Feeding, egg production, and respiration rate of pteropods Limacina in Arctic seas

Resumo

The feeding, egg production, and respiration rate of the dominant pteropod Limacina helicina have been studied in Russia’s Arctic seas. The sinking rates of fecal pellets and dead individuals have been measured to estimate their role in vertical carbon flux. As has been shown, the rate of ecophysiological processes taking place in the pteropods is higher than that of copepods, the main consumers of phytoplankton. The gut pigment content in Limacina (3084 ng ind^–1 as a maximum) was two orders of magnitude higher than in copepods. The egg production rate in Limacina even without feeding reached 4000 eggs ind^–1 versus 350–450 egg ind^–1 typical of the dominant copepods even with excess food. A close correlation between the pteropod feeding rate and individual body weight was observed for Limacina rather than a correlation with food concentration. The experimentally estimated sinking rate of Limacina fecal pellets was 270 m day^–1, higher than for most copepods. The sinking rate of dead pteropods reaches 2000 m day^–1. According to the literature, discarded mucous feeding nets sink at a rate of 80 to 1080 m day^–1. Evidently, pteropods play a significant role in biogeochemical cycles by accelerating sedimentation. High rates of all studied processes suggest that Limacina are an important component of plankton communities and play the most important role in trophodynamics at sites of their accumulation.