A central aspect of coastal biogeochemistry is to determine how nutrients, lithogenic and organic matter are distributed and transformed within coastal and estuarine environments. Analyses of the spatio-temporal changes of total suspended matter (TSM) concentration indicate strong and variable linkages between intertidal fringes and pelagic regions. In particular, knowledge about the organic fraction of TSM provides insight to how biogenic and lithogenic particulate matter are distributed in suspension. In our study we take advantage of a set of over 3000 in situ Loss on Ignition (LoI) data from the Southern North Sea that represent fractions of particulate organic matter (POM) relative to TSM (LoI = POM:TSM). We introduce a parameterization (POM-TSM model) that distinguishes between two POM fractions incorporated in TSM. One fraction is described in association with mineral particles. The other represents a seasonally varying fresh pool of POM. The performance of the POM-TSM model is tested against data derived from MERIS/ENVISAT-TSM products of the German Bight. Our analysis of remote sensing data exhibits specific qualitative features of TSM that can be attributed to distinct coastal zones. Most interestingly, a transition zone between the Wadden Sea and seasonally stratified regions of the Southern North Sea is identified where mineral associated POM appears in concentrations comparable to those of freshly produced POM. We will discuss how this transition is indicative for a zone of effective particle interaction and sedimentation.The dimension of this transition zone varies between seasons and with location. Our proposed POM-TSM model is generic and can be calibrated against in situ data of other coastal regions.

The state and development of coastal marine systems and an understanding of the interaction of organisms, sea floor, water column, and biochemical and physical processes can only be obtained by a combination of long-term monitoring and modelling approaches of different complexity. A need for the development and evaluation of monitoring strategies is driven by a framework of different European and German regulations. The research project WIMO (Scientific Monitoring Concepts for the German Bight) has developed concepts and methods that aim at a fundamental scientific understanding of marine systems and also meet monitoring requirements of European legislation and regulations like the EU Marine Strategy Framework Directive. In this final report examples of common descriptors of ecosystem state like seabed integrity, eutrophication, and biodiversity are discussed. It has been assessed to what extent established measuring procedures used to survey the characteristics of the sea floor, and newly developed technologies are eligible for governmental monitoring. The significance of integrative modelling for linking and visualising results of measurements and models is illustrated. It is shown how new concepts have been implemented into governmental monitoring in the form of web based data sheets. These insights enable continuous analyses and developments in the future.

A. Canion1,*, J. E. Kostka1,** , T. M. Gihring 1, M. Huettel1, J. E. E. van Beusekom2,*** , H. Gao3,**** , G. Lavik3, and M. M. M. Kuypers 3 1Earth, Ocean, and Atmos. Science Dept, Florida State University, Tallahassee, Florida, USA 2Alfred Wegener Institute for Polar and Marine Research, List, Germany 3Max Planck Institute for Marine Microbiology, Bremen, Germany * now at: St. Johns River Water Management District, Palatka, Florida, USA ** now at: Schools of Biology and Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, Georgia, USA *** now at: Institute of Coastal Research, Helmholtz Zentrum Geesthacht, Geesthacht, Germany **** now at: School of Ocean and Earth Sciences, Tonji University, Shanghai, China

Despite decades of research on the physiology and biochemistry of nitrate/nitrite-respiring microorganisms, little is known regarding their metabolic response to temperature, especially under in situ conditions. The temperature regulation of microbial communities that mediate anammox and denitrification was investigated in near shore permeable sediments at polar, temperate, and subtropical sites with annual mean temperatures ranging from −5 to 23 °C. Total N2 production rates were determined using the isotope pairing technique in intact core incubations under diffusive and simulated advection conditions and ranged from 2 to 359 μmol N m−2 d−1. For the majority of sites studied, N2 removal was 2–7 times more rapid under simulated advective flow conditions. Anammox comprised 6–14% of total N2 production at temperate and polar sites and was not detected at the subtropical site. Potential rates of denitrification and anammox were determined in anaerobic slurries in a temperature gradient block incubator across a temperature range of −1 °C to 42 °C. The highest optimum temperature (Topt) for denitrification was 36 °C and was observed in subtropical sediments, while the lowest Topt of 21 °C was observed at the polar site. Seasonal variation in the Topt was observed at the temperate site with values of 26 and 34 °C in winter and summer, respectively. The Topt values for anammox were 9 and 26 °C at the polar and temperate sites, respectively. The results demonstrate adaptation of denitrifying communities to in situ temperatures in permeable marine sediments across a wide range of temperatures, whereas marine anammox bacteria may be predominately psychrophilic to psychrotolerant. The adaptation of microbial communities to in situ temperatures suggests that the relationship between temperature and rates of N removal is highly dependent on community structure.

