Lake Myvatn and the River Laxá: An introduction

Abstract

In July 1999 and May 2001 a group of limnologists and other scientists involved in the research of Lake Myvatn gathered in the village of Skutustadir by the lake for two symposia to discuss and sum up the results based on the research and monitoring that has been conducted there over the past quarter of a century. The ensuing papers now appear in this issue of Aquatic Ecology under the heading 'The Ecology of Lake Myvatn and the River Lax– Temporal and Spatial Variation'.

Full text

Lake Myvatn and the River Laxá: An introduction
Árni Einarsson
Myvatn Research Station, 660 Myvatn, Iceland (e-mail: arnie@hi.is)
Abstract
In July 1999 and May 2001 a group of limnologists and other scientists involved in the research of Lake Myvatn
gathered in the village of Skutustadir by the lake for two symposia to discuss and sum up the results based on the
research and monitoring that has been conducted there over the past quarter of a century. The ensuing papers
now appear in this issue of Aquatic Ecology under the heading ‘The Ecology of Lake Myvatn and the River
Laxá – Temporal and Spatial Variation’.
The Devil’s piss
Lake Myvatn has caught the attention of naturalists
for a long time. In 1752, two explorers arrived at the
edge of the volcanic zone in northern Iceland. From a
vantage point they caught a glimpse of Lake Myvatn
in the midst of a volcanic landscape dotted with cra-
ters set against a background of steep hills. They
could also see the River Laxá cascading through the
lava field as it emerged from the lake. This was a
place they knew for its reputation for rich fishing and
abundant bird life. They recorded their impression in
their travel journal, writing: ‘And over there, Lake
Myvatn area was revealed, black and gruesome in
appearance’ !Ólafsson 1772". Their statement echoed
an age-old legend about the origin of the lake: when
God had made the sun, the Devil became mad with
jealousy. He peed towards it in order to extinguish
this glory of the creation. He missed, but instead Lake
Myvatn was formed! In the same vein an 18th cen-
tury cartographer, Thomas Knoff, remarked on Lake
Myvatn: ‘In this district there are midges so numer-
ous that the grass is blackened and the inhabitants are
forced to conduct their work at night.’ A learned 18th
century Icelander was equally outspoken when
describing his country: ‘Iceland,’ he said ‘can be seen
as a kind of large pile of rocks ...its people are quar-
relsome, self-destructive, extremely discordant, ava-
ricious, dishonest and ill-tempered. Good men are in
the minority and they have no say!’ !Jón Ólafsson in
Thoroddsen 1892–1904".
In contrast to these rather bleak 18th century
remarks, present-day Lake Myvatn, despite its abun-
dant insect life, is an object of admiration for its
natural beauty, praised by poets and a cherished des-
tination for thousands of travelers. And the local
people living along Myvatn and the Laxá have a
reputation for having been in the forefront of social
development in Iceland. The black basalt landscape
may look alien and barren but its setting is in con-
trast to the fertile lake with rich greenery on its shores
and islands. Precipitation is absorbed by the porous
lava and channeled underground through tectonic fis-
sures until the water gushes forth along the lake
shore. Some of the underground streams are cold but
others are warm, owing to the proximity to geother-
mal fields. Where the lava rocks meet the lake sur-
face, earth and water intermingle along a jagged
shoreline. The contact between geology and ecology
is most intimate.
A heaven for bugs and birds
The lake is by far the largest of several oases created
where groundwater wells up at the edge of the volca-
nic area in North Iceland. Water retention time in the
lake basin is long enough to allow the unfolding of a
rich aquatic flora and fauna. And the lake’s size and
shallowness ensure optimal feeding conditions for
breeding water birds that also find an abundance of
nest sites in the surrounding wetlands. The excep-
tional density and diversity of breeding ducks have
made the name of Lake Myvatn known over the
world. Less celebrated are their food resources, the
enormous numbers of midges and blackflies that
emerge from the lake and from its outflow, the River
Aquatic Ecology 38: 111–114, 2004.
© 2004 Kluwer Academic Publishers. Printed in the Netherlands.
111

Laxá. In fact the remark made by Thomas Knoff, the
cartographer, might just as well apply today. A num-
ber of 19th century naturalists visited Lake Myvatn.
One of them was Friedrich A.L. Thienemann, a Ger-
man doctor and ornithologist who made the first de-
tailed sketch of its wildlife, including the swarms of
chironomid midges !Figure 1".
Modernisation
The prevailing, slightly romantic, view of the lake in
the early 20th century was that the local farmers were
living in harmony with the natural resources, in par-
ticular with fish stocks and ducks. This view fitted in
with the ideas of the early ecologists about the bal-
ance of nature !Pimm 1991". In the mid-20th century,
industrialization set in, almost without warning, and
soon the local people found themselves involved in
plans for the tapping of energy sources and mining
operations. There had been some export of sulphur
from solfatara fields over the centuries, but the new
plans were a more direct threat to the ecological
character of the area. Hydropower schemes that
involved turning Lake Myvatn and the River Laxá
Figure 1. A scene from one of the islands in Lake Myvatn in 1821. The birds include great northern diver !Gavia immer", horned grebe
!Podiceps auritus", red-breasted merganser !Mergus serrator", Barrow’s goldeneye !Bucephala islandica", scaup !Aythya marila", long-tailed
duck !Clangula hyemalis", red-necked phalarope !Phalaropus lobatus", redshank !Tringa totanus", whimbrel !Numenius phaeopus", Arctic
skua !Stercorarius parasiticus"and Arctic tern !Sterna paradisaea". A pseudocrater in the background. Note the chironomid swarm on the
right-hand side. A colored engraving from Thienemann !1827".
112

