Ecological constraints on planktonic nitrogen fixation in saline estuaries. I. Nutrient and trophic controls
Howarth, Robert W.
Pace, Michael L.
Likens, Gene E.
MetadataShow full item record
KeywordNitrogen fixation; Heterocystous cyanobacteria; Estuaries; Nitrogen limitation; Nitrogen and phosphorus stoichiometry; Zooplankton grazing; Mesocosms
Heterocystous, planktonic cyanobacteria capable of fixing atmospheric N2 into available nitrogen (N) are common and critically important to nutrient cycling in many lakes, yet they are rarely observed in estuaries at salinities >10 ppt, even when strongly N limited. In a series of mesocosm experiments using water from Narragansett Bay (Rhode Island), we manipulated top-down (grazing) and bottom-up (nutrient) factors hypothesized to exclude heterocystous cyanobacteria from estuaries. We previously reported that planktonic, heterocystous cyanobacteria grew and fixed N in the absence of grazers. Here, we focus on responses to phosphorus (P) additions and grazer manipulations. Zooplankton (Acartia sp.) populations typical of temperate zone estuaries suppressed cyanobacteria, and their influence was direct through grazing rather than indirect on nutrient stoichiometry. Cyanobacterial abundance and heterocysts were low in treatments with no external P inputs. Concentrations of dissolved inorganic P comparable to those in Narragansett Bay were obtained only in P-fertilized mesocosms. Unlike previous estuarine mesocosm experiments with P fertilization, planktonic cyanobacteria grew and fixed N in our experimental systems. However, mean cell and heterocyst abundances under the most favorable conditions (high P, low N:P, and low grazers) were much lower than in comparable freshwater experiments, with N limitation maintained. These results support the hypothesis that intrinsic growth of heterocystous cyanobacteria in saline estuaries is slower than in freshwater, and that slower growth is unlikely to be due to systematic differences in P availability. Slow growth, combined with grazing, can severely limit development of planktonic, N-fixing cyanobacterial blooms in estuaries.
Author Posting. © Inter-Research, 2006. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 309 (2006): 25-39, doi:10.3354/meps309025.
Suggested CitationArticle: Marino, Roxanne, Chan, Francis, Howarth, Robert W., Pace, Michael L., Likens, Gene E., "Ecological constraints on planktonic nitrogen fixation in saline estuaries. I. Nutrient and trophic controls", Marine Ecology Progress Series 309 (2006): 25-39, DOI:10.3354/meps309025, https://hdl.handle.net/1912/4482
Showing items related by title, author, creator and subject.
Phosphate availability and the ultimate control of new nitrogen input by nitrogen fixation in the tropical Pacific Ocean Moutin, T.; Karl, David M.; Duhamel, Solange; Rimmelin, P.; Raimbault, P.; Van Mooy, Benjamin A. S.; Claustre, Hervé (Copernicus Publications on behalf of the European Geosciences Union, 2008-01-29)Due to the low atmospheric input of phosphate into the open ocean, it is one of the key nutrients that could ultimately control primary production and carbon export into the deep ocean. The observed trend over the last 20 ...
Iron availability limits the ocean nitrogen inventory stabilizing feedbacks between marine denitrification and nitrogen fixation Moore, J. Keith; Doney, Scott C. (American Geophysical Union, 2007-04-04)Recent upward revisions in key sink/source terms for fixed nitrogen (N) in the oceans imply a short residence time and strong negative feedbacks involving denitrification and N fixation to prevent large swings in the ocean ...
Nitrogen fixation rates from samples collected in the Chukchi Sea, Arctic Ocean near Barrow, Alaska in August of 2011 (ArcticNITRO project) Sipler, Rachel E.; Bronk, Deborah; Yager, Patricia L. (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: firstname.lastname@example.org, 2017-06-08)This dataset provides rates of nitrogen fixation for the coastal Chukchi Sea near Barrow, Alaska. Nitrogen fixation supplies ‘new’ nitrogen to the global ocean and supports primary production and impacts global biogeochemical ...