Amenity value of water resources has become a major driving force of recent population growth in the region centered on Coeur d’Alene Lake in northern Idaho, USA. Despite regulatory measures aimed to protect lake water quality, surface water quality is increasingly threatened by lakefront development and invasions of Eurasian watermilfoil (Myriophyllum spicatum), a non-indigenous aquatic plant species. We used hedonic modeling to estimate the effects of ambient water quality and the presence of Eurasian watermilfoil on lakefront property values of single-family homes in the Coeur d´Alene area. We find that property values are positively associated with Secchi depth (a proxy of water quality or clarity), and negatively related to the presence of watermilfoil. Results of spatial regime analysis indicate the geographical variations of these associations. The presence of watermilfoil was related to a 13% decline in mean property value, corresponding to $64,255 USD, on average, lower property sales price. Our study demonstrates that proactive mitigation approaches to cope with potential environmental degradation in lake ecosystems could have significant economic benefits to owners of lakefront properties and local communities.

The oxidation state of sulfur [S] is a primary control on mobility of metals in sediments impacted by legacy mining practices. Coeur d’Alene Lake of northern Idaho, USA, has been impacted by upstream legacy mining practices that deposited an estimated 75 Mt of metal(loid)- and S-rich sediments into the lake. Future lake conditions are expected to include algal blooms, which may alter S and metal remobilization during the seasonal euxinic environment. Cores of the lake sediments were exposed to anoxic and anoxic + algal detritus conditions for eight weeks at 4.5 °C through introduction of a N₂ atmosphere and addition of algal detritus. At a location 2.5 cm below the sediment-water interface, anoxic conditions promoted a shift in S species to continually larger concentrations of reduced species and an associated shift in the bonding environment reflective of increased S–metal bonds. Anoxic + algal detritus conditions suppressed the increasing trend of reduced S species and induced greater release of Mn compared to the anoxic-only conditions but did not appear to enhance the release of As, Cd, or Fe. The addition of algal detritus to the sediment-water interface of these Fe- and S-rich sediments enhanced mobilization of Mn likely because of dissimilatory metal reduction where the anaerobic oxidation of the algal detritus stimulated Mn reduction. Results of the study indicate that future metal release from the lake sediments will be altered with the likely deposition of algal detritus, but the effect may not enhance the release of acutely toxic metals, such as As or Cd, or substantially impact Fe cycling in the sediments.

Burnet SH, Wilhelm FM. 2021. Estimates of internal loading of phosphorus in a western US reservoir using 3 methods. Lake Reserv Manage. 37:261–274. We used 3 methods to estimate internal loading of total and dissolved phosphorus (TP/DP) in 2 years in a stratified eutrophic western US reservoir with high internal loading of phosphorus. We calculated the internal load from (i) net increases of TP/DP from reservoir water column samples, (ii) gross TP mass balances, and (iii) gross TP/DP loading estimated from laboratory-incubated sediment cores and the anoxic reservoir area. We also present a cost comparison and spreadsheet to allow managers to estimate costs for each method. The highest internal loads were estimated in 2015 from the net in situ samples (999 mg/m²/yr) and the gross annual mass balance (850 mg/m²/yr). Gross estimates from sediment cores were 1.2× higher in 2015 than in 2014 due to differences in anoxic area resulting from a drought and record reservoir drawdown. Costs were highest for the mass balance method and lowest for the sediment core method. Given the small monetary difference between the sediment core and in situ methods, we suggest managers obtain in situ data to estimate internal loading because this yields a net estimate most reflective of whole-lake dynamics. Our data provide an important benchmark of internal loading in a human-made reservoir given the general paucity of such estimates in this large geographic region.

The mobility of a metal in mining-impacted sediments is determined by the environmental conditions that influence the metal’s oxidation state and bonding environment. Coeur d’Alene Lake, USA, has been impacted by legacy mining practices that allowed the hydrologic transport of mining waste to the lakebed, resulting in substantial amounts of redox-sensitive Fe and Mn along with Ag, As, Cd, Cu, Hg, Pb, Sb, and Zn. Future lake conditions may include algal blooms and additional algal detritus at the sediment–water interface, which may alter Fe and Mn forms that can influence their, and other metal(loid)s, mobility during seasonal anoxia. Cores of the lakebed sediments were exposed to anoxic and anoxic + algal detritus conditions for 8 weeks. Sediment samples were collected biweekly for analysis of Fe and Mn oxidation states and bonding environments by synchrotron-based X-ray absorption spectroscopy. Over the 8-week period and at a location 12.5 cm deep in the sediments, anoxic and anoxic + algae conditions produced limited changes in Fe and Mn oxidation states and bonding environments. At a location 2.5 cm below the sediment–water interface, the anoxic condition promoted a relatively stable environment in which Fe and Mn oxidation states and bonding environments did not vary greatly during the experiment. At the 2.5 cm depth, the anoxic + algae condition substantially altered the Mn oxidation state distribution and bonding environment, but this condition did not strongly influence the Fe oxidation state distribution or bonding environment. The anoxic + algae condition increased the presence of Mn³⁺, produced Mn⁴⁺ at select times, altered the Mn bonding environment, and temporarily increased the release of Mn into porewater. The algae influence on sediment and porewater Mn likely occurred because of the increased formation of organo-Mn complexes produced during algae-enhanced enzymatic processes. The lack of influence of algal detritus on sediment and porewater Fe and the formation of soluble organo-Mn complexes may limit the potential increase in the mobility of other metal(loid)s with future lake conditions.