Submerged Aquatic Bryophytes in Colour Lake, a Naturally Acidic Polar Lake with Occasional Year-Round Ice-Cover

• Main Authors: Ian Hawes, Dale T. Andersen, Wayne H. Pollard
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2002
• Subjects: Arctic; Axel Heiberg Island; Heiberg; Arctique*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.567.2961; http://pubs.aina.ucalgary.ca/arctic/Arctic55-4-380.pdf

ABSTRACT. Colour Lake is a small, naturally acidic (pH 3.7) lake on Axel Heiberg Island (Canadian High Arctic) that experiences occasional year-round ice cover. We investigated the benthic vegetation of this lake, with a specific aim of determining whether the annual growth of benthic bryophytes reflects the state of summer ice cover. We found the bed of the lake to be almost completely covered by mosses or liverworts to a depth of 22 m. The mosses showed annual growth bands 10–30 mm in length, visible as changes in leaf density and size. Four to five bands retained recognizable leaves and measurable amounts of chlorophyll-a (chla), and up to 12 bands were recognizable from leaf scars. We could not find a consistent relationship between band length and persistence of ice cover for a given year. We suggest that this lack is due to the complex effects of ice cover on moss growth conditions, specifically on the water temperature and irradiance at depth. Photosynthetic characteristics of Calliergon over a range of light and temperature conditions, determined using pulse amplitude–modulated fluorometry, are presented in support of this argument. We conclude that moss banding patterns are an unreliable method of hindcasting episodic failure of ice to melt in Arctic lakes. Key Words: Arctic lakes, aquatic bryophytes, photosynthesis, light, temperature RÉSUMÉ. Le lac Colour est un petit lac de l’île Axel Heiberg, située dans l’Extrême-Arctique canadien, dont l’acidité (pH = 3,7) est naturelle et qui reste parfois englacé toute l’année. On a étudié la végétation benthique de ce lac, dans le but précis de déterminer si la croissance annuelle des bryophytes benthiques reflète l’état de la couverture de la glace en été. On a trouvé que le lit du lac