Novel molecular fingerprinting of marine avian diet provides a tool for gaining insights into feeding ecology

C₂₅ highly branched isoprenoids (HBIs) are produced by a relatively small number of diatom species, yet are common constituents of almost all marine environments. Previously, detection of HBIs in a few aquatic Arctic animals has indicated the potential use of these lipids for providing novel ecological information. In the current study, analysis of lipid extracts of livers from Leach’s storm petrel (Oceanodroma leucorhoa) and Brunnich’s guillemot (Uria lomvia) facilitated identification and quantification of HBI isomers. HBIs were found in the tissues of all specimens with clear differences in the abundances and distributions of individual HBI isomers both between Atlantic as well as Arctic birds. These differences are consistent with contrasting oceanographic regimes and suggests that regional differences in HBIs are reflected in the tissues of consumers. Tissue-specific assessment of HBI distributions has also revealed the presence of these lipids in muscle for the first time. This study represents the first report of HBI lipids in birds and provides evidence that these lipids are transferred across trophic levels and extends their potential use as chemical tracers beyond the ecology of aquatic organisms.     

Longitudinal variability in streamwater chemistry and carbon and nitrogen fluxes in restored and degraded urban stream networks

Stream restoration has increasingly been used as a best management practice for improving water quality in urbanizing watersheds, yet few data exist to assess restoration effectiveness. This study examined the longitudinal patterns in carbon and nitrogen concentrations and mass balance in two restored (Minebank Run and Spring Branch) and two unrestored (Powder Mill Run and Dead Run) stream networks in Baltimore, Maryland, USA. Longitudinal synoptic sampling showed that there was considerable reach-scale variability in biogeochemistry (e.g., total dissolved nitrogen (TDN), dissolved organic carbon (DOC), cations, pH, oxidation/reduction potential, dissolved oxygen, and temperature). TDN concentrations were typically higher than DOC in restored streams, but the opposite pattern was observed in unrestored streams. Mass balances in restored stream networks showed net uptake of TDN across subreaches (mean ± standard error net uptake rate of TDN across sampling dates for Minebank Run and Spring Branch was 420.3 ± 312.2 and 821.8 ± 570.3 mg m(-2) d(-1), respectively). There was net release of DOC in the restored streams (1344 ± 1063 and 1017 ± 944.5 mg m(-2) d(-1) for Minebank Run and Spring Branch, respectively). Conversely, degraded streams, Powder Mill Run and Dead Run showed mean net release of TDN across sampling dates (629.2 ± 167.5 and 327.1 ± 134.5 mg m(-2) d(-1), respectively) and net uptake of DOC (1642 ± 505.0 and 233.7 ± 125.1 mg m(-2) d(-1), respectively). There can be substantial C and N transformations in stream networks with hydrologically connected floodplain and pond features. Assessment of restoration effectiveness depends strongly on where monitoring is conducted along the stream network. Monitoring beyond the stream-reach scale is recommended for a complete perspective of evaluation of biogeochemical function in restored and degraded urban streams.     

EVALUATION OF THE ROSGEN STREAM CLASSIFICATION SYSTEM IN CHEQUAMEGON‐NICOLET NATIONAL FOREST,WISCONSIN1

ABSTRACT: Data collected from 121 stream reaches during 1991 to 1993 were evaluated to determine the applicability of the Rosgen Stream Classification System (RSCS) to the low relief terrain within the Chequamegon‐Nicolet National Forest (CNNF) in Wisconsin, USA. All reaches were classified to RSCS Level I and II except that 10.7 percent had sinuosities below the continuum limits and one reach had a predominantly organic substrate. Five of eight possible RSCS Level I types were observed including B, C, D, A, E, and F; 86 percent were C and E types. Seventeen of 94 possible RSCS Level II types were observed. Most reaches were slightly entrenched, had low to moderate width/depth ratios, relatively low sinuosity, low slope, and sand or gravel as the dominant channel material. Discriminant analyses were used to verify the applicability of RSCS for streams within the CNNF; discriminant functions correctly classified 92.5 and 94.7 percent of the Level I and II RSCS types, respectively. When limits for E and F types were modified slightly at Level II by adding an additional category for slopes less than 0.1 percent (a modification we recommend for low relief terrain), discriminant functions correctly classified 99.1 percent of the types. Adding another slope break at 0.3 percent produced similar results. Based on our analyses, RSCS works well within the CNNF and is probably applicable to other areas with low‐relief terrain.     

Environmental and Biological Assessment of Exposure to Benzene in Petroleum Workers

Occupational exposure to benzene was measured in two gasoline marketing terminals and five major refineries in Singapore. A total of 280 workers were monitored over two years. This assessment was carried out with two primary objectives: (1) To find out the extent of occupational exposure to benzene in the petroleum industry in Singapore, (2) To identify suitable biomarkers for monitoring of low levels of benzene exposure. The exposure was measured in five different categories of petroleum and petrochemical workers, i.e., truck drivers, despatch assistant, process operators, oil movements operators and laboratory technicians. The results revealed wide variations in exposure, from 0.01 to 13.6 ppm for personal time weighted average (TWA) exposure over the whole workshift. The exposure of truck drivers appeared to be the highest, with geometric mean (GM) of 1.98 ppm (ranged from 0.25 to 13.6 ppm). The average benzene exposure for process operators was relative low with a GM of 0.04 ppm. Lowest benzene exposure was found in the laboratory technicians, with a GM of 0.02 ppm. As cigarette smoking is known to affect metabolism of benzene, data analyses on the relationships with environmental exposure were conducted only on the 190 nonsmokers. The results showed that urinary trans, trans-muconic acid (ttMA), unmetabolized benzene in urine (UBZ) and benzene in blood (BBZ) were better biomarkers for low level benzene exposure as compared to urinary phenolic metabolites in urine, such as hydroquinone, phenol and catechol.     

