Cladophora glomerata is the dominant spring and summer epilithic macroalga in the lower Laurentian Great Lakes, and was a notorious nuisance prior to nutrient management of the early 1970s. It is an indicator of excessive nutrient supply and appears to be experiencing a resurgence in the nearshore of the lower Great Lakes. This thesis examines the ecology of C. glomerata in an urbanized location of Lake Ontario and addresses decadal scale environmental changes to the lake and their impact on this macroalga. A Cladophora growth model (CGM) was calibrated and validated to simulate attached and sloughed Cladophora biomass using two years of collected input data and independent measurements of Cladophora biomass. The CGM was used to hindcast Cladophora growth using multiplicative factors of seasonal minimal tissue phosphorus concentrations (QP) and seasonal mean nearshore light attenuation (KdPAR) of the early 1970s and 1980s relative to contemporary data. Cladophora QP in Lake Ontario is currently lower than in the early 1980s, resulting in reduced Cladophora biomass at all depths in the euphotic zone. KdPAR has also declined, most strongly since the mid-1990s, following Dreissena mussel invasion, driving an increase in macroalgal biomass between 3.5 and 10 m depth. Combining these effects, the CGM predicted that biomass is currently lower in Lake Ontario than in the early 1980s. However, increases in QP in this post-dreissenid mussel period are predicted to result in greater Cladophora proliferation than in previous decades due to increased nearshore water clarity. The in situ rates of primary production on Cladophora-dominated rocky substrata at 1m depth were measured through the spring and summer. Net primary production (NPP) was measured as change in dissolved inorganic carbon (using IRGA) in benthic incubation chambers flushed continuously with water. Incubations were of 15- 20 minutes duration, permitting measurements of productivity rates over diurnal and seasonal scales. Maximum biomass-specific net photosynthetic rates (PBmax) were highest in the spring and late-summer/fall (2.39, 1.98 mgC gDM-1 hr-1, respectively) and decreased to negative rates by early summer (−0.76 mgC gDM-1 hr-1). Directly measured rates of net primary production were simulated with the CGM. Simulated depth-integrated rates of Cladophora primary production were compared with published depth-integrated measurements of planktonic primary production from Lake Ontario. From the shoreline to the 12 m depth contour, the benthos was estimated to contribute 70% of the areal primary production. On a seasonal basis, attached macroalgae are an important component of the energy flux in the Lake Ontario nearshore. This phenology of Cladophora glomerata growing in the western end of Lake Ontario is also described. Based on internal stoichiometric ratios (C:P and N:P), and a positive correlation between the decrease in the biomass-specific maximum photosynthetic rate (PBm) and phosphorus quota (QP), Cladophora productivity at shallow depths was shown to be P limited. In addition, light attenuation through the Cladophora canopy was estimated to be 24.1 ± 3.3 (standard deviation) m-1 using paired light loggers deployed in situ. Acclimation to lower light levels through the Cladophora stand was demonstrated by significantly higher Cladophora chlorophyll concentrations at the base of the canopy. Decreases in Cladophora canopy cover in the summer resulted in increased PBm, even when QP remained near the minimal cell quota, indicating potential co-limitation of Cladophora productivity by light during peak standing crop. Cladophora growing at 1m depth was also shown here to be tolerant of high irradiance, with an average decline of less than 10% in Fv/Fm at during peak midday insolation, regardless of nutrient status or ambient water temperature. In conjunction with its role as a seasonally important nearshore primary producer, Cladophora appears to play a role as a seasonal nutrient regulator in the nearshore of Lake Ontario. The nutrient chemistry of nearshore lake water, Cladophora tissue, and a dominant tributary to western Lake Ontario were examined over the growing season of 2 years. As Cladophora grew and assimilated nutrients in the spring, total phosphorus (TP) and soluble reactive P (SRP) concentrations declined in the nearshore. Detachment and sloughing of Cladophora in the late summer was associated with increasing TP in the water column. These changes in nearshore nutrient concentrations were correlated with Cladophora phenology and not catchment loading. Nutrient loading from Oakville Creek was compared with the nutrient uptake of an adjacent Cladophora stand. The TP supply directly from the creek during the growing season was insufficient to meet the concentration of stored P in Cladophora tissue. It appears Cladophora is growing on P regulated by recycling within the lake, supporting the hypothesis that dreissenid mussels are sustaining Cladophora growth through recycling of TP in the lake. Cladophora remains P limited, however, such that increases in catchment loading would further augment its resurgence.

