Approaches to Understanding the Cumulative Effects of Stressors on Marine Mammals (2017) / Chapter Skim
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3 Current Understanding of Stressors
3 Current Understanding of Stressors
Pages 33-40
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From page 33... ...
points Extrinsic Stressor A factor in an animal's external environment that Anthropogenic: creates stress in an animal Pollutants, ship strike, entanglement, noise, psychological factors (e.g., perceived threat) Natural, but potentially influenced by anthropogenic activity: Harmful algal blooms, resource limitation, predator pressure, pathogens, temperature, salinity, naturally occurring chemicals, intra or interspecific competition Ecological Driver A biotic or abiotic feature of the environment Loss of keystone or foundation species, recurring climate patterns such that affects multiple components of an ecosystem as El Niño, climate change directly and/or indirectly by changing exposure to a suite of extrinsic stressors 33
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From page 34... ...
There is a strong spatial component to mortality, demographic impacts, and even cohort failures bycatch of marine mammals, with "hotspots" influenced by in some marine mammal species. The cumulative effect of marine mammal density (Block et al., 2011)
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. Heavy metals, particularly mercury -- which has been used as flame retardants, are another class of POPs that associated with immunological and neurotoxic effects and have spread globally in the environment and have also been can cause permanent damage to the brain (Kakuschke and reported in a broad array of marine mammal species (Houde Prange, 2007; Farina et al.
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From page 36... ...
For proliferate to form dense concentrations under certain example, viral pathogens of the genus Morbillivirus have environmental conditions. When high cell concentrations been associated with severe respiratory illness and linked to form, the toxins that they produce can harm the health of large-scale die-offs of marine mammal populations worldmarine life, and this is referred to as a harmful algal bloom wide (Van Bressem et al., 2014)
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From page 37... ...
. At present, few examples exist that demonstrate direct impacts of habitat limitation on marine mammal populations, but as critical habitats become more limited by ecological drivers, this type of stress may become preferred prey, Chinook salmon (see Figure 3.1)
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Various other short-term responses of marine Frameworks using individual-based models are being develmammals to boat traffic and swimmers have been reported. oped to simulate the potential effects of boat traffic and other Well-documented examples include avoidance behavior human activities on marine mammal populations (New et al., by bottlenose dolphins (Tursiops truncatus)
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, influ AMONG STRESSORS ences the distribution and foraging of numerous marine mammal species and impacts reproductive rates and popu- The range of extrinsic stressors to which marine mamlation dynamics (Fujiwara and Caswell, 2001; Greene and mals can potentially be exposed over a lifetime has been Pershing, 2004; Jiang et al., 2007)
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From page 40... ...
exposure to a stressor can be associ Numerous studies have evaluated the impact of vari- ated with dysregulation of endocrine and homeostatic funcous extrinsic stressors on the individual health, survival, or tion and therefore may be an important mechanism through reproduction of marine mammal species. Stressors such as which a cumulative effect manifests within individuals.
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