Investigating tools for biomonitoring browning in streams: chlorophyll content of

The chlorophyll content of the bryophyte species Fontinalis antipyretica was studied in seven small boreal streams of varying water quality. The aim was to determine whether the chlorophyll content of F. antipyretica responds to increasing water colour, and if the bryophyte could thus be used as a bioindicator for browning in stream environments. Significant variation in the CHL contents (CHL a+b, CHL a:b) of F. antipyretica was observed between streams of differing water colour. Despite this, no significant effect of water colour or the dissolved organic carbon (DOC) concentration on the CHL contents (CHL a+b, CHL a:b) was observed. However, the CHL a:b ratio decreased significantly with increasing light attenuation coefficient, thus suggesting that light is an important factor causing physiological changes in F. antipyretica. The DOC concentration explained one-third of the light attenuation coefficient, whilst no significant effect of water colour was found. Our findings suggest that whilst the CHL a:b of F. antipyretica can indicate changes in light conditions, it does not directly show a clear pressure-response association with increased water colour or DOC concentration.