Geoscience Reference
In-Depth Information
Phytoplankton today is sometimes utilized as
an ecological monitor of nutrient availability and
therefore of eutrophication events associated with
pollution or periodic upwelling. It is certainly the
case that the distribution of phytoplankton biomass
is correlated with nutrient from both upwelling
and terrestrial runoff. We should not confuse pro-
ductivity in ecological time with speciation in the
geological past, however. Algal phylogeny, when
compared to variations in Rubisco efficiency, indi-
cate that the algae were subjected to selection
pressure that concerned CO
2
uptake (Tortell 2000;
Strother 2008). The very existence today of CCMs
that extract CO
2
from inorganic HCO
3
2
is an indi-
cation that the necessity of getting CO
2
to the
active site of carbon fixation was a factor in the evol-
ution of photosynthetic organisms on Earth. The
correlation between pCO
2
levels and cyst-forming
phytoplankton during the Palaeozoic confirms that
the phytoplankton evolution was indeed sensitive
to past pCO
2
levels.
The terrestrial and marine biospheres today are
clearly linked through the carbon cycle and atmos-
pheric CO
2
. That they show such strong correlations
in the past, especially during the establishment of
near-modern levels of carbon distribution during
the terrestrialization process, is not surprising.
However, the likely correlation between pCO
2
and
both terrestrial and marine proxies for biosphere
evolution as noted here has not been emphasized
in prior studies of correlated evolution between
the terrestrial and marine realms (Vermeij 1987;
Bambach 1993; Martin 1996). Our observations
point out that pCO
2
may have been a substantial
environmental forcing factor contributing to the
evolution of the large marine phytoplankton
during the Palaeozoic.
evolution of land plants, weathering processes, and
marine anoxic events. Philosophical Transactions of
the Royal Society of London, B353, 113-130.
Algeo, T. J., Berner, R. A., Maynard,J.B.&Scheck-
ler, S. S. 1995. Late Devonian oceanic anoxic events
and biotic crises: 'Rooted' in the evolution of vascular
land plants? GSA Today, 5, 45, 64-66.
Algeo, T. J., Scheckler,S.S.&Maynard, J. B. 2001.
Effects of the Middle to Late Devonian spread of vas-
cular land plants on weathering regimes, marine biotas
and global climate. In: Gensel,P.G.&Edwards,D.
(eds) Plants Invade the Land: Evolutionary and
Environmental Perspectives. Columbia University
Press, New York, 213-236.
Bambach, R. K. 1993. Seafood through time: changes in
biomass, energetics, and productivity in the marine
ecosystem. Paleobiology, 19, 372-397.
Beck,J.H.&Strother, P. K. 2008. Spores and cryptos-
pores from a Silurian section near Allenport, Pennsyl-
vania. Journal of Paleontology, 82, 857-883.
Berner, R. A. 2001. The effect of the rise of land plants on
atmospheric CO
2
during the Paleozoic. In: Gensel,
P. G. & Edwards, D. (eds) Plants Invade the Land:
Evolutionary and Environmental Perspectives. Colum-
bia University Press, New York, 173-178.
Berner, R. A. 2004. The Phanerozoic Carbon Cycle.
Oxford University Press, Oxford.
Berner,R.A.&Kothavala, Z. 2001. GEOCARB III: a
revised model of atmospheric CO
2
over Phanerozoic
time. American Journal of Science, 301, 182-204.
Brovkin, V., Bendtsen, J., Claussen, M., Ganopolski,
A., Kubatzki, C., Petoukhov,V.&Andreev,A.
2002. Carbon cycle, vegetation and climate dynamics
in the Holocene: experiments with the CLIMBER-2
model. Global Biogeochemical Cycles, 16, 86-120.
Collins,S.&Bell, G. 2004. Phenotypic consequences of
1000 generations of selection at elevated CO
2
in a
green alga. Nature, 431, 566-569.
Driese,S.G.&Mora, C. I. 2001. Diversification of
Siluro-Devonian plant traces in paleosols and influence
on estimates of paleoatmospheric CO
2
levels. In:
Gensel,P.G.&Edwards, D. (eds) Plants Invade
the Land: Evolutionary and Environmental Perspec-
tives. Columbia University Press, New York,
237-253.
Edwards, D., Feehan,J.&Smith, D. G. 1983. A late
Wenlock flora fromCounty Tipperary, Ireland. Botani-
cal Journal of the Linnean Society, 86, 19-36.
Elick, J. M., Driese,S.G.&Mora, C. I. 1998. Very large
plant and root traces from the Early to Middle Devo-
nian; implications for early terrestrial ecosystems and
atmospheric p(CO
2
). Geology, 26, 143-146.
Falkowski,P.&Raven, J. 1997. Aquatic Photosynthesis.
1st edn. Blackwell Science, Malden, Mass.
Falkowski,P.&Raven, J. 2007. Aquatic Photosynthesis.
2nd edn. Princeton University Press, Princeton, NJ.
Fensome, R. A., Williams, G. L., Barss, M. S., Freeman,
J. M. &Hill, J. M. 1990. Acritarchs and fossil prasino-
phytes: an index to genera, species and infraspecific
taxa. AASP Contribution Series, 25, 1-771.
Gensel, P. G., Kotyk,M.E.&Basinger, J. F. 2001.
Morphology of above- and below-ground structures
in Early Devonian (Pragian-Emsian) plants. In:
Gensel,P.G.&Edwards, D. (eds) Plants Invade
A chance encounter on an English train led to support for
the senior author as a Professeur invit
´
at Universit
´
des
Sciences et Technologies de (Lille 1), France. This support,
along with discussions with T. Danelian and other col-
leagues in G
´
osyst
`
mes, is gratefully acknowledged.
Additional funds for this research were provided by
ECLIPSE-CNRS and C. Lenk. J. Michaud was responsible
for initial data processing to produce taxon-richness curves
from the Palynodata files. PKS would also like to thank
J. Williams at the Natural History Museum in London
for the unfettered use of his library and database. The com-
ments of the reviewers, P. Kenrick and R. Wicander, were
helpful in improving the manuscript. However, not all of
the content of the manuscript is in agreement with their
views. Finally, we would like to thank our editor,
B. Meyer-Berthaud, for both her patience and clarification
of some fundamental palaeobotanical issues.
References
Algeo,T.J.&Scheckler, S. S. 1998. Terrestrial-marine
teleconnections in the Devonian: Links between the
