Mecklenburg Bay Research Articles

Late-glacial and early Postglacial finds of Ancylus fluviatilis from the southwestern Baltic Sea

The small limpet Ancylus fluviatilis is reported from two sediment cores from the south-western Baltic Sea. One of the occurrences, from Mecklenburg Bay, is dated to the late-glacial, corresponding to the Baltic Ice Lake stage of the Baltic Sea. The other occurrence, from the south-western part of the Bornholm Basin, is dated to the earliest Holocene, corresponding to the Yoldia Sea stage. These appear to be the first reports of Ancylus fluviatilis shells from submarine deposits from the Baltic Sea.

Hydrographic thresholds in the western Baltic Sea: Late Quaternary geology and the Dana River concept

Since the final Weichselian deglaciation the water exchange between Kattegat and the Baltic Sea and hence the palaeogeographical development of the (western) Baltic has been controlled by a number of sills. Major thresholds are found at the southern entrance of the Great Belt and in the Darss Sill area. The easternmost of these structures is formed by Late Weichselian sands at a level of 24 m below present sea level (bsl) at the Falster–Rügen sand plain. A second threshold consisting of till was found within the Kadet Channel at a level of 23–24 m bsl. Thus, we exclude water exchange between Mecklenburg Bay and the Arkona Basin at levels below 24 m since the end of the Pleistocene. A high resolution sediment echosounder survey at the triple junction area of Langeland Channel, Vejsnaes Channel and Winds Grave Channel showed outcropping glacial deposits. Narrow channels incised at a level below 25 m bsl are filled partly with fine grained organic rich late- and postglacial sediments. Assuming no substantial crustal movements in this area in the Holocene no Ancylus Lake drainage at a level deeper than 25 m bsl is likely to have occurred here.

Evidence of nitrogen fixation by non-heterocystous cyanobacteria in the Baltic Sea and re-calculation of a budget of nitrogen fixation

Nitrogen fixation rates and related plankton parameters were determined at 8 sta- tions in the Baltic proper and Mecklenburg Bay in 1997 and 1998. Nitrogen fixation was mea- sured with 15 N-tracer method in unenriched samples. Measurable nitrogen fixation rates were found from July to October, with highest rates in August when heterocystous cyanobacteria formed blooms. Nitrogen fixation rates measured during a moderate bloom in 1998 were related to biomass of heterocystous and coccoid (non-heterocystous) cyanobacteria and primary produc- tion. The size fraction <10 µm contributed significantly to total nitrogen fixation both during day and night. It is discussed whether this may be due to small, non-heterocystous cyanobacteria, which were abundant in summer and autumn. They may separate photosynthesis and nitrogen fixation temporally (day and night) and may be especially responsible for the high nitrogen fix- ation rates observed in the dark. As the fraction of pico- and nanoplankton was not considered in earlier studies, a new budget of nitrogen fixation in the Baltic proper has been estimated. On average, daily nitrogen fixation rates of 2.5 mmol N m -2 d -1 (in July/August 1997/1998) and mean annual nitrogen fixation of 125 mmol N m -2 yr -1 were estimated for the Baltic proper. The high variability is discussed. For summer 1998, a budget of the nitrogen cycle at the main station in the Gotland Sea is given.

The Littorina Transgression in the Western Baltic Sea as Indicated by Subfossil Chironomidae (Diptera) and Cladocera (Crustacea)

Subfossil remains of chironomids, cladocerans and foraminifers found in four sediment cores from the Vejsnaes Basin, Neustadt Bay, Mecklenburg Bay, and Kiel Fjord were analyzed. The faunal assemblages from below the Littorina Transgression horizon represented a rich cladoceran and chironomid fauna typical of freshwater habitats. Above the transgression horizon chydorids disappeared, foraminifers appeared and the diverse chironomid fauna was replaced by an assemblage of three taxa, Clunio marinus, Chironomus salinarius, and Cricotopus/Halocladius, which are typical of brackish/marine conditions.

