They look like the fish eggs that top sushi or tapioca in bubble tea, but these jelly orbs are not a new culinary discovery.
They’re jelly-covered plankton, and they’re turning some Ontario lakes into a slimy, squishy mess.
According to a new study in the journal Proceedings of the Royal Society B., this species of freshwater plankton, called Holopedium, has more than doubled between the mid-1980s and the mid-2000s. It thrives in low-calcium lakes, and calcium levels have been plunging over the past decade due to acid rain and logging.
Since Holopediums don’t need calcium to survive, their population has been booming. But the low-levels have affected another crustacean, the Daphnia, who rely on the calcium for nutrients to survive and reproduce, throwing off the balance even more.
So why does it matter if the jelly-plankton population is rapidly increasing?
Firstly, as the Holopedium overtake the Daphnia in numbers, the many small fish and invertebrate that relied on the Daphnia as a major food source will be in trouble. Even worse, they cannot eat the Holopedium, whose jelly coats protect them from predators. Meanwhile, some predators simply don’t have mouths big enough to eat the large plankton, either. And researchers also worry that this will mean nutrients will not be passed up the fish food chain.
Secondly, in other lakes across the country where jellification has occurred, the Holopediums have clogged up water filtration pipes. About a fifth of drinking water in Ontario comes from low-calcium lakes.
These low calcium levels are partly due to acid rain caused by industrial pollution, and partly from logging, which prevents trees from releasing calcium back into the soil, which eventually makes its way into the lakes.
“The good news is that we are able to identify one of the effects of reduced lakewater calcium levels,” John Smol, a Queen’s University biologist who co-authored the new paper, told the Ottawa Citizen. “The bad news is that many lakes have passed critical thresholds, and we have been reduced to the role of spectator as these changes continue to unfold.”
“Once again we see that there are many unexpected consequences of our actions—and they are mostly negative.”
In other words, don’t be alarmed if the next time you take a dip in the lake, you feel more slime than just some stray algae tickling your leg.