COS 110-1 - The Indian River Lagoon Observatory Network of Environmental Sensors (IRLON): Addressing the Emerging Environmental Issue of Coastal Acidification in Florida’s Estuaries
Ocean acidification is widely recognized as a threat to oceans, but only recently has coastal acidification (CA) been recognized as a serious threat to estuaries. The Indian River Lagoon Observatory Network of Environmental Sensors (IRLON) is an estuarine observation with 10 stations in the south central Indian River Lagoon (IRL) and St. Lucie Estuary (SLE). These sites are ecologically important because of the dynamic interface between oceanic water from the inlets and freshwater inputs from rivers, canals, and Lake Okeechobee. Such high-frequency, continuous observatory data enable better quantification and modeling of relationships between environmental factors and biological processes in estuaries with tremendous climate-related interannual variability. Each IRLON station consists of a custom suite of biogeochemical instrumentation coupled with meteorological sensors to provide real-time, high-accuracy and high-resolution water quality/weather data through a dedicated interactive website. Underwater sensors measure hourly: temperature, conductivity (salinity), pressure (depth), turbidity, chromophoric dissolved organic matter (CDOM), dissolved oxygen, pH, nitrate, phosphate, and chlorophyll. In 2021, new monitoring of pCO2 addressed the emerging threat of CA to the IRL and are being with IRLON’s SeaFET pH capabilities to calculate the remaining carbonate system parameters, including aragonite saturation, an important component in acidification of estuaries and the coastal ocean.
Results/Conclusions
Three months of initial pCO2 data (July – September 2021) demonstrated large differences among stations. pCO2 levels at IRL stations near three inlets are lower than the much more elevated levels upstream in the IRL and SLE. Along a well-defined salinity gradient (with elevated organic matter, nitrogen, and phosphorus related to lower salinity), the lowest pCO2 concentration (568 ppm) was at the IRL-SLE station near the St. Lucie Inlet. Values increased rapidly at the three stations immediately upstream, ranging from 2,880 to 4,143 ppm. The freshest station, SLE-SF2, had a mean of 7,578 ppm. In the dry season, physical control of pCO2 is primarily driven by temperature. Salinity is a secondary physical parameter that exerts physical control on pCO2. Biological control on pCO2 is also evident, as demonstrated by its relationships to both dissolved oxygen concentration and pH. Because estuaries, such as the IRL and the SLE, networks of environmental sensors such as IRLON that measure key CA parameters (pH, pCO2) are necessary to detect real trends in CA and to guide management efforts on how to identify impacts of CA (e.g., on shell fish resources) and possible mitigation strategies (e.g., seagrass restoration).
