To examine the influence of diet and age on organochlorine contaminant (OC) concentrations in two closely related ringed seal ( Phoca hispida ) populations enantiomeric fractions (EFs) of chiral contaminants and stable isotopes of nitrogen (δ 15 N) and carbon (δ 13 C) were measured along with OCs in ringed seals collected from the east and west side of the Northwater Polynya. Seals from these two locations were feeding at the same trophic level based on δ 15 N values in muscle but had slightly different sources of carbon based on δ 13 C measurements in muscle. After removing the influence of age, sex, and blubber thickness, OC concentrations did not vary between ringed seals from the east and west side of the polynya. ΣPCB, ΣDDT, and Σchlordane were found to increase with age for both male and female seals. The inclusion of older (>20 years) female seals, which may have a reduced reproductive effort, may influence the relationships in females. Stable isotopes failed to describe OC concentrations in ringed seals suggesting that diet was not a major factor in variation of OC concentrations within this ringed seal population. Cis - and trans -chlordane, oxychlordane, and heptachlor epoxide were all nonracemic in the ringed seal blubber but did not vary with age, sex, or collection site. α-HCH appeared racemic (enantiomeric fraction = 0.50 ± 0.01) in the seals, although this EF is different than those previously observed in their prey species, and was found to vary significantly with age. EF values in the ringed seals varied considerably from other Arctic marine mammals and seabirds, providing addition evidence that the type(s) and characteristic(s) of the enzymes involved in biotransformation of chiral OCs vary between these organisms.

1. The impact of whole‐lake lime (slaked lime, Ca(OH)2, and/or calcite, CaCO3) addition on plankton communities was evaluated in eutrophic hardwater lakes on the North American Boreal Plain.2. Two lakes received a single treatment of lime (Ca(OH)2 at 74 or 107 mg L–1), two lakes received multiple treatments with Ca(OH)2 and/or CaCO3 (5–78 mg L–1), and four lakes were untreated and served as reference systems.3. Over the long‐term (> 1 year), phytoplankton biomass was reduced in multiple‐dose lakes, but not in single‐dose lakes. Cyanobacteria typically dominated the algal community in the years before, during and after lime treatment in both single‐ and multiple‐dose lakes.4. In the single‐dose lakes, randomized intervention analysis showed no significant change in the biomass of zooplankton after lime addition.

1. Aquatic macrophytes are abundant in ponds and canals that are constructed in semi‐arid regions for water storage and conveyance, as well as in lakes that are culturally enriched.2. Addition of Ca(OH)2 to two hardwater ponds at 250 or 275 mg L–1 caused an immediate eradication of submersed aquatic plants. Although these ponds are well‐buffered (alkalinity: 2.57–3.94 mequiv L–1; pH: 8.1–9.0), lime addition caused an immediate increase in pH of 0.2–3 units.3. Application of 135 mg L–1 Ca(OH)2 for 24 h or 210 mg L–1 Ca(OH)2 for 65 h to two irrigation canals had no effect on macrophyte biomass at the lower concentration and duration, but resulted in the elimination of aquatic macrophytes 1 month after the higher concentration, longer duration treatment.4. Unlike the macrophyte control achieved following application of 210–275 mg L–1 Ca(OH)2 to ponds or canals, microcosm experiments in which lime formulation [slaked lime (Ca(OH)2), calcite (CaCO3), or a 1 : 1 mixture] and concentrations (up to 1500 mg L–1) were manipulated failed to elicit a consistent change in macrophyte biomass. Macrophytes in microcosms treated for the short‐term (23–33 days) with ≥ 200 mg L–1 Ca(OH)2 or a mixed Ca(OH)2/CaCO3 formulation always lost pigmentation, but biomass was not consistently reduced.5. Declines in macrophyte biomass following treatment of ponds and canals may have been triggered by a short‐term rise in pH which, in these relatively warm (22–23 °C) alkaline (2.28–3.94 mequiv L–1) systems, would have resulted in low concentrations of free CO2 and bicarbonate for photosynthesis.