1 Introduction
This research focused on zooplankton, a key component of the ecosystem linking
primary producers with higher trophic levels. Zooplankton community is characterized by irregular distribution with patches caused by either environmental or
behavioral factors (Omori and Hamner 1982). Because it is typically difficult to
assess detailed information on zooplankton distribution with traditional methods
(e.g. nets), use of alternative methods should be taken into consideration. Acoustic
sampling makes studies of ecosystems fast, non-intrusive, and relatively cheap,
with high spatial and temporal resolution (Wade and Heywood 2001). Optical
method makes it possible to assess zooplankton distribution, abundance and
community size spectra, and has been already proved in practical applications
(Trudnowska et al. 2012; Krupica et al. 2012).
Concurrently with high frequency acoustical measurements, complementary
methods were used—Laser Optical Plankton Counter (LOPC) measurements
delivered high resolution information on zooplankton size spectra and abundance,
together with environmental parameters.
Information on population size spectra allowed implementation of the mathematical model of acoustic scattering on the Arctic zooplankton community. The last
part of research was a comparison between measured values of backscattered
acoustic energy and model-calculated results.
The results presented below were obtained during research conducted in two
fjords of Spitsbergen in the summer of 2013.
2 Study Area
Zooplankton acoustical and optical studies were carried out in two West Spitsbergen fjords, Hornsund and Kongsfjorden, during cruise of r/v Oceania in the
summer of 2013, as a part of the GAME (Growing of the Arctic Marine Ecosystem)
project. Hornsund is regarded as a cold fjord, under the influence of the South Cape
Current, while Kongsfjorden is the fjord influenced by warmer Atlantic type waters,
originating from the West Spitsbergen Current (Fig. 1).
3 Materials and Methods
Acoustic measurements were done with a DT-X echosounder (BioSonics Inc.,
Seattle, USA), working at a frequency of 420 kHz. Downward-looking acoustic
transducer was mounted on a frame attached to the ship, such that the transducer
was submerged 1 m below the surface. The construction allowed the ship to sail
with a speed of approximately 3 knots. Pulse length was set at 0.3 ms and trigger
52
L. Hoppe and J. Szczucka
This research focused on zooplankton, a key component of the ecosystem linking
primary producers with higher trophic levels. Zooplankton community is characterized by irregular distribution with patches caused by either environmental or
behavioral factors (Omori and Hamner 1982). Because it is typically difficult to
assess detailed information on zooplankton distribution with traditional methods
(e.g. nets), use of alternative methods should be taken into consideration. Acoustic
sampling makes studies of ecosystems fast, non-intrusive, and relatively cheap,
with high spatial and temporal resolution (Wade and Heywood 2001). Optical
method makes it possible to assess zooplankton distribution, abundance and
community size spectra, and has been already proved in practical applications
(Trudnowska et al. 2012; Krupica et al. 2012).
Concurrently with high frequency acoustical measurements, complementary
methods were used—Laser Optical Plankton Counter (LOPC) measurements
delivered high resolution information on zooplankton size spectra and abundance,
together with environmental parameters.
Information on population size spectra allowed implementation of the mathematical model of acoustic scattering on the Arctic zooplankton community. The last
part of research was a comparison between measured values of backscattered
acoustic energy and model-calculated results.
The results presented below were obtained during research conducted in two
fjords of Spitsbergen in the summer of 2013.
2 Study Area
Zooplankton acoustical and optical studies were carried out in two West Spitsbergen fjords, Hornsund and Kongsfjorden, during cruise of r/v Oceania in the
summer of 2013, as a part of the GAME (Growing of the Arctic Marine Ecosystem)
project. Hornsund is regarded as a cold fjord, under the influence of the South Cape
Current, while Kongsfjorden is the fjord influenced by warmer Atlantic type waters,
originating from the West Spitsbergen Current (Fig. 1).
3 Materials and Methods
Acoustic measurements were done with a DT-X echosounder (BioSonics Inc.,
Seattle, USA), working at a frequency of 420 kHz. Downward-looking acoustic
transducer was mounted on a frame attached to the ship, such that the transducer
was submerged 1 m below the surface. The construction allowed the ship to sail
with a speed of approximately 3 knots. Pulse length was set at 0.3 ms and trigger
52
L. Hoppe and J. Szczucka