Seabed disturbance releases carbon and reduces oxygen

The seabed stores vast amounts of carbon and nutrients, much more than the amount of carbon dioxide in the atmosphere. A new study, published in "Estuarine, Coastal and Shelf Science", reveals that repeated disturbances of the seabed, such as those caused by fishing and dredging activities, release stored carbon and nitrogen into the ocean. This release contributes to carbon dioxide emissions and depletes oxygen levels near the seabed.

According to senior researcher Christian Lonborg from Aarhus University's Institute for Ecoscience, "Researchers have long assumed that physical disturbances of the seabed, such as from fishing equipment like trawling, increase the conversion of organic carbon into carbon dioxide, but theoretical models have lacked documentation in the form of measured values. We have now shown through laboratory experiments that this is indeed the case."

The research team demonstrated that seabed disturbances increase carbon conversion and nitrogen release. As these elements are stirred into the water column, they accelerate organic material degradation, leading to additional carbon dioxide emissions - a factor that aggravates global climate concerns.

The release of nutrients from disturbed sediments can also stimulate algal growth, leading to an influx of organic carbon. This increased organic activity consumes more oxygen, worsening oxygen conditions in waters near the seabed, particularly during the late summer in Danish waters. "If we are to assess the impact of trawling equipment, dredging, and extraction of raw materials from the seabed, these consequences must also be considered," Lonborg added.

Research Report:Impacts of anthropogenic resuspension on sediment organic matter: An experimental approach