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Publication
Seagrass photo-physiological responses in natural high-CO2 environment
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Advisor(s)
Abstract(s)
The atmospheric concentration of CO2 has been steeply increasing over the last 200 years,
with an associated increase of total dissolved inorganic carbon (Ci) and a decrease of the
oceans’ pH. Seagrasses are among the most productive marine ecosystems, but yet little
is known on the effects of high-CO2/low pH on their photosynthetic physiology and the
ecological consequences. Marine CO2 seepage areas have been used as natural laboratories
to investigate the performance of marine organisms under long-term exposure to high-CO2
levels that mimic the future ocean. In this work we conducted a series of experiments
comparing the photophysiology of the seagrasses Posidonia oceanica and Cymodocea
nodosa, growing in the vicinity of submarine CO2 vents around the islands of Vulcano and
Panarea (Aeolian Archipelago, Southern Tyrrhenian Sea, Italy). Plants growing close to
CO2-seepage sites were compared with plants from control sites. Automated chlorophyll
fluorometers were deployed for 24-hour periods to examine the changes in photosynthetic
efficiency and energy quenching mechanisms. Samples were collected at predawn and noon
and analyzed for pigment composition, antioxidant capacity, and soluble carbohydrates.
Differences in gene and protein expression were evaluated as a function of Ci levels. Stable
carbon isotopes (δ13C) were also analysed to investigate the contribution of volcanic CO2 to
seagrass productivity. Both P. oceanica and C. nodosa plants growing in CO2-seepage sites
showed lower allocation of PSII-absorbed energy to photochemistry (φII), while presenting
higher proportions of energy dissipation by non-photochemical pathways (down-regulation,
φNPQ and other energy losses, φNO). As well, diel photosynthesis-irradiance curves (ETRI),
built with data acquired over the 24-hour deployments, showed lower photosynthetic rates
in plants from CO2 seepage sites. This unexpected pattern of photosynthetic activity will be
discussed in light of the complementary data.
Description
Keywords
Seagrass High CO2 Photophysiology Cymodocea nodosa Posidonia oceanica CO2 vents ETR-I curve Photosynthesis
Citation
Silva J, Olivé I, Costa M, Barrote I, Procaccini G, Mazzuca S, Vizzini S, Santos R (2013) Seagrass photo-physiological responses in natural high-CO2 environment. Coastal and Estuarine Research Federation’s 22nd Biennial Conference, San Diego, California, EUA, p210.