Climatic stressors

Apart from of investigating the concentration of priority pollutants to assess the temporal and geographic trends as it has been done in the Ebro river basin until nowadays, the SCARCE project pretends to evaluate the consequences of the climate change in the water quality as well as predicting new environmental risks derived from water scarcity. This will be done by determining the presence of new priority (i.e. perfluorinated compounds) and emerging toxicants in Mediterranean river ecosystems in the Iberian Peninsula. In a subsequent step, the effects of chemical and environmental stressors on the biota will be assessed by combining field and experimental studies. The effects of multiple stressors will be addressed from a multi-biomarker perspective [27]. 

The virus-associated mass mortalities that took place among marine mammals in the 1980s and 1990s elicited an interest in co-factors that may have contributed to the severity of these events. The deaths of 20,000 harbor and several hundred grey seals in northern Europe in 1988 prompted questions about climate change, algal blooms, environmental pollutants, exotic diseases and other perceived stressors [54], After the identification of a newly described virus, phocine distemper virus (PDV) [55], concern still lingered that immunotoxic environmental contaminants could have facilitated the outbreak. 

Many of the factors that can affect organisms adversely are inherent stressors, including availability of nutrition, water quality, temperature and other climatic extremes, disease, and predation. It is important to be able to separate effects of inherent stressors from those of toxic chemicals. There are often important synergistic relationships between inherent stressors and the effects of toxic chemicals. Organisms that are under stress from inherent stressors are likely to be more susceptible to the effects of xenobiotic toxicants. 

Life history models may be useful for considering age- or stage-specific variability in sensitivity in the extrapolation of response however, it should not be assumed that smaller or younger stages are always the most sensitive. The few studies that have addressed the impact of time of year on responses of aquatic communities to a stressor indicate that, in freshwater communities, threshold concentrations for direct toxic effects vary within a factor of 2 among seasons — well within the normal range of variation observed in laboratory toxicity tests. However, at greater exposures, the intensity and duration of direct and indirect responses may vary considerably between different periods of the year because of the influence of climatic and seasonal factors on recovery. 

J.M. Gunn, E. Snucins, N.D. Van, M.T. Arts (2001). Use of water clarity to monitor the effects of climate change and other stressors on oligotrophic lakes. Environ. Monit. Assess., 67, 69-88. 

Parts III, IV and V deal with the distribution of trace elements in biota and reservoirs (soils and sediments). In this context, it should be noted that organisms, populations, biocenoses and finally the entire ecosystem are influenced by a number of different biotic and abiotic stressors under natural conditions. These are for example climatic changes, variations in radiation regimes or availability of food resources, predator-prey relationships, parasites, diseases, intraspecific and interspecific competition. Stress is an existential prerequisite for all biological levels of organization, as it... 

Peter J. Dillon, Ph.D. (Toronto), F.R.S.C. is a Professor in the Environmental Resource Studies and Chemistry Departments at Trent University where he is Director of the new Water Quality Center. His research interests focus on biogeochemistry effects of regional and global-scale stressors including acid deposition, climate change, mercury and other trace metals on environmental chemistry. 

Climate is most stressful in cold weather when there are low ambient temperatures, high wind speeds, and absence of solar radiation. The humidity content is very low in freezing cold and therefore not an important factor. However, wet cold at ambient temperatures just above the freezing point can form a considerable cold stressor since water takes away the body heat more quickly through convection. Body cooling occurs more rapidly when people are wet (Thompson and Hayward, 1996). Therefore, hypothermia is more apparent in wet cold than in dry cold. 

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