Structural and functional diversity patterns of macrofaunal communities from a semi-enclosed inlet of Northeast Atlantic: The influence of environmental conditions.

Comprehending the mechanisms and circumstances responsible for the dynamics of biological communities is a fundamental step for predicting responses to environmental changes as well as efficient conservation and management efforts. Macrofaunal assemblages support a wide range of ecosystem services, serving as integral components of the biogeochemical cycle. Here, we examine the structure of the subtidal macrofaunal community in a semi-enclosed bay system located in the Northeast Atlantic. Employing a functional approach, our aim is to understand the interplay between water depth, geographical position, colonisation development and the communities. Our findings did not reveal the influence of water depth (range of 4 m–12 m) on the functional structures of the communities. Instead, only significant differences were demonstrated for 'time of colonisation' and 'site'. The community with 1 month of colonisation presented limited functional diversity lacking overall ecological resilience. It was mainly characterised by 'small-sized', 'short-lived', 'mobile', and 'deposit-feed' organisms indicating an incipient state of development. Communities Site 2 and Site 3 revealed significant differences in the functional structure of the communities. They exhibited similar levels of functional diversity, yet significant differences emerged in the Biological Trait Analysis. Community Site 2 was characterised by 'sessile', 'long-lived', 'large-sized' 'suspension feed' while community Site 3 was characterised by 'herbivore/grazer', 'tubicolous', and 'medium-lived' organisms. Site 2 focuses on the transport of elements from pelagos to the benthos and from benthos to pelagos while Site 3 focus on the transport of elements within the benthos and from benthos to pelagos, and effectively contributes to decomposition and resuspension processes. Moreover, they differ in their sensitivity to disturbance, which suggests that their location in the Ría influences the functional composition of the communities. Understanding these patterns within this environment of significant ecological and economic importance holds profound implications for the effective preservation of ecosystem services. • Functional analysis on the structure of the macrofaunal communities in a semi-enclosed bay system of the Northeast Atlantic. • Standard methodology wherein artificial substrates mimic a 3D complex habitat, avoid destructive sampling effectively. • Biological traits analysis reveals distinct trait patterns as it explores community relations and environmental conditions. • Traits offer distinct details into macrofaunal communities' dynamics, which traditional community analysis fails to uncover. [ABSTRACT FROM AUTHOR]