Coastal eutrophication and freshwater inputs drive acidification in the Indian River Lagoon, Florida

The additive effects of eutrophication and acidification in coastal environments have a wide range of implications for the health of organisms and ecosystems. In the eutrophic waters of the Indian River Lagoon (IRL), FL, USA, decreases in overall shellfish size have been reported, which may be related to coastal acidification. To better understand the relationship between acidification and eutrophication in the IRL, environmental parameters, dissolved nutrients, and aragonite saturation state (Ω_arag) were monitored along the entire IRL in the 2016-2017 wet and dry seasons. Additionally, three sites in the central IRL were sampled approximately weekly from June 2016-June 2017 to observe temporal variability. For the IRL-wide survey, northern sites with higher dissolved nutrient concentrations had lower Ω_arag due to nutrient pollution and harmful algal blooms, while southern sites with lower salinity had lower Ω_arag related to freshwater inputs (i.e., discharges and rainfall). In the time series sampling, there was a positive correlation between Ω_arag with salinity and negative correlations with dissolved nutrient concentrations. This work suggests that freshwater inputs and associated dissolved nutrients and organics have implications for acidification in the IRL, which will be important considerations for restoration efforts in the IRL and beyond.