Experimental evidence on the effects of temperature and salinity in morphological traits of the Microcystis aeruginosa complex.

Microcystis aeruginosa complex (MAC) encompasses noxious colonial bloom forming cyanobacteria. MAC representatives bloom in eutrophic freshwater and brackish ecosystems with stagnant water, were temperature and salinity are the main variables modulating their distribution, biomass and toxicity. Cell abundance and biovolume of MAC colonies define regulatory standards for public health. These variables depend upon colony size that in turn changes with environmental conditions. Here, we conducted two series of experiments to evaluate the response of MAC colonies morphological traits (length, volume, mucilage and number of cells) to temperature and salinity. In two series of experiments in the laboratory, we exposed natural MAC communities to three different temperatures (10, 21 and 30 °C) and four salinity levels (0, 5, 10 and 25 ppt) typically found in estuaries. We found that average colony length, volume and mucilage thickness did not change with temperature, but the cell-free space inside the colonies was smaller at the highest evaluated temperature (30 °C). Salinity fostered an increase in colony length, volume and mucilage thickness, while cell-free space diminished, resulting in higher cell density. The number of cells per colony was significantly related to colony size (length and volume) and both, temperature and salinity, affected the parameters of the relationships. Based on present results we propose statistical models to predict cell number per colony based on length and volume and accounting for the effect of salinity and temperature on these traits. This is applicable to ecological studies and to the monitoring of estuarine aquatic environments, by means of a fast and more accurate estimation of cell numbers to define MAC toxic populations early warning systems. A protocol is suggested for its application while the analysis of the interaction of temperature and salinity, as well as the variability in natural environments are objectives for future researches.

Geographic health inequalities in Norway: a Gini analysis of cross-county differences in mortality from 1980 to 2014.

BACKGROUND: This study aims at quantifying the level and changes over time of inequality in age-specific mortality and life expectancy between the 19 Norwegian counties from 1980 to 2014. METHODS: Data on population and mortality by county was obtained from Statistics Norway for 1980-2014. Life expectancy and age-specific mortality rates (0-4, 5-49 and 50-69 age groups) were estimated by year and county. Geographic inequality was described by the absolute Gini index annually. RESULTS: Life expectancy in Norway has increased from 75.6 to 82.0 years, and the risk of death before the age of 70 has decreased from 26 to 14% from 1980 to 2014. The absolute Gini index decreased over the period 1980 to 2014 from 0.43 to 0.32 for life expectancy, from 0.012 to 0.0057 for the age group 50-69 years, from 0.0038 to 0.0022 for the age group 5-49 years, and from 0.0009 to 0.0006 for the age group 0-4 years. It will take between 2 and 32 years (national average 7 years) until the counties catch up with the life expectancy in the best performing county if their annual rates of increase remain unchanged. CONCLUSION: Using the absolute Gini index as a metric for monitoring changes in geographic inequality over time may be a valuable tool for informing public health policies. The absolute inequality in mortality and life expectancy between Norwegian counties has decreased from 1980 to 2014.