XV International Symposium

on Chironomidae

Edited by

Leonard C. Ferrington Jr.

The University of Minnesota Minneapolis, Minnesota

XV International Symposium

on Chironomidae

Edited by

Leonard C. Ferrington Jr.

The University of Minnesota Minneapolis, Minnesota

ii

A contribution by the

Chironomidae Research Group Department of Entomology

at the University of Minnesota

Cover and Title Page Illustrations by Leonard C. Ferrington Jr. (Editor)

The Editor would like to acknowledge and thank the Academy of Natural Sciences of Philadelphia for

permission to use, in modified form, the image of an adult male tanypod from the cover of Dr. Selwin S. Roback’s (1971) publication, “The Adults of the SubfamilyTanypodinae (=Pelopiinae) in North

America (Diptera: Chironomidae) as the archetype for the conference logo. Please note, however,

that in the process of modifying the image it has been transformed into a species of Prodiamesinae!

Copyright

© 2010 by Leonard C. Ferrington Jr.

All rights reserved. No part of this publication may be reproduced, stored in a computerized system,

or published or distributed in any form or manner (including electronic, mechanical, reprographic, or photographic, without prior written permission from the Editor.

Literature Citation

Text:

Ferrington, L. C., Jr. (editor). 2010. Proceedings of the XV International Symposium on Chironomidae. Chironomidae Research Group, University of Minnesota, Saint Paul,

Minnesota 385 pp. + viii.

Article:

Wuelker, W. 2010. The role of chromosomes in chironomid systematics, ecology and phylogeny, pp. 1-13. In: Ferrington, L. C., Jr. (ed.). Proceedings of the XV International

Symposium on Chironomidae. Chironomidae Research Group, University of Minnesota,

Saint Paul, Minnesota 385 pp. + viii.

Credits

Special Thanks to: Ms. Claire Serieyssol Bleser

Publications Coordinator:

Proceedings of the XV International Symposium on Chironomidae. Department of Entomology, University of Minnesota

219 Hodson Hall, 1980 Foley Hall

Saint Paul, Minnesota 55108-6125

iii

iv

The XV International Symposium on Chironomidae was convened August 12-15, 2003 on the Minneapolis Campus of the University of Minnesota. Contributed papers sessions and poster displays were held in the Basic Science and Biomedical Engineering Building on Church Street in Minneapolis. Eighty-two delegates registered for the symposium and seventeen accompanying persons, including spouses and several children, attended social events. The program included the traditional Honorary Thienemann Lecture, followed by Seventy-five platform and poster presentations. The Symposium Program, giving a complete list of all scheduled presentations and Symposium activities, is included at the end of the proceedings. Delegates arriving early for the symposium participated in a day long pre-meeting social event, and

several people stayed after the symposium to participate in an optional post-meeting excursion to the headwaters of the Mississippi River, Northern Minnesota and the North Shore of Lake Superior on August 15-17. Two Committees worked hard to make the conference a success and to ensure the visits by delegates, accompanying spouses, children and others to Minnesota were pleasant. The Program Committee, consisting of Leonard Ferrington, Barbara Hayford, Susan Gresens, James Kennedy, Will Bouchard, Byron Karns, Dan Hansen and Henrique Paprocki, was responsible for the “Science” of the meeting. The Local Arrangements Committee was largely responsible for developing and coordinating the “Social” aspects of the meeting, and consisted of Dean Hansen, Leonard Ferrington, David Maschwitz, Jim Shaver, Will Bouchard and Dan Hansen. Generous support for the conference was provided by the Department of Entomology at the University of Minnesota, Emmons & Olivier Resources, an environmental engineering firm specializing in stormwater management, EcoAnalysts, Inc., an environmental consulting company specializing in invertebrate monitoring, and The Mill Stream Association, a local citizen-based organization concerned with water quality in eastern Minnesota.

