Schleswig-Holstein Wadden Sea Research Articles

Mapping seagrass (Zostera) by remote sensing in the Schleswig-Holstein Wadden Sea

The change of mapping methods for seagrass beds, here species of eelgrasses, from aerial surveys to automated classification of optical satellite data is described. Both methods are compared with respect to availability and suitability of their data. Differences in the detection capability of the methods are shown as well as results of the validation of the satellite image classification.In North Friesia, where the largest area of eelgrass occurs in the Wadden Sea, eelgrass beds have been mapped regularly using aerial surveys since 1994. After a significant decline in the 1930s and 1960s, monitoring results show a steady increase in the size of the area covered by eelgrass beds up to 2017.Since 2006, the aerial surveys have been complemented by ground surveys, which, however, only cover one sixth of the area of the Schleswig-Holstein Wadden Sea each year. Results show that size estimates of individual beds can vary significantly between aerial and ground surveys.In recent years, satellite-borne remote sensing technology and subsequent analysis methods have reached a level of quality, which makes them an alternative and cost-efficient method for mapping eelgrass. The technology has advantages such as the coverage of large areas at single points in time, repeatable and transferable image analysis methods, and high spatial resolution of the satellite images, as well as frequent repetition of acquisition of data. This provides standardised results, which allow direct comparisons over time and between areas.

Landscape Imaginaries and the Protection of Dynamic Nature at the Wadden Sea

Whereas the transgression of nature-culture dichotomies is commonplace in academic discourse, contemporary practices of nature conservation continue, in many cases, to be characterised by the active construction of fixed boundaries between spaces of nature and spaces of culture. In such contexts, nature constitutes a powerful discursive category, albeit one that is manifested differently across space and time. This paper advances a situated understanding of the spatialities and temporalities underlying contemporary practices of nature conservation through an empirical study of the concepts of nature and landscape informing management practices in the case of the Schleswig-Holstein Wadden Sea National Park in northern Germany. Theoretically, the paper draws on and further develops the concept of landscape imaginaries as a means to analytically make sense of diverse situated understandings of landscape and nature-culture relations. The paper thus addresses the implications of essentialist concepts of nature and landscape for protected area management within the context of a rapidly changing world. It is found that in this case, a conservation philosophy focused on the protection of natural processes is constrained by the maintenance of a categorical distinction between natural and cultural landscapes. The paper concludes with a plea for an understanding of nature conservation in terms of place-based situated practices.

On the feasibility of managed retreat in the Wadden Sea of Schleswig-Holstein

Sea embankments along the mainland coastline in the Schleswig-Holstein Wadden Sea safeguard 130,000 people and 19 billion € of capital assets from flooding during storm surges. Due to climate change induced sea-level rise, these defences will become exposed to higher storm surges and adaptation becomes inevitable. As an alternative to strengthening, managed retreat is discussed in literature as a coastal risk management option for climate change adaptation. Based on an evaluation of examples from the Wadden Sea, this paper elaborates managed retreat as alternative climate change adaptation from a coastal risk management perspective. This paper concludes that, conform the principles of integrated coastal zone management, one precondition for successful implementation of managed retreat is local acceptance. With respect to natural resilience to sea-level rise, managed retreat may counteract the loss of Wadden Sea structures and habitats due to coastal squeeze. However, the effectiveness depends on the surface elevation in the opened polder. If large volumes of sediment are needed to restore a natural elevation, regional resilience against SLR-induced drowning may deteriorate. With respect to coastal flood risk management in Schleswig-Holstein, opened polders have no significance as flood retention rooms and managed retreat does not reduce the hazard of flooding in surrounding polders. Further, removal of primary embankments requires large efforts to secure flood safety in adjacent polders. Under certain conditions, removal or opening of embankments may constitute sustainable coastal risk management, e.g., if retreat leads to a shorter line of defence or if other win-win-situations like securing of NATURA 2000 coherence arise.

