Bulletin of the Sea Fisheries Institute 2 (153) 2001 - CEEMaR

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10 m 40m Main phytoplankton assemblages ... 33 55.0° Gdañsk Deep 137 G2 5 100m 54.5° Gdynia 127 129 124 70 Gdañsk 125 71 112 79 63 64 57 Dead Vistula R. 157 66 65 111 74 60 88 52 54 81 52a P114 Gulf of Gdañsk 45 Vistula R. 48 42 85 40 37 36 97 86 80m 25 60m 115 117 20m Vistula Lagoon 10m 18.5° 19.0° 19.5° 20.0° Fig. 1. Location of sampling stations in the Gulf of Gdañsk 54.8° 67 10 63 20 m 4 61 58 54.3° 53 55 49 47 10 m Odra Bank 13 12 1 19 6 10 m Peene 35 41 33 31 27 25 18 16 Dziwna 38 29 Œwina Szczecin Lagoon 53.8° 13.5° 14.0° 14.5° 15.0° 15.5° ig. 2. Location of sampling stations in the Pomeranian Bay
34 S£AWOMIRA GROMISZ AND ZBIGNIEW WITEK served with Lugol’s solution (Edler 1979) and then analyzed using an inverted microscope (Utermöhl 1958). This work does not consider the composition and biovolume of heterotrophic dinoflagellates. Autotrophic dinoflagellates were distinguished from the heterotrophic ones using chlorophyll autofluorescence excited with blue light. Thus, a separate water portion was preserved with alkaline Lugol’s solution, a 3% Na 2 S 2 O 3 solution and alkaline formaldehyde and then frozen (Sherr and Sherr 1993). After slowly defrosting the sample in the laboratory, cell autofluorescence was observed under an Olympus IMT-2 inverted microscope with an IMT 2 RL epifluorescent attachment. The abundance was estimated for each species or higher systematic unit (whenever species identification was impossible), and with the aid of the geometric method the average cell volume was also assessed. Using these data, the biovolume of each taxon was determined for each sample. The value of the PIE (probability of interspecific encounters) diversity index was also estimated for each station. In the original version, this index describes the probability of two randomly seen individuals belonging to different species (Lampert and Sommer 1996), and it is calculated using the abundance of each taxa. In this work, abundance was replaced by biovolume and species diversity was calculated as follows: PIE = B/(B + 1)(1 – Σp i 2 ), where: B – total phytoplankton biovolume; p i – contribution of species i in total phytoplankton biovolume. The similarity of taxonomic composition in samples was evaluated by analyzing assemblages using the PRIMER program. The analysis was based on each taxon’s percentage of the phytoplankton biovolume and was carried out in accordance with the Bray-Curtis similarity coefficient, which is defined as follows: S jk ⎡ ⎢ = 100 ⎢1 − ⎢ ⎣ p ∑ i= 1 p ∑ i= 1 yij − yik ⎤ ⎥ ⎥ ( yij + yik ) ⎥ ⎦ where: y ij – percentage of the biovolume of species i in sample j; y ik – percentage of the biovolume of species i in sample k. In order to increase the significance of rare species in the phytoplankton biovolume, logarithmic data transformation (log(1+y)) was done before calculating the similarity. In order to present the results of clustering analysis in graphic form, hierarchical agglomerative clustering was used, in which the similarity matrix was sorted according to group-average linkage strategy. The result of the hierarchical clusterings are presented in the form of dendrograms, with the x axis representing the full set of samples and the y axis defining the similarity level at which two samples or group are considered to have fused (Clarke and Warwick 1994). This work also used hydrological data which were collected using a CTD Niels Brown probe, data on chlorophyll concentrations (Ochocki et al. 1995b, Ochocki et al. 1999, Renk et al. 2000) and hydrochemical data. Chemical analyses were carried out using the standard-
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Page 67: WSKAZÓWKI DLA AUTORÓW INFORMACJE

Bulletin of the Sea Fisheries Institute 2 (153) 2001 - CEEMaR

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