Learning chemistry through placements: Building on good practice and identifying new opportunities

This article presents and discusses the results of a project that focussed on identifying new work-based learning opportunities for chemistry students. Firstly, we investigated whether typical chemistry employers, who traditionally host sandwich or year-long placements, are able to offer short-term (e.g. summer) placements as an alternative work-based learning experience. Secondly, we determined to what extent non-traditional employers of chemistry graduates are also able to offer relevant and appropriate placement opportunities for chemistry students

Impacts of assignment in problem-based learning: A case study from chemistry

The use of problem-based learning (PBL) within undergraduate chemistry courses is increasing in popularity. Despite several previous reports describing the impacts of PBL in terms of students‟ motivation and interest in chemistry, evaluations of its impact with respect to student learning are virtually absent. Here, an evaluation of PBL case studies in chemistry is made by consideration of assessment performance data over a six year period. The performance data are considered at different stages of the undergraduate courses and are compared against related data from laboratory work and closed-book examinations. These performance data are complemented by student feedback. The analysis reveals that, regardless of level, students find PBL case studies enjoyable and motivating. In contrast, performance in assessed work is found to depend strongly on assessment criteria. Students perform comparably with other modes of assessment when the PBL case study assessment criteria are familiar to them. In contrast, when the assessment criteria demand wider consideration of PBL outcomes, typical of those appropriate for the latter stages of degree courses, lack of familiarity with such criteria appears to result in lower performance in assessments, despite careful counselling from the tutor

On the stability of various highly branched isoprenoid (HBI) lipids in stored sediments and sediment extracts

publisher: Elsevier articletitle: On the stability of various highly branched isoprenoid (HBI) lipids in stored sediments and sediment extracts journaltitle: Organic Geochemistry articlelink: http://dx.doi.org/10.1016/j.orggeochem.2016.04.010 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved

Abrupt climate changes for Iceland during the last millennium: evidence from high resolution sea ice reconstructions

International audienceA high resolution account of Icelandic sea ice over the last millennium has been constructed using a novel proxy based on the presence in sediments of a biomarker (IP25) produced by sea ice algae. Comparison with historical sea ice records demonstrates a strong correlation between documented sea ice occurrences and the IP25 proxy. An excellent agreement is also observed between the IP25 record and a diatom-based sea surface temperature reconstruction obtained from the same core and the Crowley and Lowery Northern Hemisphere temperature reconstruction. Using this approach, we provide new historical sea ice data for periods where records are scarce or absent and evidence for abrupt changes to sea ice and/or climate conditions around Iceland during the Little Ice Age

Group 2i Isochrysidales produce characteristic alkenones reflecting sea ice distribution

Alkenones are biomarkers produced solely by algae in the order Isochrysidales that have been used to reconstruct sea surface temperature (SST) since the 1980s. However, alkenone based SST reconstructions in the northern high latitude oceans show significant bias towards warmer temperatures in core-tops, diverge from other SST proxies in down core records, and are often accompanied by anomalously high relative abundance of the C37 tetra-unsaturated methyl alkenone (%C37:4). Elevated %C37:4 is widely interpreted as an indicator of low sea surface salinity from polar water masses, but its biological source has thus far remained elusive. Here we identify a lineage of Isochrysidales that is responsible for elevated C37:4 methyl alkenone in the northern high latitude oceans through next-generation sequencing and lab-culture experiments. This Isochrysidales lineage co-occurs widely with sea ice in marine environments and is distinct from other known marine alkenone-producers, namely Emiliania huxleyi and Gephyrocapsa oceanica. More importantly, the %C37:4 in seawater filtered particulate organic matter and surface sediments is significantly correlated with annual mean sea ice concentrations. In sediment cores from the Svalbard region, the %C37:4 concentration aligns with the Greenland temperature record and other qualitative regional sea ice records spanning the past 14 kyrs, reflecting sea ice concentrations quantitatively. Our findings imply that %C37:4 is a powerful proxy for reconstructing sea ice conditions in the high latitude oceans on thousand- and, potentially, on million-year timescales.publishedVersio

Identification of C 25 highly branched isoprenoid (HBI) alkenes in diatoms of the genus Rhizosolenia in polar and sub-polar marine phytoplankton.

