The in-stream water quality model, QUAL2Kw, can provide guidance in watershed management decisions by linking changes in nutrient loads to responses in water quality. This model is particularly useful for determining wasteload allocations, aiding in total maximum daily load analyses, and developing numeric nutrient criteria. Unfortunately, states struggle to balance the data collection and modeling requirements to accomplish many of these water quality management tasks due to limited resources. This commonly results in routine data collection and monitoring efforts that do not satisfy the data requirements for modeling. To address this disconnect, this study presents a data collection and parameter calibration methodology suited to meet general QUAL2Kw modeling requirements. Then, with the goal of identifying a range of numeric nitrogen and phosphorus criteria, this general data collection and modeling strategy was applied to sites throughout Utah. To help automate and test scenarios targeted at tracking effects of loading and response combinations, a nutrient criteria tool was also developed to interface with these QUAL2Kw models. By implementing the tool on these models, input concentrations of ammonium (NH4+) ranging from 10 to 101 µg/L and inorganic phosphorus (PO4-) ranging from 1 to 14 µg/L were found to exceed thresholds of bottom algae, gross primary productivity, and ecosystem respiration. Conversely, NH4+ concentrations above 3,500 µg/L and PO4- above 490 µg/L exceeded dissolved oxygen thresholds of 5-6 mg/L in some applications. Some limitations of using mechanistic models in this manner were identified, including model capabilities (e.g., steady-state versus dynamic), inclusion of appropriate processes, uncertainty in calibrated parameters, and site-specific conditions. Although many problems will require more complex modeling efforts with significantly larger data collection efforts, this approach provides an initial framework that aids in the judicial use of resources to aid in watershed management decisions.

The relationships between C:N:P (carbon, nitrogen, and phosphorus) stoichiometry of Cladophora glomerata and land use characteristics in selected nearshore areas of the lower Laurentian Great Lakes were determined during two years of field sampling of coastal areas. In the past, bi-national reduction of point sources of P-loading resulted in reduced C. glomerata biomass; however, currently C. glomerata is resurging and it has been suggested that non-point source P loading, which may have increased with increasing populations and coastal land use changes, may be the cause. Study of the Halton shoreline, Lake Ontario, in 2006 demonstrated that C. glomerata nutrient stoichiometry has a strong seasonal relationship as internal P concentrations at 2 and 5 m depths decline to as low as 0.5 μg/mg dw during the rapid early summer growth period, well below the literature value of 1.6 μg/mg dw indicative of P limitation. Samples at 10 m maintained a constant surplus in P throughout the summer as light was the greater controlling factor at this depth. Along with ambient dissolved P, C. glomerata internal P increased sharply during the September and October surveys to approximately 3.5 μg P/mg dw at 2 m stations. Throughout the 2006 growing season both water chemistry and C. glomerata nutrient stoichiometry did not identify any direct point source influencing algal growth as indicated by tissue stoichiometry. Land use comparisons between the urbanized Halton region and the non urban sites of Presqu’ile Provincial Park and Peacock Point (Lakes Ontario and Erie, respectively) indicated significantly higher enrichment in both nitrogen and phosphorus at the 10 m urban stations as internal P concentrations were elevated and both N and P nutritional status indicators (C/P, C/N, and N/P) were much lower compared with non-urban sites. Areas with relatively more human impact (Port Credit and Halton on Lake Ontario) had higher internal P concentrations in C. glomerata. Through empirical evidence, nutrient status ratios predict the onset of P limitation for Cladophora glomerata within the Great Lakes to have values for C:P > 505 and N:P > 41, whereas zero positive growth was estimated to begin when C:P > 1246 and N:P > 75. Natural stable isotope abundances of 13C were indicative of benthic algal production as δ13C values from C. glomerata tissue samples during the early summer rapid growth period varied with depth to the 5 m depth contour. Though, overall 13C algal signals were a function of offshore changes in DIC-δ13C patterns throughout the year they were consistently lower in Cladophora tissue at shallower depths suggesting high photosynthetic demand for CO2 reduced isotopic photosynthetic fractionation. This trend was evident along most shorelines and from year to year, verifying the use of 13C stable isotope to define periods of potentially carbon-limited production. 13C and 15N did not identify any significant difference between urban and non urban shorelines. Similarly, stable isotopes were inconclusive in measuring local point source impacts. Similarly, point sources were also not apparent from measuring water chemistry and C. glomerata tissue parameters. The use of 15N isotopes in tracing C. glomerata filament origins may be of merit as persistent depth relationships were observed at all sites in Lake Erie and Ontario.

