CZECH POLAR REPORTS 1 (1): 42-48, 2011
———
Received October 3, 2011, accepted December 2, 2011.
*
Corresponding author: vaczi@sci.muni.cz
Acknowledgement: The authors acknowledge the possibility to use J. G. Mendel station
infrastructure during the Czech Antarctic Expedition (Jan. – March 2010).
42
Summer season variability of dissolved oxygen concentration in
Antarctic lakes rich in cyanobaterial mats
Peter Váczi*, Miloš Barták
Laboratory of Photosynthetic Processes, Section of Plant Physiology, Department of
Experimental Biology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
Abstract
Since 2007, limnological investigation of terrestrial lakes has been carried out at James
Ross Island, Antarctica. The lakes in scope differ in their size, origin, geomorphological
and hydrological characteristics. In several selected lakes, dissolved oxygen is measured
repeatedly each summer season in order to quantify lake- and weather-related
differences. For this study, typical reresentatives of (i) coastal shalow lakes, and (ii)
high-altitude lakes with cyanobacterial mats were chosen. We present data on dissolved
oxygen measured in 3 d interval during January 2010. Within this time, water
temperature decreased gradually from 13 to 3o
C, as well as dissolved oxygen
concentration. It varied within in the range of 12.50-18.0 mg l-1
indicating the values
close to saturation and suprasaturation, respectively. Dissolved oxygen concentration
showed slightly decreasing trend in a course of time. In majority of cases, the lakes with
rich cyanobacterial flora showed higher dissolved oxygen concentrations than Lachman
Lake 2 which posses less cyanobacterial mats than other the lakes involved into the
study. Due to air temperature decrease, Dulanek lake, a high-altitude lake, froze in the
last week of January 2010.
Key words: James Ross Island, Lachman Lake 2, oxygen
Introduction
The relationships between algal and
cyanobacterial mats in Antarctic lakes and
limnological features of particular lakes
have been studied in several parts of
Antarctica. Geographically, the studies
focused mainly on the lakes at McMurdo
Dry Valleys area (Hawes 1993, Vincent et
al. 1993, Moorhead et al. 2005), Vestfold
Hills (Laybourn-Parry et Marchant, 1992),
South Shetland Islands and Antarctic
Peninsula (Vinocur et Pizarro 2000).
Majority of limnological studies have been
related mainly to species richness of
cyanobacterial mats and general chemical
characteristics of water samples.
Therefore, detailed limnological studies
published so far have determined many
characteristics, such as e.g. pH, conductivity,
alkalinity, total dissolved inorganic
carbon, CO2, HCO3, NO3-N, NO2-N, NH4N,
PO4-P, total P, Ca, Mg, K, (see e.g.
Toro et al. 2006). In spite of the fact, that
P. VÁCZI et al.
43
information on dissolved oxygen
concentration in Antarctic lake occured as
early as in 1986 (Wharton et al. 1986),
only limited number of studies has been
published since that time on dissolved
oxygen concentration in relation to
microbial mat community size and
structure, as well as variation of physical
factors such as e.g. incident light and
water temperature. Amount of dissolved
oxygen is considered both biological and
physical factors limiting life and
development of autotrophic organisms in
Antarctic lakes. Actual amount of
dissolved oxygen depends mainly on
physical and chemical characteristics of
water, as well as the development and
physiological activity of photosynthetizing
microbiota (Montecino et al. 1991). These
factors may cause variability of dissolved
oxygen within a single austral summer
season, when water temperature rises due
to full or partial loss of ice and more light
availability in water column.
Since a pioneering study on algal
community of freshwater streams (Hawes
et Brazier 1991), no attempt has been
made to study microbial mats and their
physiological characteristics at James Ross
Island. In 2006, however, Czech research
station J.G.Mendel was built and provided
its infrastucture for annual summer-season
expeditions of Czech and international
scientists to James Ross Island. Therefore,
cyanobacteria of several lakes and seepages
of James Ross Island have been
studied since 2006 (e.g. Komárek et al.