We report the identification of a range of C25 highly branched isoprenoid (HBI) alkenes and certain sterols in filtered phytoplankton samples obtained from western Svalbard (Arctic) and near South Georgia (South Atlantic, sub-Antarctic) in 2016 and 2014, respectively. The C25 HBIs contained 3–5 double bonds and had structures identified previously from analysis of laboratory diatom cultures. The same HBIs were also identified in individual diatom taxa isolated from the mixed assemblages and with reasonably similar distributions. Thus, C25 HBIs were identified in Rhizosolenia setigera isolated from western Svalbard near-surface waters, while the same HBIs were also found in R. polydactyla f. polydactyla and R. hebetata f. semispina picked from seawater collected from a site in the South Atlantic. The main sterol composition was slightly different between the two locations, with cholesta-5,24-dien-3β-ol (desmosterol) identified as one of the major components in the sample from West Svalbard, consistent with the diatom assemblage being dominated by R. setigera. In contrast, the major sterol in the South Atlantic sample was cholesta-5,22-dien-3β-ol (22-dehydrocholesterol), likely reflecting the relatively high proportion of the genus Pseudo-nitzschia. For both locations, the suite of HBIs included a tri-unsaturated isomer (HBI III; 6Z-2,6,10,14-tetramethyl-9-(3'-methylpent-4-enylidene)-pentadec-6-ene), proposed in previous studies as a potential proxy measure of pelagic sea ice-edge conditions, and thus, a counterpart to the mono- and di-unsaturated HBIs IP25 and IPSO25, which have been used as seasonal sea ice proxies in the Arctic and Antarctic, respectively. HBI III has been reported previously in sediments from West Svalbard and we report here its occurrence in a small number of surface sediments from the South Atlantic. For both regions, HBI III was present as one of the major HBIs in sediments, which contrasts the HBI distributions in the filtered phytoplankton samples, where HBIs with four and five double bonds were the major components. Differences in HBI distributions between phytoplankton and sediment samples may potentially be due to the presence of other (unanalysed) diatoms in the filtered water samples, seasonal/annual variability in the production of HBIs by a range of diatoms, differential degradation of HBIs between sources and sediments, or a combination of these. Interestingly, we did not detect any C30 HBIs in the water samples, picked cells or sediments from either location, despite earlier reports of these lipids in laboratory cultures of R. setigera. This study represents the first source identification of certain C25 HBI lipids under in situ pelagic conditions

Biomarker-based H-Print quantifies the composition of mixed sympagic and pelagic algae consumed by Artemia sp.

publisher: Elsevier articletitle: Biomarker-based H-Print quantifies the composition of mixed sympagic and pelagic algae consumed by Artemia sp. journaltitle: Journal of Experimental Marine Biology and Ecology articlelink: http://dx.doi.org/10.1016/j.jembe.2016.12.007 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved

Variability in drift ice export from the Arctic Ocean to the North Icelandic Shelf over the last 8000 years: A multi-proxy evaluation

publisher: Elsevier articletitle: Variability in drift ice export from the Arctic Ocean to the North Icelandic Shelf over the last 8000 years: A multi-proxy evaluation journaltitle: Quaternary Science Reviews articlelink: http://dx.doi.org/10.1016/j.quascirev.2016.06.012 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved

Source-specific biomarkers as proxies for Arctic and Antarctic sea ice

Over the last decade or so, certain source-specific C-25 highly branched isoprenoid (HBI) lipid biomarkers have emerged as useful proxies for Arctic and Antarctic sea ice. Thus, IP25 (Ice proxy with 25 carbon atoms) and IPSO25 (Ice proxy for the Southern Ocean with 25 carbon atoms) represent binary measures of past seasonal sea ice in the Arctic and Antarctic, respectively. A further tri-unsaturated HBI (generally referred to as HBI III) appears to provide proxy evidence for the region of open water found adjacent to sea ice (i.e. the marginal ice zone (MIZ)) in both polar regions. This review provides an update on current knowledge pertaining to each proxy. The first section focuses on describing those studies that have aimed to establish the underlying features of each proxy, including source identification and spatial distribution characteristics. The second section presents some important analytical considerations pertinent to the accurate identification and quantification of HBI biomarkers. The third section describes how each HBI proxy is normally interpreted within the sedimentary record for palaeo sea ice reconstruction purposes. This includes the interpretation of individual and combined biomarker profiles such as the PIP25 index and multivariate decision tree models. A summary of all previous palaeo sea ice reconstructions based on HBIs is also given, which includes examples that clarify or reinforce our understanding of the individual or combined biomarker signatures. Some knowledge gaps and areas for future research are also briefly described