[OANNES Foro] Global meta‐analysis of how marine upwelling affects herbivory

Mario Cabrejos casal en infotex.com.pe
Vie Nov 22 07:19:32 PST 2019


Global Ecology and Biogeography

First published: 06 November 2019

 <https://doi.org/10.1111/geb.13023> https://doi.org/10.1111/geb.13023

Global meta‐analysis of how marine upwelling affects herbivory


<https://onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Sellers
%2C+Andrew+J> Andrew J. Sellers
<https://onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Leung%2
C+Brian> Brian Leung
<https://onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Torchin
%2C+Mark+E> Mark E. Torchin

Abstract

Aim

Nutrient subsidies support high primary productivity, increasing herbivore
abundance and influencing their top‐down control of producers. Wind‐driven
upwelling events deliver cold nutrient‐rich water to coastlines, supporting
highly productive marine environments. Results from studies comparing
ecological processes across upwelling regimes are mixed: some reveal weaker
herbivory in upwelling regions, while others report a positive relationship
between upwelling and herbivory. In this synthesis we examine the influence
of upwelling on top‐down control of producers across the globe.

Location

Global; marine ecosystems.

Time period

1978-2017.

Major taxa studied

Marine herbivores and algae.

Methods

We used data from herbivory studies focusing specifically on the influence
of upwelling activity (upwelling studies), and a broader collection of
herbivore exclusion studies dating back four decades. For the upwelling
studies we compared herbivore effects between experiments replicated across
sites for which upwelling conditions were described by the authors.
Meanwhile, for the broader collection of experiments we used externally
sourced oceanographic data to characterize upwelling activity, and examined
how herbivory changed along a gradient of upwelling activity.

Results

Our results consistently reveal that upwelling weakens herbivore effects on
producers. Herbivory was, on average, four times weaker in upwelling sites
relative to sites under weak upwelling or downwelling regimes in studies
that specifically examined upwelling. The analysis of the broader herbivory
literature revealed a similar weakening influence of upwelling on herbivory;
however, the effect size was smaller and varied across producer functional
groups.

Main conclusions

Nutrient subsidies from upwelling events reduce top‐down control by
herbivores in coastal ecosystems; however, the negative relationship between
upwelling intensity and herbivory is likely the result of a combination of
co‐occurring processes. First, increased primary production overwhelms
consumption by herbivores. Second, cold water reduces herbivore metabolism
and activity. Finally, surface currents associated with upwelling activity
transport herbivore larvae offshore, decoupling secondary production from
herbivory.



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