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An experimental study of the role of...

Marino, Roxanne.

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An experimental study of the role of phosphorus, molybdenum, and grazing as interacting controls on planktonic nitrogen fixation in estuaries.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	An experimental study of the role of phosphorus, molybdenum, and grazing as interacting controls on planktonic nitrogen fixation in estuaries./
作者:	Marino, Roxanne.
面頁冊數:	215 p.
附註:	Adviser: Gene E. Likens.
Contained By:	Dissertation Abstracts International61-11B.
標題:	Biogeochemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9995140
ISBN:	0493023577

An experimental study of the role of phosphorus, molybdenum, and grazing as interacting controls on planktonic nitrogen fixation in estuaries.
Marino, Roxanne.

An experimental study of the role of phosphorus, molybdenum, and grazing as interacting controls on planktonic nitrogen fixation in estuaries. - 215 p.

Adviser: Gene E. Likens.

Thesis (Ph.D.)--Cornell University, 2001.

Heterocystic cyanobacteria respond to low nitrogen (N) availability in nutrient-enriched lakes by fixing N2, but these organisms are rare in the plankton of nearly all estuaries worldwide under similarly N-depleted conditions. Due partially to the absence of these cyanobacteria from saline estuaries, little is known about the factors which might differentially exclude them. In this dissertation, an experimental system was developed in which heterocystic, N2-fixing cyanobacteria were grown under saline estuarine conditions in 3000-liter tanks. These mesocosms were used for three experiments exploring the interaction of biogeochemical and ecological controls on cyanobacterial N2 fixation.

ISBN: 0493023577Subjects--Topical Terms:

545717
Biogeochemistry.

An experimental study of the role of phosphorus, molybdenum, and grazing as interacting controls on planktonic nitrogen fixation in estuaries.
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245 1 0 $a An experimental study of the role of phosphorus, molybdenum, and grazing as interacting controls on planktonic nitrogen fixation in estuaries.
300 $a 215 p.
500 $a Adviser: Gene E. Likens.
500 $a Source: Dissertation Abstracts International, Volume: 61-11, Section: B, page: 5760.
502 $a Thesis (Ph.D.)--Cornell University, 2001.
520 $a Heterocystic cyanobacteria respond to low nitrogen (N) availability in nutrient-enriched lakes by fixing N2, but these organisms are rare in the plankton of nearly all estuaries worldwide under similarly N-depleted conditions. Due partially to the absence of these cyanobacteria from saline estuaries, little is known about the factors which might differentially exclude them. In this dissertation, an experimental system was developed in which heterocystic, N2-fixing cyanobacteria were grown under saline estuarine conditions in 3000-liter tanks. These mesocosms were used for three experiments exploring the interaction of biogeochemical and ecological controls on cyanobacterial N2 fixation.
520 $a The hypothesis tested was that planktonic cyanobacterial growth in seawater slow, due to sulfate inhibiting the availability of molybdenum, a trace metal required for N2 fixation; slow growth leaves a developing population susceptible to control by grazing. Mesocosms were enriched with phosphorus (P) to provide a low N:P ratio, known to stimulate planktonic N2 fixation in freshwaters, and in one experiment with molybdenum. Grazing pressure was manipulated using zooplanktivorous fish or a benthic filter-feeder. Grazing suppressed both heterocyst abundance and total N increase. The cyanobacterial response to P availability, both absolute and relative to N, was not as strong as observed in freshwater systems, and was insufficient to overcome the grazing effect and ecosystem N limitation, indicating another constraint on growth and N2 fixation.
520 $a Molybdenum additions (10X seawater) affected heterocyst abundance or N2 fixation inputs less than expected, and were insufficient to stimulate rapid enough growth to overcome grazing control. A microcosm experiment with freshwater <italic>Anabaena</italic> confirmed a strong inhibition of N2 fixation at seawater sulfate and molybdenum levels, and showed a similarly small reversal of that effect at higher molybdenum. A re-examination of published kinetic data used to design these experiments suggested that the influence of sulfate on molybdenum assimilation is not entirely reversible, as assumed using a simple, single-enzyme competitive inhibition model. Nonetheless, these experiments support the hypothesis that a bottom-up constraint on growth of heterocystic cyanobacteria (molybdenum), coupled with an ecological interaction (grazing), can significantly reduce the ability of heterocystic, N2-fixing cyanobacteria to eliminate N deficits in nutrient-enriched, saline estuarine ecosystems.
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650 4 $a Biology, Limnology. $3 1018638
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