Sea surface microlayer (SML) and underlying subsurface water (SSW) bacterial communities from the Baltic Sea were studied using culturing, flow cytometry and terminal restriction fragment length polymorphism (T-RFLP). Dissolved organic matter (DOM) of water samples was determined using high performance liquid size-exclusion chromatography and by measuring dissolved organic carbon. Cadmium, copper, lead and mercury were also measured from the water samples. Two methods were compared for SML sampling: metal screen (MS) and polycarbonate membranes (PCM). All sampling sites were located in the Archipelago Sea off the southwest coast of Finland. The hypothesis was that because of its unique features, such as accumulation of nutrients and pollutants and being unshaded from UV-radiation, the SML would support a different bacterial community to that of SSW. T-RFLP profiles showed differences between the bacterial community compositions of SML and SSW at most sampling sites. In addition, temporal and sampling-site-dependent differences were observed. There were no significant differences in DOM in SML and SSW samples. In most cases, the number of bacteria was slightly higher in the SML than in SSW. No significant cytotoxicity was observed in any of the water samples. Since no temporal trends were obvious, our results suggest that, although bacterial communities in the SML Archipelago Sea differ to some extent from the ones living in SSW, SML is a dynamic environment where bacterial communities possibly develop originally from bacterioplankton and change over time.KEY WORDS: Sea surface microlayer · Bacterial community structure · T-RFLP · Dissolved organic matter
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In this study Natural organic matter (NOM) characteristics and variations of catchment samples (brooks and collector lakes) from Western Finland, and drinking water produced from the same catchment were examined. Seasonal and spatial NOM variations were followed by means of DOC and HPLC-SEC with UV and fluorescence detection. NOM decreased from drains to lakes by 35 to 75% and from drains to drinking water by 73 to 94%. Drains had a higher NOM content in summer and a lower NOM content in winter and spring. Lakes showed inverse patterns and had a higher NOM content in winter and spring and a lower NOM content in summer. HPLC-SEC separated 8 molecular weight fractions. In drains the HMW fractions represented up to 80% of the NOM, in lake waters HMW fractions accounted for 50 to 70% of the NOM. In drinking water IMW fractions dominated. Increased NOM in raw water during winter was associated with increased IMW fractions and the appearance of HMW fractions in drinking water, DOC increasing from 1.4 mg C/L in summer to 5.8 mg C/L in winter. SPH-Tryptophan correlated with the dissolved organic nitrogen and DOC of the samples. The drain affected by agriculture generally presented higher SPH-Tryptophan values than the unaffected drain.
HPLC-SEC with UV254, trytophane-like and tyrosine-like fluorescence detection was used to characterize onsite wastewater effluents from septic tanks. In total, 69 wastewater effluents, 15 of them greywater (GWE) and 54 blackwater effluents (BWE), were analysed for water quality indicators: BOD-7, DOC, COD, Total-N and TDP using conventional methods. The chromatograms showed well-separated three regions, referred to as chromatographic indicators (ChIs), which were tested as surrogates for the conventional indicators. The best surrogates for BOD-7 and DOC were found in region 3 of the tyrosine-like chromatograms. Data showed that Tyr-3, representing the sum of the tyrosine-like fractions from 8.25 min, could be used reliably to assess the BOD-7 and DOC of GWE and to approximate the BOD-7 of BWE. In addition, Tyr-3a, the fractions between 8.25 and 14 min, could be used to approximate the DOC of BWE. Furthermore, the strong correlation between COD and Tyr (all the tyrosine-type fractions) for GWE and between COD and UV254-3 for BWE allows reliable calculation of the COD of GWEs and its approximation of BWEs by linear regression. Total-N correlated weakly with tryptophan-like fractions. The use of ChI as surrogates for BOD-7, DOC and COD is an important finding that enables reliable and fast analysis without use of harmful chemicals.
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