Atmospheric stilling leads to prolonged thermal stratification in a large shallow polymictic lake

To quantify the effects of recent and potential future decreases in surface wind speeds on lake thermal stratification, we apply the one-dimensional process-based model MyLake to a large, shallow, polymictic lake, Võrtsjärv. The model is validated for a 3-year period and run separately for 28 years using long-term daily atmospheric forcing data from a nearby meteorological station. Model simulations show exceptionally good agreement with observed surface and bottom water temperatures during the 3-year period. Similarly, simulated surface water temperatures for 28 years show remarkably good agreement with long-term in situ water temperatures. Sensitivity analysis demonstrates that decreasing wind speeds has resulted in substantial changes in stratification dynamics since 1982, while increasing air temperatures during the same period had a negligible effect. Atmospheric stilling is a phenomenon observed globally, and in addition to recent increases in surface air temperature, needs to be considered when evaluating the influence of climate change on lake ecosystems

Temperature dependence of oxygen dynamics and community metabolism in a shallow Mediterranean macroalgal meadow (caulerpa prolifera)

Hypoxia is emerging as a major threat to marine coastal biota. Predicting its occurrence and elucidating the driving factors are essential to set successful management targets to avoid its occurrence. This study aims to elucidate the effects of warming on the likelihood of hypoxia. Highfrequency dissolved oxygen measurements have been used to estimate gross primary production (GPP), net ecosystem production (NEP) and community respiration (CR) in a shallow macroalgae (Caulerpa prolifera) ecosystem in a highly human-influenced closed Mediterranean bay. Daily averaged GPP and CR ranged from 0 to 1,240.9 and 51.4 to 1,297.3 mmol O2 m−2 day−1, respectively. The higher GPP and CRwere calculated for the same day, when daily averaged water temperature was 28.3 °C, and resulted in a negative NEP of −56.4 mmol O2 m−2 day−1. The ecosystem was net heterotrophic during the studied period, probably subsidized by allochthonous organic inputs from ground waters and from the surrounding town and boating activity. Oxygen dynamics and metabolic rates strongly depend on water temperature, with lower oxygen content at higher temperatures. The probability of hypoxic conditions increased at a rate of 0.39%°C−1 (±0.14 % °C−1). Global warming will increase the likelihood of hypoxia in the bay studied, as well as in other semienclosed bays

Profound daily vertical stratification and mixing in a small, shallow, wind-exposed lake with submerged macrophytes

Mixing and stratification patterns in lakes are critical attributes because they are important regulators of distribution of gases, solutes and organisms. While numerous studies have focused on mixing and stratification in large lakes, the ecology and hydrodynamics of small lakes remain grossly understudied. This is critical because small lakes are far more abundant than large lakes globally. We studied a small (<1000 m2) and shallow (<0.6 m) lake with clear water and dense submerged charophyte stands located on Öland, SE Sweden, between March 25th and May 29th to investigate the thermal regimes, surface heat fluxes and stratification and mixing processes. Daytime vertical temperature differences developed in the water column ranging from 3 °C in March to 15 °C in May. Cooling of surface waters led to full convective mixing of the water column each night. The lake shallowed from March to May. The largest temperature differences were recorded in the early afternoon although wind speeds were highest at this time. The dense charophyte cover rapidly attenuated depth penetration of wind-induced mixing and radiative fluxes. Dense macrophyte stands can engineer their own environment by facilitating build-up of steep temperature and chemical gradients. This interaction should have implications for small lakes worldwide

Cysteamine revisited: repair of arginine to cysteine mutations.

Cysteamine is a small aminothiol endogenously derived from coenzyme A degradation. For some decades, synthetic cysteamine has been employed for the treatment of cystinosis, and new uses of the drug continue to emerge. In this review, we discuss the role of cysteamine in cellular and extracellular homeostasis and focus on the potential use of aminothiols to reconstitute the function of proteins harboring arginine (Arg) to cysteine (Cys) mutations, via repair of the Cys residue into a moiety that introduces an amino group, as seen in basic amino acid residues Lys and Arg. Cysteamine has been utilized in vitro and ex vivo in four different genetic disorders, and thus provides "proof of principle" that aminothiols can modify Cys residues. Other aminothiols such as mercaptoethylguanidine (MEG) with closer structural resemblance to the guanidinium moiety of Arg are under examination for their predicted enhanced capacity to reconstitute loss of function. Although the use of aminothiols holds clinical potential, more studies are required to refine specificity and treatment design. The efficacy of aminothiols to target proteins may vary substantially depending on their specific extracellular and intracellular locations. Redox potential, pH, and specific aminothiol abundance in each physiological compartment are expected to influence the reactivity and turnover of cysteamine and analogous drugs. Upcoming research will require the use of suitable cell and animal models featuring Arg to Cys mutations. Since, in general, Arg to Cys changes comprise about 8% of missense mutations, repair of this specific mutation may provide promising avenues for many genetic diseases.QNR