Date of Award

6-1998

Type

Thesis

Major

BS/MS Environmental Science

Department

Earth & Space Science

First Advisor

James A. Gore

Abstract

A survey of the macroinvertebrate and crustacean assemblages in hydric pine flatwood wetlands during fill and drawdown periods was conducted from September to November 1998, in Lee County, Florida. Physical and chemical information, relationships between community composition and physical and chemical conditions were analyzed and a monitoring plan for detecting impacts of declining water supply in hydric pine flatwood communities was proposed. In addition, possible sources of colonists and patterns of community assemblage were investigated. Twelve ephemeral pools and three associated intermittently exposed cypress heads were sampled monthly, over three months, using 1 D-ring benthic sweep, 2 Hester-Dendy multiple plate artificial substrates, 2 bottle brush artificial substrates, and 1 funnel trap per site. Bray-Curtis based ordinations and cluster analysis revealed significant dissimilarity between and among macroinvertebrate, chironomid, and crustacean assemblages in ephemeral pool and intermittently exposed cypress head habitats at distances within 200 meters. A Principle Components Analysis (PCA) of non-chironomid macroinvertebrate assemblages and the physical and chemical parameters measured revealed that the distribution of the taxa collected could not be significantly correlated with any of the physical or chemical criteria. The pattern of colonization of the temporary wetlands within the Flint Pen Strand hydric pine flatwoods mimics those for invasion of isolated islands in the world's oceans. Species invasion is rapid by active dispersers and slightly slower by passive dispersers. Colonization is dependent upon distance to the recipient islands, both spatially and temporally, and the number of intervening "stepping-stone islands" acting as temporary refugia. The isolated island effect is not constant in the hydric pine flatwood sites. During the initial rainy season, there is probably a surface water connection from the more persistent water bodies to the hydric pine wetland. However, as the dry season proceeds, the more distant sites become hydrologically isolated. The macroinvertebrate fauna of the temporary wetlands associated with the hydric pine flatwoods represent unique associations different from those of semi-permanently flooded or intermittently exposed bodies of water. Cluster analysis of non-chironomid macroinvertebrate, chironomid, and crustacean assemblages support this conclusion. From the cluster analysis, a species list of abundant and common species expected in the represented zones was created. Although a number of different types of artificial substrates were put to use, the standard D-ring dip net is the suggested methodology to provide a composite sample necessary to determine the health of these ecosystems. Since chironomids have been shown to be indicators of changes in water quality and this study indicates that they are representative of the various changes in distance from source, area, and volume effects, concentration on this taxon is suggested for future monitoring. Taxa such as dragonflies, damselflies, Caenis sp., Ablabesmyia rhamphe grp., and Zavreliella marmorata could be expected to be indicators of adequate wetland conditions. In the larger wetland areas, the loss of longer-lived species, like the dragonflies and mayflies, indicate drydown effects, as does an increase in semi-aquatic forms, like the Collembola and Ceratopogonidae.

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