Tiger sharks support the characterization of the world’s largest seagrass ecosystem

Seagrass conservation is critical for mitigating climate change due to the large stocks of carbon they sequester in the seafloor. However, effective conservation and its potential to provide nature-based solutions to climate change is hindered by major uncertainties regarding seagrass extent and distribution. Here, we describe the characterization of the world’s largest seagrass ecosystem, located in The Bahamas. We integrate existing spatial estimates with an updated empirical remote sensing product and perform extensive ground-truthing of seafloor with 2,542 diver surveys across remote sensing tiles. We also leverage seafloor assessments and movement data obtained from instrument-equipped tiger sharks, which have strong fidelity to seagrass ecosystems, to augment and further validate predictions. We report a consensus area of at least 66,000 km2 and up to 92,000 km2 of seagrass habitat across The Bahamas Banks. Sediment core analysis of stored organic carbon further confirmed the global relevance of the blue carbon stock in this ecosystem. Data from tiger sharks proved important in supporting mapping and ground-truthing remote sensing estimates. This work provides evidence of major knowledge gaps in the ocean ecosystem, the benefits in partnering with marine animals to address these gaps, and underscores support for rapid protection of oceanic carbon sinks.


Field-specific reporting
Please select the one below that is the best fit for your research. If you are not sure, read the appropriate sections before making your selection. Did the study involve field work?
Yes No ground-truth seafloor photogrammetry information from this study are available DRYAD51 data repository. The Allen Coral Atlas mapping data were downloaded from: https://allencoralatlas.org/atlas/#5.39/24.3807/-76.0918. Source data are provided with this paper. The processed seagrass carbon stock data and tiger shark depth data are provided in the Source Data file.
n/a n/a n/a n/a This study describes the spatial extent of seagrass habitat in The Bahamas, using an innovative integration of data streams. These data streams included remote sensing, seafloor photogrammetry, tiger shark movements, tiger shark camera deployments, and seagrass sediment cores. No experiments were performed in this study.
Free-ranging, wild tiger sharks (Galeocerdo cuvier) were safely tagged and released from 2011 -2019, for all shark-based data portions of the study. The nature of finding and sampling these large predators makes data collection a largely opportunistic endeavor. We combined all available data from this long-term monitoring for our study. The tiger sharks evaluated in this study were believed to be representative of the population of tiger sharks in The Bahamas, given broad geographic distribution of individuals which provided data across the two primary carbonate banks in The Bahamas.
Sample sizes were chosen based on rough comparisons to relevant, published studies for each data stream (tracking and camera tag data on large sharks such as tiger sharks, ground-truthing used in remote sensing studies, seagrass sediment cores).
Data were collected by authors listed in the submitted co-author list, according to the Author Contributions. Field data were collected as such: Tiger shark satellite tag (AJG, ONS, NH, BDS, SK, NLP, LH), tiger shark camera tag data (AJG, BDS, SK, ABC, NLP, LH), benthic photos (AJG, BDS, AP, ASK, AM), remote sensing and mapping (JWB, MSH), and seagrass sediment core collection and analysis (AJG, WH, SDH, CF, CMD) . All data were collected either from boats during scheduled research trips in The Bahamas.
Data collection for the study began in January 2011 and concluded on December 16, 2020. The majority of shark data were collected from 2018-2020. All diver data were collected from 2018-2020, and remote sensing estimates were performed from May 2020 -May 2021. Seagrass sediment core samples were collected in 2011 and 2022. All empirical data were collected within the Exclusive Economic Zone of The Commonwealth of The Bahamas.
No data were excluded.
No attempts were made to reproduce the findings here; however, all spatial estimates were ground-truthed using real images from the Bahama Banks. Furthermore, remote sensing machine learning algorithms were validated using real field data, producing accuracy estimates as seen in the Extended Data and Supplementary Information. All aspects of the field work were performed independently (tiger shark tagging, remote sensing, seafloor photogrammetry, carbon stock analyses).
All study organisms used were free-ranging, wild, and thus randomly sampled. All individuals from which data were collected were ultimately released alive. No experimentation was performend which may have required random sampling.
Blinding was not relevant to this study as this was not involving human subjects nor species that were tested under any controlled experimental conditions.