Náttúrufræðingurinn - 2010, Side 67

67
Tímarit Hins íslenska náttúrufræðifélags
Þakkir
Unnur Þóra Jökulsdóttir, Arnþór Garðarsson og Gísli Már Gíslason lásu
greinina yfir í handriti og færðu ýmislegt til betri vegar. Rannsóknir á
fæðuvef Mývatns hafa lengst af verið hópvinna þar sem mun fleiri koma
við sögu en nefndir hafa verið í þessari ritgerð. Á engan mun hallað þótt
Þóru Hrafnsdóttur sé sérstaklega getið. Arnþór Garðarsson hefur verið stoð,
stytta og góður félagi í áratuga samstarfi um Mývatnsrannsóknir. Hafi þau
öll þökk fyrir samstarfið.
Heim ild ir
Arnþór Garðarsson (ritstj.) 1975. Votlendi. Rit Landverndar 4. Reykjavík. 1.
238 bls.
Arnþór Garðarsson 2006. Temporal processes and duck populations: 2.
examples from Mývatn. Hydrobiologia 567. 89–100.
de Ruiter, P.C., Wolters, V. & Moore, J.C. (ritstj.) 2005. Dynamic Food 3.
Webs: Multispecies Assemblages, Ecosystem Development and Environ-
mental Change. Academic Press. 608 bls.
Arnþór Garðarsson & Árni Einarsson 2002. The food relations of the 4.
waterbirds of Lake Myvatn, Iceland. Verh. Internat. Verein. Limnol. 28.
754–763.
Gísli Már Gíslason, Ásgrímur Guðmundsson & Árni Einarsson 1998. 5.
Population densities of the three-spined stickleback (Gasterosteus
aculeatus L.) in a shallow lake. Verh. Internat. Verein. Limnol. 26. 2244–2250.
Jón S. Ólafsson 1990. Fæða mýlirfa í Mývatni. Rannsóknastöð við 6.
Mývatn, skýrsla 8. Náttúruverndarráð, fjölrit 23. 1–35.
Sigrún Huld Jónasdóttir 1984. Fæða svifdýra í Mývatni. Prófritgerð í 7.
líffræði við Háskóla Íslands. 49 bls.
Guðmundur A. Guðmundsson 1984. Fæða holdýrsins 8. Hydra í Mývatni.
Rannsóknastöð við Mývatn, skýrsla 2. Náttúruverndarráð, fjölrit 14.
77–82.
Erla Björk Örnólfsdóttir 1998. Vöktun krabbadýra á botni Mývatns. 9.
Náttúrurannsóknastöð við Mývatn, fjölrit nr. 1. 89 bls.
Haraldur R. Ingvason, Jón S. Ólafsson & Arnþór Garðarsson 2002. 10.
Temporal pattern in resource utilization of Tanytarsus gracilentus larvae.
Verh. Internat. Verein. Limnol. 28. 1041–1045.
Haraldur R. Ingvason, Jón S. Ólafsson & Arnþór Garðarsson 2004. Food 11.
selection of Tanytarsus gracilentus larvae (Diptera: Chironomidae): an
analysis of instars and cohorts. Aquatic Ecology 38. 231–237.
Arnþór Garðarsson 1979. Waterfowl populations of Lake Mývatn and 12.
recent changes in numbers and food habits. Oikos 32. 250–270.
Erlendur Jónsson, Arnþór Garðarsson & Gísli Már Gíslason 1986. A new 13.
window trap used in the assessment of the flight periods of Chironomi-
dae and Simuliidae (Diptera). Freshwater Biology 16. 711–719.
Arnþór Garðarsson, Árni Einarsson, Gísli Már Gíslason, Þóra Hrafns-14.
dóttir, Haraldur R. Ingvason, Erlendur Jónsson & Jón S. Ólafsson 2004.
Population fluctuations of chironomid and simuliid Diptera at Myvatn
in 1977–1996. Aquatic Ecology 38. 209–217.
Árni Einarsson & Erla Björk Örnólfsdóttir 2004. Long-term changes in 15.
benthic Cladocera populations in Lake Myvatn, Iceland. Aquatic
Ecology 38. 253–262.
Bengtson, S.-A. 1971. Variations in clutch-size in ducks in relation to 16.
the food supply. Ibis 113. 523–526.
Guðni Guðbergsson 2004. Arctic charr in Lake Myvatn: the centennial 17.
catch record in the light of recent stock estimates. Aquatic Ecology 38.
271–284.
Árni Einarsson, Gerður Stefánsdóttir, Helgi Jóhannesson, Jón S. Ólafsson, 18.
