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Abstract Terrestrial organic matter (tOM) plays a critical role in aquatic ecosystems, influencing carbon processes and greenhouse gas emissions. Here, we investigate the impact of tOM on methane production in littoral and pelagic sediments from the Mississippi River headwaters using a microcosm approach. Contrary to our expectations, tOM addition universally increased methane production across lentic sediments, with no significant difference between littoral and pelagic zones. Methane production was influenced by select sediment microorganisms, primarily methanogens and lignocellulose degrading bacteria, which responded similarly across different sediment habitats. The study highlights the role of cytochrome-containing methanogens and their syntrophic relationships with fermentative bacteria, emphasizing the significance of microbial community structure in sediment methane dynamics. Our findings suggest that increasing tOM loads to freshwater systems could have broader implications for methane emissions, driven by specific microbial interactions. Author Contribution StatementHMS and TLH conceived the study and obtained the funds. HMS led fieldwork and microcosm set-up. HMS and LAD analyzed gas samples and HMS performed the data analysis and graphical representation of the results. HMS wrote the first draft of the manuscript, and all authors contributed significantly to the preparation of the final draft. Scientific Significance StatementAs human activities and climate change increase the amount of organic material entering lakes and rivers, understanding the effects this has on greenhouse gas emissions is crucial. Our study reveals that adding terrestrial organic matter to freshwater sediments universally boosts methane production, a potent greenhouse gas. Through the exploration of microbial communities responsible for this process, our research highlights how changes in terrestrial organic matter export to aquatic systems could increase methane emissions from sediments. Data Availability StatementAdditional Supporting Information can be found in the online version of this article, including an extended version of methods and supplementary tables. Sequencing data associated with this paper is available on NCBI, BioProject PRJNA1164797. 

Vertebrate life histories evolve in response to selection imposed by abiotic and biotic environmental conditions while being limited by genetic, developmental, physiological, demographic and phylogenetic processes that constrain adaptation. Despite the well-recognized shifts in selective pressures accompanying transitions among environments, the conditions driving innovation and the consequences for life-history evolution remain outstanding questions. Here we compare the traits of vertebrates that occupy aquatic or terrestrial environments as juveniles to infer shifts in evolutionary constraints that explain differences in their life-history traits and thus their fundamental demographic rates. Our results emphasize the reduced potential for life-history diversification on land, especially that of reproductive strategies, which limits the scope of viable life-history strategies. Moreover, our study reveals differences between the evolution of viviparity in aquatic and terrestrial realms. Transitions from egg laying to live birth represent a major shift across life-history space for aquatic organisms, whereas terrestrial egg-laying organisms evolve live birth without drastic changes in life-history strategy. Whilst trade-offs in the allocation of resources place fundamental constraints on the way life histories can vary, ecological setting influences the position of species within the viable phenotypic space available for adaptive evolution. 

Ligand-exchange reactions of wurtzite CdSe quantum platelets (QPs) and quantum belts (QBs) with methyl viologen (MV2+) and the derivative ligands MV2+(CH2)nNH2 (n = 2, 4, or 6) are investigated. The QP and QB photoluminescence is quenched after partial ligand exchange. Spectroscopic and compositional data establish that this initial ligand substitution occurs on the thin QP and QB edges. The MV2+(CH2)nNH2 ligands are shown to be more-efficient photoluminescence quenchers than the parent MV2+ ion. The ligands on the thin, nonpolar, long-edge facets quench the photoluminescence via the trapping of excitons. Transient absorption experiments indicate the excitons dissociate, and electron transfer to the MV2+(CH2)nNH2 ligands only occurs at the polar, short-edge facets of the wurtzite CdSe QPs and QBs. Electron transfer to the MV2+(CH2)nNH2 ligands occurs within 100 fs when exciting at the band edge and on longer time scales, due to intraband relaxation, when exciting at higher energies. 

