Absorption and fluorescence of dissolved organic matter in the waters of the Canadian Arctic Archipelago, Baffin Bay, and the Labrador Sea

Abstract. Photolysis of dimethylsulfide (DMS), a secondary photochemical process mediated by chromophoric dissolved organic matter (CDOM), has previously been demonstrated to be an important loss term of DMS in the surface layer of warm seas and the Southern Ocean. The role of photolysis in regulating the DMS dynamics in northern polar seas remains, however, less clear. This study for the first time determined the apparent quantum yield (AQY) spectra of DMS photooxidation in Canadian Arctic seas covering Baffin Bay, the Mackenzie estuary and shelf, and the Canada Basin. The DMS AQY was fairly invariant at salinities < 25 but rose rapidly with further increasing salinity in an exponential manner. Salinity can therefore be used as a quantitative indicator of the DMS AQY. The DMS AQY in the ultraviolet (UV) wavelengths was linearly and positively correlated with the spectral slope coefficient (275–295 nm) of the CDOM absorption spectrum, suggesting that marine CDOM photosensitizes the degradation of DMS more efficiently than does terrestrial CDOM or that coastal waters contain higher concentrations of substrates (most likely dissolved organic matter and redox metals) that compete for DMS-oxidizing radical intermediates. High concentrations of nitrate (~ 12 μmol L−1) in deep water samples boosted DMS photooxidation by 70–80%, due likely to radical chemistry of nitrate photolysis. Coupled optical-photochemical modeling, based on the obtained DMS AQY spectra, shows that UV-A (320–400 nm) accounted for 60–75% of the DMS photolysis in the sunlit surface layer and that photochemistry degraded DMS on an e-folding time from 9 to 100 d (mean: 29 d). The photooxidation term on average accounted for 21% of the DMS gross loss rate and was comparable to the atmospheric DMS ventilation rate estimated for the same geographic regions. The methodology adopted here to study the relationship between CDOM quality/origin and DMS AQYs, if applicable to other ocean areas, may bring results of global significance for DMS cycling and might have implications for probing other CDOM-driven photochemical processes.

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Sponge (Porifera) fauna of Frobisher Bay, Baffin Island, Canada with the description of an Iophon rich sponge garden

Zootaxa ◽

10.11646/zootaxa.4576.2.5 ◽

2019 ◽

Vol 4576 (2) ◽

pp. 301 ◽

Cited By ~ 2

Author(s):

CURTIS DINN ◽

EVAN EDINGER ◽

SALLY P. LEYS

Keyword(s):

Growth Form ◽

Stock Assessment ◽

Canadian Arctic ◽

Geographic Range ◽

Labrador Sea ◽

Baffin Island ◽

Remotely Operated Vehicle ◽

Baffin Bay ◽

A Site ◽

Complex Habitat

The deep-water sponge fauna of the Canadian Arctic remains to be fully described, particularly in areas that are not sampled by fisheries stock-assessment trawl surveys such as the major bays and fjords of the northern Labrador Sea and Baffin Bay. Frobisher Bay is a large inlet located on the southeast of Baffin Island. We used a remotely operated vehicle, as well as box cores and Agassiz trawls to study the sponge fauna of this bay. Over three years, from 2015 to 2017, sponge specimens were collected representing 24 distinct sponge taxa. Dense gardens of Iophon koltuni Morozov, Sabirov, & Zimina, 2019 were discovered at a site near Hill Island in inner Frobisher Bay. The species has a unique finger-like growth form and provides complex habitat in the inner bay. Other sponge species are new to the Northern Labrador marine ecoregion. In particular, we report geographic range extensions of Tetilla sibirica (Fristedt, 1887) and Craniella polyura (Schmidt, 1870), and provide spicule measurements and descriptions of Iophon piceum (Vosmaer, 1882) and Mycale lingua (Bowerbank, 1866). These species identifications, geographic range extensions, and an expanded description of a species synonym represent the first inventory of the sponge fauna of Frobisher Bay.

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