Unusual phytoplankton events in 2005

	HELCOM Phytoplankton Expert Group Authors: Susanna Hajdu1, Irina Olenina2, Norbert Wasmund3, Lars Edler4, Barbara Witek5

Key Message  

 Strong bioluminescence were observed in several coastal areas in late summer 2005.

Marine species (Cerataulina pelagica, Chaetoceros brevis, Dactyliosolen fragilissimus) penetrated far into the Baltic Proper up to the Lithuanian coast in late autumn. They may indicate warm water inflows that cannot be identified on the basis of salinity measurements.

Relevance of the indicator for describing developments in the environment

As phytoplankton is an important component of the ecosystem, its changes represent changes in the ecosystem. They may be caused by different factors like large inflow of saline or fresh-water, invasion of new species, large import of nutrients or toxic substances (also by accidents), and extreme weather conditions. The reason of unusual phytoplankton events can sometimes not be identified and such sporadic events do hardly allow trend analyses but they communicate, nevertheless, useful information on changes in the environment.

Policy relevance and policy references

Toxic phytoplankton events have high relevance for public health and economy (tourism, fisheries). The Indicator Fact Sheet may not serve for early warning but has importance for long-term documentation of such events. If new species are noticed, this may contribute to the International Convention for the Control and Management of Ships’ Ballast Water and Sediments of the International Maritime Organization (IMO). 

Assessment

During the summer 2005 several bioluminescent events were reported from different parts of the Baltic Sea. In August strong bioluminescence was observed at the Swedish east coast (archipelago of Västervik) and at the east-coast of Gotland (Valleviken). The bloom at Gotland was dominated by the potentially toxic dinoflagellate Alexandrium ostenfeldii (Paulsen) Balech & Tangen 1985, but Heterocapsa triquetra (Ehrenberg) Stein 1883 and cf. Kryptoperidinium foliaceum (Stein) Lindemann were also abundant in the sample.

Alexandrium ostenfeldii is a PSP-producing species, which so far mainly has occupied the Kattegat and the southern Baltic Proper (Wasmund 2002). It was not observed in blooms in the Baltic Sea until 1997, when it caused strong bioluminescent bloom south of the island Öland (Larsson et al. 1998).

The next bloom of this potentially toxic species was reported from the Puck Bay (Gulf of Gdansk), in late August 2001 (Witek 2004). At that time, A. ostenfeldii totally dominated the bloom with abundances up to 0.8 million cells/L. In September 2003, the bloom appeared again in the Puck Bay, but the abundance of A. ostenfeldii was lower (about 0.3 million cells/L). At the Swedish east coast of the northern Baltic Proper, A. ostenfeldii was observed for the first time in 2000 and has been more common in monitoring samples since then (see BIOMAD).The potentially toxic Alexandrium ostenfeldii seems to advance and be able to cause blooms in the Baltic Sea. Hitherto no toxic events, connected with the blooms, have been reported.

Other events of bioluminescence have occurred in the western Baltic Sea: on 27 August 2005 in coastal water of the southern Mecklenburg Bight (Niendorf near Klütz) and on 1 January 2006 on wet sand (surf zone of the beach) in Flensburg Fjord. The causing organisms are not known. Ceratium tripos was the dominating species in Mecklenburg Bight at that time but the bioluminescence in the sand might have been caused by bacteria.

In the beginning of November 2005 a mass development of marine species Cerataulina pelagica, Chaetoceros brevis, Dactyliosolen fragilissimus were observed in the Lithuanian waters with a total density up to 0.5 million cells · l^-1 and a biomass of 3.8 mg· l^-1. These species are known as marine species with brackish-water affinity, which occur in the Kattegat and Öresund, but are almost absent in the Baltic Sea (Snoeijs & Vilbaste 1994, Hällfors, 2004). They have not been observed in the southeastern part of the Baltic before. According to the monitoring data these species have been present in all (20) samples taken in the Lithuanian coastal waters on 3-9 November 2005. The salinity in the area ranged from 6.27 to 7.26 PSU and water temperature from 9.0 to 10.8 ºC. All species were more abundant at nearshore sites, and the highest cell density was found 4 km off the shore at a salinity of 6.55 PSU (Fig. 1). The abundance of these three species reached up to 33 % (16% ± 10%) of the total phytoplankton abundance and up to 82% (59% ± 24%) of the total biomass. Dactyliosolen fragilissimus had the highest abundance (Table 1).

