By Roberta Attanasio, IEAM Blog Editor
The plenitude of environmental changes currently underway is leading scientists to devise new catchwords for communicating novel, unexpected findings. Think of plastiglomerates, a new type of stone made up of melted plastic and other materials that will likely become part of the rock record. Now, we have “jellification” — very recently conceived to describe the process causing goo balls to wash up on the shores of Canadian lakes.
The goo balls are made up of a small planktonic animal dubbed Holopedium glacialis, which is surrounded by a gelatinous polysaccharide bubble. Holopedium is clogging up water pipes and may potentially disrupt the food chain. An interdisciplinary team of scientists has uncovered the story behind it.
In a paper published on November 19, 2014 (The jellification of north temperate lakes), John Smol and his collaborators report that calcium levels are decreasing in lakes across eastern North America and western Europe. A consequence of decreasing calcium levels is the disappearance of Daphnia, a tiny crustacean less than 3 mm in size, more commonly known as water flea because of its swimming style.
Daphnia is a keystone grazer in lakes and ponds — in other words, it’s part of the foundation of all healthy aquatic ecosystems. It feeds on algae cells, and represents the staple food for a variety of fish species and other predators. It needs large amounts of calcium to build its body shell. In contrast, Holopedium, a competitor of Daphnia, thrives in waters depleted of calcium. Thus, in Canadian lakes, Holopedium has taken over the room vacated by Daphnia, aided by larval midges, Daphnia’s major predator.
Indeed, according to Howard Riessen and collaborators, Daphnia is unable to defend itself in presence of low calcium levels — low levels prevent the development of Daphnia’s induced defenses against the midges. Induced defenses, such as increase in body size, formation of neck spines, and strengthening of the carapace, are those that become more pronounced in presence of predators.
In contrast, because of its jelly coat, Holopedium is relatively invulnerable to predators. Smol told CBC’s Quirks & Quarks: “Fewer things can eat these Holopedium. They’re larger, they’re covered in this jelly — some organisms simply don’t have the mouth big enough to handle them.”
Life is getting even more dangerous for Daphnia — climate change is causing oxygen decline deep in the lakes, creating better conditions for an increasing population of larval midges. And as Daphnia vanishes, Holopedium grows and multiplies by making a meal of Daphnia’s leftovers — uneaten algae.
The calcium present in lakes derives from soil and fallen trees. What is causing the low calcium levels in lakes, then? The answer is simple — a decades long legacy of industrial pollution. Andrew Tanentzap, a researcher on the Smol paper, explained in a press release that, historically, large amounts of acid were deposited throughout the northern hemisphere due to industrialization. The acid displaced calcium from soil and, over a long period, this process pushed all the calcium out of the drainage areas feeding these lakes, causing dramatic declines in the water calcium levels.
“It may take thousands of years to return to historic lake water calcium concentrations solely from natural weathering of surrounding watersheds,” said Tanentzap. “In the meanwhile, while we’ve stopped acid rain and improved the pH of many of these lakes, we cannot claim complete recovery from acidification. Instead, we may have pushed these lakes into an entirely new ecological state.”
Smol and his collaborators believe that the growth explosion of the Holopedium population will not only clog up the extraction of drinking water, but also reduce nutrient transfer through food webs because of Holopedium’s lower phosphorus content.
What can be done to fix the problem? David Schindler, an aquatic ecologist at the University of Alberta, told The Star that scientists in Scandinavia have experimented with adding lime to lakes and forest to fix their chemistry, but the process is incredibly expensive and only moderately successful. He said: “Right now we don’t know how to fix it, except to turn off emissions and wait.”