Lapointe, Brian E.

In the eutrophic waters of the Indian River Lagoon (IRL), decreases in overall
shellfish size have been reported, which may be related to coastal acidification. To
understand the relationship between acidification and eutrophication, water samples from
20 sites spanning the IRL were collected and analyzed for dissolved nutrients and omega
values in spring (dry season) and fall (wet season), 2016-2017. Additionally, three sites
were sampled weekly to observe temporal variability of nutrients and omega values. For
the IRL-Wide sampling, sites with higher dissolved nutrient concentrations showed lower
omega values with significant negative relationships. Both sampling programs showed an
overall positive linear relationship between salinity and omega values. This work
suggests that salinity and dissolved nutrients have implications for acidification in the
IRL and must be considered for future water quality, shellfish and coral reef restoration.

Urban and residential land uses in the Indian River Lagoon IRL watershed contribute
sewage and fertilizers to stormwater runoff, resulting in increased nitrogen N and phosphorous P
loadings that can fuel harmful algal blooms. The goal of this project is to quantify dissolved
concentrations of ammonium, nitrate and soluble reactive P in storm water from agricultural,
natural, and urban land uses adjacent to seven of the canals and tributaries within the IRL
watershed. Preliminary results based on water samples taken at the beginning, middle and end of
storm events at 10 sample points suggest initial spikes of soluble reactive P, nitrate and ammonia
in storm water runoff. These results represent the first attempt to characterize nutrient
concentrations of stormwater among various tributaries and land uses on the IRL.

Benthic algal species receive elevated nitrogen (N) and phosphorus (P)
availability as anthropogenic activities increase the loading of nutrients into coastal
waters. Pelagic species could also be responding to this nutrient enrichment. This study
compared the tissue nutrient content and productivity of three benthic and two pelagic
species of Sargassum. We hypothesized that the benthic species would have a higher
tissue nutrient content and productivity than the pelagic species and the pelagic species
would have a higher tissue nutrient content and productivity than historic data. The tissue
nutrient content and net productivity of the benthic and pelagic species were not
significantly different indicating that the pelagic species are receiving high levels of
nutrient availability comparable to that of the benthic species. Pelagic species in the
current study exhibited significantly higher N:P ratios and net productivity than the
historic data, suggesting a shift from N to P limitation and increased productivity.