Spatial and temporal variability of phytoplankton standing crop and primary production along the Texas-Louisiana continental shelf /
An ecological study of the phytoplankton along the Texas- Louisiana continental shelf that was conducted during five cruises between May 1992 and May 1993 showed strong spatial and temporal variability in both phytoplankton standing crop (as chlorophyll a) and primary production. The inner shelf (&...
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=743266531&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | An ecological study of the phytoplankton along the Texas- Louisiana continental shelf that was conducted during five cruises between May 1992 and May 1993 showed strong spatial and temporal variability in both phytoplankton standing crop (as chlorophyll a) and primary production. The inner shelf (<40 m) was richer and more productive than the combined middle shelf (40-80 m) and the outer shelf (> 80 m), accounting for 70% (395 gC M-2 y-1) of Texas-Louisiana shelf primary production. There were marked east-west gradients in both chlorophyll a and primary production; highest values were found close to the Mississippi River delta and the lowest values were off the Texas coast. The vertical distribution of chlorophyll a was characterized by the presence of subsurface chlorophyll maxima. The positions of the chlorophyll maxima either corresponded with the depth of 1-4% of the surface light level or the top of the nutricline. Seasonally, biomass and primary production showed the highest values in the -winter of 1993 and the lowest values in the summer of 1992, and there was also strong interannual variability in standing crop and primary production in May 1992 compared with May 1993. The contribution of the net- (>20 gm) , nano- (<20 gm and >1 gm), and pi- oplankton (<Igm)'showed considerable variation spatially and temporally. The nanoplankton-sized spectrum dominated the phytoplankton population along the TexasLouisiana shelf, contributing averages of 59% and 50% to the standing crop and primary production, respectively. The picoplankton contribution was nearly half that of the nanoplankton; the averages for the standing crop and primary production were 27%, and 25%, respectively. Netplankton accounted for only 14% of the standing crop and 25% of the primary production. The diatoms dominated the phytoplankton population during spring and winter, with the highest contribution (91 % of the catch) reported from the inner shelf. The proportion of diatoms decreased during the summer, when blooms of the blue-green alga Trichodesmium thiebautii were abundant, especially in the outer shelf Principal Component Analysis (PCA) showed a higher correlation between the nutrient input from the Mississippi and Atchafalaya rivers than any of the physical, chemical, and biological factors governing phytoplankton distribution and production on the Texas-Louisiana shelf. |
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| Item Description: | Vita. "Major Subject: Oceanography". |
| Physical Description: | xiv, 177 leaves : illustrations, maps ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |