Regional climate changes drive increased scaled-chrysophyte abundance in lakes downwind of Athabasca Oil Sands nitrogen emissions

Abstract

Several limnological and paleolimnological investigations have linked enhanced atmospheric nitrogen (N) deposition to nutrient enrichment and potentially increased primary production. The Athabasca Oil Sands Region (AOSR) in northeast Alberta is a significant regional source of N emissions, particularly since development intensified during the 1990's, and recent paleolimnological investigations have provided some evidence of increased lake production in the AOSR. However, the AOSR has also experienced atmospheric warming and hydrological change since ca 1900 AD, and therefore the relative effects of nutrient deposition and climatic mechanisms on lake production remain unclear. To address this problem, a factorial-designed paleolimnological assessment of 16 lakes in northwest Saskatchewan was undertaken to quantify changes in abundance and species composition of scaled chrysophytes over the past 100 years. Study sites included both N-limited and P-limited lakes within control regions as well as those receiving enhanced N deposition from the AOSR. We hypothesized that a change in algal communities within N-limited AOSR-impacted lakes, without concurrent changes in the other lake groups, would suggest AOSR-derived N as a driver of enhanced primary production. Instead, recent and marked increases in concentrations of scaled chrysophytes (mainly Mallomonas crassisquama) occurred in the recent sediments in cores from all four lake groups (N v. P limited, impacted v. control), suggesting that regional climate changes rather than N deposition was the paramount process enhancing chrysophyte production. However, because chrysophyte abundances tended to be higher in deep, lower pH lakes, and chrysophyte time series were fit best by lake-specific generalized additive models (GAMs), we infer that climate effects may have additionally been meditated by catchment and/or lake-specific processes.

Taxon-specific variation in δ13C and δ15N of subfossil invertebrate remains: Insights into historical trophodynamics in lake food-webs

“…Although speculative, such conclusion is in agreement with other paleolimnological proxies from the same sediment cores (i.e., molar C: N ratios of SOM, diatom assemblages, scaledchrysophytes and cladoceran composition), which indicated only limited industrial impacts (Hesjedal 2017;Laird et al 2017;Mushet et al 2017). (Dunn, 1964).…”

Effects of water levels on species diversity of silica-scaled chrysophytes in large tributaries of Lake Baikal

“…Additionally, the climatic changes recorded worldwide during the previous decades, including the Baikal Region, may also underscore the quantitative and qualitative development of silica-scaled chrysophytes (Shimaraev et al 2002;Sinyukovich et al 2010;Sorokovikova et al 2015). Global climate change influences the hydrology of waterbodies (Mushet et al 2017) that will significantly impact the development of aquatic organisms. The interchange of floods and low water levels created various environmental conditions (Table 1) and stimulated dynamics of the ecosystem allow the formation of a "hotspot" for silica-scaled chrysophytes diversity.…”

Estimates of exceedances of critical loads for acidifying deposition in Alberta and Saskatchewan

“…where T is the temperature in degrees Celsius (NEG-ECP, 2001;Nasr et al, 2010;Whitfield et al, 2010;Aherne, 2011). The resulting critical load values were referenced to the corresponding GIS polygons under the SLC containing that soil type, resulting in a Canada-wide map of forest soil critical loads for acidity.…”