O impacto da remoção de peixes sobre a dinâmica e estrutura dos grupos funcionais fitoplanctônicos em um lago raso tropical durante uma seca severa
The artifi cial eutrophication is one of the biggest t h reat for the quality of aquatic ecosystems in the whole world. The expectations for the future climatic scenarios in arid and semi - arid regions are intense and frequent droughts enhancing the risk...
Na minha lista:
| Autor principal: | |
|---|---|
| Outros Autores: | |
| Formato: | Dissertação |
| Idioma: | por |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
|
| Assuntos: | |
| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/20250 |
| Tags: |
Adicionar Tag
Sem tags, seja o primeiro a adicionar uma tag!
|
| Resumo: | The artifi
cial eutrophication is one of the biggest t
h
reat for the quality of aquatic
ecosystems in the whole world. The expectations for the future climatic scenarios in arid
and semi
-
arid regions are intense and frequent droughts enhancing the risk of
eutrophicati
on and cyanobacterial blooms.
Restoration techniques of eutrophic lakes
were proposed to reduce nutrient loading and improve the water quality. A
successful
technique used
in temperate regions
is the biomanipulation
by
benthivorous
fish
removal
. Our hypoth
esis is that the benthivorous fish
removal reduces
phytoplankton
total biomass and change the composition of phytoplankton functional groups,
improving water quality. The aim of the study was evaluate the impact of
biomanipulation on phytoplankton function
al groups and in the water quality.
We
applied the technique of biomanipulation in the artificial lake ESEC, in a semi
-
arid
region of Brazil and analyzed the physical and chemical variables and the dynamic of
phytoplankton functional groups monthly during
November 2012 to August 2013. With
the removal of benthivorous fish we observed a significant increase of the euphotic
depth, phytoplankton richness and the recruitment of green algae (groups
F
and
J
),
indicators of good water quality.
However, we did not
observe significant differences
on total phosphorous concentration and on phytoplankton biomass and diversity. The
drought effect in the region during the study was evident
,
promoting a drastic reduction
on water level which influenced the availability of
resource and affected phytoplankton
community before the biomanipulation.
To evaluate the effect of severe drought on the
dynamic of phytoplankton functional groups and test if the drought periods are
favorable to dominance of cyanobacterial groups, we
stu
died two
artificial
neighbors
lakes (ESEC and Pocinhos) in a semi
-
arid tropical region during
May
2012 to February
2013. We observed a temporal differentiation of biotic and abiotic variables caused by
drought.
Both lakes presented reduction of 2 meters of
water level and increase on
conductivity, turbidity, nutrients concentration and a reduction on water transparency,
during the severe drought.
The
deeper
lake (Pocinhos) increased phytoplankton total
biomass and presented cyanobacterial functional group d
ominance (group
S
N
) and the
shallower lake (ESEC) reduced phytoplankton total biomass and presented dominance
of mixotrophic and flagellate functional groups (groups
W
1
e
W
2
).
Summarizing, the
knowledge of the effects of benthivorous fish removal in semi
-
a
rid tropical
lakes
still
unknown and this study had limitations caused by the impact of drought. Thus, it is necessary a long term monitoring to investigate the real effects of biomanipulation on
the functioning of the studied ecosystems. Otherwise, period
s of drought could have
opposite effects (increase or reduction) on total biomass and composition of
phytoplankton functional groups.
Drought not always leads to dominance of
cyanobacterial groups. |
|---|