Comparative Study of the N Metabolism of Phytoplankton and Periphyton Communities in Oligotrophic Lakes. Part of a Coordinated Programme on Isotopic-Tracer-Aided Research and Monitoring on Agricultural Residue - Biological Interac

摘要

Limnological research at Castle Lake, CA, and Lake Tahoe, CA-NEV, USA, during the period 1977-1982 has emphasized the effects of nutrient enrichment and deficiency on primary producers. The low ambient pools of nitrogenous nutrients and their low rates of transformation have necessitated the use of isotope tracer methods ( exp 14 C, exp 15 N, exp 13 N). These techniques have been used in concert with physiological assays, growth bio-assays, and whole-ecosystem nitrogen enrichments. Our most significant results, to date, include: (1) Delineation of 5 algal communities which are spatially distinct yet occur in the same lake and which differ with regard to their principal sources of N; (2) Determination of the relative affinities of the above communities for the various sources of N; (3) Demonstration of the importance of internally regenerated N to phytoplankton productivity; (4) Development of sensitive methodology to utilize the short-lived radioisotope exp 13 N (t1/2=10 mins) for studies of denitrification and nitrate uptake in aquatic ecosystems; (5) Comparisons of a variety of physiological assays for N-deficiency in aquatic microorganisms, involving short-term and long-term experiments in containers and in an N-enriched lake. (Atomindex citation 14:745939)