2008). Moreover, long-term investigation
of lakes focused on major limnological
and hydrobiological characteristics started
in 2007. Altogether, 16 lakes in the nortern
part of James Ross Island have yet been
investigated (Nedbalová, Elster, unpublished
data). They represented lakes of
both small and large areas. The lakes
differed also in their character and origin.
Most frequent types were (1) flatbottomed
lakes on coastal terraces, (2)
thermokarst lakes, and (3) corrie lakes.
Some of them were frozen with surface
and bottom ice in the summer season.
In 2009 summer season (Jan-Feb
2009), variation of dissolved oxygen in 7
lakes of James Ross Island was measured
repeatedly to evaluate the differences
related to prevailing weather (Váczi et
Barták 2009). It was found that dissolved
oxygen concentration was reduced by 15-
30% on overcast days (compared to fully
sunny days). In 2010, the same study was
performed in the same lakes and even the
same sampling sites. We hypothesized that
interseasonal diferences in dissolved oxygen
may be distinguised if the local
weather of 2009 and 2010 austral summer
seasons differ. In this paper, we present
some detailed information about the
investigated lakes as well as variation in
oxygen concentration of particular lakes.
Material and Methods
Lake characteristics
Due to colder weather and progressive
freezing of water column, only 4 out of the
7 lakes investigated in 2009, were chosen
for the measurements in 2010. They are
characterized in Table 1. The lakes are
located in deglaciated Northern part of
James Ross Island. According to
geographical location, they may be divided
into two subgroups. The first one
comprises Interlago 1, Interlago 2, and
Lachman Lake 2 (Small Lachman Lake see
References). In fact, small area lakes
Interlago 1 and Interlago 2 form a
communication between much larger lakes
Lachman Lake 1 (Big Lachman Lake - see
References) and Lachman Lake 2 (see
Figs. 1, 3). All they are situated close to
SE coastal line of Cape Lachman, i.e. they
VARIABILITY OF DISSOLVED OXYGEN
44
are distant only 100 m from the sea. The
lakes are located in sedimentary rocks and,
on their west side, surrounded by rich
moss and lichen vegetation formed in the
neighbouring seepages. There are also
several skua nestling sites in close
neighbourhood of the lakes that provide
nutrients to the seepages and lakes.
Fig. 1. General view on Cape Lachman with the indication of lakes: (1) Lachman Lake 1 (Big
Lachman Lake), (2) Interlago 1, (3) Interlago 2, and (4) Lachman Lake 2 (Small Lachman Lake).
Locality Latitude
(South)
Longitude
(West)
Altitude
(m a.s.l.)
Maximum
Depth (m)
Interlago 1* 63.7985567 57.8101200 12 m 0.5
Interlago 2* 63.7989033 57.8104816 12 m 0.7
Lachman 2* 63.7998683 57.8087217 10 m 1.5
Dulanek* 63.8170399 57.8458549 220 m 1.1
Table 1.. Geographical characteristics of the lakes involved into the study. Lake Lachman 2
represents an official geographical name. The other names are provisional, suggested for official
geographical nomenclature of the Jamess Ross Island. An arterisk indicates that the name of the
lake is provisional.
Lake Dulanek is located nearby Windy
Pass at the height of 220 m a.s.l. It is
rather a small lake of area of about 25 m2
formed in a shallow depression at a SEfacing
foothill of the Lachman Crags mesa
(Fig. 2). The depth of water column varies
within a season, it is about 1.1 m at the
begining of austral summer and 0.7 at the
1
2
3 4
P. VÁCZI et al.
45
end of austral summer. Due to neighbouring
rock walls it is sun-lit only for a
limited period of a day. During austral
summer, direct sunshine is available only
to 15:30 h local time. The lakes are rich in
cyanobacterial mats. Especially in the
Interlago1, Interlago 2, and Dulanek, lake
bottom is fully covered by a cyanobacterial
mat (see Fig 3). Dominating matforming
specieas are Calothrix sp.,
Calothrix elsteri, Leptolyngbia antarctica,
Hassallia antarctica, Hassallia andreassenii
sp. nova as reported by Komárek et
Elster (2008), Komárek et al. (2008).
