Faculty researchers and graduate students at the Florida Institute of Technology (Florida Tech) in Melbourne have been contracted by the State of Florida, in support of a local project appropriation secured by Brevard County legislators, to study the potential effects of enhanced seawater exchange (inflow) between the Indian River Lagoon (IRL) and coastal ocean.

This multi-year effort includes proposed installation of a temporary demonstration system by an appropriate agency to help policymakers, agencies, and stakeholders determine if enhanced seawater exchange should be considered to help improve the IRL ecosystem.

Decades of increasing nutrient pollution have seriously imperiled the health and productivity of the IRL, with widespread habitat loss, mass wildlife mortalities, and disruption of historic ecosystem processes. Florida policymakers and agencies need more information to help determine the most effective strategies to stabilize and restore the lagoon system. Multiple agencies are involved in efforts to reduce excess nutrients and improve lagoon water quality through a variety of projects, policies, and legislative initiatives.

By improving understanding and management of the IRL system, RLI project results will help to address several actions in the IRL National Estuary Program Comprehensive Conservation and Management Plan, including specifically addressing action “Connected Waters-5” which calls for a demonstration project to assess the benefits and risks of enhanced ocean exchange with the lagoon.

No new navigable inlet is proposed and the RLI efforts do not advocate for a specific outcome.

Yes. The Destin Harbor pump site in Destin, Florida, has been operating since 1992 to increase seawater exchange for improved water quality and prevention of fish kills resulting from low dissolved oxygen levels. Similar engineering initiatives to enhance seawater exchange have improved water quality in New York, California, and internationally. While the IRL ecosystem is different in many ways from these other systems, the success of existing projects highlights the potential benefits of using enhanced inflow to address declining water quality in the IRL.

The RLI project builds-on more than 25 years of Florida Tech lagoon circulation and water quality research. These efforts have helped improve understanding and management of the lagoon, including creek and inlet hydrodynamics (Liu, Zarillo & Surak 1997; Zarillo and Yuk 1997; Zarillo 2006), lagoon circulation (Weaver et al. 2016; Rasario-Llantin and Zarillo 2021), muck dredging (2016-2020 annual reports), and proposed infrastructure improvements (Saberi and Weaver 2016, Zarillo 2018). Findings from the RLI project will inform future federal, state and local projects intended to restore and enhance natural IRL water circulation to improve both habitat and water quality.

Given the complexity of the lagoon ecosystem, the Florida Tech team is updating models and collecting geochemical and biological data to predict how the lagoon system may respond to enhanced seawater exchange. Research areas include, but are not limited to, lagoon circulation and residence time, salinity and temperature variation, water and sediment biogeochemistry, submerged aquatic vegetation cover (e.g., seagrasses), plankton and fish community response, and inflow system engineering. 

The RLI demonstration project is multi-phased. Agency and regulatory reviews and stakeholder input have guided project development and will continue to guide priorities and design of the proposed demonstration system. The initial phases summarized existing data and generated new environmental monitoring, modeling, and research data to improve understanding of the IRL and how the ecosystem might respond to enhanced seawater exchange. Phase 3 of the RLI project was completed in August 2023 and included additional baseline research and modeling efforts, pilot system final design, and approval of United States Army Corps of Engineers and Florida Department of Environmental Protection permits. Phase 1 through 3 results, when combined with findings from the temporary inflow pilot system by an appropriate agency, will allow for an informed determination of the feasibility and impacts of a potential permanent ocean inflow system.

Upon review of the project’s Phase I results, Port Canaveral was selected as the preferred location for the temporary demonstration system due in part to the relative lower cost and ease of access for a temporary demonstration system, as well as the existing exchange of seawater from port access at the locks. The proposed demonstration system was designed with a low pumping rate into a confined cove south of Port Canaveral Lock. If a permanent system is supported by policymakers in the future, an installation site or sites will need to be selected.