The seasonal cycle of reproduction in Temora longicornis was investigated in the Bornholm Basin, Baltic Sea, from March 2002 to May 2003. Variations in egg production of the population (EPR) and spawning females (sfEPR, similar to clutch size), proportion of spawning females (%FS), egg hatching success (HS), female prosome length (PL) and weight-specific egg production (spEPR) were compared with the seasonal variations in temperature, salinity, and food concentration and composition. Females reproduced year round with maxima of 9.8 to 12.3 eggs female(-1) d(-1) in spring and low to moderate egg production during the remaining seasons. PL was maximal during spring, and % FS, sfEPR and spEPR paralleled egg production. HS was low during winter and increased in spring. The statistical analyses showed that mean egg production correlated with both sfEPR and % FS. While % FS was significantly related to food concentration, sfEPR was dependent on both food availability and PL, which in turn was inversely related to temperature. Salinity had no effect on the seasonal variation in egg production because females maintained their vertical position in water with low seasonal amplitudes in salinity and temperature, presumably to avoid high energetic costs due to osmoregulation under fluctuating salinity. Nevertheless, the costs due to osmoregulation during development likely resulted in small female PL, and thus indirectly affected reproduction. Using empirical non-linear regression, 80% of the seasonal variation in egg production of T. longicornis was explained by female length and food concentration. However, despite the pronounced seasonal variation in egg production, the recruitment of nauplii was continuously high except throughout the productive season, indicating that a low reproductive success was offset by female abundance.

The seasonal variation in abundance, biomass and vertical distribution of nauplii and copepodites of Temora longicornis in the Bornholm Basin was studied from March 2002 to May 2003 to understand the overwintering, spring development and life cycle of this species in the Baltic Sea. The analysis of the life cycle by means of stage structure, copepodite length and stage duration revealed that T. longicornis produced 5 to 6 generations yr(-1). The species overwintered in low abundance as an active, slowly developing generation with adults appearing from February/March onwards. The onset of the spring bloom in April triggered reproduction and initiated the first spring generation (G(1)) with a strong rise in nauplii abundance. The stock biomass increased in May with the occurrence of the copepodites of G1 and remained high during the succeeding generations G(2) and G(3) until August. The stock was distributed in the upper, brackish 30 to 60 m of the water column. In summer, copepodite stages concentrated in the cool intermediate water during daytime and migrated to the surface at night. This seasonal submergence explains the persistence of T longicornis in the Bornholm Basin throughout the year because the average temperature experienced by the population was low (5 to 14 degrees C) compared with the unfavourable warm surface temperatures (>20 degrees C). The study further showed that the timing of the spring biomass increase of the species is associated with the maturation of the first generation and can vary considerably between years. A delay of similar to 1 mo was observed in 2003 when environmental conditions during the cohort development were unfavourable. We conclude that the spring development of T. longicornis is complex and depends not only on prevailing temperatures, but also on spring bloom timing and post-bloom food availability.

Temporal dynamics and vertical patterns in bacterial abundances and activities were studied in a shallow subtidal sand flat in the Sylt-Rømø Basin (North Frisian Wadden Sea, Germany). Extracellular enzymatic activities, bacterial carbon production and community respiration showed strong (factor of 4–5) temporal variations that were mostly related to seasonal temperature change and to changes in substrate availability. These temporal patterns in enzymatic activity were barely reflected in bacterial (200–400 mmol C m−2) and microphytobenthic biomass (800–1500 mmol C m−2) or the sedimentary carbohydrate inventory (1300–2900 mmol C m−2), suggesting that grazing controls the standing stocks of the microphytobenthic and bacterial assemblages. Despite their exposure to strong hydrodynamic forces such as tidal currents and wind-induced wave surge, the subtidal sandy sediments showed persistent vertical gradients in bacterial abundances, carbon production and extracellular enzymatic activities at all times. The vertical distribution of these parameters was tightly coupled to that of the microphytobenthos, dominated by diatoms. Despite the low organic carbon content typical for surge-exposed sandy sediments, high extracellular enzymatic activities and bacterial carbon production rates indicate a very active heterotrophic bacterial community, with a gross secondary productivity of 30–180 mmol C m−2, and a biomass turnover time of 2–18 days. Our data suggest that this high activity is supported by the rapid flux of carbohydrates from microphytobenthic primary productivity. Accordingly, the potential activities of enzymes hydrolyzing carbohydrates cover most of the total bacterial carbon demand during all seasons.

