Water dynamics play a pivotal role in fish biodiversity

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Washington, May 8 : A new method developed by researchers from Princeton University has shown that water dynamics play a pivotal role in the biodiversity of fishes in river networks.

The researchers have created a computer simulation that allows them to predict, based on rainfall measurements and the structure of river networks, how many species of fish will occupy any given region.

According to Ignacio Rodriguez-Iturbe, senior author of the study, the new method turns simple data about rainfall and river networks into accurate assessments of fish biodiversity, allowing better prediction of the effects of climate change and the ecological impact of man-made structures like dams.

The mathematics behind the new method also can be used to model and predict a wide range of other questions, from the transmission of waterborne illnesses to vegetation patterns on land adjacent to rivers.

"It is an extremely simple model but it predicts absolutely fantastically well all of the characteristics of biodiversity that we were interested in," said Rodriguez-Iturbe. "Our model implies that water dynamics have a commanding effect on biodiversity in river basins," he added.

In their research, the authors merged different sets of existing data from the Mississippi-Missouri river basin, an extremely large region that covers more than half of the United States.

This network of rivers springs from the Mississippi River, which cuts down the middle of the country. The triangle-shaped basin stretches from Minnesota to Louisiana and from Montana to New York.

Using one set of data, the researchers were able to identify 824 distinct sub-basins and establish how the rivers within each sub-basin were linked together. Another set of data identified 433 different species of fish living in those sub-basins.

A third set of data identified each region's average runoff, which is the amount of rainfall that ends up in rivers or streams as opposed to water that is soaked up by the ground.

The researchers combined all these data and came up with a computer model that accurately predicts how many different species of fish will inhabit any given sector of the river basin.

Their research shows that the habitats richest in the diversity of species are areas where multiple streams are close to one another.

"This will help identify which parts of a river basin are 'hot spots,' meaning they have more species than others and therefore should receive special care," said Rodriguez-Iturbe.

River networks act as ecological corridors and as such the model will be useful not just for understanding the biodiversity of fish in rivers but also for understanding such things as the dispersal of seeds or even the spread of cholera.

ANI

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