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Coccolithophores are major contributors to phytoplankton communities and ocean biogeochemistry and are strong modulators of the optical field in the sea. New discoveries are changing paradigms about these calcifiers. A new role for silicon in coccolithophore calcification is coupling carbonate and silicon cycles. Phosphorus and iron play key roles in regulating coccolithophore growth. Comparing molecular phylogenies with coccolith morphometrics is forcing the reconciliation of biological and geological observations. Mixotrophy may be a possible life strategy for deep-dwelling species, which has ramifications for biological pump and alkalinity pump paradigms. Climate, ocean temperatures, and pH appear to be affecting coccolithophores in unexpected ways. Global calcification is approximately 1–3% of primary productivity and affects CO2 budgets. New measurements of the backscattering cross section of coccolithophores have improved satellite-based algorithms and their application in case I and case II optical waters. Remote sensing has allowed the detection of basin-scale coccolithophore features in the Southern Ocean.
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Download Supplemental Figures 1-2 as a PDF, or see below.
Supplemental Figure 1.Trends in PIC concentration derived from satellite data (in units of mg PIC m-3 y-1) for (a,c) SeaWiFS (1998–2007), and (b,d) MODIS (2003–2014). Bottom panels show significant trends (p < 0:05). Position of Bermuda Atlantic Time Series (BATS) shown for reference. Adapted from Krumhardt et al (2016).
Supplemental Figure 2. Morphology of coccoliths observed by scanning electron microscopy, shown as the percentage of four categories: normal (black), incomplete (grey), malformed (white) and very malformed (red). (a) Experiments where Coccolithus pelagicus subspecies braarudii and subspecies pelagicus were grown at 10 or 15°C and high or low phosphorous levels and (b) additional experiments of high-P and low-P cultures of Coccolithus pelagicus subsp. braarudii at 15°C and subsp. pelagicus at 10°C. Triplicate batch culture results are presented separately for each experiment. (c) Scanning electron micrograph examples of normal, incomplete, malformed and very malformed coccoliths of Coccolithus pelagicus. Adapted from Gerecht et al. (2014).
Literature Cited
Gerecht AC, Šupraha L, Edvardsen B, Probert I, Henderiks J. 2014. High temperature decreases the PIC / POC ratio and increases phosphorus requirements in Coccolithus pelagicus (Haptophyta). Biogeosciences 11: 3531-45
Krumhardt KM, Lovenduski NS, Freeman NM, Bates NR. 2016. Apparent increase in coccolithophore abundance in the subtropical North Atlantic from 1990 to 2014. Biogeosciences 13: 1163-77 doi:10.5194/bg-13-1163-2016