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Forested headwater streams disproportionately rely on inputs of organic matter to fuel their food webs, and characterizing the breakdown of organic matter offers insights into ecosystem function. Organic matter breakdown rates can be influenced by the availability of limiting nutrients, and describing patterns of breakdown rates across nutrient gradients is increasingly relevant as inland waters undergo eutrophication. Here, we determined the breakdown rates of coarse woody debris (kwood) across 5 streams located at La Selva Biological Station, Costa Rica, that receive a gradient of interbasin modified groundwater inputs, creating a gradient in P concentration (6–134 lg/L soluble reactive P [SRP]). The fastest breakdown rate (kwood 50.77/y) occurred in the stream with the highest SRP, and kwood was positively correlated with SRP across the 5 streams. Further, we characterized the assemblage of macroinvertebrates from wood packs. Macroinvertebrate assemblages were different between the 5 streams, with more dense and diverse assemblages in streams with higher SRP and faster breakdown rates. Our results contribute to a growing field of study on the effect of nutrients on organic matter dynamics in inland waters by characterizing the effect of SRP on breakdown rates of wood in tropical streams. 

While many instructors have reservations against Wikipedia use in academic settings, editing Wikipedia teaches students valuable writing, editing, and critical thinking skills. Wikipedia assignments align with the community of inquiry framework, which focuses on the elements needed for a successful online learning experience. We report on a faculty mentoring network, created by WikiProject Limnology and Oceanography, which helped 14 instructors with little to no prior experience implement a Wikipedia assignment in their classes. We found that Wikipedia assignments increase students’ motivation to produce high quality work and enhance their awareness of reliable scientific sources. Wikipedia assignments can be comparable to other writing assignments in length and complexity, but have a far wider audience than a traditional research paper. Participants in our mentoring network reported challenges with implementing this new type of assignment, and here, we share resources and solutions to those reported barriers. 

Abstract Ecosystem metabolism of freshwater ecosystems has been studied for several decades, with theory and synthesis largely derived from temperate streams and rivers in North America and Europe. Advances in sensor technology and modeling have opened a wider range of streams to be included to test theories beyond temperate streams. In this paper, we review and synthesize ecosystem metabolism data from tropical streams and rivers to determine to what extent the constraints of metabolism measured in temperate streams are similar in tropical streams. We compiled 202 measurements of gross primary productivity (GPP) and ecosystem respiration (ER) from 83 tropical streams spanning 22.2°S to 18.4°N. Overall, tropical streams were heterotrophic (ER > GPP), with GPP ranging from 0.01 to 11.7 g O₂m⁻²d⁻¹and ER ranging from −0.2 to −42.1 g O₂m⁻²d⁻¹, similar on average to rates reviewed from temperate streams, but with higher maximum ER in tropical streams. Gross primary productivity increased with watershed area; a result also observed in temperate streams. ER decreased with elevated phosphorus and higher annual rainfall. We constructed a structural equation model that explained greater variation of ER (74%) than GPP (26%), and reflects similar drivers, such as land‐use and watershed area, as in temperate streams. We conclude that tropical stream ecosystem metabolism has similar drivers as temperate streams, and a warmer and wetter climate and human use of tropical lands will influence metabolic rates in streams.