Search for: All records

Abstract Background and AimsFreshwater nitrogen inputs are increasing globally, altering the structure and function of wetland ecosystems adapted to low nutrient conditions. Carnivorous wetland plants of the genus Utricularia are hypothesized to reduce their reliance on carnivory and increase their assimilation of environmental nutrients when the supply of ambient nutrients increases. Despite success in using stable isotope approaches to quantify carnivory of terrestrial carnivorous plants, quantifying carnivory of aquatic Utricularia requires improvement. MethodsWe developed stable isotope mixing models to quantify aquatic plant carnivory and used these models to measure dietary changes of three Utricularia species, Utricularia australis, U. gibba and U. uliginosa, in 11 wetlands across a 794-km gradient in eastern Australia. Diet was assessed using multiple models that compared variations in the natural-abundance nitrogen isotope composition (δ15N) of Utricularia spp. with that of non-carnivorous plants, and environmental and carnivorous nitrogen sources. Key ResultsCarnivory supplied 40–100 % of plant nitrogen. The lowest carnivory rates coincided with the highest availability of ammonium and dissolved organic carbon. ConclusionsOur findings suggest that Utricularia populations may adapt to high nutrient environments by shifting away from energetically costly carnivory. This has implications for species conservation as anthropogenic impacts continue to affect global wetland ecosystems. 

Abstract Within aquatic ecosystems, heterotrophic, mixotrophic and autotrophic plankton are entangled in a complex network of competitive, predatory and mutualistic interactions. “Browning,” the increase of colored dissolved organic matter (CDOM) from terrestrial catchments, can affect this network of interactions by simultaneously decreasing light availability and increasing organic carbon and nutrients supplies. Here, we introduce a conceptual, process-based numerical model to investigate the effects of browning on a microbial food web consisting of heterotrophic bacterioplankton, bacterivorous phago-mixoplankton, autotrophic phytoplankton and the resources light, inorganic phosphorus and DOM. Additionally, we explore how the investment in autotrophic vs. phagotrophic resource acquisition influences mixoplankton performance. Several model predictions are in broad agreement with empirical observations under increasing CDOM supply, including increased bacterial biomass and inorganic phosphorous, decreased light penetration, the potential for a unimodal phytoplankton biomass response and a local minimum in mixoplankton biomass. Our results also suggest that mixoplankton with a high investment in phototrophy perform best in many conditions but that phosphorous acquisition via prey is crucial under high light-low nutrient conditions. Overall, our model analyses suggest that responses to altered CDOM supply are largely determined by systematic changes in the relative importance of nutrient vs. energy limitation of each plankton group. 

Abstract International research is necessary in aquatic sciences because water moves across borders. Historically, international collaborations have been useful in conducting oceanographic research programs, which span large distances and require several funding sources. Although valuable, international research can have unforeseen challenges to the unprepared researcher. Communication with an international collaborator and professional development training can mitigate these pitfalls. The Limnology and Oceanography Research Exchange Program (LOREX) is an opportunity for graduate students to gain experience developing international collaborations. The LOREX program aims to help graduate students develop connections and gain experience in international research. During the summer of 2019 and spring of 2020, 26 graduate students from 24 U.S. institutions will travel to one of six different host institutions to conduct a research project that they developed with an international collaborator. To prepare for their research experience, LOREX participants participated in training programs during the 2019 Aquatic Sciences Meeting in San Juan, Puerto Rico. The first group of LOREX graduate students will share their experience through social media and blog posts throughout their journey. Applications are now open for the second cohort of LOREX participants, and potential applicants are encouraged to contact potential collaborators to develop a research project.