Biological traits of marine benthic invertebrates in Northwest Europe

Metabarcoding identifies macroalgal composition as a driver of benthic invertebrate assemblages in restored habitats

Large brown macroalgal forests support diverse communities of associated invertebrates. However, human activities have led to their degradation, replacing the original macroalgal assemblages with less-complex habitats and altering the associated invertebrate communities. To counteract this, restoration actions are currently being performed aiming at their recovery. Here, we used metabarcoding of the COI gene to describe the invertebrate community of a 10-year restored macroalgal forest dominated by Gongolaria barbata. This invertebrate assemblage was compared with an assemblage adjacent to the restoration site where G. barbata is absent, and two healthy assemblages also dominated by G. barbata, used as references. Results showed that arthropods, molluscs, and annelids were the most abundant groups. Specific MOTUs representing sponge and ascidian species were exclusively found in G. barbata assemblages, suggesting that the restoration particularly benefited some of these organisms. Crustaceans and molluscs, however, were similarly abundant across assemblages, including the one dominated by photophilous macroalgae (without G. barbata), thus indicating that these mobile groups may equally colonise these alternative habitats. The overall composition of the restored assemblage did not completely resemble references, suggesting that recovering all associated diversity is a complex process, most likely influenced by multiple factors that require further investigation.

Towards Greater Standardisation in Benthic Trait Research to Support Application to Environmental Management

Functional trait-based approaches have enriched our understanding of key ecological processes such as species assembly and biodiversity loss. This focus on traits, rather than taxonomy, promotes comparability across spatial and organisational scales, further enabling the application of trait-based methodologies to systems where species identity is difficult to recognise. Among other issues, however, the lack of standardisation is preventing trait-based approaches from unlocking their true potential. Here, 407 published articles (peer-reviewed and grey literature) are reviewed alongside the Biological Traits Information Catalogue (BIOTIC) to document inconsistencies in the understanding and use of trait terminology in the context of marine benthic ecosystems. Firstly, discrepancies in the operationalisation of key concepts are noted, each associated with six to ten separate definitions. Secondly, three distinct trait classification frameworks are identified, of which one presents considerable internal variation; within-framework trait classification also emerges as inconsistent. Lastly, a total of 290 synonyms and associated modalities are noted with respect to 18 traits commonly implemented in benthic research, amounting to an average of 16 synonyms per trait. Researchers should be aware of such inconsistencies; to overcome them, we propose a set of guidelines aimed at standardising the reporting and classification of traits in benthic research for policy and management applications. As other standards may exist, we further present a 'translation' table intended for use by trait ecologists when reviewing existing literature that adheres to different trait classification frameworks than the ones we recommend. Standardising the reporting and storage of trait data will help align our understanding of the function of benthic assemblages, their role in delivering ecosystem services, and the impact of human activities on ecosystem function.

Overcoming challenges to access ecological function: a marine soft-bottom perspective

Ecosystem functioning studies have gained prominence due to concerns about the decline of species. In marine sediments, benthic invertebrates perform important ecological functions. However, the challenges within the field of functional ecology are sparsely discussed. Our aim was to systematize the problems and suggest pathways forward. To achieve this, we review recent articles on functional ecology on marine sediments and identified two main issues. First, the absence of a clear definition of terms. Second, in terms of applicability, we observed a mismatch between the scales of functioning and traits, incomplete information on trait databases, inappropriate selection of traits, subjective measures of traits, overlooked trait variability and data analyses without the link between the taxonomy and the traits associated with functions. We propose some pathways to overcome the challenges, such as (i) reasoning of the concept of function, process and trait, (ii) increasing experiments to measure functions, (iii) clarification of the relationship between traits and functions, (iv) clear procedure for assigning trait scores, (v) experiments for understanding trait variability and function performance, and (vi) analyses that consider the sets of traits of each taxon. Overcoming these challenges will allow us to advance research and fill gaps in knowledge of ecosystem functioning.

