From Sea To Space: Turning The Tide On Microplastic Pollution

A Texas A&M University at Galveston researcher is pioneering a groundbreaking approach to monitor and combat ocean pollution using satellite technology.

What do microplastics, water color, and satellites have in common? Dr. Karl Kaiser, professor of marine and coastal environmental science in the College of Marine Sciences and Maritime Studies at Texas A&M University at Galveston is exploring an innovative idea: using satellites to spot microplastics in the ocean. How? By studying how tiny plastic particles change the way light reflects off the water — and how that changes the color we see from space. If this connection works, it could give scientists a powerful new tool to track microplastic pollution across the globe without ever leaving orbit.

Microplastics are small pieces of debris that shed from larger pieces of manufactured plastic due to chemicals or natural weathering. The minuscule size of microplastics also means they can build up in the tissue of living organisms, are easily ingested, and are distributed across vast distances via water currents.

“With microplastics, you’re in a size range that’s similar to bacteria and red blood cells; they appear to have very different characteristics than larger plastic pieces,” Kaiser said. “Their size makes them extremely difficult to filter and measure, especially in a dynamic ocean environment.”

Galveston Bay holds the highest concentration of microplastics in the United States. Why? It’s home to one of the largest plastic manufacturing hubs in the country — and the impact is visible in the water.

This issue is especially important for Kaiser, who conducts research in the bay. He examines how the higher sediment count in surface water correlates to higher microplastic concentration. From there, the suspended sediment determines what light is reflected by surface water, which is measured using spectroscopy.

Spectroscopy quantitatively measures how matter interacts with light; by identifying which specific wavelengths are absorbed or reflected, scientists can determine the composition of water-suspended sediments on a large scale. While spectroscopy is famously used to determine the makeup of distant stars and planets, Dr. Kaiser has high hopes for its applications thanks to a new generation of optical sensors in satellite imagery.

“Optical properties of surface water are shaped by what’s in the water. That determines how much light, provided from sunlight, is reflected — and that’s what satellite imagery measures,” he explained. “The reflected light is basically indicative of ingredients in the water.”

The task of matching missing wavelengths of light to what’s present in surface water will be done by an algorithm meticulously trained by Kaiser himself.

“The algorithm that will tie remote ocean color reflectance data to what’s in the water — or a specific ingredient in the water — has to be calibrated first,” he said. “You must measure incoming and outgoing light, and you must measure the sediment concentration in the water at that time. That is the primary connection.”

Kaiser is confident that there is a relationship between suspended sediment and microplastics. Where other sediment is being carried by ocean currents, microplastics should track as well. Once that relationship is rigorously tested, it will be possible to determine microplastic concentration through indirect correlation with surface water properties seen in satellite imagery, all calculated by Kaiser’s trained algorithm.

“The tools already exist to identify suspended sediment load from satellite data,” he explained. “They just haven’t been used for it yet.”

The ability to measure microplastics via satellite imagery would instantly unlock libraries of valuable data archived in satellite photo records, including microplastic migration in hundreds of photos taken over 10 years.

“The cool thing would be that we could go back through time to learn a lot about pollution loads very quickly,” he said. “We could use it as a forecasting tool to inform aquaculturists where to put their ponds and cages to avoid contamination.”

According to Kaiser, measuring microplastics is only the beginning. “If everything works out, we could then measure microplastics, forever chemicals, MPAs, and PCBs.”

If successful, Kaiser and his research partners plan to present the pollution data found through satellite imagery to state and federal agencies to bring more attention to how widespread microplastics are and to strengthen legislation that helps solve the problem.