Increases in salinity variability harm both oysters and their predators, offsetting predicted effects on population...

Area of Science:

• Ecology
• Climate Change Biology
• Population Dynamics

Background:

• Eastern oysters (Crassostrea virginica) are ecologically and economically vital estuarine species facing threats from salinity fluctuations.
• The southern oyster drill (Stramonita haemostoma), a key predator, exhibits salinity-dependent survival and feeding, thriving in high salinity and being impaired by low salinity.
• Increased salinity variability due to climate change may alter predator-prey dynamics, potentially intensifying predation on oysters.

Purpose of the Study:

• To project the effects of increased salinity variability on Eastern oyster populations and their predator, the southern oyster drill.
• To investigate the role of environmentally dependent species interactions in forecasting climate-driven population changes.
• To assess the impact of altered salinity regimes on predator-prey dynamics in estuarine ecosystems.

Main Methods:

• Developed a two-species integral projection model incorporating salinity-dependent demography for oysters and drills.
• Included size-structured and salinity-dependent predator functional responses based on laboratory experiments.
• Forced the model with simulated salinity time series reflecting increased variability predicted by global climate models.

Main Results:

• Contrary to expectations, increased salinity variability showed minimal impact on oyster abundance or quasi-extinction probability.
• Negative effects of salinity variability on oysters were largely offset by the inhibition of drill predation during low-salinity anomalies.
• Sensitivity analysis indicated that increasing drill mortality could counteract negative impacts of salinity variability.

Conclusions:

• Forecasting climate change impacts on predator-prey systems requires accounting for complex, environmentally dependent interactions.
• Salinity variability's effects on oysters are moderated by predator responses to low-salinity conditions.
• Management strategies, such as increasing predator mortality, could mitigate negative climate change effects on oyster populations.