Abstracts (Sediment part, week 1)

Lecture: Wadden Sea Research (Meinhard Simon)

Tidal flat areas are an important feature of many coastlines of the world. They belong to the most productive natural ecosystems on earth and play an important role in global biogeochemical cycles. One of the largest continuous tidal flat zones extends along the North Sea coast from Denmark via Northwest Germany to the Netherlands. A profound knowledge of the physical, biological and chemical processes in the tidal flats is one of the prerequisites for adequately protecting these unique environments and for understanding their morphological and ecosystem development under the influence of global change. In eight years of intense field and laboratory investigations in the backbarrier tidal flats of Spiekeroog island (Northwest Germany), the Research Group on BioGeoChemistry of Tidal Flats achieved a deep understanding of the currents systems, transport of particulate and dissolved matter in the water column, and the transformation of decayed biomass by microorganisms.

Excursion: Quaternary Geology, Landscape and Settlement History in the Coastal Region of Lower Saxony (Holger Freund)

The excursion gives the participants an overview of the near surface geology in the coastal region of Lower Saxony, as well as on the influence of man on the development of the coastal landscape by diking, settlement, drainage and agriculture. Examples of the typical landforms and some of the sediments and structures will be seen. The focus will be on the mixture of coastal landscape and the Pleistocene, the so called “Geest” in the region around Wilhelmshaven. Features of the excursion are

• Transition of Pleistocene landscape and marshland at Zetel
• Cores of Saalian and Elsterian deposits
• History of the Jade Bay, Coastal cliff at Dangast
• Cores of Holocene coastal deposits
• Salt marsh environment and deposits at Cäciliengroden
• Typical dwelling mound (“Wurt, terpen”) at Ziallerns
• Historical dikes and morphological features of diking, dike breaches and drainage systems

Special equipment is not necessary; rubber boots or trekking shoes for a short walk through the salt marsh are recommended.

Field work on a tidal flat (several lectures)

We will go by boat to a tidal flat south of Spiekeroog and spent there a few hours during low tide. We will take a sediment core of approx. 5 m length using a vibro corer. Further we will sample pore water from different depths and at different distances from the low water line by means of stationary and portable pore water samplers, and rhizones. Back at ICBM-Terramare, the core will be cut into two halves and samples for microbiology will be taken. We will analyze the samples and sediment core during the following two days.
Wind breaker and sun protection are highly recommended, shorts or swimming clothes, and sport or surf shoes may be useful.

Lecture: Sediments and organic matter in the Wadden Sea (Jürgen Köster)

The Wadden Sea is a highly active sedimentary system with continuous erosion and deposition of sediments. The lecture gives a shot introduction to sedimentology and sediment properties in the Wadden Sea. Organic matter in sediments is the driving force for microbiological and many biogeochemical processes. In the Wadden Sea it derives from primary production and reworking of ancient organic matter (peat). A short overview will be given how organic matter is characterized geochemically.

Lab exercise: Core description the Wadden Sea (Jürgen Köster, Holger Freund, and Elke Ahrensfeld)

Knowledge on the sediment properties is an essential base for understanding microbiological, biogeochemical, and hydrodynamic processes in the Wadden Sea. We will describe a sediment core drilled the days before on the Janssand, compile a lithological profile and discuss sedimentological features. Further, we will take samples and analyze the grain size distributions.

Lecture: A decade of subsurface microbiology on tidal-flat sediments (Bert Engelen)

The lecture will give an overview on subsurface microbiology that was conducted within the project “Biogeochemistry of Tidal Flats”. This kind of research was truly interdisciplinary with ICBM geochemists working closely together with microbiologists from the same institute. During the lecture, the distribution of different physiological groups of microorganisms and their role in shaping biogeochemical gradients will be explained. Furthermore, similarities between the shallow and the deep subseafloor biosphere will be highlighted. As many previous investigations were performed on the Janssand tidal flat, the participants will gain background information on the site where they recovered their own sediment core.

Lab work: Total cell counts in tidal-flat sediments (Bert Engelen)

During this lab work, the participants will determine the total cell number along the depth profile of the sediment core from site Janssand. The cells within sediment slurries from selected layers will specifically be stained with the nucleic acid dye SybrGreen I. The total number of cells will be counted directly under an epifluorescence microscope. Additionally, the program “Count Them” will be used for automated counting. Finally, the total cell counts will be correlated to geochemical profiles. The participants will experience the specific challenges of counting cells in sediments.

Lecture: Pore water biogeochemistry and in situ-sensors (Melanie Beck and Oliver Zielinski)

The Janssand tidal flat is situated in the backbarrier tidal area of Spiekeroog Island. Due to the tides and its sand-dominated sediments, the Janssand margin is influenced by both diffusion and advection. This leads to a continuous transport of organic matter and electron acceptors into the sediment enhancing microbial activity and remineralization. This is reflected, for example, in high nutrient concentrations such as phosphate, ammonium or silicate in pore waters. In contrast, sediments more than hundred meters afar from the tidal flat margin are microbially and biogeochemically less active. Automated sensor systems are required to perform high frequent sampling in marine sediments on longer time scales. In-situ sensors for biogeochemical parameters, based on physical, optical and chemo-optical technologies are available or under development. An introduction and overview will be given.

Lab exercise: Nutrient and CDOM analysis (Melanie Beck, Carola Lehners and Oliver Zielinski)

Nutrients like phosphate or ammonium are produced during organic matter degradation. Thus, nutrients can be used as first indicators whether sediments contain easily degradable organic matter and are microbially active. As an example, phosphate will be measured photometrically. Chromophoric dissolved organic matter (CDOM) is an optically active fraction of DOM in water. It is characterized by an exponentially decay of absorption over wavelength. Characteristic features will be extracted from the samples using UV-VIS photometry. Additionally fluorescence signatures from samples will be derived, both methods aiming at a characterization of organic matter transformation in sediments.

Lecture: Groundwater – surface water interactions at the coastal zone: Concepts and methods (Thosten Dittmar and Hannlore Waska)
Lab: Measurement of radioisotopes/establishment of a simple mass balance (Hannlore Waska)

The advective flow of seawater and fresh groundwater through coastal aquifers drives a variety of biogeochemical processes by accelerating the remineralization of buried organic matter and by acting as a carrier of a large amount of chemical species across redox boundaries to the coastal ocean. In this lecture definitions, driving forces, quantitative methods, and geochemical and ecosystem effects of this phenomenon will be discussed. A tracer-based method will be described to exemplify a mass-balance model for the determination of groundwater and pore water fluxes.

Lecture: Numerical Groundwater Modelling (Karsten Lettmann)

The aim of this lecture is to provide the students with basic knowledge of hydrological modelling. Starting with the basic mathematical equations of mass and momentum conservation, the implementation of these equations into numerical codes is explained.
Furthermore a brief introduction of different spatial numerical grids is provided. Finally, the application of these methods is demonstrated to problems of submarine groundwater discharge in coastal areas.

Excursion to Spiekeroog (Birte Junge)

The one-day trip to Spiekeroog, one of the East Frisian Islands, starts with a cruise through the Wadden Sea National Park. A guided tour through the village Spiekeroog with its church from 1696 and a house with a “swimming roof” follows. Afterwards, we will visit the Environmental Centre Wittbülten to have a look at the exhibition and to make a lunch break. In the afternoon, the excursion continues with a walk through the sand dunes of different ages. An overview will be given on the islands’ history, the development of the vegetation and the characteristics of the soils. Before leaving, some time is left for enjoying the beach or one of the nice cafes in the village