Description: Increasing anthropogenic activities on land and at sea underline the demand for easily applicable indices to effectively predict human mediated changes in ecosystem functioning. Here, we propose a novel bioirrigation index (IPc) that is based on body mass, abundance, burrow type, feeding type and injection pocket depth of bottom dwelling animals. Results from both community and single-species experimental incubations indicate that IPc is able to predict the bioirrigation rate in different sediment types (mud, fine sand, sand). Further, IPc increased the predictability of biogeochemical cycling (i.e. changing concentrations of phosphate, silicate, ammonium, nitrate and nitrite) under different environmental conditions (i.e. sediment type, temperature, faunal inventory, gradients across the sediment water interface), compared to trait based bioturbation potential (BPc). The trait-based index thus demonstrated robustness in the prediction of animal-mediated functional processes that support biogeochemical functions. Additionally our results confirm that biogeochemical cycling is more closely linked to irrigation traits than to sediment reworking traits. Based on these findings we argue that trait-based indices provide a useful tool for the prediction of ecosystem processes as effect traits provide a direct link to the behavioral mechanisms that drive ecosystem functioning.

Description: Macrofaunal bioturbation is an important mechanism for the enhancement of remineralization and biogeochemical cycling in marine sediments. Reduction of bioturbation activity may accordingly have far-reaching negative implications for general ecosystem performance. This is especially the case for shallow shelf seas, such as the German Bight, which account for 50% of global benthic remineralization, although they cover only 7% of the total sea surface. Increasing anthropogenic activities (e.g. wind farm construction) in these shallow shelf seas have intensified the need for reliable quantifications and predictions of macrofaunal bioturbation activities and resulting biogeochemical processes. The aim of this thesis was,thus, to develop easily applicable concepts that allow for the quantification of sediment reworking and the prediction of bioirrigation. In order to simplify the quantification of sediment reworking, which can so far only be assessed experimentally, I compared two of the most commonly applied methods (sediment profile imaging (SPI) and standard slicing technique (ST)). In addition, the time-saving and easily applicable SPI method was tested for its suitability to assess sediment reworking from cylindrical multi-corer samples (Manuscript I). The results suggested that SPI is suitable and even more accurate than ST for the investigation of sediment reworking activity. This omits the previously necessary need for timeconsuming slicing or the complex transfer into rectangular aquaria. These findings will facilitate studies on spatiotemporal patterns of sediment reworking activity in the German Bight. Such studies are of special interest as the bioturbation potential (BPc), which was previously often applied to estimate the potential of communities to rework the sediment, does not correlate with actual sediment reworking rates (Manuscript II). Surprisingly BPc, which includes sediment reworking traits (i.e. mobility and reworking mode) but no specific bioirrigation traits, rather correlated with bioirrigation activity and nutrient fluxes of silicate, ammonium, nitrate, and nitrite (Manuscript II). To overcome ambiguity of BPc, I developed the irrigation potential (IPc), as an adaptation from BPc (Manuscript III). By incorporation of bioirrigation effect traits (i.e. burrow type, feeding type, injection pocket depth), IPc was specifically designed to predict bioirrigation and its influence on biogeochemical processes (Manuskript III). I could demonstrate that, in contrast to BPc, the modified index provides an accurate quantitative measure of macrofaunal bioirrigation for both single species and entire communities of various infaunal species, if the index is calculated with ash free dry body mass. IPc provided better estimations of phosphate, silicate, ammonium, nitrate and nitrite fluxes than BPc (Manuscript IV). The estimation of silicate, ammonium, nitrate, and nitrite fluxes may be further increased if IPcis calculated in wet body mass instead of ash free dry body mass. Wet body mass thereby serves as a proxy of the irrigated sediment volume. In general, IPc could become a valuable tool to support ecosystem management and future investigations on the effects of anthropogenic activities on biogeochemical turnover in shallow shelf seas. Findings of Manuscript IV however also demonstrated that IPc is a crucial but insufficient parameter for the modelling of sediment biogeochemical processes because these also dependent on environmental conditions (e.g. temperature, sediment organic matter content, permeability). A newly proposed temperature term (IcT) (Manuscript III) may provide a tool to identify spatiotemporal variations in macrofaunal bioirrigation activity. There is however a need to determine further how IPcor IcT relate to biogeochemical cycling under different environmental conditions as well as how the respective macrofaunal traits are affected by environmental parameters.

Description: The contribution of sediments to nutrient cycling of the coastal North Sea is strongly controlled by the intensity of fluxes across the sediment water interface. Pore‐water advection is one major exchange mechanism that is well described by models, as it is determined by physical parameters. In contrast, biotransport (i.e., bioirrigation, bioturbation) as the other major transport mechanism is much more complex. Observational data reflecting biotransport, from the German Bight for example, is scarce. We sampled the major sediment provinces of the German Bight repeatedly over the years from 2013 to 2019. By employing ex situ whole core incubations, we established the seasonal and spatial variability of macrofauna‐sustained benthic fluxes of oxygen and nutrients. A multivariate, partial least squares analysis identified faunal activity, in specifically bioturbation and bioirrigation, alongside temperature, as the most important drivers of oxygen and nutrient fluxes. Their combined effect explained 63% of the observed variability in oxygen fluxes, and 36–48% of variability in nutrient fluxes. Additional 10% of the observed variability of fluxes were explained by sediment type and the availability of plankton biomass. Based on our extrapolation by sediment provinces, we conclude that pore‐water advection and macrofaunal activity contributed equally to the total benthic oxygen uptake in the German Bight.

Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347

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: Loss of bioturbating key species from marine sediments has been shown to strongly reduce benthic biogeochemical cycling and ecosystemfunctioning. It is thus of paramount importance to identify key bioturbators and quantify their effect on biogeochemical processes. To do so trait based community and species bioturbation potential (BPc and BPi) was mapped for 423 North Sea stations in the German Bight. Mapping of BPc and BPi identified Amphiura filiformis, Echinocardium cordatum and Nucula nitidosa as major bioturbating species in the German Bight. The effects of these species on benthic nutrient flux (i.e., changing concentrations of silicate Δ[SiO2], ammonium Δ[NH4+], nitrate Δ[NO3−] and nitrite Δ[NO2−]) were quantified in laboratory experiments together with their bioturbation rate (Db) and bioirrigation activity. The experiments indicated that mapped species bioturbation potential (BPi) may be a poor tool for identifying key bioturbators while calculated experimental BPi (expBPi)was a good indicator for species impact on biogeochemical cycling. Out of the three investigated species only E. cordatum significantly influenced biogeochemical cycling, whereas the effect of A. filiformis remained inconclusive potentially because arm damage and regeneration may affect the bioturbation activity of many individuals. The bivalve N. nitidosa showed only little impact on biogeochemical cycling, although this species was found to be an active bioturbator. Accordingly, E. cordatum may be considered one of the most important contributors to biogeochemical cycling at the sediment-water interface in the German Bight.

Description: Data on marine biota exist in many formats and sources, such as published literature, data repositories, and unpublished material. Due to this heterogeneity, information is difficult to find, access and combine, severely impeding its reuse for further scientific analysis and its long-term availability for future generations. To address this challenge, we present CRITTERBASE, a publicly accessible data warehouse and interactive portal that currently hosts quality-controlled and taxonomically standardized presence/absence, abundance, and biomass data for 18,644 samples and 3,664 benthic taxa (2,824 of which at species level). These samples were collected by grabs, underwater imaging or trawls in Arctic, North Sea and Antarctic regions between the years 1800 and 2014. Data were collated from literature, unpublished data, own research and online repositories. All metadata and links to primary sources are included. We envision CRITTERBASE becoming a valuable and continuously expanding tool for a wide range of usages, such as studies of spatio-temporal biodiversity patterns, impacts and risks of climate change or the evidence-based design of marine protection policies.

Description: Low-frequency noise (LFN), or sound waves with frequencies between 10 Hz to 500 Hz, has increased substantially in coastal and shelf waters over the last decades. This is in large part due to the escalation in human activities such as shipping, wind farming, and pile-driving. Concern over how LFN affects marine mammal and fish welfare (eg. foraging efficiency, acoustic communication interference) has led the European Marine Strategy Framework Direction to include noise as a descriptor for achieving “good” environmental status. While the effects of anthropogenic noise on marine mammals and fish are by no means well documented, the effects of such noise on marine benthic invertebrates, crucial ecosystem engineers that continually rework sediment, are even less understood. Here, we present how LFN affects the behavior and sediment reworking activities of select macrobenthic invertebrate species from the North Atlantic in controlled laboratory setups. The polychaete Lanice conchilega, an abundant benthic invertebrate, exhibited behavioral responses to LFN in the form of modified pumping behavior. The amphipod crustacean Corophium volutator was negatively affected by LFN, exhibiting lower bioturbation rates and shallower burial depths compared to controls. The effect of LFN on the polychaete Arenicola marina and the bivalve Limecola balthica remained inconclusive, though A. marina displayed greater variability in bioirrigation rates when exposed to LFN. Benthic macroinvertebrates may be in jeopardy alone with the crucial ecosystem-maintaining services they provide, thus more research is urgently needed to understand, predict, and manage the impacts of anthropogenic noise pollution on marine fauna and their associated ecosystems.

Description: In times of rapidly increasing multiple anthropogenic impacts on polar marine ecosystems and biodiversity, understanding, sustainable-use management and protection of these biotas is a matter of great concern. Research on marine biotas and their interactions with each other and the environment is fundamental in that regard, but available data are still diverse and scattered, as they exist in many formats and sources, such as published literature, data repositories, and unpublished material. Due to this heterogeneity, information is difficult to find, access and combine, severely impeding its reuse for further scientific analysis and its long-term availability for future generations. Scientists, decision makers, and the public require a versatile tool to compile, synthesize and manage biodiversity data in a transparent, efficient and comprehensible way and with high-level quality assurance. To address this challenge, we developed, implemented and utilize CRITTERBASE (https://critterbase.awi.de), a publicly accessible data warehouse and interactive portal that complies with the FAIR principles (Findability, Accessibility, Interoperability and Reusability of data). Its purpose is to complement long-term data storage repositories by providing powerful but easy-to-use data ingest, retrieval and exploration tools, thus facilitating the analysis of biodiversity data across multiple spatial and temporal scales and in wider contexts. Currently, it hosts quality-controlled and taxonomically standardized presence/absence, abundance, and biomass data from Arctic, North Sea and Antarctic regions, collated from the literature, unpublished data, own research and online repositories (with all metadata and links to primary sources included), for 3,173 polar benthic taxa (2,444 of which at species level) from 12,209 samples collected with grabs, underwater imaging or trawls between 1800 and 2014. CRITTERBASE is currently holding benthic biodiversity data only but because of its comprehensive and flexible data model it is suited to include information about further biotas and habitats. Therefore, we envision it becoming a valuable and continuously expanding tool for a wide range of usages, such as studies of spatio-temporal biodiversity patterns, impacts and risks of climate change or the evidence-based design of marine protection policies.