Predictive value of trait-based measures for benthic secondary production in the German North Sea

Understanding the role of biodiversity for ecosystem functioning has become a central research theme in marine ecology. Benthic communities with a higher diversity have been suggested to operate more effectively, which could be quantifiable as a higher secondary production. However, there is no general ecological relationship between diversity and production, not only due to environmental influences, but also because of species-specific effects. Functional diversity has been identified as the key to understanding the link between biodiversity and ecosystem functioning. We are taking a trait-based and large-scale observational approach to relate patterns in macrofaunal secondary production to functional diversity in the southern North Sea, where benthic macrofauna is confronted with many natural and anthropogenic stressors. Functional diversity is expressed in indices based on dissimilarities of species traits such as feeding type, environmental position, and larval development. Production is calculated with taxon-specific empirical productivity models. Patterns of functional diversity were spatially more homogeneous than taxonomic diversity. A handful of species provided the majority of the secondary production. Spatially implicit regressions are used to analyze how secondary production is related to environmental factors and trait diversity. We explore further whether models are improved by including specific key traits potentially contributing to energy flow. Knowledge on the explanatory value of trait composition for maintaining productivity in our system is needed to explore scenarios of anticipated changes in diversity

Multiscale spatial distribution of macrofauna response to fishery pressure

Trawling is one of the most damaging activities for fauna living at the ocean resulting in simultaneous pulse and chronic impacts on benthic communities on multiple spatio-temporal scales. Recently, high quality Vessel Monitoring by Satellite (VMS) data provides spatio-temporal information of swept area by fishery trawlers. Using this huge amount of information in combination with about 20 environmental descriptors, we aim to tease apart the effect of species endogenous features (i.e. dispersal capability) and exogenous factors (i.e. environmental conditions) on the fauna responses to fishery and its related spatial scales. We analyse data of 300 grab-samples taken in the German Bight (North Sea), encompassing 140 macrobenthic species collected on a regular grid over an area of about 8000 km2. We use Moran Eigenvector Maps to model patterns of potential connectivity between locations and shed light on which spatial scales fisheries, environmental characteristics, and macrobenthos are linked. Finally, we show maps of fauna response to fishery. We argue that despite the importance of proper quantification of fishing pressure and other human activities, shedding light on the effects and response to such activities is crucial for a sound understanding of the processes that shape ecosystems and diversity distribution

Generalized changes of benthic communities after construction of wind farms in the southern North Sea

Over the last years, the development of offshore renewable energy installations such as offshore wind farms led to an increasing number of man-made structures in marine environments. Since 2009, benthic impact monitoring programs were carried out in wind farms installed in the southern North Sea. We collated and analyzed data sets from three major monitoring programs. Our analysis considered a total of 2849 sampling points converted to a set of biodiversity response metrics. We analyzed biodiversity changes related to the implementation of offshore wind farms and generalized the correlation of these changes with spatial and temporal patterns. Our results demonstrate that depth, season and distance to structure (soft-bottom community) consistently determined diversity indicators and abundance parameters, whereas the age and the country affiliation were significantly related to some but not all indices. The water depth was the most important structuring factor for fouling communities while seasonal effects were driving most of the observed changes in soft-sediment communities. We demonstrate that a meta-analysis can provide an improved level of understanding of ecological patterns on largescale effects of anthropogenic structures on marine biodiversity, which were not visible in single monitoring studies. We believe that meta-analyses should become an indispensable tool for management of offshore wind farm effects in the future, particularly in the view of the foreseen development of offshore renewable energies. This might lead to a better picture and more comprehensive view on potential alterations. However, this requires a modern open-source data policy and data management, across institutions and across national borders

Characterization and differentiation of sublittoral sandbanks in the southeastern North Sea

Marine sublittoral sandbanks are essential offshore feeding grounds for larger crustaceans, fish and seabirds. In the southern North Sea, sandbanks are characterized by considerable natural sediment dynamics and are subject to chronic bottom trawling. However, except for the Dogger Bank, sandbanks in the southeastern North Sea have been only poorly investigated until now. We used an extensive, multi-annual dataset covering ongoing national monitoring programmes, environmental impact assessments, and basic research studies to analyse benthic communities on sublittoral sandbanks, evaluating their ecological value against the backdrop of similar seafloor habitats in this region. The analysis revealed complex spatial structuring of sandy seafloor habitats of the southeastern North Sea. Different infauna clusters were identified and could be specified by their composition of characteristic species. The sandbanks shared common structural features in their infauna community composition although they were not necessarily characterized by particularly high biodiversity compared to other sandy habitats. A close association of one of the main bioturbators in the southern North Sea, the sea urchin Echinocardium cordatum, with sandbanks was detected, which may promote the sediment-bound biogeochemical activity in this particular seafloor habitat. This would corroborate the status of sandbanks as sites of high ecological value calling for consideration in marine conservation

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

The concept of the marine ecological community has recently experienced renewed attention, mainly owing to a shift in conservation policies from targeting single and specific objec- tives (e.g. species) towards more integrated approaches. Despite the value of communities as dis- tinct entities, e.g. for conservation purposes, there is still an ongoing debate on the nature of spe- cies associations. They are seen either as communities, cohesive units of non-randomly associated and interacting members, or as assemblages, groups of species that are randomly associated. We investigated such dualism using fuzzy logic applied to a large dataset in the German Bight (south- eastern North Sea). Fuzzy logic provides the flexibility needed to describe complex patterns of natural systems. Assigning objects to more than one class, it enables the depiction of transitions, avoiding the rigid division into communities or assemblages. Therefore we identified areas with either structured or random species associations and mapped boundaries between communities or assemblages in this more natural way. We then 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, and PHORONIS. They were assessed by estimating overlap and compactness and supported by analysis of beta-diversity. Overall, 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 designs with little information or at small spatial scales

Benthic production and energy export from man-made structures to natural soft bottoms: repercussions for food provisioning services?

Over the last decade, the installation and operation of extensive offshore wind farms led to a substantial increase in artificial substrates in the North Sea. Man-made structures (MMS) such as wind turbines represent additional hard-substrate habitats in the areas of the North Sea that are predominantly characterized by soft sediments. Man-made structures, colonised by fouling populations, may have potential effects by additional biomass discharge from MMS on the benthic soft bottom systems. At the same time, many ecosystem goods and services of the North Sea such as long-term carbon storage and natural resources (e.g. for fish, birds, mammals and finally humans) are intimately linked to the benthic system. Benthic invertebrates form the major food source for many commercially exploited fish species and thus the production (i.e. species energy that is turned into biomass) of benthic communities is of direct relevance for the food provisioning ecosystem service. In this study, production was calculated based on species populations as a quantification of energy flow and trophic interactions. The obtained results may thus provide clear signals for status and possible responses of populations and entire ecosystems to the introduction of MMS. The analysis included different datasets from various monitoring programs of offshore wind farms (i.e. the production and biomass of fouling communities and of natural soft-bottom community) from the Southern North Sea over several years. We analysed production changes due to environmental parameters and the presence of the structures in a meta-analysis. The analysis revealed clear modifications in the upper parts of MMSs, where the highest production values and potential biomass export to soft bottoms were detected. The outcome may thus represent a first step to disentangle the potential effects of additional biomass discharge from MMS on the ecological functioning of benthic systems. Future monitoring should therefore focus on specific targeted monitoring, i.e. investigate the cause-effect relationships to understand changes in energy flow and how this might affect (positive-neutral-negative) the food provisioning in marine ecosystems

CRITTERBASE, a science-driven data warehouse for marine biota

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