Growth Rate of an Aquatic Bryophyte (<i>Warnstorfia fluitans</i> (Hedw.) Loeske) from a High Arctic Lake: Effect of Nutrient Concentration

Abstract

The High Arctic is one of the regions most susceptible to climate change on a global scale. Increased temperature, precipitation, and cloud cover are anticipated in the region, with consequent increases in nutrient runoff to surface waters. Mosses are often the dominant submerged macrophyte in Arctic and High Arctic lakes. If the growth rate of mosses in these lakes is nutrient-limited, then production could increase with climate changes that result in higher nutrient concentrations. We conducted a laboratory study to 1) measure the growth response of Warnstorfia fluitans (Hedw.) Loeske from a High Arctic lake to nitrogen and phosphorus availability; and 2) determine whether growth rate was N- or P-limited by examining its relationship to internal P and N content. The growth rates of W. fluitans were generally low, ranging from 0.003 to 0.012 day-1. The growth rates increased with increasing plant P content, but not with increasing N content, indicating that moss growth was P-limited at low P availability in the experiment. Critical plant P concentration for maximum growth rate was 0.086% dry weight. This is the first time a critical P threshold has been calculated. The results imply that if climate changes result in increased P concentrations in surface waters, a higher production of moss could occur in High Arctic lakes.