June 17, 2019– Mary Greeley News – Nicknamed “blue tears” or “sea sparkles,” blooms of red Noctiluca scintillans are a huge draw for tourists, but these blooms could be causing irreparable damage to the coastal marine and river ecosystems where they flourish.
On summer nights, the waters surrounding Taiwan’s Matsu Islands cast an eerie blue glow. The phenomenon, known as China’s “blue tears,” is actually caused by a bloom of tiny, bioluminescent creatures called dinoflagellates. Tourists from all over China come to view the twinkling seascape.
But, the bloom in the East China Sea may be beautiful, but it’s also toxic. And it’s growing bigger every year, a recent study finds.
Like algal blooms, when nutrient levels are high enough to support expansive blooms, it can choke out other marine life by lowering oxygen levels in the water.
The glowing waters around the East China Sea are caused by blooms of plankton called red Noctiluca scintillans, and satellite imagery shows that the blooms are spreading farther and wider than in previous years.
Fluorescent blue sparkles, dubbed “blue tears,” that glow around Taiwan’s offshore Matsu Islands are not caused by toxic algae and a sign of environmental deterioration, a Taiwanese researcher said Sunday in rebutting a recent study.
Chiang Kuo-ping (蔣國平), a distinguished professor at National Taiwan Ocean University (NTOU), said it cannot be established that the “blue tears” along beaches near Matsu are associated with toxic algae because they do not drain oxygen from the surrounding waters and kill marine life in the process as stated in the study.
He said the single-celled “noctiluca scintillans,” also known as “dinoflagellates” or sea sparkles, that generate the bioluminescence described as “blue tears” when disturbed are non-toxic heterotrophs — organisms that feed on other sources of nutrition to survive.
In coastal ecosystems, they replace copepods — small crustaceans commonly found in aquatic communities — as the main consumers of phytoplankton and play the role of a “terminator” of single-cell algae called diatoms, which Chiang described as a normal phenomenon in marine ecosystems.
The toxic algae argument does not hold water along the Matsu coastline because the sea sparkles have not caused the algae to starve the water of oxygen or led to the death of marine life, he contended.
Chiang also noted that the American study in the journal Geophysical Research Letters was conducted by people with expertise in studying satellite data and images rather than ecological experts.
The study by Chuanmin Hu, a professor of optical oceanography at the University of South Florida, that the Taiwanese professor was responding to was reported in local media.
It argued that bioluminescent sea sparkles have become more abundant in recent years based on satellite images that have tracked their movements.
The study observed that from 2000 to 2003 when the Three Gorges Dam was being built on the Yangtze River and there was little water flow, there was only a small distribution of the “blue tears.”
But since construction has been completed and the water flow was restored to normal, the “blue tears” have steadily expanded.
While the reason for that cannot be determined for certain at present, it is likely related to the major release of pollution and agricultural runoff of nutrients from the
Yangtze River into the East China Sea, the study argued.
Hu and his team of researchers used satellite data to track the size of the bloom over time. By analyzing nearly 1,000 satellite images from the past 19 years, the researchers were able to identify a signature unique to blue tears — the wavelengths of light reflected by this particular creature, but not others. “It’s like a fingerprint,” Hu said. Using this fingerprint, they found that the bloom, which is typically seen near shore, is extending its reach into deeper waters.
That’s a problem for marine creatures.
The blue tears phenomenon can poison sea life, from fish to sea turtles. The bloom can even make humans sick, Hu said. The dinoflagellates actually aren’t toxic themselves — until they begin chowing down, he said. Toxic algae is their food of choice, and as they eat, they release ammonia and other chemicals that poison the water around them. Not only that, but these creatures breathe oxygen until there’s none left in the surrounding waters.
“The oxygen in the water is so low that many animals can die,” Hu said.
The cause of blue tears isn’t certain, but Hu and his colleagues think pollution from agriculture that funnels down the Yangtze River plays a major role. The river dumps fertilizer into the East China Sea, giving blue tears massive doses of the nutrients it needs to grow.
Hu and his colleagues noticed that the size of the bloom was particularly low during the construction of the controversial Three Gorges Dam, between 2000 to 2003. It so happens that during those years, the Yangtze River’s flow had decreased markedly. In 2003, when dam construction was complete and the Yangtze River began to flow more strongly again, Hu saw the bloom begin to grow once more.
Hu and his colleagues don’t expect the bloom to stop growing anytime soon. That means it will continue to pose a threat to marine life. And the waters will glow more brilliantly.
credit: In part with https://www.earth.com/news/toxic-blue-tears-blooms-china/