11 ka

605 cal BP

5 064 cal BP

10 355 cal BP

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6 ka

7 ka

8 ka

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ANTHROPOGENIC CHANGE

WIDESPREAD FIRES

ACKNOWLEDGMENTS

INTRODUCTION

Figure 1. Long Lake is located 6 km northeast of Amherst, Nova Scotia, in theCumberland Basin marshes.

Figure 2. Long Lake viewed from the west side of the lake. Long Lake issurrounded by till (north) and floating bog (south).

FORMING A LAKE

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REFERENCES

MATERIALS & METHODS

Figure4. Percussion cores (a) and gravitycores (b) were collected from Long Lake.

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Figure 3. Bathymetry (left) and sub-bottom profile of Long Lake (right).

Figure 9. Paleogeographic reconstructions of Atlantic Canada at 13 ka (left) and 10 ka (right). At 13 ka,the Chignecto Isthmus was either ice-covered or flooded. By 10 ka relative sea level at the CumberlandBasin marshes was the same as modern datum. Modified from Shaw et al. (2002). Arrow indicateslocation of Long Lake.

SALINE INFLUENCE?

0 30.0020.0010.00 60.0050.0040.00-34.00

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13 C

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Figure 8. Geochemical data. Red dots indicate fireevents, blue dots indicate marine incursions.

13Figure 7. Biplot of C vs C/N ratio. The data indicate that organic matter in corePC2 was freshwater aquatic and/or terrestrial. Modified from Mackie et al. (2007).

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15Figure 6. Detailed plot of Hg, Pb and between 20 and 70 cm. Increases areconcurrent centred at a depth of 50 cm.

N

Figure 5. Maps of the Cumberland Basin marshes by (a) Ganong (1903) and (b) Trueman (1899) showingthe drainage modifications by the Missiguash Marsh Company (A) and Judge William A.D. Morse (B).Airphotograph (c) still shows evidence of the Missiguash Marsh Company drainage route.

CONCLUSIONS

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Halifax

Study Area

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50 km

Sediment distrubiton and bathymetry (Fig. 3) were assessed by sub-bottom profiling using a Hydrobox 33 khz transducer. Coring sites were selected based on bathymetry and intrabasin sediment distrubution to obtain the longest undisturbed record possible. Two percussion cores were collected using a portable coring platform (Fig. 4a). Percussion core PC2 was selected as a representative sample for analysis. Gravity cores (Fig. 4b) were collected for high-resolution analysis on recent environmental change at Long Lake. Cores were transported to Acadia Univesity, split, sub-sampled, and analyzed for metals (XRF), mercury, and C/N stable isotopes.

This study was funded by NSERC, Ducks Unlimited Canada, Irving Oi, and Acadia University. Special thanks to the staff at Ducks Unlimited Canada, Amherst office, for logistical support and accommodations through the Beaubassin field station. The Beaubassin Research Centre, located in Aulac, New Brunswick, is a partnership between Acadia University, Irving Oil Ltd. and DUC and is used extensively for ecological research. It is the focal area in Atlantic Canada for scientific research on wetlands and waterfowl. Special thanks to the Nova Scotia Department of Natural Resources for use of the desktop XRF instrument. We thank C. Nixon for reviewing the poster and improving the quality of the science.

Long Lake, is a small, shallow lake located 12 km inland from the head of the Bay of Fundy in the Amherst Marsh area of Nova Scotia (Figs. 1, 2) and is about 7 m above mean sea level (msl). It is part of a large coastal wetland system termed the Cumberland Basin marshes (CBM) in the New Brunswick - Nova Scotia border region. The marshes are located along the Atlantic migratory flyway and are particularly important for waterfowl and marshbird production, providing both migration and breeding habitat. Though ecosystem integrity has been studied extensively, there are no records of the physical and chemical evolution of lakes in the CBM. In this study we use a paleolimnological method at Long Lake to construct a 10 000 year record of both natural and anthropogenically influenced change.