An Evening Mixer was held from 7:00 until 9:30 PM on Tuesday Evening, 12 August 2003 at the Weisman Art Museum, located on the Minneapolis Campus of the University of Minnesota near the conference venue. Light hors d’ oeuvres and beverages were provided. Entertainment consisted of a lecture and slide show by Dr. Dean Hansen on Underwater Photography of Aquatic Insects. Refreshments for this mixer and all other social events were

donated by EcoAnalysts, Inc.

http://www.entomology.umn.edu/chironomidae/deanphoto.htm

v

On Thursday, 14 August 2003, delegates were treated to an evening buffet dinner aboard the Betsy Northrup River Boat while touring the Mississippi River near Minneapolis. The evening dinner and riverboat cruise lasted 3 hours and was attended by all registered delegates and their accompanying guests. The River Boat Cruise was partially underwritten

with a generous contribution by Emmons & Olivier Resources.

Our symposium ended with a business meeting during which we selected the venue for the XVI International Symposium in 2006. The discussion was led by Ole Sæther. The Czech Republic, China and Madeira were offered as potential venues. A decision was made to accept Madeira as the venue for the XVI Symposium on Chironomidae in 2006. Thirty-five of the presentations/posters given during the symposium and one additional contributed paper were submitted for publication in this proceedings. All manuscripts received technical suggestions by at least two anonymous reviewers, along with some text editing and formatting to standardize page size and font. Authors were asked to conform to formatting instructions for the Journal of the Kansas Entomological Society, however final

punctuation and style for text citations and references were dictated by the preferences of individual authors. The full unabridged text of the Thienemann Honorary Lecture is included, and has been posted on-line. The remaining papers have been divided into four general categories by subject: Distribution, Life Histories and Ecology (20 papers), Cytogenetics and Molecular Biology (four papers), Taxonomy (eight papers) and Special Featured Contributions (three papers). The Program Committee would like to thank the Academy of Natural Sciences of Philadelphia for kindly providing the collections of reprints of Dr. Selwin S. Roback that were used as student prizes for best research papers during the Symposium. We would especially like to acknowledge and thank Dr. Jon Gelhaus for providing the reprints and for his help in developing the concept for the awards. We would also like to thank the Academy for permission to use, in modified form, the image from the cover of Dr. Roback’s (1971) publication, “The Adults of the SubfamilyTanypodinae (=Pelopiinae) in North America (Diptera: Chironomidae)” as the archetype for our logo. Please note, however, that in the

process of modifying the image it has been transformed into a species of Prodiamesinae!

Leonard C. Ferrington Jr.

A contribution of the

http://www.padelfordboats.com/fleet.html

vi

PROCEEDINGS OF THE XV INTERNATIONAL SYMPOSIUM

ON CHIRONOMIDAE

Table of Contents

The Thienemann Honorary Lecture THE ROLE OF CHROMOSOMES IN CHIRONOMID SYSTEMATICS, ECOLOGY AND PHYLOGENY WOLFGANG F. WUELKER………………………………………………………………………………………………...1

