Spatial distribution of phytoplankton in the eastern part of the North ...

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3.5. Results of statistical analyses3.5.1. Inner structure of dataAn indirect gradient analysis PCA was used to detect the inner structure of the data obtained.The results are given in Tab. 3:**** Summary ****Axes 1 2 3 4 Total varianceEigenvalues : 0.386 0.214 0.123 0.096 1.000Cumulative percentage variance of species data : 38.6 60.0 72.3 81.8Sum of all eigenvalues 1.000Table 3. Part of the PCA analysis output.The two first ordination axes togetherexplained 60 % of the total variability.The positions of the samples in the spaceof these two axes are illustrated in Fig. 16.On the ordination diagram, the samplinglocalities are arranged more or less incorrespondence to their physical orderalong transect, forming the shape of anoverturned letter U. The sampling stationsform three distinct groups in the diagram: Figure 16. Positions of the samples in the space ofthe first two ordination axes. PCA analysis.The group of coastal stations 143, 145,147 and 149; the group of oceanic stations 123, 155 and 157; and the group of two stations 151 and153, situated in the middle part of the transect. Distinct separation of these three groups along thefirst ordination axis reflects to the important role of the distance from the coast for the speciescomposition at each station. However, the uneven arrangement of the stations along the first axisindicates the considerable changes of phytoplankton composition in the areas between stations 149-151 and 153-155.The ratio of species composition of the samples and the orientation of environmental variablesin ordination space are shown in Fig. 17. The association of coastal distance with the first axis iswell shown. Similarly, the second ordination axis dividing the stations 151 and 153 from all other17
ones is linked positively with the depth of seaand negatively with fluorescence. At stations,sited in negative part of second ordinationaxis (stations 123, 157, 143), high values offluorescence were measured. At the samestations, there were also higher numbers ofdiatom species.Figure 17. Positions of the samples and theenvironmental variables in the space of thefirst two ordination axes. PCA analysis. Theratio of the species composition of allsamples is shown (yellow – diatoms, green –dinoflagellates, grey – others).-1.0 1.0coast145149147143151depthfluorescence-1.0 1.0153123temperaturesalinity155abundance1573.5.2. Relationships between phytoplankton and environmental characteristicsThe influence of several environmental characteristics on species composition was statisticallytested using RDA analysis. Separate analyses were made to detect the influence of temperature,salinity, fluorescence, distance from the coast, depth and the total abundance of algae. Interestingly,only the influence of distance from coast proved to be significant, with a p-value of 0.001. All othercharacteristics here found not to be statistically significant for the transect. The results of analysiswith distance from the coast as the tested environmental variable are given in Tab. 4.**** Summary ****Axes 1 2 3 4 Total varianceEigenvalues : 0.343 0.201 0.132 0.090 1.000Species-environment correlations : 0.972 0.000 0.000 0.000Cumulative percentage varianceof species data : 34.3 54.4 67.6 76.6of species-environment relation : 100.0 0.0 0.0 0.0Sum of all eigenvalues 1.000Sum of all canonical eigenvalues 0.343**** Summary of Monte Carlo test ****Test of significance of all canonical axes: Trace = 0.343F-ratio = 3.658P-value = 0.0010Table 4. Part of the RDA analysis output.18
Page 5: getting deeper towards the north. I
Page 10: The values varied between 32.7 and
Page 14 and 15: However, no single Chaetocerosspeci
Page 16 and 17: part of the transect (e.g. P. pyrif
Page 20: The first ordination axis, characte
Page 23 and 24: values of fluorescence but they wer
Page 26: 5. ConclusionsThe data for this sur
Page 29 and 30: REID, F.M.H.; STEWARD, E.; EPPLEY,
Page 32 and 33: Taxon / Number of station Fig. 123
Page 34 and 35: Taxon/number of station 157 153 149
Page 36 and 37: Plate I. Craspedophyceae, Chrysophy
Page 38 and 39: Plate III. Bacillariophyceae 2.1. C
Page 40 and 41: Plate V. Bacillariophyceae 4.1., 2.
Page 42 and 43: Plate VII. Bacillariophyceae 6.1. T
Page 44 and 45: Plate IX. Dinophyceae 2.1.-3. Penta
Page 46 and 47: Plate XI. Dinophyceae 4.1., 2. Prot

Spatial distribution of phytoplankton in the eastern part of the North ...

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