The full chronology with the CRS model, the 210 Pb and the 137 Cs data has previously been published (Reuss et al., 2005).
Parsons and Dortch (2002) documented a correlation between increased nutrient loading in the Gulf of Mexico since the 1950s and an increased abundance of Pseudo-nitzschia .The core was correlated with MF8 and another core from the same location and day using diatom stratigraphy as easily discernable changes occurred in the diatom assemblages (Ellegaard et al., 2006).A supplementary sample from another core was included in the study. delicatissima appeared in smaller percentages ( ABSTRACT: Seasonal variation of DA in bivalves was monitored from August 2008 to March 2009 at a shellfish station in Bizerte Lagoon, one of the most important shellfish areas in Tunisia.Similarly, Stabell and Hasle (1996) found preserved Pseudo-nitzschia valves in sediment from the 1960s.But so far preservation of Pseudo-nitzschia cells in sediments older than 100 years has not been documented.
Dating 40 Mariagerfjord
The whole marine sediment sequence covered the last 9100 years. Diatom samples from the cores MF8 and MF9 were prepared for light microscope analysis following Renberg (1990). americana , increased in abundance after 1983 and had a major peak in 1997 where it made up more than 65% of the Pseudo-nitzschia species. americana was first recorded in the sediment record at ca. americana continued to make up a relatively large contribution to the Pseudo-nitzschia species present. During the study period, domoic acid (DA) was detected in Tunisia, in both mussels (Mytilus galloprovincialis: 0.13-0.86μg DA g-1 tissue) and oysters (Ostrea edulis: 0.42-1.04μg DA g-1 tissue). multiseries are also recorded at the Helgoland Roads time-series site for the first time.Samples of between 0.1 and 0.3 g well mixed wet sediment were weighed into test tubes and digested by 30% hydrogen peroxide (H 2 O 2 ) in a water bath at 87 8 C. seriata increased in relative abundance around 1970 and showed an increasing trend after 1983 (Fig. The amount of DA in the two species was below the EU guideline limits for shellfish (20μg DA g-1). This study represents the first examination of the seasonality of Pseudo-nitzschia species around Helgoland and the first comparison between two long-term monitoring sites in the North Sea. The expenses associated with the long-term field studies needed to document changes in species composition using plankton monitoring have unfortunately restricted the number of studies on occurrence of Pseudo-nitzschia in the field. Such studies are, however, required to determine which factors govern the development of blooms (Trainer et al., 2002).Therefore only a few studies on sediment cores report the presence of (unidentified) Pseudo-nitzschia species (Stabell and Hasle, 1996; Abrantes et al., 2007), whereas others did not find Pseudo-nitzschia species in sediments (e.g.