Nova Scotia Department of Natural ResourcesGeoscience and Mines Branch

Natural Resources

Halifax, Nova ScotiaMarch 2015

Open File Illustration ME 2015-001Starting in the 1800s, the practice of ‘tidings’ was common. In this process, landowners would dig canals from tidal rivers into wetland lakes, converting bog into productive farmland (Figs. 5a, b). First the lake would be drained of freshwater, then the tide admitted to fill the lake basin with sediment. In the mid 1800s, Long Lake was drained, but tidal water never reached the lake. Instead, water level lowering and wave scour resulted in a distinct contact between Unit 2 and Unit 3 (Fig 3). Sedimentation in the past 150 years was mostly inorganic and had moderately high concentrations of Pb (up to 40 ppm), likely from atmospheric deposition or naturally occurring lead remobilized by recreational activity or wave activity.

15Increases in Pb, Hg and N in the core centred at 5 500 cal. BP (Fig. 6) are likely the consequence of regional fires, and indicate that a significant reservoir of these metals exists in the natural environment. Increases in Hg have been observed following wildfires and associated storm runoff (Garcia

15and Carnigan, 1999; Caldwell et al., 2000), in addition to increases in N (Spencer et al., 2003). The fire events are broadly coincident with a period of warming that may have also been a period of low precipitation in Atlantic Canada (Mott et al., 2009; Spooner et al., 2014). Wetter conditions and a raised water table have persisted at the site since 4000 cal. BP, likely as a result of changing climate conditions and rapid salt marsh aggradation in response to sea-level rise (Shaw and Ceman, 1999).

Two separate increases in Cl occur at ~8 ka and ~10 ka (Fig. 8) and likely represent saline incursion into Long Lake. C/N and stable isotopes (Fig. 7), however, indicate that a community of brackish or marine primary producers was never established and the incursions were short-lived. Cl could also originate from older marine sediment that may exist upstream of Long Lake as sea level was ~10 m below modern datum by 8 ka.

Long Lake may be one of the oldest lakes in the Cumberland Basin marshes. Unit 1 is a poorly sorted beach/active drainage deposit interpreted to be marine in origin, whereas Unit 2 is an organic-rich lacustrine sediment. The contact between units 1 and 2 occurs ca. 11 500 cal BP, a time when relative sea level was falling in the region (Fig. 9; Shaw et al., 2002). Relative sea level at this time was ~20 m above modern datum (Fig. 10; Amos and Zaitlin, 1985). The contact between units 1 and 2 likely represents the point at which relative sea level was low enough for a freshwater environment to become established. At the base of a core from Round Lake (2 km north at an elevation of 9 m above msl) a possible marine clay is overlain by fresh water deposits (Dunnington, 2011). This observation is consistent with the presence of a sustained marine environment in a location where a freshwater environment has dominated since ~11 ka. Other lakes in the Cumberland Basin marshes have basal ages of 3000-4000 cal BP (e.g., Shaw et al., 2010), coincident with a time of rapid salt marsh aggradation in response to sea-level rise (Ganong, 1903; White, 2012; Shaw and Ceman, 1999).

Figure 10. (Top-left) Idealized section of the Cumberland Basin marshes from Ganong (1903). Long Lake is situated in a basin underlain by till (upland) at the landward end of the marsh (A). (Bottom-left) Relative sea level change at Cumberland Basin, Bay of Fundy. Modified from Amos and Zaitlin (1985).

The formation of Long Lake is coincident with the emergence of the Chignecto Isthmus and falling relative sea level about 12 ka. Marine incursions may have occurred after this time but were short-lived events.

Increased concentrations of Pb and Hg at about 5.5 ka are evidence of widespread fire event(s) during a time of regional drying. Increased concentrations of these metals may also represent a source for the bioaccumulation of Pb and Hg. In the last 300 years, anthropogenic activity has fundementally altered the hydrology of Long Lake.