Ecological stoichiometry is the study of the balance of chemical substances in ecosystems. In freshwaters, research has focused on how the ratios of carbon, nitrogen and phosphorus in organisms and their environment affect ecosystem processes. Because autotrophs have variable stoichiometry, particulate C:N:P ratios are used to assess nutrient availability in lakes. Zooplankton have relatively fixed stoichiometry and so differences between their body stoichiometry and the stoichiometry of their food can constrain their growth. Ecological stoichiometry predicts that zooplankton with low C:P body ratios (e.g., Daphnia) will be limited by the P content of their food in lakes where seston C:P is high. The stoichiometric theory of consumer-driven nutrient recycling (CNR) predicts that the stoichiometry of a consumer will influence the stoichiometry of the nutrients they regenerate through such processes as egestion and excretion. In lakes, zooplankton with a low body N:P are expected to regenerate nutrients in a high N:P ratio, potentially shifting nutrient limitation of the food web from N to P limitation. I used data from 99 Canadian lakes to test the following: a. Are particulate C:P and N:P ratios consistent with other P deficiency indicators? b. Do seston C:P and N:P ratios affect zooplankton community composition? c. Does zooplankton community composition affect plankton P limitation as predicted by CNR? Particulate C:P and N:P ratios generally agreed with other P deficiency indicators, except dissolved phosphate turnover times (TTPO4). C:P and N:P suggested P sufficiency more often than TTPO4, possibly because these two indicators respond to P deficiency over different time scales. Most zooplankton biomass parameters were negatively related to seston C:P ratios consistent with improved food quality at lower seston C:P. There was, however, no evidence that Daphnia were more strongly affected than any other zooplankton. Turnover times of particulate P in the whole plankton assemblage were not related to zooplankton community structure parameters. However, particulate P turnover in the >200 µm size fraction increased with increasing zooplankton biomass. There was no evidence for a particular effect of Daphnia on particulate P turnover. Phosphorus deficiency indicators showed a trend of relaxing P deficiency as zooplankton biomass and the proportion of Daphnia increased. This contradicts the predictions of CNR which suggest that Daphnia should cause greater P deficiency in lakes.

The relationships between C:N:P (carbon, nitrogen, and phosphorus) stoichiometry of Cladophora glomerata and land use characteristics in selected nearshore areas of the lower Laurentian Great Lakes were determined during two years of field sampling of coastal areas. In the past, bi-national reduction of point sources of P-loading resulted in reduced C. glomerata biomass; however, currently C. glomerata is resurging and it has been suggested that non-point source P loading, which may have increased with increasing populations and coastal land use changes, may be the cause. Study of the Halton shoreline, Lake Ontario, in 2006 demonstrated that C. glomerata nutrient stoichiometry has a strong seasonal relationship as internal P concentrations at 2 and 5 m depths decline to as low as 0.5 μg/mg dw during the rapid early summer growth period, well below the literature value of 1.6 μg/mg dw indicative of P limitation. Samples at 10 m maintained a constant surplus in P throughout the summer as light was the greater controlling factor at this depth. Along with ambient dissolved P, C. glomerata internal P increased sharply during the September and October surveys to approximately 3.5 μg P/mg dw at 2 m stations. Throughout the 2006 growing season both water chemistry and C. glomerata nutrient stoichiometry did not identify any direct point source influencing algal growth as indicated by tissue stoichiometry. Land use comparisons between the urbanized Halton region and the non urban sites of Presqu’ile Provincial Park and Peacock Point (Lakes Ontario and Erie, respectively) indicated significantly higher enrichment in both nitrogen and phosphorus at the 10 m urban stations as internal P concentrations were elevated and both N and P nutritional status indicators (C/P, C/N, and N/P) were much lower compared with non-urban sites. Areas with relatively more human impact (Port Credit and Halton on Lake Ontario) had higher internal P concentrations in C. glomerata. Through empirical evidence, nutrient status ratios predict the onset of P limitation for Cladophora glomerata within the Great Lakes to have values for C:P > 505 and N:P > 41, whereas zero positive growth was estimated to begin when C:P > 1246 and N:P > 75. Natural stable isotope abundances of 13C were indicative of benthic algal production as δ13C values from C. glomerata tissue samples during the early summer rapid growth period varied with depth to the 5 m depth contour. Though, overall 13C algal signals were a function of offshore changes in DIC-δ13C patterns throughout the year they were consistently lower in Cladophora tissue at shallower depths suggesting high photosynthetic demand for CO2 reduced isotopic photosynthetic fractionation. This trend was evident along most shorelines and from year to year, verifying the use of 13C stable isotope to define periods of potentially carbon-limited production. 13C and 15N did not identify any significant difference between urban and non urban shorelines. Similarly, stable isotopes were inconclusive in measuring local point source impacts. Similarly, point sources were also not apparent from measuring water chemistry and C. glomerata tissue parameters. The use of 15N isotopes in tracing C. glomerata filament origins may be of merit as persistent depth relationships were observed at all sites in Lake Erie and Ontario.

