Combined and interactive effects of global climate change and toxicants on populations

and communities.

MOE, J., DE SCHAMPHELAERE, K., CLEMENTS, W., SORENSEN, M., VAN DEN BRINK, P., LIES, M.; 2013; Environmental Toxicology and Chemistry, Vol 32, No. 1, pp.

49-61.

Group 5Herzallah, Mohammed A.M.

Itoe, Nolinga FaithKimbi Yaah, Velma Beri

Lopez Karolys, Andrea CarolinaMbah Bismarck, Nji FowaMingo Ndiwago, Damian

Mumbanza Mundondo, Francis

Background

• Ecotoxicological Reserach

- Effect of chemical stressors, on population, communities and ecosystems.

• Changes in environmental conditions as a result GCC will affect thevulnerability of populations and communities to toxicants.

- Stress due to GCC may reduce the potential for resistance to and recover fromtoxicant exposure.

• The complexity of GCC and toxicants interactions.

• The release, fate, and exposure of toxicant are also likely to be affected byGCC.

• Population and community level responses to toxicants under GCC arelikely to be influenced by various ecological mechanism.

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Goals, Questions

• How will GCC related changes in environmental conditions affect the vulnerability of populations and comunities to toxicants ?

• How will combined impacts of toxicants and GCC-related stressors at the individual level be influenced by ecological mechanisms at:- The population level: (growth rate)?

- The community level: (species density, ecosystem, functions and services)?

• Focus on ecological mechanisms four topics.- Demographic and interspecific processes influencing propagation of individual-

level responses.

- Resistance, resilience, and recovery from disturbances.

- Acquired tolerance to stressors and associated costs.

- Species traits and population vulnerability in a landscape context.

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Approach

• Ecological mechanisms at the population and community levels susceptible to:

- Compensate or exacerbate the individual-effects of stressors at the higher level of biological organization.

• Design of a specific scheme to explain possible combined effects of GCC and toxicant at the population and community levels (Fig 1)

• 4 topics (3 study cases) discussed to illustrate possible joint effect of GCC and toxicant at population and community levels.

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Fig. 1 Combined impacts of GCC and chemical stressors across biological levels of organization.

Topics discussion and case studies

Topics discussion and case studies

1. Demographic and interspecific processes influencing propagation of individual-level responses

At population level :- Density-dependent mechanisms compensating for the impact of stressors

(population-level impacts).

- Sublethal and latent effects and the timing of multiple stressors in relation to the life-history stages (stronger effects at population level).

Examples: Salamander vs Atrazine ; T and Hg vs nestling production in tree swallows.

At community level :- Impact on species interaction and food web structures.

Examples: Polar bears- sea ice breakup-open water seal species-contamination (Chlorinates, brominates); Tawny owls-colder winter-more PCB- alternative prey (passerine birds).

Case study: impacts of global warmingand cyanotoxins on plankton communitiesin lakes.

At population level:- Chemical and region specific effects

of GCC on persistence of compound.- Direct (T ) and indirect

(eutrophication) on population recovery .Ex. GCC contributes to prolong recovery period (Fig 2)

At community level: - Lower resistance to

contaminant, lower recovery as a result of impairment by GCC. Fig. 2 Impacts of global warming and cyanotoxins on

plankton communities in lakes.

Case Study 1

2. Resistance, resilience, and recovery from disturbances.

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Population level- When a population is exposed to a stressor over

multiple generations, natural selection may favor genotypes that are more tolerant to this stressor increase the mean tolerance of the population.

- Local adaptation of field populations with a history of stress exposure, for both chemical contaminants and climate-related factors.

Genetic adaptation to a toxicant usually results in a reduction of genetic diversity at the population level.

Fig 3. Simplified visualization of the costof tolerance concept.

Case study: Impacts of ultravioletradiation and metals on invertebratecommunities in streams.

At population level- Genetic acquired resistance (reduced

fitness). Example: Oligochaete vs Cd

- Reduction of genetic diversity- Increased susceptibility to different

environmental stressorsExample: Fresh water snails-Cd-T

At community level- Pollution-induced community

tolerance: elimination of most sensitive species, less species with tolerance to GCC-related stressors. (Fig.4).

Fig. 4 Impacts of ultraviolet (UV) radiation and metals oninvertebrate communities in streams

Case study 2

3. Acquired resistance to stressors and associated costs.

Community Level

Fig 5. Conceptual model of impacts of global climate change (GCC) on species compositionand toxicant sensitivity for a hypotheticalcommunity in a given location.

Case study 3: Impacts of futureclimate-related pesticide use oninvertebrate communities in streams.

At population level- Intrinsic sensitivity of species to

toxicant influenced by climatic variables (T )

At community level - Changes in community due to

toxicant exposure associated with toxicological sensitivity, duration of life cycle, migration (Fig 6).

- Alteration of community vulnerability to toxicant with GCC (shifts in spatial and temporal species distribution).

Fig 6. Impacts of future climate-related pesticide useon invertebrate communities in streams.

Case study 3

4. Species traits and population vulnerability in a landscape context

Conclusion

• The four topics discussed are relevant for:

- Interpreting existing observational data sets (case study 1).

- Generating testable hypotheses regarding future effects of GCC and toxicant exposure (Case study 2 and 3).

- More case studies and testing are needed before validating these ecological principles as a tool to make predictions about different climate and toxicant combinations of effects in different ecosystems

• Long-term ecotoxicological experiments that incorporate a realistic downscaling of future climate projections in combination with high environmental variation would enable more reliable predictions of toxicant impacts under climate change.

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Critical Evaluation

• The four ecological mechanisms used in the study are appropriate .Reason : They show the relationship at various levels of biological organization.

• The approach of using case studies is appropriate .Reason : The compounded effects of GCC and toxicants often lead to surprises

at the population level. Hence case studies are necessary to have specific results• The results cannot be used for ERA . • More case studies are needed for predictions to be possible • Various communities can be exposed to known concentrations and altering

climatic parameter thereby simulating GCC in lakes (Experimental Lake Area in Canada) . This will be an experiment in a natural system

• Specific schemes should be developed for different ecosystems starting by the most vulnerable

• The effects of climate change on humans and how they are trying to adapt to thelatter have not been considered in the framework developed ( quantity and diversity of new chemicals)

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