Trophic interactions modify the temperature dependence of community biomass and ecosystem function

Abstract

Aquatic ecosystems worldwide continue to experience unprecedented warming and ecological change. Warming increases metabolic rates of animals, plants, and microbes, accelerating their use of energy and materials, their population growth, and interaction rates. At a much larger biological scale, warming accelerates ecosystem-level processes, elevating fluxes of carbon and oxygen between biota and the atmosphere. Although these general effects of temperature at finer and broader biological scales are widely observed, they can lead to contradictory predictions for how warming affects the structure and function of ecological communities at the intermediate scale of biological organization. We experimentally tested the hypothesis that the presence of predators and their associated species interactions modify the temperature dependence of net ecosystem oxygen production and respiration. We tracked a series of independent freshwater ecosystems (370 L) over 9 weeks, and we found that at higher temperatures, cascading effects of predators on zooplankton prey and algae were stronger than at lower temperatures. When grazing was weak or absent, standing phytoplankton biomass declined by 85%–95% (<1-fold) over the temperature gradient (19–30 °C), and by 3-fold when grazers were present and lacked predators. These temperature-dependent species interactions and consequent community biomass shifts occurred without signs of species loss or community collapse, and only modestly affected the temperature dependence of net ecosystem oxygen fluxes. The exponential increases in net ecosystem oxygen production and consumption were relatively insensitive to differences in trophic interactions among ecosystems. Furthermore, monotonic declines in phytoplankton standing stock suggested no threshold effects of warming across systems. We conclude that local changes in community structure, including temperature-dependent trophic cascades, may be compatible with prevailing and predictable effects of temperature on ecosystem functions related to fundamental effects of temperature on metabolism.

Conservation threats and future prospects for the freshwater fishes of Ecuador: A hotspot of Neotropical fish diversity

“…Fish in small mountain streams also have limited opportunities for habitat tracking and dispersal (Herrera‐R et al ., 2020 ; Taniwaki et al ., 2017 ). Recent studies from other areas suggest a range of potential impacts including changes in the distribution of species and trophic assemblages (Garzke et al ., 2019 ; Herrera‐R et al ., 2020 ), the age of sexual maturity (Shahjahan et al ., 2017 ), metabolic rates (Petitjean et al ., 2019 ), nutrient composition (Colombo et al ., 2019 ), contaminant absorption (Schartup et al ., 2019 ) and alterations in sex ratios (Fernandino & Hattori, 2019 ). Rarer cold water species at high elevations are likely to be impacted the most (Buisson et al ., 2008 ; Herrera‐R et al ., 2020 ), suggesting that high‐elevation Astroblepus spp.…”

Species diversity and food web structure jointly shape natural biological control in agricultural landscapes

“…Food webs describe species interactions within and between various trophic levels, and their composition dictates biodiversity-ecosystem functionality 30 , 31 . As a key food web metric, network generality (i.e., mean number of host or prey species per consumer) mediates ESs 32 , with high generality entailing the presence of multiple prey or host items for each consumer (i.e., predator or parasitoid) within the food web 33 , 34 and thereby mitigating impacts of eventual species loss 35 .…”

Temperature Fluctuation Attenuates the Effects of Warming in Estuarine Microbial Plankton Communities

“…Furthermore, previous experimental studies have reported that warming can promote changes toward smaller cells when nutrient stress intensifies (Peter and Sommer, 2013), increase carbon:nitrogen (C:N) ratios (Biermann et al, 2015), primary productivity and biodiversity (Yvon-Durocher et al, 2015), and reduce the efficiency of energy transfer from primary producers to herbivores and detritivores (Ullah et al, 2018). Also, warming can strengthen the predator-consumer interaction (Schaum et al, 2018b;Garzke et al, 2019), and ultimately weaken the C-sink capacity, as shown in experimental microbial plankton communities (Yvon-Durocher et al, 2017). Surprisingly, it is still poorly understood how the interaction between warming and temperature fluctuation affects the composition, dynamics and metabolism of microbial food webs.…”