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P E R S E O Macroecological patterns
in marine phytoplankton |
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A research project funded by Ministerio
de Ciencia e Innovación (CTM2008-03999) |
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Background
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Phytoplankton
constitute the basis of the ecological food web in most marine ecosystems and
therefore play a major role in regulating the exchange of carbon dioxide
between the ocean and the atmosphere, as well as in sustaining upper trophic
levels. Two main factors, size structure and taxonomic composition, are the
key determinants of the ecological and biogeochemical role of phytoplankton,
and both can be altered by current and future processes of global change.
Hence, there is a pressing need to determine the factors that control
phytoplankton size structure and taxonomical composition and to characterize
general macroecological patterns of phytoplankton abundance, diversity and
metabolism in the ocean. Our project stems from the general hypothesis that
nutrient supply determines the size structure and functional group
composition of phytoplankton communities, and therefore the trophic and
biogeochemical functioning of pelagic ecosystems. We will address this
hypothesis using laboratory experiments with monospecific cultures, field
observations across a coast to shelf productivity gradient, and nutrient
addition experiments with natural assemblages. These observations and
experiments will allow us to construct allometric models relating cell size
to the main metabolic rates in phytoplankton (photosynthesis, nutrient
uptake, respiration, exudation, cell lysis) and to identify macroecological
patterns linking nutrient supply, phytoplankton metabolism and community
structure. |
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Emilio Marañón (PI) |
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1. To determine the
size-scaling relationships for key metabolic processes in phytoplankton
across a wide range of cell sizes and taxonomic affiliations. 2. To test the
hypothesis that the size-scaling of metabolic rates in phytoplankton follows
the ¾-power rule. 3. To determine general
macroecological patterns of size- and taxon-dependent phytoplankton metabolic
rates over a wide range of productivity conditions. 4. To test the hypothesis
that nutrient supply controls the response and ecological success of
different phytoplankton size classes and functional groups. 5. To determine general
macroecological patterns that relate water column structure and nutrient
availability to phytoplankton abundance, diversity and size-structure. |
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Work package 1. Size-
and taxon-dependent metabolism in monospecific cultures. This WP aims to determine the size-scaling
relationships for critical metabolic rates (both anabolic and catabolic) in
optimal and sub-optimal growth conditions across a wide range of cell sizes
and considering also a variety of taxonomic groups. This work package will
allow us to test the hypothesis that the size-scaling of metabolic rates in
phytoplankton frequently deviates from the predictions of the general
allometric theory due to taxon-related changes in resource uptake and use. Work package 2. Field
observations and database analyses. The objective of this WP is to determine general
patterns of size- and taxon-dependent phytoplankton abundance and metabolism
across a range of productivity conditions. Measurements will be carried out
during the upwelling-favourable season in the Ría de Vigo and also in the adjacent
shelf. In addition, measurements will also be conducted during open-ocean
transects taking advantage of cruises already programmed within the framework
of other projects. The analysis of existing databases will also be used to
extract general patterns relating hydrodynamics with phytoplankton cell size,
abundance, and metabolic rate. Work package 3.
Nutrient addition experiments with natural assemblages. By performing realistic nutrient addition
experiments to natural phytoplankton assemblages, we will test the hypothesis
that nutrient supply dynamics (rate of nutrient supply, amount of nutrient
added and frequency of pulses) control the response and ecological success of
different phytoplankton size classes and functional groups. In particular, we
will test the hypothesis that the variability in nutrient supply rates,
rather than just the total amount of nutrients available, is a critical
factor controlling the competitive success of diatoms. |
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WP1. We have
determined carbon and nitrogen cell quotas, growth rates and key metabolic
rates (photosynthesis, exudation, respiration, nutrient uptake) in >20
different species spanning >7 orders of magnitude in cell size, and
including cyanobacteria, chlorophytes, coccolithophores, dinoflagellates and
diatoms. Measurements were done during both the exponential growth and the
senescent phases. |
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WP2. We have conducted
8 sampling visits to stations in the Ría de Vigo and in the adjacent shelf
during May – July 2010. On each visit, we collected samples to determine
phytoplankton abundance, composition and size structure, together with the
rates of carbon fixation, exudation and respiration. Additional measurements
of phytoplankton abundance, size structure and metabolism have been collected
during large-scale transects in the Mediterranean Sea and in the tropical |
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WP3. We are currently
setting up a system of continuous cultures (chemostats) that will be used to
conduct experiments on the effect of temperature, nutrient supply and CO2 levels on phytoplankton
metabolism. |
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Huete-Ortega, M., Marañón, E., Varela, M., Bode, A.
(2010) General
patterns in the size scaling of phytoplankton abundance in coastal waters
during a 10-year time series. Journal
of Plankton Research, 32, 1-14. |
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López-Sandoval, D. C., Fernández, A., Marañón, E.
(2011) Dissolved
and particulate primary production along a longitudinal gradient in the
Mediterranean Sea. Biogeosciences,
8, 815-825. |
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Huete-Ortega, M., Calvo-Díaz, A., Mouriño-Carballido,
B., Graña, R., Marañón, E. (2011) Effect
of environmental forcing on the biomass, production and growth rate of
size-fractionated phytoplankton in the central Atlantic. Journal of Marine Systems, 88, 203-213. |
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Huete-Ortega, M., Cermeño, P., Calvo-Díaz, A.,
Marañón, E. (2011) Isometric
size-scaling of metabolic rate and the size abundance distribution of
phytoplankton. Proceedings of the
Royal Society B, doi:10.1098/rspb.2011.2257. |
Last updated December 2011