In
situ nutrient-spiking bioassays for determining phosphorus and
light
limitation in a wetland ecosystem
Woon-Ki
Moon, Ji-Woong Choi, Sang-Jae Lee and Kwang-Guk An*
Department of
Biological Sciences, College of Biological Sciences and Biotechnology,
Chungnam National University, Daejeon - 305 764, Korea
*Corresponding
Author E-mail: kgan@cnu.ac.kr
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Key
words
Algal growth,
Nutrient spiking bioassay,
Phosphorus-limitation,
Suspended solids,
Wetland ecosystem
Publication Data
Paper
received : 23.11.2015
Revised
received : 15.03.2016
Re-revised
received : 10.10.2016
Accepted : 09.11.2016
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Abstract
Aim: The objective of
the present study was to determine the factors that regulate the response of
algal growth in wetland ecosystem by in situ nutrient-spiking
bioassays (NSBs).
Methodology:
The
NSBs tested algal responses as a ratio of final (Chlf) to initial Chl (Chli)
in the control (no nutrient addition) and several treatments of phosphorus
(P), nitrogen (NH4-N, NO3-N), and NO3-N+P
under various environmental conditions of inorganic suspended solids (ISS)
and free-floating plants (FfP).
Results:
Experiments
of in situ NSBs with low inorganic solids showed that the response of P
treatments were significantly (p< 0.05) greater than the controls and the
treatments of NH4-N or NO3-N. Regression analysis of
Chlf : Chli ratios against log10-transformed TP in the
cubitainers, thus showed that in situ algal response in P treatments was
directly determined (R2 = 0.965, F = 40.049, p< 0.001) by
concentrations of spiked TP. In contrast, the in situ NSBs with high ISS
(> 15 mg l-1) or high FfP cover (> 95%) showed
that the response in treatments of N, P or P+NO3-N had no
significant (p> 0.05) difference with the controls.
Interpretation:
Light
limitation dominated the system, thus the ratio of Chlf : Chli had
no relation (p> 0.10) with the spiked TP. Overall, the experiments of in
situ NSBs suggest that high P-inputs from the watershed increased algal
growth, but dense FfP or high inorganic solids suppressed
eutrophication in the wetland.
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