Bodden Chain Research Articles

Benthic diatom diversity in a turbid brackish lagoon of the Baltic Sea

ABSTRACT The Darß-Zingst Bodden Chain is a tide-less shallow lagoon at the Southern Baltic coast. It was and is studied in almost all hydrological, biogeochemical as well as floristic and faunistic aspects. Benthic diatoms were studied using light and scanning electron microscopy (SEM) in the early 1970s and one sampling site was now revisited. A total of 103 diatom taxa were recorded in sediment and on macrophyte samples collected between 2015 and 2019. In the sediment samples, epipsammic diatoms accounted for almost 90% of the total valve counts. In the 1970s, only three epipsammic species were observed, while we recorded a total of 27 epipsammic taxa, most of which were very small (<12 µm). Since those earlier studies, many of these species have been newly described or transferred from other genera. Moreover, small diatoms may have been misidentified, overlooked or counted as important. This study emphasizes, in addition, the need to combine light microscopy with electron microscopy to allow the unambiguous identification also of small entities, and to reach a comprehensive overview over the diatom flora present in different benthic habitats.

Phosphorus Contents Re-visited After 40 Years in Muddy and Sandy Sediments of a Temperate Lagoon System

Worldwide, coastal water bodies suffer from anthropogenically elevated nutrient inputs, which led to eutrophication. Sediments in eutrophic systems are assumed to be an important internal nutrient source. The total phosphorus (TP) concentration (mg g-1 dry mass) is widely used as a proxy for the sediment nutrient load. 2-D distribution maps of TP concentrations are used for management plans, where areas of high TP values are marked in red. However, the sediment density is lowered at increasing water content, which can lead to different TP stocks per g m-2. The aim of this study was, to do a re-evaluation of TP concentrations and stocks in the model ecosystem of the Dars-Zingst Bodden chain, a typical lagoon system of the southern Baltic Sea. Sediment cores were taken at eight stations along transects from shallow to deeper parts of the lagoon. Samples were analyzed for TP, water and organic content, as well as density. This data set was compared to results from a sediment survey during the time of highest nutrient inputs (40 years ago) at the same sampling stations. TP concentrations from 40 years ago and today were in the same range. The highest TP concentrations (up to 0.6 mg TP g-1 dry mass) were found in the deeper basins and lowest concentrations in the shallow areas of the lagoon (down to 0.05 mg TP g-1 dry mass). However, normalization over dry bulk density reversed some results. The highest TP stocks (up to 5 g TP m-2) were then found in the shallow areas and lowest stocks (down to 0.2 g TP m-2) in the deeper parts of the lagoon. Some stations did not exhibit any differences of TP at all, even after including the dry bulk density. These findings suggest that there seems to be no up-, or downward trend in nutrient concentrations of sediments even after 25 years of reduced external nutrient inputs. Furthermore, TP stocks point to possible diffuse P entry pathways that counteract external nutrient reductions. These findings can have an impact on possible countermeasures for ecosystems rehabilitation, like sediment removal or nutrient reductions in the adjacent land.

Assessing maximum depth distribution, vegetated area, and production of submerged macrophytes in shallow, turbid coastal lagoons of the southern Baltic Sea

Submerged macrophytes improve water quality in shallow coastal lagoons but eutrophication often resulted in a degradation of macrophytes. Management measures that protect and restore macrophyte stands require knowledge on what limits macrophyte distribution. Information on macrophyte production and distribution in the Darss-Zingst Bodden Chain (southern Baltic Sea) is lacking since an almost complete loss of submerged vegetation in the 1980s. Nutrient input was reduced in the 1990s and macrophytes seem to recover, although turbidity is high and light conditions are still poor. However, this recovery raised hope that returning macrophytes could stabilize sediments and improve water clarity. In this study, seasonal changes in photosynthesis–irradiance curves of selected macrophyte species were used to calculate potential primary production in different depths and turbidity situations. Bathymetry of the area is then used to assess depth distribution and vegetated area. Since the so-calculated depth limits correspond well with the actual depth distribution in the field, macrophyte depth distribution is concluded to be mostly determined by light conditions. Most macrophytes grow in very shallow areas up to 50 cm depth where also 70% of potential primary production takes place. Present light conditions do not support a further expansion of macrophyte distribution in the DZBC.

