Graduate Thesis Or Dissertation
 

Distribution of foraminifera, Netarts Bay, Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/s1784q00q

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  • Netarts Bay is a coastal lagoon on the northern Oregon coast. Four major sedimentary environments are recognized including channel, sand flats, mud flats, and marsh. Fine-grained sediment is carried in by streams and deposited in the marshes and mud flats. Fine sand for the channel and sand flats is derived from the open ocean beaches and turbulent zone. Organic carbon varies from 0.1 to 3.5 percent of the sediment and varies inversely with the sediment size. Carbonate carbon is unimportant. Fifty-one benthic foraminiferal species were recognized of which 37 formed two percent of the population in one or more samples. Four foraminiferal faunal groups were recognized: the Elphidiella Fauna inhabiting the channel, the Elphidium Fauna reaching greatest abundance on the central bay sand flats, the Ammonia Fauna inhabiting the mud flats and inner bay sand flats, and the Miliammina Fauna characterizing the marsh. Planktonic foraminiferal populations form less than one percent of the total foraminiferal population. Benthic foraminiferal populations on the order of 80 specimens /cm2 for the live populations and 200/cm3 for the dead are found in the dense vegetation of the marsh. Tidal flat populations are approximately an order of magnitude smaller and the channel population is one to two orders of magnitude smaller than for the tidal flat. Species diversity is greatest on the central bay tidal flats, averaging seven species per sample for live and 15 for dead populations. Values decrease as mud flats, marsh, and channel environments are approached. The total standing crop and most species inhabiting the innermost part of the bay display simultaneous bimodal population maxima in July and January. These peaks are possibly controlled by the availability of food. Ammonia cf. A. beccarii tepida and Elphidium incertum incertum show strong but independent population maxima in July and October respectively. Foraminifera-ostracod ratios range from 0. 6 to 41.5 with a mean of 13.8. Agglutinated-calcareous foraminiferal ratios vary inversely with sediment size and appear to be related to the pH of the sediments. Thecamoebians are rare in the bay but replace the foraminiferal population as fresh water environments are approached in the inflowing streams. Reworked fossil foraminifera are found only rarely.
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