Chromophoric dissolved organic matter (CDOM) in first-year sea ice in the western Canadian Arctic

Abstract

We monitored the spatiotemporal progression of chromophoric dissolved organic matter (CDOM) in first-year sea ice in the western Canadian Arctic between mid-March and early July 2008. CDOM abundance in bottom ice, as quantified by absorption coefficient at 325 nm, a CDOM (325), showed a positive, linear relationship with the concentration of chlorophyll a, being low at the start of ice algal accumulation, highly enriched during the peak bloom and early post-bloom, and depleted again during sea ice melting. Vertical profiles of CDOM in early and late spring were typically characterized by slight to moderate elevations at both the surface and bottom and rather constancy within the interior ice. In the ice algae-thriving mid-spring, L-type profiles prevailed due to extremely high CDOM in the lowermost 10-cm layer. Bottom-layer CDOM in landfast ice (a CDOM (325): 15.8 m ). CDOM in the ice cover, except the bottom layer, was generally lower than or similar to that in the under-ice surface water. Salinity accounted for 58% of the CDOM variability in drift ice having minimal terrestrial and ice algal signatures. CDOM absorption spectra of algaerich bottom ice samples exhibited ultraviolet (UV) absorption shoulders attributable to mycosporine-like amino acids (MAAs). These compounds were readily photodegradable by solar UV radiation. Our results suggest that 1) inclusion of organic solutes and in situ biological production are the dominant processes controlling the distribution of CDOM in sea ice in the study area, 2) biological production in bottom ice is a minor source of CDOM to the underlying surface water; 3) CDOM plays a critical role in shielding sympagic organisms in bottom ice against UV radiation; 4) the MAAs are effective photoprotectants only under low-UV conditions.

Contrasting optical properties of surface waters across the Fram Strait and its potential biological implications

“…The sub-surface CDOM absorption maximum (30-120 m) in the EGC area was linked to river and sea-ice brine enriched water, characteristic of the Arctic mixed layer and upper halocline waters and concurs with observations of high CDOM in the EGC and surface waters of the Eurasian Basin (Amon, 2003;Stedmon et al, 2011). Lower absorption in the upper 25-30 m layer in the EGC may reflect the influence of sea-ice melt dilution and photobleaching of CDOM (Granskog et al, 2007Pegau, 2002;Xie et al, 2014). It has been suggested that CDOM incorporated into sea ice can be lost through brine drainage in summer (Xie et al, 2014) as well as photobleaching (Belzile et al, 2000;Xie and Gosselin, 2005).…”

“…Lower absorption in the upper 25-30 m layer in the EGC may reflect the influence of sea-ice melt dilution and photobleaching of CDOM (Granskog et al, 2007Pegau, 2002;Xie et al, 2014). It has been suggested that CDOM incorporated into sea ice can be lost through brine drainage in summer (Xie et al, 2014) as well as photobleaching (Belzile et al, 2000;Xie and Gosselin, 2005). Potential dilution of CDOM by sea-ice melt is then contrary to previous works in the Arctic, which suggested that CDOM accumulates in sea-ice during its formation and is subsequently released to surface waters during sea-ice melt providing a source of CDOM to the upper ocean layer (Scully and Miller, 2000).…”

Bio‐optical properties of Arctic drift ice and surface waters north of Svalbard from winter to spring

“…The vertical distribution of averaged Tchla values have resembled a L‐shape, as shown in Figure c, similar to those reported by Xie et al . [] and Hill and Zimmerman []. Tchla was very low in the upper parts of the ice (Figure c and Table ).…”

“…Particulate absorption in Arctic sea ice has been studied very sparsely [ Mundy et al ., ]. Investigations focused on CDOM in sea ice during different stages of its formation [e.g., Müller et al ., ; Xie et al ., ; Logvinova et al ., ; Hill and Zimmerman , ]. It has been documented that CDOM absorption was in most cases enriched (relative to salinity) compared to underlying water [e.g., Müller et al ., ]; its values were elevated in the bottom of the ice and ice algae significantly contributed to CDOM accumulation [e.g., Xie et al ., ; Granskog et al ., ; Hill and Zimmerman , ].…”

Optical Properties of Chromophoric Dissolved Organic Matter in the Yinma River Watershed and Drinking Water Resource of Northeast China

“…In order to characterize the spatial and temporal CDOM variations in aquatic environments, spectral analysis of CDOM (absorption and fl uorescence) can trace its origin and chemical composition [26][27]. Based on the characteristics of the absorption spectrum, spectral indices (e.g., absorption coeffi cient at specifi c wavelength), absorption ratio (E 250:365 ), spectral slopes (S, S 275-295 and S 350-400 ), the ratio of S 275-295 and S 350-400 , and SUVA 254 values have been developed to trace DOM source, molecular size, and aromatic hydrocarbon content, etc.…”