Browsing by Author "McFarlane, Robert W."
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Item A conceptual model of the Galveston Bay ecosystem(Galveston Bay National Estuary Program, 1993) McFarlane, Robert W.;The goal of this project was development of a set of habitat-based, problem-oriented, nested, hierarchical, box-and-arrow conceptual models tiered to three levels of complexity. (1) Simple, nontechnical models that facilitate understanding of important issues by the public focus on the landscape approach and provide an overview of the ecosystem. (2) Complex detailed models that reflect scientific consensus describe the structure, function and connectivity of the habitat components of the ecosystem and its connection to adjacent habitats. (3) Simple technical models useful to decision-makers, resource managers and bay users describe the interconnectedness of the ecosystem.Item Conceptual models of the Galveston Bay ecosystem(Galveston Bay National Estuary Program, 1993) McFarlane, Robert W.; Jensen, Richard W. Russell W. Kiesling, and Frank S. Shipley; Proceedings: The Second State of the Bay Symposium. February 4 - 6, 1993A series of hierarchical conceptual models of the Galveston Bay ecosystem are being developed to facilitate understanding of the bay and optimize management of anthropogenic factors that affect the ecosystem. These models are habitat-based and problem-oriented. It is desirable that these models be understandable by the general public, useful to managers and decision-makers, and retain sufficient detail to be meaningful to scientists.Item DRAFT - A Conceptual Model of the Galveston Bay Ecosystem(Galveston Bay National Estuary Program, 1993-08) McFarlane, Robert W.The goal of this project was development of a set of habitat-based, problem-oriented, nested, hierarchical, box-and-arrow conceptual models tiered to three levels of complexity. (1) Simple, nontechnical models that facilitate understanding of important issues by the public focus on the landscape approach and provide an overview of the ecosystem. (2) Complex detailed models that reflect scientific consensus describe the structure, function and connectivity of the habitat components of the ecosystem and its connections to adjacent habitats (3) Simple technical models useful to decision-makers, resource managers and bay users describe the interconnectedness of the ecosystem.Item An environmental inventory of the Armand Bayou Coastal Preserve(Galveston Bay National Estuary Program, 1991) McFarlane, Robert W.;The goal of this report was to gather and integrate existing data, identify data gaps, and describe the environmental attributes of Armand Bayou relevant to the development of a management plan for the Armand Bayou Coastal Preserve. Armand Bayou can be influenced by events anywhere within, as well as beyond, its watershed. The physical characteristics of the coastal preserve area have changed drastically due to 5 to 9 feet of land-surface subsidence across the watershed since 1906. The lower reach of the bayou has changed from a wetland-bordered freshwater stream to a brackish tidal lake nearly devoid of wetlands. Mud Lake has expanded from 100 acres in 1956 to more than 325 acres today. All of the 275 acres of wetlands present in 1956 have been lost; replacement wetlands, of a different nature, amount to 24 acres, for a net loss of 91 percent. The water quality of Armand Bayou is poor. It is ranked as the second-highest stream on the Texas coast for hypoxia, a condition of low oxygen produced by algae responding to elevated nutrient levels. Annual and monthly levels for total and ortho- phosphorus are persistently above thresholds characteristic of eutrophic streams. Ammonia and nitrate nitrogen exceed eutrophic thresholds during the cooler months but appear to be removed from the bayou by accelerated algal growth during warm months. Fecal coliforms are a problem of long standing. No investigation of toxicants in the water or sediments has been undertaken. The 60 square mile (38,400 acre) watershed receives 48 inches of rainfall annually and contributes approximately 80,000 acre-feet (71.4 million gallons per day, MGD) of freshwater inflow to Clear Lake. This rainfall varies greatly, even between localities very close together, and episodes of exceptionally heavy precipitation occur. Most of the watershed lies within the city limits of Pasadena, Deer Park, La Porte and Houston and has 38 percent residential urban and 6 percent industrial land use. Point source discharges have declined in number, from 6 to 3, but the volume of wastewater discharged has increased 35 percent, to 6.2 MGD, over the past decade. Point source stormwater discharges were 1.8 MGD in 1989. Controversial issues in recent years have involved the accelerated and increased delivery of residential-area stormwater to the bayou and the removal of irrigation water from the bayou. The current water quality monitoring station at Bay Area Boulevard does not reflect the input of nutrients and pollutants from Horsepen Bayou, a major tributary which receives the bulk of treated wastewater effluent discharged into the bayou. The quarterly or semi-annual monitoring of recent years is inadequate to determine stream conditions. A 24-hour water quality survey during the warm season is needed to determine the extent of oxygen sag during hours of darkness. An additional monitoring station that will reflect the contribution of pollutants from Horsepen Bayou is needed. Monthly sampling should be resumed for 2 to 3 years to establish an adequate baseline of information. An investigation of toxicants in water and sediment samples should be conducted. The flora and fauna of Armand Bayou are poorly known and population trends cannot be determined. The freshwater biota upstream of Bay Area Boulevard, and in the tributaries, is virtually unknown. The lower reach is potentially a valuable