Scientists explain the mysterious behavior of midges

By KENNETH CHANG

Myvatn, translated from Irish into English, means Mosquito Lake.

According to baseball fans, the mosquitoes originated from Chamberlain. They flew out of Lake Erie last October when the eighth in the first match decided between Cleveland and Yakee baseball teams. Mosquitoes have caused Yakee's team to throw two balls, the Cleveland team has scored in the run without having to catch the ball. The Yankee team eventually lost the match and a series of matches after that.

During mating season, the space around Lake Myvatn is suffocated by male mosquitoes. They hovered, waiting for their children to come. Professor Anthony R. Ives of the University of Wisconsin said: 'The sky is like a thick brown cloud covering the lake'.

But there are years when mating season, this lake almost does not see a figure of a mosquito. The exploding cycle of the number and density of the zebrafish has attracted the attention of ecologists like Dr. Ives.

On the issue of Nature , Dr. Ives and his colleagues wrote the variation in the number of mosquitoes that depend primarily on a hard-shelled algae known as diatoms, which is the main food source of mosquito. This complex dynamics can be expressed in an equation.

The equation shows the fragility of nature: a seemingly small, harmless act can also affect the ecosystem, leading to unforeseen troubles.

Ecologists have long studied mathematical models to understand the dynamics of different animals. A simple example is the predator model - prey between foxes and rabbits. When the number of rabbits increases, the fox will have excess food and also proliferate. But when foxes eat too many rabbits, the source of food runs out and it will starve.

Male mosquitoes are waiting to mate with female mosquitoes around the shore of Myvatn lake.This is a place where no Yankee team baseball player wants to take a break: Ho Myvatn in Ireland.(Photo: Ami Einarsson)

Similarly, the number of mosquitoes exploded when the diatoms became rare . The mosquito larvae lie behind in the sediment layer and eat diatoms floating through it. When mosquito larvae are present in every corner, diatoms will no longer develop. According to Dr. Ives, 'Basically, the mosquito herd has taken away its habitat'. Diatoms can grow in areas of rocky soil in lakes where mosquito larvae cannot hide. After the number of mosquitoes is reduced, diatoms will return to the area with less mosquito and another cycle will occur.

There was also a time when the number of mosquitoes was stable during the year before an explosion cycle took place. Arni Einarsson and Arnthor Gardarsson - two collaborators of Dr. Ives - collected data on the number of adult mosquitoes in Lake Myvatn since 1977. The fourth author of the Nature paper is Vincent AA Jasen of the great study London.

Alan Hastings, professor of environmental science and policy at the University of California - Davis, though not involved in the study, but also comments: 'the article has shown a great step forward in understanding. relationship ' between an observable mathematical model and ecosystem.

The equation shows that both types of dynamics - stable population and explosion cycle - are stable and will continue without interruption. But natural systems encounter obstacles that come from nature, such as an unusually hot summer, and also human obstacles.

In the case of Myvatn Lake, in 1967 there was a dredging of the lake to exploit diatomite - a chalky white stone made up of diatom shells used for filtering beer or for other purposes. Nearly two decades later, the amount of fish in the lake, which is a source of food for the people of the millennium, is also exhausted.

Dr. Ives said: 'We still think they are connected, but we have not yet found that connection.'

A Myvatn Lake (Photo: Ami Einarsson)

The new study suggests that diatoms could be trapped in low-lying areas, so they could not drift down to the shallower areas, so the number of midges also recovered longer after being reduced. When the mosquitoes become sparse, the fish are also hungry, causing the number of fish to decrease.

The mathematical model does not prove this relationship, ' but at least it shows its ability ', according to Dr. Ives. The dredging of diatomite has been discontinued since 2004 but the fish has not returned to Myvatn Lake. It is possible that life in Lake Myvatn has stabilized with a few new motivations and the amount of fish in the lake will never become redundant again. Dr Hastings said: 'Ecosystems are very complex. These mathematical models can help biologists infer change agents. And it also reminds us to be always cautious. '

That's why Yakee baseball team should think carefully before deciding to dredge Lake Erie to improve their chances of winning world tournaments.