SPATIAL AND TEMPORAL VARIABILITY IN A HYPORHEIC ZONE: A HIERARCHY OF CONTROLS FROM WATER FLOWS TO MEIOFAUNA Richard Goodwin Storey A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy, Graduate Department of Zoology, in the University of Toronto O Copyright by Richard Goodwin Storey 2001 National Library Bibliothèque nationale du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. rue Wellingbn O(tawa ON K1A ON4 OmwaON K1AW Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence aliowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or seIl reproduire, prêter, distribuer ou copies of this thesis in microfoxm, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/film, de reproduction sur papier ou sur fomat électronique. The author retains ownership of the L'auteur conserve la propriété du copy~@~tin &is thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom 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 pemiission. autorisation. SPATIAL AND TEMPORAL VARIABILITY IN A HYPORHEIC ZONE: A HlERARCHY OF CONTROLS FROM WATER FLOWS TO MEIOFAUNA By Richard Goodwin Storey A thesis submitted in conformity with the requirernents for the degree of Doctor of Philosophy, Graduate Department of Zoology in the University of Toronto, 200 1. Abstract The hyporheic zone beneath a single 10 m-long riffle of a gravel-bed strearn was sampled intensively between August 1996 and Novernber 2000. The overall aims were to identiQ the factors controlling surface-subsurface exchange flows, biogeochemical processes and meiofaunal distributions in the hyporheic zone, and to quantifi the effects of hyporheic processes on inorganic nitrogen and dissolved organic carbon (DOC) concentrations in the stream. From among a large number of factors suggested by other authors, three key factors were identified that together wntrol surface-subsurface exchange flows: the hydraulic conductivity of the alluvial sediments, the hydraulic gradient between upstream and downstrearn ends of the riffie, and the discharge flux of ground water into the alluviurn. Each of these factors changes with season, causing a reversal of subsurface hydraulic gradients and a great reduction in exchange flows during fa11 to spnng. A wide variety of aerobic and anaerobic microbial processes was fond to occur in the hyporheic zone. Although oxygen inhibits anaerobic processes, denitrification, femous iron reduction and sulphate reduction al1 occur in oxygenated sediments, probably because sediment biofilms create anaerobic microenvironments. Therefore, denitrification is controlled more strongly by nitrate concentration than by oxygen at this site. The hyporheic zone at this site is a sink of DOC and inorganic nitrogen, in contrast to many streams. Loss of inorganic nitrogen at this site is a result of slow subsurface flow rates, rapid oxygen uptake and high surface water nitrate concentrations, which together favour denitrification. This supports the current thmry that seeks to explain when and where the hyporheic zone will be a source or si& of inorganic nitrogen. At this site, however, only 0.01-0.2% of surface water discharge is exchanged with the subsurface along the 10 m nffle, indicating that removal of surface water nitrogen by hyporheic exchange is negligible in this Stream. Abundance and taon richness of meiofauna are controlled primai1y b y depth. Physicochernical parameters associated with surface water control distributions to a lesser extent, but measures of available food, such as particulate organic matter, and abundance and activity of sediment-bound bacteria, show no correlation with any measure of the meiofaunal cornmunity. Aekmowledgements First and foremost 1 would like to thank my supervisor, Dr. Dudley Williams, who has been tremendously encouraging and supportive throughout this whole process, and believed in my abilities more than 1 did myself. 1 also thank my two thesis cornmittee members, Dr. Roberta Fulthorpe and Dr. Ken Howard, who have constantly challenged me to think more clearly and have provided very valuable perspectives on the work. With field work and lab work, more people have helped me than 1 cm name, but special thanks to those who were willing to venture out repeatedly, even in sub-zero temperatures and peak mosquito season: Marilyn Smith, Katarina Magnusson, Lucie Sliva and Lama Desantis. Many thanks, too to those who spent long hours Ming through sediment samples in search of dismembered bugs: Lama, Lucie, Amie, Bobby Fokidis, Emily Chan and Jasmine Sufi. Several people have provided technical expertise without which this thesis would not have been possible. Thanks to Bill Mark and Robert Drimmie at University of Waterloo Environmental Isotope Laboratories for generously providing use of, and help with, their mass spectrometer; Ron Hofmann at University of Toronto Dept. of Environmental Engineering for analysing many DOC sarnples; Danny and Bill in the U. of T. at Scarborough workshops, for the many weird and wonderfil devices they made; and Dan Mathers at U. of T. ANALEST laboratories for help with the ion chromatography. Thanks also to Rick Gerber, Brewster Conant Jr., Steve Holysh and E. J. Wexler for technical advice on cornputer modelling. Special thanks to the MacKenzie family for allowing us free access to their property, and to Tara and Emma, two enthusiastic individuals who were always glad to see us and only rarely ran off with something valuable. This research was funded through a Natural Sciences and Engineeering Research Council of Canada (NSERC) gant to Dudley Williams. To my parents, Rae and Jack: thank you for introducing me to the amazing world around me and teaching me to explore it. Thank you for being my cheering tearn, even fiom the other side of the world. 1 could not have finished this thesis without the prayers of an extraordinary group of people at St. Ninian's Anglican church, especially Terry McQuiston, Lynne Root, Gloria Hall, Lynda Chantson, Jeff and Erin Biggs and Vivian Campbell - my fmily in Christ. And to God, who has seen the way through the many twisty tumy roads, and has taught me to be glad in al1 of them, 1 give my thanks and praise - al1 of the above are expressions of Wis love. Table of contents .. Abstract.................................................................................................................................... 11 Ackaowledgernents..................................................................................... iv ... List of tables .......................................................................................................................... vil1 List of figures ........................................................................................................................... ix Thesis introduction.................................................................................................................. 1 Definition and importance of the hyporheic zone ............................................ 1 Current research directions .................................................................... -5 Thesis objectives ................................................................................ -8 Approach ......................................................................................... -9 Outline............................................................................................ -9 References....................................................................................... Il Chapter 1: Perspectives and predictions on the rnicrobial ecology of the hyporheic zone Abstract ........................................................................................................................ 15 Introduction.................................................................................................................. 16 Bacterial types and processes possible in the hyporheic zone ..................................... 17 Fungi ........................................................................................................................... -24 Biofilms: making the story more complex ................................................................... 25 Spatial distributions.................................................................................................... -26 New technologies......................................................................................................... 28 Conclusions................................................................................................................. -30 References.................................................................................................................... 32 Chapter 2: Interactions arnong hydrology, water chemistry and meiofauna in the hyporheic zone: fine scale patterns and seasonal changes................................................. 38 Abstract ........................................................................................................................ 39 Introduction................................................................................................................. -39 Site..............................................................................................................................