Publication Date:
2024-03-15
Description:
In the high-nutrient, low-chlorophyll waters of the Gulf of Alaska, microcosm manipulation experiments were used to assess the effect of CO2 on growth and primary production under iron-limited and iron-replete conditions. As expected, iron had a strong effect on growth and photosynthesis. A modest and variable stimulation of growth and biomass production by CO2 (high CO2: 77-122 Pa; low CO2: 11-17 Pa) was observed under both iron-replete and iron-limited conditions, though near the limit of precision of our measurements in slow-growing low-iron experiments. Physiological acclimations responsible for the changes in growth were assessed. Under iron-limited conditions, growth stimulation at high CO2 appeared to result from an increase in photosynthetic efficiency, which we attribute to energy savings from down-regulation of the carbon concentrating mechanisms. In some cases, iron-rich photosynthetic proteins (PsbA, PsaC, and cytochrome b6) were down-regulated at elevated CO2in iron-limited controls. Under iron-replete conditions, there was an increase in growth rate and biomass at high CO2 in some experiments. This increase was unexpectedly supported by reductions in cellular carbon loss, most likely decreased respiration. We speculate that this effect may be due to acclimation to decreased pH rather than high CO2. The variability in responses to CO2 among experiments did not appear to be caused by differences in phytoplankton community structure and may reflect the sensitivity of the net response of phytoplankton to antagonistic effects of the several parameters that co-vary with CO2.
Keywords:
19-Butanoyloxyfucoxanthin; 19-Butanoyloxyfucoxanthin, standard deviation; 19-Hexanoyloxyfucoxanthin; 19-Hexanoyloxyfucoxanthin, standard deviation; Alkalinity, total; Aragonite saturation state; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chlorophyll a; Chlorophyll a, standard deviation; Chlorophyll b; Chlorophyll b, standard deviation; Colorimetry; Entire community; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Experimental treatment; Fluorometry; Fucoxanthin; Fucoxanthin, standard deviation; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); High Performance Liquid Chromatography (HPLC); Laboratory experiment; Micro-nutrients; Nitrate; North Pacific; OA-ICC; Ocean Acidification International Coordination Centre; Open ocean; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; pH, standard deviation; pH meter (Oakton); Phosphate; Photosynthetic protein, cytochrome, b6f; Photosynthetic protein, cytochrome, b6f, standard deviation; Photosynthetic protein, PsbA, standard deviation; Photosynthetic protein, PsbC; Photosynthetic protein, PsbC, standard deviation; Photosynthetic protein PsbA; Salinity; see reference(s); Silicon; Temperate; Temperature, water; Time, incubation
Type:
Dataset
Format:
text/tab-separated-values, 1001 data points
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