Multivariate control of heterotrophic bacterial abundance and zooplankton grazing in Labrador fjords (northeastern Canada)

2020 ◽  
Vol 84 ◽  
pp. 105-120
Author(s):  
AG Simo-Matchim ◽  
M Gosselin ◽  
C Belzile
Keyword(s):  
Growth Rate ◽  
Heterotrophic Bacteria ◽  
Abiotic Factors ◽  
Mean Value ◽  
Phytoplankton Growth ◽  
Heterotrophic Nanoflagellates ◽  
Organic Substrates ◽  
Bacterial Growth Rate ◽  
Phytoplankton Growth Rate ◽  
Substantial Control

This study was conducted in 4 Labrador fjords (Nachvak, Saglek, Okak, and Anaktalak) during the summers of 2007 and 2013, early fall 2010, and late fall 2009. Our results show that water temperature combined with the availability of nutrients and organic substrates are the main abiotic factors controlling the abundance of heterotrophic bacteria in Labrador fjords. Bacterivory also played a crucial role, with heterotrophic bacteria exerting a significant bottom-up control on the abundance of heterotrophic nanoflagellates (r = 0.35, p < 0.05) and ciliates (r = 0.70, p < 0.01). During summer 2013, the intrinsic phytoplankton growth rate varied between <0 and 0.64 d-1, with a mean value of 0.36 d-1. The herbivory rate was highly variable, ranging from 0.01 to 0.86 d-1, with a mean value of 0.31 d-1. Grazing mortality was 6-fold higher than phytoplankton growth rate. Mean phytoplankton growth and herbivory rates in Labrador fjords were comparable to the Barents and Bering seas. The intrinsic growth rate of total heterotrophic bacteria ranged between <0 and 0.68 d-1, with a mean value of 0.30 d-1. Bacterivory varied from 0.01 to 0.95 d-1, with a mean of 0.30 d-1. Mortality due to grazing was up to 2.3 times higher than total bacterial growth rate. This study improves our understanding of the factors influencing the dynamics of heterotrophic bacteria and indicates that herbivory and bacterivory exert substantial control on microbial communities in Labrador fjords.

A modeling approach to simulate impact of climate change in lake water quality: phytoplankton growth rate assessment

1998 ◽  
Vol 37 (2) ◽  
pp. 177-185 ◽  
Author(s):  
Hany Hassan ◽  
Keisuke Hanaki ◽  
Tomonori Matsuo
Keyword(s):  
Climate Change ◽  
Water Quality ◽  
Growth Rate ◽  
Dissolved Oxygen ◽  
Lake Water ◽  
Phytoplankton Growth ◽  
Quality Data ◽  
Model Parameters ◽  
Lake Water Quality ◽  
Phytoplankton Growth Rate

Global climate change induced by increased concentrations of greenhouse gases (especially CO2) is expected to include changes in precipitation, wind speed, incoming solar radiation, and air temperature. These major climate variables directly influence water quality in lakes by altering changes in flow and water temperature balance. High concentration of nutrient enrichment and expected variability of climate can lead to periodic phytoplankton blooms and an alteration of the neutral trophic balance. As a result, dissolved oxygen levels, with low concentrations, can fluctuate widely and algal productivity may reach critical levels. In this work, we will present: 1) recent results of GCMs climate scenarios downscaling project that was held at the University of Derby, UK.; 2) current/future comparative results of a new mathematical lake eutrophication model (LEM) in which output of phytoplankton growth rate and dissolved oxygen will be presented for Suwa lake in Japan as a case study. The model parameters were calibrated for the period of 1973–1983 and validated for the period of 1983–1993. Meterologic, hydrologic, and lake water quality data of 1990 were selected for the assessment analysis. Statistical relationships between seven daily meteorological time series and three airflow indices were used as a means for downscaling daily outputs of Hadley Centre Climate Model (HadCM2SUL) to the station sub-grid scale.

Phytoplankton growth rate and zooplankton grazing in the western part of the Black Sea in the autumn period

Oceanology ◽  
2009 ◽  
Vol 49 (1) ◽  
pp. 83-92 ◽  
Author(s):  
L. V. Stel’makh ◽  
I. I. Babich ◽  
S. Tugrul ◽  
S. Moncheva ◽  
K. Stefanova
Keyword(s):  
Growth Rate ◽  
Black Sea ◽  
Phytoplankton Growth ◽  
The Black Sea ◽  
Zooplankton Grazing ◽  
Autumn Period ◽  
Phytoplankton Growth Rate

An early spring bloom of large diatoms in the ice-covered Saroma-ko Lagoon, Hokkaido, Japan

