Marylanders are all too familiar with the problems associated with algae blooms in the Chesapeake Bay, but those blooms are nothing compared to the massive green carpet of algae in the Yellow Sea, near the town of Qingdao, just off the coast of China.
Biologists are still unsure about what causes the algae bloom just south of the Shandong Province, which grows to an estimated million tons of biomass each year, the New York Times reports.
A red tide bloom off Florida. Blooms of Karenia brevis algae become more toxic when access to phosphorus is limited. (photo: Florida Fish & Wildlife Research Institute)
Since algae aren’t dangerous for humans, many beachgoers play in it, tossing it over their heads like a swimming pool toy. Algae blooms are dangerous for marine life, though: They prevent the sun’s energy from reaching most submerged aquatic vegetation, which then can’t produce food through the process of photosynthesis. If food production in plants decreases, there’s less food for sea creatures who eat the plants, and then there are fewer of those animals around for ocean carnivores. You get the idea.
Furthermore, due to the emission of hydrogen sulfide gas when they decompose, algae blooms also smell like rotten eggs. That causes a predictable drop in tourism, and towns whose local economies depend on tourists’ money aren’t a big fan of algae blooms.
In the Chesapeake Bay, algae blooms are usually attributed to fertilizer runoff, which increases the level of nutrients like phosphorus and nitrogen for certain phytoplankton or cyanobacteria species. Although runoff from farms is a factor in China, that pollution has been running off into the Yellow Sea for decades, so scientists are looking for another trigger to account for the recent upsurge in the size of the blooms.
What may be happening, scientists like John Keesing from the Csiro Division of Marine and Atmospheric Research in Australia believe, is that rafts traveling south of Qingdao to harvest porphyra, known as nori in Japanese cuisine, pick up algae on the bottom of the rafts. When the rafts come back to be cleaned, the algae cells, of the species Ulva prolifera, get washed into the Yellow Sea, where a nutrient-rich environment awaits them.