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The period of student teaching often creates crisis experiences in student teachers and can have various negative effects, but it also offers opportunities for deep learning. This study focused on the types of struggles student teachers encounter and on the effects of coaching aimed at the promotion of core reflection. Core reflection is an approach focusing on the tension between people's inner strengths and their inner obstacles, as a way to support growth. While previous research suggested that teachers were able to improve their classroom performance due in part to core reflection's influence, no study before this one has directly explored how core reflection addressed uncertainty experienced by student teachers. Additionally, this study indicates core reflection may aid student teachers with finding a personal, authentic way of teaching -- a process one may call a Hero's Journey.

This paper presents a study that investigated how mentors perceived their long-term relationships with teacher candidates in a secondary teacher preparation program. The study describes the process by which the teacher candidates and the mentors select each other and how the relationship develops, with findings that suggest that the length of time teacher candidates and mentor teachers work together as essential to building trust. Mentors identify themselves as quasi-teacher educators who serve as an extension to the university preparation process. Findings explore the benefits of mentoring for the prospective and practicing teachers as well as to teacher preparation in general. To optimize the value of field experience, it is important to understand this relationship and its outcomes.

Polar freshwater ecosystems are sensitive to climate change, facing increasing temperatures and its consequences such as glacier retreat. Phosphorus and/or fixed nitrogen are widely expected to limit primary production in most freshwater environments, however the role of micronutrients is largely un‐characterized. We measured dissolved nitrate and nitrite, phosphate, cobalt, iron, manganese and zinc in a selection of Greenland and Antarctic lakes, and report the first evaluation of cobalt regulating phytoplankton growth in these systems using bioassay incubations. Results showed cobalt potentially co‐limited phytoplankton in three of the eight sites tested. A time‐series of dissolved cobalt measured in Kobbefjord (southwest Greenland) runoff corroborated low cobalt availability during summer. This was in contrast to manganese and iron which remained at high concentrations throughout summer. We hypothesize that high manganese:cobalt and/or zinc:cobalt ratios in runoff, may impede cellular cobalt acquisition, meaning cobalt co‐limitation of primary production is plausible in many polar freshwater environments. Plain Language Summary: Primary production in aquatic environments relies on supplies of bio‐accessible nitrogen and phosphorus in addition to light availability. Glacier melt and permafrost degradation have accelerated worldwide over the past two decades, inducing changes in these resources with ensuing ecological impacts. The potential ecological role of bio‐essential metals such as cobalt has however been sparsely tested in polar aquatic environments. Here we conducted nutrient addition bioassay incubations in a selection of Greenland and Antarctic lakes, and found phytoplankton growth was potentially co‐limited by dissolved cobalt availability in three of the eight tested sites. Manganese, zinc and cobalt can compete for cellular uptake, therefore we further analyzed dissolved concentrations in runoff across a multi‐year time‐series, finding that the ratios of these elements are potentially conducive to inhibition of cobalt uptake. We hypothesize that cobalt may more broadly co‐limit aquatic primary production as a result of high manganese:cobalt and/or zinc:cobalt ratios, with potential impacts on microbial community composition. Key Points: Concentrations of macro‐ and micro‐nutrients in a selection of Greenland and Antarctic lakes indicated cobalt deficiency for phytoplanktonBioassay incubation results showed cobalt potentially co‐limited phytoplankton in three of the eight sites testedA time‐series of measurements in Greenland runoff suggested high manganese:cobalt and zinc:cobalt ratios could impede cellular cobalt acquisition [ABSTRACT FROM AUTHOR]

Trichodesmium spp. is a colonial diazotrophic cyanobacterium found in the oligotrophic (sub)tropical oceans, where its distribution is strongly regulated by the availability of phosphorus and iron. The bulk carbon : nitrogen : phosphorus elemental composition of phytoplankton has previously been shown to depart from classical "Redfield" values under nutrient‐limitation conditions. We hypothesized that the abundance of intracellular metabolites and the extended Redfield ratios of Trichodesmium, including a range of trace elements, are variable in response to conditions of phosphorus and iron limitation that are found in the ocean. To test this, we grew Trichodesmium under trace metal–controlled conditions, where phosphorus was supplied as either dissolved inorganic phosphorus (DIP) or dissolved organic phosphorus (DOP) from iron depleted to elevated levels. We found that the steady‐state extended Redfield ratios of Trichodesmium under the iron‐depleted condition was (C106N15.82P0.62)1000Fe2.26Zn2.37Mn1.68Cu0.68Ni0.31Mo0.42Co0.03 for the DIP treatment where Trichodesmium was under iron limitation, and (C106N13.89P0.49)1000Fe3.38Zn2.51Mn0.97Cu0.52Ni0.42Mo0.33Co0.03 for the DOP treatment where Trichodesmium was under iron–phosphorus co‐limitation. Mean steady‐state cellular iron : carbon in the DIP treatment (iron limited) was only 50% of that in the control treatment, while zinc : carbon was elevated twofold. The average extended Redfield ratios following recovery from iron limitation was (C106N16.8P0.7)1000Fe4.41Zn1.44Mn1Cu0.52Ni0.19Mo0.3Co0.03 for the DIP and (C106N15.9P0.73)1000Fe7.36Zn2.24Mn1.08Cu0.71Ni0.63Mo0.38Co0.02 for the DOP treatment. No significant changes were observed in the carbon‐normalized abundance of targeted metabolites produced by Trichodesmium, under the different treatments. These results suggest Trichodesmium employs different strategies to cope with iron/phosphorus limitation, which is reflected in its extended Redfield ratios. [ABSTRACT FROM AUTHOR]

