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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]

Abstract: The recovery of macrofaunal communities after marine aggregate dredging was assessed using both traditional indices (abundance, biomass and species diversity), and functional analysis techniques (Somatic Production, Taxonomic Distinctness, Infaunal Trophic Index, Biological Traits Analysis and Rao''s Quadratic Entropy). A previously dredged area (Area 222), located off the southeast coast of England was selected for this investigation. Area 222 was split into sites that had been subjected to relatively high dredging intensity, relatively low dredging intensity, and undisturbed reference areas. Both traditional and functional analyses indicated that macrofauna at the low dredging intensity site had fully recovered at least 7 years after the dredging ceased. Recovery times at the high intensity site had a greater variability and most of the techniques recorded the recovery had yet to take place even 11 years after the dredging had ceased. Since Area 222 was dredged for a long period of time (approx. 25 years), it is suggested that a longer time series of study be carried out so that the definitive recovery period in this high intensity site can be determined. While a longer time series study is not always a realistic or cost effective, the present study could be useful to facilitate the selection of metrics to support in the assessment of macrofaunal recovery. [Copyright &y& Elsevier]

Previous work in the Ria Formosa Lagoon has revealed that it is possible to use macrofauna community structure as an indicator of contamination effects. Communities at sites adjacent to sewage outfalls indicated contamination but no pollution gradients were observed. In this study, macrofauna within a sub-section of the earlier work were investigated to determine the extent of mesoscale (10–100 m) variability and new indices of biological community structure. The results were evaluated using univariate (Marine Biotic Index; BI) and multivariate statistical methods (PCA). The computer program Barrier (usually used with genetic data) was also applied to detect “barriers” between spatially referenced samples. PCA identified the most significant factor effecting the distribution of the organisms in the study area to be the mud content of the sediment (% [ABSTRACT FROM AUTHOR]