The Littorina Transgression in the Western Baltic Sea as Indicated by Subfossil Chironomidae (Diptera) and Cladocera (Crustacea)

Subfossil remains of chironomids, cladocerans and foraminifers found in four sediment cores from the Vejsnaes Basin, Neustadt Bay, Mecklenburg Bay, and Kiel Fjord were analyzed. The faunal assemblages from below the Littorina Transgression horizon represented a rich cladoceran and chironomid fauna typical of freshwater habitats. Above the transgression horizon chydorids disappeared, foraminifers appeared and the diverse chironomid fauna was replaced by an assemblage of three taxa, Clunio marinus, Chironomus salinarius, and Cricotopus/Halocladius, which are typical of brackish/marine conditions.

Early Holocene history of the southwestern Baltic Sea: the Ancylus Lake stage

One of the most discussed stages in the history of the Baltic Sea is the Ancylus Lake phase. This paper presents detailed information from the Darss Sill threshold area as well as the adjacent basins, i.e. the Mecklenburg Bay and Arkona Basin located in the southwesternmost Baltic. The threshold area was transgressed at the Baltic Ice Lake maximum phase and during the following regression about 10.3 ka BP a river valley was incised in the Darss Sill to a level of 23–24 m below present sea level (b.s.l.). Preboreal sediments in the study area show lowstand basin deposition in the Arkona Basin and the existence of a local lake in Mecklenburg Bay. The lowstand system is followed by the Ancylus Lake transgression that reached a maximum level of 19 m b.s.l. Thus, at the maximum level the water depth was about 5 m over the threshold, and the shore level fall during the Ancylus Lake regression must be in the same range. The Darss Sill area is the key area for drainage of the Ancylus Lake, and if the previously suggested regression of 8–10 m in southeastern Sweden is to be achieved, isostatic rebound must also play a role. The existence of the so‐called Dana River in the Darss Sill area cannot be supported by our investigations. We observed no signs of progressive erosion of the Darss Sill area in the Early Holocene, and there are no prograding systems in Mecklenburg Bay that can be related to the Ancylus Lake regression. On the contrary, local lakes developed in Mecklenburg Bay and in the Darss Sill threshold area. In the Darss Sill area, marl was deposited in a lake in the valley that developed after the final drainage of the Baltic Ice Lake. Studies of diatoms and macrofossils, combined with seismic interpretation and radiocarbon dating, provide detailed information about the chronology and the relative shore level of these lake phases as well as about environmental conditions in the lakes.

Late- and postglacial shore level changes in the southwestern Baltic Sea

Sub-marine deposits in the region of the Arkona Basin, Mecklenburg Bay and Darss Sill have been studied using a multi-disciplinary approach that includes shallow seismic work, depositional sequence stratigraphy, radiocarbon dating and analyses of diatoms and macrofossils. Models for the relative shore level changes in the two basin areas are proposed. Both in the Mecklenburg Bay basin and in the Arkona Basin maximum shore levels of c. 20 m below present sea level were reached in late Allerød, in late Younger Dryas and in late Preboreal. The drainage of the Baltic Ice Lake led to shore level drops, but in Mecklenburg Bay the drop only amounted to around 5 m, because the Darss threshold hindered further regression. In the Arkona Basin, the drop after the final drainage of the Baltic Ice Lake was approximately 20 m, whereas the water level falls after the Allerød drainage of the Baltic Ice Lake and after the Ancylus Lake maximum, have not yet been determined. The Darss Sill area became a land area with local lakes after the Ancylus Lake drainage; there is no evidence of erosion or fluvial/deltaic sediments in Mecklenburg Bay that could be referred to the proposed so-called Dana River. The evolution of the shore level after the Boreal lowstand is poorly confined by our data, but hydrographic conditions similar to the present were established at c. 7.6 cal. ka BP.

