—The paper discusses the spatial distribution of the main parameters of primary production in the Bransfield Strait in the austral summer. The integrated primary production in the strait varied from ...435 to 741 mgC m
–2
day
–1
. The share of primary production in the total production of phyto- and bacterioplankton in the upper 10 m layer was 82–91%. Potential photosynthetic capacity (F
v
/F
m
) was high within the euphotic layer (0.418–0.749) throughout the area. The production parameters in the two main water masses in the strait did not differ. Photosynthetic efficiency (the ratio of the assimilation number and the relative electron transport rate, AN/rETR) varied in different subregions of the study area by almost six times.
Absrtact
The ecological state of the southern part of Lake Baikal was assessed in 2017 based on the phytoplankton and bacterioplankton structure. Nineteen functional groups were identified, five of ...which played the main role: Z (picocyanobacteria from oligotrophic lakes), L
O
(dinoflagellates and cyanobacteria typical of mesotrophic lakes in summer), X1 (species typical of nutrient-rich shallow lakes), MP (mero- and tycho-planktonic species, mainly diatoms), and E (phytoflagellates typical of oligotrophic lakes). The values of community index Q, obtained on the basis of data on the structure of phytoplankton, indicated the excellent ecological status of the lake. Waters of the southern part of Lake Baikal were characterized as oligotrophic and oligosaprobic, while the waters on sites “Shamansky Cape” and “City of Baikalsk” tended to the mesotrophic and β-mesosaprobic status according to the data on the chlorophyll
a
content and microbiological parameters. The absence of significant correlations between phyto- and bacterioplankton parameters may also indicate the oligotrophic status of coastal waters in the southern part of Lake Baikal.
Chlorophyll
a
concentration, the total abundance of bacteria, the number of bacterial cells with active metabolism, and the abundance of saprotrophic bacteria were studied in the surface and bottom ...water layers of Lake Beloe in winter and spring 2015–2016. The abundance of sanitary-indicator microorganisms was determined for the first time with the use of Petrifilm test-systems (3M
TM
Petrifilm™). In most cases, Lake Beloe water in spring and winter was found to correspond to eutrophic level (in terms of chlorophyll
a
concentration in water) and polysaprobic status (in terms of microbiological indices). By its sanitary-microbiological characteristics, the lake is clear—the values of the total microbial count, determined with the use of test-systems 3M™ Petrifilm™ Aqua (AQHC), were <1000 CFU/mL, and the abundance of coliform bacteria, determined with the use of test-systems 3M™ Petrifilm™ Aqua (AQСC), varied from 20 to 135 CFU/100 mL. Coliform bacteria were mostly found in the bottom water layer. It was shown that, in the organization of ecological–microbiological studies, special attention is to be paid to the bottom horizons of water bodies.
In this work, potential (by the fluorescence method) and realized (by the radiocarbon method) phytoplankton primary production and the production of heterotrophic bacteria were determined in the ...euphotic zone of the seaward part of the Gdansk Bay of the Baltic Sea in summer and autumn. The maximum quantum efficiency of photosystem II of phytoplankton (F
v
/F
m
) varied significantly in depth in June (0.33–0.59), but was uniformly very high in October (0.68–0.71), which indicates a potentially more active state of early autumn phytoplankton. Integral primary production in October was almost two times higher than in June (633 and 375 mg C/m
2
per day, respectively), while bacterial production was one-and-a-half times lower (239 and 371 mg C/m
2
per day, respectively). In the upper tenth layer of the water column, autotrophic production (phytoplankton) only slightly exceeded heterotrophic (bacterial) production in June (63% of the total production) and dominated in October (92% of the total production).
The first study on the dynamics of virioplankton abundance (VA) in the coastal waters of the Moscow River in the autumn–winter period at stations differing in the level of anthropogenic impact has ...been performed. The VA in the waters of the more polluted Dzerzhinsky st. (with a mean of 235.6 ± 71.5 × 10
6
particles/mL, varying from 167.79 to 397.39 × 10
6
particles/mL) was higher than in the waters of the less polluted Tushino st. (with a mean value of 129.0 ± 39.6 × 10
6
particles/mL, varying from 61.01 to 186.85 × 10
6
particles/mL) throughout the study. Positive correlation was observed (
R
= 0.6,
p
< 0.01) between the abundances of virio- and bacterioplankton in the waters of the Dzerzhinsky st. We assume that a significant proportion of the virioplankton of the coastal waters o of the Moscow River is represented by bacteriophages. Three quarters of the differences in the VA dynamics were significantly positively correlated with the content of ammonium and phosphates in the waters at the Dzerzhinsky st. Apparently, an increase in the nutrient load is the main factor responsible for the high VA in the waters of the Moscow River in the autumn–winter period.
