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12 HEALTH AND LABORATORY MAGAZINE

A VICIOUS CYCLE OF OXYGEN

LOSS THREATENS WATER

QUALITY IN LAKES

Researchers recently confirmed that the
world’s lakes are rapidly losing oxygen.
What does it mean for water quality that
oxygen is declining globally?

Scientists have recently associate professor of by freshwater microbes what I originally predicted.” oxygen levels in bottom
confirmed that the world’s biological sciences at the gobbles up oxygen. waters, thus disentangling
lakes are rapidly losing Virginia Tech College of FUSING FRESHWATER the effects from those of
oxygen. With a seven-year, Science and an affiliated In a seven-year field AND DATA SCIENCE changing temperature, is
whole-ecosystem study, scientist with the Fralin Life experiment that crucial to understanding
a team of freshwater Sciences Institute. “Lakes manipulated oxygen levels Making those discoveries anoxia’s impact, said Carey,
scientists at Virginia Tech do this really great job of in the bottom waters relied on the team’s a Roger Moore and Mojdeh
has been one of the first receiving and processing of a nearby reservoir, design of an experiment Khatam-Moore Faculty
to take the next step all of this carbon, Carey’s team found that that was novel in a few Fellow in the College of
in asking: What does it nitrogen, and phosphorus, with anoxic conditions ways. It had to be done at Science. “By manipulating
mean for water quality preventing them from came effects they had whole-ecosystem scale, oxygen without altering
that oxygen is declining going downstream and expected: the sediments conducted not just with temperature, we can
globally? reaching the ocean.” release a lot of nutrients samples tested in a lab understand and isolate
and carbon. But they or in small enclosures of a what its effects will be. We
Sticky with sediment, But that work could be weren’t as prepared for lake’s bottom waters, but can truly say that what
the bottom waters of dismantled by anoxia, the the extent of the changes. with access to the whole we’re seeing is a result of a
lakes are more than loss of oxygen availability. They observed the lake body of water. Carey’s changing oxygen and not
their deepest, darkest Dreaded by scientists going from a sink — which team did field experiment due to other extraneous
layer. They bury massive for years and recently retains more nutrients and in the Falling Creek factors happening in the
portions of the carbon, confirmed as widespread carbon than it exports — Reservoir in Vinton, Virginia, lake.”
nitrogen, and phosphorus by data from hundreds of to a source of nutrients where team members
found in runoff rolling in lakes, anoxia is sucking downstream, starting a manipulated oxygen levels But analyzing anoxia’s
from the land. As one of oxygen from the world’s cycle in which anoxia in one in the lake’s bottom waters effects doesn’t stop at
nature’s critical nutrient fresh waters. lake could beget anoxia in using an engineered upping or lowering oxygen
sinks, lakes earn their another. oxygenation system that levels and monitoring
reputation as “sentinels” It’s a phenomenon linked could withdraw water from water chemistry. With a
of their surroundings, to the warming of waters “I had no expectation that the bottom, inject dissolved field experiment, there’s
said freshwater scientist brought on by climate there would be this much oxygen into it at super- always data you need but
Cayelan Carey. change and to excess change in water chemistry,” saturated concentrations can’t collect, Carey said.
pollutant runoff from land Carey said. “And to see it onshore, and return the It’s difficult to sample and
“We think of lakes as use. Warming waters consistently and to see it oxygenated water to the measure “those nitty-
sentinels because they diminish fresh water’s over the seven years of bottom without altering gritty sediment-water
truly integrate all of the capacity to hold oxygen, the study — the effect of water temperature. interactions” without
changes that happen while the breakdown of anoxia was multiple orders disturbing them in the field.
on land,” said Carey, an nutrients in the runoff of magnitude greater than Manipulating only the There’s also the issue of