Scavenging and particle residence times determined from 234Th/ 238U disequilibria in the coastal waters of Mecklenburg Bay

Activities of the naturally occurring radionuclide 234Th were determined in water samples of Mecklenburg Bay (SW Baltic Sea) using a new Th-specific diatomite adsorption technique followed by liquid scintillation spectrometry. Activities of “dissolved” (operationally defined as Th in the centrifugate) and particulate 234Th varied in the range of 1.4–6.9 and 0.9–9.3 mBq l −1, respectively. A significant correlation between K d and SPM concentration was found. From this particle-concentration effect, the “colloidal pumping” model predicts that 98% of the “dissolved” Th is associated with colloids rather than being truly dissolved. Relative to calculated activities of the parent nuclide 238U in the Bay, the 234Th data yielded mean 234Th scavenging residence times in the range of 1.2–9.7 days. Particulate 234Th activities are inversely correlated to SPM concentrations. Particle residence times ranged from a few days in winter up to 20 days in spring characterized by less intense bottom currents. The hydrodynamic regime is the master variable controlling scavenging of Th and other similarly particle-reactive elements in Mecklenburg Bay.

The Baltic Ice Lake in the southwestern Baltic: sequence‐, chrono‐ and biostratigraphy

Jensen, J. B., Bennike, O., Witkowski, A., Lemke, W. &amp; Kuijpers, A. 1997 (September): The Baltic Ice Lake in the southwestern Baltic: sequence‐, chrono‐ and biostratigraphy. Boreas, Vol. 26, pp. 217–236. Oslo. ISSN 0300–9483.This multidisciplinary study focuses on late‐glacial deposits in the Mecklenburg Bay ‐Arkona Basin area. The sequence stratigraphical method has been used on shallow seismic and lithological data, in combination with biostratigraphical work and radiocarbon dating. Glacial‐till deposits underlie sediments from two Baltic Ice Lake phases. Varved clay deposits from the initial phase cover the deepest parts of the basins. A prograding delta is observed at the western margin of the Arkona Basin, prograding from the Darss Sill area. The delta system is possibly related to a highstand dated at 12.8 ka. A maximum transgression level around 20 m below present sea level (b.s.l.) is inferred, followed by a drop in water level and formation of lowstand features. The final ice lake phase is characterized by a new transgression. The transgression maximum as observed in the Mecklenburg Bay is represented by transgressive and highstand deltaic deposits. These also indicate a maximum shore level of 20 m b.s.l. The deltaic sediments that contain macroscopic plant remains and diatoms have yielded Younger Dryas ages. Mapping of the late‐glacial morphology of the Darss Sill area reveals a threshold at 23 to 24 m b.s.l. This means that the Baltic Ice Lake highstand phases inundated the Darss Sill, which implies that the westernmost extension of the Baltic Ice Lake reached as far as Kiel Bay. Forced regressive coastal deposits at the western margin of the Arkona Basin mark a lowstand level of around 40 m b.s.l. caused by the final drainage of the Baltic Ice Lake. The lowstand deposits predate lacustrine deposits from the Ancylus Lake, which date to approximately 9.6 ka BP.

Periodic and episodic benthos recruitment in southwest Mecklenburg Bay (western Baltic Sea)

Temporal changes in the zoobenthos of southwest Mecklenburg Bay were studied using routine survey data collected in 1980–94. Earlier studies suggested that long-term oxygen deficiency on the scale of several months affects the zones below 20 m depth. Episodic benthic recolonization occurred during periods with improved oxygen conditions, as a rule by opportunistic polychaetes followed by some actively immigrating adult species. However, these observations were restricted to central and southern Lübeck Bay. Our recent data indicate that benthic recolonization exhibits greater regularity along the northern shore of Lübeck Bay. Special wind conditions and water exchange processes in the western Baltic Sea are likely to displace the deep water in northern Lübeck Bay more rapidly than in the southern zones. By means of multidimensional scaling, two types of episodic recruitment are identified in the benthos that are probably related to enhanced nitrogen discharge through river runoff in the winter and exceptionally weak water stratification in the summer.