Long-term change in habitat and vegetation in an ungrazed, estuarine salt marsh: Man-made foreland compared to young marsh development

Clay-rich salt marshes of mesotidal Wadden Sea coasts and of estuaries have been established mainly within artificial sedimentation fields in front of embankments. Natural salt marsh formation and natural range expansion outside artificial structures were rare. In the last three decades of this century natural marshes along the southern Wadden Sea coast of Schleswig-Holstein, Germany, started to grow outside groyne fields and extended on tidal mudflats. This growth happened without direct human influence and naturally structured marshes of considerable spatial dimension evolved.Due to a spread in recent decades, natural grown marshes in our study area – southern Schleswig-Holstein Wadden Sea coast - are younger than man-made marshes. Vegetation developed rapidly in response to fine-scaled geomorphological conditions. Meandering creeks and different surface elevation ranges of the developing natural salt marsh are special features. The naturally grown marshes show a high proportion of pioneer vegetation with Spartina anglica and Salicornia europaea. Succession proceeds fast and elevated parts of the marsh were rapidly colonised with marsh vegetation of Puccinellia maritima and Aster tripolium in the lower marsh to late successional stages, like Halimione portulacoides and Elymus athericus, on the higher elevated parts. Strikingly, median elevations of the vegetation zones in the natural marsh were several centimetres lower than those of the man-made marsh. The largest difference between both marsh types was the characteristic and the extent of drainage systems. Naturally grown marshes have a natural developed, fine-branched and four times shorter drainage system than man-made marshes with a dense drainage structure.

Numerical Modeling of Shoreface Nourishments in the Schleswig-Holstein Wadden Sea

Numerical Modeling of Shoreface Nourishments in the Schleswig-Holstein Wadden Sea

TMAP Wadden Sea Vegetation Database

Vegetation changes in the salt marshes of the Schleswig-Holstein Wadden Sea National Park are measured annually since 1991 in relation to sea level rise, vegetation changes and salt marsh management. In total 249 permanent plots were established along transects with a concentration to three different locations along the coast, namely the Hamburger Hallig, the salt marshes of Westerhever and on the island of Trischen. Annually the vegetation composition and the cover of the species is measured using the LONDO scale. The measurements are part of the Trilateral Monitoring and Assesment Programm (TMAP) within the trilateral Wadden Sea Cooperation. The data provide a baseline for further studies of salt marsh succession in relation to marsh management and coastal protection activities. This report describes the available content in the TMAP Wadden Sea Vegetation Database (GIVD ID EUDE-033).

TMAP Wadden Sea Sedimentation Database

Elevation changes in the salt marshes of the Schleswig-Holstein Wadden Sea National Park are measured annually since 1992 in relation to sea level rise, vegetation changes and salt marsh management by means of sedimentation-erosion-bar (SEB) measurements. In total, 144 permanent plots were established along transects with a concentration to three different locations along the coast, namely the Hamburger Hallig, the salt marshes of Westerhever and on the island of Trischen. The measurements are part of the Trilateral Monitoring and Assesment Programm (TMAP) within the trilateral Wadden Sea Cooperation. The data provide a baseline for further studies of vegetation changes in salt marshes and in relation to management and coastal protection activities. This report describes the available content in the TMAP Wadden Sea Sedimentation Database (GIVD ID EU-DE-032).

Twenty years of elemental analysis of marine biota within the German Environmental Specimen Bank--a thorough look at the data.

