13 Nov 2020

13 Nov 2020

Review status: a revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

Spatiotemporal patterns of N2 fixation in coastal waters derived from rate measurements and remote sensing

Mindaugas Zilius1, Irma Vybernaite-Lubiene1, Diana Vaiciute1, Donata Overlingė1, Evelina Grinienė1, Anastasija Zaiko2,3, Stefano Bonaglia1,4, Iris Liskow5, Maren Voss5, Agneta Andersson6, Sonia Brugel6, Tobia Politi1, and Paul A. Bukaveckas7 Mindaugas Zilius et al.
  • 1Marine Research Institute, Klaipeda University, Klaipeda, 92294, Lithuania
  • 2Coastal and Freshwater Group, Cawthron Institute, Nelson, 7042, New Zealand
  • 3Zealand Institute of Marine Science, University of Auckland, Auckland, Private Bag 92019, New Zealand
  • 4Department of Marine Sciences, University of Gothenburg, Box 461, Gothenburg, 40530, Sweden
  • 5Department of Biological Oceanography, Leibniz Institute for Baltic Sea Research, Rostock, 18119, Germany
  • 6Department of Ecology and Environmental Sciences, Umeå University, Umeå, 90187, Sweden
  • 7Center for Environmental Studies, Virginia Commonwealth University, Richmond, VA 23284, USA

Abstract. Coastal lagoons are important sites for nitrogen (N) removal via sediment burial and denitrification. Blooms of heterocystous cyanobacteria may diminish N retention as dinitrogen (N2) fixation offsets atmospheric losses via denitrification. We measured N2 fixation in the Curonian Lagoon, Europe's largest coastal lagoon, to better understand the factors controlling N2 fixation in the context of seasonal changes in phytoplankton community composition and external N inputs. Temporal patterns in N2 fixation were primarily determined by the abundance of heterocystous cyanobacteria, mainly Aphanizomenon flosaquae, which became abundant after the decline in riverine nitrate inputs associated with snowmelt. Heterocystous cyanobacteria dominated the summer phytoplankton community resulting in strong correlations between chlorophyll-a (Chl-a) and N2 fixation. We used regression models relating N2 fixation to Chl-a, along with remote sensing-based estimates of Chl-a to derive lagoon-scale estimates of N2 fixation. N2 fixation by pelagic cyanobacteria was found to be a significant component of the lagoon's N budget based on comparisons to previously derived fluxes associated with riverine inputs, sediment-water exchange and losses via denitrification. To our knowledge, this is the first study to derive ecosystem-scale estimates of N2 fixation by combining remote sensing of Chl-a with empirical models relating N2 fixation rates to Chl-a.

Mindaugas Zilius et al.

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Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Mindaugas Zilius et al.

Mindaugas Zilius et al.


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Short summary
In fresh and brackish waters, algal blooms are often dominated by cyanobacteria, which have the ability to utilize atmospheric nitrogen. Cyanobacteria are also unusual in that they float to the surface and are dispersed by wind-driven currents. Their patchy and dynamic distribution makes it difficult to track their abundance and quantify their effects on nutrient cycling. We used remote sensing to map the distribution of cyanobacteria in a large Baltic lagoon and quantify their contributions.