Fig. 2. Dulanek Lake represents an example of smale-area water pool. The bottom is covered by
thick cyanobacterial mat.
Dissolved oxygen measurements
Dissolved oxygen concentration was
measured repeatedly in the interval of
about 3 d in January 2010. The
measurements were stopped on Jan 30th,
when one of the lakes froze to its bottom.
The measurements were taken within the
period of 10:00 to 14:00 of local time. On
each measuring day, the lakes were visited
and dissolved oxygend measured in the
same sequence of sites: (i) Interlago 1, (ii)
Interlago 2, (iii) Lachman Lake 2, (iv)
Dulanek. At each site, there were 5-7
sampling sites, location of which was the
same as in the former study (Váczi et
Barták 2009). The oxygen concentrations
were measured by a portable Oxymeter –
WTW Oxi 197i equipped with a WTW
CellOx 325 electrode. The probe was
placed into the depth of about 20 cm and
oxygen concentration measured when an
equilibrium (constant value) was reached.
Repeated measurements of at least 5
values were recorded for each sampling
site. Mean values of dissolved oxygen
concentration and water temperature for
each sampling site and lake, respectively,
were calculated.
VARIABILITY OF DISSOLVED OXYGEN
46
Fig. 3. Cyanobacterial mats formed in Interlago 2 (in front) and Interlago 1 lakes (in the middle).
Fig. 4. Oxygen concentrations (bars) and water temperature course (scatter graph) in several lakes
at the Northern part of the James Ross Island recorded in January 2010. The values are means of at
least 5 replicates. Error bars represent ±SD.
P. VÁCZI et al.
47
Results and Discussion
Water temperature decreased gradually
in all investigated lakes in Jan 2010 (Fig.
4). However, in Dulanek Lake, the rate of
derease was higher then in other lakes
from Jan 20th. A week later, Dulanek
Lake froze completely. It is associated
with different geomorphological position
of the lakes. While Dulanek Lake is
located in 220 m a.s.l and could be ranked
a small unstable lake, the other lakes are
shallow coastal lakes that, due to higher air
temperature, freeze later. Recently, more
detailed data will be available on the
process of ice fromation and Dulanek Lake
freezing, because there is an automatic
measuring system (established in February
2011) recording water temperature profile
in Dulanek Lake (M. Bartak, unpublished).
For majority of measurements, dissolved
oxygen concentrations were higher in the
Interlago 1 and Interlago 2 Lakes then in
Lachman Lake 2, which was comparable
to the data from 2009 austral summer
season (Váczi et Barták 2009). Absolute
dissolved oxygen values (means for
particular date) were slightly higher in
2010 (12.0 - 19.0 mg l-1
) than in 2009
(11.0 - 14.5 mg l-1
). This indicates, that
oxygen was close to saturation point in
both austral summer season – it is reported
that for majority of Antarctic lakes, the
value of 12.0 mg l-1
indicates saturation
(Toro et al 2006).
With the exception of Interlago 1 Lake,
dissolved oxygen values were found
significantly higher on Jan 20th than on
other days. This might be attributed to the
weather of a fully sunny day. High
radiation doses, in spite of a drop in water
temperature (c.f. Jan 18th and 20th –
Fig. 4), caused an increase in dissoved
oxygen concentration, similarly to what
was evidenced in 2009 (Váczi et Barták
2009).
It can be concluded that the lakes on
James Ross Island, due to their
geomorphological and hydrological
differences, represent an important
ecosystem components. Their species
richness of cyanobacterial and algal flora
makes them attractive objects for further
limnological, hydrological, ecophysiological,
and photosynthetic studies.
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