Multi-proxy analysis of a well-dated 25,000-year (25 ka) lake-sediment sequence from Lake Challa, on the eastern flank of Mt Kilimanjaro, reveal the climatic controls which govern both the lake’s palaeohydrology and the climate-proxy record contained in the mountain’s receding ice cap. The oxygen-isotope record extracted from diatom silica (d18Odiatom) in Lake Challa sediments captured dry conditions during the last glacial period and a wet late-glacial transition to the Holocene interrupted by Younger Dryas drought. Further, it faithfully traced gradual weakening of the southeastern monsoon during the Holocene. Overall, d18Odiatom matches the branched isoprenoid tetraether (BIT) index of rainfall-induced soil run-off, except during 25–22 ka BP and the last 5 ka when insolation forcing due to orbital precession enhanced the northeastern monsoon. This pattern arises because during these two periods, a weakened southeastern monsoon reduced the amount of rainfall during the long rain season and enhanced the opposing effect of evaporation intensity and/or length of the austral winter dry season. Importantly, our lake-based reconstruction of moisture-balance seasonality in equatorial East Africa also helps understand the oxygen-isotope record contained in Mt. Kilimanjaro ice. Negative correlation between ice-core d18O and Lake Challa d18Odiatom implies that temperature, not moisture balance, is the primary climate control on the long-term trend in ice-core d18O

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Stable isotope analysis of sedimentary carbon in lakes can help reveal changes in terrestrial and aquatic carbon cycles. A method based on a single, photosynthetic organism, where host effects are minimised, should offer more precision than carbon isotope studies of bulk lake sediments. Here we systematically develop a method for use on fossil lacustrine diatom frustules, adapted from previous studies in marine environments. A step-wise cleaning experiment on diatomaceous lake sediments from Lake Challa, Mt, Kilimanjaro, was made to demonstrate the necessary treatment stages to remove external sedimentary carbon. Changes in soluble carbon compounds during these cleaning experiments were measured using GC/MS. Mass spectrometry methods were refined to measure the small percentage carbon of these samples and details of these methods are presented.Samples of cleaned diatoms containing <1% carbon yielded robust results. Carbon isotope analysis of diatom samples containing different species mixtures were performed and showed suggestive differences, although the effects lay within current experimental error and require further work.Unlike work on oxygen and silicon isotopes from diatom frustules, mineral contamination had no discernable impact on the diatom carbon isotope ratios from these sediments. The range of values found in the lakes investigated thus far can be interpreted with reference to the supply and nature of carbon from the catchment as well as demand generated from lake primary productivity.3

Over the last decade the number of students coming to university with a BTEC qualification has risen. As BTEC students are more likely to come from widening participation backgrounds, accepting students with a BTEC qualification has been instrumental in helping universities to broaden access to Higher Education. However, the poorer progression and retention of students attending university with a BTEC qualification is a key area of concern. The aim of this study was to explore the transition experience of Biosciences students entering university with a BTEC qualification in order to better target support for these students. Focus groups with current students who entered university with a BTEC qualification, and semi-structured interviews with teaching staff at feeder colleges, highlighted that the BTEC equipped students with many transferable skills relevant to university study. In particular it prepared students for time management, report writing, practical laboratory work and working independently. However, our findings suggest that further support is required in mathematics, chemistry, examination and revision techniques. We propose that instilling confidence, encouraging friendship groups, more transparent advertising and developing inclusive curricula may help to improve BTEC student retention and progression.

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