Рост пурпурных серных бактерий Thiocapsa sp. Shira_1 при низких температурах, характерных для хемоклина озера Шира

Forecasting the abundance of phototrophic sulfur bacteria in lakes is very important because 1) these bacteria are major consumers of hydrogen sulfide, and 2) fossil carotenoids of these bacteria are retrospective biomarkers of limnological conditions. Therefore, understanding the factors controlling the dynamics of the abundance of phototrophic sulfur bacteria in a lake is necessary both for the prediction of hydrogen sulfide content and for paleo-limnological reconstruction. Based on long-term monitoring of the abundance of purple sulfur bacteria (PSB) in the saline meromictic Lake Shira (South Siberia, Khakassia), we proposed a hypothesis that relatively small changes in water temperature in the cold deep chemocline affect the PSB abundance in the lake. We tested this hypothesis experimentally. The purple sulfur bacterium Thiocapsa sp. Shira_1 (Chromatiaceae) from Lake Shira (South Siberia, Russia) was grown on a sulfide-containing synthetic medium under anoxic conditions in batch culture at low temperatures, from -1ºC to +8ºC, which were similar to in situ temperatures observed in the chemocline of Lake Shira. The cell growth rate at +8ºC was similar to the growth rate at room temperature, whereas there was no growth at -1ºC and +5ºC. Therefore, the variations in the biomass of purple sulfur bacteria (PSB) observed in Lake Shira could be caused by variations in chemocline temperature. The high correlation between chemocline temperature and PSB biomass supported this conclusionПрогноз динамики численности фототрофных серных бактерий в природных стратифицированных водоемах признан важной задачей. Во-первых, данная группа бактерий – основной потребитель сероводорода, который является токсическим и бальнеологическим компонентом. Во-вторых, каротиноиды фототрофных серных бактерий, захороненные в донных отложениях, используются в качестве биомаркеров прошлых состояний озера. Таким образом, знание факторов, контролирующих активность фототрофных серных бактерий, необходимо как для прогноза концентрации сероводорода, так и для палеоклиматических реконструкций. На основе многолетних наблюдений за динамикой численности пурпурных серных бактерий (ПСБ) в соленом меромиктическом озере Шира (юг Сибири, Хакасия) нами была выдвинута гипотеза о том, что небольшие вариации температуры воды в холодном и глубоком хемоклине озера влияют на численность ПСБ. Для проверки этой гипотезы нами исследован рост штамма пурпурных серных бактерий Thiocapsa sp. Shira_1 из меромиктического соленого озера Шира в периодической культуре при температурах от минус 1 до 8 °С, характерных для зоны хемоклина данного озера. Бактерий выращивали при постоянном освещении в анаэробных условиях на синтетической среде с добавлением сероводорода. Показано, что рост данного штамма при 8 °С не отличался от такового при комнатной температуре, тогда как при температурах минус 1 и 5 °С достоверный рост отсутствовал. Результаты эксперимента свидетельствуют, что повышение температуры в зоне хемоклина озера до 8 °С является фактором, способствующим увеличению численности популяции этих бактерий в озере, что согласуется с многолетними наблюдениям

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

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

Measurement(s) : temperature of water, temperature profile Technology Type(s) : digital curation Factor Type(s) : lake location, temporal interval Sample Characteristic - Environment : lake, reservoir Sample Characteristic - Location : global Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.14619009Climate 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

Hydraulically-operated Thin-layer Sampler for Sampling Heterogeneous Water Columns

A necessary condition for investigating microbial communities in chemocline zones of stratified waterbodies is high-precision sampling at a depth resolution of several centimeters. We have modified a multi-syringe sampler that is conventionally used by researchers for this purpose. The main distinctive feature of our sampler is that plungers are operated hydraulically rather than pneumatically and, thus, our sampler has the following advantages: (1) the plungers cannot move spontaneously, which ensures sampling adequacy, especially in deep-water sampling; (2) filling of the syringes with the sample can be monitored from a distance; (3) during storage, the internal volume of the syringe and the whole hydraulic system is aseptic (if 70% ethanol is used as a working fluid), which is important if samples are to be used for microbiological tests. (4) the problem of sticking plungers is minimized, even after extended storage. Vertical sampling of the chemocline zones of meromictic lakes in Southern Siberia (Russia, Khakasia) at a depth resolution of 5 cm proves that the sampler is very reliable and simple to use