Large‐scale experimental exclusion of lugworms ( Arenicola marina ) from 400 m 2 intertidal fine sand revealed significant effects of their bioturbation and bioirrigation on sediment characteristics, benthic infauna composition, and the dominant mineralization and benthic‐pelagic exchange processes in the sediment. Absence of lugworms resulted in sediment clogging with organic‐rich fine particles, an eightfold decrease in sediment permeability, low oxygen penetration depths, and accumulation of reduced mineralization products in the pore water. The sand flat inhabited by lugworms had low fine‐particle and chlorophyll contents and low sulfide and nutrient concentrations in the pore water. The effects were not limited to the vicinity of lugworm burrows but extended throughout the entire sediment down to ~20‐cm depth. Sediments with the lugworm shared the characteristic of low‐organic, advection‐driven permeable sand rather than of muddy, diffusion‐dominated sediments in the absence of lugworms. Areal oxygen uptake rates depended strongly on hydrodynamic conditions: under calm conditions, sedimentary oxygen uptake was slightly higher at the exclusion site. Experimental flushing using controlled hydrodynamic conditions showed that oxygen uptake at the lugworm site would be higher during more dynamic conditions (e.g., storms) due to significantly deeper oxygen penetration permitted by higher sediment permeability. Our results indicate an interactive effect of bioturbating organisms and hydrodynamics on water‐sediment exchange processes and highlight the importance of benthic infauna for sedimentary processes even in physically dominated systems.

Sediment destabilization by sediment-reworking organisms is common in coastal aquatic environments, but the potential of bioturbation to inhibit shoreline succession has not been suggested previously. The lugworm Arenicola marina is a widespread and dominant large burrower at European Atlantic shores, and a major source of bioturbation and bioirrigation on the extensive intertidal flats in the Wadden Sea (eastern North Sea). The hypothesis that lugworm activities inhibit the successive development from sandy to muddy sediments in depositional embayments has been tested by a large-scale exclusion field experiment. Changes in sediment properties indicate a progressive clogging of interstices with fine particles and organic matter, resulting in lower sediment permeability in exclusion areas compared to lugworm inhabited control areas. Chlorophyll content in the surface layer was consistently higher in the absence of lugworms. Lack of sub-surface irrigation in the absence of lugworms combined with reduced sediment permeability resulted in increased concentrations of ammonium, phosphate, silicate, and sulphide in the pore-water. Concentrations >100μM of sulphide gave rise to toxic conditions for macrofauna. The effects of lugworms on sediment characteristics were more conspicuous in fine than in medium sand. It is concluded that A. marina contributes to the maintenance of permeable sand and thereby sustaining suitable conditions for the lugworm population itself. Without this “ecosystem engineer” mud flats would greatly expand at the expense of sand flats in the Wadden Sea.

Among the increasing number of species introduced to coastal regions by man, only a few are able to establish themselves and spread in their new environments. We will show that the Pacific oyster ( Crassostrea gigas ) took 17 years before a large population of several million oysters became established on natural mussel beds in the vicinity of an oyster farm near the island of Sylt (northern Wadden Sea, eastern North Sea). The first oyster, which had dispersed as a larva and settled on a mussel bed, was discovered 5 years after oyster farming had commenced. Data on abundance and size-frequency distribution of oysters on intertidal mussel beds around the island indicate that recruitment was patchy and occurred only in 6 out of 18 years. Significant proportions of these cohorts survived for at least 5 years. The population slowly expanded its range from intertidal to subtidal locations as well as from Sylt north- and southwards along the coastline. Abundances of more than 300 oysters m −2 on mussel beds were observed in 2003, only after two consecutive spatfalls in 2001 and 2002. Analyses of mean monthly water temperatures indicate that recruitment coincided with above-average temperatures in July and August when spawning and planktonic dispersal occurs. We conclude that the further invasion of C. gigas in the northern Wadden Sea will depend on high late-summer water temperatures.

