Community variability and ecological functioning: 40 years of change in the North Sea benthos

Abstract

Using established associations between species traits (life history, morphological and behavioural characteristics) and key ecological functions, we applied biological traits analysis (BTA) to investigate the consequences of 40 years of change in two North Sea benthic communities. Ecological functioning (trait composition) was found to be statistically indistinguishable across periods that differed significantly in taxonomic composition. A temporary alteration to functioning was, however, inferred at both sampling stations; coinciding with the North Sea regime shift of the 1980s. Trait composition recovered after 1 year at the station located inside the grounds of a trawl fishery, whereas the station located outside the main area of fishing activity underwent a six-year period of significantly altered, and temporally unstable, trait composition. A further alteration to functioning was inferred at the fished station, when the population of a newly established species rapidly increased in numbers. The results suggest that density compensation by characteristically similar (redundant) taxa acts to buffer changes to ecological functioning over time, but that functional stability is subject to aperiodic disruption due to substitutions of dissimilar taxa or uncompensated population fluctuations. The rate at which ecological functioning stabilises and recovers appears to be dependent on environmental context; e.g. disturbance regime.

Four decades of functional community change reveals gradual trends and low interlinkage across trophic groups in a large marine ecosystem

“…To our knowledge, this is the first study comparing long‐term trends and multi‐decadal dynamics in multiple dimensions of functional community change across trophic groups and areas. Previous trait‐based studies on long‐term functional community change have focused on single organism groups separately, either zoobenthos (Gogina, Darr, & Zettler, ; Neumann & Kröncke, ; Veríssimo et al, ; Weigel, Blenckner, & Bonsdorff, ) or fish (Baptista, Martinho, Nyjtrai, Pardal, & Dolbeth, ; Barcelo, Ciannelli, Olsen, Johannessen, & Knutsen, ; Dencker et al, ; Frelat et al, ), and particularly multi‐trait compositional changes on local scale (Clare, Robinson, & Frid, ; Frid & Caswell, ).…”

“…Third, our results also show that an assessment of dynamics, that is trait turnover and multi‐trait compositional changes, in addition to the functional indices, is of importance for understanding the potential rate of change and type of functional change (identity of traits) that has occurred. Changes in trait composition have proven valuable for informing on long‐term changes in potential functioning in previous single trophic group studies, for example in North Sea zoobenthic infauna (Clare et al, ) and epifauna communities (Neumann & Kröncke, ) or coastal fish assemblages (Barcelo et al, ). In this study, long‐term changes in feeding habit and size where generally observed, suggesting potential shifts in the benthic and pelagic energy pathway (SuppInfo A: Table S5), specifically during certain time periods (SuppInfo B: Fig.…”

Fish communities diverge in species but converge in traits over three decades of warming

“…Yet, examining changes in taxonomic and trait diversity simultaneously may best describe community dynamics (Dencker et al, ; Monnet et al, ; Villéger, Miranda, Hernández, & Mouillot, ). For instance, changes in species composition may not lead to changes in trait diversity if loser species are replaced by species with similar traits (Clare, Robinson, & Frid, ; Villéger et al, ; White, Montgomery, Storchová, Hořák, & Lennon, ). Conversely, declines of a few rare species with unique trait values may have major impacts on trait diversity without notable changes in species composition (Mouillot, Bellwood, et al, ; Mouillot et al, ; Violle et al, ).…”

Maintained functional diversity in benthic communities in spite of diverging functional identities

“…Functional diversity is sometimes used as the sole explanatory variable for ecosystem functioning, which on the one hand has been shown to be a stronger predictor than species richness in many circumstances, but on the other omits information on the actual underlying functional structure (the functional identity), leaving it open which functions may or may not be present and to which degree they are expressed (Gagic et al ). There are surprisingly few studies available where the traditional taxonomic approach of changing faunal communities is assessed in combination with a functional framework on empirically collected data (van der Linden et al , Clare et al ). This is however an asset for understanding the potentially changing functionality within a system along environmental change.…”