On the integration of ecological and physiological variables in polar bear toxicology research: a systematic review

Abstract

Ecotoxicology evolved as a scientific field as awareness of the unintended effects of anthropogenic pollutants in biota increased. Polar bears (Ursus maritimus) are often the focus of Arctic contaminant exposure studies because they are apex predators with high contaminant loads. While early studies focused on describing and quantifying pollutants, present-day polar bear toxicological papers often incorporate ecological variables. This systematic literature review investigates the ecological and physiological variables that have been integrated in such studies. The systematic literature search resulted in 207 papers, published between 1970 and 2016. Representation of each of the 19 polar bear subpopulations varied from 0 to 72 papers; East Greenland, Barents Sea, Southern Beaufort Sea, and Lancaster Sound had the most published research, with over 30 papers each. Samples were collected between 1881 and 2015, primarily from harvested bears (66%); most from the 1990s and 2000s. Adipose tissue, liver, and blood were the most common tissues examined, and mean number of bears analyzed per paper was 76 (range 1–691). Papers investigating temporal trends did so using a mean sample of 61 bears over a 6-year period.The frequency with which ecological and physiological variables were integrated into toxicological papers varied. Age and (or) sex was the only ecological variable(s) considered in 51% of papers. Further, a total of 37% of the papers included in the review investigated physiological effects in relation to contaminant concentrations. Of the papers, 98% dealt with contaminant exposure at the individual level, leaving population level effects largely unstudied. Solitary subadult and adult polar bears were included in 57% and 79% of the papers, respectively. Younger bears were included in fewer papers: yearlings in 20% and cubs-of-the-year in 13%. Only 12% of the papers examined reproduction relative to contaminants. Finally, body condition was included in 26% of the research papers, whereas variables related to polar bear diet were included in ≤9%. Based on our findings, we suggest future polar bear toxicology studies increase sample sizes, include more ecological variables, increase studies on family groups, and increase the applicability of studies to management and conservation by examining pollution effects on reproduction and survival.

Comparative review of the distribution and burden of contaminants in the body of polar bears

“…As shown in Figure 1, the median pre-2000 contaminant concentration is high in the liver, and where the processes of detoxification take place and one of the most studied organs in polar bear ecotoxicology based on this literature review (AMAP 2018; Bechshøft et al, 2018), with a median of 1395 ng/g (quantile 25 %: 41 ng/g; quantile 75 %: 30675 ng/g) pre-2000 and a median of 115 ng/g (quantile 25 %: 19 ng/g; quantile 75 %: 965 ng/g) post-2000. Similar chemical fingerprints were found for the liver (Figure 2B) and kidneys (Figure 2A) for metals and PCBs, where both had the highest levels of contaminants; however, the median analysis found that the metals (other than Hg) and PCBs were approximatively 4-to 5-fold less concentrated in the liver compared to the kidneys.…”

An Evaluation of Studies on the Potential Threats Contributing to the Decline of Eastern Migratory North American Monarch Butterflies (Danaus plexippus)

“…A systematic review of available peer-reviewed literature was performed following the procedure outlined in Bechshoft et al (2017), but using monarch-specific terms associated with hypotheses regarding population declines in the Web of Science TM (Reuters, 2016). An initial list of papers was established through a literature search of all databases, including the Web of Science Core Collection, Current Contents Connect, FSTA (The Food Science Resource), KCI (Korean Journal Database), MEDLINE, Russian Science Citation Index, SciELO Citation Index, and Zoological Record, with no limitations placed on the publication date.…”

The influence of global climate change on accumulation and toxicity of persistent organic pollutants and chemicals of emerging concern in Arctic food webs

“…58,232,233 The use of meta-analysis in ecotoxicology is still in its infancy, but could be applied in these studies if both monitoring programmes and individual research studies make raw data publicly available, or at least report metadata beyond its specic use in a particular study. 234,235 For future studies, high-resolution spatial and temporal data and variability (e.g., local sea ice conditions, daily and seasonal temperature variations) should be considered, instead of climate variables averaged over large spatial and temporal scales, if possible. Considering the potential effects of intermittent and/or extreme weather events (e.g., rain-on-snow events) is also important as these anomalies are predicted to increase in response to a warming climate.…”