Проснись и погибни: влияние солёности на продуктивность популяций Moina macrocopa (Straus, 1820) (Cladocera: Moinidae), инициированных самками, вышедшими из покоящихся яиц

Freshwater salinization may have important implications for the abundance and diversity of zooplankton, which play a key role in the functioning of aquatic ecosystems. Many of these animals undergo developmental arrest in the embryonic stage, which allows them to survive harsh periods and cope with seasonal unfavorable environmental conditions. We studied the effects of salinity in the experiments with individuals and populations of the cladoceran Moina macrocopa on the life history traits and population parameters important for cyclical development of animals: the hatching success of resting eggs; the survival of hatchlings; individual performance of post- diapause females and performance of populations initiated by post- diapause females. We observed a decreasing sequence of salinities critical for traits and parameters studied in this work: from 8 g L -1, critical for hatching of resting eggs, to 1 g L-1, critical for the ability of a population initiated by post- diapause females to produce resting eggs. We conclude that the relatively low salinity (1 g L-1) that does not suppress the hatching of resting eggs reduces the ecologically significant ability of the M. macrocopa populations to replenish the bank of resting eggs. Thus, freshwater salinization, in the long term, will prevent the re-establishment of M. macrocopa and most probably other freshwater cladoceran populations from the banks of resting eggsЗасоление пресноводных экосистем может привести к значимым последствиям для численности и разнообразия зоопланктона, который играет ключевую роль в функционировании водных экосистем. Многие представители зоопланктона обладают способностью к задержке развития на стадии эмбриона, что позволяет им переживать суровые периоды существования и справляться с сезонными неблагоприятными условиями окружающей среды. Мы изучили влияние солёности в экспериментах с отдельными особями и популяциями ветвистоусого рачка Moina macrocopa на параметры их жизненного цикла и популяционные характеристики, обладающие значимостью для циклического развития животных: успешность реактивации покоящихся яиц; выживаемость вылупившихся рачков; продуктивность отдельных самок, вышедших из покоящихся яиц и продуктивность популяций, инициированных самками после диапаузы. Мы обнаружили повышение порога чувствительности изучаемых параметров к солёности: от 8 г/л – критической солености для вылупления покоящихся яиц, до 1 г/л – критической солёности для способности популяции, инициированной самками, вышедшими из яиц после диапаузы, производить покоящиеся яйца. Мы заключили, что сравнительно низкая солёность (1 г/л), которая не влияла на эффективность реактивации покоящихся яиц, негативно воздействует на экологически значимую способность популяций M. macrocopa пополнять банк покоящихся яиц. Таким образом, засоление пресных вод в долгосрочной перспективе будет препятствовать восстановлению популяций рачков M. macrocopa и, скорее всего, других популяций пресноводных ветвистоусых ракообразных из банков покоящихся яи

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

The Effect of Food Concentration on the Juvenile Somatic Growth Rate of Body Length, Fecundity and the Production of Resting Eggs by Moina brachiata (Crustacea: Cladocera) Single Females

Работа посвящена изучению действия концентрации одноклеточной водоросли Chlorella vulgaris на параметры жизненного цикла самок M. brachiata (длина тела, удельная ювенильная соматическая скорость роста, количество потомков, количество самок, образующих эфиппиальные яйца). Наименьшая концентрация корма, используемая в эксперименте, 100 тысяч клеток/мл, оказывала лимитирующее действие на размер самок в период появления первого потомства, ювенильную соматическую скорость роста и плодовитость; также данная концентрация пищи вызывала образование покоящихся яиц у самок. При увеличении концентрации корма, размер самок в период появления первого потомства, их соматическая скорость роста и плодовитость возрастали, а количество самок, образующих эфиппиумы, снижалось. При культивировании с использованием максимальных тестируемых концентраций пищи (400 и 800 тысяч клеток/мл) размер самок в период появления первого потомства, соматическая скорость роста и количество появившихся потомков были наибольшими, при этом ни одна из самок в эксперименте не образовывала покоящихся яиц. Мы также исследовали действие концентрации пищи, при котором содержалось материнское поколение на способность их потомков формировать латентные яйца. Отсутствие эфиппиумов наблюдалось только при использовании наибольших концентраций пищи в экспериментах для материнских особей и их потомков (400 тысяч клеток/мл). Таким образом, мы предполагаем, что обеспеченность пищей выше 400 тысяч клеток/мл благоприятна для партеногенетического размножения самок M. brachiata. Результаты об уровне пищевой обеспеченности, вызывающей формирование покоящихся яиц у самок M. brachiata, получены впервые.The study addresses the effect of different food concentrations of green alga Chlorella vulgaris on the life cycle parameters (the body length, specific juvenile somatic growth rate of body length, the number of offspring in the first clutch of parthenogenetic females and the number of females producing resting eggs) of the individually cultivated females of M. brachiata. The lowest food concentration used in the experiment, 100 thousand cells/ml, had a limiting effect on such parameters as the size of females at the first reproduction, juvenile somatic growth rate of body length and fecundity; it also induced the production of resting eggs by females. With food concentration increase, the size of females at the first reproduction, their somatic growth rate of body length and fecundity also increased, and the number of females that produced resting eggs decreased. Under maximal food concentrations (400 and 800 thousand cells/ml) the size of females at the first reproduction, the somatic growth rates of body length and the number of hatched offspring were the largest, and there were no females producing ephippial eggs. We also tested the effect of food concentration under which the maternal generation was kept on the ability of the offspring generation to produce resting eggs. The production of resting eggs failed to occur only at the highest food concentrations for maternal females and their offspring (400 thousand cells/ml). Thus, we concluded that food concentration above 400 thousand cells/ml is favorable concentration for parthenogenetic reproduction of M. brachiata. Since there are no literature data on what food concentration induces the production of resting eggs for this species, the results define the trophic conditions that induce production of resting eggs in M. brachiata

