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1. Reweaving river food webs through time

   https://doi.org/10.1111/fwb.13432  

   Bowes, Rachel E. ; Thorp, James H. ; Delong, Michael D. ( December 2019 , Freshwater Biology)

   Our project sought to determine ecological effects of adding low‐head dams and levees to large rivers by examining potential changes to aquatic food webs over a 70‐year period in the Lower Ohio River (LOR) and Upper Mississippi River (UMR).

   We employed museum collections of fish and compound specific stable isotope analysis of amino acids to evaluate long‐term changes in primary food sources for multiple species of fish in each river.

   Fishes in both rivers depended more on autochthonous than allochthonous carbon sources throughout the 70‐year period (based on measurements of isotopic signatures of algae, C₃plants, C₄plants, cyanobacteria, and fungi), but the relative use of different carbon sources differed between the UMR and LOR. Significant but opposite shifts in trophic positions (TP) between rivers over time (higher TP in the UMR; lower in the LOR) were correlated with major anthropogenic changes to habitat structure (e.g. slight decrease in abundance of side channels in the UMR; increase in pool water depth in the LOR) resulting from low‐head dam construction. They may also have been influenced by likely increased primary productivity in the UMR from agricultural nitrogen inputs and by possible shifts in the importance of phytoplankton versus benthic algae in the LOR from changes in water depth. Shifts in trophic position and reliance on various food sources were not correlated with variation in discharge, gage height, or temperature.

   Although these two rivers have contrasting hydrogeomorphic complexity (UMR is an anastomosing river, while the LOR is a constricted channel river) and different discharge patterns (seasonal versus yearly operation in some cases), both differ substantially from rivers having hydrogeomorphic changes resulting from construction of high dams (>15 m). It is not surprising, therefore, that factors controlling trophic position and reliance on different carbon sources vary among different types of dams and river structures.

    

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2. Ecogeographical rules and the macroecology of food webs

   https://doi.org/10.1111/geb.12925  

   Baiser, Benjamin ; Gravel, Dominique ; Cirtwill, Alyssa R. ; Dunne, Jennifer A. ; Fahimipour, Ashkaan K. ; Gilarranz, Luis J. ; Grochow, Joshua A. ; Li, Daijiang ; Martinez, Neo D. ; McGrew, Alicia ; et al ( May 2019 , Global Ecology and Biogeography)

   How do factors such as space, time, climate and other ecological drivers influence food web structure and dynamics? Collections of well‐studied food webs and replicate food webs from the same system that span biogeographical and ecological gradients now enable detailed, quantitative investigation of such questions and help integrate food web ecology and macroecology. Here, we integrate macroecology and food web ecology by focusing on how ecogeographical rules [the latitudinal diversity gradient (LDG), Bergmann's rule, the island rule and Rapoport's rule] are associated with the architecture of food webs.

   Global.

   Current.

   All taxa.

   We discuss the implications of each ecogeographical rule for food webs, present predictions for how food web structure will vary with each rule, assess empirical support where available, and discuss how food webs may influence ecogeographical rules. Finally, we recommend systems and approaches for further advancing this research agenda.

   We derived testable predictions for some ecogeographical rules (e.g. LDG, Rapoport's rule), while for others (e.g., Bergmann's and island rules) it is less clear how we would expect food webs to change over macroecological scales. Based on the LDG, we found weak support for both positive and negative relationships between food chain length and latitude and for increased generality and linkage density at higher latitudes. Based on Rapoport's rule, we found support for the prediction that species turnover in food webs is inversely related to latitude.

   The macroecology of food webs goes beyond traditional approaches to biodiversity at macroecological scales by focusing on trophic interactions among species. The collection of food web data for different types of ecosystems across biogeographical gradients is key to advance this research agenda. Further, considering food web interactions as a selection pressure that drives or disrupts ecogeographical rules has the potential to address both mechanisms of and deviations from these macroecological relationships. For these reasons, further integration of macroecology and food webs will help ecologists better understand the assembly, maintenance and change of ecosystems across space and time.

    

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3. Nutritional support of inland aquatic food webs by aged carbon and organic matter: Aged nutritional support of inland aquatic food webs

   https://doi.org/10.1002/lol2.10044  

   Bellamy, Amber R. ; Bauer, James E. ( October 2017 , Limnology and Oceanography Letters)
4. Scientists' warning on endangered food webs

   https://doi.org/10.5194/we-20-1-2020  

   Heleno, Ruben H. ; Ripple, William J. ; Traveset, Anna ( January 2020 , Web Ecology)

   Abstract. All organisms are ultimately dependent on a large diversity of consumptiveand non-consumptive interactions established with other organisms, formingan intricate web of interdependencies. In 1992, when 1700 concernedscientists issued the first “World Scientists' Warning to Humanity”, ourunderstanding of such interaction networks was still in its infancy. Bysimultaneously considering the species (nodes) and the links that glue themtogether into functional communities, the study of modern food webs – ormore generally ecological networks – has brought us closer to a predictivecommunity ecology. Scientists have now observed, manipulated, and modelledthe assembly and the collapse of food webs under various global changestressors and identified common patterns. Most stressors, such as increasingtemperature, biological invasions, biodiversity loss, habitat fragmentation,over-exploitation, have been shown to simplify food webs byconcentrating energy flow along fewer pathways, threatening long-termcommunity persistence. More worryingly, it has been shown that communitiescan abruptly change from highly diverse to simplified stable states withlittle or no warning. Altogether, evidence shows that apart from thechallenge of tackling climate change and hampering the extinction ofthreatened species, we need urgent action to tackle large-scale biologicalchange and specifically to protect food webs, as we are under the risk of pushingentire ecosystems outside their safe zones. At the same time, we need togain a better understanding of the global-scale synergies and trade-offsbetween climate change and biological change. Here we highlight the mostpressing challenges for the conservation of natural food webs and recentadvances that might help us addressing such challenges. 

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5. Controls of Methylmercury Bioaccumulation in Forest Floor Food Webs

   https://doi.org/10.1021/acs.est.8b06053  

   Tsz-Ki Tsui, Martin ; Liu, Songnian ; Brasso, Rebecka L. ; Blum, Joel D. ; Kwon, Sae Yun ; Ulus, Yener ; Nollet, Yabing H. ; Balogh, Steven J. ; Eggert, Sue L. ; Finlay, Jacques C. ( February 2019 , Environmental Science & Technology)