Identification of a novel di-unsaturated C25 highly branched isoprenoid in the marine tube-dwelling diatom Berkeleya rutilans

Highly branched isoprenoids (HBIs) are known to be biosynthesised by diatoms and are a common component of many marine and freshwater environments. However, the ability to produce these unusual hydrocarbons appears to be restricted to a few diatom species that are represented by just four genera (Haslea, Pleurosigma, Rhizosolenia and Navicula). Despite this, we routinely observe some HBIs in the natural environment that are absent from cultures of known HBI-producing diatoms, indicating the possibility of further sources. Having identified one commonly observed, yet unknown HBI isomer in estuarine sediments, we isolated and cultured diatoms in the laboratory to identify the source of this novel di-unsaturated C₂₅ HBI. Here, we show that analysis of purified extracts obtained from a laboratory culture of the tube-dwelling diatom Berkeleya rutilans enabled determination of the structure of this new compound by combined NMR spectroscopic and mass spectrometric analysis. This represents the first identification of an HBI alkene within the Berkeleya genus and adds to the growing number of reports of genera that produce these unusual hydrocarbons. The newly characterised HBI diene appears to be common in marine sediments and has also been reported in a range of marine biota, thus making it a potential tracer of source organic matter, as has been found for other HBI alkenes.     

Structural confirmation of the sea ice biomarker IP25 found in Arctic marine sediments

IP₂₅ is a highly branched isoprenoid and an organic geochemical biomarker that is produced by some Arctic sea ice diatoms. IP₂₅ has previously been used in Arctic palaeo sea ice reconstruction studies and as a tracer for studying Arctic food webs. Here, the molecular structure of IP₂₅ has been confirmed by ¹H and ¹³C NMR spectroscopy following large-scale extraction from marine sediments obtained from the Canadian Arctic and purification using a combination of open-column and HPLC chromatographic methods. The structure of IP₂₅ was consistent between the three different sampling locations and was identical to that found previously for this biomarker following synthesis from a closely related highly branched isoprenoid diene. Since this study represents the first structural characterisation of IP₂₅ in sediments, future analysis of sedimentary IP₂₅ for palaeo Arctic sea ice reconstructions can be carried out with much greater confidence.     

Flood Protection: Highlighting an Investment Trap Between Built and Natural Capital

We present a simulation model developed to communicate a potential investment trap associated with using man‐made river engineering to protect built infrastructure. A small system dynamics model in STELLA? was constructed following a collaborative model‐building process to increase understanding among stakeholders of the role natural capital plays in wealth creation. We set out to explore the dynamic relationship between investing tax revenue in natural capital (specifically forested headwaters and low land wetlands) rather than built capital (specifically stopbanks) for flood protection in the Manawatū watershed, New Zealand. Significant investment is currently required to maintain and enhance river engineering infrastructure and keep pace with changes in the river's geomorphology. Viewed from a systems perspective, we suggest diversion of a proportion of existing funding into restoration of forested headwaters on steep slopes and restoration of functioning wetlands on floodplains could in the longer term provide an effective approach to flood protection. Co‐benefits of increased natural capital include the ecosystem services nutrient cycling, sediment capture, water purification, biodiversity, pollination, and cultural and recreational values. Overcoming an investment trap requires a longer term perspective. This simple model consisting of two feedback loops and two delays aims to contribute to an ongoing stakeholder dialogue concerning the Manawatū River watershed in New Zealand.     

H-Print: a new chemical fingerprinting approach for distinguishing primary production sources in Arctic ecosystems

The unambiguous identification of discrete sources of organic matter is critical for understanding the processes that affect ecosystem structure. Here, we demonstrate how changes in the relative proportions of highly branched isoprenoid lipids can provide a straightforward analytical method to distinguish between organic matter derived from sea ice and seawater within an Arctic ecosystem. In combination with stable isotope analysis, we reconstruct the organic matter pathway across trophic levels, thereby elucidating specific organic matter energy transfers. Combined, these methods will provide a useful analytical approach for determining ecosystem structure in the future. This is likely to become increasingly important as the Arctic continues to experience a phase of rapid climate change.     

Mediated Modeling in Water Resource Dialogues Connecting Multiple Scales

We observe a paradigm shift toward collaborative, multi‐level (from local to global) water management and suggestions for scale‐related design principles in the literature. Decision‐support tools are needed that can help achieve scale design principles. Mediated modeling (MM) refers to model building with people, rather than for people. This tool belongs to a family of participatory, systems oriented tools. This article explores their suitability for addressing challenges and principles that arise at multiple‐scales. MM can promote the understanding of cross‐level and cross‐scale links, creating salient, credible, and legitimate knowledge and encouraging boundary functions. Prerequisites for successful MM processes include an openness and willingness to collaborative learning. As new “meso‐level” institutions emerge to address complex challenges in water management collaboratively, tools like MM may play an important role in structuring dialogues, developing adaptive management capacity and advance an ecosystem services approach.