Dynamics of surface elevation and microtopography in different zones of a coastal Phragmites wetland

Surface elevation and microtopography of coastal wetlands are important attributes with respect to the adaptation to sea level change. While the total increase in elevation determines if a wetland can keep up with sea level rise, microtopography impacts, inter alia, hydrological patterns, which again drive surface elevation changes. We analyzed the dynamics of surface morphology during the course of one year at five locations along a transect from land (interior zone) to sea (fringe zone) in a coastal Phragmites wetland at the Darss-Zingst Bodden Chain (Southern Baltic Sea) using a modified Surface-Elevation Table. Landwards this wetland is confined by a dyke while the seaward boundary of the wetland is formed by a micro-cliff. A small strip between the interior and the fringe zone is characterized by small basins (basin zone). Surface elevation changes in the wetland interior are mainly driven by its own productivity. Litter accumulation by the dense Phragmites stands is high, but a combination of high organic sediments and water scarcity led to compaction and counteracted vertical accretion. While the surface elevations of the measurement location in the basin zone and one of the locations in the interior zone remained fairly stable (intra-annual changes<±0.8mm), the other location in the interior showed a drastic decrease in surface elevation (−3.3cmyear−1). This large deviation may have been caused by the high spatial variability of sediment organic matter. The micro-cliff eroded constantly (−3.7cmyear−1); its steepness and surface roughness increased making it more vulnerable to the forces of the sea. The micro-cliff protects the wetland interior from flooding but at the same time suppresses allogenic sediment input. The simple approach to use freely available water level data to predict morphological changes in the fringe zone did not yield significant model results. However, the strong intra-annual variability in elevation change especially in the fringe zone showed that short-term changes may often mask long-term trends. Although we cannot predict long-term developments from our relatively short-term measurements, our results indicate that wetland evolution in such squeezed environments is threatened. In dyked wetlands sediment supply from the land is suppressed and lateral erosion at the seaward edge leads to marsh retreat. None of the measuring locations is currently keeping up with local sea level rise.

Impact of adjacent land use on coastal wetland sediments

Coastal wetlands link terrestrial with marine ecosystems and are influenced from both land and sea. Therefore, they are ecotones with strong biogeochemical gradients. We analyzed sediment characteristics including macronutrients (C, N, P, K, Mg, Ca, S) and heavy metals (Mn, Fe, Cu, Zn, Al, Co, Cr, Ni) of two coastal wetlands dominated by Phragmites australis at the Darss-Zingst Bodden Chain, a lagoon system at the Southern Baltic Sea, to identify the impact of adjacent land use and to distinguish between influences from land or sea. In the wetland directly adjacent to cropland (study site Dabitz) heavy metal concentrations were significantly elevated. Fertilizer application led to heavy metal accumulation in the sediments of the adjacent wetland zones. In contrast, at the other study site (Michaelsdorf), where the hinterland has been used as pasture, heavy metal concentrations were low. While the amount of macronutrients was also influenced by vegetation characteristics (e.g. carbon) or water chemistry (e.g. sulfate), the accumulation of heavy metals is regarded as purely anthropogenic influence. A principal component analysis (PCA) based on the sediment data showed that the wetland fringes of the two study sites are not distinguishable, neither in their macronutrient status nor in their concentrations of heavy metals, whereas the interior zones exhibit large differences in terms of heavy metal concentrations. This suggests that seaside influences are minor compared to influences from land. Altogether, heavy metal concentrations were still below national precautionary and action values. However, if we regard the macronutrient and heavy metal concentrations in the wetland fringes as the natural background values, an accumulation of trace elements from agricultural production in the hinterland is apparent. Thus, coastal wetlands bordering croplands may function as effective pollutant buffers today, but the future development has to be monitored closely to avoid breakthroughs due to exceeded carrying capacities.

