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

Abstract

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.

Soil Carbon, Nitrogen, and Phosphorus Stoichiometry and Fractions in Blue Carbon Ecosystems: Implications for Carbon Accumulation in Allochthonous-Dominated Habitats

“…The BCE area data are dominantly derived from remote sensing combined with field survey. Accurate mapping of saltmarshes is still challenging due to the spatial resolution of satellite products is not enough to identify their spatial, temporal, and spectral variations. , The wide range of per unit OC stocks and SAR also enhance the uncertainty and variation in estimation of carbon accumulation potentials. For instance, the soil OC content and SAR at one seagrass site (WH2) are ∼10 and ∼3 times higher than those in other sites (Figures S6 and S7).…”

Correspondence among multiple methods provides confidence when measuring marine protected area effects for species and assemblages

“…Our analysis uncovered multiple examples of this phenomenon with a variety of both targeted and non‐targeted species, highlighting the importance of considering multiple data sources and species‐specific biology when designing an MPA monitoring plan. For example, in ecosystems where larger‐bodied, highly mobile carnivorous fishes like sharks are important, such as in the seagrass meadows of the Caribbean (Gallagher et al., 2022), managers stand to benefit most from some type of BRUV monitoring, as larger‐bodied predators are more frequently encountered on this technique than UVC. In contrast, in tropical MPA networks such as the Great Barrier Reef, where parrotfishes and other herbivores are crucial to mediating coral‐macroalgae competition (Cheal et al., 2010) managers would likely benefit the most from an extensive UVC monitoring regime, as herbivores are less likely to be encountered on baited surveys.…”

Energetic connectivity of diverse elasmobranch populations – implications for ecological resilience

“…The second functional group, neritic-oceanic connectors (NOCs) comprised species that predominantly relied upon coral reef and oceanic-derived energy (figure 5), which is supported by existing knowledge of vertical movement behaviors (reviewed by [68]). Caribbean reef sharks relied upon energy derived from seagrass, coral reef and oceanic forage species, reflecting their movements across ecotones [21][22][23]29]. Their reliance on oceanic forage species may also, in part, explain the functionality of commonly observed deep-diving behaviours [62, 68,69].…”

“…Among target areas for research on trophic coupling, marine seascapes within subtropical and tropical latitudes offer a valuable opportunity to understand patterns of predator-mediated ecosystem connectivity, due to the diversity of species and distinct ecosystems that exist across very small spatial scales [20]. In The Bahamas, acoustic telemetry and biologging revealed that tiger sharks connect coral reef, carbonate banks and seagrass meadows throughout their home range [21], whereby the intermediary seagrass habitats appear to serve as strategic navigation routes and connective pathways between ecosystems [22,23]. At Palmyra Atoll, blacktip reef sharks ( Carcharhinus melanopterus ), grey reef sharks ( C. amblyrhynchos ) and red snapper ( Lutjanus fulvus ) were shown to derive energy from lagoon, forereef and oceanic environments, with grey reef sharks connecting forereef and oceanic components and potentially linking the epipelagic and deep-water environment [9].…”