Israel: Environmental Pollution Researches Want to Reduce Nitrogen Levels in River Estuaries with Seaweed Farms

Due to agricultural emissions and wastewater from industry and households, nitrogen concentrations in estuaries are rising in many parts of the world. A team of international scientists shows that seaweed farms in river estuaries significantly reduce nitrogen concentrations and prevent environmental pollution.

Tel Aviv/Israel — A new study by Tel Aviv University and University of California, Berkeley proposes a model according to which the establishment of seaweed farms in river estuaries significantly reduces nitrogen concentrations in the estuary and prevents pollution in estuarine and marine environments.

As part of the study, the researchers built a large seaweed farm model for growing the ulva sp. green macroalgae in the Alexander River estuary, hundreds of meters from the open sea. The Alexander River was chosen because the river discharges polluting nitrogen from nearby upstream fields and towns into the Mediterranean Sea. Data for the model were collected over two years from controlled cultivation studies.

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Researchers explain that nitrogen is a necessary fertilizer for agriculture, but it comes with an environmental price tag. Once nitrogen reaches the ocean, it disperses randomly, damaging various ecosystems. As a result, the state local authorities spend a great deal of money on reducing nitrogen concentrations in water, following national and international conventions that limit nitrogen loading in the oceans, including in the Mediterranean Sea.

The laboratory of Prof. Alexander Golberg of the Porter School of Environmental and Earth Sciences is developing technologies for growing seaweed in the ocean in order to offset carbon and extract various substances, such as proteins and starches, to offer a marine alternative to terrestrial agricultural production. In a study, he and his team showed that if seaweed is grown according to the model they developed, in rivers’ estuaries, they can absorb the nitrogen to conform to environmental standards and prevent its dispersal in water and thus neutralize environmental pollution. The mathematical model predicts farm yields and links seaweed yield and chemical composition to nitrogen concentration in the estuary.

Apart from its ecological value, the seaweed also has an economic one, since it can be sold as biomass for human use. “In fact, we have developed a planning tool for setting up seaweed farms in estuaries to address both environmental problems while producing economic benefit. We offer the design of seaweed farms in river estuaries containing large quantities of agriculturally related nitrogen residues to rehabilitate the estuary and prevent nitrogen from reaching the ocean while growing the seaweed itself for food. In this way, aquaculture complements terrestrial agriculture”, says Goldberg.

References: Multi-scale modeling of intensive macroalgae cultivation and marine nitrogen sequestratio; Communications Biology; DOI: 10.1038/s42003-021-02371-z

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