Extensive data sets of water quality and sediment chemistry as well as detailed historical records were used to analyze environmental factors controlling dinoflagellate cyst distribution in shallow estuaries (lagoons and embayments) of southern New England. Cyst abundance, species richness, the proportion of cysts produced by heterotrophic and autotrophic dinoflagellates, and the composition of cyst assemblages reflect spatial and temporal variation in environmental conditions. The cyst record in sediment cores from two embayments, New Bedford Harbor and Apponagansett Bay, Massachusetts demonstrates cyst sensitivity to environmental change caused by anthropogenic activity in the watersheds. Intensive industrialization and urbanization occurred during the 20th century in New Bedford Harbor resulted in extreme eutrophication and toxic pollution (heavy metals and PCBs). These conditions are reflected in declining cyst diversity and wide fluctuation in total cyst production. At the same time, the proportion of certain heterotrophic taxa increases. As impacts of extreme eutrophication and toxic pollution cannot be separated, the cyst response must be interpreted as a cumulative «pollution signal». The spatial distribution of modern dinoflagellate cysts in the area supports this signal. Cysts vary along gradients of nutrient enrichment, corresponding to distance from sewage outfalls. Dinoflagellate cysts in surface sediments from New England lagoons also were studied. A comparison of assemblages to water quality parameters, that are affected greatly by the degree of water exchange between lagoon and ocean, indicates that temperature and salinity are the main abiotic factors controlling cyst distribution in these estuaries. A new species of dinoflagellate cyst, Islandinium brevispinosum, has been identified and described. This species was found within a narrow range of water temperature and salinity, and at elevated nutrient levels. Dinoflagellate cysts reflect environmental conditions at the small spatial scales necessary to characterize variability within estuaries. However, the relative importance of abiotic factors controlling the spatial and temporal distribution of dinoflagellate cysts is likely to vary with the hydrological differences between lagoons and embayments. Therefore, dinoflagellate cysts can be useful indicators of environmental conditions in and human impacts on shallow estuaries.

Microbiological water quality monitoring of bathing waters does not account for faecal bacteria in sediments. Intertidal deposits are a significant reservoir of faecal bacteria and this indicates there is a risk to human health through direct contact with the sediment, or through the resuspension of bacteria to the water column. This project investigated factors influencing the relative abundance of faecal indicator organisms (FIOs) in intertidal estuarine sediments. The effects of physical, biogeochemical and biological sediment characteristics, environmental variables and native microbial communities were explored through field campaigns on the Ythan and Eden estuaries, Scotland. The contributory role of sediments to adverse water quality was investigated by combining FIO abundance and measurements of sediment stability. The importance of strain and sediment characteristics in the adhesion of E. coli to suspended sediments was also examined using laboratory experiments. E. coli concentrations up to 5.9 log₁₀ CFU 100 g dry wt⁻¹ were observed, confirming that intertidal sediments are an important reservoir of faecal bacteria. The variability of E. coli abundance in estuarine sediments was successfully explained with multiple stepwise linear regression (Adjusted R² up to 87.4) using easily-obtainable measurements of sediment characteristics and environmental variables, with variability most heavily influenced by salinity and particle size gradients. Native microbial community population metrics and community constituent composition correlated with environmental gradients, but did not influence FIO abundance. The amount of E. coli adhering to suspended sediments ranged from 0.02 to 0.74 log₁₀ CFU ml⁻¹, and was dependant on strain characteristics and sediment type rather than zeta potential, with higher cell-particle adhesion at 2 and 3.5 PSU than 0 and 5 PSU. Monitoring of sediment characteristics will lead to more informed bathing water quality advisories to protect public health. Future research should focus on applying the findings here to the modelling of bacterial fate and transport on a catchment scale.

