[Vision2020] April 11, 2012: "Ocean acidification-induced food quality deterioration constrains trophic transfer"

[Ted Moffett]

It's easy to forget how the web of life on our planet, in the oceans as on
land, is fundamentally based on very small organisms, as the following peer
reviewed science article in part illuminates:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737

Ocean Acidification-Induced Food Quality Deterioration Constrains Trophic
Transfer

Dennis Rossoll1<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#aff1>
#<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#equal-contrib>,
Rafael Bermúdez1<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#aff1>
#<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#equal-contrib>,
Helena Hauss1<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#aff1>,
Kai G. Schulz1<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#aff1>,
Ulf Riebesell1<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#aff1>,
Ulrich Sommer1<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#aff1>,
Monika Winder1<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#aff1>
,2<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#aff2>
*<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#cor1>

*1* Helmholtz Centre for Ocean Research Kiel (GEOMAR), Kiel, Germany,
*2*Department of Systems Ecology, Stockholm University, Stockholm,
Sweden
Abstract

Our present understanding of ocean acidification (OA) impacts on marine
organisms caused by rapidly rising atmospheric carbon dioxide (CO2)
concentration is almost entirely limited to single species responses. OA
consequences for food web interactions are, however, still unknown.
Indirect OA effects can be expected for consumers by changing the
nutritional quality of their prey. We used a laboratory experiment to test
potential OA effects on algal fatty acid (FA) composition and resulting
copepod growth. We show that elevated CO2 significantly changed the FA
concentration and composition of the diatom *Thalassiosira pseudonana*,
which constrained growth and reproduction of the copepod *Acartia tonsa*. A
significant decline in both total FAs (28.1 to 17.4 fg cell-1) and the
ratio of long-chain polyunsaturated to saturated fatty acids (PUFA:SFA) of
food algae cultured under elevated (750 µatm) compared to present day (380
µatm) *p*CO2 was directly translated to copepods. The proportion of total
essential FAs declined almost tenfold in copepods and the contribution of
saturated fatty acids (SFAs) tripled at high CO2. This rapid and reversible
CO2-dependent shift in FA concentration and composition caused a decrease
in both copepod somatic growth and egg production from 34 to 5 eggs female-1day
-1. Because the diatom-copepod link supports some of the most productive
ecosystems in the world, our study demonstrates that OA can have
far-reaching consequences for ocean food webs by changing the nutritional
quality of essential macromolecules in primary producers that cascade up
the food web.

------------------------

And toward the bottom of the text in this study:

Our study suggests that OA can have important consequences for consumer
growth and production by affecting the nutritional quality of primary
producers that translates to higher trophic levels. These results are
consistent with experiments on freshwater cladocerans, fed with algae from
an acidic lake [37]<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#pone.0034737-Locke1>,
suggesting that our results are not restricted to monospecific laboratory
cultures and may be expected at community level. However, future
experimental manipulations are required to clarify the widespread response
of phytoplankton biochemical composition to ocean acidification at relevant
*p*CO2 levels in other taxonomic groups and natural communities. It can be
expected that trophic upgrading and differential algae sensitivity to
*p*CO2at the community and ecosystem level may compensate for low food
quality
observed at the single species level. Moreover, the tolerance to *p*CO2 and
pH might be lower for monocultures compared to natural populations, which
have high ecophysiological variability
[38]<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#pone.0034737-Paasche1>and
genetic diversity, important for adaption to various environmental
factors [39]<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#pone.0034737-Sunday1>.
Nonetheless, shifts in FA composition as a response to changing CO2 have
been documented in other phytoplankton species
[26]<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#pone.0034737-Sato1>,
[40]<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#pone.0034737-Riebesell5>,
and FA-responses in phytoplankton as observed here might be important
during bloom periods if CO2 sensitive organisms dominate.

The effect of OA on nutritional quality in the diatom-copepod food chain
relationship observed in our study may have far reaching consequences for
food webs since FAs originating in phytoplankton are sequentially
incorporated into the total lipid fraction of zooplankton and
triacylglycerol of larval fish
[41]<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#pone.0034737-Fraser1>.
Given that fish is a critical natural resource
[42]<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#pone.0034737-Food1>,
acidification-driven food quality deterioration may impair fish production
by changing the biochemical composition of food algae and its transfer to
higher trophic levels
[43]<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#pone.0034737-Kang1>,
[44]<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034737#pone.0034737-Fabry1>.
While it is difficult to extrapolate from monocultures to community level,
these results point to the likelihood that OA consequences go beyond direct
physiological impacts and that indirect effects through trophic
interactions need to be considered.

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Vision2020 Post: Ted Moffett
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