DISTRIBUTION, LIFE HISTORIES AND ECOLOGY Production and Life Cycle of Chironomus major (Diptera: Chironomidae) in Kentucky Lake, USA PINAR BALCI, DAVID S. WHITE and GARY RICE……………………………………………...…………………….14 Longevities and Survivorship Patterns of Adult Diamesa mendotae, a Winter-Active Chironomidae. LEONARD C. FERRINGTON, Jr., BYRON KARNS and R. WILL BOUCHARD, Jr., …………….………………22 A New Technique For Using Chironomid (Diptera) Remains in Paleoclimate Research DONNA R. FRANCIS, MATTHEW J. WOOLLER, GIFFORD H. MILLER, IAN R. WALKER, MARILYN L. FOGEL and ALEXANDER P. WOLFE…………………………….…………………………………….30 Intersex in the Terrestrial Chironomid Bryophenocladius illimbatus JAN FROUZ…………………………………………………………………………………………………………………37 Terrestrial Chironomids in Disturbed Habitats JAN FROUZ…………………………………………………………………………………………………………………41 The Production of Chironomids and Blackflies in a Subarctic River GÍSLI MÁR GÍSLASON and ARNTHOR GARDARSSON……………………………………………………….……45 Chironomid Species Assemblages of Streams Draining Areas of Serpentine Versus Non-serpentine Bedrock SUSAN E. GRESENS and LEONARD C. FERRINGTON, Jr., ………………………………………………………55 The Impact of Bank Protection Work on the Chironomid Fauna (Diptera: Chironomidae) in the Middle Reaches of the Chikuma River in Central Japan KIMIO HIRABAYASHI and MASARU YAMAMOTO………………………………………………………………….70 Relationships of Chironomidae with Hydroperiod in Eastern Everglades National Park RICHARD E. JACOBSEN and SUE A. PERRY………………………………………………………………………78 Chironomid Assemblages in Different Alpine Stream Types VALERIA LENCIONI and BRUNO ROSSARO…………………………………………………………………………95 Definition and Assignment of Indicator Weights to Different Chironomid Species LAURA MARZIALI, CARLOTTA CASELEGMO, VALERIA LENCIONI and BRUNO ROSSARO……………103

vii

DISTRIBUTION, LIFE HISTORIES AND ECOLOGY, continued The Chironomidae (Diptera) of the Taro River (Italy) LAURA MARZIALI, CARLOTTA CASELEGNO, GIORGIO HANOZET, GIUSEPPE PARENTI, MATILDE FORCELLA, ELISAl BERRA, ROBERTO GIACCHINI and BRUNO ROSSARO……………………109 Ontogenic Changes in the Diet of Lentic Chironomid Larvae with Emphasis of the First Instar Larvae J. S. ÓLAFSSON………………………………………………………………………………………………………….118 Chironomidae (Diptera) Living in Freshwater Sponges (Porifera) in Brazil FABIO DE OLIVEIRA ROQUE, SUSANA TRIVINHO-STRIXINO, SHEYLA R. M. COUCEIRO, NEUSA HAMADA and CECILIA VOLKMER-RIBEIRO…………………...…………………………………………131 Lake Reference State Deduced From Chironomid Pupal Skin Data LESLIE P. RUSE and STEPHEN J. BROOKS………………………………………………………………………..140 Biodiversity of Chironomidae Larvae (Diptera) and Oligochaeta (Annelida) in Snyder’s Branch Creek (Salem, Virginia, United States of America): Testing for Ecological Discontinuities JORGE A. SANTIAGO-BLAY, BRIAN C. WILSON, and CHRISTINE E. TAYLOR………………………………156 Chironomidae of a Floodplain Pond in Córdoba, Argentina JOHN B. STAHL……………………………………………………………………………………………….………….168 Finding the Best Measures of Chironomid Community Response to Disturbance in the Upper Trinity River Basin, North Central Texas JAYNIE M. STEPHENSON and JAMES H. KENNEDY…………………………………………………..………….174 New Records and Range Extensions for Several Genera of Chironomidae From Lake Superior KEVIN T. STROOM, KURT SCHMUDE, JIM SNITGEN, STEPHEN J. LOZANO, TIMOTHY CORRY and JILL V. SCHAROLD…………………………………………………………………………………………..….…184 Chironomidae of the Kenai River From Collections of Pupal Exuviae DAVID C. WARTINBEE…………………………………………………………………………………………………196

CYTOGENETICS AND MOLECULAR BIOLOGY Chromosomal Evolution of Nearctic and Palearctic Chironomus Species (Diptera: Chironomidae) IYA I. KIKNADZE, MALCOLM G. BUTLER, LARISSA I. GUNDERINA, ALBINA G. ISTOMINA, VLADIMIR D. GUSEV and LUBOV A. NEMYTIKOVA……………………………………………………….………203 Preliminary Physical Maps of the Chironomus Genome, with a Focus on Genes Potentially Involved in Response to Heavy Metals JON MARTIN, HENRY CHUNG, THAVARNALAR BALAFRISHNAN and CHARLES ROBIN………………222 Cytogenetic Biomarkers in Chironomus riparius Mg. (Diptera) as Indicators of Heavy Metal Pollution PARASKEVA MICHAILOVA, NINEL PETROVA, GABRIELLA SELLA, STEFANO BOVERA, KEITH WHITE and LILIAN RARNELLA……………………………………………….…….235 The Polytene Chromosomes of Kiefferulus (Nilodorum) “species Yanuma” (Diptera: Chironomidae) SUMITRA SAXENA……………………………………………………………………………………………………….243

