DETECTING TRENDS IN ABUNDANCE AND DISTRIBUTION OF SEAGRASSES IN LAKE WORTH LAGOON, PALM BEACH COUNTY, FLORIDA

Abstract

Over the past 15 years, seagrass community stability has varied in estuaries throughout Florida. This study sought to model potential patterns of physiochemical parameters and community composition that may correlate with the fluctuation of seagrass populations in Lake Worth Lagoon (LWL), Palm Beach County, FL over time (2007–2019). Seven transects and 4 polygon areas throughout the LWL were established and stratified along a north—south gradient. Sites were sampled annually (May–August) for water quality, seagrass and macroalgal abundance, and community composition. Models developed to explain macrophyte abundance and composition were assessed using Akaike Information Criterion. Interaction between year and site best explained seagrass abundance and community composition in transect and polygon sites. Transect data revealed that seagrass and macroalgae declined after 2012 and continued until barely detected after 2016. This die off was not consistent for all transects and there was site variability in annual dissolved oxygen, nitrate, phosphate, and salinity levels. Polygon sites exhibited a shift in community composition after 2013, initially dominated by seagrass species Syringodium filiforme and Halodule wrightii before transitioning in 2012–2013 to Halophila decipiens and Caulerpa spp. Central lagoon sites transitioned to communities devoid of nearly all vegetative species. The loss of seagrass and the change in community composition could be explained by a transient dry period in 2012 and a subsequent inflow of freshwater. These events (sudden drought followed by an increase in freshwater) likely compounded the stress on the system between 2011–2014, leading to a drastic change in seagrass community.