Working Group Ecosystem Analysis:

Food Webs in Coastal Waters

Working in the Wadden Sea Station Sylt since 1980, my wife and me made our PhD in biological oceanography 1984 on “primary production of intertidal flats in the Wadden Sea and field studies on secondary production and respiration of benthic communities of the Wadden Sea”, respectively, at the University of Kiel, Germany. We could continue our work as postdocs at the Biologische Anstalt Helgoland, working on the energy flow of intertidal mussel beds. In our working group we focused on exchange processes and benthic-pelagic processes between the mussel bed and the overlying water. We developed an in situ flume system that allows us to measure these processes on a larger scale than is normally done in the laboratory or in mesocosms. Within the later ongoing SWAP-project we applied this system also to other intertidal communities of the Wadden Sea such as mud flats, sand flats and especially seagrass beds. We shared our work in that Ragnhild is focusing on primary producers such as benthic micro- and macrophytes as well as phytoplankton, and Harald directed his research mainly on the consumer part of the system. We used the information from this research to develop a model of the food web of the Sylt – Rømø Bight by ecological network analysis that reflects the ecological status of this ecosystem during the mid nineties. We found from this holistic approach that we have some gaps in our knowledge especially at the upper part of the food web within the top predator group, such as fish, birds and seals as well as in special communities such as seagrass beds. The following research period were characterized by the implementation of an intensive research on seagrass communities, particularly the influence of currents and waves on the grazing food chain of these communities as well as on the role of fish in seagrass beds. This research led us to the investigation.


Role of tropical seagrass beds in the coastal carbon cycle of Indonesia


The project aims to describe the carbon flow through selected tropical seagrass beds and to show how dependent its function as carbon sink is in relation to the riverine input of dissolved and particulate carbon.

Thus three special foci will be investigated which require the measurements in the field, laboratory and field experiments as well as modelling techniques:


  1. C-Budget of seagrass beds (stable isotopes; biomass etc. production measurements of all components).
  2. CO2 - Impact on the metabolism and development of seagrass beds (laboratory and field experiments).
  3. Network analysis of the food web of tropical seagrass beds (modelling).

The project is carried out in Indonesia at the coasts of Sumatra, the Riau-islands and at the Spermonde – Archipelago (Southwest Sulawesi) in the Frame of the German- Indonesian Research Project (

) in close cooperation with Indonesian research institutes, such as Research and Development Center for Marine, Coastal and Small Islands (RDC MaCSI) of Hasanuddin University (UnHas) Makassar, University of Riau (UNRI), Pekanbaru and the the Agency for Marine & Fisheries Research of the Republic of Indonesia, Jakarta Indonesia (KKP).The German part of the project is funded by the BMBF.


Members of Staff: Dr. Harald Asmus, Dr. Ragnhild Asmus, Dr. Dominik Kneer

From sediment to top predator


The Wadden Sea area around the Islands Amrum, Föhr and the main land is one of the most diverse and productive coastal areas of Schleswig-Holstein. The islands are used by various bird species as breeding sites and the surrounding Wadden Sea is a fruitful food source.
The interdisciplinary project STopP deals with the topic how sediment characteristics and hydrodynamics influence the distribution of benthic organisms and the development of specific habitats which are used by foraging birds.
With ecological network analysis food webs are created based on the collected data. The food webs show the importance of the different habitats for birds and allow forecasting future scenarios in the area due to natural or anthropogenic impacts.

The STopP- Project is one of the five projects of coastal research programme (KüNO-Verbund) (link) that are funded bei BMBF in the frame of sustainable development (FONA). The main Cooperation partners are: der Landesbetrieb für Küstenschutz, Nationalpark und Meeresschutz Schleswig-Holstein - Nationalparkverwaltung (LKN-NPV), which is coordinatiing the project, the Christian- Albrechts-University Kiel, especially with the  FTZ – Büsum and  das Landesamt für Landwirtschaft, Umwelt und ländliche Räume Schleswig Holstein.

Members of Staff: Sabine Horn (PhD-Student), Dr. Harald Asmus, Dr. Ragnhild Asmus

The impact of biological invasions on the food web of the Wadden Sea


The analysis of coastal food webs in relation to biodiversity is one of the recent topics of our section. Especially the dramatic changes in species composition due to new species such as the pacific oyster or the invasion of lusitanian fish species have promoted the attention on this research field.

The food web of the Wadden Sea may presently show another face as compared to the situation about 10 years ago.

We plan to establish the food web of the Sylt-Rømø Bight as a reference model for the Northern German and Danish part of the Wadden Sea. We install a food web in two additional areas, the Jade Bay and the Balgzand area to cover the total area.

Our aim is to develop scenarios for the future, including the invasive species as well as other changes to get an idea how climate change may have an influence on coastal food webs.