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TAXONOMY The Immature Stages of Chasmatonotus unimaculatus Loew (Diptera: Chironomidae: Orthocladiinae) with Notes on their Habitat MICHAEL J. BOLTON and RICHARD E. JACOBSEN………………………………………………………………255 A new species of Paratanytarsus Thienemann and Bause (Diptera: Chironomidae) with unusual larval and adult male morphology MICHAEL J. BOLTON, TORBJØRN EKREM, JAMES E. SUBLETTE and MARY F. SUBLETTE……………262 Description of the Immature Stages and Adult Female of Neostempellina reissi Caldwell (Diptera: Chironomidae) BROUGHTON A. CALDWELL, ROBERT W. BODE and ALEXANDER J. SMITH………………………………272 A New Genus From Bromeliads in Florida and Brazil (Diptera: Chironomidae: Orthocladiinae) J. H. EPLER……………………………………………………………………………………………………….……….285 Can Gonostylus Heel of Procladius (Holotanypus) be a Key Character to Identify Species? TADASHI KOBAYASHI…………………………………………………………………………………………………294 Two New Brazilian Species OF Axarus Roback, 1980 (Diptera: Chironomidae: Chironominae) HUMBERTO F. MENDES AND TROND ANDERSON……………………………………………………………….302 A New Genus of Orthocladiinae from Patagonia and South Chile (Diptera: Chironomidae) O. A. SÆTHER and T. ANDERSEN……………………………………………………………………………………311 The Female of Bethbilbeckia floridensis Fittkau, 1988 with A Review of the Genus (Diptera: Chironomidae) CHARLES N. WATSON, Jr………………………………...……………………………………………………………334

SPECIAL FEATURED CONTRIBUTIONS The History, Present Status and Future Prospects of Chironomidae Research in China XINHUA WANG, RUILEI ZHANG, YUHONG GUO, HONGQU TANG, ZHEN LIU and CHUNCAI YAN.….342 The Association of Chironomids and Vibrio cholerae (The First Three Years of Research) MEIR BROZA, MALKA HALPERN, HANAN GANCZ and YECHEZKEL KASHI………………………...………357 The General Bibliography of the Chironomidae (Diptera) ODWIN HOFFRICHTER………………………………………………………………………………………………….368

SYMPOSIUM PROGRAM………………………………………………………………………………….….371

Proceedings of the XV International Symposium on Chironomidae, pp. 45-54

Edited by Leonard C. Ferrington Jr. (2010)

The Production of Chironomids and Blackflies in a Subarctic River

GÍSLI MÁR GÍSLASON and ARNTHOR GARDARSSON Institute of Biology, University of Iceland, Askja, IS-101 Reykjavik.

ABSTRACT: In 1978-1985, in the River Laxá, N-Iceland, the production of Orthocladiinae,

the dominant subfamily of Chironomidae, was estimated by the average cohort method at three stations at 2, 6 and 24 km downstream from the outlet of Lake Mývatn. At two upstream

stations, population levels of aquatic insects have been monitored with window traps since

1977. Dominating Orthocladiinae species were: Eukiefferiella minor, E. claripennis, Orthocladius consobrinus and O. oblidens. The blackfly Simulium vittatum accounted for up

to 90% of all insects caught in the traps

Production of Chironomidae was 8-35 g AFDW m-2

y-1

, 5-47% of the combined production of chironomids and blackflies at the outlet of Lake Mývatn and 9-27 g AFDW m

-2y

-1, at the

sampling stations 5 and 24 km downstream. Production of S. vittatum was 27-599 g AFDW

m-2

y-1, 53-95% of the combined production at 2 km from the outlet, and 13-69 g AFDW m

-2y

-1,

or 43-86% of the production at the two other stations.

