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Zooplankton community composition an...

Conroy, Brandon Judd.

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Zooplankton community composition and grazing in the Amazon River plume and western tropical North Atlantic Ocean.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Zooplankton community composition and grazing in the Amazon River plume and western tropical North Atlantic Ocean./
Author:	Conroy, Brandon Judd.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2016,
Description:	182 p.
Notes:	Source: Dissertation Abstracts International, Volume: 78-02(E), Section: B.
Contained By:	Dissertation Abstracts International78-02B(E).
Subject:	Biological oceanography. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10147094
ISBN:	9781369023909

Zooplankton community composition and grazing in the Amazon River plume and western tropical North Atlantic Ocean.
Conroy, Brandon Judd.

Zooplankton community composition and grazing in the Amazon River plume and western tropical North Atlantic Ocean. - Ann Arbor : ProQuest Dissertations & Theses, 2016 - 182 p.

Source: Dissertation Abstracts International, Volume: 78-02(E), Section: B.

Thesis (Ph.D.)--The College of William and Mary, 2016.

Large river plumes and frontal zones are important physical features influencing plankton distribution in the marine environment. In the western tropical North Atlantic Ocean (WTNA) the Amazon River plume may extend over an area reaching 1.5 x 106 km2. The freshwater plume creates a low-density lens in the surface 25m and supplies silicon and phosphorus to the WTNA. These physical and chemical gradients create an ideal environment for large-scale blooms of diatom diazotroph associations (DDAs), a symbiotic relationship between nitrogen-fixing cyanobacteria and chain-forming diatoms. While the physical and chemical properties of the plume with regard to influences on phytoplankton have been reported, zooplankton distributions and the fate of enhanced primary production in the plume are largely unknown. I investigated mesozooplankton (>200 mum) composition and grazing in the Amazon River plume-influenced WTNA in spring (May-June 2010) and fall (Sept.-Oct. 2011). Changes in zooplankton distribution and grazing occurred over the sea surface salinity (SSS) gradient from low salinity and mesohaline plume waters to high salinity oceanic waters. Distinct communities were identified in each season along the salinity gradient with several taxa primarily constrained in the surface plume waters (e.g., Lucifer faxoni). The plume appears to function as an "extended estuary", with a number of taxa (e.g., decapods, euphausiids, and fish larvae) utilizing the plume as a nursery habitat or dispersal mechanism for larval stages. Mesozooplankton grazing was elevated in plume waters compared to oceanic waters and was 2-3 times higher in the fall vs. spring. These patterns suggest a lag in the peak mesozooplankton abundance and grazing in response the observed spring DDA bloom, at least in low salinity plume waters. Comparison of micro- and mesozooplankton grazing along the SSS gradient supported a transition from an "export" food web in waters with SSS < 33 where mesozooplankton grazing dominated and potential for export via fecal pellet production is higher, to a "retention" food web at SSS above 33 where microzooplankton grazing was highest and recycling of nutrients in surface waters is predicted. Using molecular techniques to investigate feeding on DDAs and other N- fixers, I found that copepods consumed DDAs (Hemialus-Richelia and Rhizosolenia- Richelia , diatom-diazotroph respectively) as well as the colonial cyanobacterium Trichodesmium. Investigation of mesozooplankton grazing more broadly on other cyanobacteria with 16S rRNA sequencing revealed consumption of Synechococcus, Prochlorococcus, and the unicellular diazotroph UCYN-A Candidatus Atelocyanobacterium thalassa. Together, these results have important implications for our understanding of biogeochemical cycling in the WTNA, and other regions with abundant DDAs (e.g., the Mekong and Congo River plumes).

ISBN: 9781369023909Subjects--Topical Terms:

2122748
Biological oceanography.

Zooplankton community composition and grazing in the Amazon River plume and western tropical North Atlantic Ocean.
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245 1 0 $a Zooplankton community composition and grazing in the Amazon River plume and western tropical North Atlantic Ocean.
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300 $a 182 p.
500 $a Source: Dissertation Abstracts International, Volume: 78-02(E), Section: B.
500 $a Adviser: Deborah K. Steinberg.
502 $a Thesis (Ph.D.)--The College of William and Mary, 2016.
520 $a Large river plumes and frontal zones are important physical features influencing plankton distribution in the marine environment. In the western tropical North Atlantic Ocean (WTNA) the Amazon River plume may extend over an area reaching 1.5 x 106 km2. The freshwater plume creates a low-density lens in the surface 25m and supplies silicon and phosphorus to the WTNA. These physical and chemical gradients create an ideal environment for large-scale blooms of diatom diazotroph associations (DDAs), a symbiotic relationship between nitrogen-fixing cyanobacteria and chain-forming diatoms. While the physical and chemical properties of the plume with regard to influences on phytoplankton have been reported, zooplankton distributions and the fate of enhanced primary production in the plume are largely unknown. I investigated mesozooplankton (>200 mum) composition and grazing in the Amazon River plume-influenced WTNA in spring (May-June 2010) and fall (Sept.-Oct. 2011). Changes in zooplankton distribution and grazing occurred over the sea surface salinity (SSS) gradient from low salinity and mesohaline plume waters to high salinity oceanic waters. Distinct communities were identified in each season along the salinity gradient with several taxa primarily constrained in the surface plume waters (e.g., Lucifer faxoni). The plume appears to function as an "extended estuary", with a number of taxa (e.g., decapods, euphausiids, and fish larvae) utilizing the plume as a nursery habitat or dispersal mechanism for larval stages. Mesozooplankton grazing was elevated in plume waters compared to oceanic waters and was 2-3 times higher in the fall vs. spring. These patterns suggest a lag in the peak mesozooplankton abundance and grazing in response the observed spring DDA bloom, at least in low salinity plume waters. Comparison of micro- and mesozooplankton grazing along the SSS gradient supported a transition from an "export" food web in waters with SSS < 33 where mesozooplankton grazing dominated and potential for export via fecal pellet production is higher, to a "retention" food web at SSS above 33 where microzooplankton grazing was highest and recycling of nutrients in surface waters is predicted. Using molecular techniques to investigate feeding on DDAs and other N- fixers, I found that copepods consumed DDAs (Hemialus-Richelia and Rhizosolenia- Richelia , diatom-diazotroph respectively) as well as the colonial cyanobacterium Trichodesmium. Investigation of mesozooplankton grazing more broadly on other cyanobacteria with 16S rRNA sequencing revealed consumption of Synechococcus, Prochlorococcus, and the unicellular diazotroph UCYN-A Candidatus Atelocyanobacterium thalassa. Together, these results have important implications for our understanding of biogeochemical cycling in the WTNA, and other regions with abundant DDAs (e.g., the Mekong and Congo River plumes).
590 $a School code: 0261.
650 4 $a Biological oceanography. $3 2122748
650 4 $a Ecology. $3 516476
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710 2 $a The College of William and Mary. $b School of Marine Science. $3 3281332
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