Transcript ppt - Mountain

Diatoms from the sediments of the lake Nižné Terianske pleso
(High Tatra Mts., Slovakia)
Elena Štefková
Dept. Hydrobiology, Institute of Zoology Slovak Academy of Sciences, Bratislava, Slovakia (e-mail: [email protected])
In the frame of international projects AL:PE2 (Acidification of Mountain Lakes) and
MOLAR (Mountain Lake Research) the Tatra Lake Nižné Terianske pleso was
chosen as investigated high mountain lake in Slovakia. Diatom assemblages from
the sediment core of the Lake Nižné Terianske pleso were studied and pH
reconstruction was calculated.
Study Site
Lake:
Location:
Valley:
Position:
Altitude:
Lake area:
Max. depth:
Mean depth:
pH:
Retention time:
Catchment area:
Catchment geology:
Catchment vegetation:
Ice-free period:
Epilithic diatoms and diatoms from sediment traps of this lake were studied too.
Nižné Terianske pleso
High Tatra Mts., Slovakia
Nefcerka
49°10'11"N, 20°00'51"E
1941 m a.s.l.
4.8 ha
44.4 m
18.4 m
6.48
293 days
1.1 km2
granite
alpine meadows: bare rock (1:1)
4 month (July – October)
The lake has an inflow and an outflow.
Methods
Two cores - TERI93/2 (35 cm) and TERI96/7 (30 cm) have been
analyzed for diatoms.
The cores were taken in the years 1993 and 1996 from the
deepest area of the Lake Nižné Terianske pleso. The cores were
subsampled at every 2 mm and these samples were used for
various paleolimnological analyses including analyses for diatoms.
Diatom samples were prepared by the method Battarbee (1986)
and Battarbee & Kneen (1982).
Epilithic diatoms were scraped from the stones 3-times yearly
(1996-1997) in the ice-free period.
Photo V. Kubovčík
Summary diatom diagram - sediment core TERI93/2
Reconstructed pH
Sediment cores
Diatom analysis of the cores show that the assemblages in these cores have a diverse mixture of both planktonic
and benthic taxa. From both cores 28 levels have been analyzed for diatoms. From both cores together a total 121
diatom species were identified, of these 93 agreed. Comparing both cores there were just little differences between
them, regarding only abundance of some species. A summary percentage diatom diagrams clearly illustrate the
most important changes throughout the cores TERI93/2 and TERI96/7.
Fairly constant from the base to the top of the sediment surface were some diatoms such as Achnanthes
minutissima, Cymbella minuta, Denticula tenuis, Gomphonema angustum and Fragilaria brevistriata. In the bottom
part of the cores (to 16 cm) the most abundant were species Asterionella formosa, Fragilaria pinnata, F. brevistriata,
F. capucina var.capucina, Denticula tenuis, Navicula schmassmannii, Achnanthes minutissima and A. curtissima.
From these species Asterionella formosa (typical plankton species) reached abundance higher than 20% while in
the upper part (from 8cm) was rare (less than 1%) or absented. Diatom assemblages started to change in the part
from 9 cm to the top. By some species (e.g. Asterionella formosa, Fragilaria capucina, F. pseudoconstruens, F.
construens, F. pinnata) the clear decrease was registered and some of them practically disappeared. On the other
hand another group of diatoms (Achnanthes spp., Navicula schmassmannii, Orthoseira roeseana) which previously
were not present or were very rare started to increase in its abundance. In the upper part of the core (3 – 0 cm)
diatom assemblages were composed mainly from species such as Achnanthes marginulata, A. levanderi,
A. subatomoides, A. helvetica, Fragilaria brevistriata, Orthoseira roeseana, Neidium bisulcatum, Navicula digitulus,
N. schmassmannii and Aulacoseira distans. The most abundant in layers of sediment core TERI96/7 were Navicula
schmassmanni, which reached in the upper part abundance nearly 40% and Orthoseira roeseana with abundance
about 15%. In the core TERI93/2 reached just 16% abundance.
Reconstructed pH
The reconstructed pH of the core TERI93/2 was stable at approximately 6,9 from the base
of the core to about 2 cm depth. The pH then declines to 6,6 at 0,4 cm depth, recovering to
6,8 at the surface. The reconstructed pH of the core TERI96/7 was approximately 7.04 from
the base to 6.66 in the upper part of the sediment core. In the part of 30 – 9 cm pH varied
about values 7. From 9 cm to the top of the sediment pH declined to 6,66.
Epilithic diatoms
Summary diatom diagram - sediment core TERI96/7
Reconstructed pH
Together 7 epilithic samples were taken from the lake Nižné Terianske pleso, a total of
56 species representing 20 genera, were recorded.
The most common species were several species of genera Achnanthes (e.g.
A. helvetica, A. lapidosa, A. minutissima, A. subatomoides), Cymbella minuta,
Denticula tenuis, Fragilaria capucina, Navicula gallica var. perpusilla and Tabellaria
flocculosa.
Species new for the territory of Slovakia
Achnanthes altaica (Portezky) Cleve-Euler
Achnanthes carissima Lange-Bert.
Achnanthes impexiformis Lange-Bert.
Achnanthes oblongella Oestrup
Achnanthes oestrupii (Cleve-Euler) Hust.
Sediment traps
Sediment traps were exposed in the Lake Nižné Terianske pleso. From four sediment
traps samples a total of 25 genera with 74 diatom species were recorded. Species
composition of such community was dependent on season and time of exposition of
the sediment traps in the lake. The most abundant were several species of
Achnanthes, Denticula tenuis, Fragilaria crotonensis, Orthoseira roeseana and
Tabellaria flocculosa.
Achnanthes scotica Flower
Achnanthes ventralis (Krasske) Lange-Bert.
Amphora inariensis Krammer
Aulacoseira pfaffiana (Reinsch) Krammer
Eunotia incisa Gregory
Eunotia rhomboidea Hust.
Fragilaria pseudoconstruens Marciniak
Gomphonema minutum (C. Agardh) C. Agardh
Gomphonema pumilum (Grunow) Lange-Bert.et Reichert
Navicula digitulus Hust.
Navicula lapidosa Krasske
Navicula medioconvexa Hust.
Navicula pseudokotschyi Lange-Bert.
Navicula stroemi Hust.
Nitzschia alpina Hust.
Surirella bohemica Maly