nursery habitat for certain commercial and recreational finfishes and shellfishes. A survey of these species in Mud Lake should be undertaken. The extent of bottomland forest flooding and value of this forest habitat as a contributor of detritus and nutrients, and as a sink for nutrients and pollutants, should be determined.Item An environmental inventory of the Christmas Bay Coastal Preserve(Galveston Bay National Estuary Program, 1991) McFarlane, Robert W.;The goal of this report was to gather and integrate existing data, identify data gaps, and describe the environmental attributes of Christmas Bay relevant to the development of a management plan for the Christmas Bay Coastal Preserve. Specific topis to be addressed included human occupancy, physical habitat alterations, water quality trends, freshwater inflows, infrastructure, hydrological and meteorological influences, and the living resources.Item Freshwater Inflow to Galveston Bay(McFarlane & Associates, 1987) McFarlane, Robert W.Galveston Bay is the most productive estuary in Texas. The Trinity River provides one-half of the freshwater inflow and nutrients, and a substantial amount of the sediment, which reaches Galveston Bay. The Lake Livingston dam and reseervoir, to date, have not reduced the annual river discharge to Trinity Bay but a slight seasonal shift has reduced flow from January to May while increasing flow from August to December. The frequency and duration of floods, important to the transport of floodplain nutrients, has not diminished. The proposed Wallisville dam and reservoir, near the mouth of the river, will potentially divert as much as 39 percent of river discharge and entrap substantial, but unknown, quantities of sediment and nutrients, leading to higher salinities in Trinity Bay and erosion of the rivermouth delta. Sheet flow of floodwaters across the delta marshes, an important nutrient transport mechanism, will be reduced. It is essential that a comprehensive environmental impact assessment, conducted by an independent third-party, be completed to consider the synergistic and cumulative effects of the several in-progress or proposed development projects which currently threaten the Galveston Bay ecosystem.Item Gull, Tern & Skimmer population trends in Galveston bay(Texas Natural Resource Conservation Commission, 1999) McFarlane, Robert W.; Proceedings: The State of the Bay Symposium IV. January 28-29, 1999The 1973 to 1996 Texas colonial waterbird census data for laughing gull, least tern, Forster's tern, royal tern, Caspian tern, Sandwich tern, gull-billed tern, and black skimmer populations in Galveston Bay will be analyzed. The impact of nesting island loss will be evaluated.Item The Phenology of Commercial Penaeid Shrimp in Galveston Bay(Galveston Bay Estuary Program, 2003) McFarlane, Robert W.; The Sixth Biennial State of the Bay Symposium January 14-16, 2003Understanding of the structure and function of an estuarine ecosystem, such as Galveston Bay, may be enhanced by the simultaneous consideration of all of the nine major estuaries in Texas. These estuaries reflect the precipitation and temperature gradients and river outfalls along the coast. Phenology is the study of the temporal aspects of recurrent natural phenomena and their relation to weather and climate (Lincoln et al., 1998). The objective of this study is to examine the phenology of the utilization of Texas estuaries by the dominant commercial shrimp species.Item Population Trends of Colonial Waterbirds in Galveston Bay(Texas Natural Resource Conservation Commission, 2001) McFarlane, Robert W.; Proceedings: The State of the Bay Symposium V. January 31 - February 2, 2001The Texas Colonial Waterbird Census data for the 26 year period 1973 to 1998 were analyzed in search of population trends for the 22 species of colonial waterbirds nesting within the Galveston Bay ecosystem. The minimum, average, and maximum number of breeding pairs for each species is presented. The trends are graphed in the accompanying figures for each species. A trend line has been incorporated into each graph to aid interpretation but the reader is cautioned that colonial waterbird data seldom meet the inherent assumptions associated with linear regression trend analysis (independence, linearity, normal distribution, and homoscedasticity of variance). Trend lines near the horizontal indicate a stable, albeit fluctuating, population. Year-to-year variation is rather extreme for most species and breeding was absent in some years for some species. The total population for each species is double the pair number plus an unknown, but substantial, number of nonbreeding individuals. Ten species (45 percent) appear to have stable populations. Eight species (36 percent) appear to have increased in abundance to some extent. Only 4 species (18 percent) exhibit evidence of population decline.Item Shrimp farms: The next threat to Galveston Bay(Texas Natural Resource Conservation Commission, 1999) McFarlane, Robert W.; Proceedings: The State of the Bay Symposium IV. January 28-29, 1999Shrimp mariculture has migrated up the Texas coast and now threatens Galveston Bay. This activity poses three major threats to the health of the Galveston Bay ecosystem: (1) degradation of water quality, (2) the potential introduction of an exotic shrimp species, and (3) the potential introduction of an exotic shrimp pathogen or parasite. All of these threats have occurred in Texas estuaries and their environmental impact is unpredictable. The ecological footprint of a shrimp farm is much larger than the upland area occupied by the farm. Application of the Precautionary Principle would lead shrimp farmers and agency regulators to adopt a conservative approach until the absence of an environmental threat has been demonstrated. This paper will discuss the three necessary goals in order to attain ecologically sustainable shrimp farming.