The domino effects of the ocean acidification

The domino effects of the ocean acidification

This barely known process raises major questions about the future of marine organisms. The German Institute AWI works to monitor species dynamics through the international project BIOACID.

Ocean acidification is an ongoing phenomenon developed as a result of an increase in the atmospheric CO2. Not as widely known as global warming, yet it has equally important consequences : the ocean pH rises and rises, creating an unbalance between bicarbonates and carbonic acid, leaving less carbonate available for marine organisms such us sea urchins or corals, that build their shells from calcium carbonate. The acidification phenomenon also affects the carbon use efficiency amongst producers (microalgae) which can experiment a decline in the quality of the food for primary consumers (herbivore zooplankton) and hence, affect higher trophic levels. This is an interview with Maria Algueró, marine biologist, whose research is focused on the consequences of OA on mesozooplankton, in the frame of the BIOACID project. She works for the AWI(Alfred Wegener Institute for Marine and Polar Research) in the BAH, the Biological Institute located in the small island of Helgoland, 60 km far from the continent, in the North Sea.

What have been the main guidelines of the BAH (Biological Institute of Helgoland) in marine research since its creation? M. Algueró: The main goal of the BAH is to understand how different species interact within the shallow seas ecosystem. For example, Helgoland Roads is a long-term monitoring program that has been documenting the input of harmful substances and nutrients into the North Sea since the 1960s. And the European lobster is one of the stars in the station! The stock of this species decreased during the II World War because of the shelling over the island. One of the aims of laboratory tests is to increase lobster stocks around Helgoland in cooperation with local fishermen. The key question tackled by our research unit, the Shelf Sea Systems Ecology, is how North Sea ecosystems are influenced by anthropomorphic pressure, particularly by climate change. Thus, my research topic is the influence of the ocean acidification among the mesozooplankton, focusing on jellyfish and copepods.

Acartia tonsa, copepod.

Your Work Package assesses the direct and indirect effects of OA on the trophic chains. What kind of experiences do you conduct? M.Algueró: My working package aims for the response of subtropical Atlantic (Gran Canaria, Spain) and North Sea (Gullmar Fjord, Sweden) mesozooplankton to ocean acidification. We will investigate how mesozooplankton is affected by ocean acidification in those two different ecosystems: eutrophic (North Sea) and oligotrophic (Gran Canaria). The effects can be direct, such as changes in physiology and metabolism associated with increases in CO2 and/or decreases in pH, or indirect ones, as those based on the unbalanced biochemical composition of autotroph production and trophic interactions. But here at the BAH I also carry out several experiments culturing Rhodomonas salina (unicellular algae) and Acartia tonsa (copepod), and sampling jellyfish from the field. Most of times, jellyfish polyps are difficult to find, so we harvest the adults from the field, we induce larvae in the laboratory, and then we leave these to settle and develop into polyps. Chrysaora hysoscella, also known as compass jellyfish

What are the main consequences of OA on phytoplankton and zooplankton?

M. Algueró: What a difficult question… That’s the reason that the BIOACID project is developing the longest cosmos experiment ever! Till now, most of the lab and field experiments searching for answers about the effect of CO2 over particular species were short-term experiments. But then, information about reactions and adaptations of natural complex biological communities to ocean acidification could not be answered. That’s what we are trying with the mesocosmos sites till next June in the Gullmar Fjord, in Sweden. These ten 55.000L plastic bags, enclosed in their bases by sediment traps, are placed in the Swedish fjord, so they can conduct the first long-term mesocosmos experiment in the natural environment… Maybe I could better answer your question when I will get my results once I will finish this experiment…

So, the ocean pH is getting lower and lower. Is there any action that could be taken to try to reverse this process?

M.Algueró: In fact, you can find some studies about the iron fertilization in the ocean, in order to stimulate photosynthesis in phytoplankton. Personally, I think that it could solve some local problems, but the ocean doesn’t behave the same way all around the globe. And the coastal communities are really complex… Local and personal actions on land can play an important role on ocean acidification of coastal waters. A good exercise is to calculate our own CO2 fingerprint, which measures the CO2 emissions that we produce every single day. It is difficult to change our habits, but again, it is just a question of adaptation and global commitment.