Relationships between biodiversity and ecosystem functioning proxies strengthen when approaching chemosynthetic deep-sea methane seeps

Abstract

As biodiversity loss accelerates globally, understanding environmental influence over biodiversity–ecosystem functioning (BEF) relationships becomes crucial for ecosystem management. Theory suggests that resource supply affects the shape of BEF relationships, but this awaits detailed investigation in marine ecosystems. Here, we use deep-sea chemosynthetic methane seeps and surrounding sediments as natural laboratories in which to contrast relationships between BEF proxies along with a gradient of trophic resource availability (higher resource methane seep, to lower resource photosynthetically fuelled deep-sea habitats). We determined sediment fauna taxonomic and functional trait biodiversity, and quantified bioturbation potential (BPc), calcification degree, standing stock and density as ecosystem functioning proxies. Relationships were strongly unimodal in chemosynthetic seep habitats, but were undetectable in transitional ‘chemotone’ habitats and photosynthetically dependent deep-sea habitats. In seep habitats, ecosystem functioning proxies peaked below maximum biodiversity, perhaps suggesting that a small number of specialized species are important in shaping this relationship. This suggests that absolute biodiversity is not a good metric of ecosystem ‘value’ at methane seeps, and that these deep-sea environments may require special management to maintain ecosystem functioning under human disturbance. We promote further investigation of BEF relationships in non-traditional resource environments and emphasize that deep-sea conservation should consider ‘functioning hotspots' alongside biodiversity hotspots.

Insights from the management of offshore energy resources: Toward an ecosystem-services based management approach for deep-ocean industries

“…In non-chemosynthetic systems, more diverse communities generally have higher rates of ecosystem function and therefore provide more robust ecosystem services. However, at methane seeps, highest function is not always associated with higher diversity (Ashford et al, 2021a), which emphasizes the need to assess ecosystem services on a site-specific basis. A more BOX 3 Criteria for carrying out impact assessments at different phases of development of oil and gas industrial activities.…”

“…Connectivity plays key roles in structuring and supporting the ecosystem services from the deep sea. For example, the connectivity between chemosynthetic ecosystems and background areas through transition zones and/or chemotones often concentrate a high quantity of ecosystem services (Figure 5, Levin et al, 2016;Ashford et al, 2021a, Ashford et al, 2021b, Gollner et al, 2021. In this instance, a lesson can be taken from the management of fisheries in the U.S., where Essential Fish Habitat (EFH) is managed in addition to the direct management of fish stocks (Moore et al, 2016) to ensure connectivity among habitats utilized by different life stages (Peterson et al, 2020).…”

Food web structure mediate positive and negative effects of diversity on ecosystem functioning in a large floodplain river

“…The current biodiversity crisis has raised concerns about the impacts of the decline in species richness on the provisioning of ecosystem services, making the relationship between diversity and ecosystem functioning a key area of inquiry in ecology (Isbell et al 2011, Tilman et al 2014, Loreau et al 2021). Many factors, including environmental conditions (Baert et al 2018, Li et al 2020, Ashford et al 2021), functional diversity (Duffy et al 2017, Maureaud et al 2019), spatial processes (Thompson et al 2018, Borthagaray et al 2020), eco-evolutionary dynamics (Loeuille 2019, Akesson et al 2021), and trophic interactions (Loreau & Hector 2001, Mora et al 2014, Wu et al 2022), have been identified as determinants of the relationship between species richness and ecosystem functioning (van der Plas 2019). However, in spite that a tight association between diversity and complexity has been largely recognized (Valdovinos et al 2010; McCann 2011; May 1972; Thébault et al 2010), the role of food web structure in the diversity - ecosystem function relationship has been largely overlooked (Nie et al 2023).…”