As one component of the German ecological environment observation, the Environmental Specimen Bank program was initiated in the mid-1980s. Under the program, representative specimens of marine, fresh water, and terrestrial ecosystems are sampled regularly and archived under chemically stable conditions. An initial characterization of the samples provides data regarding the status quo of the respective ecosystems. The aim of the present publication is to give insight into these real-time monitoring data, which have been generated for the last 10 to 20 years. This is done exemplarily for the heavy metals cadmium (Cd), mercury (Hg), and lead (Pb) in marine specimens of the Baltic and the North Sea. Bladder wrack (Fucus vesiculosus), blue mussel (Mytilus edulis), eelpout (Zoarces viviparus), and eggs of herring gulls (Larus argentatus) were sampled at one location in the Baltic Sea and at two sites in the North Sea (Schleswig-Holstein Wadden Sea and Lower Saxony Wadden Sea). Annual samples were pooled, homogenized, and analyzed for a set of elements. Cd and Pb were quantified after freeze-drying and microwave digestion using inductively coupled plasma-mass spectrometry. Total Hg in freeze-dried samples was determined by atomic absorption spectrometry using a direct mercury analyzer. Time series data covering up to two decades revealed comparable cadmium levels at all three locations. Concentrations in bladder wrack ranged between 0.10 and 0.37 microg/g on a wet weight basis (ww). Respective values for blue mussel and eelpout liver were 0.07-0.29 and 0.01-0.10 microg/g ww. Herring gull eggs were not included in cadmium analyses. Declining trends were observed in North Sea bladder wrack and mussels, eelpout from the Lower Saxony site, and mussels from the Baltic Sea. Upward trends were apparent in eelpout from the Schleswig-Holstein location. Mercury concentrations in Baltic Sea specimens ranged from 1.1-2.7 ng/g ww in bladder wrack to 2.6-5.1, 26-52, and 86-226 ng/g ww in blue mussel, eelpout muscle, and herring gull eggs, respectively. No temporal trends were observed. North Sea bladder wrack had accumulated 5.4-24 ng/g ww Hg. The respective Hg values for blue mussel and eelpout muscle were 19-64 and 73-187 ng/g ww. Highest Hg contents were detected in herring gull eggs (90-1,100 ng/g ww). Declining trends of Hg were observed in herring gull eggs at both North Sea locations and in blue mussels at the Lower Saxony site. Lead concentrations in Baltic Sea specimens were 48-222 ng/g ww in bladder wrack, 85-189 ng/g ww in blue mussel, 2.0-9.5 and 10-42 ng/g ww in eelpout muscle and liver, and 2.7-26 ng/g ww in herring gull eggs. In the North Sea, Pb concentrations were as follows: 68-397 ng/g ww in bladder wrack, 101-507 ng/g ww in blue mussels, 2.6-35 and 5.9-158 ng/g ww in eelpout muscle and liver, and 3.5-55 ng/g ww in herring gull eggs. Highest Pb-levels were found at the Lower Saxony site. Declining Pb-trends were observed in bladder wrack from the Baltic Sea; in bladder wrack and mussel at the Schleswig-Holstein location; and in bladder wrack, mussels, eelpout liver, and herring gull eggs at the Lower Saxony site. During the 10 to 20 years of monitoring, reliable data were obtained which allow a good insight into metal contamination of marine biota. Assessment of the data according to OSPAR criteria (OSPAR 2005) revealed cadmium levels above the derived background concentrations in mussels of all three sites. Mercury levels above background concentrations were found at both North Sea locations, whereas only mussels at the Lower Saxony site had Pb concentrations above the reference value. Archived specimens are available for further analyses and questions which may arise in the future (speciation of elements, metallomics).

On 4 June 2008 Siberian Red Knots at Elbe Mouth Kissed the Canonical Evening Migration Departure Rule Goodbye

Observations of departing Siberian-breeding Red Knots Calidris canutus canutus from their central staging site during northward migration, the Schleswig-Holstein Wadden Sea, Germany, in early June 2008, challenge the established notion that departing long-distance migrating waders only leave around sunset. During four days we scanned several thousand Red Knots for colour-ringed individuals and found a total of 20 different individuals that were previously ringed at either their main wintering site, the Banc d'Arguin in Mauritania, or at stopover sites on the Atlantic coast of France. Body masses of captured Red Knots in Schleswig-Holstein were higher than 200 g and hematocrite values showed an average of 58%, clearly indicating that they were ready for take-off. On all except one evening, we noted impressive departure movements during the incoming tide. On that exceptional evening a cold front thunderstorm passed over the area. Late the next morning, thousands of Red Knots departed during the incoming tide. We assume that the birds avoided taking off in adverse weather conditions and elaborate why Red Knots presumably traded off advantages from departing during twilight. We suggest that during spring migration, schedules are so tight that further delays decrease fitness, either because it would cause another full day of exposure to high predation risk by falcons, or because of conditions upon arrival on the tundra.

Integrated management of artificially created salt marshes in the Wadden Sea of Schleswig-Holstein, Germany

In the about 10,000 km2 large Wadden Sea 353 km2 of salt marshes exist. The great majority of these are artificial, i.e. developed through accretion enhancement techniques. Salt marshes in the Wadden Sea have a high coastal defence value as well as ecological significance. High salt marshes in front of sea walls reduce the wave-impact on the dikes and, therewith, the danger of breaching. At the same time, the salt marshes have a high ecological value, e.g., as resting places for migratory birds. In consequence, for coastal defence, salt marshes should be created and/or maintained. For nature protection, natural dynamic processes (incl. erosion) should prevail. To anticipate this possible conflict among coastal defence and environmental administration, in Schleswig-Holstein an interdepartmental working group established a salt marsh management concept. For information of the interested parties and for monitoring of the concept, an integrated salt marsh board was established, consisting of representatives from public administration and local interest groups (NGO's, dike and water boards, municipalities). Five years after implementation of the concept, this board established a first progress report. Although the concept was, in the beginning, met with great scepticism, five years of practical experience demonstrate that it functions well. The salt marshes are stable or growing, i.e. the management measures are successful. As a planning instrument, the concept is unambiguous, i.e. provides clear guidelines on how to manage the salt marshes. Finally, as an instrument of participation, the salt marsh board is valued positively by all members.