Phosphorus storage and mobilization in coastal Phragmites wetlands: Influence of local-scale hydrodynamics

Coastal Phragmites wetlands are at the interface between terrestrial and aquatic ecosystems and are important for nutrient retention and regulation. They can act both as nutrient sinks and sources for phosphorus, depending on environmental conditions, sediment properties as well as antecedent nutrient loadings and sorption capacities of the sediments. The Darss-Zingst Bodden Chain is a shallow lagoon system at the German Baltic coast with a long eutrophication history which is lined almost at its entire length by Phragmites wetlands. In order to elucidate under which conditions these wetlands act as sources or sinks for phosphorus, in-situ data of chemo-physical characteristics of water and sediment samples were combined with hydrodynamic measurements and laboratory experiments. A basin zone within the wetland serves as accumulation sink for fine-grained particles rich in phosphorus, iron, manganese and organic matter. The Phragmites stems reduce the water flow and allow the accumulation of organic matter and minerals. Without turbulent mixing and downward flow the bottom water and the sediment surface lack replenishment of oxygen. The relationship between oxygen saturation in the water and soluble reactive phosphorus (SRP) concentrations showed a threshold-type behavior. Under oxygen deficiency soluble reactive phosphorus concentrations in the water were significantly higher than under aerated conditions (oxygen saturation <10%: mean SRP = 0.22 mg/L vs. oxygen saturation >10%: mean SRP = 0.02 mg/L). During stagnant periods with low water level, low-turbulence and thus low-oxygen conditions phosphorus from the sediments is released. But the sediments are capable of becoming sinks again once oxygen is resupplied. When vertical downward flows are dominant in the water and turbulent kinetic energy rises, oxygen saturation increases. A thin oxic sediment surface layer rich in iron and manganese is able to readsorb phosphorus quickly as kinetic sorption experiments show, but due to its redox sensitivity the immobilization is – at least in part – only temporary. This study demonstrated that sediments in coastal Phragmites wetlands can switch their function from sink to source of soluble reactive phosphorus on a very short time-scale, depending on local-scale hydrodynamic conditions and the state of the oxic–anoxic sediment interface.

Long term water level and surface temperature changes in the lagoons of the southern and eastern Baltic

The paper studies variations in the water level and surface temperature of coastal lagoons along the southern and south-eastern shores of the Baltic Sea: the Curonian Lagoon, Vistula Lagoon, and Darss-Zingst Bodden Chain. Linear regressions for annual mean water level variations showed a positive trend in water level, but at different rates. The highest rate during the period between 1961–2008 was recorded for the Curonian and Vistula lagoons (~ 4mm year−1), the lowest for the DarssZingst Bodden Chain (approximately ~ 1mm year−1). The warming trend of the mean surface water temperature in the lagoons was 0.03°C year−1 in the period 1961–2008. Moreover, the variability in annual water temperature and sea level as well as their extreme values have increased most dramatically since the 1980s.

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Tideless estuaries are very common on the western, southern and eastern Baltic coast. They play an important role as buffers and filters for the Baltic Proper. These functions can vary, depending on discharge areas and the situation in the estuaries themselves. Our knowledge of the estuaries varies widely, ranging from more or less simple descriptions to a fairly complete understanding of the processes taking place in their ecosystems. So far, only one preliminary comprehensive study has been performed for the whole area (Baltic Sea Environment Proceedings No. 40, HELCOM 1991).Three different discharge areas connected to tideless estuaries are compared in some detail:-the shallow polytrophic Darss-Zingst Bodden Chain, Germany-the shallow eutrophic Puck Bay, Poland-the deeper mesotrophic Gulf of Riga, Latvia.Starting points are discharge areas, discriptions of the water bodies and main loads. The development of the ecosystems under the influence of anthropogenic impacts during the last 40 years is then described.Conclusions are drawn concerning:-the general behaviour of such systems-the benefits and drawbacks of the discharge areas, the loads, and the structures and functions of the estuaries-special problems regarding the buffer and filtering capacities of the systems in question-economic consequences.High variability and elasticity are the main characteristics of these tideless estuarine ecosystems. Multivalente economic utilization of these resources and functions is the best way to save such ecosystems and money as well.

Mixotrophy, allelopathy and the population dynamics of phagotrophic algae (cryptophytes) in the Darss Zingst Bodden estuary, southern Baltic

Seasonal plankton dynamics in the Darss Zingst Bodden Chain (DZBC), a southern Baltic estuary, are characterised by summer cyanophyte/chlorophyte dominance, but with winter blooms of mixotrophic cryptophytes, particularly associated with periods of ice cover. Analysis and simulation of a mixotrophic Lotka-Volterra competition model shows that coexistence of algae and cryptophytes is unlikely under static conditions, with seasonal or stochastic variation in parameters, as well as with time lags. However, incorporating production by cyanophytes/chlorophytes of non- toxic allelopathic substances allows stable coexistence of algae and mixotrophs. When parameterised using empirical DZBC data for light, temperature and ice cover, the model gives a good represen- tation of cryptophyte dynamics and bloom formation. We conclude that both mixotrophy and allelopathy are necessary ingredients of community coexistence and dynamics in the DZBC.

