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1. A changing menu in a changing climate: Using experimental and long‐term data to predict invertebrate prey biomass and availability in lakes of arctic Alaska

   https://doi.org/10.1111/fwb.13162  

   Klobucar, Stephen L. ; Gaeta, Jereme W. ; Budy, Phaedra ( August 2018 , Freshwater Biology)

   Changes in seasonality associated with climate warming (e.g. temperature, growing season duration) are likely to alter invertebrate prey biomass and availability in aquatic ecosystems through direct and indirect influences on physiology and phenology, particularly in arctic lakes. However, despite warmer thermal regimes, photoperiod will remain unchanged such that potential shifts resulting from longer and warmer growing seasons could be limited by availability of sunlight, especially at lower trophic levels. Thus, a better understanding of warming effects on invertebrate prey throughout the growing season (e.g. early, peak, late) is important to understand arctic lake food‐web dynamics in a changing climate.

   Here, we use a multifaceted approach to evaluate prey availability to predators in lakes of arctic Alaska. In a laboratory mesocosm experiment, we measured different metrics of abundance for snails (Lymnaea elodes) and zooplankton (Daphnia middendorffiana) across three time periods (early, mid‐ and late growing season) and across three temperature and photoperiod treatments (control, increased temperature and increased temperature × photoperiod). Additionally, we used generalised additive models and generalised additive mixed‐effects models to relate long‐term empirical observations of zooplankton biomass (1983–2015) to observed temperature regimes in an arctic lake. We then simulated zooplankton biomass for the warmest temperature observations across the growing season to inform likely zooplankton biomass regimes under future change.

   We observed variable responses by snails and zooplankton across experiments and treatments. Early in the growing season, snail development was accelerated at multiple life stages (e.g. egg and juvenile). In mid‐season, in accordance with warmer temperatures, we observed significantly increasedDaphniaabundances. However, in the late season,Daphniaappeared to be limited by photoperiod. Confirming our experimental results, our models of zooplankton biomass showed an increase of nearly 20% in warmer years. Further, these model estimates could be conservative as the consumptive demand of fishes may increase in warmer years as well.

   Overall, our results highlight the importance of interactive effects of temperature and seasonality. Based primarily on temperature, we can readily predict the response of fish metabolism in warmer temperatures. However, in this context, we generally require a better understanding of climate‐driven responses of important invertebrate prey resources. Our results suggest invertebrate prey biomass and availability are likely to respond positively with climate change based on temperature and seasonality, as well as proportionally to the metabolic requirements of fish predators. While further research is necessary to understand how other food‐web components will respond climate change, our findings suggest that the fish community at the top of arctic lake food webs will have adequate prey base in a warming climate.

    

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2. Climate Change Implications for Tidal Marshes and Food Web Linkages to Estuarine and Coastal Nekton

   https://doi.org/10.1007/s12237-020-00891-1  

   Colombano, Denise D. ; Litvin, Steven Y. ; Ziegler, Shelby L. ; Alford, Scott B. ; Baker, Ronald ; Barbeau, Myriam A. ; Cebrián, Just ; Connolly, Rod M. ; Currin, Carolyn A. ; Deegan, Linda A. ; et al ( January 2021 , Estuaries and Coasts)

   null (Ed.)

   Abstract Climate change is altering naturally fluctuating environmental conditions in coastal and estuarine ecosystems across the globe. Departures from long-term averages and ranges of environmental variables are increasingly being observed as directional changes [e.g., rising sea levels, sea surface temperatures (SST)] and less predictable periodic cycles (e.g., Atlantic or Pacific decadal oscillations) and extremes (e.g., coastal flooding, marine heatwaves). Quantifying the short- and long-term impacts of climate change on tidal marsh seascape structure and function for nekton is a critical step toward fisheries conservation and management. The multiple stressor framework provides a promising approach for advancing integrative, cross-disciplinary research on tidal marshes and food web dynamics. It can be used to quantify climate change effects on and interactions between coastal oceans (e.g., SST, ocean currents, waves) and watersheds (e.g., precipitation, river flows), tidal marsh geomorphology (e.g., vegetation structure, elevation capital, sedimentation), and estuarine and coastal nekton (e.g., species distributions, life history adaptations, predator-prey dynamics). However, disentangling the cumulative impacts of multiple interacting stressors on tidal marshes, whether the effects are additive, synergistic, or antagonistic, and the time scales at which they occur, poses a significant research challenge. This perspective highlights the key physical and ecological processes affecting tidal marshes, with an emphasis on the trophic linkages between marsh production and estuarine and coastal nekton, recommended for consideration in future climate change studies. Such studies are urgently needed to understand climate change effects on tidal marshes now and into the future. 

