Divergent composition of algal-bacterial biofilms developing under various external factors

Figures & data

Table 1 . Physical and chemical variables during May to July 2002 in two water bodies sampled in Leiduinen: Nieuw Kanaal (NK) and Oranjekom (OK). k: light attenuation coefficient calculated from PAR measurements in absence of floating mats.

	NK			OK
Variable	minimum	average	maximum	minimum	average	maximum
N Kjedahl (mg l^−1)	< 0.2	0.33	0.66	< 0.2	0.46	0.82
NO3 (mg l^−1)	< 0.2	1.8	4.1	0.9	3.6	6.2
PO4 total (mg l^−1)	0.07	0.11	0.22	0.11	0.25	0.52
SiO2 (mg l^−1)	3.8	7.9	11.7	5.3	7.0	8.6
Chl a (μg l^−1)	< 2	8.8	23	3.1	9.6	50
T (°C)	17.9	19.2	20.9	16.0	17.1	18.8
Conductivity (mS)	562	585	600	677	703	728
k (m^−1)	0.7	1.0	1.2	0.9	1.4	1.9

Fig. 1. Relative abundance of algae and bacteria (determined by Confocal Laser Scanning Microscopy) and extracellular polymeric substances (EPS, in relative fluorescence units) in young biofilms growing at the three locations studied at Leiduinen. (a) Nieuw Kanaal (NK); (b) Oranjekom (OK) east; (c) OK west. Error bars represent standard deviations (n = 12).

Fig. 2. Carbon and Chl a content of biofilms at different stages of development. (a) Total organic (TOC) and inorganic carbon (TIC) content; (b) Chl a content. Site abbreviations as in Fig. 1. Error bars represent standard deviations (n = 4).

Fig. 3. Concentrations of accessory pigments relative to Chl a (both in μg cm^{− 2}) in the biofilms at the three locations studied. (a) OK east; (b) OK west; (c) NK. Error bars represent standard deviations. Error bars as in Fig. 2.

Fig. 4. Carbohydrate concentrations in the biofilms, divided into three fractions: extracellular loose, extracellular bound and internal. (a) NK; (b) OK east; (c) OK west. Error bars as in Fig. 2.

Fig. 5. Concentrations of EPS (a) and internal carbohydrates (b) in the biofilms relative to Chl a.