Spatiotemporal patterns of N<sub>2</sub> fixation in coastal waters derived from rate measurements and remote sensing

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 We measured N2 in the Curonian Lagoon, Europe's largest coastal lagoon, to better understand factors controlling context seasonal changes phytoplankton community composition external inputs. Temporal patterns were primarily determined by abundance cyanobacteria, mainly Aphanizomenon flos-aquae, which became abundant after decline riverine nitrate inputs associated with snowmelt. Heterocystous dominated summer resulting strong correlations between chlorophyll a (Chl a) fixation. used regression models relating Chl a, along remote-sensing-based estimates derive lagoon-scale pelagic was found be significant component lagoon's budget based on comparisons previously derived fluxes inputs, sediment–water exchange, To our knowledge, this is first study ecosystem-scale combining remote sensing empirical rates a.