The near-bottom chlorophyll A maximum in Onslow Bay : effects of wave events on benthic microalgae resuspension
- UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
- Gianluca Manes (Creator)
- Institution
- The University of North Carolina Wilmington (UNCW )
- Web Site: http://library.uncw.edu/
- Advisor
- Daniel Baden
Abstract: Both a significant benthic microflora and a near-bottom chlorophyll a maximum
are present in Onslow Bay, NC. Over 80% of the chlorophyll a is associated with the
sediments, supporting previous findings that primary production by microalgae on the
continental shelf out to the shelf break is important. Benthic microalgae are likely to be
the major producers in continental shelves like Onslow Bay where light flux to the
bottom appears to be adequate to support them.
The existence of a near-bottom chlorophyll a maximum is due partly to
resuspension by surface gravity waves. Orbital velocities and bottom shear stresses
exceeded thresholds of 0.2-0.3 m/s and 0.2 N/m2, respectively, and caused statistically
significant increases in turbidity (NTU) and fluorescence (RFU). In addition to the
magnitude of the orbital velocity measured by Turner SCUFA II in situ loggers the
change in orbital velocity (or bottom shear stress) before and after a storm event, and the
duration of the event also control the resuspension phenomena. However, other processes
such as in situ growth of near-bottom microflora, sinking, and the spring bloom have to
be considered as well in studying formation of near-bottom chlorophyll maxima.
I observed anomalously high values of turbidity and fluorescence at 1 m from the
bottom in May-June 2002 and the lowest concentration of phytoplankton in the water
column (near-bottom, mid-depth, surface) during this event. I hypothesize that demersal
zooplankton moved into the water column at night and reentered the substrate by day and
that holozooplankton were down in the water column near the bottom during the day and
migrated upward at night. These migration patterns were responsible for the fluorescence
and turbidity pattern. The high spikes in turbidity signals at 1 m were probably produced by the high density of zooplankton (~10 4m-2) and the fluorescence signal at 1 m was the
result of their nocturnal feeding (the fluorescence signal was related to the chlorophyll a
content in their guts).
The near-bottom chlorophyll A maximum in Onslow Bay : effects of wave events on benthic microalgae resuspension
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Created on 1/1/2009
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Additional Information
- Publication
- Thesis
- A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Science
- Language: English
- Date: 2009
- Keywords
- Biotic communities--North Carolina--Onslow Bay, Chlorophyll--North Carolina--Onslow Bay, Primary productivity (Biology)--Measurement
- Subjects
- Biotic communities -- North Carolina -- Onslow Bay
- Chlorophyll -- North Carolina -- Onslow Bay
- Primary productivity (Biology) -- Measurement