Palynomorph- and chironomid-based analyses of Eemian, Weichselian, and Holocene ecosystem- and climate dynamics in the Baltic Sea region
Final Report Abstract
Since it was not possible to analyse palynomorphs in pre-Holocene sediments (mainly due to preservation issues), the project focus was mainly directed to sediments comprising the past ~8000 years. The planned examination of chironomid remains proved to be ineffective after tests for Site M0059 showed that the concentration such remains was much lower than expected. Only for the northernmost sites (M0061/M0062) of IODP-Expedition 347, chironomid-related studies might still be a useful approach. For Site M0059 (Little Belt, southwestern Baltic Sea), a multi-proxy overview over the development of the area could be generated, including salinity and quantitative temperature reconstructions. Among other findings, it could be shown that lacustrine conditions occurred in the Little Belt until ~7400 years before present and that there was no connection to the Kattegat at this time. The transition to the Littorina Sea stage occurred quickly within ~200 years. While salinity proxies generally revealed similar trends, temperature proxies, particularly for marine conditions, did not accord to each other in many cases. This implies that the application of modern-day proxy calibrations to intervals which experienced change from freshwater to marine conditions is problematic. Pollen-based results imply generally increasing winter temperatures until today, but decreasing summer temperatures. For the pollen-based data, an anthropogenic bias cannot be excluded though, particularly for the late Holocene. Organic-rich layers at several sites can be tied to hypoxic/anoxic conditions. An early hypoxia phase is related to the Holocene thermal maximum (lasting until ~5000 years before present) and to increased temperature, salinity and primary productivity. A second Holocene period of hypoxia without indications for increased salinity coincided with the so-called Medieval Climate Anomaly around ~1000 years before present. For Sites M0061/M0062 (Ångermanälven Estuary, northern Baltic Sea) ecological shifts driven by salinity, isostacy and strength of the Ångermanälven River discharge could be identified. Among other findings, it could be shown that during the early Littorina Sea stage, a particularly marine phase occurred. Pollen data generated in the framework of this project could be used to reconstruct terrestrial changes and palaeotemperatures, and furthermore to control age models via comparison with terrestrial pollen records. In several cases, anthropogenic influence could be identified via cultivated-Poaceae pollen grains as indicators for agricultural activity. Marine palynomorph data could be used to analyze coeval changes within the marine realm. The project has led to new research ideas which will be followed in a further DFG project.
Publications
- (2014): Reconstructing paleo-temperatures in the Baltic: a multi-proxy comparison from IODP site M0059 (Little Belt). The 12th Colloquium on Baltic Sea Marine Geology, 2014, Warnemünde
Groeneveld, J., Kotthoff, U., Granoszewski, W., Bauersachs, T., Ash, J., Fanget, A.-S., Krupinski, N.Q., Stepanova, A., Peyron, O., Andren, T., Cotterill, C., and Exp. 347 Science Party
- (2015): Reconstruction of the palaeoecological evolution of the Holocene Bothnian Sea region on the basis of palynomorphs from two IODP-sediment cores from the Ångermalnäven Estuary. 2nd post-cruise meeting of IODP Expedition 347 and subsequent Baltic Sea Colloquium 2015, Stockholm
Brandt, H.-T., Michaelis, O., Kotthoff, U.
- Expedition 347 Science Party (2016): Reconstructing Holocene palaeo-environmental conditions in the Southwestern Baltic (Little Belt, IODP Expedition 347, Site M0059): A multi-proxy comparison. International Congress of Paleoceanography 2016, Utrecht
Kotthoff, U., Andrén, E., Andrén, T., Ash, J.L., Bauersachs, T., Fanget, A.-S., Granoszewski, W., Groeneveld, J., Krupinski, N.Q., Peyron, O., Slomp, C.P., Stepanova, A., Warnock, J., van Helmond, N.
- (2017): Controls of the onset and termination of past hypoxia in the Baltic Sea. Palaeogeography, Palaeoclimatology, Palaeoecology 490, 347-354
Papadomanolaki, N.M., Dijkstra, N., van Helmond, N.A.G.M., Hagens, M., Bauersachs, T., Kotthoff, U., Sangiorgi, F., Slomp, C.P.
(See online at https://doi.org/10.1016/j.palaeo.2017.11.012) - (2017): Holocene environmental history of the Ångermanälven Estuary, northern Baltic Sea. Boreas
Warnock, J.P., Bauersachs, T., Kotthoff, U., Brandt, H.-T., Andrén, E.
(See online at https://doi.org/10.1111/bor.12281) - (2017): Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059). Biogeoscience 14, 5607-5632
Kotthoff, U., Groeneveld, J., Ash, J.L., Fanget, A.-S., Quintana Krupinski N., Peyron, O., Stepanova, A., Warnock, J., van Helmond N.A.G.M., Passey, B.H., Clausen, O.R., Bennike, O., Andrén, E., Granoszewski, W., Andrén, T., Filipson, H.L., Seidenkrantz, M.- S., Slomp, C.P., Bauersachs, T.
(See online at https://doi.org/10.5194/bg-14-5607-2017) - Expedition 347 Science Party (2017): Agricultural activity in the Baltic region and coeval terrestrial and marine ecosystem changes – palynological pilot studies (IODP Exp. 347 Sites M0059, M0063). Geo-Bremen 2017, Bremen
Brust, P.C., Wienholz, D.J., Kotthoff, U.
