Assessing long-term changes in chironomid assemblages linked to past fluctuations in Leach’s Storm-Petrel populations on islands in the Western Atlantic Ocean
Authors
Lim, Joeline
Date
Type
thesis
Language
eng
Keyword
Paleolimnology , Seabird , Conservation , Population dynamics , Chitin degradation , Chironomus spp.
Alternative Title
Abstract
Nutrient loading is an important factor that can indirectly deplete dissolved oxygen concentrations in lakes. In environments where seabirds nest and breed, guano is a prominent source of nutrients that can eutrophy waterbodies. Such external nutrient inputs may deplete bottom-water oxygen, resulting in shifts in bottom-water invertebrate communities that are sensitive to changes in oxygen. Chironomidae (non-biting midges) can be used as paleolimnological indicators to infer changes in past oxygen conditions due to their sensitivity to oxygen concentration, excellent preservation in sediments and abundance. I assessed the long-term changes in subfossil chironomid assemblages linked to reconstructed changes in the seabird colony size of the Leach’s Storm-Petrel in ponds located off the Canadian East coast on Baccalieu Island, Newfoundland, and Grand Colombier Island, Saint Pierre and Miquelon, France, to qualitatively reconstruct past changes in dissolved oxygen conditions, and thereby indirectly infer changes in colony size. Ornithological surveys indicate declines in the Leach’s Storm-Petrel colony in Newfoundland since the 1980s, whereas the colony in Saint Pierre and Miquelon is believed to be stable or increasing, albeit based on limited observational data. Using dated sediment cores from seabird-impacted lakes, I isolated chironomid head capsules, taxonomically identified them to the genus level, and determined their abundance and diversity. Using the chironomid assemblages, I qualitatively inferred lake oxygen conditions over the past ~1700 and ~5700 years on Baccalieu Island and Grand Colombier Island, respectively. Furthermore, I investigated if the timing of changes in chironomid-inferred oxygen coincided with known occurrences of seabird-derived inputs in the lakes’ catchments, as determined by surveys and other paleolimnological proxies. The chironomid data provides novel information on past oxygen levels in the lakes. In both sites, chironomid assemblages indirectly tracked past changes in the storm-petrel colony size, and their more recent declines. These data, alongside several paleolimnological proxies, will be used to determine the long-term natural variability and dynamics of Leach’s Storm-Petrel populations. This research provides data required to implement informed conservation and management strategies. Moreover, understanding the background conditions and responses of lakes to nutrient loading provides insights on the effects and tolerance of lakes to disturbance.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.