Figure 1. Abundance (cells ·10³  l^-1) of Cerataulina pelagica, Dactyliosolen fragilissimus and Chaetoceros brevis in Lithuanian coastal waters.

Table 1.

The mechanism of penetration of these species from the Kattegat-Öresund area into the Baltic proper is not clear. During the regular monitoring cruise by SMHI in the middle of November Cerataulina pelagica and Pseudo-nitzschia delicatissima group were found at stations BCS III-10 (=BMP K1) and BY38 (=BMP I1) (AlgAware 10, 2005, www.smhi.se). The wide distribution area suggests that the presence of these marine species was not due to ballast water introduction. Between October 20^th and November 15^th there was an inflow of Kattegat water into the Baltic of about 40-50 km³. This water had a low density and may have stayed close to the surface long enough to reach far into the Baltic. Also the measurements of the IOW on Darss Sill noticed a warm water inflow (14 °C, 18 PSU) at the surface (Nausch et al. 2006). Water transport into the Baltic in the surface layer may pass unnoticed in salinity data, but is obviously detectable by the presence of phytoplankton species indicating a certain salinity preference.

References 

AlgAware 10, 2005: http://www.smhi.se/

BIOMAD http://www2.ecology.su.se/dbbm/index.shtml

Hällfors, G. 2004. Checklist of the Baltic Sea Phytoplankton Species. Baltic Sea Environment Proceedings, No. 95. HELCOM, 208 pp.

Larsson, U., Hajdu, S., Andersson, L., Edler, L. 1998. The free water mass. In: The Baltic Sea ’97, Report on Environmental Monitoring, SMF Stock­holm University, Stockholm. pp. 28-33 (In Swedish with English summary and legends, http://www.smf.su.se)

Nausch, G., Feistel, R., Lass, H.U., Nagel, K., Siegel, H.,2006: Hydrographisch-chemische Zustandseinschätzung der Ostsee 2005. Meereswiss. Ber., Warnemünde, 66, 1-82.

Snoeijs, P. & Vilbaste, S. (eds.). 1994. Intercalibration and distribution of diatom species in the Baltic Sea. Vol. 2. 125 pp.

Wasmund, N. 2002. Harmful algal blooms in coastal waters of the south-eastern Baltic Sea. In: Schernewski, G. and Schiewer U. (eds.): Baltic coastal ecosystems. CEEDES-Series. Springer. Berlin, Heidelberg, New York. pp. 93-116.

Witek B. 2004. Blooms of potential toxic dinoflagellates Prorocentrum minimum (Pavillard) and Schiller and Alexandrium ostenfeldii (Paulsen) Balech Tangen in the Gulf of Gdańsk, Ogólnopolska Konferencja Naukowa "Zakwity wody-monitoring i kontrola zagrożeń", Gdynia 20-22 kwietnia 2004 (Conference abstract).

Data

Swedish national monitoring data (BIOMAD http://www2.ecology.su.se/dbbm/index.shtml, AlgAware 10, 2005, www.smhi.se) and data from samples collected from bioluminescent water.

Lithuanian national monitoring data.

Observation of bioluminescence by the public.

Quality information

Information based partly on national monitoring samples, collected from different blooms in 2005, with the whole Baltic Sea being considered. Phytoplankton samples were analyzed and identified by phytoplankton experts, using the mandatory HELCOM methods.

¹Department of Systems Ecology, Marine and Brackish Water Ecology, Stockholm University, SE-106 91 Stockholm, Sweden.

² Centre of Marine Research,Taikos str 26, LT-91149, Klaipeda, Lithuania

³ Baltic Sea Research Institute, Seestr. 15, D-18119 Warnemünde, Germany

⁴ SMHI, Oceanographic Services, Doktorsgatan 9 D, SE-262 52 Ängelholm, Sweden

⁵ University of Gdansk, Institute of Oceanography, Departement of Marine Biology and Ecology, PL-81-378 Pilsudskiego 46, Gdynia, Poland

For reference purposes, please cite this indicator fact sheet as follows:

[Author’s name(s)], [Year]. [Indicator Fact Sheet title]. HELCOM Indicator Fact Sheets 2006. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.
 

Last updated 17.8.2006.