Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains x, 157 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Conversion to agriculture, land fragmentation, and removal of native grazers have made tallgrass prairies and the streams that drain them one of the most imperiled systems on earth. Patch-burn grazing (PBG), an increasingly common management practice on remaining prairie parcels, has been shown to benefit cattle and grassland birds. However, potential influences of this practice on streams are unknown. To address this, we sampled stream macroinvertebrates and benthic organic matter two years before and three years during PBG on two watersheds with riparian fencing (fenced), two grazed watersheds without riparian fencing (unfenced), and two ungrazed (control) watersheds. Very fine benthic organic matter increased 51% in unfenced watersheds after implementation of PBG, accompanied by a threefold increase in fine organic sediments in the same watersheds. Contribution of fine inorganic sediments to total substrata increased 28% in unfenced watersheds during PBG, while fine inorganic sediments decreased in both the control (18%) and fenced (16%) watersheds. Increases in the contribution of Chironomidae to total macroinvertebrate abundance (18% before, 49% during PBG) and biomass (10% before, 19% during PBG) were evident in unfenced streams. In contrast, abundance of sensitive EPT taxa decreased an order of magnitude from 7,635 to 687 individuals m-2 in unfenced streams, but did not change in fenced and control streams. Increases in tolerant taxa and fine organic and inorganic sediments, along with reductions in metrics of biotic integrity, suggest PBG adversely impacts prairie streams. However, the absence of negative responses in fenced watersheds indicates that riparian fencing can mitigate these impacts by serving as a buffer to prevent excess sedimentation. In order to properly manage remaining tallgrass prairie parcels, it is important to consider both the aquatic and terrestrial components of these systems, as they are tightly linked. Results from this study provide a basis for management and policy decisions regarding remaining grassland watersheds.

The aim of the study was to examine if the benthos in a restored portion of a small lowland stream south of Linkoping differed from two non restored reference areas two years after restoration. The reference areas were one stretch downstream and one upstream stretches of the restored stream. The benthic invertebrates were collected using standardized kick sampling. In order to classify the communities and estimate any differences, three different indices were exercised. In addition rank-abundance curves and checklists were used to get a picture of species composition. The only index that showed a difference between areas was the Berger-Parker diversity index showing that the downstream reference stretch differed from the other two. None of the analyses showed that the restored area was different from the other two, probably due to too short a time since the restoration. To allow for the bottom substrate to develop and stabilize so that species can re-colonize the area.

Univ., Diss.--Göteborg, 2007. / Enth. außerdem 5 Zeitschriftenaufsätze.

Thesis (PhD)--Göteborg University, c2007. / A collection of papers by the author, some with co-authors. Includes bibliographical references.

Coastal hydrodynamics regulate population dynamics through the distribution and dispersal of the meroplankton of many benthic invertebrates. I examined the hydrodynamics at four different sites on the south-east coast of South Africa and coupled them with larval sampling done at high temporal and spatial resolution. Day and night sampling was done at all four sites and a continuous 24 hour study was done in one site, both forms of sampling were carried out in autumn and spring. Samples were taken at two stations, 900 metres offshore and 300 metres apart, within each site. Water properties measured were depth, temperature and current velocity and direction. Plankton samples were collected using a plankton pump at various depths, from the surface, bottom and either side of the thermocline when present. A wide range of taxa (mostly bryozoans, bivalves, barnacles and decapods) was examined. 2-way ANOVAs were used to test the effects of time and depth on each taxon. In addition, multiple regression analyses were performed on each taxon to investigate the effects of hydrodynamics on the distribution of larvae. Bryozoanlarvae proved to be positively phototactic whilst bivalve veligers, barnacle larvae and decapod zoeae performed diel vertical migration. Turbulence and temperature had an effect on the vertical distribution/migration of decapod zoeae. These results highlight the role of taxon-specific responses to flow and the potential differential effects on larval retention and ultimately connectivity of benthic populations.

Benthic filter feeders have a key functional role in the dynamics of coastal food web as an intermediate trophic level and bioengineers. A wide variety of factors, operating across multiple spatial scales (e.g. hydrographic regime, human activities), can affect the composition of the water column and thus the availability of food for benthic populations. Food availability in turn affects the growth, reproductive rates and survival of benthic organisms, and consequently, can influence the functioning of the entire ecosystem. This study aims to evaluate how various environmental factors may modify the diet of intertidal filter feeders living along the South African coast. Specifically, the effects of biogeography, upwelling, urbanization and freshwater input on the dietary regimes of five species of filter feeders (two mussel and three barnacle species) were investigated using fatty acid (FA) and stable isotope (SI) analyses.Strong interspecific differences were found among the five species considered. However, all species responded to factors operating at large (100s km) and meso (10s- 100s km) scales (i.e. biogeography and upwelling respectively). The barnacles exhibit habitat segregation and showed different FA and SI signatures from each other, while the two mussel species, an invasive and native species that co-occur in the same mussel beds, had partially overlapping diets. Differences in their diets were found only using FA analysis, while their SI signatures differed on only one occasion. This highlights the importance of using the appropriate tool, and ideally combined techniques, to investigate diets.FA and SI signatures of all species considered changed among the three biographical provinces (west, south and east coasts of South Africa) exhibiting similar patterns that reflect the two oceanographic regimes that characterize the coastline: the eutrophic Benguela Current on the west coast and the oligotrophic Agulhas Current on the other two coasts. Upwelling had a significant effect on FA and SI signatures, with stronger effects on the west coast than the south coast. The results indicate that benthic filter feeders at upwelling areas consumed a mix of coastal macroalgal detritus and phytoplankton, which was probably brought onshore during downwelling events. At smaller spatialscales and using repeated sampling, the influence of upwelling on the west coast was found to be pervasive, rather than discrete, so that it may be more appropriate to categorize upwelling by referring to upwelling centres and downstream areas. SI underlined a significant effect of urbanization on the diet of filter feeders with an enrichment in the δ¹⁵N being characteristic of anthropogenic effect. Although a large number of rivers characterize the South African coast, no distinct effect of freshwater input was found for either the SI or FA signatures of the filter feeders. This contrasts with earlier work on demersal species and suggests that freshwater input does not significantly affect food availability for intertidal filter feeders, and that other factors (e.g. hydrogeography) are more important in determining the diet of these populations. These results highlight that environmental and anthropogenic factors operating at different spatial and temporal scales have a profound effect on benthic ecosystems, and that they control the relationship between primary production and primary consumers in coastal areas. Above all, this work highlights the importance of understanding the spatial and temporal scales at which different factors affect feeding regimes, and their critical role in coastal food webs.

No description available.

No description available.

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.