Guest essay by Eric Worrall
Anyone who thinks stopping the swimming pool going green in Summer is a battle is mistaken. According to a recent study, warming reduces the growth rate of plankton, and starves animals up the food chain of food.
Global warming poses threat to food chains
MARCH 2, 2021 4:14 AM AEDT
Scientists measured the transfer of energy from single-celled algae (phytoplankton) to small animals that eat them (zooplankton).
The study – by Queen Mary University of London and the University of Exeter, and published in the journal Nature – found that 4°C of warming reduced energy transfer in the plankton food webs by up to 56 per cent.
“These findings shine a light on an under-appreciated consequence of global warming,” said Professor Gabriel Yvon-Durocher, of the Environment and Sustainability Institute on Exeter’s Penryn Campus in Cornwall.
“Phytoplankton and zooplankton are the foundation of food webs that support freshwater and marine ecosystems that humans depend on. Our study is the first direct evidence that the cost of growth increases in higher temperatures, limiting the transfer of energy up a food chain.”
The abstract of the study;
Warming impairs trophic transfer efficiency in a long-term field experiment
In natural ecosystems, the efficiency of energy transfer from resources to consumers determines the biomass structure of food webs. As a general rule, about 10% of the energy produced in one trophic level makes it up to the next1–3. Recent theory suggests this energy transfer could be further constrained if rising temperatures increase metabolic growth costs4, although experimental confirmation in whole ecosystems is lacking. We quantified nitrogen transfer efficiency (a proxy for overall energy transfer) in freshwater plankton in artificial ponds exposed to 7 years of experimental warming. We provide the first direct experimental evidence that, relative to ambient conditions, 4 °C of warming can decrease trophic transfer efficiency by up to 56%. In addition, both phytoplankton and zooplankton biomass were lower in the warmed ponds, indicating major shifts in energy uptake, transformation and transfer5,6. These new findings reconcile observed warming-driven changes in individual-level growth costs and carbon-use efficiency across diverse taxa4,7–10with increases in the ratio of total respiration to gross primary production at the ecosystem level11–13. Our results imply that an increasing proportion of the carbon fixed by photosynthesis will be lost to the atmosphere as the planet warms, impairing energy flux through food chains, with negative implications for larger consumers and the functioning of entire ecosystems.
I’d love to know what their secret is. Because the one thing about living in the tropics is the the annual battle in Summer to stop the swimming pool going bright green. And my tropical swimming pool is a great deal warmer than any pool of gently warmed water in Britain.
via Watts Up With That?
March 1, 2021 at 08:44PM