Temporal and Spatial Comparison of Mercury Bioaccumulation in the Lower Trophic Levels of a Post-glacial Lake Food Web.

Total mercury (Hg) concentrations and carbon (δ13C) and nitrogen (δ15N) stable isotopes were quantified among aquatic invertebrate and sediment samples collected from Keuka Lake in New York's Finger Lakes region to evaluate temporal and spatial variability in Hg bioaccumulation and trophic ecology among these lower trophic levels. Hg concentrations ranged from 6.3 to 158.8 ng/g (dry wt) across dreissenid mussel, zooplankton, and juvenile (< 10 mm) and adult (≥ 10 mm) mysid shrimp (Mysis diluviana) samples. Hg concentrations were higher in samples collected from the western basin in 2015 relative to those for samples collected from this basin in 2022 (p < 0.001). While no specific mechanisms could be identified to explain this difference, higher δ15N values for zooplankton collected in 2015 support conclusions regarding the role of zooplankton trophic status on Hg concentrations in these populations. Spatial patterns in Hg concentrations were of generally low variability among samples collected from the lake's east, west and south basins in 2022. Trophic positions as inferred by δ15N were represented by adult mysids > juvenile mysids > large zooplankton (≥ 500 µm) > dreissenid mussels ≥ small zooplankton (64-500 µm). Differences were evident among the regression slopes describing the relationships between sample Hg concentrations and δ15N values across the lake's three basins (p = 0.028). However, this was primarily attributed to high δ15N values measured in dreissenid mussels collected from the south basin in 2022. Biota sediment accumulation factors ranged from 0.2 to 2.3 and were highest for adult M. diluviana but mysid δ13C values generally supported a pelagic pathway of Hg exposure relative to benthic sediments. Overall, these results provide additional support regarding the contributions of lower trophic levels to Hg biomagnification in aquatic food-webs.

Interplay between personality and antisocial peer affiliation as prospective predictors of marijuana use and academic achievement in the transition into and out of college.

Marijuana use has increased in recent cohorts and is associated with several negative outcomes, including poorer academic achievement. Less is known about how personality and peer factors in the first two years of college work together to predict problematic marijuana use and potentially co-occurring academic problems three years later. The longitudinal College Experiences Study (N = 209) was used to address this (N = 209, ~90% white, ~40% male); this study collected data from students in their first year of college, as well as ~1 year later (retention = 85%), and again ~4 years after the initial data collection (retention = 80%). Longitudinal data were analyzed via the traditional cross-lagged panel (CLPM) and the random-intercept CLPM approach. Results were consistent in that there was strong stability in problematic marijuana use, constraint, and antisocial peer affiliation across time, which were predominately influenced by stable, trait-like influences. These factors were also highly correlated but there was less evidence that one predicted the other over time. Nonetheless, greater constraint at Wave 1 was associated with significantly greater cumulative GPA in the transition out of college (ßs = 0.43-0.44). Results support the importance of early prevention and intervention of problematic marijuana use, as well as the possibility of using personality-targeted approaches in the first year of college to promote growth in behaviors related to constraint (e.g., staying organized, risk avoidant) in an effort to improve academic success and correlated substance use outcomes by the transition out of college.