The diatom Mediopyxis helysia Kühn, Hargreaves & Halliger 2006 at Helgoland Roads: a success story?

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 l ¡1, it was one of the dominant diatoms in the 2010 spring bloom with Mediopyxis reaching cell densities above 300,000 cells l ¡1 and total chlorophyll concentrations exceeding 40 g l ¡1 . 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 12°C. 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 of 31.5. 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.

The Continuous Plankton Recorder survey: How can long-term phytoplankton datasets contribute to the assessment of Good Environmental Status?

“…Over the course of the survey, several phytoplankton taxa have been discovered in areas where they were previously absentMediopyxis spp. (Kraberg et al, 2012), Coscinodiscus wailesii (Boalch and Harbour, 1977;Edwards et al, 2001a), and Neodenticula seminae (Reid et al, 2007). For a number of these taxa, vectors of introduction (e.g.…”

An updated phytoplankton check-list for the Helgoland Roads time series station with eleven new records of diatoms and dinoflagellates

“…This is a large bipolar centric diatom species (apical diameter up to 100 µm first recorded from the Gulf of Maine and the island of Sylt, see also [19]). It was first recorded at the Helgoland Roads site in March 2009 [20]. The species has characteristic star-shaped chloroplasts and the valve outline, which has one rounded and one pointed valve apex, is also diagnostic.…”

“…An earlier study reported that this species was first observed in 2003 [21], but it was not observed during the routine phytoplankton counts on Lugol samples, and did not appear in the 2004 check-list. Mediopyxis helysia formed extensive blooms in Helgoland Roads in 2010 (and also in the Dutch Wadden Sea [22], but appears to be restricted to quite specific environmental conditions occurring predominantly during periods with reduced salinities [20] and its numeric importance appears to be diminishing again at least at Helgoland Roads.…”

Emission of iodine-containing volatiles by selected microalgae species

“…These media were prepared from filtered natural seawater from the shores of Sylt and additional nutrients which the diatoms need to grow (0.88 mmol NO 3 ) and which is a common used medium as described by Guillard et al (1975) and Kraberg et al (2012). Both cultures were incubated in the F/2 medium at 16 • C with 12 h light-12 h dark cycling (LUMILUX Plus Eco daylight lamp; ca.…”