No. The inflow rates under consideration for the temporary inflow demonstration project would be controlled and limited in volume, with no perceptible impact on lagoon water level. Currently, the lagoon water level fluctuates with tides, storm activity, and rainfall. Water levels also rise and fall seasonally in response to changes in Gulfstream circulation, which can change lagoon water level by as much as two feet from season-to-season.

Preliminary project models indicate enhanced inflow will increase oxygen availability and stabilize lagoon water temperature and salinity. Inflow is also predicted to reduce overall nutrient loads responsible for harmful algal bloom outbreaks by promoting natural processes that remove excess nutrients, with no predicted increase in nutrient loads in other areas of the lagoon or increase in nutrient export to the coastal ocean through Sebastian Inlet.

Inflow rates under consideration for the temporary demonstration project were selected in part to confine effects to the immediate vicinity of the demonstration site. Adverse impacts from the demonstration project to lagoon fish and other estuarine-dependent species are not expected.  

While there is currently not enough information to determine ecological effects from a large-scale inflow system, findings from the first three phases of the RLI project highlight the impact of poor water quality on lagoon fish stocks and indicate enhanced inflow could potentially mitigate negative impacts from severe heat and cold events. Future efforts would help determine whether controlled seawater exchange can help restore impacted fish populations, including investigating population response to projected changes to water temperature and salinity.

The temporary demonstration system and any future infrastructure would be designed with safety features to prevent manatees and other wildlife from being trapped or impeded, including automatic and manual emergency shutoff features.

There is currently not enough information to make an effects determination. Findings from the first three phases of the RLI project highlight the impaired state of the lagoon and the influence of oxygen levels on nutrient biodegradation. Initial results are consistent with published studies and suggest that enhanced seawater exchange can decrease the concentration of nutrients that support the onset and proliferation of algal blooms.

The main benefits of decreased nutrient concentrations would likely result from changes to biogeochemical nutrient cycling due to improved dissolved oxygen levels, with limited additional benefits from direct dilution by seawater. Another significant predicted benefit of ocean inflow would be buffering against extreme temperature and salinities that have been attributed to mass mortality events and initiation of the regime shift from a seagrass to algal dominated system.

In the next project phase, construction of a temporary demonstration inflow system spearheaded by an appropriate agency will help researchers extrapolate effects of a potential full-scale inflow system.

Enhanced seawater exchange would not, on its own, solve lagoon water quality issues. Rather, enhanced inflow could potentially augment ongoing and proposed efforts to reduce lagoon nutrient loads and improve ecosystem restoration efforts.

After completion of the temporary demonstration project, data and assessments will be provided to policy makers, permitting agencies, and other stakeholders. If warranted, policy makers could begin steps toward installation of a large-scale seawater exchange system as a complimentary approach to restoring IRL water quality. This process would involve public discussions, site engineering, site selection, permitting, and natural resource monitoring.

Permitting and consulting agencies and stakeholder organizations include the St. Johns River Water Management District, Florida Fish and Wildlife Conservation Commission, U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, Florida Department of Environmental Protection, IRL National Estuary Program, Port Canaveral, Brevard County, Indian River County, and several municipalities.

Research support was provided by Applied Ecology, Brevard Zoo, Florida International University, Florida Fish and Wildlife Research Institute, Hubbs-SeaWorld Research Institute, University of Florida, and University of West Florida.

Pre-application permitting consultations with Florida Fish and Wildlife Conservation Commission, U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, and Florida Department of Environmental Protection were initiated in project Phases 1 and 2. The outcome of these meetings established protocols to address permitting-related issues and to facilitate expedited review of the temporary demonstration project permit. Phase 3 of the project completed review and authorization of U.S. Army Corps of Engineers’ (USACE) Section 404 and Section 408 permits, and the State of Florida Environmental Resource Permit. Approved permits are transferable to allow any agency to install, operate, and maintain the temporary pumping system for additional research efforts.

The RLI executive summaries and full reports are in the Reports Section of the Florida Tech Indian River Lagoon Research Institute site: https://www.fit.edu/indian-river-lagoon/.