Groundwater seepage in the marine environment: role for mass flux and bacterial activity

• Published in: Marine ecology. Progress series (Halstenbek) Vol. 178; pp. 169 - 177
• Main Authors: Bussmann, I., Dando, P. R., Niven, S. J., Suess, E.
• Format: Journal Article
• Language: English
• Published: Oldendorf Inter-Research 17-03-1999
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Bacteria; Baltic Sea; Biological and medical sciences; Chlorides; Fundamental and applied biological sciences. Psychology; Germany, Eckernfoerde Bay; Groundwater; Magnesium; Marine; Methane; Microbial ecology; Oxidation; Salinity; Sea water; Sea water ecosystems; Seas; Sediments; Synecology; Various environments (extraatmospheric space, air, water); Europe; Germany; Baltic Sea; ANE, Baltic, Eckernfoerde Bay; ANE, Germany, Schleswig-Holstein, Eckernfoerde Bay; ANE, Baltic Sea; Methane; Microbial activity; Water chemistry; Fresh water discharge; Environmental factor; Sulfates; Sediments; Salinity; Marine environment; Chemical reduction; Production rate; Oxidation; Bay; Mass flow; Ground water
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps178169

In Eckernförde Bay (western Baltic Sea) pockmark structures are induced by groundwater seeping out of the sediment. On 3 occasions in winter and spring 1993-94 we investigated the influence of groundwater on the reduction of salinity, on porewater chemistry, and on bacterial activities (methane oxidation and sulphate reduction). In 2 out of 3 sampling campaigns groundwater discharge could be detected. The concentration gradients of Cl– and SO4= are moved towards the sediment surface by the vertical advection of groundwater during seep times. Without groundwater discharge the porewater chemistry resembled the control site. Compared to the control site, the methane oxidation and sulphate reduction rates were elevated at the pockmark site, reaching maximum values of 49 and 269 μmol l–1 d–1 respectively. The groundwater venting from the pockmark had an end member composition of 80 mM Na+, 1.0 mM Ca++ and was depleted in Mg++. Due to mixing of these major cations along the groundwater/seawater interface, no CaCO3 precipitation was found around the pockmark site.