Spatial and temporal variation of Nuphar lutea pigment content in small boreal lakes: effect of water colour and phosphorus concentration

Abstract

AbstractThe spatial and temporal variation of Nuphar lutea chlorophyll content was studied in 12 small lakes in Finland to clarify the bioindicator potential of N. lutea chlorophyll content for monitoring lake brownification. Significant in-lake variation in water colour and total phosphorus concentration was observed in a few study lakes. At highest, the in-lake variation for water colour was 13% and for total phosphorus concentration 27%. However, the in-lake variation in water quality did not coincide with significant in-lake variation of N. lutea chlorophyll content. The total chlorophyll concentration (chlorophyll a + b) varied in a few lakes, but the chlorophyll a and b ratio (chlorophyll a:b) did not change within the lakes. The chlorophyll a:b, however, varied between lakes and decreased significantly with increasing water colour and total phosphorus concentration in Nuphar lutea individuals collected near the lake outflow. The chlorophyll content of N. lutea did not show significant temporal variation during the one-week sampling period despite variable weather conditions. Chlorophyll a:b of N. lutea seems to be a possible bioindicator for monitoring brownification, as it can differentiate lakes from each other based on a small difference in water colour but does not react to short-term in-lake variations in the water quality.