A Cautionary Note: Ceriodaphnia dubia Inter-Laboratory Test Variability.

An inter-laboratory comparison of the three-brood survival and reproduction Ceriodaphnia dubia toxicity test was conducted involving three toxicity testing laboratories. This comparison was initiated due to sporadic toxicity with this test related to discharge of a mine effluent, which some regulators believed indicated adverse effects in the receiving environment. One mine effluent and two receiving water samples were evaluated. There were no adverse effects on C. dubia survival in any tests. However, sublethal effects on reproduction (i.e., the IC25; the concentration that causes a 25 % inhibitory effect in the measured sublethal endpoint) ranged from 35 % to >100 % among all test treatments. All laboratories were certified for this test and followed established procedures. Dilute mineral water appears to be the best medium for culturing, dilution, and control water. Variability in the C. dubia laboratory toxicity test should not be mistaken for adverse effects in receiving environments.

Global data set of long-term summertime vertical temperature profiles in 153 lakes.

Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of lake thermal structure in a time of rapid global and ecological change.