Suchergebnisse

In streams, unionoid mussels and fish form aggregations that exert bottom-up and top-down effects on food webs, but the magnitude and spatial extent of their effects are controlled by species traits. Sedentary mussels live burrowed in the sediment in patchily distributed dense aggregations (mussel beds) where they filter seston and provide a local, relatively constant nutrient subsidy. In contrast, fish move on and off mussel beds, and thus comprise a transient nutrient subsidy. We asked how overlap between fish and mussels influences nutrient recycling and resource distribution in streams. We conducted an 8-week study in experimental streams where we created mussel beds (comprised of two species, Actinonaias ligamentina and Amblema plicata), manipulated the occurrence of a grazing minnow (Campostoma anomalum), and tracked nutrient (nitrogen and phosphorus) and resource (algae, detritus, and chironomids) abundance up and downstream of the mussel beds. In general, neither consumer had strong effects on the concentration or spatial distribution of nutrients. Water turnover time in our experimental streams may have diluted fish and mussel nutrient excretion effects, making it difficult to detect spatial patterns during a given sampling period. Fish controlled the abundance and productivity of algae. In treatments without fish, large mats of filamentous algae formed early in the experiment. These algae senesced, decomposed, and were not replaced. When fish were present, algae consisted of attached biofilms with consistent biomass and spatial distribution over time. Although previous work has shown that mussels can have strong, seasonal bottom-up effects on both primary and secondary production, our results suggested that adding grazing mobile fishes, led to a more consistent and homogenous supply of algal resources. Because mussels rarely occur in the absence of fish, considering their combined influence on ecosystem dynamics is likely to be important. ; National Science FoundationNational Science Foundation (NSF) ; Published version ; National Science Foundation ; Public domain authored by a U.S. government employee

Freshwater mussels are declining globally, and effective conservation requires prioritizing research and actions to identify and mitigate threats impacting mussel species. Conservation priorities vary widely, ranging from preventing imminent extinction to maintaining abundant populations. Here, we develop a portfolio of priority research topics for freshwater mussel conservation assessment. To address these topics, we group research priorities into two categories: intrinsic or extrinsic factors. Intrinsic factors are indicators of organismal or population status, while extrinsic factors encompass environmental variables and threats. An understanding of intrinsic factors is useful in monitoring, and of extrinsic factors are important to understand ongoing and potential impacts on conservation status. This dual approach can guide conservation status assessments prior to the establishment of priority species and implementation of conservation management actions. ; NF-R was supported by a post-doctoral fellowship (Xunta de Galicia Plan I2C 2017-2020, 09.40.561B.444.0) from the government of the autonomous community of Galicia. BY was supported by the Ministry of Science and Higher Education (no. 0409-2016-0022). DLS was supported by the G. E. Hutchinson Chair at the Cary Institute of Ecosystem Studies. AO was supported by the Russian Foundation for Basic Research (no. 17-44-290016). SV was funded by European Investment Funds by FEDER/COMPETE/POCI- Operacional Competitiveness and Internacionalization Programme, under Project POCI-01-0145-FEDER-006958 and National Funds by FCT-Portuguese Foundation for Science and Technology, under the project UID/AGR/04033/2013. NF-R is very grateful to the University of Oklahoma Biological Survey for providing space to work in the U.S. and especially to Vaughn Lab members. Authors are very grateful to Akimasa Hattori, Allan K. Smith, Andrew Roberts, Daniel Graf, David Stagliano, David T. Zanatta, Dirk Van Damme, Ekaterina Konopleva, Emilie Blevins, Ethan Nedeau, Frankie Thielen, ...