O Copyright by Brian Milakovic, 1999

INVERTEBRATE POPULATIONS OF INTACT AND DEGRADED AREAS OF A SUPRA-TIDAL MARSH AT LA PÉROUSE BAY, MANITOBA Brian Milakovic A thesis submitted in conformity with the requirements for tbe degree of MASTER OF SCIENCE Graduate Department of Botany University of Toronto O Copyright by Brian Milakovic, 1999 National Library Bibliothwue nationale of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395, rue Weüington OnawaON KIAW OnawaON KtAON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Libray of Canada to Bibliothèque nationale du Canada de reproduce, loan, distniute or sel1 reproduire, prêter, distniuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/tilm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts kom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Collections of aquatic invertebrates were made from 70 vemal ponds hm degraded and intact areas in the supra-tidal marsh at La Pérouse Bay on different occasions between June and early August 1996, and 12 of those ponds were resampled intensively between June and early July 1997. Benthic macroinvertebrate assemblages showed changes in the representation of certain groups. Midge larvae (Diptera: Chironomidae) were the most abundant organisms in ponds with numbers appioaching 25,000 individuals/m2. The aquatic invertebrate collections made from the vernal ponds indicated a loss of species richness in ponds in degraded ateas. Collections of terrestrial invertebrates based on the use of piddl traps were made on a weekly bais in the same areas fiom which aquatic arthropods were collected between June and late August 1997. Spiders (Araneae) and certain beetles (Coleoptera) dominated intact swds whereas shore bugs (Hemiptera: Saldidae), as well as microfauna nich as springtails (Collembola), dorninated degraded areas. 1 wish to thank the senior scientists of the La Pérouse Bay branch of the Hudson Bay Project, Dr. R.L. Jefferies. h. K.F. Abraham, and Dr. R.F. Rockwell, for establishing and maintaining a superior standard for ecological research in the north. Because of them, 1 had the opportunity to explore an "intellectual playground" that other 'kids' do not get to dirty themselves in. Thanks to Dr. Hélène Cyr, Dr. Chns Darling, Dr. T.J. Carleton, and Dr. K.F. Abraham, my esteemed committee, for the hours of grilling and general discussions that went a long way to improving the quality of this study. Hélène, the the in your lab confirmed my interest in ecology.. .the long hard hours, and the fun.. .littie did 1 know it would serve as a fitting prerequisite to this endeavor. And thanks to Ms. Deborah Tarn, Mr. Henry Frania, and Mr. Brad Hubley for their help and technical assistance. Special thanks to my extended farnily ... my fnends and lab mates Tanya Handa and Esther Chang for their fiiendship and support duhg two of the most challenging and exciting surnmers of my life, and for their smiles and encouragement during the intervening months. .. Chris Witte for his camaraderie, for happily sharing his time and knowledge, and for al1 his tremendous help. Mucb of this work could not have been accomplished without the hard work and dedication of great field assistants. .. Elizabeth Gold and Leslie Gold And of course the rest of the Hudson Bay team made rny northem experience one I'll not soon forget ... Ashana Mellor, Paul Matulonis, Curt Vacek, Diana Pollak. And certaidy my family at home ... my siblings, David and Lillian, and my parents (who never ceased to encourage, help, and yes, give a good kick in the rear when needed) and ali the uncles, auais, and cousins... dso, dearest Christine (such patience), Martin, Rex, Tracy, Darlene.. .ail who asked, "&en7 t you done yet !?" Yes I am. Fiaally, special thanks again to "Dr. Boô" for his guidance, generosity, support, and patience during al1 stages of this study... and to his red pen for "teaching me to wxite". This research was fiuided by a NSERC gant awarded to RL. Jefferies, and a University of Toronto Open Felîowship. Contents 13 Invertebrates in an Arctic Environment. ..............................m...m..mm.13 1.3.1 The Arctic En~ironrnent......~................... ..m000e0m00000000m000m013 1.3.2 The Ttopbic Relationsbip of Invertebrates ..........................17 133 lavertebntes at La Phuse Bay.. .... ..................................19 Chapter III: Tenestdril Inverlebrutes 97 3.3 Resulb.............. ............. ............ ..... ........... ................ .......111 3.3.1 Environmental Variables. ................. .... ................ m....m..lll 3.3.2 Ground Fauna........ ........... ..... ...... ............. ..m.m.....m......124 a. Statistia.. .. ..... .. .. ....l 24 b. R~~OOS~Sof Invertebrate G~OU~S.....................127 Chapter FC Future Directions for Reseatch 178 Figure 3.1. Aerial photograpbs of the three areas from which both aquatic and terrestrial hpodswae wllected ......................................................104 Figure 3.2 . Design of the sampling grid utilized to collect terresmial arthropods........ 105 Figure 3.3. Photographs of pantraps ............................................................ 106 Figure 3.4. Percent water content of mils in the three sample areas ....................... 113 Figure 3.5. Soil temperature profiles of the supra-tidal matshes, June 25, 1997......... 116 Figure 3.6. Soü temperature profiles of the supra-tidal marshes, July 18, 1997......... 117 Figure 3.7. Soi1 temperature profiles of the supra-tidal marsheq August 17, 1997 ...... 119 Figure 3.8. Albedo, and the amount of radiation reaching the ground surface in the three sample areas ...................................................................... 122 Figure 3.9. Pantrap counts for spiders .......................................................... 129 Figure 3.10. Pantrap wunts for ground mites ................................................. 131 Figure 3.1 1. Pantrap counts for springtai1s.................................................... 134 Figure 3.12. Pantrap counts for ground Mes............................................... 137 Figure 3.13. Pantrap counts for carrion beetles ............................................... 140 Figure 3.14. Pantrap wunts for variegated mud-loving beetles ............................143 Figure 3.15. Pantrap counts for tiger beeties .................................................. 145 Figure 3 .16 . Pantrap counts for shore bugs ................................................... 148 Figure 4.1. Mechanisms modulating top-ciown and bottom-up forces in food chains ... 164 Figure 4.2. Factors influencing population dynamics and cornmunity structure in natural systems........................................................................... 165 Figure 4.3. Schematic representations of the structure of "food weô" relationships between taxa wrveyed from vernal ponds in the three sampling areas .. 169 Figure 4.4. Schematic representations of the structure of "food web" relationships ôetween the arthropod grouad fauna surveyed fiom terrestrial habitats in the thra sampling anas ........................................................ 173 vii L Ovemew. 1.1 Introduction Many species of Arctic breeding geese have increased substantiaily in number over the past three decades, including lesser snow geese (Amer caemlescens caerulescens), greater snow geese (A. c. atlontica), Ross' geese (A. rossii), and greater white-fionted geese (A. albrfrons) (Abraham and JeEeries, 1997). The mid-continent population of lesser snow geese, of which the La Pbrouse Bay colony (Fig. 1.1) is a component, now ambers over 5 million birds and the population continues to increase at a rate of about 5% to 7% per year (Abraham et ai., 19%). Both natural and agicultural ecosystems have ken significantly alter& by the intense foraging activities of populations of some of these geese species (Jeffenes, 1988a,b; Kerbes et ai., IWO). Most geese feed in fiocks on migration and on the wintenng grounds. Many, including lesser snow geese, feed in groups on the breeding grounds following hatch. The combination of high numbers of geese, the$ colonial behavior, and locally hi@ densities cm result in substantid shih in plant assemblages and habitat structure over the. The long-term effeets of disturf,ance by geese on different vegetation types and soils are cumulative (Abraham and Jefferies, 1997). Females display a high degree of philopatry to breeding grounds (Cooke et al., 1995) and in response to overall population growth, nesting colonies expand outward within existing suitable habitats (Kerbes, 1994). The sustained use of a breeding site over the long term allows littie opportunity for recovery of the vegetation from the effects of foraging (Abraham and Jeffenes, 1997). The intensity of foraging each year depends on the number of birds and the weather conditions. In late HUDSON BAY Figure 1.1. Map of La Pérouse Bay, Manitoba and the coastal zone. The positions of La Pérouse Bay and Churchill on the Hudson Bay Coast are indicated

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