How functionally diverse are fish in the deep? A comparison of fish communities in deep and shallow‐water systems

Abstract

Aim Functional diversity metrics inform how species’ traits relate to ecosystem functions, useful for quantifying how exploitation and disturbance impact ecosystems. We compare the functional diversity of entire fish communities in a shallow‐water region with a deep‐sea region for further insight into the differences between these ecosystem types. Location The regions compared in this study were selected to represent a shallow‐water coastal region, Tasman and Golden Bays (TBGB), and a deep‐sea region, Chatham Rise (CR), in New Zealand. Methods Functional diversity was assessed using four metrics: functional richness, evenness, divergence and dispersion. We compared these metrics across four key functions: habitat use, feeding, locomotion and life history. Results Our results showed that overall, the shallow‐water and deep‐sea ecosystems had equal diversity. When focusing on the four ecological functions, the two ecosystems exhibited equal diversity metrics across most analyses. Of the significantly different results, the deep‐sea had higher functional richness for habitat use and locomotion traits, lower functional dispersion for feeding and lower functional evenness for life history. Main conclusions Differences across the functions highlight higher diversity of habitat utilization by deep‐sea fish, while lower diversity in feeding suggests deep‐sea fish tend towards generalist diets, likely driven by low food availability. Deep‐sea fish displayed an increased range of locomotive traits in our analyses, but this conflicts with existing evidence and warrants further study. Life‐history results suggest deep‐sea fish exhibit higher clustering of traits, indicating potential under‐utilization of life‐history strategies in the deep‐sea. Our results demonstrate that although deep‐sea fish communities have similar levels of diversity to shallow‐water communities, the traits that structure this diversity differ, and therefore, the systems may respond to exploitation differently.

Functional diversity in reef fish assemblages in the Parque Nacional Sistema Arrecifal Veracruzano, Mexico: Temporal and spatial changes

“…Without a focus on which functional process dominates, it is difficult to delineate which trait or set of traits (e.g., locomotion, feeding, habitat use) would most likely be related to depth and food availability. Depth was shown to be important in our results, and feeding habits are a significant variable for community structure differentiation (Ferreira et al, 2001;Deus and Petrere-Junior, 2003;Carrington et al, 2021). It has been widely suggested that the primary mechanisms regulating reef fish community structure may vary as a function of reef type, reef context, and geographic region (e.g., Beukers and Jones, 1998;Friedlander et al, 2003;Darling et al, 2017;Wetmore et al, 2020).…”

“…The depth level is another variable that seems to have an important effect, either direct and/or as a causation of other conditions that were identified to be important in the community functional structure (coral coverage, less impacted sites, reduce discharge of continental waters). Other studies focusing on deep-sea functional communities have reached a similar conclusion, both directly (Mindel et al, 2016) and indirectly (Carrington et al, 2021;Myers et al, 2021). Bringing these ideas together, habitat filtering tends to be the guiding force in fish assemblages, having stronger effects based on the characteristics of local sites (Richardson et al, 2017;Valleé et al, 2019).…”

Black coral forests enhance taxonomic and functional distinctiveness of mesophotic fishes in an oceanic island: implications for biodiversity conservation

“…Despite hosting different species composition, mesophotic reefs filled a comparable volume of the trait space (i.e., functional richness), irrespective of the habitat, suggesting the maintenance of a similar range of trait combinations. This common 'backbone' appears to be a common feature of reef fish assemblages across latitudinal and depth gradients across disparate biogeographic regions 27,45,46 , suggesting the maintenance of a set of traits that underpin core ecosystem functions mediated by fishes 47 . Yet, when accounting for the distribution of species abundances, we found marked differences between the mesophotic strata and their shallower counterparts, a result that was driven by the presence of BCFs.…”

Institute Profile: Victoria University of Wellington's Coastal Ecology Laboratory—A Uniquely Situated Research Facility for Subtidal and Intertidal Biology

“…There are several key areas of research focus for staff at the Coastal Ecology Laboratory. These include a strong focus on climate change research (Micaroni et al 2022; Krieger et al 2023), population and community ecology (Shima and Swearer 2016; Carrington et al 2021; Bell et al 2022), and fisheries/marine protection (Eddy et al 2014; Rogers et al 2018; Durante et al 2022). Although we are situated in the temperate zone, we also have a strong focus on coral reef biology, with most of our academics comparing temperate and tropical ecosystem trends in community ecology, eco‐physiology, climate change impacts, and fisheries.…”