Nematodes had a mean abundance of hundreds per m 3 in an estuarine creek. They were four orders of magnitude less abundant in the water column than in the sediment. The water column nematode assemblage was dominated by three species of Metachromadora which comprised 57% of the suspended nematodes. Other abundant species were Chromadorita aff. minima and Ptycholaimellus pandispiculatus. Numbers of suspended nematodes were highest during the ebb and flood tides when currents were fastest. The two factors that appear to be most important in determining which species are in the water are the vertical distribution and the overall abundance of a species in the sediment. Surficial distributions and high sediment abundance will result in greater representation in the water column. Suspension in the water column and subsequent transport by tidal currents potentially plays a significant role in the local dispersal of certain meiobenthic nematode species. Corollaries to water column dispersal are an improved ability of nematodes in colonizing new habitats, an increased diversity in some habitats as animals are carried between habitats, and an interaction between hydrodynamic factors and benthic topography that affects small-scale spatial distribution.
Section 305(b) of the United States' Clean Water Act (CWA) requires states to assess the overall quality of waters in the states, while Section 303(d) requires states to develop a list of the specific waters in their state not attaining water quality standards (a.k.a impaired waters). An integrated, efficient and cost-effective process is needed to acquire and assess the data needed to meet both these mandates. A subset of presentations at the 2002 Environmental Monitoring and Assessment Program (EMAP) Symposium provided information on how probability data, tools and methods could be used by states and other entities to aid in development of their overall assessment of condition and list of impaired waters. Discussion identified some of the technical and institutional problems that hinder the use of EMAP methods and data in the analysis to identify impaired waters as well as development needs to overcome these problems.
A Use Attainability Analysis is being conducted to support new subcategories of designated uses for the Chesapeake Bay. The Chesapeake Bay deviates from traditional UAA applications due the need to consider numerous sources and jurisdictions and complex spatial ecological requirements. A flexible UAA approach has been adopted that relies on integrated and interdisciplinary modeling and analysis guided by a collaborative workgroup decision-making process. Various watershed modeling scenarios have been developed to help represent conditions associated with the UAA factors for determining attainability. Costs, screening level indicators of potential economic impacts, and cost-effectiveness are estimated to help characterize economic impacts and relative efficiency of these model scenarios. Repeated iterations of the analytical process are expected to facilitate decisions about acceptable allocations and highest attainable use boundaries.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.