The ecology of the invasive cyanobacterium Cylindrospermopsis raciborskii (Nostocales, Cyanophyta) in two hypereutrophic lakes dominated by Planktothrix agardhii (Oscillatoriales, Cyanophyta)

Figures & data

Fig. 1. Conceptual model of the relationship between Planktothrix agardhii and Cylindrospermopsis raciborskii with regard to temperature and light.

Table 1. Physical characteristics of Lake Bnińskie (BN) and Lake Bytyńskie (BY) in western Poland.

	Lake BN	Lake BY
Latitude	52°12.7	52°30.5
Longitude	17°06.8	16°30.1
Area (ha)	225.9	308.8
Max. depth (m)	8.5	7.0
Average depth (m)	4.2	3.5
Max. width (m)	655	1490
Max. length (m)	4545	4160
Length of shore line (m)	11830	17475

Fig. 2. Phytoplankton composition in Lake Bnińskie from July to October in the years 2004–2007.

Fig. 3. Biomass of Planktothrix agardhii and Cylindrospermopsis raciborskii in Lake Bnińskie from July to October in the years 2004–2007.

Fig. 4. Phytoplankton composition in Lake Bytyńskie from July to October in the years 2004–2007.

Fig. 5. Biomass of Planktothrix agardhii and Cylindrospermopsis raciborskii in Lake Bytyńskie from July to October in the years 2004–2007.

Fig. 6. Ordination diagram for Canonical Correspondence Analysis of the phytoplankton assemblages in Lake Bnińskie.

Table 2. The results of Canonical Correspondence Analyses (CCA) with forward selected variables (P < 0.05) for Lake Bnińskie (BN) and Lake Bytyńskie (BY).

	Lake BN		Lake BY
	Axis 1	Axis 2	Axis 1	Axis 2
Eigenvalue	0.399	0.338	0.462	0.208
Species-environment correlation	0.890	0.935	0.963	0.762
Cumulative percentage variance of species data	17.2	31.8	24.3	35.2
Inter-set correlations with axes
Temperature	−0.060	0.390	0.345	−0.002
pH	−0.044	−0.335	−0.727	0.122
SD	−0.817	0.153	0.767	0.077
	−0.218	−0.730	−0.028	0.323
	0.216	0.235	0.590	−0.142
	−0.357	−0.241	0.586	−0.121
TP	−0.154	−0.186	0.626	−0.096
TN	0.147	−0.255	0.667	−0.135
TN:TP	0.379	−0.007	−0.015	−0.160
Chl a	0.559	−0.112	−0.700	−0.219

Fig. 7. Ordination diagram for Canonical Correspondence Analysis of the phytoplankton assemblages in Lake Bytyńskie.

Table 3. The results of multiple regression analyses for Lake Bnińskie (BN) and Lake Bytyńskie (BY) showing the main environmental factors related to the abundance of P. agardhii and C. raciborskii.

	Model	R ^2	P
Lake BN
Planktothrix agardhii	Y = 54.81 − 64.6 * SD	0.517	0.000
Cylindrospermopsis raciborskii	No significant variables in the model
Lake BY
Planktothrix agardhii	Y = 54.16 − 50.6 * SD − 0.04 * + 0.088 * + 0.119 * Chla-a − 0.007 * TN + 0.032 * TP	0.918	0.000
Cylindrospermopsis raciborskii	Y = 0.122 + 0.003 *	0.318	0.001