scienceStechnology
Tuesday, February
Page 6
THE BATTALION
, Kebruarv I
A new angle for lake management
Scientists examine role of fatty acids in health of aquatic ecosystems
BY YOLANDA LUKASZEWSKI
The Battalion
Nutritional fads come and go, but one fatty
acid that scientists find beneficial in human diets
could also prove essential to the health of lake
ecosystems.
Plankton, tiny plants and animals, form the ba
sis of food chains in lakes, and fisheries managers
know that their health translates into the overall
health of the ecosystem.
Fisheries managers trying to create ideal con
ditions for fish populations traditionally focused on
the effects of nutrients, such as nitrogen and phos
phorous compounds, on plankton communities.
These nutrients can have a rippling effect
through each trophic level, or rung, of the food
chain, ultimately determining which species of
zooplankton are available for fish to eat.
But some researchers are now saying that di-
QatolM]
i
Fish populations
depend on
healthy
supplies of
zooplankton
t
t
The zooplankton
Duphnia is one
of the main
consumers of algae
in lakes. Increasing
their population
allows greater
control of algae
blooms and provide*
more food for fish populations
Herbivorous zooplankton
consume phytoplankton.
niiitoms, common |>li\to|)l:inltloii
in lake ecosystems, are integral
components of the hike ecosystem's
food chain. They arc higher in food
quality than other common plankton
species, such as cyanobacteria.
Phytoplankton use solar energy
to transform dissolved nutrients into food.
ROBERT HYNECEK/ ITti Battalion
Fisheries scientists showed that diatoms, with high concentrations of one kind of fatty acid,
are a more efficient food resource than other common phytoplankton.
etary factors are also important considerations for
healthy lake ecosystems.
Scientists should stop looking at just total ni
trogen and phosphorous. Dr. Daniel Roelke, as
sistant professor of Wildlife and Fisheries Sci
ences, said.
“We should start looking at specific com
pounds and how they are controlling, or at least
influencing, other trophic levels in terms of their
reproductive growth and success.”
A group of aquatic scientists at the
University of Califomia-Davis and the
University of Washington are taking this
different approach.
They found that zooplankton, the tiny
animal component of plankton, thrive on
certain kinds of algae but not others.
Some kinds of phytoplankton, the mi
croscopic algae making up plankton’s plant
component, are rich in a certain fatty acid
that may he crucial to zooplankton growth.
In laboratory experiments, the re
searchers fed two types of phytoplankton,
cyanobacteria and diatoms, to the zoo
plankton Daphnia.
They found that in summer, when the
cyanobacteria dominated the lake, only 5
to 26 percent of the phytoplankton eaten
by the Daphnia was converted to zoo
plankton biomass.
During spring and winter, when di
atoms dominated the lake, 50 to 65 per
cent of the phytoplankton Daphnia ate
was converted to zooplankton biomass.
Cyanobacteria is poor in eicosapen-
taneoic acid, commonly known as
omega-3 fatty acid, while diatoms are
rich in omega-3 fatty acid.
The Daphnia that consumed phyto
plankton high in omega-3 fatty acid had
higher egg production and growth rates,
leading the researchers to conclude that
the omega-3 fatty acid in diatoms made
them more nutritious than cyanobacteria.
This might explain the difference in growth.
Omega-3 fatty acids keep cell membranes
healthy and help form important hormones in an
imals, Dr. Michael T. Brett, University of Wash
ington assistant professor of Civil and Environ
mental Engineering, said.
Brett co-authored the study, published last
month in the journal Nature.
“Eicosapentaneoie aeid is the same dietars tat
ty acid that is thought to be the health) compo
nent of fat-rich fish like salmon and tuna in hu
man diets," Brett said.
“Phytoplankton that are more nutritious can
have a major impact on the overall food web.”
Brett said.
“What the study shows is that the rate at
which zooplankton convert phytoplankton to
biomass depends on the supply of this class of
essential fatty acids. This gives us important in
sights into what may determine how cncrgv
moves through aquatic food webs," he said.
Scientists have known for some time that
zooplankton do not grow well on evanobaete-
ria, but they did not know exactlv why. Roelke
said.
This study is unique, he said, because the re
searchers chose to look at a fatty acid to explain
why zooplankton do not grow as well on
cyanobacteria as they do on diatoms.
However, algae living in nutrient poor env i-
ronments will not be as nutritious as algae grow -
ing in healthy conditions, regardless of the
species or abundance, he said.
Roelke said the study did not address how
food quality varies depending on the physio
logical state of the algae.
Nevertheless, studying the role that omega-
3 fatty aeid plavs in aquatic food chains could
have important implications for lake restoration
and fisheries management.
Based on the results of the study, fisheries
managers might want to create an env ironment
that favors nutritious algal species over poor
food quality algae.
M?
FDA approves 1 a
new digital Ags’f
mammogram break
world
BY JASC
The
M
ost athli
want, c<
their eh
\\ \SI 11 N( iTON (AP) - Hk nation
digital mammograms computenzedbit
\-ra> s to hunt breast cancer — wereappp
b\ the government Monday.
1 )igital mammograms appear as goodc
hut not better than regular mammojtTaa
detecting breast cancer, the h*xl and Dray
ministration cautioned vanes trom pciso
But the new digital niuminograph)stories to national
chine, til Medical Inc s SenographcMj Texas AAA
di>csolVcr potential advantages to rceukTHckvard is no i
Y-n»ys: Howard is strixii
I )igilal tnamnv'ciams can he stonx. limited bv a singk
tromcall) so films are not lost, adjustedimdoCs not want to I
rler-or o\erevposure withoutneetfiogiH "I \cr\boil\ M
\ rav, .md sent electronicallv tosfxx. ones that hate to
worldwide toi consultation. next lc\cl." \A
Mettct. it is ,i Ion. -awaited first xtef :.coach Mel Nash
me computers m even more sophifta.lost and that is hi
ect breast cancer.DlDte I hat attitinf
of breast imaging fi work well in a
leral Hospital, who haste more to traimm
tern. said. rather than eom|
II open a new era inim® each competitioi
etion ot breast canccr,"ktt Nc\cithclcss.
list ol research that digits.c. swim each race I
ihlc to move lorward.‘•Th5!‘i in the adjacent lai
1 I’ve got mv lingerserwe I he dctcrmina
ire going to pan ouL Tlaipn X-lactor. th.
ipporiunity ' to tr\ through three sea-
\ mciK.in women undergo s* uric JO# now making its
unogramseven vear. world ciicuit.
!lie breast Vra\ is die cold standith: lodas. the ser
^ta^^n;p*ticularlvevHte F,N VSum " nm -
ms are not loolpr* Sheffield. I nglan
toped that compote his college talents
d improve the Wfc mere m the l ump
ved essentially a fe resenting the I X
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England. I low ai d
World C up on he
mans.
“It w ill he gooc
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lusettt
udv th
“Th
better d
direct*
Gener
th
ast i
man
But
mammograms coi
The FDA approv ed ei
in digital mtuumographv. cautioned rat
ic dev ices chid Dr. Dan Schultz.
-x—7~
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