The objectives of this study were to (i) assess the variation in relative abundance of lake sturgeon (Acipenser fulvescens Rafinesque, 1817) subjected to various man-induced stresses and physical characteristics at a landscape scale across Ontario; and (ii) ascertain the factors that explain the variability observed among rivers using a multivariate approach. A standardized index netting program targeting juvenile and adult Lake Sturgeon was conducted over two field seasons at 22 river sites across Ontario. Each river had unique or different human-induced stresses and physical characteristics. Relative abundance of Lake Sturgeon varied in river across the Ontario landscape. A principal component analysis was conducted using site physical characteristics with the associated anthropogenic stressors. The catch-per-unit-effort (CPUE) for juvenile and adult Lake Sturgeon were then regressed with the scores of principal components having eigenvalues >1. The variation observed was best explained by the negative relationship observed between CPUE and the presence of hydroelectric generating stations. Historical commercial fisheries also had an effect on Lake Sturgeon abundance whereas subsistence fisheries seemed to focus on rivers that were not regulated and where Lake Sturgeon numbers were greater. Research and recovery efforts should focus on minimizing the impact of hydroelectric generation on Lake Sturgeon while achieving socioeconomic goals. U.S.

The presence of hydroelectric power generating facilities has been identified as the primary factor affecting the variation in relative abundance of Lake Sturgeon Acipenser fulvescens in rivers across Ontario. Qualitatively, these facilities are known to have impacts on the aquatic environment, and they can be inferred to have effects on Lake Sturgeon; however, few studies quantifying these effects are available. Our objectives were to (1) determine and compare the magnitude of effect (d) of hydroelectric facility operating regimes on Lake Sturgeon abundance;(2) compare Lake Sturgeon biological responses among river systems with different operating regimes in order to understand the potential limiting factors within these systems; and (3) assess the effectiveness of mitigation efforts where they have been employed. A standardized index netting program targeting juveniles and adults was conducted over two field seasons at 23 river sites across Ontario. The magnitude of effect on abundance (as indicated by d) was lowest in run-of-the-river systems and was considered large in peaking systems and winter reservoir systems. Relative abundance was significantly greater in unregulated rivers than in regulated rivers. Juvenile abundance was significantly greater in run-of-the-river systems than in peaking systems and winter reservoirs and was significantly greater in peaking systems than in winter reservoirs. Adult abundance did not significantly differ among operating regimes. Growth was faster and condition was significantly greater in unregulated systems than in regulated systems. Recruitment of Lake Sturgeon was highly variable in both regulated and unregulated systems, whereas recruitment failure was more evident in regulated systems, particularly in peaking systems.

Bulk precipitation samples were collected weekly at Turrialba, Costa Rica, from March 1979 through March 1981 and analyzed for pH, conductivity, major cations and anions, nutrient (N and P) species, and 12 trace metals. Results indicated that Costa Rican precipitation contains relatively low levels of acidity, nutrients, and minerals. For example, during the precipitation years March 1979 to March 1980 and April 1980 to April 1981, volume‐weighted mean specific conductances were 4.88 and 4.82 μS/cm, respectively. Precipitation pH values ranged from 4.81 to 6.35 and the volume‐weighted mean pH was 5.34 over the 2‐year study. On the basis of equivalent ratios, excess [SO42−] was found to be the principal acidic anion, with only small possible contributions from excess [Cl−] or NO3−. Marine‐ derived aerosol accounted for virtually all of the Na+, Mg2− and Cl− deposited in Turrialba rain and was a minor contributor (3–15%) to the K+, Ca2+, and SO42− loadings. Excess [SO42−] comprised 85% of the total SO42− and may arise in Costa Rican precipitation due to long‐range transport, biogenic sources, or local volcanic emissions. Highest concentrations of minerals and nutrients were observed during the low rainfall period of early spring, which coincided with increased agricultural activities. Very low levels of trace metals were observed in the precipitation.

Chemical analyses of wet-only and bulk precipitation collected from June 1976 to July 1977 indicate that rain is the predominant deposition mechanism for SO42-, NH4"1", NO3-, Mg2+, and K+, but dry fallout is of comparable importance to rainfall for deposition of Na+, Cl-, and Ca2+. Heavy metal levels (especially Zn) were highly variable in both types of samples. The (volume-weighted) average concentrations of total nitrogen, NH4"1", and NO3-in bulk precipitation were 0.82, 0.12, and 0.23 mg of N/L, respectively. Averages for orthoand total phosphate were 24 and 85 Mg of P/L, respectively, in bulk precipitation and 19 and 34 pg/h in wet-only samples. Highest nutrient concentrations occurred in spring and early summer. Total loadings of N and P from bulk precipitation (1.15 g of N and 0.12 g of P/(m2-year)) are above permissible rates (relative to eutrophication) for shallow lakes.

The acidity of rainfall in Florida has increased markedly in the past 25 years, and the average sulfate and nitrate concentrations have increased by factors of 1.6 and 4.5, respectively, over the period. Annual average pH values below 4.7 now occur over the northern three quarters of the state. Summer rainfall has average pH values 0.2 to 0.3 unit lower than winter rainfall, and sulfate concentrations at most sites are higher in summer. The annual deposition of H(+) (about 300 to 500 equivalents per hectare) in northern Florida is a third to a half of the deposition in the heavily impacted northeastern United States; comparable figures for excess sulfate (derived from sulfur dioxide) are 7 to 11 kilograms of sulfur per hectare or 50 to 90 percent of the sulfate deposition rates at Hubbard Brook, New Hampshire.