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3. Hurricane disturbance drives trophic changes in neotropical mountain stream food webs

   https://doi.org/10.1002/ecy.4202  

   Gutiérrez‐Fonseca, Pablo E. ; Pringle, Catherine M. ; Ramírez, Alonso ; Gómez, Jesús E. ; García, Pavel ( November 2023 , Ecology)

   Food webs are complex ecological networks that reveal species interactions and energy flow in ecosystems. Prevailing ecological knowledge on forested streams suggests that their food webs are based on allochthonous carbon, driven by a constant supply of organic matter from adjacent vegetation and limited primary production due to low light conditions. Extreme climatic disturbances can disrupt these natural ecosystem dynamics by altering resource availability, which leads to changes in food web structure and functioning. Here, we quantify the response of stream food webs to two major hurricanes (Irma and María, Category 5 and 4, respectively) that struck Puerto Rico in September 2017. Within two tropical forested streams (first and second order), we collected ecosystem and food web data 6 months prior to the hurricanes and 2, 9, and 18 months afterward. We assessed the structural (e.g., canopy) and hydrological (e.g., discharge) characteristics of the ecosystem and monitored changes in basal resources (i.e., algae, biofilm, and leaf litter), consumers (e.g., aquatic invertebrates, riparian consumers), and applied Layman's community‐wide metrics using the isotopic composition of¹³C and¹⁵N. Continuous stream discharge measurements indicated that the hurricanes did not cause an extreme hydrological event. However, the sixfold increase in canopy openness and associated changes in litter input appeared to trigger an increase in primary production. These food webs were primarily based on terrestrially derived carbon before the hurricanes, but most taxa (includingAtyaandXiphocarisshrimp, the consumers with highest biomass) shifted their food source to autochthonous carbon within 2 months of the hurricanes. We also found evidence that the hurricanes dramatically altered the structure of the food web, resulting in shorter (i.e., smaller food‐chain length), narrower (i.e., lower diversity of carbon sources) food webs, as well as increased trophic species packing. This study demonstrates how hurricane disturbance can alter stream food webs, changing the trophic base from allochthonous to autochthonous resources via changes in the physical environment (i.e., canopy defoliation). As hurricanes become more frequent and severe due to climate change, our findings greatly contribute to our understanding of the mechanisms that maintain forested stream trophic interactions amidst global change.

    

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4. 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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5. Biogeography of ocean acidification: Differential field performance of transplanted mussels to upwelling-driven variation in carbonate chemistry.

   https://doi.org/10.1371/journal.pone.0234075  

   Rose, Jeremy M. ; Blanchette, Carol A. ; Chan, Francis ; Gouhier, Tarik C. ; Raimondi, Peter T. ; Sanford, Eric ; Menge, Bruce A. ( July 2020 , PloS one)

   Griffen, Blaine D. (Ed.)

   Ocean acidification (OA) represents a serious challenge to marine ecosystems. Laboratory studies addressing OA indicate broadly negative effects for marine organisms, particularly those relying on calcification processes. Growing evidence also suggests OA combined with other environmental stressors may be even more deleterious. Scaling these laboratory studies to ecological performance in the field, where environmental heterogeneity may mediate responses, is a critical next step toward understanding OA impacts on natural communities. We leveraged an upwelling-driven pH mosaic along the California Current System to deconstruct the relative influences of pH, ocean temperature, and food availability on seasonal growth, condition and shell thickness of the ecologically dominant intertidal mussel Mytilus californianus. In 2011 and 2012, ecological performance of adult mussels from local and commonly sourced populations was measured at 8 rocky intertidal sites between central Oregon and southern California. Sites coincided with a large-scale network of intertidal pH sensors, allowing comparisons among pH and other environmental stressors. Adult California mussel growth and size varied latitudinally among sites and inter-annually, and mean shell thickness index and shell weight growth were reduced with low pH. Surprisingly, shell length growth and the ratio of tissue to shell weight were enhanced, not diminished as expected, by low pH. In contrast, and as expected, shell weight growth and shell thickness were both diminished by low pH, consistent with the idea that OA exposure can compromise shell-dependent defenses against predators or wave forces. We also found that adult mussel shell weight growth and relative tissue mass were negatively associated with increased pH variability. Including local pH conditions with previously documented influences of ocean temperature, food availability, aerial exposure, and origin site enhanced the explanatory power of models describing observed performance differences. Responses of local mussel populations differed from those of a common source population suggesting mussel performance partially depended on genetic or persistent phenotypic differences. In light of prior research showing deleterious effects of low pH on larval mussels, our results suggest a life history transition leading to greater resilience in at least some performance metrics to ocean acidification by adult California mussels. Our data also demonstrate “hot” (more extreme) and “cold” (less extreme) spots in both mussel responses and environmental conditions, a pattern that may enable mitigation approaches in response to future changes in climate. 

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