into reservoirs were met with fierce opposition and
eventually led to the protection of the area as a nature
reserve !Ólafsson 1981". Mining the lake sediments
for diatomite was, however, started in 1967 and is still
continuing. Concerns about the future of the lake’s
ecosystem, partly stimulated by what the local farm-
ers described as a crash of the biota in the early
1970s, led to programmes of limnological monitoring
and research directed by Pétur M. Jónasson, profes-
sor of limnology at the University of Copenhagen,
Denmark. The first research results were published in
1979 as a memoir on Lake Myvatn in Oikos !Jónas-
son 1979". Research and monitoring since then has
been conducted jointly by the Myvatn Research Sta-
tion and the University of Iceland, with important
contributions from several other research organiza-
tions. A wealth of data on the temporal and spatial
aspects of the ecosystem has been collected, and not
surprisingly, midges and blackflies still play a central
role.
Ups and downs
Scientific monitoring of the chironomids and other
components of the food web over the last 25 to 30
years has revealed large quasi-cyclic population fluc-
tuations with a periodicity of 5–9 years during which
the ecosystem is driven from one extreme to the other.
During years of low chironomid populations there are
hardly any midges to be seen. In contrast, in years of
maximum abundance, chironomids occur at such high
density that their larvae thickly blanket the lake bot-
tom with their tubes and the mating swarms blacken
the sky. Documents from the 1920s and catch statis-
tics from 1900 to the present indicate that fishing in
Lake Myvatn can be quite variable and is related
mainly to food conditions in the lake !Sæmundsson
1923; Gardarsson and Einarsson 2000". It is, how-
ever, becoming increasingly evident that the present
fluctuations in the chironomid populations in Lake
Myvatn are more extreme than witnessed before. The
unique decline in the commercial fishery, beginning
in about 1970 and now reaching an all-time low,
seems to be a direct consequence of repeated periods
of starvation leading to high mortality rates and low
recruitment. The fluctuations are driven by processes
intrinsic to the ecosystem and have little or no causal
relationship with climate or episodes of volcanic ac-
tivity. This changing behaviour of the ecosystem has
raised concerns about the impact of modern human
activities. Mining pits in the lake bottom cause relo-
cation of freshly formed sediment, an increase in the
N:P ratio and the disruption of macrophyte commu-
nities. Hydrodynamic modeling has revealed that the
scale of sediment focusing to the mining pits is very
large. The trophic status of Lake Myvatn is in the long
run intimately linked to the geological setting. The
short-term nutrient dynamics are, however, domi-
nated by internal loading from the sediments. Much
has been learned about these processes in Lake My-
vatn recently !papers in this issue"but their relative
importance and interactions during different phases of
the ecosystem cycles remain to be worked out.
A conservation area?
The high conservation value of the Myvatn/Laxá area
is widely recognized. The area was declared a nature
reserve in 1974 and designated a Ramsar site in 1978.
The conservation of Myvatn/Laxá is not an easy task,
however. The complex dynamics of the ecosystem
and its large temporal variation render it impossible
to predict exactly how individual populations will re-
spond to modern activities. This creates a manage-
ment challenge and should have implications for the
conservation policy for this area. The only sound
strategy seems to be not to interfere with the
physico-chemical variables of the lake’s ecosystem,
such as water depth, light regime and water chemis-
try. To use a simple analogy, the strategy should be
the same as when keeping a house plant alive: mod-
erate clipping of leaves does little harm, but it is not
wise to disrupt the basic components of water, light
and nutrients. This principle is a cornerstone of the
policy of ‘wise use’ and precaution advocated by the
Ramsar Convention for Wetlands of International Im-
portance.
A laboratory of wildlife ecology
Density fluctuations in the chironomids cause both
positive and negative feedbacks within the food web
and have caught the attention of scientists. Therefore,
Lake Myvatn has become a natural laboratory of
wildlife ecology relating recruitment of waterfowl to
their food resources. The River Laxá has also had
many of its ‘secrets’ unveiled; its simple food web
and its production gradients due to unidirectional flow
of organic particles has proved fertile ground for im-
portant research. Other ecological research activities
include tracing of groundwater sources, climate
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analyses, palaeolimnological studies and mapping of
the benthos.
This issue of Aquatic Ecology presents 17 papers
on the research conducted over the last 2 to 3 decades.
In the first report, Kristmannsdóttir and Ármannsson
use chemical analyses to separate the different
