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.

Deeper waters are changing less consistently than surface waters in a global analysis of 102 lakes.

Globally, lake surface water temperatures have warmed rapidly relative to air temperatures, but changes in deepwater temperatures and vertical thermal structure are still largely unknown. We have compiled the most comprehensive data set to date of long-term (1970-2009) summertime vertical temperature profiles in lakes across the world to examine trends and drivers of whole-lake vertical thermal structure. We found significant increases in surface water temperatures across lakes at an average rate of + 0.37 °C decade-1, comparable to changes reported previously for other lakes, and similarly consistent trends of increasing water column stability (+ 0.08 kg m-3 decade-1). In contrast, however, deepwater temperature trends showed little change on average (+ 0.06 °C decade-1), but had high variability across lakes, with trends in individual lakes ranging from - 0.68 °C decade-1 to + 0.65 °C decade-1. The variability in deepwater temperature trends was not explained by trends in either surface water temperatures or thermal stability within lakes, and only 8.4% was explained by lake thermal region or local lake characteristics in a random forest analysis. These findings suggest that external drivers beyond our tested lake characteristics are important in explaining long-term trends in thermal structure, such as local to regional climate patterns or additional external anthropogenic influences.

Autotrophic carbon fixation strategies used by nitrifying prokaryotes in freshwater lakes.

Niche specialization of nitrifying prokaryotes is usually studied with tools targeting molecules involved in the oxidation of ammonia and nitrite. The ecological significance of diverse CO2 fixation strategies used by nitrifiers is, however, mostly unexplored. By analyzing autotrophy-related genes in combination with amoA marker genes based on droplet digitial PCR and CARD-FISH counts targeting rRNA, we quantified the distribution of nitrifiers in eight stratified lakes. Ammonia oxidizing (AO) Thaumarchaeota using the 3-hydroxypropionate/4-hydroxybutyrate pathway dominated deep and oligotrophic lakes, whereas Nitrosomonas-related taxa employing the Calvin cycle were important AO bacteria in smaller lakes. The occurrence of nitrite oxidizing Nitrospira, assimilating CO2 with the reductive TCA cycle, was strongly correlated with the distribution of Thaumarchaeota. Recently discovered complete ammonia-oxidizing bacteria (comammox) belonging to Nitrospira accounted only for a very small fraction of ammonia oxidizers (AOs) present at the study sites. Altogether, this study gives a first insight on how physicochemical characteristics in lakes are associated to the distribution of nitrifying prokaryotes with different CO2 fixation strategies. Our investigations also evaluate the suitability of functional genes associated with individual CO2 assimilation pathways to study niche preferences of different guilds of nitrifying microorganisms based on an autotrophic perspective.

Bodywork as systemic and inter-enactive competence: participatory process management in Feldenkrais® Method and Zen Shiatsu.

Feldenkrais and Shiatsu enable somatic learning through continuous tactile coupling, a real-time interpersonal dynamic unfolding in a safe dyadic sphere. The first part of our micro-ethnographic study draws on process vignettes and subjective theories to demonstrate how bodywork is infused with systemic sensitivities and awareness for non-linear process management. Expressed in dynamic systems parlance, both disciplines foster metastability, adaptivity, and self-organization in the client's somato-personal system by progressively reconfiguring systemic dispositions, i.e., an attractor landscape. Doing so requires a keen embodied apperception of hierarchies of somato-systemic order. Bodyworkers learn to explore these in their eigenfunction (joints, muscles, fascia), discriminate coordinative organization in small ensembles, and monitor large-scale dynamic interplay. The practitioner's "extended body" reaching forth into the client's through a resonance loop eventually becomes part of this. Within a bodywork session, practitioners modulate this hierarchical functional architecture. Their ability for sensorially staying apace of systemic emergence allows them to respond to minute changes and customize reactions in a zone of proximal development (dynamic immediacy). They stimulate the client's system with a mix of perturbing and stabilizing interventions that oscillate between eigenfunctions and their coordinative integration. Practical knowledge for "soft-assembling" non-linear synergies is crucial for this (cumulative local effects, high-level functions "slaving" the system, etc.). The paper's second part inventorizes the bodyworker's operative tool-box-micro-skills providing the wherewithal for context-intelligent intervention. Practitioners deploy "educated senses" and a repertoire of hands-on techniques (grips, stretches, etc.) against a backdrop of somatic habits (proper posture, muscle activation, gaze patterns, etc.). At this level, our study addresses a host of micro-skills through the lens of enactive cognitive science.

Hang on or run? Copepod mating versus predation risk in contrasting environments.

Mating durations of copepods were found to differ significantly between fishless high-altitude waters and lowland lakes containing fish. In lowland species the whole mating process was completed within a few minutes, but it averaged over an hour in high-altitude species. Alpine copepods showed a prolonged post-copulatory association between mates, during which the male clasped the female for an extended period after spermatophore transfer, while in lowland species males abandoned their partner immediately after copulation. Prolonged associations also occurred after transfer of spermatophores to heterospecific females with shorter conspecific mating duration, suggesting that male interests largely dictate the time spent in tandem. The differences observed may be adaptations to environments with different predation pressure, as pairs in tandem are more conspicuous and less reactive than single animals. We argue that differences in mating behavior and mating duration evolved under sexual versus natural selection, reflecting trade-offs between enhancement of fertilization success and reduction of vulnerability to visual predation. In fishless mountain lakes with high intrasexual competition, guarding males can reduce the risk of spermatophore displacement or the risk that the female will accept sperm from rival males without increased risk of being eaten, thereby maximizing paternity. Populations from fishless alpine lakes further differed from lowland species by exhibiting higher female/male size dimorphism and more intense pigmentation. While these traits vary between populations according to predation pressure, mating duration appears to be more species-specific.