1,720,974 research outputs found
Primary Production and Nutrient Dynamics of Urban Ponds
No full textIn urban areas, stormwater management ponds (SWPs) are built to mitigate polluted runoff. Although these ponds are increasing in numbers, their ecology is not well understood. Physical and chemical characteristics of 17 SWPs in the City of Ottawa were measured to determine the drivers of phytoplankton biomass (Chl. a) and primary production (PP). While total phosphorus was the best predictor of algal biomass in the ponds (as in lakes), the imperviousness of the catchment could also predict Chl. a. Planktonic PP in two ponds measured seasonally was more closely related to water residence time than to nutrient concentrations with rates approaching at times the theoretical maximum for aquatic systems. In one pond, whole ecosystem metabolism, estimated using diel changes in dissolved oxygen and δ18O-O2, suggested that these hypereutrophic systems were net sinks for carbon in the summer but likely sources to the atmosphere at other times of the year
Phytoplankton Communities in Temperate Rivers
No full textThe structure of phytoplankton communities was examined seasonally across five rivers with a focus on small cells and their relative importance. Picophytoplankton (0.2-2 μm), previously considered insignificant in rivers, reached densities as high as those observed in lakes and oceans (~ 10e4-10e5 cells/mL). Their relative importance was not a function of trophic state with the highest contribution to algal biomass found in the most eutrophic river. Body size distributions were analyzed from both chlorophyll-a size fractions and taxonomic enumerations; no significant effect of river or season was detected, suggesting that phytoplankton size distribution is not a useful metric of change in rivers. Unlike lake ecosystems, the rivers were uniformly dominated by small cells (< 20 μm). Taxonomic analyses of the seasonal succession did not reveal a common periodicity of particular divisions (e.g. diatoms). However, strong dominance was more typical of eutrophic rivers even though taxa richness was similar
Phytoplankton Communities in Temperate Rivers
No full textThe structure of phytoplankton communities was examined seasonally across five rivers with a focus on small cells and their relative importance. Picophytoplankton (0.2-2 μm), previously considered insignificant in rivers, reached densities as high as those observed in lakes and oceans (~ 10e4-10e5 cells/mL). Their relative importance was not a function of trophic state with the highest contribution to algal biomass found in the most eutrophic river. Body size distributions were analyzed from both chlorophyll-a size fractions and taxonomic enumerations; no significant effect of river or season was detected, suggesting that phytoplankton size distribution is not a useful metric of change in rivers. Unlike lake ecosystems, the rivers were uniformly dominated by small cells (< 20 μm). Taxonomic analyses of the seasonal succession did not reveal a common periodicity of particular divisions (e.g. diatoms). However, strong dominance was more typical of eutrophic rivers even though taxa richness was similar
The Cyanotoxin Anatoxin-a: Factors Leading to its Production and Fate in Freshwaters
No full textAnatoxin-a (ANTX) is a neurotoxin produced by several freshwater cyanobacteria and has
been implicated in the death of livestock and domestic animals from consumption of tainted
surface waters. ANTX is unstable under normal conditions and is somewhat problematic to
extract and study. Accelerated solvent extraction (ASE) combined with liquid
chromatography-mass spectrometry (LC/MS) was used to develop an efficient extraction and
analytical method for both ANTX and the more commonly encountered hepatotoxic
microcystins produced by cyanobacteria. The effects of nitrogen supply on the cellular
production and release of ANTX was investigated in Aphanizomenon issatschenkoi
(Ussaczew) Proschkina-Lavrenko (Nostocales). In contrast to the predictions of the carbonnutrient
balance hypothesis, the maximum production was observed under moderate N stress.
In addition, steady state fugacity-based models were employed to investigate ANTX’s
distribution and fate in freshwater ecosytems. ANTX was not found to be very persistent in
aquatic ecosystems and did not appear to bioaccumulate in fish, at least not from the
dissolved phase
Primary Production and Nutrient Dynamics of Urban Ponds
No full textIn urban areas, stormwater management ponds (SWPs) are built to mitigate polluted runoff. Although these ponds are increasing in numbers, their ecology is not well understood. Physical and chemical characteristics of 17 SWPs in the City of Ottawa were measured to determine the drivers of phytoplankton biomass (Chl. a) and primary production (PP). While total phosphorus was the best predictor of algal biomass in the ponds (as in lakes), the imperviousness of the catchment could also predict Chl. a. Planktonic PP in two ponds measured seasonally was more closely related to water residence time than to nutrient concentrations with rates approaching at times the theoretical maximum for aquatic systems. In one pond, whole ecosystem metabolism, estimated using diel changes in dissolved oxygen and δ18O-O2, suggested that these hypereutrophic systems were net sinks for carbon in the summer but likely sources to the atmosphere at other times of the year
Picocyanobacteria in oligotrophic to mesotrophic lakes: Variables affecting their abundance and analysis by flow cytometry.