Hydraulically-operated Thin-layer Sampler for Sampling Heterogeneous Water Columns

A necessary condition for investigating microbial communities in chemocline zones of stratified waterbodies is high-precision sampling at a depth resolution of several centimeters. We have modified a multi-syringe sampler that is conventionally used by researchers for this purpose. The main distinctive feature of our sampler is that plungers are operated hydraulically rather than pneumatically and, thus, our sampler has the following advantages: (1) the plungers cannot move spontaneously, which ensures sampling adequacy, especially in deep-water sampling; (2) filling of the syringes with the sample can be monitored from a distance; (3) during storage, the internal volume of the syringe and the whole hydraulic system is aseptic (if 70% ethanol is used as a working fluid), which is important if samples are to be used for microbiological tests. (4) the problem of sticking plungers is minimized, even after extended storage. Vertical sampling of the chemocline zones of meromictic lakes in Southern Siberia (Russia, Khakasia) at a depth resolution of 5 cm proves that the sampler is very reliable and simple to use

Measuring Alloxanthin as a Proxy Approach in a Study of Trophic Relationships between Zooplankton and Cryptophyte Algae in Lake Shira

Криптофитовые водоросли признаны важным трофическим звеном многих водных экосистем, однако остаются недостаточно изученными в плане трофических взаимодействий с другими компонентами экосистем. Они являются более качественной пищей, чем большинство других водорослей, и поэтому могут быть подвержены селективному выеданию со стороны зоопланктона. Следовательно, прямые измерения динамики их концентрации в озерах могут давать очень сильно заниженные показатели продукции. Одним из способов оценки потребления криптофитовых водорослей зоопланктоном служит определение содержания в нем специфического для криптомонад каротиноида аллоксантина. В работе исследовалось содержание аллоксантина в осадочных илах, седиментационных ловушках и зоопланктоне озера Шира с помощью высокоэффективной жидкостной хроматографии. Была показана значимая корреляция между количеством некоторых видов зоопланктона, способных потреблять криптофитовые водоросли, и потоком осаждаемого аллоксантина, зафиксированным в седиментационных ловушках. Результат анализа проб зоопланктона (наибольший вклад в биомассу которого обеспечивал веслоногий рачок Arctodiaptomus salinus (Daday, 1885)) на содержание каротиноидов в течение весенне-летнего сезона показал наличие аллоксантина в количестве до 80 мкг/г, снижающееся к концу сезона, что коррелировало с биомассой криптофитовых водорослей в озере. Каротиноиды, ассоциированные с другими группами водорослей, наблюдались в значительно меньшем количестве. Это демонстрирует высокий уровень селективного потребления веслоногим рачком A.salinus криптофитовых водорослей и может служить подтверждением тесной трофической связи между нимиCryptophyte algae are an important trophic link in many aquatic ecosystems, but they remain insufficiently studied in terms of trophic interactions with other components of ecosystems. They are better quality food than most other algae and, therefore, can be subject to selective grazing by zooplankton; thus, direct measurements of the dynamics of their concentration in lakes may give very low productivity indicators. One way to assess the consumption of cryptophyte algae by zooplankton is to determine the content of alloxanthin, a carotenoid specific for cryptophyte algae, in zooplankton. The present study investigated the alloxanthin content of sedimentary silts, sedimentation traps, and zooplankton of Lake Shira using high performance liquid chromatography. A significant correlation was found between the abundance of some zooplankton species capable of consuming cryptophyte algae and the flux of precipitated alloxanthin recorded in sedimentation traps. Analysis of zooplankton samples (the largest contribution to the biomass of which was made by the copepod Arctodiaptomus salinus (Daday, 1885)) for the content of carotenoids during the spring-summer season showed the presence of alloxanthin amounts reaching 80 μg/g, which decreased by the end of the season, and that correlated with the biomass of cryptophyte algae in the lake. Carotenoids associated with other groups of algae were observed in considerably smaller amounts. Thus, the copepod A. salinus exhibits high selective consumption of cryptophyte algae, which may serve as a confirmation of a close trophic relationship between the

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

Abstract 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