Location of Stonehaven monitoring site Stonehaven Monitoring site Why are coccolithophores important? Seasonal variation of Emiliania huxleyi morphology at an ecosystem monitoring site off the east coast of Scotland Pablo Leon Diaz, Eileen Bresnan and Pam Walsham Marine Laboratory, 375 Victoria Road, Aberdeen, AB11 9DB, U.K. Methods – SEM analysis Marine Scotland Science has been operating a coastal ecosystem monitoring site at Stonehaven (lat N/long. 2.10W) since Samples are collected weekly 5 km offshore to record temperature, salinity, nutrients, phytoplankton and zooplankton. Total Alkalinity (TA) and Dissolved Organic Carbon (DIC) are also measured since 2009 to generate data on OA in Scottish waters (see poster by Walsham et al., E-poster session 1). Since 2010 additional samples have been collected to investigate the diversity of coccolithophores in the region. Sea water samples for the analysis of coccolithophores were preserved using a formalin-hexamine solution and stored in dark conditions until analysis using Scanning Electron Microscopy (SEM). Between 5 and 10 ml of samples were filtered through a 0.1 µm filter, rinsed to remove salt and then air dried. Filters were splutter coated with gold and examined with a Zeiss EVO MAIO SEM (Institute of Medical Sciences, University of Aberdeen). Coccolithophore cells were enumerated and classified according to Young et al. (2003*). Emiliania huxleyi coccospheres and coccoliths were measured from SEM micrographs using Fiji (ImageJ) image processing package and categorized into morphotypes. Coccolithopore cell Coccolith structure Coccoliths Distal shield Central area *Young, J. R., Geisen, M., Cros, L., Kleijne, A., Sprengel, C., Probert, I. and Ostergaard, J A guide to extant coccolithophore taxonomy. J. Nannoplankton Res. Spec. Issue 1:1–125. Coccolithophores are an important component of the phytoplankton community and are the focus of many studies about the effects of Ocean Acidification (OA). Laboratory research has shown contradictory results about the impacts of OA on the calcification of coccolithophore plates and field studies are scarce. In this study the diversity and seasonality of coccolithophores are investigated at the Stonehaven coastal monitoring site for the first time. ZEISS EVO MAIO SEM used in the study

Seasonal variation of Emiliania huxleyi morphology at an ecosystem monitoring site off the east coast of Scotland Pablo Leon Diaz, Eileen Bresnan and Pam Walsham Marine Laboratory, 375 Victoria Road, Aberdeen, AB11 9DB, U.K. Coccolithophore diversity Analysis of water samples collected between June 2010 and December 2013 reveals six coccolithophore species present at the Stonehaven monitoring site. Emiliania huxleyi Coronosphaera mediterranea Syracosphaera corolla Helicosphaera carteri HOL perforate Syracosphaera spp. Coccolithus pelagicus Braarudii spp. A seasonal cycle in coccolithophore abundance was observed, with increased abundance during summer and early autumn and very low cell densities in winter. E. huxleyi was the dominant specie throughout the year. The other species/genera were mainly observed in the early summer. No coccolithophores were observed in April.

Emiliania huxleyi morphotypes Seasonal variation of Emiliania huxleyi morphology at an ecosystem monitoring site off the east coast of Scotland Pablo Leon Diaz, Eileen Bresnan and Pam Walsham Marine Laboratory, 375 Victoria Road, Aberdeen, AB11 9DB, U.K. The authors would like to thank Kevin Mackenzie, Debbie Wilkinson and Lucy Wight from the Microscopy Unit, IMS, University of Aberdeen for their assistance with the SEM analysis as well as all involved in the sampling team at the Stonehaven ecosystem monitoring site. This work is funded by the Scottish Government Service Level Agreement ST03p. The morphological analysis of E. huxleyi cells indicate the presence of three different morphotypes at the region: i) Type A, small coccospheres with moderate-heavily elements and a grilled central area; ii) Type A Overcalcified, small coccospheres with heavily elements and almost closed central area; iii) Type B: larger coccospheres with lightly calcified elements. A seasonal variability was observed in the E. huxleyi morphotypes, with a transition in dominance from less to more heavily calcified forms between spring and early winter. Type A was the dominant morphotype observed. Acknowledgments Emiliania huxleyi (Type A) Grilled central area Emiliania huxleyi (Type B) Solid non-grilled central area Emiliania huxleyi (Type A overcalcified) Increased calcification Type A Overcalcified Type B This study presents the first records of coccolithophore diversity at the Stonehaven monitoring site. As the time series extends, data collected will show if variation in the abundance of these dominant morphotypes is driven by seasonality or influenced by larger scale environmental change such as climate change or OA.