Fróðskaparrit - 01.01.1999, Blaðsíða 169

VATNPLANTUR í FØROYSKUM VØTNUM VIÐ BLEYTUM VATNI
TAKA LÆTTLIGA ÓLÍVRUNNIÐ KOLEVNIUPP
173
Table 1. Alkalinity (mean ± s.d, n = 2-3) and UTM co-ordinates (zone 29V)for lakes included in this
investigation.
Talva 1. Alkani (Miðal ± s.d., n- 2-3) og UTM samskiparar (øki 29 V) yvir vøtn, sum henda kanning fevnir um.
Lake UTM co-ordinates Alkalinity (meqv L'1)
Eysturoy
Toftavatn 6897580 m.N, 619070 m.E 0.16±0.016
Múlavík 6909700 m.N, 599250 m.E 0.17±0.019
Streymoy:
Saksunarvatn 6902600 m.N, 595940 m.E 0.19±0.013
Mjáuvøtn 6889940 m.N, 604700 m.E 0.13±0.016
Áarstíggjafossur 6861550 m.N, 605760 m.E 0.29±0.005
Pond at Tórshavn 6878290 m.N, 616490 m.E 0.81±0.058
Sandoy:
Norðara Hálsavatn 6863700 m.N, 612100m.E 0.18±0.025
Sandsvatn 6859600 m.N, 614900 m.E 0.37±0.044
Gróthúsvatn 6858620 m.N, 614220 m.E 0.37±0.021
Stóravatn 6858400m.N, 609140m.E 0.31±0.016
Material and methods
Specimens of 26 aquatic macrophyte
species and water were collected in ten
lakes on Eysturoy, Streymoy and Sandoy
(Table 1). Several of the species were col-
lected in more than one lake.
Alkalinity of the lake water was mea-
sured by Gran titration (Mackereth et al.,
1989) of 20 ml samples with 0.1 M HCl us-
ing a Radiometer PHM 84 pH-meter with a
glass combination electrode (Radiometer
GK2401C).
The carbon extraction capacity of the
plants was measured employing pH drift
experiments. Small apical shoots, young,
but with fully developed leaves or thallus
segments, were incubated in closed, 25 ml
glass bottles and allowed to photosynthe-
sise for 18 hours. The incubation medium
was modified from Smart and Barko (1985)
by adjusting the amount of KHC03 and
NaHC03 to give alkalinities of 0.125 meqv
L"1 and 1.0 meqv L"1. The medium was
bubbled with atmospheric air prior to incu-
bation. The bottles were placed on a rotat-
ing wheel in a water-bath at 10°C ± 0.1 °C
and light was provided at 250 pmol photons
m'2 s'1 by a high-pressure metal halide
lamp. After 16 hours of incubation, pH was
measured and alkalinity determined for 10
ml samples by Gran titration. The carbon
extraction capacity is expressed as final-
PH.
The concentration of the different inor-
ganic carbon species was calculated from
alkalinity, pH and temperature, as de-
scribed in Maberly (1996).
Results and discussion
The selection of species included in this
study is listed in Table 2.
The fmal-pH reached in the pH drift ex-
periments at an alkalinity of 1.0 meqv L'1
varied among the different plant species
from 8.55 for Isoetes lacustris to 10.87 for
the filamentous algae Vaucheria sp. (Table