Latitudinal variation in ecological opportunity and intraspecific competition indicates differences in niche variability and diet specialization of Arctic marine predators

Individual specialization (IS), where individuals within populations irrespective of age, sex, and body size are either specialized or generalized in terms of resource use, has implications on ecological niches and food web structure. Niche size and degree of IS of near-top trophic-level marine predators have been little studied in polar regions or with latitude. We quantified the largescale latitudinal variation of population- and individual-level niche size and IS in ringed seals (Pusa hispida) and beluga whales (Delphinapterus leucas) using stable carbon and nitrogen isotope analysis on 379 paired ringed seal liver and muscle samples and 124 paired beluga skin and muscle samples from eight locations ranging from the low to high Arctic. We characterized both withinand between-individual variation in predator niche size at each location as well as accounting for spatial differences in the isotopic ranges of potential prey. Total isotopic niche width (TINW) for populations of ringed seals and beluga decreased with increasing latitude. Higher TINW values were associated with greater ecological opportunity (i.e., prey diversity) in the prey fish community which mainly consists of Capelin (Mallotus villosus) and Sand lance (Ammodytes sp.) at lower latitudes and Arctic cod (Boreogadus saida) at high latitudes. In beluga, their dietary consistency between tissues also known as the within-individual component (WIC) increased in a near 1:1 ratio with TINW (slope = 0.84), suggesting dietary generalization, whereas the slope (0.18) of WIC relative to TINW in ringed seals indicated a high degree of individual specialization in ringed seal populations with higher TINWs. Our findings highlight the differences in TINW and level of IS for ringed seals and beluga relative to latitude as a likely response to large-scale spatial variation in ecological opportunity, suggesting species-specific variation in dietary plasticity to spatial differences in prey resources and environmental conditions in a rapidly changing ecosystem

Data from: Recent Warming, Rather than Industrial Emissions of Bioavailable Nutrients, is the Dominant Driver of Lake Primary Production Shifts across the Athabasca Oil Sands Region

Freshwaters in the Athabasca Oil Sands Region (AOSR) are vulnerable to the atmospheric emissions and land disturbances caused by the local oil sands industry; however, they are also affected by climate change. Recent observations of increases in aquatic primary production near the main development area have prompted questions about the principal drivers of these limnological changes. Is the enhanced primary production due to deposition of nutrients (nitrogen and phosphorus) from local industry or from recent climatic changes? Here, we use downcore, spectrally-inferred chlorophyll-a (VRS-chla) profiles (including diagenetic products) from 23 limnologically-diverse lakes with undisturbed catchments to characterize the pattern of primary production increases in the AOSR. Our aim is to better understand the relative roles of the local oil sands industry versus climate change in driving aquatic primary production trends. Nutrient deposition maps, generated using geostatistical interpolations of spring-time snowpack measurements from a grid pattern across the AOSR, demonstrate patterns of elevated total phosphorus, total nitrogen, and bioavailable nitrogen deposition around the main area of industrial activity. However, this pattern is not observed for bioavailable phosphorus. Our paleolimnological findings demonstrate consistently greater VRS-chla concentrations compared to pre-oil sands development levels, regardless of morphological and limnological characteristics, landscape position, bioavailable nutrient deposition, and dibenzothiophene (DBT)-inferred industrial impacts. Furthermore, breakpoint analyses on VRS-chla concentrations across a gradient of DBT-inferred industrial impact show limited evidence of a contemporaneous change among lakes. Despite the contribution of bioavailable nitrogen to the landscape from industrial activities, we find no consistency in the spatial pattern and timing of VRS-chla shifts with an industrial fertilizing signal. Instead, significant positive correlations were observed between VRS-chla and annual and seasonal temperatures. Our findings suggest warmer air temperatures and likely decreased ice covers are important drivers of enhanced aquatic primary production across the AOSR

Spring Melt and the Redistribution of Organochlorine Pesticides in the Sea-Ice Environment: A Comparative Study between Arctic and Antarctic Regions

Complementary sampling of air, snow, sea-ice, and seawater for a range of organochlorine pesticides (OCPs) was undertaken through the early stages of respective spring sea-ice melting at coastal sites in northeast Greenland and eastern Antarctica to investigate OCP concentrations and redistribution during this time. Mean concentrations in seawater, sea-ice and snow were generally greater at the Arctic site. For example, α-HCH was found to have the largest concentrations of all analytes in Arctic seawater and sea-ice meltwater samples (224–253 and 34.7–48.2 pg·L^–1 respectively compared to 1.0–1.3 and <0.63 pg·L^–1 respectively for Antarctic samples). Differences in atmospheric samples were generally not as pronounced however. Findings suggest that sea-ice OCP burdens originate from both snow and seawater. The distribution profile between seawater and sea-ice showed a compound-dependency for Arctic samples not evident with those from the Antarctic, possibly due to full submersion of sea-ice at the former. Seasonal sea-ice melt processes may alter the exchange rates of selected OCPs between air and seawater, but are not expected to reverse their direction, which fugacity modeling indicates is volatilisation in the Arctic and net deposition in the Antarctic. These predictions are consistent with the limited current observations

Nutrient (TN, DIN, TP, TDP, SRP) data from snowpack samples in the Athabasca Oil Sands Region, Alberta, Canada

Nutrient (TN, DIN, TP, TDP, SRP) data from snowpack samples in the Athabasca Oil Sands Region, Alberta, Canad