No full textPicocyanobacteria (PC) are microscopic blue green algae responsible for a tenth of the total primary production of marine and freshwater systems. In this research, the ecology of temperate lake PC populations and their flow cytometry signatures were studied. In the first chapter, I examined the relative importance of growth versus losses of picocyanobacteria (PC) and the influence of physical and chemical variables on their in situ abundance in 48 temperate freshwater lakes. Growth and loss rates of PC were estimated from in situ incubations using a selective metabolic inhibitor technique and abundance of PC was determined by epifluorescence microscopy. In the second chapter, I examined the use of flow cytometry to identify PC and determine their abundance in lake water samples. The background noise appears higher in lake samples than marine ones. The source of this noise needs to be identified and corrected in future studies. However, flow cytometry is a promising tool for examining pigment distributions and for rapid assessments of the phytoplanktonic community. Epifluorescence remains the most reliable technique to determine PC abundance and pigment composition in freshwater lakes. (Abstract shortened by UMI.
Plankton development and trophic interactions in rivers.
No full textThe factors regulating the development and trophic interactions of planktonic communities were determined in 31 medium to large size temperate rivers. In addition, the Rideau River, Ontario, was studied in detail over three field seasons. Variables measured included: phytoplankton biomass as measured by chlorophyll concentration; zooplankton biomass (rotifers and crustaceans); heterotrophic bacterial abundance; heterotrophic flagellate abundance; nutrient concentrations (phosphorus and nitrogen); dissolved organic carbon concentration; river discharge; water residence time; depth; temperature; and light attenuation. Phytoplankton was abundant in eutrophic rivers (15 g L\sp{-1} of chlorophyll a) and was most strongly related to nutrient concentrations, primarily total phosphorus, which explained up to 76% of the variation in chlorophyll a. Phytoplankton biomass in the rivers was not related to the hydrological parameters of water residence time or discharge, possibly due to the short generation time of phytoplankton (hours to days). Light did not appear to limit phytoplankton biomass due to shallow depths and extensive vertical mixing. In the Rideau River phytoplankton biomass exhibited longitudinal heterogeneity, but in general increased in a downstream direction, concomitant with increases in nutrient concentrations. Phytoplankton biomass did not appear to be affected by zooplankton grazing in the rivers. However, phytoplankton biomass may have been negatively impacted by benthic filter feeders, in particular the invasive zebra mussel (Dreissena polymorpha), in the downstream reaches of the Rideau River. Zooplankton biomass in the rivers was low (usually 20 g L\sp{-1} dry mass) and small taxa dominated the zooplankton communities (e.g. rotifers, bosminids). Large zooplankton taxa, such as Daphnia sp., were much less abundant. Due to longer generation times (days to weeks), zooplankton biomass was primarily related to water residence time which explained 33% of the variation. Zooplankton appeared susceptible to advective loss in the rivers. A positive resource effect of either nutrients or phytoplankton on zooplankton biomass, typically observed in lakes, was weaker in the rivers. In comparison to lakes, zooplankton appeared less tightly coupled to phytoplankton. As with phytoplankton, zooplankton biomass in the Rideau River increased with downstream travel and appeared to be negatively affected by benthic filter feeders. Heterotrophic bacteria were abundant in the rivers (4.5 10\sp6 cells ml\sp{-1}) and, as in lakes, bacteria were most strongly related to nutrient concentrations (total phosphorus) and phytoplankton biomass (chlorophyll a). In contrast to lakes, no relationship between bacterial abundance and dissolved organic carbon was observed, possibly due to the more allochthonous, refractory nature of river dissolved organic carbon. Heterotrophic flagellates were also abundant in the rivers (4.0\times10\sp{3} cells ml\sp{-1}) and were most strongly related to bacterial abundance and nutrient concentrations (total phosphorus). Neither bacterial nor flagellate abundance was related to water residence time. A negative relationship between zooplankton biomass and bacterial or flagellate abundance was not observed, possibly because of the low biomass (hence low grazing pressure) of zooplankton in the rivers. Due to the scarcity of zooplankton in rivers, there may be little transfer of energy from the planktonic microbial food web to planktonic metazoans
Plankton development and trophic interactions in rivers.