Biological and Ecological Features, Trophic Structure and Energy Flow in Meromictic Lakes

Case studies and typical examples for meromictic lakes are used to provide a review of the biology and ecology of these ecosystems. Water column in meromictic lakes is not entirely mixed. These lakes are chemically and/or thermally stratified for several years and have several specific ecological features. The chemocline —the habitat created between the mixolimnion on top and monimolimnion below—is characterised by the existence of complex bacterial communities, autotrophic and heterotrophic protists and metazooplankton, commonly dominated by rotifers , high rates of oxygenic and anoxygenic photosynthesis and some biogeochemical processes . In these lakes, the sulphur, carbon and nitrogen cycles are partially coupled. However, a large number of bacterial and archaeal taxa, especially in anoxic waters, are still unidentified. An unaccomplished important task is to both investigate the uncultivated microbial diversity and access metabolic potential of the bacterial communities in meromictic lakes. The different components of the chemocline communities represent the ingredients of microbial loop that probably links the production of organic matter in anoxic waters with the classical grazer food web . However, in most of such lakes, the food web is not quite quantified. The classical grazer food web in meromictic lakes is often truncated, especially because fish and other predators are often absent. Meromixis has several effects on the grazer food web. First, the lack of mixing favours the loss of nutrients into the monimolimnion, which thus controls nutrient availability and the development of the phytoplankton . Because there is virtually no annual mixing in meromictic lakes, spring algal blooms can be less pronounced. The anoxic monimolimnion prevents zooplankton from vertical migrations that change the nature of food web interactions. The relatively large size of the monimolimnion and prevailing anoxic conditions adversely affect the biota. With the development of anoxic monimolimnion, the size of the photic and aerobic zones decreases, benthic community is altered and habitat for zooplankton and fish is reduced. The zooplankton community in meromictic lakes varies in the species composition and abundance. Depending on salinity and chemical composition of the mixolimnion, the zooplankton may include certain typical cladocerans and copepods . If the salinity increases, the zooplankton can shift to Artemia dominated community, typical of hypersaline lakes. Concluding, complex trophic links, coupling of nutrients cycles and anoxic and oxic food web components are peculiar features that make meromictic lakes natural laboratories to study the complexity of the food webs and biological interactions

Conclusion: Ecology of Meromictic Lakes

The term meromixis was introduced more than 80 years ago to denote lakes that do not annually mix completely. Since then our understanding of meromictic lakes has considerably advanced. Physical processes support the difference in water density between deep (monimolimnion ) and surface (mixolimnion ) waters in meromictic lakes; such lakes reveal complex biogeochemical interactions that contribute to the maintenance of meromixis. This Conclusion chapter of the book on Ecology of Meromictic Lakes presents the general overview of physical, chemical and biological properties of meromictic lakes, based partly on the foregoing 12 chapters. The broad spectrum of meromixis supported by different processes in lakes located in different regions and climates is presented. We stress the importance of undisturbed sediments in meromictic lakes as paleolimnological archives and demonstrate how this information can be used to reconstruct lake history and development over longer time periods. The effects of switch from holomictic to meromictic regime and vice versa on the food web and biological community are demonstrated by some of the case study lakes. However, we do not have the mathematical or modeling tools to understand all the causal factor for processes that switch the mixing regimes of lakes. Man-made meromictic lakes (pit lakes) can be used as lake management tools to control water quality in lakes . We discuss that numerical simulations and model forecasts are important tools to predict the mixing regimes in both man-made and natural meromictic lakes. Biogeochemical reactions play important role in cycling of nutrients in meromictic lakes. Both anoxygenic photosynthesis and chemolithoautotrophy are exceptionally important for fixation of inorganic carbon in organic matter in meromictic lakes. These carbon fixation activities link the carbon cycle with the sulphur, nitrogen and iron cycles. Studies of meromictic lakes—aquatic systems where physics, biogeochemistry and ecology interact intensively—give us new insights into the limnology of inland lakes

Introduction: Meromictic Lakes, Their Terminology and Geographic Distribution

We start with the recent developments and reasons why the meromictic lakes should get more attention in limnological literature. Thereafter, we define monimolimnion , mixolimnion and some other terms related to meromixis. The definition of Hutchinson for meromictic lakes holds for more than 60 years while some modification is required. We differentiate between a meromictic lake and a non-meromictic ones, despite the fact that for deep waters the patterns of recirculation in non-meromictic lakes may be similar to meromixis. We also refer briefly to the classification schemes of meromixis and list processes involved in sustaining stratification. Regions on the Globe that produce salinity gradients in surface waters; mining areas, where geochemistry is more actively operative; and areas where waters of different compositions meet may promote the development of such conditions in lakes. Meromixis is a much more dynamic process than it is often understood. If monimolimnion gets eroded, the meromixis can terminate, while changes in the hydrology can turn a lake meromictic. Finally, we briefly introduce here the structure of this book, which has three parts. Part I focuses on physical (Chap. 2), chemical (Chap. 3) and biological (Chap. 4) properties of meromictic lakes. Part II presents eight case studies in separate chapters including the regional studies on different meromictic lakes in five continents. Part III (Chap. 13) is based mainly on the brief conclusion summaries derived from the preceding 12 chapters with editors’ remarks. Lastly, this book is an attempt to update our available knowhow and expertise on the existing state-of-the-art information on meromictic lakes and the literature references that can form the basis for future studies on meromictic lakes

The Effect of Food Concentration on the Juvenile Somatic Growth Rate of Body Length, Fecundity and the Production of Resting Eggs by Moina brachiata (Crustacea: Cladocera) Single Females

Работа посвящена изучению действия концентрации одноклеточной водоросли Chlorella vulgaris на параметры жизненного цикла самок M. brachiata (длина тела, удельная ювенильная соматическая скорость роста, количество потомков, количество самок, образующих эфиппиальные яйца). Наименьшая концентрация корма, используемая в эксперименте, 100 тысяч клеток/мл, оказывала лимитирующее действие на размер самок в период появления первого потомства, ювенильную соматическую скорость роста и плодовитость; также данная концентрация пищи вызывала образование покоящихся яиц у самок. При увеличении концентрации корма, размер самок в период появления первого потомства, их соматическая скорость роста и плодовитость возрастали, а количество самок, образующих эфиппиумы, снижалось. При культивировании с использованием максимальных тестируемых концентраций пищи (400 и 800 тысяч клеток/мл) размер самок в период появления первого потомства, соматическая скорость роста и количество появившихся потомков были наибольшими, при этом ни одна из самок в эксперименте не образовывала покоящихся яиц. Мы также исследовали действие концентрации пищи, при котором содержалось материнское поколение на способность их потомков формировать латентные яйца. Отсутствие эфиппиумов наблюдалось только при использовании наибольших концентраций пищи в экспериментах для материнских особей и их потомков (400 тысяч клеток/мл). Таким образом, мы предполагаем, что обеспеченность пищей выше 400 тысяч клеток/мл благоприятна для партеногенетического размножения самок M. brachiata. Результаты об уровне пищевой обеспеченности, вызывающей формирование покоящихся яиц у самок M. brachiata, получены впервые.The study addresses the effect of different food concentrations of green alga Chlorella vulgaris on the life cycle parameters (the body length, specific juvenile somatic growth rate of body length, the number of offspring in the first clutch of parthenogenetic females and the number of females producing resting eggs) of the individually cultivated females of M. brachiata. The lowest food concentration used in the experiment, 100 thousand cells/ml, had a limiting effect on such parameters as the size of females at the first reproduction, juvenile somatic growth rate of body length and fecundity; it also induced the production of resting eggs by females. With food concentration increase, the size of females at the first reproduction, their somatic growth rate of body length and fecundity also increased, and the number of females that produced resting eggs decreased. Under maximal food concentrations (400 and 800 thousand cells/ml) the size of females at the first reproduction, the somatic growth rates of body length and the number of hatched offspring were the largest, and there were no females producing ephippial eggs. We also tested the effect of food concentration under which the maternal generation was kept on the ability of the offspring generation to produce resting eggs. The production of resting eggs failed to occur only at the highest food concentrations for maternal females and their offspring (400 thousand cells/ml). Thus, we concluded that food concentration above 400 thousand cells/ml is favorable concentration for parthenogenetic reproduction of M. brachiata. Since there are no literature data on what food concentration induces the production of resting eggs for this species, the results define the trophic conditions that induce production of resting eggs in M. brachiata