Quantifying the interactions among ocean acidification, temperature, and fishing for marine invertebrates

Background/Question/Methods

Rising atmospheric concentrations of carbon dioxide will alter both ocean temperature and pH. Ocean acidification (OA) can decrease survival, slow growth, and extend development time for invertebrate larvae, particularly those that calcify, while higher temperatures can speed development. Increased mortality, slowed growth, and changed development affect dispersal, which can alter the persistence and spatial distribution of marine invertebrate populations. For exploited populations with economic as well as ecological value, changes in population structure will also alter the maximum attainable fishery yields, which could change spatial patterns of fishing. Understanding the interactions among OA, temperature, and fishing in a spatial context is necessary for determining the overall population-level effects and the potential fishery impacts and response. Using a spatially-explicit population model, this project develops a framework to explore and quantify the relative population-level consequences of OA and temperature effects and their interaction with fishing for marine invertebrates. 

Results/Conclusions

OA effects on larval survival, growth, and development cause equilibrium population sizes and the number of larvae available to settle to drop. Larval survival effects cause the largest population decreases, followed by growth and developmental effects. Temperature effects on development have little effect on population sizes. Both OA and temperature developmental effects change the composition of arriving larvae, which can affect population connectivity: OA increases the percentage of larvae arriving at a location other than their origin while temperature effects decrease the percentage of larvae arriving from elsewhere.

By increasing development time and decreasing larval survival, OA reduces the number of larvae reaching habitat to settle, shifting populations from persistent to non-persistent due to a shortage of arriving larvae. Temperature effects on development can have the reverse effect and make populations more likely to be persistent. Higher levels of fishing mortality also increase the likelihood of a population becoming larval-limited and collapsing. The combination of fishing with OA and temperature could push some populations into a non-persistent state. Species already close to being limited by larval supply and those that experience OA effects on larval survival, particularly those with long development times, look to be the most vulnerable.