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Cell densities of Parmales (a group of siliceous marine phytoplankton) were determined in 81 water samples from depths of 0–60 m on a monthly basis from October 2009 and October 2010 in Mag...

We analysed the morphology of Emiliania huxleyi from globally distributed plankton samples and demonstrate that the size of E. huxleyi placoliths is highly correlated to in-situ sea surface water salinity. We used multiple linear regression analysis to link morphological parameters of E. huxleyi to in-situ salinity and in-situ temperature. The best multiple regression model yielded an R 2 = 0.84 with a standard residual error of 0.65 for in-situ salinity over a gradient from 32.6 to 38.8. No significant correlation existed with temperature. Our results suggest that the morphology of E. huxleyi placoliths of recent and ancient sediments may provide a robust method to reconstruct sea surface salinities. One caveat is that the plankton-derived multiple regression model for in-situ salinities is different from that reported from previous work on Holocene sediments. This discrepancy is most likely caused by taphonomic processes or from the biogeographically biased data sets which were used (open ocean versus near shore). The cause of the tight relation between salinity and morphological response is not well understood but may be related to cell turgor regulation that affects the size of the cell and thus the size of a single coccolith.

J. BOLLMANN, M.Y. CORTES ,A. K LEIJNE, J.B. O STERGAARD ANDJ.R. YOUNG. 2006. Solisphaera gen. nov. (Prymnesiophyceae), a new coccolithophore genus from the lower photic zone. Phycologia 45: 465-477. DOI: 10.2216/05-14.1 Solisphaera gen. nov. (Prymnesiophyceae) is described from the lower photic zone of the Pacific Ocean, the North Atlantic Ocean and the Gulf of Mexico. Differences in coccolith morphology between Solisphaera and members of Rhabdosphaer- aceae are certainly substantial enough to warrant the erection of a separate genus that should probably be categorised as incertae sedis aff. Rhabdosphaeraceae. The new genus accommodates three new species, S. emidasia sp. nov., S. blagna- censis sp. nov. and S. helianthiformis sp. nov. and the presence of a corona of process-bearing coccoliths around the cell is a key feature that unites the three species in the new genus Solisphaera, while the shape of these coronal coccoliths provides the main character for separating them at species level. A remarkable feature of this genus is the tight interlocking of the coronal coccoliths, in almost all collapsed coccospheres the circle of coronal coccoliths remains intact. This is evidently due to the presence of notches at the base of the process into which the rims of adjacent coccoliths lock. All three species are restricted to the lower photic zone in the areas studied and apparent preferences for different depth levels of S. emidasia and S. blagnacensis, as well as their nutrient and light requirements, have to be confirmed by further analysis.

This paper discusses the techniques used to sample and analyse living marine calcareous phytoplankton. The various methods are described and tested within several research projects aimed at the determination of coccolithophore cell densities in seawater. In addition, the potential advantages and drawbacks associated with the application of light and scanning electron microscopic techniques to the quantitative analysis of coccolithophores are discussed. Several tests have been carried out in order to quantify potential errors related to: (1) homogeneity of material distribution on filter membranes; (2) use of different microscopes (scanning electron microscope versus light microscope); (3) use of different filter membranes (cellulose mixed-ester membranes versus polycarbonate membranes); and (4) Utermohl settling versus filtration method. These tests revealed that major errors in cell density calculations could result from the uneven distribution of coccolithophore specimens on a filter membrane. The error resulting from the use of a light microscope arises from its low resolution, which restricts the identification of species, especially of small coccospheres. The use of different filter membranes does not show a statistically significant difference in cell density calculations, although polycarbonate membranes can be examined much more efficiently with the scanning electron microscopy than cellulose mixed-ester membranes. The Utermohl method, however, gives lower cell densities consistently (several times) than the filtration method.

This is the first description of a combination coccosphere of the heterococcolithophore species Coronosphaera mediterranea (Lohmann 1902) Gaarder in Gaarder & Heimdal (1977) and the holococcolithophore species Calyptrolithophora hasleana (Gaarder 1962) Heimdal in Heimdal & Gaarder (1980) (Figs 1, 2). A single specimen of this new combination coccosphere was found within 53000 analysed cells in one of 189 samples collected at the JGOFS time series station ALOHA, Hawaii, during 1993 to 1996. The specimen was in a sample collected during autumn 1996 at a water depth of 5 m at a temperature of 26·1 °C, salinity of 35·0 psu, phosphate of 0·002 μmol/kg and in nitrate-depleted water (for details see Cortes, 1998; Cortes et al., 2001).