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Helgol Mar Res (2012) 66:463468 DOI 10.1007/s10152-011-0277-9
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The diatom Mediopyxis helysia Khn, Hargreaves & Halliger 2006 at Helgoland Roads: a success story?
Alexandra C. Kraberg Kristine Carstens
Silvia Peters Katharina Tilly Karen H. Wiltshire
Received: 10 January 2011 / Revised: 6 September 2011 / Accepted: 8 September 2011 / Published online: 28 September 2011 Springer-Verlag and AWI 2011
Abstract The Helgoland Roads phytoplankton long-term data set is one of the longest and the most detailed data sets in Europe, having provided continuous work-daily observations of phytoplankton abundance since 1962. These high frequency counts have undergone and are continuously subject to a high level of quality control. The Helgoland data set thus is useful in the evaluation of new records in phyto- and zooplankton. Here, we report the Wrst appearance of the relatively recently described diatom Mediopyxis helysia in the Helgoland Roads counts. This species was
Wrst detected in Helgoland samples in March 2009. Importantly, it has rapidly become a prominent member of the Helgoland phytoplankton community. While in 2009 it only produced a moderate spring peak of 4,000 cells l1, it was one of the dominant diatoms in the 2010 spring bloom with Mediopyxis reaching cell densities above 300,000 cells l1 and total chlorophyll concentrations exceeding 40 [afii9839]g l1. In 2010, this species was repeatedly present throughout the year. There was no clear relationship between temperature and cell abundance with all Mediopyxis cells occurring at temperatures between 3 and 12C. However, the extensive peak in 2010 was associated with a sudden drop in salinity, which could indicate that this
bloom might have been the result of inXow of low salinity water into the area. This was supported by a laboratory growth experiment in which a clonal culture of M. helysia grew fastest at a salinity of 27 and slowest at a salinity of31.5. Further long-term observations will be required to establish whether this species will become a regular feature at Helgoland and how this might aVect the local food web.
Keywords Helgoland Roads Mediopyxis helysia
Long-term trends North Sea Nutrients Salinity
Introduction
The Helgoland Roads long-term phytoplankton data set is one of the longest and most detailed in Europe, as it is based on work-daily counts since 1962. It has also undergone a...