et al. # a comprehensive database of paleoclimate records is needed to place recent warming into the longer-term context of natural climate variability. We present a global compilation of quality-controlled, published, temperature-sensitive proxy records extending back 12,000 years through the Holocene. Data were compiled from 679 sites where time series cover at least 4000 years, are resolved at sub-millennial scale (median spacing of 400 years or finer) and have at least one age control point every 3000 years, with cutoff values slackened in datasparse regions. The data derive from lake sediment (51%), marine sediment (31%), peat (11%), glacier ice (3%), and other natural archives. The database contains 1319 records, including 157 from the Southern Hemisphere. the multi-proxy database comprises paleotemperature time series based on ecological assemblages, as well as biophysical and geochemical indicators that reflect mean annual or seasonal temperatures, as encoded in the database. This database can be used to reconstruct the spatiotemporal evolution of Holocene temperature at global to regional scales, and is publicly available in Linked Paleo Data (LiPD) format.

Changes in penguin populations on the Antarctic Peninsula have been linked to several environmental factors, but the potentially devastating impact of volcanic activity has not been considered. Here we use detailed biogeochemical analyses to track past penguin colony change over the last 8,500 years on Ardley Island, home to one of the Antarctic Peninsula's largest breeding populations of gentoo penguins. The first sustained penguin colony was established on Ardley Island c. 6,700 years ago, pre-dating sub-fossil evidence of Peninsula-wide occupation by c. 1,000 years. The colony experienced five population maxima during the Holocene. Overall, we find no consistent relationships with local-regional atmospheric and ocean temperatures or sea-ice conditions, although the colony population maximum, c. 4,000–3,000 years ago, corresponds with regionally elevated temperatures. Instead, at least three of the five phases of penguin colony expansion were abruptly ended by large eruptions from the Deception Island volcano, resulting in near-complete local extinction of the colony, with, on average, 400–800 years required for sustainable recovery.

1. Assemblages of epilithic diatoms, macrophytes, benthic macroinvertebrates and fish were monitored over a 5‐year period (1988–92) in ten lakes and nine streams in the U.K., as part of the U.K. Acid Waters Monitoring Network. All organisms were categorized according to their functional or morphological characteristics and integrated to describe the food web at each site. In general, the flora and fauna of all sites were typical of oligotrophic, softwater systems subject to various degrees of acidification. 2. Salmonids were the only fish caught at any site and brown trout were the dominant species. With only 5 years of data it was not possible to test for directional changes in fish populations at each site. Among sites, fish density was positively associated with pH, and this did not vary between lake outflows and streams or between fish of different age class (0 +, 1 +). Condition factor, reflecting fish health, was not associated with pH among sites, but was negatively associated with fish density and, on average, was higher for fish in streams than those in lake outflows. 3. Variability in the diatom, macrophyte and invertebrate data sets were quantified in three ways using multivariate techniques: species turnover or replacement (temporal variation due to directional change), persistence (the reciprocal of between‐year variability) and within‐year variability (heterogeneity between sample replicates). For all groups, turnover was relatively low and persistence was high. The least persistent macrophyte assemblages occurred in stream sites and this may reflect high inter‐annual variation in the cover of filamentous algae which are prone to scouring. Within‐year variability was higher than turnover or between‐year variability for the diatoms and invertebrates, and highest values were recorded for lake invertebrates. 4. Redundancy analysis, RDA, was used to test the diatom, macrophyte, invertebrate and food web data for evidence of directional changes over time and its significance was assessed using Monte Carlo permutation tests. These tests appeared robust to temporal and spatial variability in the data set. Significant trends could be identified in some data sets despite considerable between‐replicate and non‐linear between‐year variability. 5. Significant linear trends in at least one biological group were found at eight lake and seven stream sites. Only one lake and one stream had significant trends in all four groups. These trends represent changes in the flora and/or fauna, but they can be interpreted in several different ways. Only six sites showed trends that were consistent with our knowledge of species’ responses to water chemistry: three indicated increased acidity and three indicated decreased acidity. At only one site were the biological results consistent with observed chemical changes and there was disagreement at the other five. Of the other nine sites that showed biological changes, two appeared to reflect known physical habitat disturbances; the other seven remain unexplained.

Long-chain alkenones (LCAs) have been used for decades to reconstruct quantitative sea-surface temperature records, but they also have a great potential for paleotemperature reconstructions in lacustrine settings. Here, we investigated how the presence and abundance of LCAs in surface sediments from 106 lakes varied with environmental conditions in lakes of the Northern Great Plains (Canadian Prairies) in southern Saskatchewan, Canada. Consistent with preliminary research, we found LCAs in 55% of surveyed lakes, with mean concentrations of 143 μg/g dry sediment, but very high concentrations (up to 2.3 mg/g dry sediment) in 7% of lakes. Statistical analyses indicate that salinity and stratification play key roles in determining LCA presence and abundance supporting previous research in Spain and the northern Great Plains, USA. Overall, the alkenone unsaturation index () was not correlated significantly with average summer water temperature, probably because the timing of maximum LCA production occurs during the spring season. We conclude that improved seasonal sampling is required within the study lakes to better identify the timing and habitat of haptophyte production, and allow development of environmental temperature reconstruction tools.

Successful management of damaged coastal ecosystems requires reliable scientific evidence of their past state. Here we demonstrate that the sediment record of biotic indicators can be used to quantitatively reconstruct nutrient concentrations preceding the short time span covered by monitoring records. We generated a diatom-based weighted-averaging partial least squares transfer function model for total dissolved nitrogen with a prediction accuracy of 0.09 microg L(-1) (log10 units). The model was applied to sediment core data from Laajalahti Bay, an urban embayment in Helsinki, Finland, where its performance was validated against a approximately 30 yr record of water-quality data and known land-use changes in the watershed. The model tracked well the trends in the nutrient record, although it underestimated very high nutrient concentrations in this highly impacted embayment. The generally good agreement between the actual and predicted values implies that the approach has considerable potential in assessing background nutrient concentrations in coastal waters.