We suggest that populations of Chironomidae in the river are dependent on benthic algal production, which explains the relative stability in the populations over the past 26 years, in

comparison with the larval blackfly population, which feeds on drifting FPOM, and reflected

changes occurring in the phytoplankton production in Lake Mývatn.

INTRODUCTION

A critical step in understanding food webs and trophic dynamics of communities is qualifying the role of the primary consumers. Chironomidae tend to dominate in arctic and alpine regions (Petersen et

al., 1995) and most rivers in Iceland, except lake outlets (Gíslason et al., 1998), but relatively few

studies of annual production have been conducted. Chironomidae production is known from a few

rivers in the temperate region (see Armitage et al., 1995; Benke, 1998; Wright and Smock, 2001) and in the Norwegian highlands (Aagard et al., 1997).

The River Laxá, N-Iceland provides a good opportunity to study trophic relationships. Discharge measurements began in 1950 and other major physical and chemical variables have been monitored

since 1971 (Gíslason, 1994). Aquatic insects have been monitored from 1977 and waterfowl since

1975 (See Gíslason, 1994; Gardarsson and Einarsson, 2004). Discharge and nutrient input into the river is relatively stable from year to year. However, fine particulate organic matter (FPOM)

fluctuates on a year to year basis and the production of the blackfly Simulium vittatum Zett. has

shown up to an order of magnitude difference in minimum and maximum annual production

(Gíslason and Gardarsson, 1988). Year to year changes in the annual catch of brown trout (Salmo trutta L.) (Gíslason et al., 2002) and population dynamics of Barrow’s goldeneye (Bucephala

islandica (Gmelin)) and the harlequin duck (Histrionicus histrionicus (L.)) reflect changes in the

abundance of S. vittatum (Einarsson et al., in press).

The aim of this study is to evaluate the contribution of Chironomidae production to secondary

production in a subarctic lake outlet.

https://mail.lsit.ucsb.edu/horde/imp/view.php?mailbox=INBOX&index=3&array_index=4&id=2&actionID=113&mime=f50fc2818e9c1bc18693ff2aeaf41159#author1#author1

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SAMPLING SITES The Laxá is a lake-fed river in the volcanic zone of North Iceland (Figure 1). It flows over a bed of lava rock formed by a large eruption about 2300 years B.P. (Thórarinsson, 1979). River Laxá is the

outlet of L. Mývatn (65 35’N, 17 00’W), 278 m a.s.l., with mean flow of 33m3s

-1 (Figure 1). Rivers

Kráká and Sortulaekur add a further 7 m3s

-1 and 1 m

3s

-1, respectively, to the discharge near the outlet

(Ólafsson, 1979a; Rist, 1979). The discharge of the River Laxá is stable throughout the year and

almost no floods occur (Rist, 1979). The major ions remain stable through the year, due to the even subterranean flow of water into Lake Mývatn (Ólafsson, 1979b).

The sampling sites, Midkvísl, Helluvad and Thverá, were selected as representative of the 35

km long upper part of the river, above the

Laxargljúfur canyon, where current velocity and

waterfalls make the river impassable to migrating fish. However, the upper part has a

large landlocked stock of brown trout (Gíslason

et al., 2002), feeding on the benthic invertebrates (Steingrímsson and Gíslason,

2002). Midkvísl is one of three channels that

constitutes the outlet, Helluvad is 5 km below

the outlet and Thverá is 24 km downstream from the lake. The upper part of the river Laxá and its

animal communities are described by Gíslason

(1994).

