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Effects of Environmental Perturbations on the Aquatic Community in the San Juan River

Metadata Updated: August 15, 2019

Razorback suckers (Xyrauchen texanus) and Colorado pikeminnow (Ptychocheilus lucius) are two endangered species of cyprinids located in the San Juan River Basin. Numerous factors may be contributing to the decline of these fish populations including hydraulic alterations (impoundment; altered thermal and hydrological regimes), non-native species interactions and contaminants. An assessment of the physical (temperature, substrate, ultraviolet [UV] radiation), biological (macroinvertebrates), and chemical factors (metals, polycyclic hydrocarbons, other water quality factors) was conducted to determine whether these factors could be limiting populations at six sites within the San Juan River and at one site in Los Pi[HTML_REMOVED]os River. Metal concentrations in sediment, surface and pore-waters were low, although significant differences in surface waters were found between sites. Hazard Quotients were calculated and indicate the potential risk for adverse effects should be considered for aluminum, lead and copper. Toxic Unit modeling also suggested a potential toxicity from sediments at several sites. Concentrations of 16 Priority Pollutant polycyclic aromatic hydrocarbons (PAHs) were low in sediment, pore water and Semipermeable Membrane Devices. Several compounds were found that are known to be toxic to aquatic organisms following photoactiviation by UV-B radiation. However no significant mortality to juvenile Colorado pikeminnow occurred during in-situ exposures conducted in the presence and absence of UV radiation. Seven-d reproduction tests with Ceriodaphnia dubia revealed that sediment pore water reduced reproduction at several sites. Physical and chemical habitat factors potentially affecting the distribution and composition of the macroinvertebrate community were evaluated. Macroinvertebrate populations were significantly different across sites. Differences, however, were not related to metal or organic contamination. Physical habitat variables of temperature, current velocity, and substrate size were useful predictors of macroinvertebrate densities between sites. A comparison of invertebrate communities on natural and artificial substrates indicated that a lack of suitable substrate is the main factor limiting macroinvertebrate distribution and composition at our study sites. The artificial substrates collected a more diverse community, and contained from 5 to 538 times more taxa than the Hess samplers. Community metrics were statistically significant (P < 0.05) between artificial substrate and Hess sampling methods in unstable (sand, silt, embedded cobble) substrates. Statistical differences were not observed when substrates associated with healthy invertebrate communities (gravel, loose cobble) were encountered. Numerous factors may be impacting endangered fish populations of the San Juan River. However, the influence of contaminants has not been unequivocally demonstrated. Additional analysis of toxicity data, contaminants, and invertebrate community may provide greater insight as to whether these multiple stressors may be limiting populations of razorback suckers and Colorado pikeminnow. Such information is necessary for future management decisions relating to mineral and gas exploration in the Basin.

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Non-Federal: This dataset is covered by different Terms of Use than License: No license information was provided.

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Metadata Date February 1, 2001
Metadata Created Date August 15, 2019
Metadata Updated Date August 15, 2019
Reference Date(s) January 1, 2000 (publication)
Frequency Of Update notPlanned

Metadata Source

Harvested from Pennsylvania Geospatial Data Clearinghouse

Additional Metadata

Resource Type Dataset
Metadata Date February 1, 2001
Metadata Created Date August 15, 2019
Metadata Updated Date August 15, 2019
Reference Date(s) January 1, 2000 (publication)
Responsible Party U.S. Geological Survey, Biological Resources Division, Columbia Environmental Research Center (Point of Contact)
Contact Email
Access Constraints Use Constraints: none, Access Constraints: none
Bbox East Long -106
Bbox North Lat 38
Bbox South Lat 37
Bbox West Long -111
Coupled Resource
Frequency Of Update notPlanned
Harvest Object Id 918e93a2-c29d-4c51-8ccd-907344c267ea
Harvest Source Id 461fc638-8de6-4c37-9f60-43399e6f6031
Harvest Source Title Pennsylvania Geospatial Data Clearinghouse
Licence Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the accuracy or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. It is strongly recommended that these data are directly acquired from a U.S. Geological Survey server, and not indirectly through other sources which may have changed the data in some way. It is also strongly recommended that careful attention be paid to the contents of the metadata file associated with these data. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and/or contained herein.
Metadata Language
Metadata Type geospatial
Progress completed
Spatial Data Service Type
Spatial Reference System
Spatial Harvester True
Temporal Extent Begin 1996-07-01
Temporal Extent End 1996-08-01

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