Global warming and water pollution may soon cause a change in diet patterns, especially for fish lovers. According to a recent study, scientists
have recorded instances of massive outbreaks of Noctiluca scintillans during winter which is thought to reduce fish catch. The study says these micro organism blooms disrupt the traditional food chain leading to the detriment of regional fisheries, affecting the long-term health of the ecosystem that has sustained the coastal population. Biogeochemist of Goan origin Helga do Rosario Gomes, who was part of the study recently published in the scientific journal Nature Communications, told Herald Review, “The situation doesn’t bode well for the fisheries of the Arabian Sea.” The organism’s ability to thrive in pollution rich, low oxygen level water condition, only adds to the grim picture scientists are forecasting for the future of the fish catch. Oman was the first to witness this scientifically worrying trend that may soon be making its way to the Indian coast. In 2013, fish catch in Oman fell by 13 per cent, compared with the previous year. Omani fishermen also complained that they sighted more gelatinous salp, jellyfish and sea turtles , most of which are not consumed by locals. Scientists at Columbia University’s Lamnot-Doherty Earth Observatory say the presence of Noctiluca scintillans accounts for the 13 per cent fall and the occurrence began in early 2000. “We think that Noctiluca blooms may have come from the Gulf of Oman, where it has been in thick blooms for a while now. We hypothesize that currents and eddies brought Noctiluca to the Arabian Sea, where they encountered low oxygen waters. Noctiluca does well in
these waters, unlike other phytoplankton,” Gomes says. But what is the cause for these low oxygen water? The influx of untreated sewage from mega cities along the coast is known to be low in oxygen and high in organic matter. Excessive use of fertilizers that gets washed in to the sea is
another reason. Studying NASA’s satellite images,
Gomes and her team were able to confirm these blooms with the rich
emerald green water that has replaced the blues.
“Using these satellite images, I will
now be studying how human activities
in coastal mega cities are changing the
biodiversity of the Arabian Sea and the
repercussions it will have on the food
chain.”
Starting in 2009, Gomes along with
her fellow researchers from the university
sailed aboard the Indian research ship
Sagar Sampada collecting samples of
the Noctiluca blooms off the coast of
Goa.
Putting Noctiluca and its diatom competitors
in oxygen starved water, they
found that Noctiluca’s carbon-fixation
rate rose by up to 300 per cent while
the diatoms fell by nearly as much. They
also found the organism grew faster in
light than the dark.
But the biogeochemist believes disaster
management is possible even at this
point.
“One is by preventing further expansion
of the already large oxygen minimum
zone, which means reducing the discharge
of untreated sewage into the
sea, monitoring the amount of excessive
fertilizer that gets washed into the sea,
as well as educating the people about
global warming, the dangers of a large
hypoxic (low oxygen) zone, and pushing
the required agencies to set new policies,”
Gomes said.
The food chain under water usually
begins with micro organisms called
the diatoms which is then consumed
by zooplanktons, crustaceans, small
fish and finally the bigger fish. Noctiluca,
on the other hand feeds on
the diatoms leaving the zooplanktons
with no food thereby disturbing the
food chain.
Studies have shown that this organism,
however, is not a preferred food for
zooplanktons and crustaceans but are
mostly consumed by jelly fish and salps.
Smaller and predatory fishes, the kind
that are usually consumed by humans
in turn tend to stay away from these gelatinous
organisms.
