Bacterial biomass production and ammonium regeneration in Mediterranean sea water supplemented with amino acids. 1. Correlations between bacterial biomass, bacterial activities and environmental parameters

Abstract

Batch systems were used to establish the N balance of a marine coastal water to quantify responses to organic N (amino acid) enrichment in summer and winter. During both seasons, the amino-acid enriched batch clearly showed solicitation and growth phases in bacterial communities. Maximum growth rates were 0.38 h-1 at 25.degree. C and 0.07 h-1 at 10.degree. C in summer and winter experiments as estimated from direct counts. Short sampling time (1 h) and parameters (direct counts, plate counts, biovolumes measurements, ATP, chlorophyll, mineral salts, 14C uptake, mineralization) describing bacterial growth and activity were used. Parameter associations determined via principal component analysis, discarding the problem of quantity with standardized variables, showed analogous responses in the blank and in enriched batches in summer. High mineralization rates of carbon (40%) and N (regeneration ratio 0.65 in June, 0.5 in Jan.) were observed in conditions of substrate excess.