ill., map; Report title; Includes bibliographical references
Abstract. The presence of a one-person submersible at Crater Lake, Oregon in August 1989 provided a unique opportunity to examine the vertical distribution of a deep-water moss at one of the deepest and clearest lakes in the world. Living specimens of this moss, which was identified as Drepanocladus exannulatus Warnst., were found at depths between 25 m and 120 m. Dense beds of the moss were observed at depths between 30 m and 70mt a region that corresponded to the zone of maximum phytoplankton primary production in the water column. The moss population supported a diverse assemblage of epiphytic algae of which the most abundant genera included Oedogonium. Cladophora. Rhizoclonium, Tribonema, Vaucheria. and the diatoms Melosira. Epithemia. Gomphonema^Cymbella^Cocconeis^Fragilaria^Navicula and Synedra. Chemical and physical data support the hypothesis that the lower limit of distribution of the moss is determined by light limitation, whereas the upper limit is related to the availability of nitrogen and trace elements. In August 1989 a series of deep-water dives were made at selected locations in Crater Lake (Oregon) using Deep Rover, a one-person submersible. These dives, which were supported for the most part by the National Park Service, were primarily designed to identify the magnitude and characteristics of hydrothermal inputs to the deep lake. In addition, the National Geographic Society provided supplementary funds to support an investigation of the deep-water benthic communities in the lake. Although early biological studies of the benthic flora and fauna were greatly inhibited by the sampling methods and equipment available at the time, both Hasler (1937) and Brode (1938) found that a deep-water moss was present in dredge samples obtained from depths as great as 120 m below the water surface. A more recent study of the Crater Lake ecosystem (Drake et al. 1990) has generated considerable interest in this organism, as it apparently generates relatively large biomasses at depths of 30 m or more below the water surface. Moreover, relationships between the deep-water moss, with its assemblage of epiphytic algae, and the nutrient dynamics and bioenergetics of the Crater Lake ecosystem are entirely unknown. The presence of the submersible at Crater Lake in 1989 provided a unique
Abstract. The presence of a one-person submersible at Crater Lake, Oregon in August 1989 provided a unique opportunity to examine the vertical distribution of a deep-water moss at one of the deepest and clearest lakes in the world. Living specimens of this moss, which was identified as Drepanocladus exannulatus Warnst., were found at depths between 25 m and 120 m. Dense beds of the moss were observed at depths between 30 m and 70mt a region that corresponded to the zone of maximum phytoplankton primary production in the water column. The moss population supported a diverse assemblage of epiphytic algae of which the most abundant genera included Oedogonium. Cladophora. Rhizoclonium, Tribonema, Vaucheria. and the diatoms Melosira. Epithemia. Gomphonema^Cymbella^Cocconeis^Fragilaria^Navicula and Synedra. Chemical and physical data support the hypothesis that the lower limit of distribution of the moss is determined by light limitation, whereas the upper limit is related to the availability of nitrogen and trace elements. In August 1989 a series of deep-water dives were made at selected locations in Crater Lake (Oregon) using Deep Rover, a one-person submersible. These dives, which were supported for the most part by the National Park Service, were primarily designed to identify the magnitude and characteristics of hydrothermal inputs to the deep lake. In addition, the National Geographic Society provided supplementary funds to support an investigation of the deep-water benthic communities in the lake. Although early biological studies of the benthic flora and fauna were greatly inhibited by the sampling methods and equipment available at the time, both Hasler (1937) and Brode (1938) found that a deep-water moss was present in dredge samples obtained from depths as great as 120 m below the water surface. A more recent study of the Crater Lake ecosystem (Drake et al. 1990) has generated considerable interest in this organism, as it apparently generates relatively large biomasses at depths of 30 m or more below the water surface. Moreover, relationships between the deep-water moss, with its assemblage of epiphytic algae, and the nutrient dynamics and bioenergetics of the Crater Lake ecosystem are entirely unknown. The presence of the submersible at Crater Lake in 1989 provided a unique