Ecological preferences of freshwater Ulva flexuosa (Ulvales; Ulvophyceae): development of macroalgal mats in a Tulce fishpond (Wielkopolska Region, Poland)

Figure 1

Figure 2

Figure 3

Values of Pearson’s linear correlation coefficient and the coefficient of determination (r2) for morphometric parameters of U_ flexuosa thalli and macroalgal mats with physicochemical factors

	pH	Depth	N-NH4 +	P-PO4-	O2	Temperature
Average length of a thallus	-0.45ns	0.90 P < 0.001, ns − not significant, coefficient of determination − r2 in brackets	-0.45 ns	0.10 ns	0.68 P < 0.05	-0.38 ns
	-	(0.82)	-	-	(0.45)	-
Average width of a thallus	-0.18 ns	-0.03 ns	-0.23 ns	-0.40 ns	-0.08 ns	-0.63 P < 0.05
	-	-	-	-	-	(0.39)
Surface of mats	-0.73 P < 0.01	0.43 ns	-0.62 P < 0.05	-0.75 P < 0.01	-0.20 ns	-0.47 ns
	(0.54)	-	(0.39)	(0.56)	-	-
Density of thalli per m-2 of mats	-0.48 ns	0.89 P < 0.001, ns − not significant, coefficient of determination − r2 in brackets	-0.53 ns	0.06 ns	0.82 P < 0.01	-0.42 ns
	-	(0.80)	-	-	(0.67)	-
Percentage of branched thalli per m2 of mats	0.54 ns	0.10 ns	0.59 P < 0.05	0.59 P < 0.05	0.14 ns	0.16 ns
	-	-	(0.35)	(0.35)	-	-
Percentage of unbranched thalli per m2 of mats	-0.76 P < 0.01	0.31 ns	-0.46 ns	-0.67 P < 0.05	-0.15 ns	-0.31 ns
	(0.58)	-	-	(0.45)	-	-
Percentage of young thalli per m2 of mats	0.60 P < 0.05	-0.48 ns	0.70 P < 0.01	0.30 ns	-0.31 ns	0.52 ns
	(0.36)	-	(0.50)	-	-	-
Percentage of mature thalli per m2 of mats	-0.82 P < 0.001, ns − not significant, coefficient of determination − r2 in brackets	0.43 ns	-0.84 P < 0.001, ns − not significant, coefficient of determination − r2 in brackets	-0.59 P < 0.05	0.05 ns	-0.34 ns
	(0.68)	-	(0.71)	(0.35)	-	-
Percentage of submerged thalli per m2 of mats	-0.66 P < 0.05	0.89 P < 0.001, ns − not significant, coefficient of determination − r2 in brackets	-0.58 P < 0.05	-0.14 ns	0.50 ns	-0.43 ns
	(0.44)	(0.80)	(0.33)	-	-	-
Percentage of free-floating thalli per m2 of mats	0.73 P < 0.01	-0.86 P < 0.001, ns − not significant, coefficient of determination − r2 in brackets	0.70 P < 0.05	0.22 ns	-0.48 ns	0.40 ns
	(0.54)	(0.74)	(0.49)	-	-	-

Results of the Mann-Whitney U test of the difference in mean values of physicochemical factors under and outside of Ulva mats (n = 12)_ Results where P < 0_05 are statistically significant and given in bold_

Parameters	Unit	Mann-Whitney U test	Statistical significance		Sign
pH	-	66.0	P = 0.75	UMM	OMM	>
Conductivity	µS cm-1	31.0	P = 0.01			>
N-NH4+	mg l-1	64.0	P = 0.66			>
N-NO3-		32.5	P = 0.02			<
P-PO43-		49.0	P = 0.19			>
Fetotal		63.0	P = 0.62			>
NaCl		67.5	P = 0.85			>
Cl-		67.5	P = 0.81			>

Comparison of anatomical features of Ulva flexuosa (n =30) and average values of morphometric features of Ulva mats (n =12)_

Features	Units	Mean	Min.	Max	SD – standard deviation
Length of thalli	cm	20.00	4.2	66.40	0.53
Width of thalli		0.59	0.15	1.15	0.14
Length of cells	µm	11.15	8.10	15.5	1.99
Width of cells		8.09	4.96	10.78	1.39
Number of pyrenoids	-	2	1	3	0.75
Perimeter of pyrenoids	µm	3.19	2.40	3.90	0.38
Surface of mats	m2	12.83	1.0	30.0	11.17
Density of thalli per m2 of mats	m-2	75.92	10.0	250.0	66.16
Percentage of branched thalli per m2 of mats	%	49.58	10.0	90.0	26.67
Percentage of unbranched thalli per m2 of mats		22.92	5.0	75.0	24.07
Percentage of young thalli per m2 of mats		37.50	5.0	95.0	32.72
Percentage of mature thalli per m2 of mats		55.92	1.0	95.0	31.74
Percentage of submerged thalli per m2 of mats		35.25	0	95.0	38.78
Percentage of free-floating thalli per m2 of mats		59.58	10.0	100	32.71

Average values of physicochemical factors of water for the examined site of Ulva flexuosa (n =12)

Parameter	Units	Mean	Min.	Max	SD – standard deviation
Temperature	ºC	17.3	14.10	22.0	2.16
Depth of water	m	2.4	2.0	3.2	0.37
pH	-	7.2	6.03	8.4	1.37
Conductivity	μS cm-1	1044.7	655.0	1421.0	196.38
O2	mg O2 l-1	8.0	4.2	3.4	8.07
N-NH4 +	mg N l-1	1.2	0.18	4.0	1.26
N-NO3 -	mg N l-1	0.2	0.06	0.4	0.09
P-PO4 3-	mg PO4 l-1	0.5	0.12	0.8	0.25
Total Fe	mg Fe l-1	0.2	0.06	0.3	0.07
NaCl	mg NaCl l-1	91.1	61.05	143.6	25.27
Cl-	mg Cl l-1	55.2	37.0	87.0	15.32