axelman + Show 4 more

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https://doi.org/10.1371/journal.pone.0073823

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Abstract

Predator depletion on Cape Cod (USA) has released the herbivorous crab Sesarma reticulatum from predator control leading to the loss of cordgrass from salt marsh creek banks. After more than three decades of die-off, cordgrass is recovering at heavily damaged sites coincident with the invasion of green crabs ( Carcinusmaenas ) into intertidal Sesarma burrows. We hypothesized that Carcinus is dependent on Sesarma burrows for refuge from physical and biotic stress in the salt marsh intertidal and reduces Sesarma functional density and herbivory through consumptive and non-consumptive effects, mediated by both visual and olfactory cues. Our results reveal that in the intertidal zone of New England salt marshes, Carcinus are burrow dependent, Carcinus reduce Sesarma functional density and herbivory in die-off areas and Sesarma exhibit a generic avoidance response to large, predatory crustaceans. These results support recent suggestions that invasive Carcinus are playing a role in the recovery of New England salt marshes and assertions that invasive species can play positive roles outside of their native ranges.

Highlights

Unchecked human population growth has threatened the persistence of natural ecosystems [1] by escalating extinctions [2], ecosystem phase shifts [3], habitat loss [4], and species invasions [5]
Recovering marshes have higher burrow densities and wider burrow complexes than healthy sites [36] and we found that Carcinus were >50X more common at burrowed, die-off sites than healthy sites with few Sesarma burrows (F1,4 = 7.73, P < 0.05)
Our results suggest that Carcinus colonize the intertidal at die-off marshes by using Sesarma burrows as refuges from predation and desiccation

Summary

Introduction

Unchecked human population growth has threatened the persistence of natural ecosystems [1] by escalating extinctions [2], ecosystem phase shifts [3], habitat loss [4], and species invasions [5]. Invasive species have been shown to restore lost ecological functions and promote recovery within heavily degraded ecosystems [8], stimulating debate on the costs and potential benefits of species outside native ranges e.g. [6,9,10,11,12], in light of the extent and severity of human impacts on ecosystems. Invasive predators could have a large impact on the recovery of degraded communities if their impact is exerted through both consumptive and non-consumptive effects [17]. Elucidating recovery mechanisms, including the potential for invasive species to aid in recovery, is essential for informing conservation to improve management success, attain sustainable human ecosystem use, and test ecological theory [19,20]

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