Environmental influence on the functional ecological structure of benthic macrofaunal communities of the northwest Iberian coast

Evaluating the functional structure of benthic macrofaunal communities provides insights into how environmental drivers shape the ecosystem and establishes a baseline knowledge of the communities' dynamics and functioning. This understanding allows the prediction of responses to environmental changes and the implementation of efficient conservation and management strategies. Here we examine the structures and functions of benthic macrofaunal communities on the Northwest Iberian coast concerning environmental factors such as depth, hydrodynamic energy, and bottom type. The results suggest that the community assemblages and their function are structured by factors which influence food availability and habitat heterogeneity. The different sites exhibited different trait compositions and functional structures, indicating that distinct functions are performed according to environmental conditions. The communities found in sandy bottom areas with low hydrodynamic conditions presented frail functionality and demonstrated high vulnerability to alterations in their environment. Conversely, the communities found in rocky bottoms with high hydrodynamic conditions exhibited a fulfilled functional niche space, rendering them more resilient to such changes and less prone to loss of function. Although the analyses did not reveal significant differences in the factor depth, its influence on several factors seems relevant in shaping the functional structure of the communities. These findings highlight the importance of understanding the impact of local environmental conditions on ecosystem functioning, to effectively implement monitoring, management, and conservation strategies.

Fauna - Microplastics interactions: Empirical insights from benthos community exposure to marine plastic waste

Microplastic deposition in soft marine sediments raises concerns on their role in sediment habitats and unknown effects on resident macrobenthic communities. To assess the reciprocal influence that MPs and macrobenthos might have on each other, we performed a mesocosm experiment with ambient concentrations of environmental Polyethylene (PE) and a non-manipulated, natural macrobenthic community from the Belgian part of the North Sea (BPNS). Our results show that PE fragments increase mortality of abundant bivalves (specifically Abra alba) after 30 days of exposure but not for the most abundant polychaete Owenia fusiformis, possibly due to its predominant suspension feeding behavior. Fast burial of surface MPs exposes deep-dwelling burrowers to the pollutant, however reducing the amount of MPs interacting with (sub) surface living fauna. We conclude that macrobenthos promotes the sequestration of deposited MPs, counteracting resuspension, and can have cascading effects on biodiversity due to their effect on abundant and functionally important species.

Oil and gas platforms degrade benthic invertebrate diversity and food web structure

Oil and gas exploitation introduces toxic contaminants such as hydrocarbons and heavy metals to the surrounding sediment, resulting in deleterious impacts on marine benthic communities. This study combines benthic monitoring data over a 30-year period in the North Sea with dietary information on >1400 taxa to quantify the effects of active oil and gas platforms on benthic food webs using a multiple before-after control-impact experiment. Contamination from oil and gas platforms caused declines in benthic food web complexity, community abundance, and biodiversity. Fewer trophic interactions and increased connectance indicated that the community became dominated by generalists adapting to alternative resources, leading to simpler but more connected food webs in contaminated environments. Decreased mean body mass, shorter food chains, and the dominance of small detritivores such as Capitella capitata near to structures suggested a disproportionate loss of larger organisms from higher trophic levels. These patterns were associated with concentrations of hydrocarbons and heavy metals that exceed OSPAR's guideline thresholds of sediment toxicity. This study provides new evidence to better quantify and manage the environmental consequences of oil and gas exploitation at sea.

A roadmap to define and select aquatic biological traits at different scales of analysis

