, Volume 569, Issue 1, pp 113-127

Ectoenzyme kinetics in Florida Bay: Implications for bacterial carbon source and nutrient status

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Abstract

Ectoenzyme kinetics [alkaline phosphatase, aminopeptidase (AM), lipase, α-glucosidase, and β-glucosidase] were determined over a seasonal cycle at four stations, Little Madeira Bay (northeast), Duck Key (east), Bob Allen Key (south-central), and Whipray Basin (north-central), which represent distinct regions of Florida Bay. Spatial and temporal variations in ectoenzyme kinetics were related to biotic and abiotic drivers in order to discern potential ectoenzyme substrate sources. Generally, ectoenzyme activities were higher in the central bay and lowest in the eastern bay. One pronounced exception was AM activity, which was highest at the mangrove fringe along the northeastern bay and reflected increased contribution of organic nitrogen inputs from upstream Everglades wetlands. When ectoenzymes were normalized to bacterial abundances, these trends dissipated and highest cell-specific activities were observed consistently in the south-central region. Relationships between ectoenzyme kinetics and environmental and biological parameters were complex, but three main spatially determined differences were discernable. Ectoenzyme kinetics were controlled by phosphorus availability in the eastern bay, by organic matter availability in the south-central bay, by microbial community composition and organic matter availability in northeastern bay (wetlands transition area), and by microbial community composition in the north-central bay. These differences in enzyme kinetics further support the hypothesis of distinct microbial communities in different regions of Florida Bay and provide insight into biogeochemical cycles and the microbial food web within Florida Bay.