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

Area of Science:

• Aquatic ecology
• Ecosystem science
• Climate change impacts

Background:

• Global aquatic ecosystems face unprecedented warming and ecological shifts.
• Temperature influences metabolic rates, population dynamics, and ecosystem processes like carbon and oxygen fluxes.
• Warming's effects on community structure and function can be complex and sometimes contradictory.

Purpose of the Study:

• To experimentally test how predator presence and species interactions modify temperature-dependent ecosystem oxygen production and respiration.
• To investigate the role of trophic cascades in mediating the effects of warming on aquatic communities.
• To understand the relationship between temperature, trophic interactions, and ecosystem functions.

Main Methods:

• Experimental manipulation of freshwater ecosystems (370 L) over 9 weeks.
• Tracking changes in phytoplankton biomass, zooplankton prey, and predator-prey interactions across a temperature gradient (19-30 °C).
• Measuring net ecosystem oxygen production and respiration to assess ecosystem function.

Main Results:

• Higher temperatures amplified predator cascading effects on zooplankton and algae.
• Phytoplankton biomass declined significantly, especially when grazers were present without predators.
• Ecosystem oxygen production and consumption increased exponentially with temperature, showing relative insensitivity to trophic interactions.

Conclusions:

• Temperature-dependent trophic cascades alter community structure but do not necessarily lead to species loss or ecosystem collapse.
• Despite shifts in community biomass, net ecosystem oxygen fluxes remain predictable with warming.
• Local community dynamics, including trophic cascades, are compatible with predictable, metabolism-driven ecosystem functions under warming.