Recent Evidence of Biological Recovery from Acidification in the Adirondacks (NY, USA): A Paleolimnological Investigation of Big Moose Lake Using Diatoms, Chrysophytes, and Cladocera

Kristina M. A. Arseneau1, Charles T. Driscoll2, Lindsay M. Brager1,3, Karen A. Ross1,4 and Brian F. Cumming1

The Adirondack region of New York (USA) has been significantly impacted by acid deposition. Since the implementation of the Clean Air Act Amendments, the area has shown improvements in water chemistry. However, little work has been done to assess biological recovery in the region. Assessing biological recovery is often difficult due to a lack of long-term monitoring data but paleolimnology can overcome this problem. Paleolimnology uses the physical and biological characteristics of lake sediments to infer lake histories. Biological proxies such as diatoms, chrysophytes, and cladocera can be correlated to environmental variables like pH and temperature. By quantifying changes in these proxies overtime, paleolimnologists can assess changes in the aquatic environment. Big Moose Lake is an intensively studied, acidified drainage lake located in the south-western part of Adirondack Park. Water chemistry measurements taken approximately once a month since 1982 show that the lake’s current pH is approaching its pre-industrial diatom-inferred pH of 5.8. The goal of this investigation was to see if biological recovery has followed chemical recovery in Big Moose Lake. Changes in the lake’s chrysophyte, diatom and cladocera fossil assemblages were analyzed from ca. 1760-present in a 34-cm isotopically dated sediment core. An analysis of similarities (ANOSIM) was used to examine shifts in species composition in the three species groups between two recent time periods: period 1 (1982-1992; mean pH=5.0) and period 2 (1997-2007; mean pH=5.4). ANOSIM showed a significant shift in species composition between periods 1 and 2 for diatoms and chrysophytes but not for cladocera. Both algal groups showed a recent shift from acid-tolerant to acid-sensitive species. However, the changes in diatom species composition were small, suggesting that the diatoms remain relatively unresponsive to increases in pH. Recovery is further advanced in the chrysophytes but a recent (ca. 1995) increase in the species Synura echinulata suggests that the group is not returning to its pre-disturbance state, likely due to climate warming. Cladocera remain unresponsive to increasing pH and several local/regional factors may be preventing their recovery (i.e. predation, calcium depletion, climate warming). This study demonstrates that biological recovery is underway in the Adirondacks but that recovered assemblages may not return to their pre-industrial state due to other environmental factors.

1 Paleoecological Environmental Assessment and Research Laboratory (PEARL), Dept. of Biology, Queen’s University, 116 Barrie St., Kingston, Ontario, Canada K7L 3N6 (email: ; tel: 613-533-6000 ext: 75161)
2 Center for Environmental Systems Engineering, Syracuse University, 151 Link Hall, Syracuse, New York, United States 13244
3 Dept. of Oceanography, Dalhousie University, Life Sciences Centre, 1355 Oxford Street, Halifax, Nova Scotia, Canada B3H 4J1
4 Dept. of Geography, University of Western Ontario, Room 2322, Social Sciences Centre, 1151 Richmond St. London, Ontario, Canada N6A 5C2