BIOMAD 3.2. BACTERIOPLANKTON, GULF OF BOTHNIA
Bacterioplankton monitoring in the Gulf of Bothnia
Aquatic bacteria, photo: Johan Wikner
Keywords: Baltic Sea, Östersjö, Ostsee, Gulf of Bothnia, Bottniska viken, planktonic bacteria, bakteria.
Contract holder:
Johan Wikner, Umeå Marine Sciences Centre (UMSC),
Norrbyn, 910 20 Hörnefors, Sweden
Phone: +46 90 7865000, +46 90 7867979 fax: +46 90 7867995
E-mail: johan.wikner@umf.umu.se
Project objectives:
The project is a part of a larger monitoring programme; Intensive Monitoring
of the Pelagic Environment. The objective is to follow long-term trends in the
biomass production and abundance of the bacterioplankton as a measure of the
trophic status of the ecosystem. Bacterial biomass production is further an
important part of the ecosystems secondary production, an indirect measure of
the biological respiration, and thereby the ecosystem oxygen demand.
Sampling strategy:
The objective is primarily to gain a proper estimate of the annual mean bacterial
abundance and accumulated biomass productivity in the average water column of
the basins. This will form the basis for an inter-annual trend analysis.
The bacterial growth and abundance are monitored at one coastal station, Öre Estuary
(with code NB1, latitude N 63° 29' 98", longitude E 19° 49' 14"), and at two
open sea stations, Bothnian Bay (with code F9, latitude N 64° 42' 56" longitude E
22° 03' 87") and Bothnian Sea (with code US5b, latitude N 62° 35' 22"
longitude E 19° 58' 41"), see the map with
frames capable browser.
The project began in 1980 at NB1 and in 1991 at F9 and US5b.
BIOMAD stores at the present data for the period 1989-1996.
The sampling is made bi-weekly during the period Maj-September in the Bothnian Sea
(US5b) and June-September in the Bothnian Bay (F9). In October-January the samplings are
made once every month.
Methods:
Water samples are collected with 5 L Niskin bottles at depths 0, 4, 8, 14, 20, 40, 60, 80
and 100 m.
Sub-samples for bacterial abundance are preserved with 1.5% formaldehyde (final conc.). Samples are stained with acridine orange and microscopic slides are prepared within 6 hours from sampling on-board the research vessel (Blackburn et al. 1998). Bacterial abundance is estimated by epifluorescence direct count and bacterial biomass production by the thymidine incorporation technique. Microscopic slides are counted in an epifluorescence microscope and size determined by image analysis within two weeks of sampling (Hobbie et al. 1977). The full procedure is described in standard operating procedures (SOP) at the Umeå Marine Science Center and mainly follow the recommendation of the Baltic Monitoring Programme HELCOM (c.f. Guidelines... 1988).
Sub-samples for estimating the bacterial biomass production are processed according to the tritiated thymidine method using the milliter (Eppendorf) scale version (Smith and Azam 1992). Triplicate samples are inoculated with tritiated thymidine where samples treated with trichloroacetic acid (TCA) serve as control free of bacterial activity. Incubation is done at approx. in situ temperature for 1 hour. The amount of thymidine assimilated into cold TCA precipitable material is analysed in a scintillation counter. Generation of radioactive cold TCA precipitable material is converted to cells produced by the empirical factor 1.0 *1018 cells [mol thymidine-1]. The full procedure is described in standard operating procedures at the Umeå Marine Science Center.
Results, Metadata:
No clear trend in the annual average bacterial biomass could be demonstrated at
the coastal station (NB1) during the period 1984-1994, neither during parts of the period
(Kuosa et al. 1996). The probability to detect a true trend of 5.0% yr.-1 was
0.80 on a 11 yr. data set, according to a power analysis on the annual averages. The
average biomass concentration in the 0-20 m water layer during the whole period was 2.78
mmol C m-3.
No trend in bacterial biomass production could be demonstrated at the coastal station (NB1) for the whole investigation period on either seasonal or annual values. The probability to detect a true trend of 12% yr.-1 was determined to 0.80 on a 10 yr. data set, according to a power analysis on the annual data. If a systematic change have occurred it was therefore probably less than 12% yr.-1. The average annual bacterioplankton biomass production in the 0-20 m water layer during the 10 yr. period was 1.41 mol C m-2 yr.-1.
Time series at the off-shore stations are yet to short for an statistical
trend-analysis to be meaningful. A covariation between all three stations is, however,
appearant on an inter-annual scale.
In order to ensure the correctness of the interpretation prior to the usage of any of the
data in these files, the contract holder responsible for this data set should be
consulted.
The commpressed database is downloadable by FTP or sent as email attachment on request in ZIP-format.
BIOMAD bacterioplankton database format
Literature:
Blackburn, N., Hagström, Å., Wikner, J., Cuadros Hansson, R. and Bjørnsen, P. (1998): Automatic Counting, Measurement, Morphology, and Growth Rate Estimates of Bacteria in Aquatic Samples by Image Analysis. Appl. Environ. Microbiol. submitted MS,
Hobbie, J.E., Daley, R.J., and Jasper, S. (1977): Use of Nucleopore Filters for Counting Bacteria by Fluorescence Microscopy. Appl. Environ.Microbiol. 33: 1225-1228.
Smith, D.C. and Azam, F. (1992): A Simple, Economical Method for Measuring Bacterial Protein Synthesis Rates in Seawater Using 3H-leucine. Mar. Microb. Foodwebs 6: 107-114.
Kousa, H., J. Kuparinen and J. Wikner. (1996): Pelagic Biology of the Gulf of
Bothnia. In HELCOM 1996, Third Periodic Assessment of the State of the Baltic Sea,
1989-1993; Background document Balt. Sea Environ. Proc. No 64 B, p. 40.
Last update: 20 January 1998 by Johan Wikner
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