Living coccolithophores in the western Pacific Ocean off Chile
Report of the project:
Coccolithophore sampling on bord of SONNE Cruise SO 161-5 (SPOC)
Source: BGR
Coccolithophores are a major group of marine, unicellular phytoplankton. Their cell surfaces are covered by minute external calcite scales (=coccoliths) which form an important part of fine-grained deep-sea sediments and, therefore, are extensively used in palaeoecological and palaeoceanographical studies (Winter & Siesser, 1994). Because of their optical (albedo - masses of detached coccoliths substantially reflect incoming light) and biochemical (dimethylsulfide - which act as a source molecule for cloud nucleation) effects they likely produce additional feedback to climate change (Westbroek et al., 1993).
There are, however, only limited studies available which deal with the biogeographic occurrence of living coccolithophores in the world oceans. Also, relatively little work has been done on absolute abundances of single species according to ecological parameters in modern communities. This is in contrast to extensive geological studies which have used coccolith assemblage changes as indicators of shifts in paleoceanographic conditions (Gard & Backman, 1990; Baumann & Matthiessen, 1992; Andruleit & Baumann, 1998). The observed distribution patterns of living coccolithophore communities seem to be reflected in bottom sediments rather well (McIntyre & Bé, 1967, Andruleit & Rogalla, 2002) although, a fossil assemblage is not a direct image of the former living community. Therefore, this investigation is done with regard to the spatial and seasonal occurrence of geologically important species, e.g. of Emiliania huxleyi and Gephyrocapsa oceanica. This in turn is essential for a better understanding of the relationship between living communities and accumulated coccolith assemblages in sediments.
At cruise SO 161-5 the focus of research was on the horizontal and vertical sampling of the surface waters of the eastern Pacific Ocean off Chile. At a total of 11 stations (see table below) water samples were taken at several depth intervals with a rosette sampler according to previous CTD profiling. It was aimed to sample the mixed surface water layer, above, at, and below the thermocline and at the bottom of the photic zone. The water (1 to 2 litres) from each depth was filtered without further treatment through filters of 0.45 µm pore width using a vacuum pump and afterwards dried at 50° C for some hours.
Due to the lack of a scanning electron microscope coccolithophore numbers were not investigated on bord. Nevertheless an indication as to whether there are sufficient specimens is related to the staining of the filters. Most filters show a promising staining with an approximate plankton maximum at shallow depths.
| Station No: | Date | Sample depths ( m) | Position | Water depth (m) | |
|---|---|---|---|---|---|
| Latitude | Longitude | ||||
| 9 MS | 29.12.01 | 11, 31, 61, 91, 120, 150 | S 36° 71 | W 73° 48.9 | 2459 |
| 27 MS | 01.01.02 | 11, 27, 41, 51, 82, 122 | S 36° 06 | W 74° 45.02 | 4500 |
| 34 MS | 03.01.02 | 11, 21, 40, 80, 120, 160 | S 37° 11.98 | W 74° 25.26 | 3882 |
| 38 MS | 04.01.02 | 10, 20, 41, 61, 100, 160 | S 38° 48.38 | W 74° 34.31 | 1997 |
| 41 MS | 05.01.02 | 10, 22, 42, 62, 101,142 | S 38° 44,9 | W 74° 01,0 | 450 |
| 44 MS | 05.01.02 | 9, 24, 45, 65, 104 | S 38° 45,0 | W 74° 09,0 | 1281 |
| 58 MS | 08.01.02 | 9, 23, 33, 53, 83, 121 | S 38° 43,0 | W 74° 46,0 | 4520 |
| 96 MS | 18.01.02 | 10, 22, 32, 53, 83, 120 | S 39° 50,0 | W 74° 55,48 | 4247 |
| 99 MS | 18.01.02 | 5, 17, 31, 52, 82, 112 | S 39° 50,54 | W 74° 30,29 | 1590 |
| 108 MS | 20.01.02 | 8, 18, 33, 53, 73, 103 | S 38° 20,45 | W 74° 09,47 | 895 |
| 116 MS | 22.01.02 | 8, 16, 32, 52, 72, 102 | S 36° 39,64 | W 74° 11,29 | 3287 |
Literature:
- Andruleit, H. and Baumann, K.-H. (1998): History of the Last Deglaciation and Holocene in the Nordic Seas as revealed by coccolithophore assemblages. Marine Micropaleontology, 35: 179-201.
- Baumann, K.-H., and Matthiessen, J. (1992). Variations in surface water mass conditions in the Norwegian Sea: Evidence from Holocene coccolith and dinoflagellate cyst assemblages.- Mar. Micropaleontol., 20: 129-146.
- Gard, G, and Backman, J. (1990). Synthesis of Arctic and Sub-Arctic coccolith biochronology and history of North Atlantic drift water influx during the last 500.000 years.- In "Geological history of the polar oceans: Arctic versus Antarctic" (Bleil, U., & Thiede, J., Eds.), Kluwer Academic Publishers, 417-436.
- McIntyre, A. and Bé, A.W.H. (1967). Modern coccolithophoridae of the Atlantic Ocean - I. Placoliths and Cyrtoliths. - Deep-Sea Res., 14: 561-597.
- Westbroek, P., Brown, C. W., van Bleijswijk, J., Brownlee, C., Brummer, G. J., Conte, M., Egge, J., Fernandez, E., Jordan, R., Knappersbusch, M., Stefels, J., Veldhuis, M., van der Wal, P., and Young, J. (1993). A model system approach to biological climate forcing. The example of Emiliania huxleyi. Glob. Planet. Change, 8: 27-46.
- Winter, A., and Siesser, W.G. (1994). Coccolithophores.- Cambridge University Press.