Energetic connectivity of diverse elasmobranch populations – implications for ecological resilience

Abstract

Understanding the factors shaping patterns of ecological resilience is critical for mitigating the loss of global biodiversity. Throughout aquatic environments, highly mobile predators are thought to serve as important vectors of energy between ecosystems thereby promoting stability and resilience. However, the role these predators play in connecting food webs and promoting energy flow remains poorly understood in most contexts. Using carbon and nitrogen isotopes, we quantified the use of several prey resource pools (small oceanic forage, large oceanics, coral reef, and seagrass) by 17 species of elasmobranch fishes ( n = 351 individuals) in The Bahamas to determine their functional diversity and roles as ecosystem links. We observed remarkable functional diversity across species and identified four major groups responsible for connecting discrete regions of the seascape. Elasmobranchs were responsible for promoting energetic connectivity between neritic, oceanic and deep-sea ecosystems. Our findings illustrate how mobile predators promote ecosystem connectivity, underscoring their functional significance and role in supporting ecological resilience. More broadly, strong predator conservation efforts in developing island nations, such as The Bahamas, are likely to yield ecological benefits that enhance the resilience of marine ecosystems to combat imminent threats such as habitat degradation and climate change.

Substantial blue carbon sequestration in the world’s largest seagrass meadow

“…Indeed, we estimate that its annual C org sequestration is equivalent to or even higher than the anthropogenic greenhouse gas emissions in the Bahamas (1.71 Tg C yr −1 at 2018 rates) 44 . Moreover, The Bahamas Banks are generally less than 10 m deep and are bounded by near-vertical declivities into very deep water, which likely facilitate the export of seagrass carbon to the deep ocean 45,46 . Following the estimation by Duarte and Krause-Jensen 45 that 4.9% of the seagrass NPP could be sequestrated in the deep ocean, we estimate that The Bahamas seagrass meadows can contribute roughly 10.4 g C org m −2 yr −1 and a total of 0.70-0.96 Tg C org to C org sequestration in the deep-sea annually.…”

Northeast Atlantic elasmobranch community on the move: Functional reorganization in response to climate change

“…Elasmobranchs contribute to ecosystem functioning with unique combinations of physiological, morphological, reproductive, or behavioral traits (Tilman, 2001) that have no functional equivalent (i.e., functionally distinct species; Coulon et al., 2023; Leitão et al., 2016; Mouillot et al., 2013; Violle et al., 2017). They are known for exerting top‐down regulation (Barley et al., 2017a, 2017b; Ruppert et al., 2013) but they are also linked to other ecosystem functions such as promoting energetic connectivity between neritic, oceanic, and deep‐sea ecosystems (Shipley et al., 2023). Simulated extinction scenarios within various taxonomic groups (e.g., vascular plants, mammals, birds, reptiles, amphibians, and freshwater fish) revealed extensive changes in species trait composition within communities when functionally distinct species were lost (Carmona et al., 2021; Colares et al., 2022; McLean et al., 2019).…”

Management and research efforts are failing dolphins, porpoises, and other toothed whales

“…Charismatic marine vertebrates have been the focus of more intensive research, public interest, and management effort than their other vertebrate and invertebrate counterparts. The heightened interest in species like sharks, marine mammals, and sea turtles is in part due to their charismatic status, but they are also economically valuable for fisheries and tourism 1 , 2 ; they influence the structure, dynamics, and function of ecosystems 3 – 5 ; promote connectivity among ecosystems through nutrient cycling 6 , 7 ; and can be used as sentinel species to monitor ocean health 8 , 9 in a time of unprecedented environmental change. Despite this, charismatic marine vertebrates are not protected from the ongoing biodiversity loss in the world’s oceans, with many taxa, species, and populations increasingly at risk of extinction 10 – 12 .…”