Ocean Circulation and Climate

5. Foraminifera and environment

: Figure 1. A recent example of foraminiferal species’ response to changing environmental conditions. The benthic Ammotium cassis (Parker 1870) is a Northern Hemisphere cold-water species, which needs high salinities for reproduction (Olsson, 1976). It was frequent in the western Baltic Sea during the 1960s to 1980s and diminished during the last 10 years, most likely induced by a period of low deep-water salinities in the early 1990s (Matthäus, 1990; Nausch et al., 2003; Schönfeld and Numberger, 2007).

Planktonic and benthic foraminifera reveal the state and the dynamics of the surface and deep ocean in the past. These protozoans are less than 1 millimetre in size. They occur in nearly all marine environments, from deep-sea trenches up to the salt marsh meadows. Even in brine channels of Antarctic sea ice they have been found. Many species respond sensitively to certain environmental conditions. Thus, the chemical and isotopic composition of their calcitic shell material records the properties of their ambient sea water. The texts also mirror metabolic and kinetic processes again which played a role in shell formation. Foraminiferen are mostly well-preserved in marine sediments, and they are found in great numbers. Therefore, foraminifera became the most important tool for paleoceanographic reconstructions.

: Figure 2. Ammotium cassis from Eckernförde Bight, Western Baltic Sea, collected at 24 m waterdepth. The 0.9 mm long specimen was living at the time of sampling.

Foraminiferen als Proxies für Bodenströmungen (German)

Foraminiferal taxonomy
Paleo-seasurface temperatures deduced from Mg/Ca in planktonic foraminifers
Benthic foraminifera in moderately polluted environments: a case study from Kiel Bight (SW Baltic Sea)
Effects of elevated pCO2 on living benthic foraminifera
Changing habitats of planktonic foraminifera in the Greenhouse World
Biodiversity of benthic foraminifera in the northeastern Atlantic
Benthic foraminifera in tropical Oxygen Minimum Zones
Marginal marine foraminifera

References:

Matthäus, W. 1990. Langzeittrends und Veränderungen ozeanologischer Parameter während der gegenwärtigen Stagnationsperiode im Tiefenwasser der zentralen Ostsee. Fischerei-Forschung, 28: 25–34.

Nausch, G., Matthäus, W., Feistel, R. 2003. Hydrographical and hydrochemical conditions in the Gotland Deep area between 1992 and 2003. Oceanologia, 45: 557–569.

Olsson, I. 1976. Distribution and ecology of the foraminiferan Ammotium cassis (Parker) and its ecological significance. Zoon, 4: 137–147.

Schönfeld, J., Numberger, L., 2007. Seasonal dynamics and decadal changes of benthic foraminiferal assemblages in the western Baltic Sea (NW Europe). Journal of Micropalaeontology, 26: 47–60.

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