Population dynamics and ecoparasitological surveys of Corophium volutator in coastal waters in the Bay of Mecklenburg (southern Baltic Sea)

DAO Diseases of Aquatic Organisms Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials DAO 29:169-179 (1997) - doi:10.3354/dao029169 Population dynamics and ecoparasitological surveys of Corophium volutator in coastal waters in the Bay of Mecklenburg (southern Baltic Sea) Meißner K, Bick A The population dynamics of Corophium volutator (Pallas, 1766) were studied at 2 stations in virtually tideless water in the Bay of Mecklenburg (southern Baltic Sea). Particular attention was given to temperature, the main factor affecting reproductive and development processes. Infestation by parasites was one of various factors which was considered for explanation of variations in abundance in the course of the year. At both stations 2 generations were present during the reproduction period. These were called the spring generation and summer generation (with cohorts I and II) in accordance with their occurrence. The greatest increase in abundance coincided with the appearance of the spring generation. Most of the overwintering individuals originated from summer generation I in both populations. Although reproductive activity was the same at both stations, the variations in abundance were completely different; the population at one station collapsed almost completely. Ecoparasitological analysis revealed that mortality in the extremely heavily infested spring generation was unusually high, and this had a direct impact on subsequent reproductive processes. The much more severe infestation at one station than at the other was found to be caused by a 4-fold higher abundance of the wadden snail Hydrobia spp., which is the primary intermediate host of the larval trematodes found in C. volutator in these waters. The studies showed that parasite infestation is a factor that can affect population development. Therefore, ecoparasitological phenomena should be taken into account when interpreting data relating to population dynamics. Corophium volutator · Population dynamics · Parasites · Digenetic trematodes · Baltic Sea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in DAO Vol. 29, No. 3. Publication date: June 19, 1997 Print ISSN:0177-5103; Online ISSN:1616-1580 Copyright © 1997 Inter-Research.

Late Pleistocene and early Holocene paleogeography of the Darss Sill area, southwestern Baltic

Abstract Today, about 73% of the water exchange between the Baltic and the North Sea takes place through the Darss Sill area. In hydrographic terms the Darss Sill is a major morphological unit separating the deeper areas of the Mecklenburg Bay and the Arkona Basin from each other. It is characterized by an average water depth of 16 m. The main bathymetric features are the Gedser Reef with a water depth of less than 10 m and the Kadet Channel which has a maximum water depth of 32 m. According to previous authors there are two different ice marginal lines between Falster (Denmark) and the Darss peninsula (Germany). The recent Kadet Channel is regarded as a large glacial valley cutting the ice marginal lines. Joint Danish and German investigations in the Darss Sill area (1989–1991) indicate the existence of only one marginal line in this region, which is represented by a till cropping out in the area between Falster and the German coast. The formation of the marginal line ca. 13,500 BP caused a damming of a pre-existing subglacial drainage system in the Gedser Reef area. Southeast of the recent Kadet Channel glaciofluvial drainage occurred towards the NE through a deep channel into the Baltic Ice Lake immediately after the retreat of the ice. During the Baltic Ice Lake transgression the channel was filled by sandy sediments from sources east of the investigated area. This accumulation process resulted in the blocking of the channel at the time of the Baltic Ice Lake highstand maximum. At this time occasional overflow in the Kadet Channel area must have started. The main erosion and deepening of the Kadet Channel must, however, be ascribed to the Ancylus Lake overflow.

Analysis of a sediment core from the Mecklenburg Bay, with a discussion on the early Holocene history of the southern Baltic Sea

Abstract The stratigraphy of a core taken from the bottom sediments of Mecklenburg Bay in the southern Baltic is studied. Radiocarbon dates of a peat layer about 26 m below sea level show that the peat was formed approx. 9,500 BP. Pollen and diatom analyses were made from the profile. Some features in the biostratigraphy are difficult to explain, but a consistent picture can be drawn of the outline of the postglacial development in this region. The Ancylus transgression did not extend to Mecklenburg Bay, which was inundated by saline water during the Litorina Sea stage of the Baltic.