Description: Bioturbation is one of the key mediators of biogeochemical processes in benthic habitats that can have a high contribution to seafloor functioning and benthic pelagic coupling in coastal waters. Previous studies on bioturbation were limited to point locations and extrapolations in single regions, but have not accounted for regional differences under changing environmental conditions, though there are indications that species contributions will differ across regions or with biotic and abiotic context. To capture those differences and assess global patterns and commonalities, multi-regional analyses are imperative. Here for the first time, bioturbation potential (BPc), a functional indicator of benthic community bioturbation, was estimated based on macrofauna data from four regions (i.e. German Baltic Sea, German North Sea, Belgian part of the North Sea and the Eastern English Channel). For each region and sediment type we identified key species contributing to BPc. Comparison within and across regions demonstrated regional differences, and both overlap and mismatch between species that are functionally important and those that are dominant in biomass. Knowledge on the functionally important species is crucial when management objectives include the protection of certain ecosystem functions. Available environmental layers were used as predictors to model the spatial distribution of BPc for each area and to explore the underlying drivers of differences. Random forest models were trained using as response variables either i) BPc initially calculated per station; or ii) BPp – the species-specific contribution to BPc – for key species (with subsequent summation of their predicted full-coverage distributions to BPc). Maps of BPc distribution predicted by random forest were compared with those generated using natural neighbour interpolation. Overall, derived BPc values increased towards the German parts of the North and Baltic Seas. The relevance of BPc for ecosystem processes and functions, however, vary with biotic and abiotic settings. Results revealed a strong association of BPc with species diversity and region, but less with sediment grain size. A large range of BPc occurred when species richness was low. This suggests that the provisioning of high bioturbation activity is possible also under low diversity, where it is vulnerable due to reduced resilience. The executed multi-regional analysis allowed identifying regional differences in performance of macrofauna, suggesting the need for regionspecific conservation and management strategies. https://doi.org/10.1016/j.ecolind.2019.105945 Received 26 July 2019; Received in revised form 12 November 2019; Accepted 14 November 2019 ⁎ Corresponding author. E-mail address: mayya.gogina@io-warnemuende.de (M. Gogina). Ecological Indicators 110 (2020) 105945 1470-160X/ Crown Copyright © 2019 Published by Elsevier Ltd. All rights reserved. T

Description: Macrofaunal sediment reworking activity is a key driver of ecosystem functioning in marine systems. So far sediment reworking rates can only accurately be assessed by measurements as inference from community parameters is limited. In this case study we test the applicability of 2-D optical florescent sediment profile imaging (f-SPI) on multi corer type incubation cylinders. f-SPI has to date been applied to flat-surfaced (i.e. rectangular) cores only, while multi corer type incubation cylinders were analyzed by the spatially low resolved and invasive slicing technique. Here we apply both methods to cylindrical sediment cores (10 cm diameter). Cores were taken from by two common communities (i.e. Nucula-community and Amphiura-community) in the southern German Bight. Both f-SPI and the slicing technique showed similar vertical luminophore profiles. However the slicing technique found no significant differences between the two communities, whereas f-SPI showed significant differences for all investigated sediment reworking parameters: sediment reworking rate, non-locality index, mean weighted luminophore depth, and the maximal luminophore depth. Consequently, this may lead to different conclusions about the sediment reworking behaviors of the two communities. Likely the slicing method failed to detect significant differences between the Nucula- and Amphiura-community, owing to insufficient spatial accuracy. The f-SPI method, on the other hand, did not capture the full extent of maximal sediment reworking depth due to wall-effects. We conclude that both methods have specific drawbacks and advantages. While slicing is preferable when focusing on the absolute maximal sediment reworking depth especially with predominantly sessile communities, f-SPI is better suited to capture general sediment reworking patterns of most other communities. We demonstrate further that the bias, which is introduced by the distortion effect on imaging due to optical perspective and cylinder wall curvature of rounded cylinders using f-SPI, is negligible. Accordingly our results indicate that the distortion effects by curvature of the rounded cylinder walls will not cause underestimations of sediment reworking parameters in the f-SPI approach. Consequently f-SPI is suitable for the investigation of sediment reworking in natural communities by means of multi corer type samples.

Description: Benthic organisms and their bioturbation activities have a profound effect on a multitude of sediment properties. While many studies have already explored benthic impacts at small temporal and spatial scales, little is known on how the small-scale effects accumulate and interactively guide large-scale (km-scale) morphological evolution. Here we firstly summarize the most important processes of benthos affecting sediment stability and then explore existing biomorphodynamic modeling studies both at small- and large-scales. In general, microbenthos (body size 〈0.1 mm) mainly stabilizes sediments while meio- (0.1–1 mm) and macrobenthos (〉1 mm) may stabilize or destabilize sediments. Among all types of sediment, fine-grained fraction (silt and clay) is most sensitive to the impact of benthos. Benthic organisms have the capability to mediate sediment transport and sedimentation patterns beyond their habitats on the long-term and over a large-scale. However, so far, numerical models evaluating benthic impact are limited to explorative studies and have not reached a stage where they can be used for predictive modeling. The barriers hindering a further development of biomorphodynamic models include not only limited understanding of fundamental biological/bio-physical processes affecting morphological development and dynamic feedback loops among them but also a shortage of data for model calibration and confirmation of simulation results. On the other hand, thriving for higher model complexity does not necessarily lead to better performance. Before conducting biomorphodynamic modeling, researchers must figure out which questions can be answered in a meaningful sense with simulation results that can be compared with observations and which level of modeling complexity is sufficient for that purpose.