METHODS

In 1978-80 and 1984-85, benthic samples were

taken 2-3 times a month from May to September and once in October and January. In 1977 and

1981-85, samples were taken monthly from May

to October and in 1982 once in January. Benthic samples were taken by removing lava rocks

from the bottom, holding a net (mesh size 70

m) downstream and collecting dislodged animals (Gíslason, 1985; Gíslason and

Gardarsson, 1988).

Figure 1. Map of Lake Mývatn and River Laxá.

Five rocks were examined from each collection. Each rock was outlined on graph paper in the same

position as it had on the bottom. The resulting area was used to calculate numbers and biomass per m2. In

addition to benthic samples, both qualitative and quantitative seston samples were taken. The processing

of benthic and seston samples have been described earlier (Gíslason, 1985).

Production of Chironomidae and S. vittatum were estimated by the size frequency method (Hynes and Coleman, 1968; Hamilton, 1969). S. vittatum larvae were grouped into 1 mm length classes to enable

separation of generations; 100-400 larvae in each length class were dried for 24 hours at 60 C and

weighed on an analytical balance. The larvae were incinerated for 80 minutes at 600 C and weighed again. The length of 30 Chironomidae larvae was measured, their diameter was measured at 4 points, near

their ends and at 1/3 and 2/3 of their lengths respectively. Their weight was estimated from their volume

and natural density (weight = .r

2.length

.1.05, where r is the mean radius of the larva and 1.05 its specific

47

gravity) and the ash free dry weight was estimated the same as for S. vittatum, 12.2% of wet weight

(Gíslason and Gardarsson, 1988). The relationship between ash free dry weight and length of Chironomidae larvae was y = 0.0056x

3.1898 (r= 0.974, p

48

The production of chironomid larvae and pupae was between 8 - 34 g AFDW m-2

y-1

at Midkvísl, 10 - 17 g

AFDW m-2

y-1

at Helluvad and Thverá (figure 4, Table 2). There were much greater fluctuations in blackfly production, ranging from 27 to 599 g AFDW m

-2y

-1 at Midkvísl and 12 - 90 g AFDW m

-2y

-1 at

Helluvad and Thverá. The turnover rate (P/B) for Chironomidae was 3.4-8.0 and 2.2 - 9.0 for S. vittatum

at all sampling sites (Table 2), indicating one and two life cycles per year among the dominant

chironomid species and S. vittatum.

Table 2. Biomass (g-afdw m-2

) and production (g-afdw m-2

y-1) of Chironomidae and S. vittatum

in the R. Laxá estimated with the size frequency method (Hynes and Coleman 1968) and

later modifications by Hamilton (1969). Data missing for Chironomidae at Midkvisl

and Helluvad from 1981-82 to 1983-84 and at Thverá from 1980-81 to 1984-85.

Study Year 78-79 79-80 80-81 81-82 82-83 83-84 84-85

Chironomidae

Midkvisl (outlet) P 26.7 23.3 7.6 --- --- --- 34.7

B 4.6 3.8 1.1 --- --- --- 4.3

P/B 5.8 6.2 6.6 --- --- --- 8.0

Helluvad (5 km) P 10.2 9.3 17.5 --- --- --- 12.7

B 2.2 2.5 2.4 --- --- --- 2.7

P/B 4.7 3.7 7.2 --- --- --- 4.8

Thvera (24 km) P 9.7 17.3 --- --- --- --- ---

B 2.9 3.0 --- --- --- --- ---

P/B 3.4 5.8 --- --- --- --- ---

Simulium vittatum

Midkvisl (outlet) P 53.2 27.2 100.6 57.1 54.4 51.3 599.0

B 15.2 9.8 19.3 10.9 20.2 23.1 66.6

P/B 3.5 2.8 5.2 5.3 2.7 2.2 9.0

Helluvad (5 km) P 21.1 12.5 13.2 21.2 21.2 18.9 79.6

B 4.5 3.2 2.5 4.2 13.6 6.5 22.0

P/B 4.7 3.9 5.3 5.0 1.6 2.9 3.6

Thvera (24 km) P 24.7 23.9 25.1 46.7 69.2 66.8 89.7

B 4.2 6.6 3.4 12.7 13.2 12.0 14.0

P/B 5.9 3.6 7.5 3.7 5.3 5.6 6.4

Window trap catches of Chironomidae were small at all stations from 1977 to 2001 and for the blackfly S.