Biogenic silica, one of the major constituents of marine sediments, is a potentially powerful paleoceanographic tool, revealing information on past productivity. Interpreting the sedimentary records of the biogenic silica requires, however, an understanding of its preservation. Dissolution of biogenic silica is controlled by the presence of trace elements such as Al. The work in this paper focuses on the association of Al and Si in biogenic silica. The composition and the atomic structure of cultured and natural diatoms were determined by using PIXE and XAS techniques. This study provides the first evidence for a structural association of Al and Si in biogenic silica.

We used X-ray absorption spectroscopy at the Al K-edge to investigate the atomic structure of biogenic silica and to assess the effect of Al on its crystal chemistry. Our study provides the first direct evidence for a structural association of Al and Si in biogenic silica. In samples of cultured diatoms, Al is present exclusively in fourfold coordination. The location and relative intensity of X-ray absorption near-edge structure (XANES) features suggests the structural insertion of tetrahedral Al inside the silica framework synthesized by the organism. In diatom samples collected in the marine environment, Al is present in mixed six- and fourfold coordination. The relative intensity of XANES structures indicates the coexistence of structural Al with a clay component, which most likely reflects sample contamination by adhering mineral particles. Extended X-ray absorption fine structure spectroscopy has been used to get Al-O distances in biogenic silica of cultured diatoms, confirming a tetrahedral coordination. Because of its effect on solubility and reaction kinetics of biogenic silica, the structural association between Al and biogenic silica at the stage of biosynthesis has consequences for the use of sedimentary biogenic silica as an indicator of past environmental conditions.

The Wadden Sea is a shallow tidal area along the North Sea coast of The Netherlands, Germany and Denmark. The area is strongly influenced by rivers, the most important of which are the rivers Rhine, Meuse and Elbe. Due to the increased nutrient load into the coastal zone the primary production in the Wadden Sea almost tripled during the past few decades. A conceptual model is presented that links nitrogen input (mainly nitrate) via Rhine and Meuse with the annual nitrogen cycle within the Wadden Sea. Three essential steps in the model are: (1) nitrogen limits the primary production in the coastal zone, (2) a proportional part of the primary produced organic matter is transported into the Wadden Sea and (3) the imported organic matter is remineralized within the Wadden Sea and supports the local productivity by nitrogen turn-over. The conceptual model predicts that during years with a high nutrient load more organic matter is produced in the coastal zone and more organic matter is transported into and remineralized within the Wadden Sea than during years with low nutrient loads. As a proxy for the remineralisation intensity ammonium plus nitrite concentrations in autumn were used. Based on monitoring data from the Dutch Wadden Sea (1977–1997) the above mentioned model was statistically tested. In autumn, however, a significant correlation was found between autumn values of ammonium and nitrite and river input of nitrogen during the previous winter, spring and summer. The analysis supports that in years with a high riverine nitrogen load more organic matter is remineralized within the Wadden Sea than in years with a low nitrogen load. A comparison with older data from 1960 to 1961 suggests that the remineralisation intensity in the Wadden Sea has increased by a factor of two to three. This is not reflected by a two to three-fold increase in riverine nitrogen load from 1960 to present. It is suggested that the increased remineralisation rates in the Dutch Wadden Sea between the 1960s and the 1980s/1990s are largely caused by an increased nitrogen flux through the Channel and the Strait of Dover and by an increased atmospheric nitrogen input.