Dissolved organic matter along the eutrophication gradient of the Darβ–Zingst Bodden Chain, Southern Baltic Sea: I. Chemical characterisation and composition

The Darβ–Zingst Bodden Chain (DZBC) is a shallow tideless estuary of 4 separate basins containing extremely high contents of particulate organic matter (POM) because of an eutrophication for more than 30 years. Therefore the open question to be addressed in this study was whether and how high POM is reflected in amounts and composition of dissolved organic matter (DOM). The pelagial was sampled at different stations along the eutrophication gradient during the growing season 1996, as well as in winter 1995/96 and 1996/97 to assess seasonal variations. The chemically utilisable compounds (uDOM) like dissolved free amino acids (DFAA) and dissolved free carbohydrates (DFCHO), as well as the corresponding polymer fractions dissolved combined amino acids (DCAA) and dissolved combined carbohydrates (DCCHO) were analysed together with the total dissolved organic carbon (DOC) and total dissolved organic nitrogen (DON). The concentrations of these fractions were used to calculate the respective percentage contribution of the DOC and DON and to compare with the C:N ratio in the dissolved pool. In the DZBC very high absolute amounts of DOM components of up to 30 μmol C l − 1 for DFAA, 288 μmol C l − 1 for DCAA, 67 μmol C l − 1 for DFCHO, 196 μmol C l − 1 for DCCHO were determined. On average, proportions of 0.8% DFAA, 3.6% DFCHO, 6.5% DCAA and 12.6% DCCHO of DOC were measured in the growing season of 1996. Consequently, at least 23.5% of DOC in the DZBC were classified as readily utilisable. The concentrations of these bio-available compounds fluctuated strongly over the course of the year, but the dissolved monomers more than the corresponding polymers. With the exception of DFAA at significantly higher concentrations in winter, a clear seasonality in DOM compounds was absent. In spite of the high amounts of uDOM, most likely being able to sustain many microheterotrophs, the quality of the total DOM has to be assessed as recalcitrant due to an average molar C:N ratio of ca. 19. This fact makes the Darβ–Zingst Bodden Chain quite unique concerning persistent high amounts of utilisable and refractory organic matter. So far, it was not possible to prove whether the high DOM originates directly from primary production, is mostly the result of microbial degradation in the pelagial or stems from anaerobic degradation in the sediment. However, the high DOM concentrations, its element composition and the accumulation of glycine and serine in the dissolved amino acid pool suggest that the degradation of DOM was advanced. Such analyses seem to be an additional tool to describe the ecological state of highly polluted waters and estimate the origin and fate of organic matter.

Population dynamics of pikeperch ( Sander lucioperca) and its linkage to fishery driven and climatic influences in a southern Baltic lagoon of the Darss-Zingst Bodden Chain

Our study uniquely analyzes the population structure (stock sizes N in numbers, biomass B, recruitment R, spawning stock biomass SSB, yield-per-recruit Y/ R, catch-to-biomass ratios Y/ B) and the influence of natural (North Atlantic Oscillation NAO, regional environmental variables) and anthropogenic (fishing mortality F) forces on the population dynamics of a single isolated stock of the pikeperch, Sander lucioperca, in the north-eastern Baltic coast of Germany over a 25 years time period. N and F were estimated using the statistical virtual population analysis (VPA) approach while B, SSB, R, Y/ R, Y/ B were derived from these. Based on segmented regressions, the study of anthropogenic influences revealed a significant effect of F on R; an effect of F on Y/ B was partly significant. In both cases a changepoint value of F = 0.56 was found. Based on cross-correlations and general linear regression models, the analysis of the influence of environmental factors detected significant lagged effects of the NAO and local temperatures and salinities on R while classical stock-recruitment models (Beverton/Holt, Ricker) and polynomials did not.