Biological N2 fixation has been crucial for sustaining early life on Earth. Very negative δ15N values detected in Archean sediments, which are not observed in present‐day environments, have been attributed to the low efficiency of proto‐nitrogenases. Alternatively, variations in early atmospheric CO2 may also play a role. Here we examine the effects of CO2 concentrations on the biomass δ15N signatures of the diazotrophs Trichodesmium erythraeum and Crocosphaera watsonii, which utilize Mo‐Fe nitrogenase (the most common form of the enzyme). Our results show that these organisms produce biomass with δ15N values up to ∼3‰ lower under both decreased and elevated CO2 concentrations compared to modern levels (∼380 μatm). These deviations from modern CO2 levels reduce nitrogenase enzyme efficiency, leading to increased organismal isotopic fractionation during N2 fixation. This study offers an alternative explanation for the observed fluctuations in geological δ15N records and provides new insights into the past nitrogen cycle on Earth. Plain Language Summary: The isotope effect of biological N2 fixation is crucial for understanding the nitrogen cycle, but its regulation under different atmospheric CO2 levels as appeared in Earth's history is not well understood. Our research shows that CO2 levels significantly influence the nitrogen isotope composition in the biomass of the diazotrophic cyanobacteria Trichodesmium and Crocosphaera by affecting the nitrogenase efficiency and thus the growth rate. This study sheds light on the geological changes in the δ15N records and provides new insights into the historical nitrogen cycle on Earth. Key Points: The effects of CO2 on the biomass δ15N signatures of the diazotrophs Trichodesmium erythraeum and Crocosphaera watsonii are examinedBoth species produce biomass with δ15N values lower under both decreased and elevated CO2 concentrations compared to modern CO2 levelsCO2‐controlled nitrogenase efficiency significantly influences organismal isotopic fractionation during N2 fixation [ABSTRACT FROM AUTHOR]

Nutrient transfer into the sunlit surface ocean by cyclonic eddies is potentially crucial for sustaining primary productivity in the stratified subtropical gyres. However, the nature of productivity enhancements, including the flow of matter to higher trophic levels and its impact on carbon fluxes, remain poorly resolved. Here, we report a detailed assessment of the biogeochemical response to a cyclonic eddy in the subtropical Northwest Pacific via a combination of ship‐based and autonomous platforms. Primary production was enhanced twofold within the eddy core relative to reference sites outside, whereas phytoplankton biomass even decreased. Pico‐phytoplankton (< 2 μm) dominated (> 80%) both phytoplankton biomass and primary production inside and outside the eddy. The stimulated primary production in the eddy core was accompanied by an approximately twofold increase in mesozooplankton abundance, an approximately threefold increase in particle formation in the deep chlorophyll maximum layer, as well as significantly enhanced surface oceanic CO2 uptake and net community production. We suggest these observations carry important implications for understanding carbon export in the subtropical ocean and highlight the need to include such subtropical eddy features in ocean carbon budget analyses. [ABSTRACT FROM AUTHOR]

Biological nitrogen (N2) fixation is the main input of fixed nitrogen to ecosystems on Earth. Nitrogen isotope fractionation during this process is a key parameter for understanding the nitrogen cycle, however, relatively little is known about its regulatory mechanisms. Here we examine the effects of varying CO2 concentrations on biomass δ15N signatures of the cyanobacterial diazotrophs Trichodesmium erythraeum and Crocosphaera watsonii. We show that these organisms produce biomass up to ~3 ‰ lower in δ15N under either decreased (~180 µatm) or elevated (~1400 µatm) CO2 concentrations in comparison to modern levels (~380 µatm). Our results pointed towards changes in nitrogenase enzyme efficiency in response to CO2 perturbations impacting isotopic fractionation during N2 fixation and thus the biomass δ15N. This study contributes to an improved interpretation of the observed fluctuations in the δ15N records, and thus the past nitrogen cycle on Earth. [ABSTRACT FROM AUTHOR]