USING GOOGLE EARTH TO SHARE SEDIMENT DATA WITH STAKEHOLDERS IN THE BELGRADE LAKES WATERSHED, CENTRAL MAINE, USA

Analysis of bottom samples collected from Great Pond, central Maine, USA, were used to create a sediment map of the lake basin in regards to depth, grain-size distribution, total organic content (TOC), C:N ratios and phosphorus and metal concentration. Great Pond has the largest surface area (3,453 ha) of the 7 lakes in the watershed. Most of its water comes from East and North Ponds via Great Meadow Stream, as well as the surrounding uplands and groundwater. Lake volume was increased by the construction of a hydroelectric dam in 1886.

To evaluate natural and anthropogenic changes in the lake environment, 67 samples were collected. Multiple sedimentologic and geochemical proxies were used to infer in-lake ecological responses. Grain-size was used to determine sediment source and indicates a predominance of silt and clay-sized sediment related to the underlying glacio-marine Presumpscot Formation. Other samples contain sand and pebble-sized sediments related to esker and outwash sources. Google Earth placemarks were created for the sample sites and include histograms and ternary diagrams for both gravel, sand and mud and sand, silt and clay for easy observation. A lake bottom map was created and shows the relationship to nearby surficial glacial features. The sediment map and Google Earth placemarks will be housed on a local website for viewing and use by stakeholders and the scientific community.

C:N ratios were calculated to detemine the source of organic matter in the sediment. Values ranged between 8-11 and indicated a nonvascular plant (algal) origin for the organic matter.

Future analyses of these sediments will include total organic carbon (TOC) to evaluate biomass productivity. Sediments will also be analyzed for phosphorus, aluminum, iron and other metals to determine further anthropogenic impact on the system.

This research will add to the geologic knowledge base of lake sedimentation and chemistry which can be used by local conservation groups for community education and advocacy for best sustainability practices. Results will aid in the understanding of the glacial formation of the lake, distribution of sediment within, and human impact on the lake. Additionally, knowing the distribution of phosphorus and metals within the sediments may allow development of a strategy to avoid accelerated eutrophication.