Leibniz-Institut für Ostseeforschung, Warnemünde
(IOW) (Baltic Sea Research Institute, Warnemünde)
The results of the weekly sampling at the sea bridge Heiligendamm (54°08,55' N; 11°50,60' E,
300 m off shore, 3 m water depth), performed by the Baltic Sea
Research Institute Warnemünde (IOW) are shown in
Figure 1. The line reflects the chlorophyll a concentration and the columns the phytoplankton wet weight.
The phytoplankton biomass was determined by microscopic counting (Utermöhl method) and the chlorophyll a
concentration (corrected for phaeopigment) by ethanolic extraction and fluorometric measurement according to the
Starting with the sample from 27.9.2006, a new phytoplankton counting program "PhytoWin" was applied. Before,
the DOS-version "PHYTO" was used, which was based on an internal
IOW list of phytoplankton biovolumes. The PhytoWin is
based (since March 2006) on the official HELCOM list (Olenina et al. 2006).
The phytoplankton samples from 31.1.2006 (=week 5), 30.5.2006 (=week 22), 8.8.2006 (=week 32) and 5.9.2006
(=week 36) could not be analysed because of high content of resuspended sediments owing to strong wind. No sampling was
possible on 11.7.2006 (=week 28) because of the visit of US-president George W. Bush in Heiligendamm. No chlorophyll
data are available from 9.5. to 30.6.2006 as samples were spoiled by impure extraction agent. On 10.10.2006 (week 41) and
since 30.10.2006, the sea bridge Heiligendamm was barred because of reconstruction.
As expected, phytoplankton biomass was low at the beginning of the year.
Beside the typical cryptophyceae (Teleaulax sp., Plagioselmis prolonga, Hemiselmis sp.), the autumn
dinoflagellate Ceratium tripos and the spring diatom Thalassiosira anguste-lineata were abundant on
17.1.2006. By the 7.2.2006 (week 6), Actinocyclus sp. developed a biomass of 284 mg/m3. This species
declined strongly for the benefit of other diatoms (Porosira glacialis, Rhizosolenia setigera,
Thalassiosira nordenskioeldii, Skeletonema "costatum") already one week later. Porosira glacialis
continued growing to 236 mg/m3 on 21.2.06 (week 8), while Rhizosolenia setigera, which was dominating in 2005, decreased.
Porosira glacialis accounted for the main part of the early stage of the spring bloom, with
413 mg/m³ on 7.3.2006 (week 10). Also Skeletonema
grew strongly to 191 mg/m³. By use of the common identification books,
Skeletonema was traditionally identified as Skeletonema costatum. The taxonomic work by Sarno et al. (2005)
showed that also other species have to be taken into consideration. Electron microscopic analyses on the sample from 7.3.2006
revealed that the Skeletonema species in the investigated waters should be Skeletonema marinoi. This species grew to
415 mg/m³ by 14.3.2006. On 21.3.2006 (week 12), Skeletonema marinoi,
Porosira glacialis, Chaetoceros similis and Chaetoceros wighamii formed the bloom to almost equal shares.
During the diatom bloom, water temperatures were below 1 °C (except for
week 8 - 9).
The diatom bloom decreased by the 28.3.2006 (week 13), while the water temperature increased
continuously (to 2.8 °C in week 13, continuing to 7 °C
in week 18). From the diatoms, primarily Skeletonema marinoi (107 mg/m³)
and Rhizosolenia setigera (50 mg/m³) remained.
Now, Dictyocha speculum and athecate dinoflagellates developed, by the 4.4.2006 also Apedinella radians
and Mesodinium rubrum. The absolute maximum of the bloom was reached on 11.4.2006, established by the naked form
of Dictyocha speculum (3350 mg/m³). This species was counted as
Chrysophycee in Figure 1, but forms an own class according to the latest taxonomy.
On 25.4.2006 (week 17), the prymnesiophycee Chrysochromulina sp. developed. It nourished heterotrophically
(or mixotrophically) as indicated by individuals which had particles on its haptonema. Chrysochromulina sp. decreased with the
general phytoplankton biomass decrease in May. The mixotrophic cryptophyceae Plagioselmis prolonga, Teleaulax sp.
took benefit from this situation.