The Incomati River Estuary is prone to pollutants from anthropogenic activities such as agricultural and industrial activities in the upper catchments. The main aim of the study was to use free-living nematodes as pollution indicators in the Incomati River Estuary. The main objectives were to determine the relationship between nematodes assemblage and environmental variables, and to identify environmental factors that play a role in nematodes community structuring. Lastly, it was to identify free-living nematode genera that can be used as pollution indicators in the Incomati River Estuary. Four sites were selected following the salinity gradient of the Incomati River Estuary. Site E1 with a salinity range of 0-3NST (Oligohaline Zone), E2 with a salinity 3-5NST (Euhaline Zone), E3 with a salinity 6-18NST (Mesohaline Zone), and E4 with 20-27 NST (Polyhaline Zone) were selected and monitored bi-monthly from June 2017 to April 2018. Two sediments samples were collected per site during neap tide using a handheld perplex corer which was 1m long with a 3.6 diameter and 10cm penetration height. Plastic bottles with a height of 13cm and a diameter of 7cm were used to store the sediment samples. One of the two sediment samples was used for free-living nematodes, and the other bottle was used for the analysis of environmental factors. All environmental factors were analysed at Labserve Laboratory, Mbombela Town, Mpumalanga Province. Sediment particle size and organic matter analyses were done following the procedure set by Parker (1983) and Buchanan (1971) respectively. Metal analysis was done following the procedure used by Gyedu-Ababio et al.1999. Nutrients were done using different methods. For nitrates (NO3) analysis, a copper cadmium method by Bate and Heelas, 1975 was used, while a method designed by Strickland and Parson, 1972 was used to analyse orthophosphate. A mixed acid digestion procedure of Oles and Dean 1965 was followed for total phosphate. A method by Lorenzen and Jeffrey, 1980 was used for the analysis of chlorophyll-a. Heterotrophic bacteria analysis were done following a procedure by (Atlas, 1997). Nematodes were extracted using a method by Furstenberg et al.1978, with sucrose as a separating agent. Nematodes were counted following a procedure by Giere, 1993. Nematodes feeding types were investigated using Wieser, 1953 procedure. Different statistical packages including PRIMER version 6 were used to analyse the data. A Bray-Curtis Cluster analysis indicated a similarity between sites E1 (Oligohaline Zone) and E2 (Euhaline Zone), and between site E3 (Mesohaline Zone) and E4 (Polyhaline Zone) which was attributed to similar sediment particle sizes distribution within the sites. There was no significant difference (p>0.05) of sediments particle size between the sites. The highest concentration of metals was found at site E2 which was situated in the Euhaline Zone, whilst the second highest concentration was found at site E1 which was situated in the Oligohaline Zone. A PERMANOVA analysis indicated that there was a significant difference (p<0.05) of Metal concentration between sites sampled. The PCA analyses indicated that there was a positive correlation between Metals and Sediment Particle Size such as Granules. It was observed that sediment particle size and organic matter influenced the distribution of metals in the Estuary. The highest concentration of chlorophyll-a and nitrates (NO3) were found at site E3 which was situated in the Mesohaline Zone, and the second highest was found at site E4 which was situated in the Polyhaline Zone. There was a positive correlation between Heterotrophic bacteria and environmental factors such as zinc, fine sand, very fine sand and mud. This indicated that certain metals and sediment particles size played a role in structuring food source for meiofauna, especially nematodes. The number of free-living nematodes were found to decrease towards site E1. This indicated that salinity influenced the diversity and density of free-living nematodes in the estuary. Site E2 had the lowest diversity and richness followed by site E1. The lower diversity, richness and Maturity Index at site E2 and E1 indicated that these sites were under stress. A Bray-Curtis Cluster analysis indicated that there was a spatio-temporal variation of diversity and density of free-living nematodes in the estuary. All four nematodes feeding types were found in the Estuary and feeding type 1B was the dominant feeding type at the sites, followed by feeding type 2A. The highest number of feeding type 1B (non-selective deposit feeders) was identified at site E2. The life strategy characterisation (colonizer- persisters) indicated that site E2 was dominated by colonizer and intermediate genera (c-p 2 and 3), which indicated that the site was under stress. The study found that genera such as Terschellingia and Theristus were pollution indicators because they were found in higher abundance at a site that was mostly polluted by metals, organic matter, and total phosphate. Further studies in other River Estuaries in South Africa and SADC should be undertaken to add to the findings of the current study. / Environmental Studies / Ph. D. (Environmental Sciences)

No description available.

Historical environmental changes in two shallow, unstratified, estuaries in Buzzards Bay, Massachusetts are compared, using three diatom paleo-production indicators: sedimentary biogenic silica (BSi), BSi flux and ratio of Centric to Penate diatoms. Both estuaries were exposed to pollution. New Bedford Harbor (NBH) has a history of intensive nutrient loading and industrial pollution, while the control site, Apponagansett Bay, has lower levels of nutrient loading. Consideration of local precipitation history and diatom parameters suggests that salinity-driven changes in diatom production are negligible. Over the past &sim;350 yrs, BSi concentrations and fluxes are higher in NBH. Thus, overall diatom production is sensitive to nutrient enrichment and less responsive to industrial pollutants. The relationship between the C/P ratio and environmental conditions is not as clear, possibly due to its dependence on eelgrass abundance. The uniqueness of this study lies in its use of the parameters combined, as well as its geographic setting.

No description available.