Fróðskaparrit - 01.01.1999, Qupperneq 165

169
High Inorganic Carbon Extraction Capacity
of Submerged Macrophytes from Soft-water
Faroese Lakes
Vatnplantur í føroyskum vøtnum við bleytum vatni taka lættliga
ólívrunnið kolevni upp
Tom Vindbæk Madsen and Jens Bagger
Department of Plant Ecology, University of Aarhus, Nordlandsvej 68, DK-8240 Risskov, Denmark
Corresponding author: Tom Vindbæk Madsen, E-mail: Tom.Madsen@biology.au.dk
Úrtak
Vatnplantur (macrophytes) úr tíggju føroyskum vøtnum
við millum 0.16 og 0.8 meqv. L_1 av alkali í sær vóru
tiknar, og kannað varð, hvussu væl tær vóru førar fyri at
taka ólívrunnið kolevni upp. Av 26 sløgum, ið vórðu
kannað, tók um leið helmingurin væl av kolevni upp
samsvarandi við, at tær vóru førar fyri at miðsavna
kolevni. Hin helmingurin sýndi eyðkenni samsvarandi
við spjadda C02 veiting og C-3 fotosamamenning.
Hóast lítið alkali var í føroyskum vøtnum og sostatt lítið
hydrokarbonati, megnaðu tey sløg, sum eru før fyri at
taka kolevni upp, at troyta tað hydrokarbonat, sum var.
Einki samband var funnið millum alkali í vøtnunum og
førleikan hjá plantunum at taka upp kolevni.
Abstract
Submerged aquatic macrophytes from ten Faroese lakes
with an alkalinity between 0.16 and 0.8 meqv L'1 were
collected and their inorganic carbon extraction capacity
determined. Among the 26 species tested, about one-
half had a high carbon extraction capacity consistent
with possession of a carbon concentrating mechanism.
The other one-half showed characteristics consistent
with diffusive C02 supply and C-3 photosynthesis.
Despite the low alkalinity of the Faroese lakes and, thus,
low bicarbonate concentration, the species employing a
carbon concentrating mechanism were able to exploit
the bicarbonate pool of the water. No relationship
between lake alkalinity and carbon extraction capacity
of the plants was observed.
Introduction
Submerged plants in lakes and streams are
often exposed to environmental conditions
significantly different from conditions ex-
isting in terrestrial habitats from which vas-
cular plants are believed to have colonised
freshwater habitats (Raven, 1995). In par-
ticular, the supply rate of C02 and 02 are
substantially lower in water than in air due
to the 104 times lower diffusion rate of gas-
es. The low diffusion rate impedes the gas
flux across the stagnant layer of water sur-
rounding the plants and, thereby, restricts
the exchange rate between plants and bulk
water. As a result, C02 saturation for sub-
merged macrophyte photosynthesis is
reached only at relatively high concentra-
Fróðskaparrit 47. bók 1999: 169-179