Comparison of functional diversity of two Alaskan Arctic shelf epibenthic communities

Abstract

Alaskan Arctic shelf communities are currently experiencing dramatic changes that will likely affect ecosystem functioning of Arctic marine benthic communities. Here, functional diversity based on biological traits was used to assess differences and similarities in ecosystem functioning between 2 shelf systems that are geographically close but vary in many environmental influences: the Arctic Beaufort and Chukchi Sea epibenthic communities. We hypothesized that (1) patterns of functional composition and diversity metrics reflect patterns in taxonomic composition and diversity metrics in these 2 shelf communities; and (2) patterns in functional diversity metrics are distinct between the 2 shelves. We evaluated 9 biological traits (body form, body size, feeding habit, fragility, larval development, living habit, movement, reproductive strategy, sociability) for 327 taxa in 2014 and 2015. For each trait, multiple modalities (specific expressions within a trait) were considered. Patterns in functional diversity metrics on both shelves reflected those in taxonomic diversity metrics. However, shelf communities were more similar in functional- than in taxonomic composition. Beaufort Sea communities had higher functional dissimilarity and functional evenness driven by differences in the modalities within body form, body size, larval development, and reproductive strategy. These traits primarily affect nutrient cycling, energy turnover, and recovery from disturbances, suggesting a stronger potential for future maintenance of ecosystem function, and indicating a more even use of resources in the Beaufort Sea. The combination of functional and taxonomic diversity metrics enabled a comprehensive understanding of how ecological niche space is used and how epibenthic communities function in Alaskan Arctic shelf systems.

Functional Pattern of Benthic Epifauna in the Chukchi Borderland, Arctic Deep Sea

“…In contrast, higher FR at the deeper stations is, in turn, likely related to the homogeneity of the abyssal environment to which epifauna appear to have adapted by fewer and shared trait modalities. Low FR at mid-depth stations may render these areas less resilient to ongoing and future change and potential human use as functions may be lost when species loss occurs (Loreau, 2008;Van der Linden et al, 2016), a conclusion consistent with studies on Arctic benthic macrofauna (Kokarev et al, 2017;Liu et al, 2019;Sutton et al, 2020). In addition, modalities such as sessile, attached, and upright body form at these stations point to higher vulnerability of mid-depth epifauna to predation, disturbances or decreases in food availability (Degen and Faulwetter, 2019).…”

“…Nine commonly used traits represented by a total of 39 modalities were chosen for the present analysis following established definitions by Bremner et al (2006), Costello et al (2015), Degen et al (2018), and Sutton et al (2020) (Table 2). The traits reflected morphology (adult size, body form), behavior (living habitat, mobility, adult movement, feeding habit, substrate affinity) and life-cycle characteristics (larval development and reproduction) (Table 2; reviewed by Martini et al, 2020a).…”

“…The average adult size of a given species across all stations was used for the analysis. As information about biology and behavior of many epifaunal taxa in the Arctic deep sea remains limited or is at times non-existent at the species level, coding of these taxa was conducted based on information available for closely related species in the same genus or family (following, e.g., Faulwetter et al, 2015;Rand et al, 2018;Sutton et al, 2020). In a few cases, modalities common at even higher taxonomic rank (such as direct development in Peracarida) were applied.…”

“…mostly on the shelves and for macrofauna (i.e., mostly infaunal taxa ≥0.5 or 1 mm) (Cochrane et al, 2012;Krumhansl et al, 2016;Kokarev et al, 2017;Rand et al, 2018), while few studies have so far focused on biological traits of epifaunal megafauna (i.e., invertebrates and demersal fish on top of the sediment and typically ≥ ca. 5 mm) (Sutton et al, 2020) or deep ecosystems (Degen, 2015;Liu et al, 2019). Functional patterns have not been examined for epifaunal communities anywhere in the Arctic deep sea.…”

“…Overview of traits and their modalities used in the present paper.Slightly adjusted fromBremner et al (2006),Degen et al (2018),Costello et al (2015), andSutton et al (2020).…”