Effects of global warming on arctic coastal communities



Worldwide, global warming causes effects on coastal ecosystems. In this regard, arctic shores are particularly affected because temperature in polar regions is rising twice as fast compared to the rest of the world. Therefore, we investigate the consequences of increasing water temperatures on arctic coastal diversity, species interactions, parasitism and ecosystem functioning. As an example, we study direct and indirect effects of a warming induced increase of macroalgae biomass at artic coasts of Svalbard. Here, an increasing number of algae are getting detached by storms due to the missing protecting sea ice cover in winter. Macroalgae accumulate on the seafloor, where they affect the existing benthic community.

Coping with climate change via epigenetics

This project is about the role of non-genetic/epigenetic inheritance in adaptive potential of species under climate change. A main focus is transgenerational plasticity (TGP: where parents prime offspring to perform better in matching future environments) that can be generated by epigenetic mechanisms such as DNA methylation, and provides a temporal buffer for genetic adaptation of populations facing rapid climate change. Ultimately, adaptive potential will determine population persistence and species extinction risk in a warming world, but may also play a key role in feedbacks between ecology and evolution (eco-evolutionary dynamics or EED). We use populations of marine threespine stickleback (Gasterosteus aculeatus) to identify epigenetic signatures potentially underlying TGP seen at the phenotypic level (physiology and growth) in response to ocean warming, and to disentangle contributions of genetic and epigenetic change to adaptive potential along latitudinal gradients (e.g. from the North Sea to the Arctic). Also, by exploring the role of TGP in EED we investigate whether epigenetic “pre-programming” via inherited adaptive methylomes can modify species interactions, community dynamics and ecosystem function, adding an evolutionary perspective to ecosystem models.


Ecological surveys of intertidal seagrass beds

Seagrass beds are highly productive coastal habitats and of great ecological importance. On the other hand they are also very sensitive towards a variety of parameters, particularly to human induced eutrophication. Therefore, seagrass is regarded as an indicator for ecosystem health and is used as such in the EU Water Framework Directive.

Seagrass beds in the Schleswig-Holstein Wadden Sea grow on the tidal flats and the survey of their status is applied by a combination of different approaches. An area-wide and large scale survey of the seagrass beds is conducted by an aerial mapping from a plane. Field surveys take place in chosen areas in order to complete the aerial mapping results by precise and high-resolution data. The analysis of historic aerial photographs allows a view on the past seagrass situation and enables to reconstruct their long-term development.

As the seagrass beds in the northern part of the Schleswig-Holstein Wadden Sea have increased significantly in bed area since the mid 1990s, a recovery is not observed for the beds in the southern part. We assume that seagrass in the northern part benefits from a recent reduction of nutrient discharges from large rivers while the southern beds are in too close proximity to the estuaries of Elbe, Weser and Ems. Additionally, as seagrass grows only at sheltered sites, stronger hydrodynamics as an effect of climate change are becoming an increasing threat.

Neobiota in German coastal waters

Non-native species have altered coasts and ecosystems worldwide since centuries. Today global trade of aquaculture organisms or fast ocean passages of cargo vessels accelerate the dispersal of non-indigenous species, increasing their numbers in local communities. According to the ‘European Marine Strategy Framework Directive’ nations are obliged to monitor the presence and distribution of marine neobiota in order to uncover pathways and prevent future introductions.

A specific neobiota monitoring program was initiated by the AWI and state authorities in 2009. The survey of defined harbor sites along the North and Baltic Sea shore resulted in a continuous time series, uncovering 1–2 newly introduced species on average per year.

Additionally, a synopsis on macrobenthic algae and invertebrates, summarizing relevant literature on aquatic non-native species in German coastal waters, was first published in 2015 and is currently updated. Short résumés and significant pictures are supposed to facilitate the identification of non-native species in ecological investigations as well as nature conservancy or student projects.  

HI-CAM: Helmholtz-Initiative Climate Adaptation and Mitigation: two Sides of the same Coin

The project aims to combine expertise from different research fields within the HGF, in order to give recommendations on climate adaption and mitigation for decision-makers in politics and research. For this purpose, AWI’s Wadden Sea Station will elucidate the carbon sequestration potential in marine vegetated habitats in the Wadden Sea, and explore the potential for development of restoration programs as a mean to enhance CO2 uptake.

