Publication Date:
2015-08-24
Description:
Instrumental equipment unsuitable or unavailable for fieldwork as well as lack of ship space can necessitate the preservation of seawater samples prior to analysis in a shore-based laboratory. Mercuric chloride (HgCl2) is routinely used for such preservation, but its handling and subsequent disposal incur significant risks and expense. Benzalkonium chloride (BAC) has been used previously for freshwater samples. Here, we assess BAC as a less hazardous alternative microbial inhibitor for marine samples prior to the measurement of oxygen-to-argon (O2/Ar) ratios, as used for the determination of plankton net community production. BAC at a concentration of 50 mg dm−3 inhibited microbial activity for at least three days in seawater with chlorophyll a (Chl a) concentrations up to 1 mg m−3, possibly longer when Chl a concentrations were lower. BAC concentrations of 100 and 200 mg dm−3 were no more effective than 50 mg dm−3. With fewer risks to human health and the environment, and no requirement for expensive waste disposal, BAC could be a viable alternative to HgCl2 for short-term preservation of seawater samples, but is not a replacement for HgCl2 in the case of oxygen triple isotope analysis, which requires storage over weeks to months. In any event, further tests on a case-by-case basis should be undertaken if use of BAC was considered, since its inhibitory activity may depend on concentration and composition of the microbial community.
Print ISSN:
1812-0806
Electronic ISSN:
1812-0822
Topics:
Geosciences
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