No full textThe factors regulating the development and trophic interactions of planktonic communities were determined in 31 medium to large size temperate rivers. In addition, the Rideau River, Ontario, was studied in detail over three field seasons. Variables measured included: phytoplankton biomass as measured by chlorophyll concentration; zooplankton biomass (rotifers and crustaceans); heterotrophic bacterial abundance; heterotrophic flagellate abundance; nutrient concentrations (phosphorus and nitrogen); dissolved organic carbon concentration; river discharge; water residence time; depth; temperature; and light attenuation. Phytoplankton was abundant in eutrophic rivers (15 g L\sp{-1} of chlorophyll a) and was most strongly related to nutrient concentrations, primarily total phosphorus, which explained up to 76% of the variation in chlorophyll a. Phytoplankton biomass in the rivers was not related to the hydrological parameters of water residence time or discharge, possibly due to the short generation time of phytoplankton (hours to days). Light did not appear to limit phytoplankton biomass due to shallow depths and extensive vertical mixing. In the Rideau River phytoplankton biomass exhibited longitudinal heterogeneity, but in general increased in a downstream direction, concomitant with increases in nutrient concentrations. Phytoplankton biomass did not appear to be affected by zooplankton grazing in the rivers. However, phytoplankton biomass may have been negatively impacted by benthic filter feeders, in particular the invasive zebra mussel (Dreissena polymorpha), in the downstream reaches of the Rideau River. Zooplankton biomass in the rivers was low (usually 20 g L\sp{-1} dry mass) and small taxa dominated the zooplankton communities (e.g. rotifers, bosminids). Large zooplankton taxa, such as Daphnia sp., were much less abundant. Due to longer generation times (days to weeks), zooplankton biomass was primarily related to water residence time which explained 33% of the variation. Zooplankton appeared susceptible to advective loss in the rivers. A positive resource effect of either nutrients or phytoplankton on zooplankton biomass, typically observed in lakes, was weaker in the rivers. In comparison to lakes, zooplankton appeared less tightly coupled to phytoplankton. As with phytoplankton, zooplankton biomass in the Rideau River increased with downstream travel and appeared to be negatively affected by benthic filter feeders. Heterotrophic bacteria were abundant in the rivers (4.5 10\sp6 cells ml\sp{-1}) and, as in lakes, bacteria were most strongly related to nutrient concentrations (total phosphorus) and phytoplankton biomass (chlorophyll a). In contrast to lakes, no relationship between bacterial abundance and dissolved organic carbon was observed, possibly due to the more allochthonous, refractory nature of river dissolved organic carbon. Heterotrophic flagellates were also abundant in the rivers (4.0\times10\sp{3} cells ml\sp{-1}) and were most strongly related to bacterial abundance and nutrient concentrations (total phosphorus). Neither bacterial nor flagellate abundance was related to water residence time. A negative relationship between zooplankton biomass and bacterial or flagellate abundance was not observed, possibly because of the low biomass (hence low grazing pressure) of zooplankton in the rivers. Due to the scarcity of zooplankton in rivers, there may be little transfer of energy from the planktonic microbial food web to planktonic metazoans
The Cyanotoxin Anatoxin-a: Factors Leading to its Production and Fate in Freshwaters
No full textAnatoxin-a (ANTX) is a neurotoxin produced by several freshwater cyanobacteria and has
been implicated in the death of livestock and domestic animals from consumption of tainted
surface waters. ANTX is unstable under normal conditions and is somewhat problematic to
extract and study. Accelerated solvent extraction (ASE) combined with liquid
chromatography-mass spectrometry (LC/MS) was used to develop an efficient extraction and
analytical method for both ANTX and the more commonly encountered hepatotoxic
microcystins produced by cyanobacteria. The effects of nitrogen supply on the cellular
production and release of ANTX was investigated in Aphanizomenon issatschenkoi
(Ussaczew) Proschkina-Lavrenko (Nostocales). In contrast to the predictions of the carbonnutrient
balance hypothesis, the maximum production was observed under moderate N stress.