A 10 000 year record of environmental change at Long Lake, Cumberland

Marshes, Nova Scotia-New Brunswick border region, Canada

Dewey Dunnington, Hilary White, Ian Spooner,Chris White, Nelson O'driscoll, and Nic Mclellan

Poster presentation at the Society 41st Colloquium and Annual General Meeting, Mount Allison University, Sackville, New Brunswick, January 30-31, 2015.

2015 Atlantic Geoscience

Amos, C.L. and Zaitlin, B.A. 1985: The effect of changes in tidal range on a sublittoral macrotidal sequence, Bay of Fundy, Canada; Geo-Marine Letters, v. 4, p. 161-169.Caldwell, C.A., Canavan, C.M. and Bloom, N.S. 2000: Potential effects of forest fire and storm flow on total mercury and methylmercury in sediments of an arid-lands reservoir; Science of The Total Environment, v. 260, p. 125-133.Dunnington, D.W. 2011: Using paleolimnological methods to track late Holocene environ- mental change at Long Lake, New Brunswick - Nova Scotia Border Region, Canada; Unpublished B.Sc.H. thesis, Acadia University, Wolfville, Nova Scotia, 83 p.Ganong, W.F. 1903: The Vegetation of the Bay of Fundy Salt and Diked Marshes: an Ecological Study; Botanical Gazette, v. 36, no. 6, p. 429-455.Garcia, E. and Carignan, R. 1999: Impact of wildfire and clear-cutting in the boreal forest on methyl mercury in zooplankton; Canadian Journal of Fisheries and Aquatic Sciences, v. 56, p. 339-345.Mackie, E.A.V., Lloyd, J.M., Leng, M.J., Bentley, M.J and Arrowsmith, C. 2007: Assessment

13 of C and C/N ratios in bulk organic matter as palaeosalinity indicators in Holocene and Late glacial isolation basin sediments, northwest Scotland; Journal of Quaternary Science, v. 22, p. 579-591.Mott, R.J., Walker, I.R., Palmer, S.L. and Lavoie, M. 2009: A late-glacial - Holocene palaeo- ecological record from Pye Lake on the eastern shore of Nova Scotia; Canada Geological Survey of Canada Contribution 20080395. Canadian Journal of Earth Sciences, v. 46, p. 637-650.Shaw, J., Amos, C.L., Greenberg, D.A., O'Reilly, C.T., Parrott, D.R. and Patton, E. 2010: Catastrophic tidal expansion in the Bay of Fundy, Canadian Journal of Earth Sciences, v. 47, p. 1079-1091.Shaw, J. and Ceman, J. 1999: Salt-marsh aggradation in response to late-Holocene sea- level rise at Amherst Point, Nova Scotia, Canada; The Holocene, v. 9, p. 439-451.Shaw, J., Gareau, P. and Courtney, R.C. 2002: Palaeogeography of Atlantic Canada 13- 0kyr; Quaternary Science Reviews, v. 21, p. 1861-1878.Spencer, C.N., Gabel, K.O. and Hauer, F.R. 2003: Wildfire effects on stream food webs and nutrient dynamics in Glacier National Park, USA; Forest Ecology and Management, v. 178, p. 141-153.Spooner, I., Stolze, S., Martin, B., Robichaud, A., Herman, T., Mockford, S., Caverhill, B., Mazzucchi, D., and White, H. 2014: A 10,000-Year Record of Environmental Change from Blanding's Turtle (Emydoidea Blandingii) Habitat at Pleasant River Fen, Nova Scotia, Canada; Wetlands, v. 34, p. 1145-1158.Trueman, G.J. 1899: The Marsh and Lake Region at the Head of Chignecto Bay; Bulletin of the Natural History Society of New Brunswick, v. 14, p. 93-104.White, H.E. 2012: Paleolimnological records of post-glacial lake and wetland evolution from the Isthmus of Chignecto region, eastern Canada. M.Sc. Thesis, Acadia University, Wolfville, Nova Scotia, 131 p.

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