Ocean warming and species range shifts affect rates of ecosystem functioning by altering consumer–resource interactions

Abstract

Recent warming trends have driven widespread changes in the performance and distribution of species in many regions, with consequent shifts in assemblage structure and ecosystem functioning. However, as responses to warming vary across species and regions, novel communities are emerging, particularly where warm-affinity range-expanding species have rapidly colonised communities still dominated by cold-affinity species. Such community reconfiguration may alter core ecosystem processes, such as productivity or nutrient cycling, yet it remains unclear whether novel communities function similarly to those they have replaced, and how continued warming will alter functioning in the near future. Using simplified kelp forest communities as a model system, we compared rates of respiration, consumption and secondary productivity between current cold-affinity and future warm-affinity kelp assemblages under both present-day temperatures and near future warming in a series of mesocosm experiments. Overall, respiration rates of gastropods and amphipods increased with warming but did not differ between cold and warm affinity kelp assemblages. Consumption rates of three consumers (urchin, gastropod and amphipod) differed between kelp assemblages but only amphipod consumption rates increased with warming. A diet derived from warm-affinity kelp assemblages led to a decrease in growth and biomass of urchins, whereas the response of other consumers was variable depending on temperature treatment. These results suggest that climate-driven changes in assemblage structure of primary producers will alter per capita rates of ecosystem functioning, and that specific responses may vary in complex and unpredictable ways, with some mediated by warming more than others. Understanding how differences in life history and functional traits of dominant species will affect ecological interactions and, in turn, important ecosystem processes is crucial to understanding the wider implications of climate-driven community reconfiguration.

Pulsed pressure: Fluctuating impacts of multifactorial environmental change on a temperate macroalgal community

“…This shrinking of the grazer population is likely to have (over-) compensated any hypothetical increase of per capita grazing which in addition was limited to the amphipods. The shrinking of mesograzer biomass with warming has been suggested to reflect a mismatch between the warming-driven increase of metabolic rates (Brown et al 2004) and a finite digestive tract limiting any compensatory feeding (Gilson et al 2021). The observed detrimental impact on juvenile grazers may hint at a potential carryover effect, since a decrease in the abundance of juveniles under heat stress will translate to a decrease in the abundance of adults even when the stress ceases.…”

“…(17°C) (Wahl et al 2020), all warming levels should have decreased the grazing activities of these two mesograzer groups. Only amphipod activity ( T opt = 21°C) could have been enhanced by moderate warming (Gilson et al 2021). However, it is likely that such warming‐induced increase in grazer activity was partially or completely suppressed by the hypoxia stress experienced during upwelling 3 as seen in the incubation experiments.…”

Major Expansion of Marine Forests in a Warmer Arctic

“…The poleward expansion of macrophytes (i.e., borealization of temperate communities) has important consequences for the functioning of Arctic ecosystems given their roles in e.g., carbon and nutrient cycling and storage (Filbee-Dexter et al, 2019;Vilas et al, 2020;Gilson et al, 2021). Because of their much higher C/N and C/P ratios compared to phytoplankton (Duarte, 1992), macrophytes can export far more carbon per unit of available nutrients than phytoplankton, thereby having the capacity to enhance the biological carbon pump.…”

Temperate Kelp Forest Collapse by Fish Herbivory: A Detailed Demographic Study

“…Climate change is behind the redistribution of many species on a global scale, and consequently shifts community structure and ecosystem functioning (Pecl et al, 2017;Gilson et al, 2021). In marine environments, poleward range shifts have been documented for several species in response to rising seawater temperatures (Lima et al, 2007;Sorte et al, 2010;Poloczanska et al, 2013).…”