Idiosyncratic species effects confound size-based predictions of responses to climate change

Abstract

Understanding and predicting the consequences of warming for complex ecosystems and indeed individual species remains a major ecological challenge. Here, we investigated the effect of increased seawater temperatures on the metabolic and consumption rates of five distinct marine species. The experimental species reflected different trophic positions within a typical benthic East Atlantic food web, and included a herbivorous gastropod, a scavenging decapod, a predatory echinoderm, a decapod and a benthic-feeding fish. We examined the metabolism -body mass and consumption -body mass scaling for each species, and assessed changes in their consumption efficiencies. Our results indicate that body mass and temperature effects on metabolism were inconsistent across species and that some species were unable to meet metabolic demand at higher temperatures, thus highlighting the vulnerability of individual species to warming. While body size explains a large proportion of the variation in species' physiological responses to warming, it is clear that idiosyncratic species responses, irrespective of body size, complicate predictions of population and ecosystem level response to future scenarios of climate change.

Climate change in size-structured ecosystems

“…Warming directly accelerates individual metabolic rates [2 -5,15,92], which causes increased feeding rates [10,15]. Over the short term, this can lead to increased top-down control and trophic cascades.…”

“…Over the short term, this can lead to increased top-down control and trophic cascades. However, increases in feeding rates with warming are generally weaker than those of metabolism [15,28,29], which should lead to reduced consumer densities and long-term reductions in top-down control and trophic cascades. Interestingly, experimental results are mixed, with increases and decreases of trophic cascade strength in the planktonic and benthic food web, respectively [17].…”

“…These trophic cascades generally structure biomass distributions across populations in different ecosystem types [79]. Warming generally increases the individual consumption rates [10,15], which may explain the intensified trophic cascade in the planktonic food web of a pond mesocosm experiment [17]. However, the lack of a warming effect on the benthic trophic cascade in the same experiment illustrates that species interactions are often driven by more complex constraints than simple metabolic changes.…”

“…This theme issue integrates novel approaches for addressing the consequences of climate change in complex, sizestructured ecosystems. This includes the development of novel concepts [7][8][9][10], model analyses [11][12][13] and empirical studies in marine [14,15], freshwater [16,17] and terrestrial ecosystems [18][19][20][21][22]. In the following, we will introduce the framework of this theme issue by describing the complexity and the size structure of natural communities and how they might interact with climate change in determining top-down or bottom-up control, community stability and spatial processes.…”

Biodiversity and ecosystem functioning in dynamic landscapes

“…As the exact position of these intraguild predation motifs cannot be predicted a priori, this hinders simple predictions of how ecosystem functions vary between low-and high-diversity communities. This simultaneous change in biodiversity, network structure and associated ecosystem energy fluxes may explain the frequent occurrence of idiosyncratic BEF relationships in multi-trophic experiments [43,44].…”