Toward an assessment of ocean acidification in the Adriatic sea and impact on the biogeochemistry of marine carbonate system

The increase of CO2 amount in the atmosphere has created great concern: it will in all probability result in changes in temperature, precipitation and/or their seasonal amplitudes with consequences not only on sea level rise but also on chemical equilibrium of the CO2 system in seawater, mainly reducing pH and carbonate ion concentration (Ocean Acidification). The process is now well documented in field data from all around the world. However is not sufficiently witnessed in the Mediterranean Sea, due to the scarcity of good quality data. On this concern, results for the Adriatic Sea are presented: from experimental measures of pH and total alkalinity, two seasonal pictures of pH and carbonate system parameters have been drawn. In addition, a pH decrease of 0.063pHT units with related chemistry changes has been inferred in the North Adriatic Dense Water (NAdDW) over the two last decades. These results, although preliminary, merit attention as confirm that N. A. sea has been affected by OA, being sensitive to the climate forcing. Potential impacts of OA are several and should be assessed, as many might even exacerbate hyopoxia/anoxia events, already affecting the area. OA might also affetc the food web, as the carbonate reduction has the potential to alter the distribution and abundance of marine organisms that use calcium carbonate to build their shells or skeletons (corals, plankton) and the organisms that depend on them for survival (fishes, marine mammals).

Effect of ocean acidification on early life stages of Atlantic herring (Clupea harengus L.)(update)

Due to atmospheric accumulation of anthropogenic CO₂ the partial pressure of carbon dioxide (pCO₂) in surface seawater increases and the pH decreases. This process known as ocean acidification might have severe effects on marine organisms and ecosystems. The present study addresses the effect of ocean acidification on early developmental stages, the most sensitive stages in life history, of the Atlantic herring (Clupea harengus L.). Eggs of the Atlantic herring were fertilized and incubated in artificially acidified seawater (pCO₂ 1260, 1859, 2626, 2903, 4635 μatm) and a control treatment (pCO₂ 480 μatm) until the main hatch of herring larvae occurred. The development of the embryos was monitored daily and newly hatched larvae were sampled to analyze their morphometrics, and their condition by measuring the RNA/DNA ratios. Elevated pCO₂ neither affected the embryogenesis nor the hatch rate. Furthermore the results showed no linear relationship between pCO₂ and total length, dry weight, yolk sac area and otolith area of the newly hatched larvae. For pCO₂ and RNA/DNA ratio, however, a significant negative linear relationship was found. The RNA concentration at hatching was reduced at higher pCO₂ levels, which could lead to a decreased protein biosynthesis. The results indicate that an increased pCO₂ can affect the metabolism of herring embryos negatively. Accordingly, further somatic growth of the larvae could be reduced. This can have consequences for the larval fish, since smaller and slow growing individuals have a lower survival potential due to lower feeding success and increased predation mortality. The regulatory mechanisms necessary to compensate for effects of hypercapnia could therefore lead to lower larval survival. Since the recruitment of fish seems to be determined during the early life stages, future research on the factors influencing these stages are of great importance in fisheries science.

Understanding the impacts of ocean acidification remains a key challenge

Climate change or no climate change, there is one consequence that is in no doubt: As the concentration of CO2 in the atmosphere increases, so will its concentration in the ocean – resulting in ocean acidification.

When CO2 dissolves in seawater it reacts to form a number of ionic and non-ionic  carbon species depending on  the temperature and alkalinity.  The net effect is to increase the concentration of hydrogen ions (H+) and reduce the concentration of carbonate ions  (CO3 2– ). More H+ ions mean lower pH and more acidic conditions; so as more and more CO2  dissolves into the  ocean, the ocean is becoming  more and more acidic. Reducing the carbonate ions means that  calcifying organisms, those that  form shells and coral reefs, have  to spend increasing amounts  of energy on this activity, at  the expense of growth and  reproduction causing long-term  changes to ecosystem structure  and function.

Funding opportunity: Regional ecosystem prediction program: Potential impacts of ocean acidification on fishery ecosystems

NOAA/NOS/NCCOS/CSCOR is accepting proposals which address the potential ecosystem impacts of ocean acidification to fishery ecosystems of US waters. Research should focus on the development of ecological models (linked to biogeochemical models if possible) which can be used to predict population and/or ecosystem level effects (including potentially, socioeconomic impacts) of increasing ocean acidification on a) important US commercial and recreational fishery species and/or b) key organisms in the ecosystems on which these fishery species rely (e.g., zooplankton, forage fish).

Funding limits for individual projects are approximately $200,000 to $400,000 per year lasting up to 3 years.

Leibniz Prize 2012 to honor outstanding researcher Prof. Dr. Ulf Riebesell

Prof. Dr. Ulf Riebesell (52), Oceanography, Leibniz Institute of Marine Sciences (IFM-GEOMAR) at University of Kiel

Ulf Riebesell receives the Leibniz Prize for his research on ocean change, one of the farthest-reaching corollaries and consequences of human-induced climate change. This marine scientist from Kiel was one of the first researchers to examine the influence of acidification and ocean warming on marine organisms and ecosystems. He focused especially on plankton and other calcareous and calcifying organisms in the ocean. In his experimental work — initially in the laboratory and later with free-drifting mesocosms in the Baltic Sea, Norwegian fjords and the Arctic — Riebesell was able to show how increased uptake of carbon dioxide from the atmosphere reduces the pH value in oceans and the ability of calcareous organisms to produce shells. Because these organisms are often at the beginning of the food chain, this may have a material impact on the entire food chain and production in the ocean. With his work, Riebesell has made not only marine scientists but also the general public aware of ocean acidification as one of the most acute threats to marine ecosystems.