We portrayed the trophic web of the Sylt-Rømø Bight based on the situation analysed during the large ecosystem project SWAP in the early 90-ies. This leads to one of the most detailed food web model in the world that gave us a holistic view on ecosystem level, how our system works and in which parts it is sensitive. We also started to analyse the different communities in the Bay separately and became an idea how important habitat diversity is for the functioning and the stability of the total system.


The project INFOWEB is one of both bilateral dutch- german Biorisk-projects (Consequences of biological invasions for nature conservation in the Wadden Sea coastal ecosystem) that is funded in the frame of the Wadden Akademi by the NWO and the BMBF. The main co-operation partners are the Royal Netherlands Institute for Sea Research, NIOZ, the University of Groningen and the research Institute Senckenberg am Meer and five further Dutch, Danish and German institutions, especially the FTZ-Büsum.

Members of staff: Camille de la Vega (Phd-student), Dr. Harald Asmus (project leader and co-ordinator), Dr. Ragnhild Asmus 




In summer 2013 a new experimental facility at the AWI Wadden Sea station was completed to simulate the influence of changing environmental conditions on benthic communities in the Wadden Sea. The facility consists of 12 mesocosms, each with 1800 l water volume and a light-permeable cover. Each mesocosm has a tide and current simulation to recreate conditions as natural as possible for the communities. Furthermore, it is possible to manipulate in each basin the temperature, carbon dioxide concentration and nutrients. A multiparameter probe is monitoring and recording continuously and automatically pH, salinity, oxygen content and temperature.

As part of the BIOACID II project, the first experiment was conducted in spring  2014:

April - July 2014: To examine the impact of global warming and ocean acidification, a community of bladderwrack (Fucus vesiculosus forma mytili), Pacific oyster (Crassostrea gigas), mussels (Mytilus edulis), periwinkle (Littorina littorea, Littorina mariae) and amphipods (Gammarus spp.) was incubated in the mesocosms for 11 weeks. The temperature and CO2 concentration were increased as for the year 2100 predicted.

July - September 2014: In addition to global warming and ocean acidification we will   simulate the influence of increased entry of nutrients into the sea.

Further planned experiments:

The mesocosms are are very well equipped for experimental studies of the relationship between biodiversity of benthic systems and their ecosystem functioning.

Member of Staff: Dr. Harald Asmus, Dr. Ragnhild Asmus, Andereas Pansch (PhD-Student), Petra Kadel (BTA)


Pansch, A., Winde, V., Asmus, R. and Asmus, H. (2016): Tidal benthic mesocosms simulating future climate change scenarios in the field of marine ecology, Limnology and Oceanography: Methods. doi: 10.1002/lom3.10086

Graiff, A., Al Jabani, B., Asmus, H., Asmus, R.,    Bartsch, I., Bohm, F.,    Boettcher, M.,    Eisenhauer, A.,    Gutow, L.,    Karsten, U., Kruse, I. , Matthiessen, B., Mensch, B.,    Pansch, A.,    Raddatz, S.,    Schmitz-Streit, R.,    Tauber, I.,    Wahl, M.,    Werner, F. and Winde, V. (2015): Effects of warming and acidification on a benthic community in the Baltic Sea - Kiel Benthocosms, European Journal of Phycology, 50, pp. 89-90.


Food Webs

Role of meiofauna in the functioning of soft-bottom coastal food webs

The general aim of this PhD thesis will be to determine how changes of food source properties affect fluxes of organic matter in soft bottom coastal habitats. We will compare two bays, Marennes-Oléron Bay at the west coast of France, dominated by mudflats, and the Sylt-Rømø Bight in northern Germany, dominated by sandflats. The biomass of food resources (i.e., benthic diatoms, detrital matter, and phytoplankton) and meiofauna and the trophic relationships between these food sources and the meiobenthic consumers will be studied for four different seasons within these two bays. The three different habitats that will be studied are; mudflats (dominated by epipelic microalgae), sandflats (dominated by epipsammic microalgae) and seagrass beds (characterized by a mixture of epipelic and epipsammic microalgae and high quantities of detrital organic matter). The functioning of the two ecosystems, both the Marennes-Oléron Bay and of the Sylt-Rømø Bight, has been studied frequently and as a result, food web models have already been built. However, these models are mostly based on the relationships between food resources and macrofauna. To improve the food web models and the knowledge about the role of meiofauna in soft-bottom ecosystems, the results obtained during this PhD will be included into these pre-existing models. This will eventually allow us to determine the gains or losses of ecosystem functions provided by meiofauna when sediment grain size is changing.


Members of Staff: Luuk van der Heijden (PhD-Student), Dr. Harald Asmus, Dr. Ragnhild Asmus

Senior Scientist:

Dr. Sabine Horn



PD Dr. Harald Asmus

Dr. Ragnhild Asmus



Dr. Dominik Kneer (Alumni)

Dr. Camille de la Vega (Alumni)



Andreas Pansch (MSc.) (Alumni)

Luuk van der Heijden (MSc.) (Alumni)


Technical Assistance:

Petra Kadel

Birgit Hussel