Long-term observations on salinity dynamics in a tideless shallow coastal lagoon of the Southern Baltic Sea coast and their biological relevance

The Darß-Zingst Bodden Chain (DZBC) is a tideless shallow inner coastal water of the Southern Baltic Sea. Important water volumes are exchanged with the Baltic Sea in dependence of wind direction and strength, water levels and coastal water currents. The Bodden chain is a system of 4 consecutive water basins which are connected via narrow streams with the opening to the Baltic Sea in the west. The innermost Bodden basins are predominantly influenced by freshwater and the outermost basins receive more Baltic Sea water. The whole Bodden chain was subject to a substantial eutrophication for decades until 1990. Macrophytes vanished, phytoplankton formed dense blooms throughout the growing season and organic matter accumulated in the system. The water mixing varies in time and is very different for the separate water basins what obscures trends of biological parameters, e.g. phytoplankton composition, primary production and benthic organisms. Thus, the process of 30 years' eutrophication and especially of re-mesotrophication for the last 15 years is difficult to describe and verify without an indicator for the portion of mesotrophic Baltic Sea water at the monitoring locations. Therefore, variability of salinity was described on short-term, seasonal and long-term ranges as well as spatial gradients. The data set is based on 29 years of daily measurements for the central part of the Bodden chain. In contrast to deep fjords of the northern Baltic Sea, maximum salinity changes were ca. 1 psu per day not for more than consecutive 5 days in the same direction. In contrast to the outer coastal waters of the Baltic Sea, lowest salinities occurred always in early spring and highest in autumn indicating a completely different set of meteorological and hydrological parameters affecting seasonality. Annual averages of Bodden salinity correlated with values of the Baltic Sea, but deviations from the mean were twice as high. The long-term mean at the central Bodden chain (Zingster Strom) was 5.6 psu, a salinity where biodiversity is often low. The range of salinity was 1–14 psu which represents an even higher stress factor for sessile organisms than the unfavourable average in the horohalinicum (5–8 psu). The salinity in the more freshwater influenced water basins never exceeded 9 psu. Salinity of the two outermost water basins near the Baltic Sea entrance ranged between 2 and 14 psu. Although annual means of salinity of outer and inner coastal waters correlated conditions in inner coastal waters, it cannot be estimated from Baltic Sea water surveys. Seasonality and statistical variation as well as complicate mixing patterns of the chain-like water basins prevent a direct estimate on salinity at a given site and biologically sensitive time, e.g. hatching time.

Nutrient accumulation and nutrient retention in coastal waters – 30 years investigation in the Darss‐Zingst Bodden chain

AbstractCoastal waters are transitional zones between limnic waters and marine systems. The anthropogenic impact on these water bodies is high and a rapid change of trophic level was observed within the last 50 years. In the Darss‐Zingst Bodden chain (southern Baltic Sea – Mecklenburg‐West Pomerania, Germany), the change in trophic state during the last thirty years can be reconstructed by long‐term monitoring of chemical, hydrographical and biological parameters with an up to daily resolution. Until the 1980s, increased input of the anthropogenic nutrient load from the catchment area has been documented. However, with the implementation of the HELCOM recommendations the input of phosphorus and nitrogen was reduced in the 1990s. In contrast to the reduction of nutrient inputs, a decrease in nutrient concentrations and primary production could not be observed. The reasons are a high internal nutrient load and the release of nutrients out of the sediments. Numerous research projects allowed the description and quantification of these processes. Today, the internal phosphorus pool exceeds the external phosphorus load several fold. These results are the scientific basis for the development of restoration strategies of coastal waters. The development of suitable management plans is necessary for the implementation of the EU Water Framework Directive to guarantee a good ecological state by 2015. The long time acquisition of monitoring data and voluminous complementary specific research projects was enabled by the local field research conditions of the Biological Station of the University of Rostock in Zingst.

