Chapter 15 - Effects of Pollution on Populations, Communities, and Ecosystems

Abstract

If the sensitivity to pollution of the different species in a community follows a normal distribution, then we could identify species particularly sensitive and thus prone to quickly disappear after a pollution event, and species more tolerant than average, that dominate the community under polluted conditions. Both sets of species are useful as indicators of environmental pollution by absence or occurrence (and increase in abundance), respectively. A species whose absence, presence, or abundance reflects a specific environmental condition is termed an indicator species. This concept supports a static vision where shifts in tolerance within a region - due to acclimation- or among biogeographical regions -due to genetic differences- are not considered. However, absence/presence of indicators has been proposed for routine assessment of atmospheric (lichens) and freshwater (insect larvae) pollution, and it is reflected in the Water Framework Directive as a biological quality element intended to categorize the ecological status of water bodies. In marine waters biotic benthic indices are useful to track temporal changes but not to compare among geographical areas. In soft-bottom marine environments organic enrichment causes proliferation of opportunists and reduction of diversity, but natural factors such as fluctuating salinity may also explain low diversity. Physical disturbance or toxic chemicals are not expected to cause the same pattern of response than organic enrichment. Species:abundance curves better describe changes in community structure. We are also interested in assessing the risk that pollution poses for the many ecosystem services provided by marine ecosystem to humankind, including provisioning services such as fisheries, regulating services such as fixation of atmospheric CO2 through primary production, and cultural services such as recreational opportunities. All those services are based on functional attributes. However, effects of pollution on those attributes are difficult to predict.