Research Projects in progress
Over the past 5 years I have been working with graduate and honours students investigating high resolution record of human impact on natural systems, primarily lakes. A few abstracts from recent conferences are below.
In the coming months (spring-summer 2013) I intend to continue work in Halifax Regional Municipality investigating anthropogenic impact on urban lakes, Ben Misiuk (ENVS Honours) will be the lead on this project. I will also be back in the Tantramar Marsh region working with Dr. Mark Mallory (Acadia Biology) and a variety of students on metal accumulation in constructed wetlands.
Further afield work continues in British Columbia on a variety of high resolution, multiproxy paleolimnological studies of short term environmental change in alpine lakes.
Work continues on the Bloody Creek impact crater with focus on the age of the feature and the possibility of multiple impact events.
Lead accumulation in open water wet ecosystems in the Border Marshes region, Nova Scotia – New Brunswick.
PATRICK ENGELHARDT, IAN SPOONER, MARK MALLORY, CHRISTINE MCLAUCHLAN AND NIC MCLELLAN
Open water wet ecosystems (OWWE) in the Border Marshes region (BMR) provide productive avian and invertebrate habitat. In the BMR lead (Pb) is a contaminant of interest due to potential bio-magnification and subsequent uptake by migratory waterfowl in OWWE. This study focuses on the relationships between constructed OWWE, productivity and lead accumulation. Eleven sites were selected to represent the spectrum of the OWWE environments in the BMR. Sites variability was determined by measuring salinity (0%- 2.83%), pH (6.6 - 9.1) and specific physical parameters. Variability at each site was defined through weekly determination of water pH, temperature, dissolved oxygen (DO), salinity and total dissolved solids (TDS). Top-of-core and bottom-of-core sediment samples were collected for each site and analyzed for loss on ignition (LOI), carbon-nitrogen ratios (C:N) and elemental concentrations of Pb and other environmental proxies (Ti, Fe, Mn) using X-ray fluorescence (XRF).
C:N – δ13C data indicates variable productivity (C:N 6.73 - 17.62) and that the organic sediment in all environments is dominantly autochthonous. Excavated sites had lower lead concentrations (0-14 ppm) in top-of-core sediment samples than non-excavated sites (>16 ppm). Bottom-of-core sediment samples exhibited highly variable lead concentrations (5-92 ppm) that reflect either natural lead sources (erosion of till) or the lack of an anthropogenic atmospheric source due to the pre-industrial age of the sediment. The variation in surficial sediment lead concentrations is likely due to a combination of factors including variable shoreline erosion, variable autochthonous productivity and, in some cases point source pollution. There was little evidence to indicate that lead sequestration correlates with salinity or pH. Results to date indicate recently excavated sites have higher autochthonous productivity and lower lead in surface sediments than either older excavated sites or natural OWWE.
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A Paleolimnological record of anthropogenic impact on water quality in First Lake, Lower Sackville, Nova Scotia
*DRAKE TYMSTRA1, IAN SPOONER1, and CHRIS WHITE2
1. Department of Earth and Environmental Sciences, Acadia University, 15 University Avenue, Wolfville, Nova Scotia B4P 2R6, Canada
112493t@acadiau.ca, Ian.Spooner@acadiau.ca
2. Nova Scotia Department of Natural Resources, 1701 Hollis Street, PO Box 698, Halifax, Nova Scotia, B3J 2T9, Canada whitece@gov.ns.ca
Lakes situated in urban environments are subject to a variety of anthropogenically induced pressures including nutrient loading, erosion, metal and salt inputs, and hypolimnetic anoxia. Since the 1920’s, First Lake in Lower Sackville, Nova Scotia has been the focus of watershed development and degradation of lake water quality is an ongoing concern. A time stratigraphic, multi-proxy, geochemical investigation was conducted on a sediment core from First Lake in order to determine pre- and post-development water quality conditions. A year-long study of limnological conditions, local weather conditions, and existing historical data was conducted in 2012. First Lake is 82 ha in size with a maximum depth of 23m. Survey results indicate shallow secchi depths (<2m), strong stratification (~6m) and neutral pH values (6.48-8.67). Oxygen-deprived bottom waters (<5%) commonly develop as the summer progresses. Water temperature trends indicate continual mixing in the epilimnion.
Atmospheric Pb concentrations found within the sediment core were used to approximate sedimentation rates. Pre-development (pre-1920) data indicates a mesotrophic lake that may have experienced occasional eutrophic conditions. Post-development proxy data indicates higher δ 15N values and lower C/N ratios indicative of increased primary productivity within the lake as a result of increased nutrient input from early agricultural development during the 1920’s. Changes in concentrations of Ti, Cu, K, loss-on-ignition and magnetic susceptibility values indicate landscape instability and increased sediment and toxin transfer into the lake associated with urbanization in the 1960’s. Collectively, these data indicate that though First Lake was a moderately productive lake before development, recent water quality degradation is strongly linked to specific anthropogenic activities in the watershed, an understanding of which is a fundamental factor in developing effective lake management strategies.
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The 11000 year record of environmental change from Pleasant River Fen, Nova Scotia, Canada: Impact on Blanding’s turtle population dynamics and habitat.
Ian Spooner, Bryan Martin, Tom Herman, Stephen Mockford, Brennan Caverhill, André Robichaud, David Mazzucchi, Susann Stolzeand Hilary White.
Pleasant River Fen is a 90 hectare wetland located in southwestern Nova Scotia that provides habitat for a small, disjunct, genetically distinct population of Blanding’s turtle (Emydoidea blandingii). The survival of this endangered species is thought to depend, in part, on the morphological stability of wetland environments. In this study we reconstruct the post-glacial evolution of Pleasant River Fen. Vibracoring was used to obtain an 11,000 year record of environmental change. A variety of stratigraphic proxies (LOI, MS, δ15N, aquatic and arboreal pollen, spores and macrofossils) were used to understand how regional climate variability and basin evolution affected the physical structure of the wetland.
Proxy analyses indicated that Pleasant River Fen experienced fundamental physical change in response to known climate change elucidated from regional pollen records. The site persisted as a moderately productive shallow lake from deglaciation (> 12000 cal. BP) until about 1500 cal. BP. Blanding’s turtles likely first colonized the region at about 8000 cal. BP. An increase in clastic input and change in the autochthonous floral assemblage at 3000 cal. BP is consistent with the regional arboreal record that indicates the onset of Neoglacial cool moist climate. Sediment stratigraphy and aquatic pollen indicate the transition from lake to fen occurred at about 1500 cal. BP. An increase in local herbaceous pollen and two prominent charcoal beds at ca. 1000-700 cal. BP indicate significant fire events, more arid conditions, and the periodic establishment of a grassland environment. Drying was followed ca. 700 cal. BP by an increase in hydrophilic fauna consistent with increased moisture, persistent flooding and Little Ice Age-equivalent cooling. From 300 BP onwards lithostratigraphic variability was likely related to human activity (fire, water level management) in the region.
The apparent persistence of Blanding’s turtles in Pleasant River Fen throughout the late Holocene suggests that they are resilient to habitat changes associated with natural wetland succession, climate change and human activity. It is likely that other environmental stresses such as habitat fragmentation and anthropogenic land use may exert a stronger influence on population dynamics.