Wurtzite CdSe quantum belts with L-type n-octylamine, L-type ammonia, or Z-type Cd(oleate)2 ligands are exchanged for several metal-dithiocarbamate ligands [M(S2CNR1R2)2]: Cd(S2CNPhMe)2, Cd(S2CNEt2)2, Zn(S2CNPhMe)2, and Zn(S2CNEt2)2. Successful ligand exchange with all M(S2CNR1R2)2 compounds occurs from {CdSe[Cd(oleate)2]0.19} quantum belts (QBs), which induce similar spectral shifts in the absorption spectra of the ligand-exchanged QBs. Spectroscopic data, experimentally determined lattice strains, and ligand exchanges with [Na][Et2NCS2] and [NH4][MePhNCS2] establish that the [M(S2CNR1R2)2] ligands bind as bound-ion-paired X-type ligands with (S2CNR1R2)− groups ligated directly to the QB surfaces and [M(S2CNR1R2)]+ groups serving as the charge-balancing ion-paired countercations. The X-type dithiocarbamate ligands do not impart any special electronic effects to the CdSe QBs. 

The microbial communities of lake sediments have the potential to serve as valuable bioindicators and integrators of watershed land-use and water quality; however, the relative sensitivity of these communities to physio-chemical and geographical parameters must be demonstrated at taxonomic resolutions that are feasible by current sequencing and bioinformatic approaches. The geologically diverse and lake-rich state of Minnesota (USA) is uniquely situated to address this potential because of its variability in ecological region, lake type, and watershed land-use. In this study, we selected twenty lakes with varying physio-chemical properties across four ecological regions of Minnesota. Our objectives were to (i) evaluate the diversity and composition of the bacterial community at the sediment-water interface and (ii) determine how lake location and watershed land-use impact aqueous chemistry and influence bacterial community structure. Our 16S rRNA amplicon data from lake sediment cores, at two depth intervals, data indicate that sediment communities are more likely to cluster by ecological region rather than any individual lake properties ( e . g ., trophic status, total phosphorous concentration, lake depth). However, composition is tied to a given lake, wherein samples from the same core were more alike than samples collected at similar depths across lakes. Our results illustrate the diversity within lake sediment microbial communities and provide insight into relationships between taxonomy, physicochemical, and geographic properties of north temperate lakes. 

What if the environment could be transformed in culturally-responsive and inclusive ways to foster high-quality interactions and spark conversations that drive learning? In this article, we describe a new initiative accomplishing this, called Playful Learning Landscapes (PLL). PLL is an evidence-based initiative that blends findings from the science of learning with community-based participatory research to transform physical public spaces and educational settings into playful learning hubs. Here, we describe our model for conducting this research, which is mindful of three key components: community input, how children learn best, and what children need to learn to be successful in the 21st century economy. We describe how this model was implemented in two PLL case studies: one in a predominantly Latine community and the second in early childhood education classrooms. Furthermore, we describe how research employing our model can be rigorously and reliably evaluated using observational and methodological tools that respond to diverse cultural settings and learning outcomes. For example, our work evaluates how PLL impacts adult–child interaction quality and language use, attitudes about play and learning, and community civic engagement. Taken together, this article highlights new ways to involve community voices in developmental and educational research and provides a model of how science can be translated into practice and evaluated in culturally responsive ways. This synthesis of our process and evaluation can be used by researchers, policymakers, and educators to reimagine early educational experiences with an eye toward the built environment that children inhabit in everyday life, creating opportunities that foster lifelong learning. 

Changes in climate are altering disturbance regimes in forests of western North America, leading to increases in the potential for disturbance events to overlap in time and space. Though interactions between abiotic and biotic disturbance (e.g., the effect of bark beetle outbreak on subsequent wildfire) have been widely studied, interactions between multiple biotic disturbances are poorly understood. Defoliating insects, such as the western spruce budworm (WSB; Choristoneura freemanni), have been widely suggested to predispose trees to secondary colonization by bark beetles, such as the Douglas-fir beetle (DFB; Dendroctonus pseudotsugae). However, there is little quantitative research that supports this observation. Here, we asked: Does previous WSB damage increase the likelihood of subsequent DFB outbreak in Douglas-fir (Pseudotsuga menziesii) forests of the Southern Rocky Mountains, USA? To quantify areas affected by WSB and then DFB, we analyzed Aerial Detection Survey data from 1999–2019. We found that a DFB presence followed WSB defoliation more often than expected under a null model (i.e., random distribution). With climate change expected to intensify some biotic disturbances, an understanding of the interactions between insect outbreaks is important for forest management planning, as well as for improving our understanding of forest change.