Trait-based approaches are a powerful tool, as they not only improve understanding of ecological complexity and functioning but also allow comparison across different ecosystems and biogeographical regions. They may be used to unveil ecosystem processes and assess community structures, but their great potential becomes limited when dealing with scattered trait data and historically unstandardised trait nomenclature. The lack of standardisation allows authors to use the terminology of their preference, which inevitably leads to ambiguous misunderstandings and limits comparison between different studies. There have been some attempts to organise the trait vocabulary, but even these are mostly created from the perspective of a single ecosystem, which limits their applicability. In this work, we conducted a systematic literature review that identified and compiled 1127 traits across 37 datasets of fishes, invertebrates and zooplankton from freshwater, marine and transitional ecosystems. This dataset was then used to build on the Marine Species Traits Wiki and to propose a new, unified approach to a trait vocabulary based directly on readily available trait data. We propose a single standardised designation for all the different traits identified and provide a list of all the different synonyms commonly used for these traits. A roadmap to help the trait selection process is also provided, offering a guide through four main steps and important questions for choosing an adequate set of traits at the beginning of any study, which constitutes one of the main challenges in functional ecology research. Overall, this proposal will provide a solid baseline for tackling gaps in trait nomenclature and ensuring a clearer future for functional ecology studies.

The seafloor from a trait perspective. A comprehensive life history dataset of soft sediment macrozoobenthos

Biological trait analysis (BTA) is a valuable tool for evaluating changes in community diversity and its link to ecosystem processes as well as environmental and anthropogenic perturbations. Trait-based analytical techniques like BTA rely on standardised datasets of species traits. However, there are currently only a limited number of datasets available for marine macrobenthos that contain trait data across multiple taxonomic groups. Here, we present an open-access dataset of 16 traits for 235 macrozoobenthic species recorded throughout multiple sampling campaigns of the Dutch Wadden Sea; a dynamic soft bottom system where humans have long played a substantial role in shaping the coastal environment. The trait categories included in this dataset cover a variety of life history strategies that are tightly linked to ecosystem functioning and the resilience of communities to (anthropogenic) perturbations and can advance our understanding of environmental changes and human impacts on the functioning of soft bottom systems.

Mapping marine benthic biological traits to facilitate future sustainable development

Escalating societal demands placed on the seabed mean there has never been such a pressing need to align our understanding of the relationship between the physical impact of anthropogenic activities (e.g., installation of wind turbines, demersal fishing) and the structure and function of the seabed assemblages. However, spatial differences in benthic assemblages based on empirical data are currently not adequately incorporated into decision-making processes regarding future licensable activities or wider marine spatial planning frameworks. This study demonstrates that, through harnessing a Big Data approach, large-scale, continuous coverage maps revealing differences in biological traits expressions of benthic assemblages can be produced. We present independent maps based on a suite of response traits (depicting differences in responses to natural or anthropogenically induced change) and effects traits (reflecting different functional potential), although maps derived using single traits or combinations of a range of traits are possible. Models predicting variations in response traits expression provide greater confidence than those predicting effects traits. We discuss how such maps may be used to assist in the decision-making process for the licensing of anthropogenic activities and as part of marine spatial planning approaches. The confidence in such maps to reflect spatial variations in marine benthic trait expression may, in the future, inherently be improved through (1) the inclusion of more empirical macrofaunal assemblage field data; (2) an improved knowledge of marine benthic taxa trait expression; and (3) a greater understanding of the traits responsible for determining a taxon's response to an anthropogenic pressure and a taxon's functional potential.

NZTD - The New Zealand Trait Database for shallow-water marine benthic invertebrates

Macrobenthic traits, for example feeding mode, life history, morphology, are increasingly used for determining responses of macrobenthic fauna to environmental change and influences on ecosystem functioning. Yet, trait information is scarce or non-existent in several parts of the world, such as New Zealand. This deficit makes collecting trait data a difficult and time-consuming task, limiting its potential use in trait-based assessments. Here, we present the New Zealand Trait Database (NZTD) for marine benthic invertebrates, the first comprehensive assessment of macrobenthic traits in New Zealand. The NZTD provides trait information for more than 700 macrobenthic taxa, categorised by 18 traits and 77 trait modalities. The NZTD includes five freely downloadable datasets, (1) the macrobenthic trait dataset, with outcomes from a fuzzy coding procedure, (2) the trait source information, (3) the references by taxa, (4) the full references list, and (5) the full taxa list used in the NZTD. Establishing the NZTD closes the trait knowledge gap in New Zealand and facilitates future research applying trait-based approaches to New Zealand's coastal macrofauna.