The Great Lakes have been the focus of extensive environmental research, but recent data on the aquatic concentrations of emerging compounds, such as flame retardants, are scarce. Water samples from 18 stations on the five Great Lakes were collected in 2011 and 2012 using XAD-2 resin adsorption and analyzed for PCBs, organochlorine pesticides, PAHs, polybrominated diphenyl ethers (PBDEs), and emerging flame retardants, including organophosphate flame retardants (OPEs). Total PCB concentrations ranged from 117 ± 18 pg/L in Lake Superior to 623 ± 113 pg/L in Lake Ontario. Among the organochlorine pesticides, the most abundant was dieldrin, with the highest average concentration of 99 ± 26 pg/L in Lake Erie, followed by p,p'-DDD with an average concentration of 37 ± 8 pg/L in Lake Ontario. Total PAH concentrations were higher in Lakes Erie and Ontario than in Lakes Michigan, Huron, and Superior. Total PBDE concentrations were highest in Lake Ontario (227 ± 75 pg/L), and the most abundant congeners were BDE-47, BDE-99, and BDE-209. Total OPE concentrations ranged between 7.3 ± 4.5 ng/L in Lake Huron to 96 ± 43 ng/L in Lake Erie.

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Based primarily on data collected over the past four decades by Environment Canada, long-term trends of eutrophication-related variables are developed for the offshore waters of the Laurentian Great Lakes. Trends of spring concentration are reported for the major nutrient species: phosphorus [total phosphorus (TP), and soluble reactive phosphorus (SRP)]; nitrogen [total oxidized nitrogen (NO 3 1 NO 2 ), and ammonia nitrogen (NH 3 )]; and silica [soluble reactive silica (SiO 2 )]. Summer trends of surface chlorophyll a and Secchi depth are developed as indicators of lake trophic response. The results show that phosphorus has declined significantly in all the lakes, whereas nitrogen and silica have both increased. Along with documenting the

Abstract. The surface-atmospheric exchange of CO2 and CH 4 was measured continuously using the flux gradient approach from a beaver pond in the northern study area of the Boreal Ecosystem-Atmosphere Study between May 22 and September 19, 1994. The beaver pond was a large source of CO2 and CH 4 for the entire study period.

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