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Thesis (Ph. D.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains xii, 162 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 98-99).

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2005. / Includes bibliographical references.

Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2005. / Includes bibliographical references.

Thesis (doctoral)--Universität Bremen, 2006. / Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 200-215). Available also in a digital version from Dissertation Abstracts.

The objective of this study was to obtain a bioassessment using benthic macroinvertebrates to meet TMDL (Total Maximum Daily Load) criteria for an oligotrophic (Lake Seminary) and an eutrophic (Lake Jesup) freshwater system in Seminole County, Florida. Monthly sampling of the benthic macroinverterbrate communities provided important biological data necessary to construct TMDL protocol and trophic state. Since macroinvertebrates are near the base of the food chain, they not only provide a critical role in the natural flow of energy and cycling of nutrients through the food web, but also provide a good indication of water quality by their presence and abundance. This study suggests that TMDL protocol and reversal trends in eutrophication can be successfully monitored using benthic macroinvertebrate data. Comparative methodology between the LCI and conventional methods indicate that the LCI is a valid, cost-effective and rapid bioassessment method when compared to the conventional method and that the conventional method is an effective tool when more in depth benthic studies are needed as it shows distinct seasonal patterns and accounts for more of the sensitive, intolerant taxa. Furthermore, this type of biological monitoring and trend analysis aids in the implementation of anthropogenic controls that targets waters for TMDLs in suspect systems. When integrated within a watershed management plan, multi-metric indexing functions as an effective overall indicator of the biological condition within a waterbody responding to its watershed.

The relative sensitivities of four benthic invertebrates (𝘏𝘺𝘢𝘭𝘦𝘭𝘭𝘢 𝘢𝘻𝘵𝘦𝘤𝘢, 𝘊𝘩𝘪𝘳𝘰𝘯𝘰𝘮𝘶𝘴 𝘳𝘪𝘱𝘢𝘳𝘪𝘶𝘴, 𝘏𝘦𝘹𝘢𝘨𝘦𝘯𝘪𝘢 spp., and 𝘛𝘶𝘣𝘪𝘧𝘦𝘹 𝘵𝘶𝘣𝘪𝘧𝘦𝘹) were determined separately for cadmium, copper, and nickel in 96-hour water-only and in spiked sediment exposures. Survival (LC25's and LC5O's), growth and reproduction (IC25's) endpoints were compared amongst the four species. In the water-only tests, 𝘏. 𝘢𝘻𝘵𝘦𝘤𝘢 is the most sensitive species to cadmium and nickel, with mean LC5O's of 0.013 and 3.6 mg/L respectively, and 𝘊. 𝘳𝘪𝘱𝘢𝘳𝘪𝘶𝘴 is the most sensitive species to copper, with a mean LC5O of 0.043 mg/L. In the spiked sediment exposures, 𝘏𝘦𝘹𝘢𝘨𝘦𝘯𝘪𝘢 spp. is most sensitive species to copper with a mean LC5O in sediment of 93 μg/g and a mean IC25 of 38 μg/g, and 𝘏. 𝘢𝘻𝘵𝘦𝘤𝘢 is most sensitive species to cadmium and nickel, with mean LC5O's of 33 and 67 μg/g respectively and mean IC25's of 10 and 40 μg/g respectively. Overall, 𝘛. 𝘵𝘶𝘣𝘪𝘧𝘦𝘹 is the least sensitive species to all metals tested, and the number of young produced/adult is the most sensitive of the reproduction endpoints for 𝘛. 𝘵𝘶𝘣𝘪𝘧𝘦𝘹. The relative sensitivities reveal that two endpoints, 𝘊𝘩𝘪𝘳𝘰𝘯𝘰𝘮𝘶𝘴 and 𝘏𝘦𝘹𝘢𝘨𝘦𝘯𝘪𝘢 survival, can be used to possibly distinguish between cadmium, copper, and nickel metal toxicity. Species test responses in field-collected sediments from areas contaminated primarily by the above mentioned metals were compared to the determined sensitivities in order to establish the causative agent of toxicity. Sediment toxicity was categorized first by comparing species responses to those established for a reference database. Responses in the field sediment support suspected toxicant in some cases, but not others. Multivariate analyses were used to assess sediment toxicity in the field sites based on the species responses, and these analyses reveal that the test endpoints respond to different environmental variables in ordination space. A comparison of test responses in the field sites to those in reference sites in ordination space reveals 13 of the 15 field-collected sites to be toxic or severely toxic. / Thesis / Master of Science (MS)