Nicole Furlan Thesis Defense: Project Description
Title: Life Histories, Diets and Secondary Production of Odonata along a Temperature Gradient on the Copper River Delta, Alaska
Southcentral Alaska’s Copper River Delta (CRD) is the largest contiguous coastal wetland on the west coast of North America, representing a vital network of aquatic and terrestrial habitats as well as a wealth of wildlife and fisheries resources. Coastal topography drives cold air masses from Alaska’s Interior through the Copper River Canyon and these masses have a disproportionate impact on the east side of the delta. The resulting east-west temperature gradient provides an ideal backdrop for testing the effects of contrasting temperature regimes on aquatic insect communities in CRD ponds, in which dragonflies (Odonata: Epiprocta) and damselflies (Odonata: Zygoptera) are often apex predators.
To compare odonate life histories, secondary production and diets as influenced by different temperature regimes, eight ponds were chosen from the east and west sides of the delta, divided evenly between two contrasting landscape types: outwash plain (OP) and uplifted marsh (UM). Water temperatures were coldest in OP ponds on the west delta and warmest in UM ponds on the west delta. Growing degree days (GDD) accumulated most rapidly in west UM ponds (16.4 GDD/day) and least rapidly in west OP ponds (12.1 GDD/day). Five families of odonate taxa were collected and Enallagma boreale (Coenagrionidae) was the numerically dominant odonate taxon in 10 of the 16 sampled ponds, comprising 48.5% of all odonates collected during the study. Leucorrhinia hudsonica (Libellulidae) and Aeshna juncea (Aeshnidae) comprised 36.6% and 10.4% of collected odonates, respectively. Odonate densities were higher in west delta ponds than in east delta ponds, and 70.3% of the odonates collected over the course of the study were taken from UM ponds on the west delta. There were no significant differences in A. juncea or E. boreale densities or secondary production between pond types, but L. hudsonica densities and secondary production were significantly higher (p<0.001) in west delta UM ponds than in any other pond type.
A. juncea diets were highly variable on a temporal scale. A. juncea diets in west OP ponds were dominated by low-quality prey such as ostracods (Ostracoda), water mites (Hydrachnidae), and water boatmen (Corixidae). Midge larvae (Chironomidae) dominated A. juncea diets in all other pond types, occurring in 68% of foreguts. A. juncea diets containing E. boreale and L. hudsonica demonstrated intraguild predation, and cannibalism was evident in 6% of foreguts. Foreguts containing threespine stickleback (Gasterosteus aculeatus) revealed A. juncea’s apex predator role in CRD ponds. The phenology of odonate emergence was not assessed due to insufficient numbers of collected exuviae, but it is likely that odonate emergence happens earliest in UM ponds on the west delta due to rapid degree day accumulation and high densities of prey items for consumption. This study may provide valuable insights into the potential impacts of climate change on coastal wetland ecosystems, especially the role of odonates as food resources for avian taxa that nest and breed on the CRD.
Although a thesis credits only one author, this work represents the contributions and support of countless individuals, institutions, and funding agencies. First and foremost, I owe immense gratitude to Dr. Martin Berg for tirelessly providing insight, mentorship, and a healthy sense of humor. I am incredibly lucky to have worked with him for so long, and to have had the opportunity to spend my field season on Alaska's Copper River Delta. I doubt that I will ever visit another place as beautiful as the delta, and it will always hold a place in my heart. Additionally, it's often easy to lose oneself in the minutiae of research, but my committee members have always helped to reinforce the importance of perspective. Thank you to Dr. Timothy Hoellein and Dr. John Kelly for asking the difficult questions; I am a stronger researcher for it.
To Chantel Caldwell: thank you for your hard work in the field and your excellent company in the lab. This project would have been a whole lot longer and much less fun without you. I would also like to thank Emily Campbell for her willingness to donate time and energy to this study, and for her love of the delta.
Thank you to Conrad and Sarah Zack for their continual support and friendship. There are few people who are kinder or more generous than Conrad and Sarah, and I am lucky to know them.
The United States Forest Service was indispensable to this study and provided transportation, logistical support, sampling assistance, and funding. Special thanks to Luca Adelfio, Erin Copper, Jason Fode, Ken Hodges, Tim Joyce, Deyna Kuntzsch, and Sean Meade for squeezing this research into an already busy summer field season. Additional funding was also provided by the National Fish and Wildlife Federation.
Finally, Thank you to Gordon Reeves for his deep commitment to all aspects of research on the Copper River Delta.
The author, Nicole Furlan, received her Bachelor of Science degree in Biology from Loyola University Chicago, Chicago, IL in 2008. Following graduation, she worked as a Research Technician for Dr. Martin Berg and entered the Master's program in Biology at Loyola University Chicago in 2010. She completed her Master of Science degree in Biology in 2014
Dr. Martin Berg
Dr. Timothy Hoellein
Dr. John Kelly