2011 ◽  
Vol 92 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Akihiro Shiomoto ◽  
Koji Asakuma ◽  
Han-Dong Hoon ◽  
Koichi Sakaguchi ◽  
Kimihiko Maekawa
Keyword(s):  
Growth Rate ◽  
Global Warming ◽  
Primary Production ◽  
Spring Bloom ◽  
Early Spring ◽  
Phytoplankton Growth ◽  
Bloom Period ◽  
Ice Coverage ◽  
Phytoplankton Growth Rate ◽  
Free Area

Saroma-ko Lagoon, the largest body of water that has complete ice coverage during winter in Japan, was not completely covered by ice in the winter of 2009. This condition is considered to be a result of the progression of global warming. A bloom of large diatoms was observed in the ice-free area between February and April. This early spring bloom seemed to have started in the latter part of January, and lasted for about three months. The maximum chlorophyll-a (Chl a) concentration of about 10 mg m−3 was observed in March, and was similar to the level of 5–20 mg m−3 previously reported for the ordinary spring bloom in Saroma-ko Lagoon. The maximum primary production of 786 mgC m−2 day−1 and the maximum Chl a-specific primary production, an index of the phytoplankton growth rate, were also found in March. Species changes from Thalassiosira spp. to Chaetoceros spp. were observed during the bloom. This early spring bloom could extend into the ordinary spring bloom period. Its duration was obviously longer than that of the spring bloom, which is typically about one month. These results show the phytoplankton condition that could be expected during winter and spring as global warming progresses.

Dominance of phosphorus over nitrogen as the limiter to phytoplankton growth rate

Hydrobiologia ◽  
1978 ◽  
Vol 57 (3) ◽  
pp. 209-215 ◽  
Author(s):  
E. B. Welch ◽  
P. Sturtevant ◽  
M. A. Perkins
Keyword(s):  
Growth Rate ◽  
Phytoplankton Growth ◽  
Phytoplankton Growth Rate

The Redfield Ratio and Phytoplankton Growth Rate

1985 ◽  
Vol 65 (2) ◽  
pp. 487-504 ◽  
Author(s):  
P. Tett ◽  
M. R. Droop ◽  
S. I. Heaney
Keyword(s):  
Growth Rate ◽  
Chemical Composition ◽  
Surface Waters ◽  
Growth Rates ◽  
Phytoplankton Growth ◽  
Maximal Growth ◽  
Redfield Ratio ◽  
Phytoplankton Growth Rate ◽  
Marine Surface ◽  
Natural Phytoplankton

Goldman, McCarthy & Peavey (1979b) argued that growth rates of phyto-plankton in apparently oligotrophic ocean waters may near maximal. Their hypothesis was succinctly restated by Goldman (1980): ‘…the chemical composition of phytoplankton is extremely variable under exacting laboratory conditions of nutrient limitation and approaches the ‘Redfield’ proportions (C:N:P of 106:16:1) when neither nitrogen nor phosphorus is limiting so that near maximal growth rates are attained. In marine surface waters the chemical composition of particular matter often is in the Redfield proportions, thus implying that natural phytoplankton growth rates may be close to maximal.’ We argue on theoretical, experimental and observational grounds that this implication may not necessarily be correct.

scholarly journals Adding nitrate and phosphate separately or together in the Central Indian Ocean: a nutrient enrichment experiment

2009 ◽  
Vol 6 (3) ◽  
pp. 2649-2666 ◽  
Author(s):  
S. Tang ◽  
L. Jiang ◽  
Z. J. Wu
Keyword(s):  
Growth Rate ◽  
Indian Ocean ◽  
Water Temperature ◽  
Chlorophyll A ◽  
Nutrient Enrichment ◽  
Phytoplankton Bloom ◽  
Phytoplankton Growth ◽  
Chlorophyll A Concentration ◽  
Central Indian Ocean ◽  
Phytoplankton Growth Rate

Abstract. Nutrient enrichment experiments were carried out in the Central Indian Ocean during the Chinese First Around-the world Research Cruise, adding nitrate, phosphate, or a mixture of both of them to surface seawater. The concentration of nitrate, nitrite, ammonia, and phosphate were analyzed spectrophotometrically, the chlorophyll-a concentration with fluorescence analysis, and the temperature variation during the experiment recorded. Addition of nitrate resulted in rapid growth of phytoplankton concomitant with depletion of nitrate in the water samples. No apparent variation occurred in chlorophyll-a concentration when phosphate was added. Combining nitrate and phosphate proved to be best to promote phytoplankton bloom, and nitrate was depleted prior to phosphate. After nitrate was consumed, a substantial amount of phytoplankton survived on the supplied phosphate. No correlation was found between the nitrate to phosphate ratio and chlorophyll-a or phytoplankton growth rate. We also found no correlation between water temperature and chlorophyll-a or phytoplankton growth rate. We conclude that neither nitrate to phosphate ratio nor water temperature control the growth of phytoplankton.

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