Branching frequency of Thalassia testudinum (Banks ex K?nig) as an ecological indicator in Florida Bay

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Jill C. Paxson (Creator)
The University of North Carolina Wilmington (UNCW )
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Abstract: The effects of short-shoot density and light availability on rhizome apical meristem density and rhizome branch frequency of Thalassia testudinum were assessed in ten basins in Florida Bay. Core samples for density measurements were obtained from 27-30 stations per basin (over 300 sampling stations total) during the spring 1998 and spring 1999 sampling of the Fish Habitat Assessment Program (FHAP). Rhizome branch frequency (apicals short-shoots-1) was calculated from the core data. Light attenuation, (Kd), estimated from in situ measurements of secchi depths, light profiles of scalar irradiance and Kd values calculated from AVHRR satellite imagery using GIS indicated high light availability and similar optical water quality between the two years. Light attenuation estimates were coupled with USGS bathymetry to determine if there was a significant interaction between light availability and Thalassia densities or rhizome branching. Apical density and short-shoot density were linearly correlated in Florida Bay. Neither apical density nor rhizome branch frequency in 1998 was found to be a good predictor of short-shoot density fluctuations between the spring of 1998 and 1999. Increases in rhizome branch frequencies were only weakly associated with between-year increases in short-shoot densities in this study. Mean rhizome branch frequencies were 0.19 + 0.02, and 0.15 + 0.01, for spring 1998 and spring 1999, respectively. The relatively lower rhizome branching rates observed in Florida Bay in 1998 and 1999 may reflect a density-dependent inhibitory response due to the increase in short-shoot densities following the seagrass die-off from 1990 to 1998 (305 short shoots/m2 in 1990, Durako 1995 versus 590 & 602 short shoots/m2 in this study). There was a positive relationship between percent surface irradiance and short-shoot density. In conclusion, rhizome branch frequency was not a good ecoindicator of light availability or short-shoot density changes in Florida Bay. In contrast, it appears that the effect of short-shoot density, which did respond positively to increasing light availability, may be more important in effecting rhizome branching. Therefore, rhizome branch frequency may be a biological indicator that responds to short-shoot density changes in this non-light limited Bay.

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Seagrasses--Florida--Ecology, Seagrasses--Florida--Florida Bay, Thalassia--Florida--Florida Bay
Seagrasses -- Florida -- Florida Bay
Seagrasses -- Florida -- Ecology
Thalassia -- Florida -- Florida Bay

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