Abstract

Phosphorus (P) cycling by microbial activity is highly relevant in the eutrophication of lakes. In this context, the contents of organic (Po) and inorganic (Pi) phosphorus, the activity of acid (ACP) and alkaline (ALP) phosphomonoesterase (Pase), and the abundances of bacterial Pase genes (phoD, phoC, and phoX) were studied in sediments from Budi Lake, a eutrophic coastal brackish water lake in Chile. Our results showed spatiotemporal variations in P fractions, Pase activities, and Pase gene abundances. In general, our results showed higher contents of Pi (110-144 mg kg- 1), Po (512-576 mg kg-1), and total P (647-721 mg kg- 1) in sediments from the more anthropogenized sampling sites in summer compared with those values of Pi (86-127 mg kg- 1), Po (363-491 mg kg- 1) and total P (449-618 mg kg- 1) in less anthropogenized sampling sites in winter. In concordance, sediments showed higher Pase activities (mu g nitrophenyl phosphate g-1 h-1) in sediments from the more anthropogenized sampling sites (9.7-22.7 for ACP and 5.9 to 9.6 for ALP) compared with those observed in less anthropogenized sampling sites in winter (4.2-12.9 for ACP and 0.3 to 6.7 for ALP). Higher abundances (gene copy g-1 sediment) of phoC (8.5-19 x 108), phoD (9.2-47 x 106), and phoX (8.5-26 x 106) genes were also found in sediments from the more anthropogenized sampling sites in summer compared with those values of phoC (0.1-1.1 x 108), phoD (1.4-2.4 x 106) and phoX (0.7-1.2 x 106) genes in the less anthropogenized sites in winter. Our results also showed a positive correlation between P contents, Pase activities, and abundances of bacterial Pase genes, independent of seasonality. The present study provided information on the microbial activity involved in P cycling in sediments of Budi Lake, which may be used in further research as indicators for the monitoring of eutrophication of lakes.