A General-Purpose Biotic Index to Measure Changes in Benthic Habitat Quality across Several Pressure Gradients

Abstract

Realistic assessments of the ecological status of benthic habitats, as requested by European directives such as the Water Framework Directive and the European Marine Strategy Framework Directive, require biotic indices capable of detecting anthropogenic impact without having preliminary knowledge of the occurring pressures. In this context, a new general-purpose biotic index (GPBI) based on the deviation of benthic macrofauna community composition and structure from a valid reference (i.e., good ecological status) is proposed. GPBI is based on the assumption that as a site becomes impacted by a pressure, the most sensitive species are the first to disappear, and that stronger impacts lead to more important losses. Thus, it explicitly uses the within-species loss of individuals in the tested station in comparison to one or several reference stations as the basis of ecological status assessment. In this study, GPBI is successfully used in four case studies considering the impact of diversified pressures on benthic fauna: (1) maerl extraction in the northern Bay of Biscay, (2–3) dredging and trawling in the North Sea, and (4) hypoxic events at the seafloor in the Gullmarfjord. Our results show that GPBI was able to efficiently detect the impact of the different physical disturbances as well as that of hypoxia and that it performs better than commonly used pressure-specific indices (M-AMBI and TDI). Signal detection theory was used to propose a sound good/moderate ecological quality status boundary, and recommendations for future monitoring are also provided based on the reported performance of GPBI.

Megabenthic invertebrate diversity in Mediterranean trawlable soft bottoms: a synthesis of current knowledge

“…Over the years, megabenthos in trawl surveys has gained more attention as a primary tool for providing data useful per se for the assessment of fish communities and ecosystems (Cotter et al, 2009). Subsequently, the survey scope has broadened from demersal species populations to their communities and more recently to the sensitivity of species and communities to trawling impact (González-Irustra et al, 2018;Rijnsdorp et al, 2018;Jac et al, 2020aJac et al, , b, 2021Labrune et al, 2021). And, despite the fact that since 2012 benthos has been introduced in the MEDITS protocol, this was only on a voluntary basis, thus resulting to the collection of fragmentary information based on the degree of specialisation of each scientific team.…”

Ecological quality assessment: A framework to report ecosystems quality and their dynamics from reference conditions

“…The definition of quantitative, data‐driven, reference conditions requires sampling designs similar to those underpinning long‐term monitoring (Tomczak et al, 2022). Such assumptions have been recently summarized by Labrune et al (2021): (1) reference stations should be defined within a same or at least a similar ecological entity (Borja et al, 2012); (2) a set of reference stations is preferable that one station, as it allows a better integration of the spatial variability of reference conditions (Lavesque et al, 2009); (3) even if they do not represent an optimum, historical data may represent an alternative in the absence of reference stations (Borja et al, 2012; Tomczak et al, 2022); (4) shifting‐baselines claims for a synchronous monitoring of both potential references and tested stations over longer time periods to highlight their dynamics and disentangle natural from anthropogenic drivers (Basset et al, 2013; Hess et al, 2020). If fulfilled, these assumptions require analytical tools tailored to deal with this design.…”

“…These approaches have also proven to be limited in assessing the effect of anthropogenic disturbances in naturally stressed ecosystems, such as estuaries (Elliott & Quintino, 2007). In response, indices based on the deviation of the taxonomic composition of tested community with respect to stations of reference have been developed (Flåten et al, 2007; Johnson et al, 2008; Labrune et al, 2021) but defining thresholds remains a challenge to determine the achievement of reference conditions: that is, distinguish stations that meet reference conditions from those that do not meet them, with respect to ecological quality ratios generally ranging from 0 to 1 (Hiddink et al, 2023). What is an acceptable ecological quality assessment?…”

“…For a long time, biodiversity indices have remained the main way for reporting ecological quality. Scientists, stakeholders, and administrative bodies requirement for a synthetic approach to the assessment of ecosystems quality have favored a still ongoing development of biotic indices devoted to synthesize community responses to perturbations and ecological quality assessment (EQA) (Blandin, 1986; Buckland et al, 2005; Diaz et al, 2004; Labrune et al, 2021; Washington, 1984). Some of these biotic indices integrate multivariate data into a single, site‐specific, numeric score that can be straightforwardly interpreted by nonspecialists within a “good” versus “bad” range of values, most often in relation with legislative requirement (Diaz et al, 2004).…”

Ecosystem-based assessment of a widespread Mediterranean marine habitat: The Coastal Detrital Bottoms, with a special focus on epibenthic assemblages

“…Their conservation value is recognized under EU rules and international conventions (Barbera et al, 2003;Salomidi et al, 2012). Marion (1883); Meinesz et al (1983); Holon and Harmelin (2014) and La Rivière et al (2021) described a CDB facies with large calcified bryozoans, such as Pentapora fascialis (Pallas, 1766), Smittina cervicornis (Pallas, 1766), Turbicellepora avicularis (Hincks, 1860), Hornera spp. Lamouroux, 1821, etc., but the highest diversity of bryozoans on CDB is found among small species (Harmelin, 2017).…”