Defining Chlorophyll-a Reference Conditions in European Lakes

The concept of “reference conditions” describes the benchmark against which current conditions are compared when assessing the status of water bodies. In this paper we focus on the establishment of reference conditions for European lakes according to a phytoplankton biomass indicator—the concentration of chlorophyll-a. A mostly spatial approach (selection of existing lakes with no or minor human impact) was used to set the reference conditions for chlorophyll-a values, supplemented by historical data, paleolimnological investigations and modelling. The work resulted in definition of reference conditions and the boundary between “high” and “good” status for 15 main lake types and five ecoregions of Europe: Alpine, Atlantic, Central/Baltic, Mediterranean, and Northern. Additionally, empirical models were developed for estimating site-specific reference chlorophyll-a concentrations from a set of potential predictor variables. The results were recently formulated into the EU legislation, marking the first attempt in international water policy to move from chemical quality standards to ecological quality targets

Male offspring born to mildly ZIKV-infected mice are at risk of developing neurocognitive disorders in adulthood

Congenital Zika virus (ZIKV) syndrome may cause fetal microcephaly in -1% of affected newborns. Here, we investigate whether the majority of clinically inapparent newborns might suffer from long-term health impairments not readily visible at birth. Infection of immunocompetent pregnant mice with high-dose ZIKV caused severe offspring phenotypes, such as fetal death, as expected. By contrast, low-dose (LD) maternal ZIKV infection resulted in reduced fetal birth weight but no other obvious phenotypes. Male offspring born to LD ZIKV-infected mothers had increased testosterone (TST) levels and were less likely to survive in utero infection compared to their female littermates. Males also presented an increased number of immature neurons in apical and basal hippocampal dendrites, while female offspring had immature neurons in basal dendrites only. Moreover, male offspring with high but not very high (storm) TST levels were more likely to suffer from learning and memory impairments compared to females. Future studies are required to understand the impact of TST on neuropathological and neurocognitive impairments in later life. In summary, increased sex-specific vigilance is required in countries with high ZIKV prevalence, where impaired neurodevelopment may be camouflaged by a healthy appearance at birth.Peer reviewe

Seasonal and regional controls of phytoplankton production along a climate gradient in south-west greenland during ice-cover and ice-free conditions

Across a small geographic area (< 180 km), the region of South West Greenland covers a natural climate gradient. Variation in temperature and precipitation result in marked differences in limnology at three discrete locations: ice sheet margin, inland and the coast. Replicate lakes from each location were sampled for physical (temperature, light), chemical (dissolved oxygen, pH, conductivity, nutrients) and biological (chlorophyll a (Chl a), photosynthetic pigments) variables on three occasions within a 12 month period: July - August 2010, April - May 2011 and June - July 2011 spanning ice cover. Variation in ice phenology was linked to the climate gradient; however phytoplankton production and community composition did not differ regionally. Large-scale seasonal fluctuations in temperature and nutrient availability were the strongest predictors of phytoplankton production, with a shift from nitrate to phosphorus controlled production between ice cover and ice free conditions. Underlying seasonal drivers, variables predicting production were unique to each location: ice sheet margin (soluble reactive phosphorus), inland (temperature) and coast (silicate) and reflect local differences in nutrient availability. Results from the current study have important consequences when controls over phytoplankton production in Arctic lakes are inferred from a limited number of sites, but up-scaled to represent pan-Arctic trends