Evidence for dissolved organic nitrogen and phosphorus uptake during a cyanobacterial bloom in Florida Bay

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 280:73-83 (2004) - doi:10.3354/meps280073 Evidence for dissolved organic nitrogen and phosphorus uptake during a cyanobacterial bloom in Florida Bay P. M. Glibert1,*, C. A. Heil2,3, D. Hollander2, M. Revilla1, A. Hoare2, J. Alexander1, S. Murasko2 1University of Maryland Center for Environmental Science, Horn Point Laboratory, PO Box 775, Cambridge, Maryland 21613, USA 2College of Marine Science, University of South Florida, 140 7th Avenue South, St. Petersburg, Florida 33701, USA 3Present address: Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, 100 Eighth Avenue South, St. Petersburg, Florida 33701, USA *Email: glibert@hpl.umces.edu ABSTRACT: Florida Bay, a shallow, seagrass-dominated bay in southern Florida, USA, receives significant nutrient inputs and has experienced seagrass losses and microalgal blooms within the last several decades. Inorganic nutrient inputs have been well characterized, but the role of organic nutrients, specifically of dissolved organic nitrogen (DON) and organic phosphorus (DOP), in supporting microbial processes in the bay is unknown. In this study various techniques were used to assess the importance of these nutrients along a transect in Florida Bay when a cyanobacterial bloom occurred in the central region in November 2002. These techniques included measurements of ambient particulate and dissolved nutrients, enzyme (urease and alkaline phosphatase) activities, and experiments to determine rates of 15N uptake (nitrate, ammonium, urea, and amino acids over a period of 0.5 h) and long-term (48 h) changes in microbial biomass and 15N natural abundance in enrichment bioassays. The cyanobacterial bloom in central Florida Bay was associated with the highest concentrations of DON and DOP, whereas the microflagellate- and diatom-dominated eastern bay region was associated with the highest concentrations of inorganic nutrients. The zeaxanthin:chlorophyll a ratio (an indicator of the relative contribution of cyanobacteria to phytoplankton biomass) was positively correlated with the rate of uptake of urea, and negatively correlated with the rate of uptake of inorganic nitrogen. The opposite pattern was observed for the fucoxanthin:chlorophyll a ratio (indicative of relative diatom biomass) and the peridinin:chlorophyll a ratio (indicative of relative photosynthetic dinoflagellate biomass), suggesting that different algal groups were using different N substrates. Biomass responses in the bioassay experiments showed that phytoplankton (as chlorophyll a) responded to DON additions in the western region and to DOP additions in the eastern region, but heterotrophic bacteria, in contrast, responded to DOP additions in the west and DON additions in the east. These findings thus demonstrate the potential for different sources of N, including DON, to stimulate different components of the algal community, and for the phytoplankton and bacteria to respond differently to N and P. KEY WORDS: Florida Bay · Cyanobacteria · Organic N · Organic P · Nutrient limitation · Urease · Alkaline phosphatase · Bioassay · Nutrient uptake rates Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 280. Online publication date: October 14, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.