Multiple stressors facilitate the spread of a non‐indigenous bivalve in the Mediterranean Sea

Gianluca Sarà,Erika M.D Porporato,Maria Cristina Mangano,Nova Mieszkowska

doi:10.1111/jbi.13184

Abstract

AbstractAimThe introduction of non‐indigenous species (NIS) via man‐made corridors connecting previously disparate oceanic regions is increasing globally. However, the environmental and anthropogenic factors facilitating invasion dynamics and their interactions are still largely unknown. This study compiles and inputs available data for the NIS bivalve Brachidontes pharaonis across the invaded biogeographic range in the Mediterranean basin into a species distribution model to predict future spread under a range of marine scenarios.LocationMediterranean Sea.MethodsA systematic review produced the largest presence database ever assembled to inform the selection of biological, chemical and physical factors linked to the spread of B. pharaonis through the Suez Canal. We carried out a sensitivity analysis to simulate current and future trophic and salinity scenarios. A species distribution model was run to determine key drivers of invasion, quantify interactive impacts arising from a range of trophic states, salinity conditions and climatic scenarios and forecast future trajectories for the spread of NIS into new regions under multiple‐parameter scenarios (based on the main factors identified from the systematic review).ResultsImpacts on invasion trajectory arising from climate change and interactions with increasing salinity from the new opening of the canal were the primary drivers of expansion across the basin, the effects of which were further enhanced by eutrophication. Predictions of the current distribution were most accurate when multiple stressors were used to drive the model. A habitat suitability index developed at a subcontinental scale from model outputs identified novel favourable conditions for future colonization at specific locations under 2030 and 2050 climatic scenarios.Main conclusionsFuture expansion of B. pharaonis will be enhanced by climate‐facilitated increased sea temperature, interacting with increasing pressures from salinity and eutrophication. The spatially explicit risk output maps of invasions represent a powerful visual product for use in communication of the spread of NIS and decision‐support tools for scientists and policymakers. The suggested approach, the observed distribution pattern and driving processes can be applied to other NIS species and regions by providing novel forecasts of species occurrences under future multiple stressor scenarios and the location of suitable recipient habitats with respect to anthropogenic and environmental parameters.

Highlights

Climate change is driving poleward range shifts across a wide range of marine benthic taxa (Helmuth, Mieszkowska, Moore, & Hawkins, 2006; Mieszkowska, Sugden, Firth, & Hawkins, 2014; Mieszkowska et al, 2006; Pecl et al, 2017) and is thought to be exacerbating the invasion success of non-indigenous species (NIS) (Pederson et al, 2011)
No evidence exists within the current literature on the effect of trophic status on the presence of B. pharaonis, as most filter feeder diets comprise of fresh particulate organic matter and detritus, will likely be affected by trophic condition shifts as expressed by changes in suspended chlorophyll-a
Chlorophyll-a, salinity and surface temperature were the predictors accounting for the highest percentage of the modelled current distribution (Figure A1 and Table A1 in Appendix S2), which was in accordance with values from the literature (AUC = 0.816 Æ 0.052; Figure 2 current scenario, 2010)

Summary

Introduction

Climate change is driving poleward range shifts across a wide range of marine benthic taxa (Helmuth, Mieszkowska, Moore, & Hawkins, 2006; Mieszkowska, Sugden, Firth, & Hawkins, 2014; Mieszkowska et al, 2006; Pecl et al, 2017) and is thought to be exacerbating the invasion success of non-indigenous species (NIS) (Pederson et al, 2011). Advances in our ability to track biogeographic range shifts and invasions have increased awareness of the complexity of environmental and anthropogenic processes involved in biological invasions in a changing world. Unilateral response to warming of the global oceans, scientists seek new, integrated approaches to predict future biogeographic shifts of NIS (Burrows, Schoeman, & Richardson, 2014). The development of predictive models that can be run for a range of multiple anthropogenic factor (hereafter termed stressors) scenarios will increase the accuracy of quantitative forecasts for ecological and economic costs of invasion, and provide useful guidance for planning management or control strategies that form part of the mitigation and adaptation management processes (Chapman, Makra, & Albertini, 2016)

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Conclusion