B-neutral certification recommended for sustainable fish farming
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by Giulia Granato and Mauro Doimi, Marine biologists, D&D Consulting, Italy
ost of human activities emit carbon dioxide (CO2), which contains atmospheric carbon. CO2, along with other emissions, have changed and is still changing global climate irremediably. What is not still well known is that our ocean, coasts and lagoons provide a natural way of reducing the impact of greenhouse gases on our atmosphere, through sequestration (or sinking) of this carbon. 83 percent of the global carbon cycle is circulated through the ocean. Coastal habitats cover less than two percent of the total ocean area, but account for approximately 50 percent of the total carbon sequestered in ocean sediments. The term used for carbon captured by marine ecosystems is called “Blue carbon”. Carbon is taken by living organisms that store it in an organic form, like mud sediments or for building clam shells. Mangroves, salt marshes and seagrass “capture and hold” large quantities of carbon, acting as something called a “blue carbon sink”. Fish farming is directly involved in the carbon cycle and can be positive in emissions or negative in the sink. Extensive aquaculture made in wetlands or in brackish lagoons proved to be an efficient blue carbon sink. These ecosystems, strongly autotrophic, fix carbon dioxide photo-synthetically as organic matter and the excess of the CO2 is
respired back by biota, thus removing CO2 from the atmosphere and storing it below the ground. The CO2 cycle is complex and begins from its capture in the water by atmosphere and photosynthesis due to the macro-micro algae. The CO2 reacts with carbonate alkalinity in the brackish water and precipitates on the bottom. Moreover, the CO2 is captured by the mud due to the denitrification process and the chemical linkage with the cations and clay. It has been shown that the biomass production in brackish lagoons is higher than other blue ecosystems, like lakes or rivers, sequestering carbon at a much faster and bigger rate. Consequently, aquaculture in brackish lagoons plays a doubly important role: these ecosystems sequester tonnes of blue carbon and produce fish in a sustainable and organic way, whilst ensuring the conservation of the natural habitat. Fish are kept wild and live in perfect balance inside the lagoon food chain. Extensive aquaculture produces less negative ecological impacts on the environment: to the contrary other methods of fish farming like offshore cages produce organic waste, such as fish sewage, and do not remove it. Therefore, it is urgent to encourage every sustainable system that can mitigate climate change to protect the habitat which has a low “carbon footprint”. Fish farms in lagoons should be incorporated into the carbon market through the method of buying and selling carbon credit international called “carbon offsets”. A carbon offset is a reduction in emissions of carbon dioxide made in order
22 | June 2019 - International Aquafeed