vittatum it showed a considerable increase during 1984 and 1985 when the production of S. vittatum peaked (figure 5). No relationship was found between the chironomid production and window trap

catches of adults from the river (r = -0.351, n = 8), but correlation between the production of S.vittatum

and the subsequent number of adults from the same cohorts was highly significant (Gíslason and

Gardarsson, 1988).

49

DISCUSSION

The Chironomidae production of the River Laxá was between 8 and 35 g AFDW m-2

y-1, a production

range for moderate to high production in lotic habitats as defined by Armitage et al. (1995), where

extremely high production was above 32g DW m-2

y-1

(highest value known was 77 g DW m-2

y-1

). Annual

production of chironomids in a lowland stream in Denmark was estimated 13 g DW-2

y-1

(Lindegaard and

Mortensen, 1988). Similar values were reported for two lowland streams in Poland (Grzybkowska, 1989). Benke (1998) observed a similar range for the most productive genera of filtering collectors of

Chironomidae on snag surfaces in a Costal Plain river in south-eastern USA and the total production of

Chironomidae was 65 g DW m-2

y-1

. Total production of Chironomidae in the sediment of a headwater of a Coastal Plain river was 39-42 g DW m

-2y

-1 (Wright and Smock, 2001). However, the production in

Midkvisl (outlet)

Density (

nos m

-2)

0

50000

100000

150000

200000

250000

300000

1200000 Chironomidae

S. vittatum

Thvera (24 km)

1978 1979 1980 1981 1982 1983 1984 1985

Density (

nos m

-2)

0

50000

100000

150000

200000

250000

300000

1200000

Helluvad (5 km)

Density (

nos m

-2)

0

50000

100000

150000

200000

250000

300000

1200000

Figure 2. Densities of Chironomidae and S. vittatum larvae in the River Laxá.

50

Laxa was an order of magnitude larger than the macroinvertebrate production in a pristine Norwegian

highland stream (Aagaard et al., 2001). In the Laxá the production of Chironomidae was mainly by Orthocladiinae, the most common species were: Eukiefferiella minor (Edwards), E. claripennis

(Lundbeck), Orthocladius consobrinus (Holmgren) and O. oblidens (Walker) (Gíslason et al., 1995a, b).

Midkvisl (outlet)

Bio

ma

ss (

g a

fdw

m-2

)

0

10

20

3060

80Chironomidae

S. vittatum

Thvera (24 km)

78-79 79-80 80-81 81-82 82-83 83-84 84-85

Bio

ma

ss (

g a

fdw

m-2

)

0

10

20

3060

80

Helluvad (5 km)

Bio

ma

ss (

g a

fdw

m-2

)

0

10

20

3060

80

Figure 3. Biomass of Chironomidae and S. vittatum. Data missing for Chironomidae at

Midkvisl and Helluvad from 1981-82 to 1983-84 and at Thverá from 1980-81 to 1984-85.

Preliminary studies on the food of Chironomidae indicate that they were feeding on epilithic algae on the

river bottom (Gíslason, 1994). The food of S. vittatum larvae was drifting algae and detritus originating in

the Lake Mývatn (Gíslason and Jóhannsson, 1991). The population of the dominating benthic

51

invertebrate, the blackfly S. vittatum, reflects changes in Lake Mývatn. Production was significantly

associated with temperature, expressed as degree days, and FPOM (Gíslason and Gardarsson, 1988) and significant relationships are found between the summer cohort of S. vittatum and Anabaena flos-aquae

(Gíslason, 1994). Numbers of S. vittatum in the window traps were correlated with the production of the

corresponding generation (Gíslason and Gardarsson, 1988).

