“Tropical coastal ecosystems, such as coral reefs, are oligotrophic, meaning they are located in nutrient-poor waters and have adapted to those conditions,” said Madeline Berger, a researcher at the National Center for Ecological Analysis.
In a paper published in the journal Ocean and Coastal Management, leader Berger and his colleagues address the challenge of nutrient contaminants through a case study off the coast of Central America. The result? Farms are to blame for the vast majority of nitrogen pollutants flowing into the Mesoamerican reef region. Knowing where contaminants come from, according to the researchers, will help managers adapt mitigation solutions.
“Our study highlights that other control methods will want to be used in other watersheds to decrease nutrient intake that may have adverse effects on the fitness of coral reefs and seagrass beds in this area,” Berger said.
The Mesoamerican Reef (MAR) is the largest barrier reef in the Western Hemisphere, just behind Australia’s Great Barrier Reef in terms of size. Shared across Mexico, Belize, Guatemala, and Honduras, it stretches nearly 700 miles and is home to a variety of creatures, adding plenty of fish species, critically endangered sea turtles, as well as mollusks, marine mammals, and shorebirds. . These habitats and communities, in turn, support local fishing and tourism. Millions of other people flock each year to the resorts and ports of Cancun, Cozumel, Belize City and other themes along the coast for their Caribbean vacations.
But the reef is also in trouble. More than one part is in poor condition due to threats, adding to ocean warming, unsustainable fishing and pollution.
“Nutrient contaminants are a known risk to coral reefs and seagrass meadows,” Berger said. or kill fish and other animals. Water quality disorders are also among the main reasons for white syndrome, a pathogenic disease that causes white lesions that spread to coral and lead to death in just a few weeks. Nutrient contaminants in this region, according to the researchers, “come from 4 sources: agricultural production, human wastewater, atmospheric deposition, and excrement,” and agriculture and human wastewater are suspected of contributing to most pollutants.
To find out how much of the pollutants came from upstream agriculture or human water, the researchers dove into several styles that examined the watersheds that feed the MAR. and known rates of nitrogen excretion across humans, which has been adapted to that express region.
“Another NCEAS organization is also creating a spatially particular global style that quantifies the ecological footprint of food production, so we saw an opportunity to synthesize the two styles to compare the nutrient contaminants of tea water with the nutrient contaminants of agricultural and animal production,” Berger said.
The researchers also modeled the effects of the millions of tourists visiting the coast using hotel location data, cruise ship shipping location data, and monthly statistics reported through each country’s tourism offices. which turns out to be quite complicated,” he said.
The researchers found that agriculture is by far the largest contributor (92%) of nitrogen to the SEA, due to runoff from fertilizers and livestock traveling into the ocean through rivers and streams. Two rivers, the Ulúa River in Honduras and the Motagua River in Guatemala contributed more than 50% of the modeled nitrogen pollutants, collecting runoff from several tributaries upstream and flowing into the ocean. Meanwhile, 90% of the modeled nitrogen pollutants have been attributed to 20 (out of 430) watersheds, 11 of which are located in Guatemala or Honduras. An estimated 80% of coral reefs and 68% of seagrass beds have been exposed to nitrogen pollutants from watershed plumes.
The findings are indicative of the complexity of the pollutants challenge: Even adjustments in land use and inland agricultural expansion can have effects on marine ecosystems, Berger said. coastal watersheds. And while tourism accounted for a very small proportion of the total pollutants, watersheds that contributed the most to pollutants also tended to have a higher number of tourists or be close to those that did.
“The exercise also raised the question of how tourists, or tourism demand, have greater effects beyond the mere physical presence of more people, such as a taller structure or the expansion of agriculture, which can also exacerbate the influx of pollutants,” Berger said. The researchers hope that ultimately, a granular technique that can be used to trace the origins and trajectories of nitrogen and other nutrients and their effects will allow coastal managers to expand the complicated action plans needed to mitigate pollutants in some of the world’s most biodiverse coastal areas. Regions.
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