Aquaculture production and environmental regulations in Germany

Summary Aquaculture in Germany is a small industry, practiced only in a few specifically suited areas. Marine finfish farming is almost nonexistent but mussel farming is a steady activity with a notable level of production. However, this industry is presently very restricted with no hope for expansion as regulations are stringent and new licences in both fresh and marine waters are extremely difficult to obtain. In addition to State-specific conditions within the Federation, the complexity of the regulatory framework is exemplified by focusing on some key aspects for finfish farming and by specific aspects of mussel farming activities in the Schleswig-Holstein Wadden Sea where environmental protection measures dictate the level of control, mainly as a result of the recent establishment of the National Wadden Sea Park.

Comment on Buhs and Reise (1997): epibenthic fauna dredged from tidal channels in the Wadden Sea of Schleswig-Holstein: spatial patterns and a long-term decline

Comment on Buhs and Reise (1997): epibenthic fauna dredged from tidal channels in the Wadden Sea of Schleswig-Holstein: spatial patterns and a long-term decline

Draft management plan for the Wadden Sea of Schleswig-Holstein

Based on the results of the “Applied Ecosystem Research in the Wadden Sea of Schleswig-Holstein” a comprehensive concept of environmental protection has been prepared. The synthesis report (Stock et al. 1996) provides the foundation for a future National Park Plan. Examples of the conceptual part of the report are summarised in this contribution. The future border of the National Park should be orientated on ecosystem-criteria. Proposed large-scale zoning within the park can allow a self-organising nature and will secure a comprehensive protection of natural values and a sustainable use of natural resources. A visitor guidance concept offers the necessary information and will have a beneficial effect on public awareness of environmental problems. For the protection of the nurse- and rearing-grounds of small cetaceans a special protection area for whales is proposed.

Epibenthic fauna dredged from tidal channels in the Wadden Sea of Schleswig-Holstein: spatial patterns and a long-term decline

The epibenthic fauna dredged in the channels of the Wadden Sea of Schleswig-Holstein is dominated by crustaceans. Mean species richness is lower in a southern region (7.6±2.2 species haul−1) which is part of the Elbe estuary and lacks protective barrier islands. A northern region is more marine and is protected by a seaward barrier of high sands. Here mean species richness is 10.9±2.8. Within channels, there is no significant inshore-offshore gradient, and species number does not increase with depth. Stratified sampling near the island of Sylt revealed that abundance and diversity are high along the gentle upper slope (5 m depth) of channels when mussels are present, but low in the absence of mussels. Abundance and diversity are also low along the steeper slope below (at 10 and 15 m depth). In a channel with scattered stones and boulders, highest diversity (16.0±5.1) and dense epibenthic assemblages were encountered along the upper and middle slopes (5 and 10 m). Comparisons with historical surveys suggest that a decline of nearly fifty percent of all epifaunal species within the last hundred years may be attributed to fishery disturbances.

Seasonal variation in the occurrence of planktic bivalve larvae in the Schleswig-Holstein Wadden Sea

In the late 1980s, recruitment failures of the musselMytilus edulis led to economic problems in the mussel fishing and cultivation industries of northwestern Europe. As part of a collaborative study to gain a better understanding of the mechanisms affecting recruitment processes of mussels, plankton samples were collected regularly over a four-year period (1990–1993) from three stations in the Schleswig-Holstein Wadden Sea. The bivalve component of the plankton was dominated by the Solenidae, which was almost exclusively represented byEnsis americanus (= directus). M. edulis was the second most abundant species. Abundances of mussel larvae peaked 2 to 4 weeks after spawning maxima in the adult populations. Although variations in timing and amplitude of the total larval densities occurred, annual abundances ofM. edulis larvae remained stable during the study period, and regional abundance differences were insignificant. A close relationship was found between peaks in larval abundance and phytoplankton blooms. Differences in larval concentrations in the ebb and the flow currents were insignificant. Planktic mussel larvae measured between 200 μm and 300 μm, and successive cohorts were recognizable in the majority of samples. Most larvae were found to originate from local stocks, although imports from outside the area do occur.

