Vasco Vieira in an interview with Greensavers

MARE researcher Vasco Vieira, author of the study “Seagrass space occupation efficiency is key for their role as ecosystem engineers and ecological indicators”, spoke to Greensavers about the ability of seagrasses to use nutrients of human origin. 

Seagrass beds are ecosystems found in coastal areas, lagoons, estuaries and lagoons, formed by highly productive seagrasses. As well as being a refuge for many animals, these ecosystems provide services such as atmospheric carbon sequestration and water purification.

Like other plants, seagrasses use the nutrients in the water and the availability of light to grow and spread. Researcher Vasco Vieira discovered that the presence of human-derived nutrients in moderate concentrations benefits the growth of seagrass beds. The MARE researcher, who studied seagrass beds in Brazil, Costa Rica, the United Kingdom and Portugal, concluded that “in pristine conditions”, i.e. without effluents of human origin, “the growth of seagrass is limited by the scarcity of nutrients”.

However, the researcher stresses that it is important not to exceed the toxicity limit, which promotes the proliferation of algae that prevent sunlight from penetrating, causing the prairies to die.

Many of these nutrients come from wastewater treatment plants, which treat wastewater before releasing it back into ecosystems, greatly reducing the negative effects on these environments. With these new conclusions from the study led by the MARE researcher, it will be possible to “reconcile seagrass meadows with water treatment”.

According to Vasco Vieira, “this means that we don't need to force the WWTP to send water that is 100% clean of nutrients, because the seagrass beds themselves can remove this excess of nutrients, and in a natural way”.

This new strategy will bring benefits not only to the ecosystem, by providing it with nutrients, but also to the WWTP itself, which will take less time to treat the water, consuming less energy and reducing its carbon footprint.

In addition, the researchers found a greater abundance of invertebrates in the River Tagus, which allowed them to conclude that “the seagrass in the Tagus is benefiting from nutrient discharges, either because the river comes with more fresh water in its flow that brings nutrients along its course, or those that come from agricultural effluents,” or from discharges from the WWTP or the food industry, he explains.

Despite the enormous importance of these ecosystems, seagrass meadows are highly threatened all over the world and Portugal is no exception. In the Tagus River, this ecosystem is fragmented due to bivalve trawling, which is highly destructive for these plants. "In the Tagus they're in decline, but it's not because of nutrients. It's because of illegal shellfish gatherers," says Vasco Vieira.

For the researcher, the solution lies in banning this unregulated activity, promoting practices such as aquaculture and the development of shellfish traps that don't damage the seagrass beds. However, he admits that this may be “unrealistic” and says that this is “a problem of coexistence” between unregulated shellfish gatherers and the conservation of seagrass beds, so the solution will lie with political decision-makers.

To read the interview click HERE