R.H. Wolff | Search USGS

USGS2011

Invasion patterns along elevation and urbanization gradients in Hawaiian streams

Hawaii's extreme isolation has resulted in a native stream fauna characterized by high endemism and unusual life history characteristics. With the rapid increase in the human population, the viability of Hawaiian stream ecosystems is threatened by development and the associated habitat alteration. Thirty-eight sites on three islands (Oahu, Kauai, and Hawaii) were sampled to determine how habitat alteration resulting from urbanization and development was associated with the establishment of introduced species. Undeveloped sites had higher streamflow velocities, more riffles, lower embeddedness, deeper water, larger substrate, and lower water temperature than developed sites. Developed sites additionally had more pools and greater sparseness of riparian canopy cover. Overall, 23 fish species from 11 families and 5 crustacean species from 3 families were collected. Of these, 16 fish species and 3 crustacean species were introduced. Developed sites had on average almost twice as many species as undeveloped sites and were dominated by introduced species. Low-elevation sites were the most developed and supported the highest number of introduced species. However, species composition at some relatively undeveloped sites was impacted by downstream habitat alteration, since all native species must pass through the lower reaches to complete their life cycles. With increasing urbanization and development, the habitat features required by native species are disappearing and streams are becoming more suitable for generalist introduced species, which are typically better adapted for altered habitats than are native species. As development pressures in tropical island ecosystems increase worldwide, this will become an increasingly important issue globally. An understanding of which habitats are most likely to support nonnative species provides information necessary for developing a management strategy to protect aquatic ecosystems from invasive nonnative species.

Transactions of the American Fisheries Society↗

USGS2004

Relations between land use and organochlorine pesticides, PCBs, and semi-volatile organic compounds in streambed sediment and fish on the island of Oahu, Hawaii

Bed-sediment and/or fish samples were collected from 27 sites around the island of Oahu (representing urban, agricultural, mixed, and forested land use) to determine the occurrence and distribution of hydrophobic organic compounds including organochlorine pesticides, polychlorinated biphenyls (PCBs), and semi-volatile organic compounds (SVOCs). Of the 28 organochlorine compounds analyzed in the fish, 14 were detected during this study. Nineteen of the 31 organochlorine compounds and 40 of the 65 SVOCs were detected in the sediment. Urban sites had the highest number of detections and tended to have the highest concentrations of pesticides. Chlordane compounds were the most frequently detected constituents at urban sites, followed by dieldrin, polycyclic aromatic hydrocarbons (PAHs), and DDT compounds. PAHs were the most frequently detected constituents in watersheds with mixed (urban and agricultural) land use. The only pesticides detected at agricultural sites were DDT and its degradation products, DDD and DDE. No pesticides or PCBs were detected at the forested sites, but a few ubiquitous SVOCs were found in sediments at some forested sites. In general, concentrations of the most frequently detected pesticides were higher in fish than in sediment. Following a trend that has been observed elsewhere in the nation, concentrations of most organochlorine pesticides and PCBs are decreasing in Hawaii.

Hawaii↗