Highlights  The General Lake Model (GLM) is stress tested against 32 globally distributed lakes.  There was low correlation between input data uncertainty and model performance.  Model performance related to lake-morphometry, light extinction and flow regime; deep, clear lakes with high residence times had the lowest model error.

No abstract

Planktic foraminiferal Mg/Ca ratios have become a fundamental seawater temperature proxy in past climate reconstructions, due to the temperature dependence of Mg uptake into foraminiferal calcite. However, empirical calibrations for single species from methodologically consistent data are still lacking.Here we present species-specific calibrations of Mg/Ca versus calcification temperature for two commonly used species of planktic foraminifera: Globigerina bulloides and Neogloboquadrina pachyderma left, based on a series of Southern Ocean and North Atlantic core tops. Combining these new data with previously published data, we derive an integrated G. bulloides Mg/Ca-temperature calibration for mid and high latitudes of both hemispheres between 2 and 188C, where Mg/Ca 5 1.006 6 0.032 * e 0.065 6 0.003 * Tiso (R 2 5 0.82). G. bulloides is found to calcify deeper in the Southern Ocean ($ 200 m) than in the North Atlantic (top 50 m). We also propose a Mg/Ca temperature calibration to describe the temperature response in N. pachyderma left that calcified away from the influence of sea ice in the Southern Ocean, valid between $ 21 and 98C, of the form Mg/Ca 5 0.580 6 0.016 * e 0.084 6 0.006*Tiso (R 2 5 0.70). These calibrations account for uncertainties on Mg/Ca measurements and calcification temperature that were carefully estimated and propagated using Monte Carlo iterations. The 1r propagated error in Mg/Ca-derived temperatures is 1.18C for G. bulloides and 0.98C for N. pachyderma left for the presented data sets. Geographical extension of genotypes must be assessed when choosing to develop regional or global calibrations.

Abstract. Density calculations are essential to study stratification, circulation patterns, internal wave formation and other aspects of hydrodynamics in lakes and reservoirs. Currently, the most common procedure is the use of CTD profilers and convert measurements of temperature and electrical conductivity into density. In limnic waters, such approaches are of limited accuracy, if they do not consider lake specific composition of solutes, as we show. A new approach is presented to correlate density and electrical conductivity, using only two specific coefficients based on the composition of solutes. First, it is necessary to evaluate the lake-specific coefficients connecting electrical conductivity with density. Once these coefficients have been obtained, density can easily be calculated based on CTD data. The new method has been tested against measured values and the most common equations used in the calculation of density in limnic and ocean conditions. The results show that our new approach can reproduce the density contribution of solutes with a relative accuracy of 10 % in lake waters from very low to very high concentrations as well as in lakes of very particular water chemistry, which surmounts all commonly implemented density calculations in lakes by far. Finally, we provide a web link for downloading the corresponding density calculator.

Abstract. Density calculations are essential to study stratification, circulation patterns, internal wave formation and other aspects of hydrodynamics in lakes and reservoirs. Currently, the most common procedure is the use of CTD (conductivity, temperature and depth) profilers and the conversion of measurements of temperature and electrical conductivity into density. In limnic waters, such approaches are of limited accuracy if they do not consider lake-specific composition of solutes, as we show. A new approach is presented to correlate density and electrical conductivity, using only two specific coefficients based on the composition of solutes. First, it is necessary to evaluate the lake-specific coefficients connecting electrical conductivity with density. Once these coefficients have been obtained, density can easily be calculated based on CTD data. The new method has been tested against measured values and the most common equations used in the calculation of density in limnic and ocean conditions. The results show that our new approach can reproduce the density contribution of solutes with a relative error of less than 10 % in lake waters from very low to very high concentrations as well as in lakes of very particular water chemistry, which is better than all commonly implemented density calculations in lakes. Finally, a web link is provided for downloading the corresponding density calculator.

A geochemical model was incorporated into a stratification model for lakes to create the model package: DYCD-CORE, a numerical code that couples the thermal and hydrodynamic capabilities of DYRESM and the geochemical capabilities of the reactive transport model CORE 2D V4. Based on the chemical composition of solutes calculated in each node for each time step, density was computed using specific partial molal volumes of all considered solutes and fed back into the stratification module of the program package. The density calculated each time step leads to a strong coupling of hydrodynamics and hydrogeochemistry and reflects the complex interaction as it is present in all lakes. To demonstrate the functionality of the numerical approach, an example of an iron-meromictic lake was chosen, where the reactivity of the dissolved iron kept the water body perennially stratified. To critically validate the model results, temperatures were continously measured at high vertical and temporal resolution in a field investigation of Waldsee (near Döbern, Germany). Multiparameterprobe profiles and water samples confirmed the continous chemical stratification and served as initial and boundary conditions for the simulation period. The model package DYCD-CORE could reproduce the permanent stratification as it were in the lake. A demonstration run using the standard UNESCO equation for density, and hence assuming non-reactive solutes, failed entirely. Hence, stratification models using salinity for density are not suited for simulating density created by lake-internal geochemical transformation of solutes. However, density can be based directly on the simultaneous numerical simulation of lake geochemistry. Predictive modeling of changing lake circulation in a variable climate or considering change of use will require a proper inclusion of the geochemistry as demonstrated in this paper.

Abstract. In the last decades, the mining exploitation of large areas in Lusatia (Eastern Germany) but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH < 3). The biogeochemical functioning of these lakes is mainly governed by cycling of iron. This represents a relevant ecological problem and intensive research has been conducted to understand the involved biogeochemical processes and develop bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macroinvertebrates) under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera) is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O 2 microsensors) was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the diffusive oxygen uptake by sediment, indicating a stimulation of the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation) but with no significant effect on the iron flux at the sediment-water interface, and thus Correspondence to: S. Lagauzère (lagauzere@gmail.com) on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

<b><i>Objective:</i></b> The aim of this study was to investigate the association between rhegmatogenous retinal detachment (RRD) and solar radiation in northwestern Spain. <b><i>Methods:</i></b> All RRD cases in Pontevedra from 2008 and 2014 were retrospectively analyzed. Climatological data from 4 weather stations in the area were collected. The association between RRD incidence and solar radiation was investigated. <b><i>Results:</i></b> A total of 256 RRD cases were identified. There was a seasonal variation in the incidence of RRD with a maximum number of incident cases observed in June and July and a minimum number of cases observed in January and December. An association was found between RRD incidence and solar radiation both monthly (<i>p</i> = 0.004) and bimonthly (<i>p</i> = 0.057). The right eye was more frequently affected than the left eye (<i>p</i> = 0.035). RD cases other than rhegmatogenous showed neither seasonality nor association with radiation. <b><i>Conclusions:</i></b> Solar radiation may play a role in RRD genesis in our area. Laterality could be related to the amount of radiation reaching each eye.