In addition, steady state fugacity-based models were employed to investigate ANTX’s
distribution and fate in freshwater ecosytems. ANTX was not found to be very persistent in
aquatic ecosystems and did not appear to bioaccumulate in fish, at least not from the
dissolved phase
Stormwater Retention Ponds: Hydrogen Sulfide Production, Water Quality and Sulfate-Reducing Bacterial Kinetics
No full textStormwater retention basins are an integral component of municipal stormwater management strategies in North America. The province of Ontario’s Ministry of the Environment and Climate Change obligates land developers to implement stormwater management in their land use and development plans to mitigate the effects of urbanization (Bradford and Gharabaghi, 2004). When stormwater retention ponds are improperly designed or maintained, these basins can fail at improving effluent water quality and may exasperate water quality issues. \ud
Intense H2S production events in stormwater infrastructure is a serious problem which is seldom encountered and documented in stormwater retention ponds. This study monitored two stormwater retention ponds situated in the Riverside South community, Ottawa, Ontario, Canada for a period of 15 consecutive months to thoroughly characterize intense hydrogen sulfide (H2S) production in a stormwater retention pond under ice covered conditions during winter operation and during periods of drought under non-ice covered conditions during the summer.\ud
Field experiments showed a strong relationship (p < 0.006, R > 0.58, n = 20+) between hypoxic conditions (dissolved oxygen (DO) concentration < 2 mg/L) and the intense production of H2S gas. Ice-capping of the stormwater ponds during winter severely hindered reaeration of the pond and led to significant production of total sulfides in the Riverside South Pond #2 (RSP2), which subsequently resulted in the accumulation of total sulfides in the water column (20.7 mg/L) during winter in this pond. There was a perceived lag phase between the drop in DO and the increase in total sulfides near the surface, which was potentially indicative of slow movement of total sulfides from the benthic sediment into the water column. These high-sulfide conditions persisted in RSP2 from early January 2015 until the spring thaw, in mid-April, 2015. Riverside South Pond #1 (RSP1), the reference pond studied in this work, showed significantly less production of total sulfides across a significantly shorter period of time. Analysis of the microbial communities showed that there was little change in the dominant bacterial populations present in the benthic sediment of the pond demonstrating significant total sulfide production (RSP2) and the pond that did not demonstrate significant total sulfide production (RSP1). Additionally, it was found that locations with the most accumulated sediment had the highest propensity for the production of H2S gas. Furthermore, there was no perceivable community shift in the two ponds throughout the seasons, indicating that the sulfate-reducing bacteria (SRB) in stormwater benthic sediment are ubiquitous, exist in an acclimatized microbial population and are robust. Study of the microbial abundances revealed that SRB represented approximately 5.01 ± 0.79 % of the microbes present in the benthic sediment of RSP2. Likewise, in the stormwater pond which did not experience intense H2S gas production, RSP1, 6.22 ± 2.11 % of microbes were of the SRB type, demonstrating that H2S gas production does not correspond to higher concentrations of SRB or the proliferation of dominant species, but rather is a symptom of increased bacterial activity due to favourable environmental conditions.\ud
In addition, this work also covers the kinetics of sediment oxygen demand (SOD), ammonification and sulfate-reduction, and attempts to understand the processes leading to H2S gas production events.\ud
In doing so, it was observed that kinetics obtained full-scale field studies were greater than in laboratory kinetic experiments. Laboratory experiments at 4°C identified total SOD, ammonification and sulfate-reduction kinetics to be 0.023 g/m2/day, 0.027 g N/m2/day and 0.004 g S/m2/day, respectively. Meanwhile, kinetics calculated from the field study of stormwater retention ponds for total SOD, ammonification and sulfate-reduction were of 0.491 g/m2/day, 0.120 g N/m2/day and 0.147 g S/m2/day, respectively. It is expected that this difference is due to the depth of active sediment influencing the total rates of production/consumption, making area-normalized daily rates of production/consumption (g/m2/day) unsuitable for the comparison of field and laboratory studies, without some scaling factor. This study also measured supplementary kinetic parameters such as the Arrhenius coefficients and the half-saturation coefficient, to add to existing knowledge of sulfate-reduction
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