The underwater soundscape of the North Sea.

As awareness on the impact of anthropogenic underwater noise on marine life grows, underwater noise measurement programs are needed to determine the current status of marine areas and monitor long-term trends. The Joint Monitoring Programme for Ambient Noise in the North Sea (JOMOPANS) collaborative project was funded by the EU Interreg to collect a unique dataset of underwater noise levels at 19 sites across the North Sea, spanning many different countries and covering the period from 2019 to 2020. The ambient noise from this dataset has been characterised and compared - setting a benchmark for future measurements in the North Sea area. By identifying clusters with similar sound characteristics in three broadband frequency bands (25-160 Hz, 0.2-1.6 kHz, and 2-10 kHz), geographical areas that are similarly affected by sound have been identified. The measured underwater sound levels show a persistent and spatially uniform correlation with wind speed at high frequencies (above 1 kHz) and a correlation with the distance from ships at mid and high frequencies (between 40 Hz and 4 kHz). Correlation with ocean current velocity at low frequencies (up to 200 Hz), which are susceptible to nonacoustic contamination by flow noise, was also evaluated. These correlations were evaluated and simplified linear scaling laws for wind and current speeds were derived. The presented dataset provides a baseline for underwater noise measurements in the North Sea and shows that spatial variability of the dominant sound sources must be considered to predict the impact of noise reduction measures.

Bacterial metabolism of alpha-pinene: pathway from alpha-pinene oxide to acyclic metabolites in Nocardia sp. strain P18.3.

Over 20 gram-positive bacteria were isolated by elective culture with (+/-)-alpha-pinene as the sole carbon source. One of these strains, Nocardia sp. strain P18.3, was selected for detailed study. alpha-Pinene-grown cells oxidized, without lag, alpha-pinene, alpha-pinene oxide (epoxide), and the cis and trans isomers of 2-methyl-5-isopropylhexa-2,5-dienal. No other tested terpene was oxidized at a significant rate. alpha-Pinene was not metabolized by cell extracts in the presence or absence of NADH or NADPH. Cell extracts catalyzed a rapid decyclization of alpha-pinene oxide, in the absence of added cofactors, with the formation of cis-2-methyl-5-isopropylhexa-2,5-dienal. Further oxidation of the aldehyde to the corresponding acid occurred in the presence of NAD. Both activities were induced by growth with alpha-pinene. A rapid, nonenzymic transformation of the cis aldehyde into the trans isomer occurred in glycine buffer. The trans isomer was also a substrate for the NAD-linked aldehyde dehydrogenase. The distribution of the alpha-pinene oxide lyase in alpha-pinene-utilizing Pseudomonas spp. was also investigated and was compatible with the two alternative ring-cleavage sequences that have been proposed on the basis of accumulated metabolites.

Purification and properties of alpha-pinene oxide lyase from Nocardia sp. strain P18.3.

alpha-Pinene oxide is an intermediate in the degradation of alpha-pinene by Nocardia sp. strain P18.3 and some Pseudomonas strains. The epoxide is cleaved by a lyase which catalyzes a concerted reaction in which both rings of the bicyclic structure are cleaved with the formation of cis-2-methyl-5-isopropylhexa-2,5-dienal. The enzyme has been purified to homogeneity from Nocardia sp. strain P18.3. It was induced by growth with alpha-pinene and constituted 6 to 7% of the soluble protein of cell extracts. The apparent molecular weight of the native enzyme was 50,000 by ultracentrifugal analysis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis gave two dissimilar subunits with apparent molecular weights of 17,000 and 22,000. The enzyme was devoid of prosthetic groups, had no cofactor requirement, and had a broad pH activity range, a Km for alpha-pinene oxide of 9 microM, and a turnover number of 15,000. Inhibitors included sulfhydryl reactive compounds, terpene epoxides, and pinane derivatives with substituent groups at carbon 3. A mechanism for the concerted reaction has been proposed in which decyclization is initiated by donation of a proton from the catalytic center to the oxygen of the epoxide with consequent destabilization. In vitro the enzyme was inactivated during catalysis, and a reactive cationic intermediate may be responsible for this phenomenon. The enzyme should be classified as a lyase EC 4.99.-.-.

Metabolite production during the biodegradation of the surfactant sodium dodecyltriethoxy sulphate under mixed-culture die-away conditions.

Sodium dodecyltriethoxy sulphate (SDTES), either pure or as a component of commercial surfactant mixtures, underwent rapid primary biodegradation by mixed bacterial cultures in OECD screen and river-water die-away tests. Inoculation of [35S]SDTES-containing solutions with OECD screen test media acclimatized to surfactants or their degradation products led to production of various 35S-labelled glycol sulphates and their oxidation products, all known to occur during degradation of [35S]SDTES by pure bacterial isolates. Triethylene glycol monosulphate was the major catabolite together with smaller amounts of di- and monoethylene glycol monosulphates implying, by analogy with pure cultures, that ether-cleavage was the major primary biodegradation step. The oxidation product (carboxylate derivative) of each glycol sulphate was also detected together with metabolites tentatively identified as omega-/beta-oxidation products of the dodecyl chain. Relatively little SO2-4 was liberated directly from SDTES but mixed cultures derived from sewage could metabolize the sulphated glycols to SO2-4. The environmental relevance of these degradation routes was established by following metabolite production from [35S]SDTES in full-scale river-water die-away tests. Triethylene glycol sulphate was formed first, then rapidly oxidized to acetic acid 2-(diethoxy sulphate) which persisted as the major metabolite for 2-3 weeks. Small amounts of sulphated derivatives of di- and monoethylene glycols were also detected during the same period. Very little SO2-4 was formed directly from SDTES but large amounts accompanied the eventual disappearance of glycol sulphate derivatives. None of the 35S-labelled organic metabolites was persistent and, whenever [35S]SDTES was a component of a commercial mixture, all ester sulphate was completely mineralized to 35SO4(2-) within 28 d.