Cultured hydrocarbon-oxidizing bacteria have been isolated for the first time from bacterioplankton in urban Lake Beloye (Moscow). The taxonomic positions of two bacterial strains (2012B and 2012C) ...isolated from this lake have been determined. Lipids of the strain 2012B comprise C
14:0
–C
19:0
fatty acids, the most abundant of them being C
15:0
(54%), C
16:0
(17%), C
17:0
(10%), and 10-methyl С
18:0
(3.5%). Lipids of the strain 2012C comprise C
14:0
–C
19:0
fatty acids, the most abundant of them being C1
5:0
(45%), C
16:0
(32%), and C
17:0
(9%). A phylogenetic analysis of strain 2012B is performed using the nucleotide sequences of the 16S rRNA (KP779654.1) and
alkB
(KR422620.1) genes and the strain is identified as a typical member of the genus
Rhodococcus
spp. (Actinobacteria, Nocardiaceae). The combination of molecular identification and analysis of biochemical and physiological properties makes it possible to identify strain 2012B as
Rhodococcus
qingshengii
2012B. A phylogenetic analysis of strain 2012C is performed using the nucleotide sequences of 16S rRNA (MG966152) and shows the highest identity (99.57%) of strain 2012С with
Pseudomonas psychrotolerans
and
Pseudomonas oryzihabitans
—
The effect of aqueous unmodified fullerene C
60
dispersions (AFD) at a concentration of 5 mg/L on the total number and metabolic activity of heterotrophic river bacteroplankton was investigated. ...The stimulating effect of AFD on the number of bacterioplankton and on the activity of electron transport chains in its cells is shown. It is established that, in the presence of AFD, the bactericidal activity of antibiotics decreases. The stimulating effect of fullerene on the natural heterotrophic bacterioplankton, which we discovered, casts doubt on the expediency of using AFD as a bacteriostatic agent.
The spatial variability of phytoplankton primary production characteristics has been studied along transects between the Shetland Islands and Iceland (transect I) and along 59.5° N (transect II) from ...June 30 to July 16, 2013. It has been shown that the surface chlorophyll
a
concentration (Chl
0
) varied within more than two orders of magnitude from 0.07 to 6.67 mg/m
3
along transect I and from 0.02 to 3.63 mg/m
3
along transect II. The water column primary production (PP
int
) changed by a factor of 3.8 from 273 to 1040 and by a factor of 5.6 from 68 to 379 mgC/m
2
per day along transects I and II, respectively. It has been established that the spatial variability of Chl
0
and PPint was consistent with the distribution of the main surface flows and thermohaline fronts. This conclusion was made based on a reliable positive correlation between Chl
0
and the zonal potential temperature gradient (
R
= 0.43,
p
< 0.01,
N
= 65). Phytoplankton assimilation activity along transect II depends on the nutrient concentration. This is confirmed by the reliable positive correlation of the assimilation number with the phosphate concentrations (
R
= 0.58,
p
< 0.05,
N
= 76) and dissolved silicon (
R
= 0.51,
p
< 0.05,
N
= 76).
The results of investigations of three Moskva River sites with different degrees of pollution using a complex of microbiological characteristics and the parameters of chlorophyll a fluorescence are ...presented. We determined that the bacterioplankton seasonal dynamics at less polluted waters (Tushino and Vorob’evy Gory) were similar but differed significantly from one in more polluted waters (Dzerzhinskii). The number of bacteria with active electron transport chain, as well as their share in the bacterioplankton structure, was higher in the water of Dzerzhinskii (average annual values of 0.23 × 10⁶ cells/mL and 14%) than that in the less polluted water of Tushino and Vorob’evy Gory (0.14 × 10⁶ cells/mL; 6% and 0.15 × 10⁶ cells/mL; 7%, respectively). From April to October, the content of chlorophyll a and its photosynthetic activity were the highest in Tushino. In Dzerzhinskii, during spring the increase in photosynthetic activity commenced earlier and was more intensive that the increase in chlorophyll a content; i.e., the increase in phytoplankton biomass was temporarily suppressed. We suggest association of this phenomenon with suppression of organic matter synthesis by phytoplankton due to the high water pollution in Dzerzhinskii. The second autumn peak of chlorophyll a content, which was typical of clear water and was observed in Tushino, did not occur in Dzerzhinskii. We recommend combined application of these microbiological parameters and characteristics of chlorophyll a fluorescence for further monitoring.
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