Viability of bacteria from different aquatic habitats. I. Environmental conditions and productivity

Various freshwater, estuarine and coastal stations of the Southern Baltic Sea were com- paratively studied to evaluate pelagic bacterial performance. Inner coastal waters (so-called bodden or lagoons) are highly productive systems and dominate the coast of the Southern Baltic Sea. Due to high nutrient loads up to the 1990s in combination with an enhanced primary production, increased amounts of particulate (POC) and dissolved organic carbon (DOC) accumulated in these waters. In the Dars-Zingst bodden chain, POC < 16 and DOC < 13 mg C l -1 , and C:N ratios of 9 to 11 in partic- ulate matter were measured in winter and spring samples. Due to high POC concentrations, the aver- age ratio of DOC:POC was 1.1:1, which is very low compared to other aquatic systems. Bacterial abundance and activities were rather high and reached 24 × 10 6 ml -1 and 18 µg C l -1 h -1 , respectively. Although 2 of the 3 investigated freshwater systems were classified as eutrophic, the highest mea- sured POC concentrations, bacterial abundance and production were much lower (1.6 mg C l -1 , 11 × 10 6 bacteria ml -1 , 4.4 µg C l -1 h -1 ) than in the bodden. In contrast to that, the DOC load was as high as in these inner coastal waters (<12 mg C l -1 ). The coastal stations of the Baltic Sea, classified as mesotrophic, were not severely loaded with organic matter and bacteria (POC < 0.8, DOC < 5.5 mg C l -1 , bacteria < 3 × 10 6 ml -1 ). Bacterial production again was lower than at all other stations; however, levels did reach an exceptional 4.6 µg C l -1 h -1 , which is comparable to values of the freshwater systems. Compared to the other investigated marine and freshwater systems, the bodden were heavily loaded with organic matter, especially particulate organic matter (POM). The origin of this material is assumed to be mainly autochthonous as it is known not to be transported by rivers into these estuaries. Although dissolved inorganic nitrogen (DIN) concentrations were high at least in winter, POM was of poor quality; this was reflected by high C:N ratios and a low contribution of phytoplankton carbon to POC. However, this is particularly surprising, because nitrogen should be readily available at all bodden sites by resuspension from the sediment caused by frequent winds in these very shallow systems of <2 m depth.

Light and temperature acclimation of Rhodomonas salina (Cryptophyceae): photosynthetic performance

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 29:287-296 (2002) - doi:10.3354/ame029287 Light and temperature acclimation of Rhodomonas salina (Cryptophyceae): photosynthetic performance Astrid Hammer1,*, Rhena Schumann1, Hendrik Schubert2 1University of Rostock, Department of Life Sciences, Institute of Aquatic Ecology, Albert-Einstein-Str. 3, 18051 Rostock, Germany 2University of Greifswald, Institute of Ecology, Grimmer Str. 88, 17487 Greifswald, Germany *E-mail: astrid.hammer@stud.uni-rostock.de ABSTRACT: Blooms of phototrophic cryptophytes have been observed in the highly eutrophic estuarine Darss-Zingst Bodden Chain (DZBC), Germany, during prolonged periods of light limitation due to ice and snow covering. The present study analyses possible mechanisms by which Rhodomonas salina, as a surrogate for bloom forming DZBC cryptophytes, maintains large densities during these low light/low temperature conditions. Growth, photosynthetic activity and pigment content were examined under 16 combinations of temperature (5 to 20°C) and irradiance (10 to 150 μmol photons m-2 s-1) under nutrient-saturated conditions in a seawater-based medium. R. salina was tested for its capacity to photoacclimate to different light intensities in relation to temperature by calculating the photoadaptive index Ek (light saturation point of photosynthesis, Pmax/a). Pmax, the maximum photosynthesis rate and a, the efficiency of light utilisation at limited light intensities remained unchanged with respect to irradiance for every temperature tested. Consequently Ek, the irradiance at which photosynthesis rate ceased to be light-limited was constant (mean 49 μmol photons m-2 s-1) within the chosen range of irradiances. This indicated that R. salina failed to adapt to down-shift changes in the light regime, at least in terms of photosynthetic parameters. Pigmentation analyses supported these results showing no acclimation of pigment ratios with regard to growth irradiance for a particular temperature. The calculated irradiance needed for 0 net photosynthesis (Ec) was about 26 μmol photons m-2 s-1 and did not show any significant variation in light or temperature. The failure of R. salina to respond to down-shift changes in the light regime did not result, however, in a reduction in growth at low irradiances (10 μmol photons m-2 s-1). Judging from these results, R. salina seems to pursue an alternative strategy to capture energy under low light conditions which we hypothesise to be uptake of dissolved organic carbon from the seawater-based medium. Follow-up research will concentrate on the relative contribution of heterotrophy to the overall nutrition of R. salina under white ice covering. KEY WORDS: Bloom · Cryptophytes · Rhodomonas salina · Ice · Photosynthesis · Photoacclimation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 29, No. 3. Online publication date: October 23, 2002 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2002 Inter-Research.

