Marine protected areas act as valuable management tools, often maintaining source populations of fish that support surrounding fished areas through larval dispersal. But will they continue to ensure population persistence given predicted climate change? Shifting temperatures are likely to impact adult reproduction and larval dispersal, and will modify the environmental conditions of the seascape. These factors are all interactive, with results that may be additive, synergistic, or antagonistic. To evaluate these potential effects, Andrello et al. examine connectivity between marine protected areas and simulate how both adults and larvae may react to climate change.
The Mediterranean Sea provides an ideal test system, with approximately 100 marine protected areas as well as numerous over-exploited fishing areas, and it is likely to see a large increase in sea surface temperatures by the end of the century. Andrello et al. use an individual-based mechanistic model that incorporates predicted climate change to simulate changing hydrodynamics, larval dispersal, and adult reproduction. They measured connectivity using four variables: larval dispersal distance, connectance of the overall system, area seeded by larval dispersal, and larval retention from source populations.
The simulation results show that, over time, larval dispersal decreased, dispersal area decreased, and larval retention increased, leading to higher larval concentrations in smaller areas. However, overall connectivity actually increased because increased temperatures made more northern locations available to warm-tolerant populations from the south. Climate change overall affected all measures of connectivity through additive mechanisms, and ultimately impacted the fish populations both inside and outside of protected areas. This study represents the first step in modelling both adult reproduction and larval growth jointly to determine the effects of climate change on marine connectivity.
Andrello, M., D. Mouillot, S. Somot, W. Thuiller, and S. Manel. 2015. Additive effects of climate change on connectivity between marine protected areas and larval supply to fished areas. Diversity and Distributions 21(2): 139-150.