Temporal and spatial scales of effects of toxic and non-toxic stressors
- Environmental Protection Agency, Newport, OR (United States)
Estuarine ecosystems are potentially subjected to over 25 types of non-toxic stressors, including sedimentation, nutrients, exotic species, and habitat loss. Many non-toxic stressors operate over entire estuaries. For example, spread of exotics such as Spartina in Willapa Bay, WA may impact much of the intertidal area. Alterations due to toxic pollutants tend to be localized near their inputs. However, trophic transport can spread DDT and PCBs throughout a much wider area. Toxic pollutants are often introduced into the environment rapidly through discharges and spills, and then affect organisms fairly rapidly (within minutes to over a life cycle). The time course for non-toxic stressors is more variable. Some non-toxic alterations are very rapid, such as physical manipulation of habitats (e.g., filling). Alterations to habitats or watershed inputs are gradual, and thus difficult to detect in standard studies. For example, a slight increase in segmentation is difficult to quantify over a few years, but over decades could have major effects on estuarine ecosystems. The duration of effects of toxic pollutants depends upon their dilution, degradation and burial rates, and range from minutes for rapidly diluted soluble pollutants to decades or centuries for recalcitrant pollutants such as DDT. Duration of effects for non-toxic stressors are often ``permanent`` over ecological time for two reasons. Firstly, many non-toxic alterations are due to changes in watersheds, which recover slowly if logged or not at all if native habitat is transformed for development or farming. Secondly, several of the non-toxic stressors, such as invasions of exotics, result in a new, ``stable`` ecological system, so there is no recovery in the sense that pollutants degrade.
- OSTI ID:
- 211946
- Report Number(s):
- CONF-9511137-; ISBN 1-880611-03-1; TRN: IM9617%%262
- Resource Relation:
- Conference: 2. Society of Environmental Toxicology and Chemistry (SETAC) world conference, Vancouver (Canada), 5-9 Nov 1995; Other Information: PBD: 1995; Related Information: Is Part Of Second SETAC world congress (16. annual meeting): Abstract book. Global environmental protection: Science, politics, and common sense; PB: 378 p.
- Country of Publication:
- United States
- Language:
- English
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