According to a new study, the United States' Atlantic Coast and eastern Gulf Coast are likely to see significant increases in nutrient loading in the coming decades, putting those areas at risk of harmful algal blooms.
Estuaries Face Higher Nutrient Loads In The Future
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Nutrient loadings are of particular interest because they are major contributors to algal blooms, which endanger both human health and the environment, as per ScienceDaily.
Blooms can produce toxins that are harmful to both human and animal life, depending on the type of algae.
Algal blooms also contribute to "dead zones," which are areas of water with insufficient oxygen to support a healthy ecosystem.
Furthermore, algal blooms can raise the cost of drinking water treatment and industrial sectors that rely on clean water.
Furthermore, the risk of algal blooms is increasing as temperatures rise due to global climate change.
"We know how important nutrient loadings are to ecosystem health, so we wanted to assess estuaries across the 48 contiguous states to see how vulnerable they are to increased nutrient loads," said Lise Montefiore, a postdoctoral researcher at North Carolina State University and co-corresponding author of a paper on the work.
The goal was to estimate average annual nutrient loads for estuaries between 2035 and 2065 using predictive modeling.
With the exception of the Mississippi River estuary, they were able to assess all major estuaries in the lower 48 states.
"One of the drivers for this study is that once an estuary has elevated nutrient loads, it is extremely difficult to restore that estuary," said Natalie Nelson, co-corresponding author and assistant professor of biological and agricultural engineering at NC State.
It's more effective to prevent high nutrient loads from occurring in the first place than it is to address nutrient loading problems once they've occurred, so they wanted to assist policymakers in identifying which systems are most vulnerable and could benefit significantly from conservation efforts to prevent increased nutrient loads.
Researchers used historical data as well as existing research to forecast land use and climate conditions for the continental United States between 2035 and 2065.
This information was then fed into a model that predicted annual average nitrogen and phosphorus loads for 112 estuaries in the lower 48 states.
The model was applied to the time periods 1990-2020 and 2035-2065 by the researchers.
To help put the modeling results into context, the researchers also assessed each estuary's sensitivity to increased nutrient loads.
The researchers used existing research to classify estuaries based on how much their conditions are likely to deteriorate if nutrient loads increased.
The researchers also assessed each estuary's "adaptive capacity," which essentially accounts for the resources available in each estuary that authorities could use to effectively address nutrient loadings.
State laws and regulations, the availability of monitoring data, and the number of wetlands in the estuary were among the factors considered.
The greater the available resources, the higher the estuary's adaptive capacity score.
"One of the key takeaways from this work is that land use plays a significant role in nutrient loads, possibly larger than many people would expect when compared to climate change," Montefiore said.
State and regional officials have limited influence over climate change, but they do have control over land-use decisions.
As a result, they will be able to help limit future nutrient loads and protect their water resources.
Nutrients are required for plant growth, but an excess of nutrients in water can have a number of negative health and environmental consequences, as per USGS.
Eutrophication occurs when there is an excess of nutrients in the water, primarily nitrogen and phosphorus.
Algae feed on the nutrients in the water, growing, spreading, and turning green.
Algae blooms can stink, block sunlight, and, in some cases, release toxins.
When the algae die, they are decomposed by bacteria-this process consumes the oxygen dissolved in the water and is needed by fish and other aquatic life to "breathe".
If enough oxygen is removed, the water can become hypoxic, where there is not enough oxygen to sustain life, creating a "dead zone".
Eutrophication is a natural process caused by nutrient accumulation in lakes or other bodies of water.
Nutrient-feeding algae form unsightly scum on the water's surface, reducing the recreational value and clogging water-intake pipes.
Decaying mats of dead algae can cause foul tastes and odors in the water; bacteria consume dissolved oxygen from the water, causing fish kills in some cases.
Eutrophication can be accelerated by increasing the rate at which nutrients enter the water.
Algal growth is typically limited by the available supply of either phosphate or nitrate, and a water body is said to be nitrogen limited if the ratio of nitrogen species to phosphorus species (N:P) is low, or phosphorus limited if the N:P is high.
Many different types of algae can cause harmful algal blooms (HABs) in freshwater ecosystems, and they can be triggered by nutrient enrichment.
The most common and severe blooms are typically caused by cyanobacteria, the only known freshwater algae capable of producing toxins dangerous to human health.
CyanoHABs have the potential to endanger both human and aquatic ecosystem health.
Economic costs associated with cyanoHABs include lost recreational revenue, lower property values, and higher drinking-water treatment costs.
