Theses and Dissertations

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Defense Date

2003

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology

First Advisor

Scott Schatz

Second Advisor

Harold Laubach

Third Advisor

Andrew Rogerson

Abstract

Ergosterol analysis techniques are relatively new methods for measuring fungal biomass. Ergosterol is a sterol found in the plasma membrane of eumycotic fungal cells. It is unique to higher filamentous fungi and is not found in the plasma membrane of other eukaryotes. Thus, quantifying fungal biomass can be achieved by isolating ergosterol. The purpose of this study was to measure seasonal changes in fungal biomass in intertidal and submerged wood substrates in a South Florida mangrove ecosystem by ergosterol analysis. In addition, fungal species were identified within a South Florida mangrove forest along the Loxahatchee River.

Mesh bags containing four different substrates were placed along Whiskey Creek in John U. Lloyd State Park, Florida The four substrates were Red Oak wood, Quercus rubra, Yellow Pine wood, Pinus leiophylla, Red Mangrove wood, Rhizophora mangle, and R. mangle leaves. Mesh bags were placed in the intertidal zone in January, March, May, and September of 2002 and ergosterol levels were measured each month for the four different substrates. Another set of the four different substrates was completely submerged in August 2002, and ergosterol measurements were recorded monthly.

Seasonally, it was found that ergosterol levels were higher in the late spring and early summer months. This might be due to the higher water levels in the winter and fall, which increased competition for the available substrates. Ergosterol levels were noticeably lower in the submerged Red Mangrove leaves as compared to the intertidal Red Mangrove leaves. Newell (1997) found similar results and concluded that leaves in the upper intertidal zone that are exposed to periodic desiccation might favor eumycotic fungal growing conditions, whereas Oomycetes, a mycelial protist, might out-compete higher filamentous fungi in submerged leaves.

The marine mangrove fungi found along the Loxahatchee River were similar to the mangrove species reported in previous tropical and subtropical studies. The majority (73%) of species was Ascomycetes. The dominant species were Marinosphaera mangrovei, Hypoxylon oceanicum, Cytospora rhizophorae, and Caryosporella rhizophorae. These species are commonly found on Rhizophora mangle.

Noticeable trends in seasonal fungal distributions, in addition to differences in fungal biomass between submerged and intertidal mangrove leaves, were evident during the course of this study. Fungi have been shown to play an important role in nutrient recycling within mangrove ecosystems. This study demonstrated that ergosterol methods are appropriate for the study of mangrove fungi. Future studies will likely provide greater insights into the activities of filamentous marine fungi in estuarine and near-shore ecosystems.

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