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| 文件类型： | 文章 |
|---|---|
| 所有的著者/提供者： | Catherine M Pringle |
| ISSN: | 0887-3593 |
| OCLC号码： | 478666520 |
| 语言注释： | English |
| 注意： | Fig. 1. Potential Downstream Influences on Upstream Communities. Fig. 2. Location of the Caribbean National Forest in northeastern Puerto Rico, showing the 9 major river drainages of the forest, all of them dammed except for the Mameyes River. Fig. 3. The food web of highland montane streams in Puerto Rico indicating migratory organisms that are vulnerable to water abstraction in lowland stream reaches. Amphidromous and catadromous organisms both spend some part of their life cycle in the estuary/ocean. Fig. 4. Schematic diagram illustrating interstream differences in primary producers in (a) a stream characterized by high densities of atyid shrimp with no predaceous fishes, and (b) a stream with very low numbers of atyids and characterized by the presence of predaceous fishes. The atyid-dominated stream (a) had blue-green algal bands in shallow (< 3 cm) pool margins where atyids did not forage; in deeper water, atyids maintained a low-growing understory turf dominated by sessile diatoms (Bacillariophyta) and sometimes closely cropped filamentous blue-green (Cyanophyta) algae. In the atyid-poor stream (b), algal assemblages were characterized by high standing crop of loosely attached epipelic diatoms and no depth zonation. Fig. 5. Schematic diagram of the Rio Espiritu Santo, Puerto Rico, illustrating observed and potential downstream-upstream effects. Barriers, both natural (waterfalls) and artificial (dams and associated water abstraction), act as selective filters along the stream continuum. Superimposed on the upstream legacies created by these filters are the legacies created by interactive effects of both natural (e.g., hurricanes and droughts) and artificial (stream poisoning events, fishing, shrimp trapping, pollution) disturbances. |
| 奖励： | |
| 其他题名： | New Concepts in Stream Ecology: Proceedings of a Symposium |
摘要：
Modifications of lower watersheds such as water abstraction, channel modification, land-use changes, nutrient enrichment, and toxic discharge can set off a cascade of events upstream that are often overlooked. This oversight is of particular concern since most rivers are altered by humans in their lower drainages and most published ecological investigations of lotic systems have focused on headwater streams. Factors contributing to ecological processes or biophysical legacies in upper watersheds often go unacknowledged because they occur at disparate geographic locations downstream (e.g., gravel mining, water abstraction, dams) with significant lag times. This paper considers examples of how alterations to streams and rivers in their lower reaches can produce biophysical legacies in upstream reaches on levels from genes to ecosystems. Examples include: 1) genetic- and species-level changes, such as reduced genetic flow and variation in isolated upstream populations; 2) population- and community-level changes that occur when degraded downstream areas act as population "sinks" for "source" populations of native species upstream or, conversely, as "source" populations of exotic species that migrate upstream; and 3) ecosystem- and landscape-level changes (e.g., nutrient cycling, primary productivity, regional patterns of biodiversity) that can occur in headwater systems as a result of downstream habitat deterioration and hydrologic modifications. Finally, a case study from my own research illustrates the importance of careful consideration of downstream-upstream linkages in formulating research questions, designing experiments, making predictions, and interpreting results. The effects of dams and associated water abstraction in lowland streams of Puerto Rico has forced my colleagues and me to re-evaluate the results of ecological research that we have conducted in highland streams over the past decade and to redirect our research to consider downstream-upstream linkages.