Eutrophication

Florida’s coral reefs are facing a multi-year coral disease outbreak described as stony coral tissue loss disease (SCTLD), affecting at least 24 species of scleractinian corals. Potential anthropogenic and environmental drivers of SCTLD progression and severity are still poorly understood. This project was designed to determine the potential impacts of elevated nutrients on the progression and spread of SCTLD on reefs in Southeast Florida. We attempted to increase nutrient levels near coral colonies using fertilizer amendments to mimic the effects of agricultural and urban runoff. SCTLD lesion progression, coral tissue loss, and disease prevalence were tracked overtime. There were no significant differences in nutrient concentrations between nutrient-amended and control groups or SCTLD progressions or surrounding SCTLD prevalence. However, water temperature was positively correlated to SCTLD activity. These findings provide insight to reef managers seeking to limit and mitigate the prevalence and impacts of SCTLD.

Coastal mangrove forests are at risk of being submerged due to sea level rise (SLR). However, mangroves have persisted with changing sea levels due to a variety of biotic and physical feedback mechanisms that allow them to gain and maintain relative soil surface elevation. Mechanisms of surface elevation change (SEC) include leaf, wood, and root production, decomposition, and sedimentation/erosion, the combination of which result in a net change in the soil’s surface elevation. Therefore, mangrove forest resilience to SLR is dependent upon their ability to migrate inland or to build soil elevation at a rate that tracks with SLR. However, anthropogenic disturbances, such as altered hydrology and eutrophication, can degrade mangrove forest health and compromise their land building processes placing them at greater risk of succumbing to SLR.

Eutrophication is an increase in primary plant nutrients (Nitrogen [N] and Phosphorus [P]) in oceans, estuaries and lakes. The consequences of eutrophication are harmful algal blooms (HABs), resulting in algal toxin production and the depletion of oxygen as the extensive biomass decays. P is often the limiting nutrient and is viewed as a significant environmental problem. Most of the excess P that enters aquatic ecosystems originates from anthropogenic sources such as fertilizers, sewage, animal wastes, compost, crop residues, and wastewater. Over time, one of the main reservoirs of P becomes organic P (Po). We investigated the chemical nature and dynamics of P in cyanobacteria, horse manure, stormwater treatment areas, and rice fields. To better understand the chemical nature of P, the identification of specific P compounds was required, which was achieved through 31P nuclear magnetic resonance (NMR) spectroscopy. We investigated how paramagnetic metals and quadrupolar nuclei cause severe line broadening, peak shifts, and decreased the signal to noise ratio. Results revealed that certain Po forms are readily bioavailable to Microcystis aeruginosa. Additionally, the potential heterotrophic use of the organic portion (e.g., glucose, glycerol) of these P compounds are indicated for the growth and persistence of Microcystis aeruginosa. We showed that the cultivation of rice (Oryza sativa L.) had been found to effectively reduce P from agrarian soil and water through plant uptake and, therefore, minimizing downstream eutrophication. Soil, water, sugarcane, and rice plants at two different stages were analyzed for twelve different elements. Finally, we examined how a “relic” agrarian ditch in Stormwater Treatment Area 1 East (STA-1E) can be used for the retention and sequestration of P and other nutrients. The STAs were established to capture P from agricultural and other sources before reaching the Everglades. Retained P is primarily stored in the wetland soils and sediments, generated through a collection of interrelated physical, chemical, and biological processes.

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.