Midkvisl (outlet)P

rod

uctio

n (

g a

fdw

m-2

yr-

1)

0

25

50

75

100

600 ChironomidaeS. vittatum

Thvera (24 km)

78-79 79-80 80-81 81-82 82-83 83-84 84-85

Pro

du

ctio

n (

g a

fdw

m-2

yr-

1)

0

25

50

75

100

600

Helluvad (5 km)

Pro

du

ctio

n (

g a

fdw

m-2

yr-

1)

0

25

50

75

100

600

Figure 4. Production of Chironomidae and S. vittatum. Data missing for Chironomidae at Midkvisl and Helluvad from 1981-82 to 1983-84 and at Thverá from 1980-81 to 1984-85.

Chironomid production did not change much from year to year (figure 4). No relationship between chironomid production in the river and catches in the window traps (r = -0.351, n = 8) might indicate that

either the annual difference is so small that no relationship can be detected, or the small changes in

52

window trap catches and production observed in the chironomids compared with the blackflies may be of

more stochastic nature than changes in environmental parameters, especially food supply. No relationship was observed between the window trap catches of chironomids and blackflies (r=0.08, n=50). This

suggests that they do not share the same resources.

Population fluctuations of chironomids in the River Laxá and Lake Mývatn were not related, except for E. minor and O. consobrinus (Gardarsson et al., 2004). Changes in chironomid species were not related to

drifting FPOM, except for E. minor (p = 0.02) (Gardarsson et al., 1995). In Lake Mývatn, the dominant

chironomid species, Tanytarsus gracilentus (Holmgren), had population cycles of over four orders of magnitude driven by consumer-resource interactions (Einarsson et al., 2002). In the River Laxá, the

changes in total numbers of catches of chironomids were within one order of magnitude (figure 5).

Chironomidae

Num

ber

0

50000

100000

150000

Dragsey(outlet)

Helluvad (5km)

S. vittatum

19

76

19

78

19

80

19

82

19

84

19

86

19

88

19

90

19

92

19

94

19

96

19

98

20

00

20

02

20

04

Num

ber

0

100000

200000

300000

400000

Dragsey (outlet)

Helluvad (5 km)

Figure 5. Window trap catches of Chironomidae and S. vittatum at the outlet and at Helluvad (5 km downstream). Note that the scales on the y-axes are

not the same for Chironomidae and S. vittatum.

Although production of the Chironomidae is moderate to high compared with lotic habitats in the

temperate zone (Armitage et al., 1995) its importance in the food web depends on changes in S. vittatum

production, chironomids becoming relatively more important in years with low S. vittatum production. In the brown trout in 1992, chironomids were about 22% of the diet (Steingrímsson and Gíslason, 2002), or

53

half of their contribution to benthic densities. During periods of emergence of S. vittatum the proportion

of Chrionomidae increased, but at the same time the total volume of trout stomach contents decreased (Gíslason and Steingrímsson, 2004). The duckling production of harlequin duck and the numbers of

Barrow’s goldeneye responded to changes in S. vittatum numbers, but not numbers of Chironomidae

(Einarsson et al., 2006). Chironomid production in the River Laxá is high compared with rivers of similar

latitude, but S. vittatum plays a more significant role as food for vertebrate species in the River Laxá ecosystem than the Chironomidae. The role of chironomids as food for invertebrate predators is still not

understood and needs further study.

ACKNOWLEDGMENTS

We thank our colleagues at the Institute of Biology, University of Iceland for their support and advice during the study. We are especially indebted to Adalbjörg Erlendsdóttir, Dr. Kristín Bergsteinssdóttir,

Gudrún Lárusdóttir and Iris Hansen for doing the measurements and preparing the data on spreadsheets.

We thank Dr. Jón S. Ólafsson for drawing the final diagrams and Dr. Árni Einarsson for reading the

manuscript. The Mývatn Research Station provided logistics and support during field work. This study was financed by the Research Fund of the University of Iceland and the Icelandic Science Foundation.

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