5th UF Water Institute Symposium Abstract

Submitter's Name Savanna Barry
Session Name Poster Session - Coastal Waters
Poster Number 9
Author(s) Savanna Barry,  University of Florida, Fisheries and Aquatic Sciences (Presenting Author)
  Charles Jacoby,  University of Florida, Soil and Water Science
  Thomas Frazer, University of Florida, School of Natural Resources and Environment
  Seagrass resilience to shading driven by biomass allocation ratio
  Seagrasses are unique marine plants with fully developed leaves, roots and rhizomes and a high degree of phenotypic plasticity in allocating tissue to these structures. Along Florida’s Gulf coast, concentrations of chlorophyll-a in surface waters and the widths and lengths of leaves of the dominant seagrass, Thalassia testudinum, increased along a gradient of increasing phosphorus concentrations in the water column. Aboveground to belowground biomass ratios (AG:BG) for T. testudinum indicated that seagrasses allocated relatively more biomass to aboveground structure as phosphorus concentrations in the water column increased. Based on these results, we designed an 8-week shading-recovery experiment in T. testudinum meadows with three different AG:BG ratios (high, intermediate, and low) to determine if relative allocation of biomass influenced resilience to short-term shading. Seagrasses in all treatment plots persisted through the 5 weeks of shading, but responded negatively to shading by decreasing leaf growth rates or altering leaf morphology. A 3-week recovery period showed that T. testudinum with intermediate AG:BG ratios were more resilient to shading than T. testudinum with either high or low ratios, and seagrasses with high AG:BG ratios were the least resilient. Overall, these results suggested that long-term water quality conditions may exert a strong influence on allocation of biomass by T. testudinum, which potentially may affect their ability to recover from short–term disturbances. In turn, AG:BG ratios are important metrics to monitor in seagrass meadows because they indicate areas of high and low resilience to short-term disturbances.