Carbon monoxide and chromophoric dissolved organic matter cycles in the shelf waters of the northern California upwelling system

Abstract

[1] An annual program of approximately bimonthly seawater sampling was conducted off the coast of the Bodega Marine Laboratory in the California Current upwelling system (CCUS) to investigate controls on dissolved carbon monoxide (CO) and its photochemical parent, chromophoric dissolved organic matter (CDOM). A diel steady state model was developed to quantify CO sources and sinks throughout the day. Observed midday CO spanned 2.7-17 nmol L À1 , and correlated strongly with coincident CDOM absorption; however, rapid microbial consumption rates (0.05-0.80 h À1 ) were such that $95% of the CO generated was metabolized within the ocean surface. Further indication of the dominant influence of the microbial ecosystem was the persistent observation of a strong ''dark production,'' which contributed $25% of the diurnal source strength within the top 17 m of the ocean. The dark source correlated strongly with biological oxidation rates and CDOM, suggesting that it is the result of incomplete respiration of biologically labile DOM. CDOM was lowest in recently upwelled waters, implying that its origin is from the induced primary production and not from shelf sediment resuspension. The estimated CO air-sea flux was highly variable (average of 5 mmol m À2 d À1 ), and most likely inconsequential to the atmospheric budget in coastal regions. The photolytic source strength of CO 2 from CDOM (2.7 mmol m À2 d À1 ) was estimated by scaling to modeled CO photoproduction rates. This photolytic remineralization rate represents $2.5% of the net primary production in the CCUS, implying that CDOM photobleaching may play a significant role in the carbon cycling of upwelling systems.

Air–sea exchange of CO<sub>2</sub> at a Northern California coastal site along the California Current upwelling system

“…The 30 m of land between the tower base and the ocean accounted for less than 0.01 % of the flux footprint, even under conditions with the smallest flux footprint. The water depth within the footprint area was estimated to be about 20-30 m (Day and Faloona, 2009 In addition, the sensor compared well with the pCO 2 system reported in Ikawa and Oechel (2011). All the data used in this study are summarized in Table 1.…”

“…The predominant alongshore wind causes Ekman transport along with lateral shear vorticity, which generates positive curl in the surface stress, resulting in strong coastal upwelling. Spatial distributions of water temperature indicated that our study area was particularly favorable for wind-driven upwelling events (Day and Faloona, 2009). The region's wind-driven upwelling cycle, nutrient availability and subsequent primary production have been described in CoOP WEST (Wind Events and Shelf Transport) studies Largier et al, 2006;Wilkerson et al, 2006).…”

“…The repeating cycles of upwelling and relaxation create a unique biological system. Upwelling carries deep water that is relatively cold and nutrient rich to the surface, but increased turbidity (Day and Faloona, 2009) and lateral exports of nutrients inhibit production, while nutrients brought up to the surface are consumed during the subsequent relaxation period (Largier et al, 2006;Wilkerson et al, 2006 …”

A new method for continuous measurements of oceanic and atmospheric N<sub>2</sub>O, CO and CO<sub>2</sub>: performance of off-axis integrated cavity output spectroscopy (OA-ICOS) coupled to non-dispersive infrared detection (NDIR)

“…Furthermore, since no ancillary measurements of relevant parameters such as CDOM (chromophoric dissolved organic matter) and Chl a were carried out during these cruises, the differences between underway and discrete methods cannot be directly related to either of those. In addition, the absence of parallel discrete sampling for CO measurements makes it difficult to assess to which extent the results from former studies are comparable to ours because they are based on gas chromatographic methods (Conrad et al, 1982;Law et al, 2002;Stubbins et al, 2006;Day and Faloona, 2009;Kitidis et al, 2011). Therefore, future studies employing at-sea measurements of CO should also include discrete measurements in order to directly compare the results to those from continuous measurements using OA-ICOS.…”

Variability of carbon monoxide and carbon dioxide apparent quantum yield spectra in three coastal estuaries of the South Atlantic Bight

“…This may reflect the photoinhibition of CO uptake by bacteria, with higher bacterial consumption rates when solar UV radiation is less intense and substrate concentrations have been elevated by photochemistry (Tolli and Taylor, 2005). Photochemical production of CO in the oceans has been well studied recently (Day and Faloona, 2009;Miller and Moran, 1997;Stubbins et al, , 2006White et al, 2010;Zafiriou et al, 2003Zafiriou et al, , 2008Ziolkowski and Miller, 2007;Kitidis et al, 2011), and global annual production of CO in the worlds oceans is currently estimated at between 30 and 84 Tg C yr −1 (Zafiriou et al, 2003;Stubbins et al, 2006;Fichot and Miller, 2010).…”