sources of groundwater feeding the springs on the
lake shore. Björnsson and Jónsson describe the
climate and climatic variability in the Myvatn area.
With so much data on the long-term variability in the
Myvatn biota it is essential to have background infor-
mation on climate. This includes the North Atlantic
Oscillation !NAO". Weather influences the Myvatn
environment, as demonstrated by Kjaran et al., where
a hydraulic model allows the calculation of wind-
driven currents and transport of resuspended sediment
for various wind scenarios. The next three papers deal
directly with the role of the lake sediment as a source
or sink of solutes !internal loading". The studies by
Thorbergsdóttir et al. and Thorbergsdóttir and Gísla-
son are based on benthic enclosures that allow the es-
timation of fluxes across the sediment-water interface.
The first paper focuses on oxygen, the second one on
nutrients. The third paper, by Gíslason et al., uses
gradients in the interstitial water to calculate the dif-
fusion of solutes. The growing evidence that Tanytar-
sus gracilentus, the dominant chironomid, can play a
key role in the ecosystem has stimulated some
research projects. Its tube building activity changes
the physical characteristics of the sediment surface, as
described by Ólafsson and Paterson. Ingvason et al.
studied the food selection of Tanytarsus larvae. Gar-
darsson et al. summarize the results of the monitoring
of the chironomids, which began in 1977 and has
yielded a continuous record of all the ca. 40 species.
Their paper shows clearly the enormous fluctuations
in some of the populations. In their two studies on the
Cladocera, Örnólfsdóttir and Einarsson describe vari-
ability in time and space, both the seasonal and dec-
adal. The long-term record shows a dramatic change
in species composition. Two contributions on fish
follow, one on the Arctic charr, the main species of
the commercial fishery in the lake, the other on the
brown trout which is a source of much recreational
fishery in the River Laxá. The charr paper, by Gud-
bergsson, describes the diminishing fish catches in the
lake and the results of a monitoring study. The trout
study by Gíslason and Steingrímsson deals with sea-
sonal variation in feeding and its connection with the
life history of blackflies. Two papers on the Myvatn
ducks, by Gardarsson and Einarsson, relate changes
in their populations with the food supply. The first in-
vestigation demonstrates correlations between pro-
duction of ducks and chironomid populations. The
second study investigates the relationship between
chironomids and the distribution and numbers of
moulting ducks. Then follows a contribution by Tho-
rarinsson and Einarsson on habitat use of the horned
grebe, one of the characteristic birds of the Myvatn
area. The final paper, by Einarsson et al., gives an
overview of some spatial and temporal aspects of the
ecosystem, with data to illustrate sediment resuspen-
sion, distribution of macrophytes and a palaeolimno-
logical record extending back for 2300 years.
The volcanic area of Iceland is the only substantial
part of the mid-Atlantic rift zone exposed above sea
level. This volcanic setting and the resulting hydro-
logical conditions at Lake Myvatn are quite rare, if
not unique, worldwide. The old legend about the
Devil’s involvement in the creation of the lake may
have been slightly incorrect, but underground activity
has certainly been a major contributing factor. In
combination with the impoverished macrofauna of
Iceland due to its remoteness as an oceanic island and
high latitude, this makes Myvatn quite an attractive
subject for study. The lake is also an interesting ob-
ject for comparison with other well-investigated shal-
low, eutrophic lakes on both sides of the Atlantic
Ocean.
References
Gardarsson A. and Einarsson Á. 2000. Monitoring waterfowl at
Myvatn, Iceland. In: Comin F.A., Herrera J.A. and Ramirez J.
!eds", Limnology and Aquatic Birds. Monitoring, Modelling and
Management. Universidad Autónoma de Yucatan, Mérida
!Mexico". Memorias 4: 3-20.
Jónasson P.M. 1979. Ecology of eutrophic, subarctic Lake Mývatn
and the River Laxá. Oikos 32: 1–308.
Ólafsson E. 1772. Vice-Lavman Eggert Olafsens og Land-Physici
Biarne Povelsens Reise igiennem Island, foranstaltet af Viden-
skabernes Sælskab i Kiöbenhavn; og beskreven af forbemeldte
Eggert Olafsen. Jonas Lindgrens Enke, Soröe, Denmark.
Ólafsson H. 1981. A true environmental parable: The Laxa–My-
vatn conflict in Iceland, 1965–1973. Environmental Review 5:
2–38.
Pimm S. 1991. The Balance of Nature? Ecological Issues in the
Conservation of Species and Communities. University of Chi-
cago Press, Chicago, USA.
Sæmundsson B. 1923. Fiskirannsóknir 1921–1922. Andvari 48:
67-107, Reykjavik, Iceland.
Thienemann F.A.L. 1827. Reise im Norden Europas, vorzüglich in
Island, in den Jahren 1820 bis 1821. Carl Heinrich Reclam,
Leipzig, Germany.
Thoroddsen Th. 1892–1904. Landfrædisaga Islands. Hid íslenska
bókmenntafélag, Kaupmannahöfn, Denmark.
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