Attachment and settlement of post-larval mussels ( Mytilus edulis L.) in the Schleswig-Holstein Wadden Sea

A number of spat collectors were designed and tested to monitor the spatfall of mussels ( Mytilus edulis) in the Schleswig-Holstein Wadden Sea. Initial trials using vertically suspended sisal ropes placed in the intertidal gave an indication of the importance of the orientation of the collectors to the direction of the tidal stream. Rotatable and cylindrical collectors, using a polyester petticoat gauze as a settlement substrate, were subsequently designed to function independently of the direction of the tidal current. The location and intensity of larval attachment to artificial collectors and naturally occurring filamentous substrates varied greatly. Settling intensity was closely correlated with the length of the current vector to which the collector was exposed and/or to its height in the water column. Two main settlement seasons were apparent: the first from late May to early August, and a second, shorter and with lower abundance, in late September into October. Settlement on the collectors and subtidal hydroids during winter provides field evidence for the ability of larvae to delay metamorphosis, and suggests their presence throughout the year. Length-frequency distributions of plantigrades from the collectors were comparable to those found attached to natural filamentous substrates over the same period. The substrate choices observed during this study confirm that plantigrades preferentially attach to filamentous substrates, and subsequently migrate onto pitted and creviced hard surfaces.

Attachment and settlement of post-larval mussels (Mytilus edulis L.) in the Schleswig-Holstein Wadden Sea

Attachment and settlement of post-larval mussels (Mytilus edulis L.) in the Schleswig-Holstein Wadden Sea

Large-scale distribution patterns of the mussel Mytilus edulis in the Wadden Sea of Schleswig-Holstein: Do storms structure the ecosystem?

The distribution of mussel beds in the Wadden Sea of Schleswig-Holstein was mapped by aerial surveys from 1989 to 1991. The number of mussel beds decreased from 94 in 1989 to 49 in 1990, as a result of severe storms in early 1990. Thereafter only small changes were observed. The mussel beds that remained in 1990 were found only in the shelter of islands; all beds in exposed areas had disappeared between the surveys of 1989 and 1990, leaving large areas without mussel beds. Storms are thus identified as a major factor limiting the distribution of mussel beds to the sheltered parts of the Wadden Sea. Beds in the exposed parts of the Wadden Sea are highly dynamic, whereas beds in sheltered areas may persist over long times. A comparison with distribution patterns of older surveys (from 1937, 1968 and 1978) revealed great similarities with the results of recent investigations, indicating a constant distribution pattern over a long period. The results are discussed in relation to eutrophication and the structure of the benthic communities of the Wadden Sea. It is concluded that any eutrophication-induced increase of the mussel population would be restricted to the sheltered parts of the Wadden Sea. Storms will largely determine whether the communities of a given area have to compete with mussels, which are most important filter feeders of the ecosystem. As competition for food is a major factor structuring the benthic communities of the Wadden Sea, it is assumed that storms indirectly affect all other communities, giving deeper-burying, storm-tolerant species a competitive advantage in exposed areas where epibenthic mussels are excluded. The impact of mussel fisheries will be different for persisting and dynamic beds: fishing on persisting beds in sheltered areas may remove the crucial reserve which mussel-feeding birds such as eiders or oystercatchers need in times of low mussel populations.

The impact of boating on the distribution of seals and moulting ducks in the Wadden Sea of Schleswig-Holstein: M. Thiel, G. Nehls, S. Brager & J. Meissner, Netherlands Institute for Sea Research, Publication Series, 20, 1992, pp 221–233

The impact of boating on the distribution of seals and moulting ducks in the Wadden Sea of Schleswig-Holstein: M. Thiel, G. Nehls, S. Brager & J. Meissner, Netherlands Institute for Sea Research, Publication Series, 20, 1992, pp 221–233

Arctic Sounds on Temperate Shores: The Occurrence of Song and Ground Display in Knots Calidris canutus at Spring Staging Sites

In May 1990, more than 4500 km away from, and up to three weeks before arriving on their high Arctic breeding grounds, individuals of two subspecies of Knots, Calidris canutus islandica and canutus, showed ground display and song whilst foraging in flocks on the tidal flats in the Wadden Sea of Schleswig-Holstein, FRG. Similar displays and songs were recorded in May 1987 and 1988 on the staging areas of C.c. islandica in northwest Iceland. The display behaviour, identified as the 'tail-up display', is probably performed only by males towards females, and occurs commonly just after arrival at the tundra breeding sites. Tail-up displays may result in copulations both on the staging and on the breeding sites. On the staging sites, tail-up displays were most frequent in the days prior to the departure of flocks to a subsequent stopover area (Iceland) or for presumed direct flights to the Canadian and the Siberian Arctic. Our observations suggest that the behavioural condition required for reproduction may, at least in males, develop some weeks before the actual arrival in the breeding areas.