Seston particles along a eutrophication gradient in coastal waters of the Southern Baltic Sea: Significance of detritus and transparent mucoid material

Exposed to over 30 yr of continuous eutrophication, the Dars-Zingst bodden chain, a shallow tideless estuary accumulated large amounts of particulate organic matter (POM). We sam- pled along the eutrophication gradient throughout the vegetation period 1996, in order to assess POM properties. Besides parameters describing the chemical composition, such as C/N ratio, protein content and protein:carbohydrate ratio, particles were microscopically analysed. From the volumes of non-transparent, nucleic acid-containing (fluorescently labelled by propidium iodide) and organic particles (stained with DTAF), the percentages of detrital and transparent mucoid material were derived. Ten to 63% of particulate organic carbon (POC) in the bodden system consisted of carbon from bacteria, phytoplankton and protozoans. Of the total organic particle volume, up to 46% were microorganisms. Although detritus volume averaged 14%, maximum values of 68% could be deter- mined. Most of the organic particle volume consisted to 64% of transparent mucoid matter, which is an important carbon compartment in material cycling (e.g. settling substrate). At higher POC con- centrations the chemically unidentified material as well as the mucoid matter were quantitatively more important compared to the mesotrophic Baltic Sea station, where the portion of detritus (62% on average) was much higher. The microscopically derived quantification of detrital and mucoid mat- ter provides additional information on the suitability of seston as settling substrate, its age, origin and physical properties. Since the riverine water input into the bodden system is small and its POC con- centration lower compared to the bodden itself, most of the estuarine POM was obviously produced locally. Detritus from submersed macrophytes did not occur before the end of the vegetation period in October and thus cannot contribute significantly to the POM analysed in this study. The high amounts of POM in the bodden system probably originate mainly from pelagic primary production. The sedimentation of POM, its processing in and frequent resuspension from the several mm-thick flocculent sediment layers, seems to be the main source for the high amount of mucoid particles.

Enzyme activities and allozyme polymorphism in two genetic types (or sibling species) of the genus Marenzelleria (Polychaeta: Spionidae) in Europe

Two populations of Marenzelleria spp. from the North Sea and the Baltic Sea that had already been characterized by allozyme electrophoresis and found genetically different in 1994 were again examined in 1997. The genetic identity (I = 1.0) examined in 1994 and 1997 shows that the structures of the populations of genetic Type I in the North Sea (Ringkobing Fjord) and genetic Type II in the Baltic Sea (Darss–Zingst Bodden chain) are stable. Three diagnostic gene loci that were determined additionally (citrate synthase, one locus; alanine aminotransferase, two loci) support the hypothesis of the existence of two sibling species of the genus Marenzelleria in Europe. In addition, the activities of ten electrophoretically separated enzyme systems were measured in the worms immediately after removal from their habitat and after they had been kept in the laboratory for 2 months. Under both conditions four enzymes showed significant differences between genetic types. The higher activity of the alanine aminotransferase of the North Sea worms (Type I) is discussed in the context of the different preferred salinities of the two Marenzelleria sibling species.

Discharge areas — A comparison between three regions in the southern Baltic

Tideless estuaries are very common on the western, southern and eastern Baltic coast. They play an important role as buffers and filters for the Baltic Proper. These functions can vary, depending on discharge areas and the situation in the estuaries themselves. Our knowledge of the estuaries varies widely, ranging from more or less simple descriptions to a fairly complete understanding of the processes taking place in their ecosystems. So far, only one preliminary comprehensive study has been performed for the whole area (Baltic Sea Environment Proceedings No. 40, HELCOM 1991). Three different discharge areas connected to tideless estuaries are compared in some detail: - the shallow polytrophic Darss-Zingst Bodden Chain, Germany - the shallow eutrophic Puck Bay, Poland - the deeper mesotrophic Gulf of Riga, Latvia. Starting points are discharge areas, discriptions of the water bodies and main loads. The development of the ecosystems under the influence of anthropogenic impacts during the last 40 years is then described. Conclusions are drawn concerning: - the general behaviour of such systems - the benefits and drawbacks of the discharge areas, the loads, and the structures and functions of the estuaries - special problems regarding the buffer and filtering capacities of the systems in question - economic consequences. High variability and elasticity are the main characteristics of these tideless estuarine ecosystems. Multivalente economic utilization of these resources and functions is the best way to save such ecosystems and money as well.