At the beginning of June, phytoplankton biomass recovered from the previously registered minimum, especially due to
growth of unidentified dinoflagellates. Also prymnesiophytes (probably Chrysochromulina spp.) were frequent
on 6.6.2006 (week 23); however, due to difficult identification, they were put to "Others" in Figure 1. On 13.6.2006,
the heterotrophic flagellate Katablepharis sp. dominated, but due to its obligatory heterotrophic mode of nutrition it was not
included in Figure 1. The 20.6. (week 25) resembled the 6.6.2006. The naked form of Dictyocha speculum, which formed a
bloom already in April, showed up again (68 mg/m³) on 4.7.2006 (week 27),
while Ceratium tripos appeared with 54 mg/m³. A bloom of
Anabaena sp. (715 mg/m³) has grown by the
18.7.2006 (week 29), and Ceratium tripos has increased to
97 mg/m³. A species shift within the nitrogen-fixing cyanobacteria from
Anabaena sp. to Nodularia spumigena (347 mg/m³) and
Aphanizomenon sp. (93 mg/m³) occurred in week 30. This bloom,
dominated by Nodularia spumigena, persisted at least until 1.8.2006. The cyanobacteria bloom was especially strong
this year, with high local variability. On some occasions in August 2006 (11.8., 17.8.), bathing was forbidden at some places in
northwest-Mecklenburg. Strong blooms occurred in front of Warnemünde from 14. - 17.8.2006 and around the 28.8.2006.
The intensity was obviously lower in front of Heiligendamm on the sampling days in August.
On 15.8.2006 (week 33), Ceratium tripos (162 mg/m³) and
Plagioselmis prolonga (137 mg/m³) dominated. A short occurrence of
Coscinodiscus granii (159 mg/m³) on 22.8.2006 may indicate outflow of
Baltic water. The summer peak of phytoplankton biomass was reached on 29.8.2006 with
1732 mg/m³. It was strongly dominated by unidentified algae of a size
<5 µm (9.5 million cells/ m³
<2 µm; 4.2 million cells/ m³ of
2 - 5 µm size).
The species composition changed again by the 12.9.2006 (week 37). Dinoflagellates dominated:
Ceratium fusus (992 mg/m³), Ceratium tripos
(400 mg/m³). But also diatoms have developed: Coscinodiscus granii
(195 mg/m³), Proboscia alata
(91 mg/m³), Cerataulina pelagica
(65 mg/m³), Chaetoceros curvisetus
(21 mg/m³). On 19.9.2006 (week 38),
Ceratium tripos (518 mg/m³),
Cerataulina pelagica (207 mg/m³),
Ceratium fusus (87 mg/m³) and
Prorocentrum micans (70 mg/m³) were the most
Starting with week 39, a new biomass list was applied, as stated above. We could argue that this change could have
caused the strong decline in biomass. But also the abundances, which are not influenced by this methodological
change, decreased strongly from 4,6 million/L on 19.9.2006 to 0,8 million/L on 27.9.2006.
This is also supported by the decline in chlorophyll a concentrations. Ceratium and have disappeared almost
completely, and cryptophyceae (Teleaulax spp., Plagioselmis prolonga) became dominant. On 4.10.2006 (=week 40),
Ceratium tripos (46 mg/m³) and Coscinodiscus granii
(33 mg/m³) were the most important species. The shifts in the ratio of
Ceratium tripos and Coscinodiscus granii may be caused by the drift of the water bodies. Inflowing water from
the Belt Sea supports Ceratium tripos
(e.g. 103 mg/m³ on 16.10.2006),
while outflowing Baltic water transports Coscinodiscus granii to the sampling station
(e.g. 110 mg/m³ on 23.10.2006).
1. 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.
2. Sarno, D., Kooistra, W.H.C.F., Medlin, L., Percopo, I., Zingone, A., 2005. Diversity in the genus Skeletonema (Bacillariophyceae). II. An assessment of the taxonomy of S. costatum-like species with the description of four new species. J. Phycol. , 41, 151-176.
Figure 1: Chlorophyll a concentration and composition of phytoplankton biomass (wet weight) from 3.1. to 23.10.2006 at the coastal station Heiligendamm (surface water).