Leibniz-Institut für Ostseeforschung, Warnemünde
(IOW) (Baltic Sea Research Institute, Warnemünde)
(Dr. Norbert Wasmund, Susanne Busch, Ina Topp, Regina Hansen)
The Leibniz Institute for Baltic Sea Research conducts a coastal monitoring programme with weekly samplings at the sea-bridge Heiligendamm (54°08,55''N; 11°50,60'E; 300 m off shore, 3 m water depth). The Department of Marine Biology analyses the surface samples, taken by means of a bucket, for phytoplankton composition and biomass and for chlorophyll a.
The phytoplankton biomass is determined by microscopical counting (UTERMÖHL method) and the chlorophyll a concentration by ethanol extraction and fluorometric measurement. Method instructions see(http://www.helcom.fi/groups/monas/CombineManual/AnnexesC/en_GB/).
Phytoplankton counting was carried through by use of the counting programme OrgaCount and is based on the HELCOM-biovolume factors which are annually updated: http://www.ices.dk/env/repfor/index.asp (basics see in Olenina et al. 2006). The analytical specifics of the chlorophyll a determination are published by Wasmund et al. (2006). According to the decision of
the BLMP-subgroup "Quality Assurance" from 11.9.2008 we show here chlorophyll a data which are not corrected for pheopigments.
Sampling wasn’t carried through on 8.8.2011.
The results are shown in Figure 1 by continuation of the earlier data from the beginning of 2011.
After the conspicuous phytoplankton spring bloom which was discussed in the last report, biomass and chlorophyll a concentrations were low in summer (until 30.8.2011, =week 35). The reported period starts on 3.5.2011 (week 18), when Chrysochromulina spp. (Image 1) and unidentified Gymnodiniales (Image 2) dominated. Gymnodiniales tend to increase until 24.5.2011 (week 21). Afterwards they disappeared,
but Cryptophyceae (Plagioselmis, Hemiselmis, Teleaulax) grew slightly and by week 23 also Chrysochromulina spp.
Image 1: Chrysochromulina sp.
Image 2: Gymnodiniales
Since 14.6.2011 (Week 24), Cyanobacteria appeared: Aphanocapsa sp., Snowella sp., Pseudanabaena limnetica, Aphanothece sp., Aphanizomenon sp. The phytoplankton kept a high diversity throughout the summer. For example on 12.7.2011 (Week 28), besides the above mentioned Chrysochromulina spp. and Gymnodiniales, also the dinoflagellate Alexandrium protogonyaulax (58 mg/m³,
Image 3) and the Cyanobacterium Aphanizomenon sp. (49 mg/m³, Image 4) became important.
Image 3: Alexandrium protogonyaulax
Image 4: Aggregate of filaments of Aphanizomenon sp.
On 19.7.2011, the Cyanobakterium Nodularia spumigena became present. On 1.8.2011, Prorocentrum minimum was dominant with 58 mg/m³. By the16.8.2011 (week 33), Cyanobacteria disappeared and the dinoflagellate Ceratium tripos appeared.
On 23.8.2011 (Week 34), a strong diatom development started with the growth of Cerataulina pelagica (Image 5) and Dactyliosolen fragilissimus (Image 6).
Biomass on 30.8.2011 is strongly underestimated because of wind-induced resuspension of sedimented particles which made the quantitative microscopical analysis improper.
On 6.9.2011, Cerataulina pelagica was suddenly absent, but Dactyliosolen fragilissimus had developed strongly (1,057 mg/m³). Still stronger was the growth of Pseudosolenia calcar-avis (1,704 mg/m³). The two last-mentioned species stayed the dominating species until 27.9.2011 (week 39).
Image 5: Cerataulina pelagica
Image 6: Dactyliosolen fragilissimus
Cerataulina pelagica developed again, and with lower intensity also the diatoms Proboscia alata, Rhizosolenia pungens, Thalassionema nitzschioides as well as the dinoflagellates Prorocentrum micans and Prorocentrum minimum. The bloom has reached its peak on 20.9.2011 (week 38) with a biomass of 4,937 mg/m³ but was still flourishing at the end of our reporting period. The chlorophyll
samples of that time could not be analysed yet because of a breakdown of the fluorometer.
Olenina, I., Hajdu, S., Andersson, A.,Edler, L., Wasmund, N., Busch, S., Göbel, J., Gromisz, S., Huseby, S., Huttunen, M., Jaanus, A., Kokkonen, P., Ledaine, I., Niemkiewicz, E. (2006): Biovolumes and size-classes of phytoplankton in the Baltic Sea. Baltic Sea Environment Proceedings No.106, 144pp.
Wasmund, N., Topp, I., Schories, D. (2006): Optimising the storage and extraction of chlorophyll samples. Oceanologia 48: 125-144.
All photos taken by Susanne Busch
Figure 1: Composition of the phytoplankton biomass and concentration of chlorophyll a from 4.1. to 27.9.2011 at sea-bridge Heiligendamm.