Salinity, Inorganic Nutrients, and Primary Production in a Shallow Coastal Inlet in the Southern Baltic Sea (Nordrügenschen Bodden) Results from Long‐Term Observations (1960–1989)

AbstractThe Nordrügenschen Bodden waters are a shallow coastal inlet of the Southern Baltic Sea consisting of individual basins, some of which are joined only via small connections. The Bodden are characterized by pronounced horizontal gradients in hydrographical, chemical and biological parameters. Whereas concentrations of inorganic nutrients increase, salinity decreases with increasing distance from the connection to the Baltic Sea. Between 1960 and 1989 long‐term variations of salinity, inorganic nutrients (ammonium, nitrate, phosphate), Secchi disk visibility, and planktonic primary production were monitored at 6 locations throughout the Bodden. The gradients were most pronounced during the first period of observation (1960–1963). Between 1960 and 1985 concentrations of inorganic nutrients in the adjacent Arkona Sea increased up to values several times higher than the previous concentrations. This increased nutrient load in the Baltic Sea was reflected by higher nutrient concentrations and higher primary production in the outer and central parts of the Nordrügenschen Bodden. Between 1963 and 1965 the shipping channel between the outer (Libben) and the inner part (Großer Jasmunder Bodden) of the Bodden chain was dredged. This led to an improvement of water exchange between the Baltic Sea and the Bodden, resulting in a significant reduction of the gradients of chemical and biological parameters. Whereas salinity and Secchi disk visibility increased, inorganic nutrients, and primary production decreased. This was most obvious in the inner parts of the Bodden where the water quality was improved. The trophic status of the Kleiner Jasmunder Bodden is still worrying. This Bodden represents the innermost part of the Nordrügenschen Bodden connected with the Großer Jasmunder Bodden only via a small flood gate. Unless the water exchange is drastically improved, the Kleiner Jasmunder Bodden will retain its hypertrophic status in the longer term. The future development of the trophic status of the Bodden is discussed.

Marenzelleria viridis (Verrill, 1873) (Polychaeta), a new benthic species within European coastal waters Some metabolic features

The polychaete Marenzelleria viridis (Verrill, 1873) is a recent invader of European brackish waters (North Sea and Baltic Sea). As a member of the coastal infaunal community, dwelling in permanent tubes, M. viridis is frequently subjected to extreme environmental conditions, such as periods with restricted oxygen availability. When exposed to experimental anoxia, M. viridis follows in general the metabolic pathways exploited by many marine invertebrates. However, some differences become obvious. In contrast to most polychaetes, M. viridis used phospho- l-arginine for short-term energy provision and octopine was found to be the only end-product of cytosolic glycolysis. Alanopine and strombine, which were also measured were only found in traces. This corresponds with the relatively high activity of the octopine dehydrogenase (18 U g −1 wet wt.), whereas the activities of other known pyruvate oxidoreductases were clearly lower or almost zero. Remarkable differences in the mode of anaerobic energy production were not found in populations with different salinity regimes from the Baltic Sea (Darss-Zingst bodden chain, S 8%.) and the North Sea (Ems estuary, S 15%.). Although glycine concentrations were clearly higher in the North Sea population, strombine did not occur as end-product of anaerobic glycolysis. However, alanine was accumulated to a higher amount in the North Sea population, albeit the concentrations of alanine were nearly the same in both populations. Compared to other marine polychaetes, M. viridis (North Sea and Baltic) showed only a moderate resistance against anoxic conditions. The reasons appear to be the relatively low glycogen content and insufficient reduction of the energy demand, indicated by the strong decrease in the energy charge after 24 h (0.82 to 0.70). Furthermore, M. viridis switched much earlier to energy production via the ‘propionate pathway’ and propionate was first detected in the incubation medium three hours after onset of anoxia. However, in M. viridis anaerobic energy production started at a very low oxygen tension (critical p O 2 at about 2 kPa) which indicates a very efficient use of oxygen even at severe hypoxia.