In marine systems, salt marshes and seagrasses play a prominent role in carbon sequestration. However, due to large spatial heterogeneity in stored carbon and a limited number of studies, the sequestration capacity of these habitats along the German coast is largely unknown and subject to very high error-margins. In the HI-CAM Project, AWI-Sylt will quantify the carbon sequestration capacity of seagrass beds and salt marshes in the Wadden sea, and perform a quantitative spatial analysis in order to elucidate the C-sequestration capacity in the entire region.

Subtidal mussel populations on former culture plots in the Sylt-Rømø Bight

The project aims to follow the development of subtidal areas that were formerly used as mussel culture plots in the Sylt-Rømø Bight. Special focus is what effect the termination of fishing in these areas has on the mussel population and whether there are positive effects on other macroinvertebrate species associated to biogenic reefs.

The blue mussel (Mytilus edulis) is an important component of the Wadden Sea ecosystem. It facilitates benthic-pelagic coupling, influences sediment processes, provides structure to many other organisms, and thereby increases marine biodiversity. Besides its ecological importance, the mussel has also a high economic value and is one of the most important species for fisheries in the Wadden Sea. Aquaculture activities focus on the cultivation of seed mussels on bottom culture plots. The seed mussels are about 2–3 cm in shell length and are collected by fishing on subtidal wild mussel seed beds or originate from Seed Mussel Collectors. The mussel seed is relayed on the culture plots and cultured until a commercial size of about 4–5 cm is reached. During the culture process the plots are regularly fished to minimize epigrowth and reduce the abundance of a voracious predator, the common starfish.

In the Sylt-Rømø Bight, subtidal mussel culture plots once widely occurred throughout the entire area, but decreased considerably over the last decades. From 2017 onwards, the remaining culture plots were closed and all fishing activities on these plots were no longer allowed.

Since the areas used for mussel cultivation show a relative high mussel survival and growth, they may also serve as suitable areas for a natural development of subtidal mussel beds. As such, these areas may provide valuable information and may help to fill knowledge gaps on the ecology and macrobenthic community of undisturbed subtidal mussel beds.

Effects of two non-native crabs on native communities in the Wadden Sea

Worldwide, many coastal ecosystems are invaded by an increasing number of non-native species. They often affect native communities and especially predators like crabs cause strong effects on the occurrence and population dynamics of native species. In biotic habitats such as epibenthic bivalve reefs, interactions between associated species are comparatively close due to limited space. This is also the case In the Wadden Sea, where the two non-native crab species achieve highest densities in mixed reefs of native blue mussels and introduced Pacific oysters. However, effects on dynamics of potential prey species within this habitat are widely unknown. Therefore, we conduct manipulative laboratory and field experiments to assess the ecological role of both new crab species in bivalve aggregations, which represent one of the most diverse habitats in the Wadden Sea ecosystem.

Long-term performance of the small-sized fauna

This project aims to quantify the spatial and long-term temporal variability in meiobenthic communities in order to estimate their susceptibility to climate change

Small (mm-sized) animals are extremely abundant in the seafloor all over the world and may play an important role in benthic ecosystem performance. However, the small size leads to large problems in finding, retrieving, and handling of these organisms while their bewildering diversity asks for detailed taxonomic expertise. Therefore, the small benthic fauna has never been studied over most of the world. But the island of Sylt makes an exception; here, we have rich data on many aspects of meiofaunal community composition from the 1960s to 1980s. These unique historic data are used to reveal the degree of change in meiobenthic communities over the past decades and to identify the most important factors responsible for change.

The role of warming in spring diatom bloom timing (Sylt Rømø Bight, North Sea)

Due to the long-term ecological research activities (LTER) the Sylt Rømø Bight (SRB) is an ideal model system for the observation of warming effects on coastal ecosystems. Over the last 50 years the temperature of the sea surface (SST) rose by approximately 1.55 oC. This warming has been companied by a trend of less cold winters. Warm or rather cold winters have a tremendous impact on the spring diatom bloom in the bight. Following cold winters the bloom developed at lower temperatures (av. 2,4 oC ) compared with warmer ones (7,3oC ). After cold winters the spring bloom peaked almost one month earlier (March 17th) compared to warmer ones (April 12th) and spring bloom biomass was almost double as high after cold winters. Overall filtration rates (% average volume SRB per tidal cycle) of the benthic filter feeders during warm winters were in the range of 9-28 % while during cold winters only ≤ 4% were filtered. The resulting impact on the phytoplankton appears to be sufficiently high enough to suppress positive net production. Hence there are strong indications that the delayed, low biomass spring bloom in the wake of warm winters is caused by an enhanced top-down control triggered by the dense populations of benthic filter feeders

Application of Machine Learning algorithms for Chlorophyll-a prediction in the German Bight

Prediction of environmental data is a challenge as its details are more complex in nature, due to its complexity and nonlinearity, limitating conventional approaches on predicting unobserved near future. The versatility of Machine Learning techniques allow it to be successfully applied in many fields of science and to a great variety of problems.