Gísli Már Gíslason, Isamu Wakana, Guðni Guðbergsson & Arnþór
Garðarsson 2004. The ecology of Lake Myvatn and the River Laxá:
variation in space and time. Aquatic Ecology 38. 317–348.
Jón S. Ólafsson & Paterson, D.M. 2004. Alteration of biogenic structure 19.
and physical properties by tube building chironomid larvae in cohesive
sediments. Aquatic Ecology 38. 219–229.
Arnþór Garðarsson & Sigurður S. Snorrason 1993. Sediment characteris-20.
tics and density of benthos in Lake Mývatn, Iceland. Verh. Internat.
Verein. Limnol. 25. 452–457.
Lindegaard, C. & Pétur M. Jónasson 1975. Life cycles of 21. Chironomus
hyperboreus Staeger and Tanytarsus gracilentus (Holmgren) (Chirono-
midae, Diptera) in Lake Mývatn, Northern Iceland. Verh. Internat.
Verein. Limnol. 19. 3155–3163.
Árni Einarsson, Arnþór Garðarsson, Gísli Már Gíslason & Ives, A.R. 22.
2002. Consumer-resource interactions and cyclic population dynamics
of Tanytarsus gracilentus (Diptera: Chironomidae). Journal of Animal
Ecology 71. 832–845.
Ives, J.D. 2007. Skaftafell in Iceland: A Thousand Years of Change. 23.
Ormstunga, Reykjavík. 256 bls.
Ives, A.R., Árni Einarsson, Jansen, V.A.A. & Arnþór Garðarsson 2008. 24.
High-amplitude fluctuations and alternative dynamical states of
midges in Lake Myvatn. Nature 452. 84–87.
Liebhold, A., Koenig, W.D. & Bjørnstad, O.N. 2004. Spatial synchrony 25.
in population dynamics. Annual Review of Ecology and Systematics 35.
467–490.
Carpenter, S.R. 2003. Regime Shifts in Lake Ecosystems: Pattern and 26.
Variation. Excellence in Ecology 15. 119 bls.
Van de Bund, W.J., Romo, S., Villena, M.J., Valentín, M., Van Donk, E., 27.
Vicente, E., Vakkilainen, K., Svensson, M., Stephen, D., Ståhl-Delbanco,
A., Rueda, J., Moss, B., Miracle, M.R., Kairesalo, T., Hansson, L.-A.,
Hietala, J., Gyllström, M., Goma, J., García, P., Fernández-Aláez, M.,
Fernández-Aláez, C., Ferriol, C., Collings, S.E., Bécares, E., Balayla,
D.M. & Alfonso, T. 2004. Responses of phytoplankton to fish predation
and nutrient loading in shallow lakes: a pan-European mesocosm
experiment. Freshwater Biology 49. 1608–1618
Um höfundinn
Árni Einarsson (f. 1954) lauk B.Sc.-prófi í líffræði frá
Háskóla Íslands 1976 og Ph.D.-prófi í dýravistfræði frá
University of Aberdeen í Skotlandi árið 1986. Árni
hefur unnið að rannsóknum á Mývatni allar götur frá
árinu 1975, fyrst sem aðstoðarmaður Arnþórs Garðars-
sonar prófessors en síðan á eigin vegum og sem starfs-
maður Náttúrurannsóknastöðvarinnar við Mývatn frá
1985. Árni er nú forstöðumaður hennar.
Póst- og netfang höfundar/Author’s address
Árni Einarsson
Náttúrurannsóknastöðinni við Mývatn
IS-660 Mývatn
arnie@hi.is
crustaceans. Monitoring of the food
web has revealed strong fluctuations
that seem to be driven by processes
internal to the food web rather than by
external factors. It seems that the
midge Tanytarsus is a keystone species
in this respect. Its larvae are so numer-
ous on the lake bottom that they eat up
available food and the population
crashes. Other midge populations fol-
low suit because they rely on the same
resource. A mathematical model has
been developed that describes the fluc-
tuations which turn out to be a result
of rapid switching between two modes
of population behaviour, one stable
the other oscillating. Studies of the
model suggest that the Lake Myvatn
ecosystem is vulnerable to just small
changes in the external environment.
This includes the transport of organic
particles (food) into the Tanytarsus
habitat. Reduction of this resource
(which results from changed lake bot-
tom topography due to mining activi-
ties in the lake, 1967–2004) acts to
deepen the fluctuations because it
serves as a food reserve in lean years.
The impact of small fish (three-spined
sticklebacks) as predators may be sub-
stantial but are probably most influen-
tial in the upper levels of the food web
during lean years.
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