Effects of changing land use on the microbial water quality of tidal creeks.

Population growth along the southeastern United States coast has precipitated the conversion of forested watersheds to suburban and urban ones. This study sampled creeks representing forested, suburban, and urban watersheds along a longitudinal gradient for indicators of water quality, including traditional indicator bacteria (fecal coliforms and enterococci) and alternative viral indicators (male-specific and somatic coliphages). Tested microorganisms were generally distributed with highest concentrations in creek headwaters and in more developed watersheds. The headwaters also showed the strongest predictive relationship between indicator concentrations and urbanization as measured by impervious cover. A seasonal pattern was observed for indicator bacteria but not for indicator viruses. Coliphage typing indicated the likely source of contamination was nonhuman. Results suggest that headwater creeks can serve as sentinel habitat, signaling early warning of public health concerns from land-based anthropogenic activities. This study also implies the potential to eventually forecast indicator concentrations under land use change scenarios.

Assessing coastal waters of American Samoa: territory-wide water quality data provide a critical "big-picture" view for this tropical archipelago.

The coastal waters of American Samoa's five high islands (Tutuila, Aunu'u, Ofu, Olosega, and Ta'u) were surveyed in 2004 using a probabilistic design. Water quality data were collected from the near-shore coastal habitat, defined as all near-shore coastal waters including embayments, extending out to 1/4 mile off-shore. Hydrography and water column samples were collected, and water quality data were compared to the Territorial water quality standards for pH, dissolved oxygen (DO), Enterococcus, chlorophyll a, water clarity, total nitrogen, and total phosphorus. All station measurements for pH, DO, and Enterococcus satisfied the local water quality standards, although some fraction of the Territory could not be assessed for either DO or Enterococcus. With respect to chlorophyll a, 66 +/- 18% of Territory coastal waters complied with the standard, while 34 +/- 18% failed to comply with the standard. For water clarity, 54 +/- 18% of the Territorial waters complied with the standard while 42 +/- 7% failed to comply. Territorial waters satisfied the standards for total nitrogen and phosphorus 72 +/- 17% and 92 +/- 10%, respectively. These data provide the first "big-picture" view of water quality in the near shore region around the high islands of American Samoa. While the picture is encouraging, these data suggest emerging water quality concerns.

Assessing the ecological condition of a coastal plain watershed using a probabilistic survey design.

Using a probabilistic survey design, we assessed the ecological condition of the Florida (U.S.A.) portion of the Escambia River watershed using selected environmental and benthic macroinvertebrate data. Macroinvertebrates were sampled at 28 sites during July-August 1996, and 3414 individuals were identified. Taxonomic data were distilled into the 8 m of the Stream Condition Index (SCI), developed specifically for Florida waterways, and sites were classified on an ordinal scale as very good, good, poor, and very poor. The weighted cumulative distribution function of the SCI showed that 8% (+/- 7) of the stream and river miles in this landscape were in very good condition, while 25% (+/- 7), 51% (+/- 16), and 16% (+/- 15) were in good, poor, and very poor condition, respectively. The only environmental parameter significantly correlated with SCI was dissolved oxygen (DO), and two sites classified as very poor had oxygen levels around or below 2 mg L(-1). However, other sites exhibited similarly low SCI values without the attendant low DO, implying that factors determining site condition were complex and multivariate. The results of this survey corroborate Federal and state assessments demonstrating that many locations within this watershed exhibit significant degradation.