GBIC Full Text
Permanent URI for this collectionhttps://hdl.handle.net/1969.3/28601
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Browsing GBIC Full Text by Subject "accretion"
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Item Galveston Bay oyster reef survey. Volume I: Technical reports. Volume II: Map atlas.(Galveston Bay National Estuary Program, 1997) Powell, Eric N.; Song, J.; Ellis, M.; Choi, K.;Report I: Oyster reefs make up one of the primary geological features of Galveston Bay. They affect current flow and salinity and provide a primary substrate for a wide variety of hard-bottom invertebrates and fish. The commercial oyster fishery in Galveston Bay is one of the more important ones in the U.S. and the private (or noncommercial) harvest of shellfish in Texas ranks third in the country. Accordingly, the oyster reefs play a pivotal geological, ecological and commercial role in Galveston Bay. The purpose of this study was to survey the oyster reefs of Galveston Bay and compare them to earlier surveys. Of particular importance were concerns about the perceived loss of reef area and the lowering of relief on the remaining reefs. The primary objectives of this study were to resurvey the aerial extent and relief of the principal reefs in Galveston Bay.; Report II: Oysters are generally considered to respiratory best at moderate salinities (12-20 ppt). Factors restricting oyster production outside this salinity range include increased respiratory demand, decreased filtration rate, and mortality at lower salinity and predation and disease at higher salinities. Production on reefs, however, is significantly affected by variables like food supply and rate of recruitment that might follow salinity in a more complex way. In addition, the direct affect of the commercial fishery is poorly known. Some reefs are heavily fished, others are less so, in the same salinity regime. Accordingly, the production of oyster populations might not be a simple function of salinity, and, indeed, the accompanying survey of reef accretion and loss over a 20 year interval in Galveston Bay did not reveal a clear trend with the prevailing salinity gradient over that time. Moderate salinity areas, on the average, accreted more new reef, however areas of similar salinity accreted and lost reef area during this time over much of the salinity gradient in the bay.Item Shoreline changes on Galveston Island (Bolivar Roads to San Luis Pass): An analysis of historical changes of the Texas Gulf shoreline.(University of Texas, Bureau of Economic Geology, 1974) Morton, R.A.;Historical monitoring along Galveston Island records the type and magnitude of changes in position of the shoreline and vegetation line and provides insight into the factors affecting those changes. Documentation of changes is aided by the compilation of shoreline and vegetation line position from topographic maps, aerial photographs, and coastal charts of various vintages. Major and minor factors affecting shoreline changes include: (1) climate, (2) storm frequency, (3) local and eustatic sea-level conditions, (4) sediment budget, and (5) human activities. The major factors affecting shoreline changes along the Texas Coast, including Galveston Island, are a deficit in sediment supply and relative sea-level rise or compactional subsidence. Changes in the vegetation line are primarily related to storms. Studies indicate that shoreline and vegetation line changes on Galveston Island are largely the result of natural processes and their effects is requisite to avoid or minimize physical and economic losses associated with development and use of the beach.