MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps12354

A 'fuzzy clustering' approach to conceptual confusion: how to classify natural ecological associations

Dario Fiorentino*, Roland Pesch, Carmen-Pia Guenther, Lars Gutow, Jan Holstein, Jennifer Dannheim, Brigitte Ebbe, Tim Bildstein, Winfried Schroeder, Bastian Schuchardt, Thomas Brey, Karen Helen Wiltshire

*Email: dario.fiorentino@awi.de

ABSTRACT: The concept of the marine ecological community experiences renewed attention, mainly owing to a shift in conservation policies from targeting single and specific objectives (e.g., species) towards integrated approaches. Despite the value of communities as distinct entities, e.g. for conservation purposes, there is still an ongoing debate on the nature of species associations. They are seen either as communities, cohesive units of non-randomly associated and interacting members, or as assemblages, groups of species randomly associated. We investigated such dualism using fuzzy-logic applied to a large dataset in the German Bight (south-eastern North Sea). We identified areas with either structured or random species associations and mapped boundaries between communities or assemblages in a more natural way. We described the impact of the chosen sampling design on the community identification. Four communities, their core areas and probability of occurrence were identified in the German Bight: AMPHIURA-FILIFORMIS, BATHYPOREIA-TELLINA, GONIADELLA-SPISULA, PHORONIS. They were assessed by estimating overlap and compactness and supported by analysis of beta-diversity. 62% of the study area was characterized by high species turnover and instability. These areas are very relevant for conservation issues, but become undetectable when studies choose sampling design with little information or at small spatial scales.