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SUSCEPTIBILITY OF RECRUITING SEAGRASS (THALASSIA TESTUDINUM) TO POREWATER H2S IN FLORIDA BAY
Title
SUSCEPTIBILITY OF RECRUITING SEAGRASS (THALASSIA TESTUDINUM) TO POREWATER H2S IN FLORIDA BAY.
Creator
MacLeod, Kasey, Koch, Marguerite, Florida Atlantic University, Department of Biological Sciences, Charles E. Schmidt College of Science
Abstract/Description
This study investigated the influence of high concentrations of porewater H2S (~100 μM) on recruitment of the tropical dominant seagrass species, Thalassia testudinum, following mortality events or "die-offs" in Florida Bay. Major seagrass die-off events (>50 km2) are occurring globally in coastal regions with mortality frequently linked to hypoxia and sediment-derived hydrogen sulfide (H2S) exposure, a well-known phytotoxin. In tropical carbonate environments, such as Florida Bay, low iron...
Show moreThis study investigated the influence of high concentrations of porewater H2S (~100 μM) on recruitment of the tropical dominant seagrass species, Thalassia testudinum, following mortality events or "die-offs" in Florida Bay. Major seagrass die-off events (>50 km2) are occurring globally in coastal regions with mortality frequently linked to hypoxia and sediment-derived hydrogen sulfide (H2S) exposure, a well-known phytotoxin. In tropical carbonate environments, such as Florida Bay, low iron in sediments promote H2S accumulation and subsequent intrusion into seagrass meristematic tissue through roots, and root-shoot junctions. While H2S intrusion into meristematic tissue is a leading hypothesis for large-scale seagrass mortality events, it is less clear if H2S contributes to a decline in seagrass recruitment following large-scale seagrass die-off events. Herein, I examined tissue stable sulfur isotope signatures (d34S), belowground tissue biomass partitioning, and internal O2/H2S dynamics of newly recovering shoots over seasons at a western Florida Bay site with recurrent die-off events. Tissue results showed less H2S accumulation in tissue samples of shoots recruiting into bare sediment patches compared to tissue samples from adjacent T. testudinum and H. wrightii seagrass meadows. Additionally, internal gas dynamics of recruits showed high pO2 during the day, and no detection of meristematic H2S intrusion, despite meristem hypoxia for several hours during the night. Recruiting shoots consistently have low root biomass, likely contributing to a lack of meristem H2S intrusion, as young, minimally developed, or lack of roots in recruiting shoots limit H2S intrusion. These results lead me to suggest that high H2S levels in porewater of western Florida Bay does not limit T. testudinum recruitment into open bare patches following major die-off events, supported by the recovery, albeit slow, of this species based long-term monitoring of seagrass in the Bay.
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Date Issued
2022
PURL
http://purl.flvc.org/fau/fd/FA00014030
Subject Headings
Thalassia testudinum, Seagrasses, Hydrogen sulfide, Pore water
Format
Document (PDF)
Estuaries in distress
Title
Estuaries in distress.
Creator
Barile, Peter J., Lapointe, Brian E.
Date Issued
1999
PURL
http://purl.flvc.org/fau/fd/FA00007317
Subject Headings
Estuaries, Hydrogen sulfide, Algae, Indian River (Fla. : Lagoon)
Format
Document (PDF)
INTERNAL OXYGEN DYNAMICS AND RHIZOSPHERE OXIDATION IN TROPICAL SEAGRASS, THALASSIA TESTUDINUM
Title
INTERNAL OXYGEN DYNAMICS AND RHIZOSPHERE OXIDATION IN TROPICAL SEAGRASS, THALASSIA TESTUDINUM.
Creator
Winn, Nathaniel, Koch-Rose, Marguerite, Florida Atlantic University, Department of Environmental Sciences, Charles E. Schmidt College of Science
Abstract/Description
Large-scale seagrass mortality events have been linked to internal hypoxia and exposure to phytotoxins in the sediment, such as hydrogen sulfide (H2S). Although seagrasses can transport oxygen (O2) to belowground tissues (rhizomes and roots) and into surrounding sediment to prevent H2S intrusion, reoccurring seagrass mortality events from H2S exposure continue. In the present study, I examined the potential of tropical seagrass Thalassia testudinum to transport O2 effectively to belowground...
Show moreLarge-scale seagrass mortality events have been linked to internal hypoxia and exposure to phytotoxins in the sediment, such as hydrogen sulfide (H2S). Although seagrasses can transport oxygen (O2) to belowground tissues (rhizomes and roots) and into surrounding sediment to prevent H2S intrusion, reoccurring seagrass mortality events from H2S exposure continue. In the present study, I examined the potential of tropical seagrass Thalassia testudinum to transport O2 effectively to belowground tissues and diffuse O2 into Florida Bay sediment around the root rhizosphere or sediment-root interface to constrain H2S diffusion into the roots. My approach was to (1) examine the spatial distribution of O2 in the rhizosphere during the light and dark with 2-D planar optode sensors, (2) examine patterns of root O2 loss (ROL) with O2 dye tracing experiments, and (3) measure O2 and H2S dynamics in internal tissues and rhizospheres. My results indicate that T. testudinum effectively sustains oxidation in belowground tissues to constrain H2S, but minimal evidence of ROL into the rhizosphere.
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Date Issued
2023
PURL
http://purl.flvc.org/fau/fd/FA00014365
Subject Headings
Turtle grass Seagrasses, Thalassia testudinum, Hydrogen sulfide--Environmental aspects, Rhizosphere
Format
Document (PDF)