Extreme rainfall events cause top-heavy aquatic food webs

Date:
July 9, 2020
Source:
University of British Columbia
Summary:
Scientists across seven different sites throughout Central and
South America replicated the extreme rainfall events predicted
by climate change science. Using the insect larvae that live in
the water trapped by bromeliad plants as a model ecosystem, they
found that food webs became top-heavy with predators when there
were large day-to-day variations in rainfall.



FULL STORY ==========================================================================
An expansive, multi-site ecology study led by UBC has uncovered new
insights into the effects of climate change on the delicate food webs
of the neotropics.


==========================================================================
In research recently outlined in Nature, scientists across seven different sites throughout Central and South America replicated the extreme rainfall events predicted by climate change science. Using the insect larvae that
live in the water trapped by bromeliad plants as a model ecosystem,
they found that food webs became top-heavy with predators when there
were large day-to-day variations in rainfall.

"This has knock-on effects for all parts of the rainforest system,
because the larval insects in the bromeliads are destined to become
winged adults that then are part of the forest ecosystem around them,"
said co-author Diane Srivastava, professor of zoology in UBC's faculty
of science, who established the Bromeliad Working Group, an international consortium of researchers who conducted the research.

To attain their results, scientists in sites spread across Argentina,
Brazil, Columbia, Costa Rica, French Guiana and Puerto Rico performed
identical experiments on bromeliads -- large flowering tropical plants
that trap water and provide a habitat for many aquatic insects and
larvae. The bromeliads were covered with rain shelters, and researchers
watered them on strict schedules to replicate 30 different rainfall
patterns in each site.

"This is the first study, to my knowledge, where we have a replicated
study of how precipitation patterns affect an entire food web in multiple sites," said Srivastava. "Every day we'd run around with a watering
can with a list of how much water each bromeliad should get on each
day. We had a customized rainfall schedule for each bromeliad in every
field site." While the researchers found that extreme rainfall patterns resulted in top- heavy food webs, the opposite was true when rainfall was delivered on an even schedule, with similar amounts of water delivered
to the plants every day.

Under those conditions, there were fewer predators and more prey among
the larval insects.

"We were actually expecting to see the opposite pattern," said
Srivastava. "We often think of predators being the most sensitive to environmental change, but we got the opposite result. One reason may be
that, when the water level in the bromeliad went down during drier days,
there was less aquatic habitat, so the prey was condensed into a small
amount of water together with their predators.

This can really benefit predators and disadvantage prey." These findings
can be extrapolated to other rainfall-dependent aquatic ecosystems, said Srivastava. "In any small pond or lake which is primarily determined by rainfall, we can expect to see a similar effect. We should be concerned
about these findings, because we've shown that these extreme perturbations
in rainfall really do affect the flow of energy through the food web."

========================================================================== Story Source: Materials provided by University_of_British_Columbia. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Gustavo Q. Romero, Nicholas A. C. Marino, A. Andrew M. MacDonald,
Régis Céréghino, M. Kurtis Trzcinski, Dimaris
Acosta Mercado, Céline Leroy, Bruno Corbara, Vinicius
F. Farjalla, Ignacio M. Barberis, Olivier Dézerald, Edd
Hammill, Trisha B. Atwood, Gustavo C. O. Piccoli, Fabiola Ospina
Bautista, Jean-François Carrias, Juliana S. Leal, Guillermo
Montero, Pablo A. P. Antiqueira, Rodrigo Freire, Emilio Realpe,
Sarah L. Amundrud, Paula M. de Omena, Alice B. A. Campos, Pavel
Kratina, Eoin J. O'Gorman, Diane S. Srivastava.

Extreme rainfall events alter the trophic structure in bromeliad
tanks across the Neotropics. Nature Communications, 2020; 11 (1)
DOI: 10.1038/ s41467-020-17036-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200709085310.htm

--- up 24 weeks, 2 days, 2 hours, 34 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)