Seven years after the 1991 Mount Pinatubo eruption, the current geochemical environment of ash-covered deep-sea sediments in the South China Sea was investigated. The depth distributions of O2, NO3−, Mn2+, Corg and porosity at six representative sites covered with varying thicknesses of tephra are reported. The shapes of the depth profiles reveal that O2 is totally exhausted within ash layers thicker than 3 cm, while thinner layers are penetrated by oxygen followed by linear downcore profiles with depletion between 8 and 12 cm. Hence, the zone between ash layer and total depletion of oxygen represents a zone of negligible oxygen consumption. Various multi-layer models were developed to explain the observed oxygen concentration profiles. These mathematical simulations also serve to assess both the development since the surface sediments were sealed by the ash fallout as well as the future evolution. Whereas thick tephra layers provoke a nearly stationary situation, i.e. are capable of preventing oxygen from penetrating into the underlying sediments, oxygenation of sediments below thin layers increases rapidly. In these sediments, the effect of oxygen diffusion velocity is drastically reduced by the reaction with dissolved manganese, and therefore explains the linear profiles. Besides, this study is suitable as a case study to assess the effects of human interventions in the deep-sea ecosystem, such as mining and waste dumping.

Summary From 1994 through 1996 transformation processes in the water column of the German Bight and the adjacent Wadden Sea were investigated in the projects TRANSWATT and KUSTOS. On the basis of a review of carbon and nutrient budgets we examine the role of processes in the sediment for overall carbon and nutrient cycling in the Wadden Sea and adjacent German Bight. We distinguish two aspects: the sediment as the site where organic matter is rapidly turned over and the sediment as the site where organic matter and nutrients are immobilized. The relative importance of the sediment for the remineralisation of organic matter depends on the water depth: The review of carbon budgets suggests that in the Wadden Sea (2 - 3 m) about 50% of the remineralisation occurs in the sediment. In the German Bight (20 m), 10 - 20% of the primary production is remineralised in the sediment. The budgets further show that the Wadden Sea is heterotrophic. About 100 gC m -2 y 1 is imported from the coastal zone. This implies a net autotrophy of the coastal zone, which is in line with the results from the projects TRANSWATT and KUSTOS. Within the Wadden Sea, organic matter has to be turned over two to three times and in the German Bight three to four times to explain the annual primary production. This is lower than in the offshore North Sea where annual turnover rates up to five have been found. Several processes remove nutrients on longer time-scales from the biogeochemical cycle. The importance of the local formation of phosphorus containing minerals like apatite as a phosphorus sink is shown. A discussion of several denitrification estimates concludes that in the German Bight and adjacent Wadden Sea on average about 8 -16% of the total nitrogen influx (from the coastal zone, from rivers and via the atmosphere) is lost to the atmosphere.

The external forcing of the German Bight system is largely due to the atmosphere. Energy fluxes that drive mixing processes and biological productivity, as well as atmospheric nutrient inputs outside the Elbe estuary, are important factors for biomass production. This study is based on the KUSTOS experiments focusing on air-sea exchange with intensive observations of a) radiative fluxes at the surface of the drifting water body; b) atmospheric surface layer parameters determining the mixing conditions in the planetary boundary layer; c) the speciation of atmospheric nitrogen compounds; d) and changes in aerosol and gas composition during transport over sea. These episodic data were complemented by a) synoptic data analysis of water and air temperature, wind, pressure and water vapour pressure over the sea; b) corresponding oceanic data on heat advection and mixed layer depth from an oceanic model driven by observations in the atmosphere; c) computations of the highly variable heat and radiative fluxes with the mesoscale atmospheric model METRAS; d) long-term atmospheric deposition measurements of nutrients in the German Bight; e) investigations of the atmospheric processes responsible for the formation of coarse particulate nitrate by means of a new aerosol submodel in the METRAS transport model. We present detailed seasonal or annual budgets for fluxes of heat, momentum, nitrate, ammonium, persistent organic pollutants. The atmospheric fluxes of heat and chemical matter are compared with load and fluxes in the water column in order to identify when and where the atmospheric impact is relevant and detectable. Spatial and temporal variability is discussed for the fluxes of heat, momentum and nitrogen. From the budgets we identify categories of potential atmospheric impact. Apart from the category “no atmospheric impact≓ valid e.g. for Cr, As, Ni and phosphate, we identify 4 others: 1) “atmosphere driven≓: short term, local dominant impact for Heat and momentum; 2) “episodic atmospheric impact≓: long term, local and dominant impact with large fluxes involved for radiation, PCB, Pb; 3) “persistent atmospheric pollutant≓: long term dominant but regionally indifferent impact for α- and γHCH; 4) “steadily perturbing the marine ecosystem≓: long term, widespread impact superimposed on the dynamic system driven by marine biology for nitrate, ammonium.