Sulfur cycling in the water column of Lake Kinneret with emphasis on the triple sulfur isotope (delta S-32, delta S-33, delta S-34) fractionation between sulfate and hydrogen sulfide was investigated. In addition to providing quantitative constraints, the triple sulfur isotope composition of sulfur species in a stratified waterbody offers insights into sulfur cycling in the ancient oceans. Another goal of this work was to evaluate the rates and mechanisms of hydrogen sulfide oxidation during mixing of the lake water column. To achieve these goals, 5 sampling campaigns were conducted to measure temperature, pH, and concentrations of oxygen and sulfur species, along with the triple isotope composition of hydrogen sulfide and sulfate. We found that the value of isotopic fractionation between sulfate and hydrogen sulfide increases from the early stratification in spring to the advanced stages of stratification in autumn, reaching & varepsilon;S-34 = -34 +/- 4 parts per thousand in November. The combination of delta S-34 and delta S-33 values suggests that the extent of recycling of hydrogen sulfide through disproportionation of zero-valent sulfur increases in summer because of its phototrophic oxidation of hydrogen sulfide and further increases in autumn because of mixing of sulfidic and oxic waters. After the lake water column is fully mixed, hydrogen sulfide is fully oxidized in <60 h. This observation agrees with kinetic calculations and suggests that dissolved Fe(II) and Mn(II) are present at concentrations high enough to catalyze oxidation of hydrogen sulfide.
Glossogobius olivaceus is an economically valuable euryhaline goby species that typically inhabits estuarine ecosystems in Vietnam with well-developed mangrove forests. Notably, its occurrence in freshwater habitats devoid of mangrove influence indicates substantial ecological plasticity. The length-weight relationship (LWR) and condition factor (K) are key metrics for assessing growth patterns, population status, and understanding how environmental conditions support the survival and development, along with how this species adapts with the surrounding environment. In the LWR equation (W = aL(b)), b indicates growth pattern (b = 3, isometric; b > 3, positive allometry; b < 3, negative allometry). This study aimed to examine the growth characteristics and condition factors among sexes and seasons of G. olivaceus in the freshwater section of the Thuong River (Bac Ninh Province) throughout a year. We collected 1251 individuals from August 2024 to July 2025. The female to male ratio was 1:1.25, indicating a male-biased sex ratio in the catch. Overall, G. olivaceus exhibited positive allometric growth in freshwater, with weight increasing faster than length (b = 3.144, P < 0.05); b values were higher in females (3.246) than in males (3.105), and greater in the rainy season (3.214) than the dry season (3.043), with P < 0.05 for all cases. The condition factor remained stable (K approximate to 1.00, P > 0.05). These results demonstrate that G. olivaceus is well adapted to freshwater environments and provide essential baseline information for population assessment, conservation, and sustainable fisheries management in inland waters of northern Vietnam.
