Biology Theses and Dissertations
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Item STUDIES OF PERIPHYTIC ALGAE ON ALGAL TURF SCRUBBERSTM ALONG THE CHESAPEAKE BAY: COMMUNITY STRUCTURE, SYSTEMATICS, AND INFLUENCING FACTORS(2012) Laughinghouse, Haywood Dail; Kangas, Patrick C; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This is an ecological and systematic study of periphytic algae growing in an ecologically-engineered system used for water quality improvement: the Algal Turf Scrubber or ATSTM. This technology consists of an attached algal community growing on screens in a shallow floway through which water is pumped. The study was conducted on small-scale, experimental floways at three sites within the Chesapeake Bay watershed: on the Susquehanna River in southeastern Pennsylvania (freshwater) and on the Great Wicomico and York Rivers in Virginia (brackish water). A total of 330 taxa were identified at the sites from 2008-2011. The majority of taxa at all three sites belonged to the phylum Bacillariophyta, but a large number of taxa from Chlorophyta and, to a lesser degree, Cyanobacteria were also found at the freshwater site. Algae found in the ATSTM exhibited a diversity of life forms and modes of attachment within the community. Although these system appear to be dominated by a "canopy" of attached, filamentous species, more than half of the total abundance (cell density) were solitary, unattached taxa that grow as an "understory" within the three dimensional structure of the community. Longitudinal patterns were examined on the longest floways (90 m long) at the freshwater site. The community nutrient uptake rate (mass of nitrogen or phosphorus m-2 day-1) for the harvested algal biomass was found to decline from the top to the bottom of the floway for a system constructed at 2% slope but no distinct pattern was found for a system constructed at 1% slope. The majority of algal taxa were evenly distributed along the floway from top to the bottom, in terms of frequency of occurrence, suggesting a general lack of longitudinal specialization within the community. A detailed review of the systematics of the Order Oscillatoriales (Cyanobacteria) found on the ATSTM was undertaken since this group has not been studied much in the Chesapeake Bay watershed. Twenty-four taxa were examined, described morphologically and their nomenclature reviewed. Comparing 16s rRNA gene analyses of planktonic and periphytic Pseudanabaena, it was suggested that periphytic Pseudanabaena be revised and elevated to a new genus, Ilyonema.Item PATTERNS OF WETLAND PLANT SPECIES RICHNESS ACROSS ESTUARINE RIVER GRADIENTS(2009) Sharpe, Peter James; Baldwin, Andrew H; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)It is widely accepted that in coastal wetlands a negative relationship exists between plant species richness (number of species) and salinity. However, the distribution of species richness across estuarine salinity gradients has not been closely examined. I hypothesized that plant species richness in coastal marshes (i.e., wetlands dominated by herbaceous plants) would follow a non-linear pattern with increased distance (salinity) downriver (Chapter 2). To test this hypothesis I conducted detailed marsh vegetation surveys along ≈ 50 km estuarine river gradients of the Nanticoke and Patuxent Rivers, MD/DE. I further hypothesized that the observed patterns of plant species richness on the Nanticoke and Patuxent Rivers could be accurately predicted by a mid-domain effect (MDE) model independent of measured abiotic factors using RangeModel 5.0 (Chapter 3). Lastly, I theorized that Marsh mesocosms subjected to intermediate salinity and inundation would exhibit significantly higher biomass and plant species richness compared to mesocosms subjected to extreme salt/fresh and flooding regimes utilizing a controlled greenhouse experiment (Chapter 4). I found that plant species richness can vary in both a linear (Patuxent River) and non-linear (Nanticoke River) pattern along an estuarine gradient. The MDE model did not explain a high proportion of the observed richness patterns for either river system compared to abiotic factors like porewater salinity. The controlled marsh mesocosm experiment supported the non-linear pattern of plant species richness observed along the Nanticoke River gradient, but did not show a significant difference in plant biomass or richness/diversity between purely fresh and low-salinity marsh mesocosms (α = 0.05). The results of this research suggest that tidal marsh plant richness/diversity patterns do not always conform to a simple linear relationship with increasing salinity and that the MDE is not as important of a mechanism in these communities compared to porewater salinity or flooding frequency. Furthermore tidal low salinity marshes exposed to elevated salinity and flooding frequencies are likely to see a shift in their plant community structure to more salt tolerant plants and less rich/diverse communities assuming they can accrete at a rate equal to or exceeding the present rates of sea-level rise in the Chesapeake Bay.Item Patterns in Diversity and Distribution of Benthic Molluscs Along a Depth Gradient in the Bahamas(2004-11-15) Dowgiallo, Michael Joseph; Reaka-Kudla, Marjorie L.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Species richness and abundance of benthic bivalve and gastropod molluscs was determined over a depth gradient of 5 - 244 m at Lee Stocking Island, Bahamas by deploying replicate benthic collectors at five sites at 5 m, 14 m, 46 m, 153 m, and 244 m for six months beginning in December 1993. A total of 773 individual molluscs comprising at least 72 taxa were retrieved from the collectors. Analysis of the molluscan fauna that colonized the collectors showed overwhelmingly higher abundance and diversity at the 5 m, 14 m, and 46 m sites as compared to the deeper sites at 153 m and 244 m. Irradiance, temperature, and habitat heterogeneity all declined with depth, coincident with declines in the abundance and diversity of the molluscs. Herbivorous modes of feeding predominated (52%) and carnivorous modes of feeding were common (44%) over the range of depths studied at Lee Stocking Island, but mode of feeding did not change significantly over depth. One bivalve and one gastropod species showed a significant decline in body size with increasing depth. Analysis of data for 960 species of gastropod molluscs from the Western Atlantic Gastropod Database of the Academy of Natural Sciences (ANS) that have ranges including the Bahamas showed a positive correlation between body size of species of gastropods and their geographic ranges. There was also a positive correlation between depth range and the size of the geographic range. Nearly 80% of the species of gastropods in the ANS data set are less than 30 mm in body size, indicating that most gastropods in the Bahamas are small. A relatively high number of species of gastropods in the ANS data set that occur in the Bahamas had geographic ranges that extended into the Eastern Pacific (37%) and into the Brazilian (50%) provinces, though ranges of species tended to show highest densities centered in and near the Caribbean province. One of the more obvious faunal boundaries for the gastropods in the ANS data set was their northernmost limit, around Cape Hatteras, where colder northern water masses converge with the warmer waters of the Gulf Stream.