Monitoring ofDinophysisspecies and diarrhetic shellfish toxins in Flødevigen Bay, Norway: inter-annual variability over a 25-year time-series

Abstract

The accumulation of phycotoxins in bivalve mussels associated with mussels feeding on toxic phytoplankton is a well-known phenomenon in Norway. Regular monitoring for 25 years has revealed that accumulation of Diarrhetic Shellfish poisoning (DSP) toxins in mussels is the main phycotoxin problem along the Norwegian coast. The aim of this study was to evaluate possible trends over time of Dinophysis spp. and DSP as well as possible correlation between abundance of Dinophysis spp. and toxin accumulation in mussels, as based on intensive and regular monitoring at the southern coast of Norway at Flødevigen Bay. The main source organism causing a risk of DSP in Norway is Dinophysis acuta. However, it cannot be excluded that other Dinophysis spp., e.g. D. acuminata and D. norvegica, may contribute to the total accumulation of toxins. The variability in the occurrence of these species is high at both short- and long-term; between days and between years. There are, however, some important overall patterns in the occurrence of the species during the last decades. Dinophysis acuminata and D. norvegica have mainly been abundant from March to December, whereas D. acuta has typically occurred in late summer and autumn (August-December). For all three species we have observed a narrowing of the peak season since 2002 at the same time as they have become less abundant. Coincident with these changes, the problem of the accumulation of DSP toxins in mussels along the southern coast of Norway has declined significantly, but it is still mainly restricted to the autumn. Why the cell concentration of Dinophysis spp. has declined after 2002 is not obvious, but this has occurred in a period with relatively high summer temperatures. The relatively simultaneous changes in physical, chemical and biological factors of the pelagic ecosystem along the southern coast of Norway indicate that complicated ecological interactions may be involved.

Characterization of Dinophysis spp. (Dinophyceae, Dinophysiales) from the mid‐Atlantic region of the United States1

“…Similar shifts in the Dinophysis community were reported along the Norwegian and Sardinian coasts by Naustvoll et al. () and Bazzoni et al. (), respectively, through their analyses of 25‐year time‐series data sets.…”

“…Naustvoll et al. () did not observe a relationship between nutrients and Dinophysis and hypothesized changes in the Dinophysis community may be influenced by shifts in the prey community it relies on. Additionally, dinoflagellate parasites, such as Amoebophrya and Parvilucifera , are known to infect and impact some Dinophysis populations (Park et al.…”

Climate variability and Dinophysis acuta blooms in an upwelling system

“…Belgrano et al (1999) linked abundance of D. acuta in the Skagerrak, western Sweden, to periods of positive values of the NAO, and suggested that large-scale climatic processes govern the interannual variability of D. acuta, ruling out the hypothesis of an increasing trend in recent decades. Naustvoll et al (2012) observed a decrease of D. acuta numbers on the southern Norwegian coast on the basis of a 25-year time series . Concerning Dinophysis spp.…”

“…to environmental conditions, the lack of long-term time series data has hindered progress in understanding the factors controlling their interannual variability. Multidecadal climate oscillations have been proposed to explain long-term variations in Dinophysis blooms in the Skagerrak, in western Swedish (Belgrano et al, 1999) and southern Norwegian coastal waters (Edwards et al, 2006;Naustvoll et al, 2012). These authors suggested that long-term changes of Dinophysis blooms in these areas were related to phase changes of the North Atlantic Oscillation (NAO), the most important mode of low-frequency variability of atmospheric circulation in the northern hemisphere (Hurrell, 1995).…”

Simultaneous detection of three biotoxins causing diarrhetic shellfish poisoning (okadaic acid, dinophysistoxin-1, dinophysistoxin-2) in oyster by LC-MS/MS

“…Therefore, these samples of oyster were still safe for human consume. However, long-term studies have also showed that the contamination of DSP toxins in shellfish at the same location may have significant year-to-year variation and even more significant between multiannual periods 21,32 . So the presence of OA and DTX-2 in oyster, even at very low levels, confirmed the potential risk of DSP outbreak in Vietnam and the necessity of monitoring toxins in shellfish for human consume in general.…”