Climate change is a global issue as it influences the marine environment and it impacts directly   human and marine species. Considering the importance in understanding the dynamics of primary production under global warming influence, the objective of this work is to evaluate the use of machine learning algorithms to the estimation of Chlorophyll-a concentration in the German Bight, (1) assessing Machine Learning algorithms like Random Forest, Neural Networks and Support Vector Regressor related prediction accuracy; (2) analyzing the temporal behavior of chlorophyll-a based on selected machine learning models and (3) examining the relative importance of temperature as a predictor in the different models

FESOM-C: Seamless modeling across scales: from global ocean to ocean shelf

Shelf areas represent a critical transition zone between the terrestrial area and the deep ocean. Although the shelf seas represent a small fraction of the Global Ocean, their role in the global biogeochemical cycle, climate- and  eco- systems is unproportionally large. These marine areas attract particulate attention due to high human activity there and its vulnerability to natural hazards. Note also, that many of the largest shelf seas are in polar regions, which are very sensitive to the climate change. The coastal zones and deep ocean evolve in time as one entity. However there is still substantial gap in understanding of the deep signal fate in the coastal areas and the role and feedbacks of the shelf processes with the wider system. In this sense numerical simulations are a powerful instrument. Making progress on this largely depends on the accurate representation of the physical environment in a coupled coastal-open ocean system. In its turn an accurate model representation of the physical processes is a pre-request for plausible simulation of the biogeochemical cycles and ecosystem dynamics. However, the elaboration of the coupled system still represents a great scientific challenge.

To fill mention gap we are building a coastal branch of the finite volume version of the global sea ice-ocean model FESOM (FESOM 2) - FESOM-C exploiting multi-resolution unstructured meshes. FESOM-C is designed from ground up for smaller scales and higher grid resolutions than FESOM and accounts for processes which are usually not resolved by large-scale models.

Exclusion of bottom touching fishing gear in marine protected areas within the German EEZ of the North Sea – Baseline description of sediment structures, bentho-pelagic habitats and biocenosis (MGF-Nordsee)

The aim of the BMBF funded project MGF-Nordsee is a detailed description of the present status of the three Natura 2000 sites in the North Sea allowing to assess the effects of fisheries exclusion on the ecosystems on the long run.  The results will provide a comprehensive baseline description of the sediment characteristics, bentho-pelagic habitats and food webs in the Natura 2000 sites allowing to detect long-term changes due to fishery management.

The establishment of no-take areas and marine conservation sites is a relevant management strategy to encounter the challenges of decreasing fish stocks, the destruction of habitats and the decline in biodiversity.  In the German exclusive economic zone (EEZ) of the North Sea there are three conservation areas (Natura 2000 sites), the Sylter Outer Reef, the Borkum Reef Ground and the Dogger Bank. These areas are protected under comprehensive guidelines to preserve threatened species and habitats.

Commercial fisheries have been shown to affect tremendously sediment structures, benthic communities and fish fauna. Impacts of fisheries will be investigated within the project. MGF-Nordsee works in close cooperation with the Federal Agency for Nature Conservation and is embedded in the research mission “Protection and Sustainable Use of Marine Areas” of the Deutsche Allianz Meeresforschung.



Past ecological states of oyster beds in the North Sea

The European flat oyster (Ostrea edulis) has been a keystone species in the North Sea, but became functionally extinct in the early 20th century due to overfishing and disease. This project investigates the age and structure of sublittoral oyster beds (Ostrea edulis) in the open North Sea in order to better understand past ecological states and potential environmental stressors leading up to the regional collapse of an important sublittoral filter feeder. This has implications for benchmarking baseline conditions in restorative efforts of Ostrea habitats. PESO commenced in summer 2019 and uses an interdisciplinary approach combining geoscientific methods with expertise in restoration ecology. The project is funded by the AWI section “Coastal Ecology” and is conducted in close collaboration with RESTORE.