Analysis of long-term variation in phytoplankton biovolume in the northern basin of Lake Biwa

Kishimoto, Naoyuki; Ichise, Satoshi; Suzuki, Kei; Yamamoto, Chihiro

doi:10.1007/s10201-012-0390-8

Cited by 20 publications

(11 citation statements)

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“…In the northern basin of Lake Biwa, a decrease in net phytoplankton (≥ 4,000 µm 3 /cell) and an increase in small nanophytoplankton (S-nanophytoplankton, < 100 µm 3 /cell) was observed (Kishimoto et al, 2013). As a result, the average cell volume was shifted from 269 µm 3 /cell in 1980s to 56 µm 3 /cell in 2000s (Kishimoto et al, 2013). Figure.…”

Section: Factors Changing Areal Net Primary Productionmentioning

confidence: 96%

“…These changes indicate a decrease in phytoplankton biomass in the northern basin of Lake Biwa. Actually, the decrease in total phytoplankton biovolume in Lake Biwa was also reported (Kishimoto et al, 2013). Therefore, it seems to be natural that primary productivity in the northern basin of Lake Biwa tends to decrease after 1981.…”

Section: Introductionmentioning

confidence: 98%

“…8 shows the changes in the annual mean of areal net primary production fractioned by cell size. The cell size information was quoted from the electronic supplementary material of Kishimoto et al (2013). Figure 8 clearly demonstrates that the most part of the increase in net primary production was caused by the S-nanophytoplankton, whereas its biovolume at Imazuokichuo point was about one order smaller than that of the net phytoplankton even in recent years (Kishimoto et al, 2013).…”

Section: Factors Changing Areal Net Primary Productionmentioning

confidence: 99%

“…The data contained population densities of 200 phytoplankton species at the depth of 0.5 and 5 m (see the electronic supplementary material of Kishimoto et al (2013) for the full species list). The observation frequency was basically twice a month.…”

Section: Estimation Of Primary Productivity Data For Evaluationmentioning

confidence: 99%

“…Therefore, it seems to be natural that primary productivity in the northern basin of Lake Biwa tends to decrease after 1981. However, the shift of predominant phytoplankton species to smaller ones was observed in the lake along with oligotrophication and lake warming (Kishimoto et al, 2013). It is known that the metabolic rate of organisms is proportional to the body size to the power of 0.75 (Kleiber, 1947).…”

Section: Introductionmentioning

confidence: 99%

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Does a Decrease in Chlorophyll <I>a</I> Concentration in Lake Biwa Mean a Decrease in Primary Productivity by Phytoplankton?

Kishimoto

Yamamoto

Suzuki³

et al. 2015

J. of Wat. & Envir. Tech.

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Lake Biwa had eutrophicated till the 70s, but total phosphorus and chlorophyll a concentration began to improve around 1980 due to various efforts by the government and residents. Along with the decrease in chlorophyll a concentration, Secchi depth in Lake Biwa has been improved. It is expected that the decline in chlorophyll a concentration decrease primary productivity by phytoplankton. However, the phytoplankton community in Lake Biwa has also been changed along with the oligotrophication. Therefore, the response of the productivity against the change in chlorophyll a concentration may not be linear. In this research, areal primary productivity in the northern basin of Lake Biwa was estimated using phytoplankton census data and environmental data collected by Lake Biwa Environmental Research Institute from 1980 to 2008. Surprisingly, the estimated areal productivity tended to increase over time, whereas chlorophyll a showed a reverse trend. Two influential factors were deduced: the one was the expansion of euphotic zone with the improvement of Secchi depth and the other was the shift of phytoplankton to smaller species, which had higher productivity than larger ones. The latter had a stronger effect than the former. Thus, a change in phytoplankton community should be considered for the accurate evaluation of productivity.

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Section: Factors Changing Areal Net Primary Productionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 98%