Reduced calcification decreases photoprotective capability in the coccolithophorid Emiliania huxleyi

Intracellular calcification of coccolithophores generate CO₂ and consumes additional energy for acquisition of calcium and bicarbonate ions, therefore, it may correlate with photoprotective processes by influencing the energetics. To address this hypothesis, a calcifying Emiliania huxleyi strain (CS-369) was grown semi-continuously at reduced (0.1 mM, LCa) and ambient Ca²⁺ concentrations (10 mM, HCa) for 150 days (>200 generations). The HCa-grown cells had higher photosynthetic and calcification rates and higher contents of chl a and carotenoids compared to the naked (bearing no coccoliths) LCa-grown cells. When exposed to stress-full levels of PAR, LCa-grown cells displayed lower photochemical yield and less efficient non-photochemical quenching (NPQ). When the LCa or HCa-grown cells were inversely shifted to their counterpart medium, LCa to HCa transfer increased photosynthetic carbon fixation (P), calcification rate (C), C/P ratio, NPQ and pigments contents, while those shifted from HCa to LCa exhibited the opposite performance. Increased NPQ, carotenoids and quantum yield clearly linked with increased or sustained calcification in E. huxleyi. The calcification must have played a role in dissipating excessive energy or as an additional drainage of electrons absorbed by the photosynthetic antennae. This phenomenon was further supported by testing two noncalcifying strains, which showed insignificant changes photosynthetic carbon fixation and NPQ when transferred to LCa condition.

Climate change threatens crucial marine algae

UXBRIDGE, Canada, May 8 (IPS) – Without major reductions in the use of fossil fuels, sunlight is to kill an unknown number of ocean phytoplankton, the planet’s most important organism, a new study reports this week.Not only are phytoplankton, also known as marine algae, a vital component in the ocean’s food chain, they generate at least half of the oxygen we breathe.

In the not so distant future, sunlight, the very source of life for phytoplankton, will likely begin to kill them because of the ocean’s increasing acidity, researchers from China and Germany have learned.

“There’s a synergistic effect between increased ocean acidity and natural light,” says Ulf Riebesell of the Helmholtz Centre for Ocean Research in Kiel, Germany.

Rising CO2 and increased light exposure synergistically reduce marine primary productivity

Carbon dioxide and light are two major prerequisites of photosynthesis. Rising CO₂ levels in oceanic surface waters in combination with ample light supply are therefore often considered stimulatory to marine primary production^{1, 2, 3}. Here we show that the combination of an increase in both CO₂ and light exposure negatively impacts photosynthesis and growth of marine primary producers. When exposed to CO₂ concentrations projected for the end of this century⁴, natural phytoplankton assemblages of the South China Sea responded with decreased primary production and increased light stress at light intensities representative of the upper surface layer. The phytoplankton community shifted away from diatoms, the dominant phytoplankton group during our field campaigns. To examine the underlying mechanisms of the observed responses, we grew diatoms at different CO₂ concentrations and under varying levels (5–100%) of solar radiation experienced by the phytoplankton at different depths of the euphotic zone. Above 22–36% of incident surface irradiance, growth rates in the high-CO₂-grown cells were inversely related to light levels and exhibited reduced thresholds at which light becomes inhibitory. Future shoaling of upper-mixed-layer depths will expose phytoplankton to increased mean light intensities⁵. In combination with rising CO₂ levels, this may cause a widespread decline in marine primary production and a community shift away from diatoms, the main algal group that supports higher trophic levels and carbon export in the ocean.

Impacts of ocean warming and acidification on the larval development of the barnacle Amphibalanus improvisus

The world’s oceans are warming and becoming more acidic. Both stressors, singly or in combination, impact marine species, and ensuing effects might be particularly serious for early life stages. To date most studies have focused on ocean acidification (OA) effects in fully marine environments, while little attention has been devoted to more variable coastal ecosystems, such as the Western Baltic Sea. Since natural spatial and temporal variability of environmental conditions such as salinity, temperature or pCO₂ impose more complex stresses upon organisms inhabiting these habitats, species can be expected to be more tolerant to OA (or warming) than fully marine taxa. We present data on the variability of salinity, temperature and pH within the Kiel Fjord and on the responses of the barnacle Amphibalanus improvisus from this habitat to simulated warming and OA during its early development. Nauplii and cyprids were exposed to different temperature (12, 20 and 27 °C) and pCO₂ (nominally 400, 1250 and 3250 μatm) treatments for 8 and 4 weeks, respectively. Survival, larval duration and settlement success were monitored. Warming affected larval responses more strongly than OA. Increased temperatures favored survival and development of nauplii but decreased survival of cyprids. OA had no effect upon survival of nauplii but enhanced their development at low (12 °C) and high (27 °C) temperatures. In contrast, at the intermediate temperature (20 °C), nauplii were not affected even by 3250 μatm pCO₂. None of the treatments significantly affected settlement success of cyprids. These experiments show a remarkable tolerance of A. improvisus larvae to 1250 μatm pCO₂, the level of OA predicted for the end of the century.

This is your ocean on acid

As emissions continue to rise, the world’s oceans are becoming corrosive, threatening shellfish, corals and the entire ocean food web

On most days, Bill Dewey can be found wearing waist-high waders and inspecting Manila clams—the West Coast version of the littleneck—at his Washington clam farm, Chuckanut Shellfish. Under an arrangement that’s unique to the state, Dewey owns 32 acres of tidelands. Unlike land-based farms, he can only harvest when the tide recedes, leaving over a mile of mudflats, and shellfish, exposed. He gathers the clams with the help of a former tulip-bulb harvesting machine that’s carried out aboard his boat, the Clamdango!

What is an ocean acidification data set and what are the minimum core variables?

The interagency ocean acidification data management team is seeking community input on the definition of an ocean acidification data set. Please see details below and send your feedback to Hernan Garcia (hernan.garcia(at)noaa.gov) by May 18.