This study aims to understand the influence of external forcing (i.e. climate, human influences) changes on the inputs of terrigenous materials from the Kaoping River as well as the biogeochemical responses of carbon and nutrients to riverine fluxes in the Kaoping coastal zone. The Kaoping River exhibits contrasting patterns in water discharge and material fluxes between wet and dry seasons. In general, river discharge is about 12 times higher in the wet season than in the dry season. Riverine fluxes of terrigenous materials (DOC¡BPOC¡BDSi¡BDIN¡BDIP¡BTDN and TDP) are about 3 to 10 times higher in the wet season than in the dry season. Consequently, distribution patterns of carbon, nutrients and hydrochemical parameters are significant difference among four seasons in the Kaoping coastal zone. Distributions of DOM (dissolved organic matter), POM (particulate organic matter) and nutrients in the Kaoping coastal zone show that the highest concentration is generally found in the area close to the Kaoping estuary, and the concentration decreases with the distance away from the land. The riverine fluxes also affect the ratios of DOC/TOC and £GPOC/£GPN in the coastal zone. The characteristics of DIN and DIP distributions and their ratios imply that the primary productivity may be largely limited by nitrogen (DIN < 1£gM¡AN/P < 10) rather than phosphorus (DIP < 0.2£gM¡AN/P < 30) in the Kaoping coastal zone. The occurring probability of nitrogen limitation varies from season to season during the study period, roughly ranging from 4% to 42% (winter, summer > spring, autumn). The GP (gross production) ranges from 708-19819 mg C m-2 d-1 in spring, from 2451-16230 mg C m-2 d-1 in summer, and from 844-5549 mg C m-2 d-1 in winter. The DCR (dark community respiration) ranges from 970-6284 mg C m-2 d-1 in spring, from 861-12418 mg C m-2 d-1 in summer, and from 997-5781 mg C m-2 d-1 in winter. Both GP and DCR display the highest value in summer, indicating the significant influence of terrigenous fluxes on biological production and respiration during summer. Meanwhile, correlations are significantly positive between GP (DCR) and temperature and nutrients, but significantly negative between GP (DCR) and salinity, also indicating the impacts of terrigenous inputs on GP and DCR. In the Kaoping coastal zone, the BCD (bacterial carbon demand) is about 15% GP and 64% GP, respectively, in winter and summer, inplying that the contribution of GP to BCD is more important in winter than in summer. Judging from the ratio of GP/DCR in different seasons and sampling stations, we conclude that the study area near the Kaoping estuary is likely to be autotrophic throughout the study period, the other stations are also likely to be autotrophic during summer. Nevertheless, the offshore stations appear to be heterotrophic during the winter season.

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Estuarine phytoplankton growth is often controlled by nitrogen availability. In addition to overall nitrogen loads, nitrogen form (organic vs. inorganic) is an important factor affecting estuarine phytoplankton growth and community composition. Recent studies have shown that in addition to nitrogen availability, trophic cascades and relaxation of grazing pressure may also be important for phytoplankton bloom formation in estuaries. With a goal of better understanding how nitrogen availability and grazing pressure interact to control estuarine phytoplankton growth and community composition, we examined the individualistic as well as the combined effects of nitrogen (varying availability and form) and grazing pressure on estuarine phytoplankton growth and community composition in the Neuse River Estuary, North Carolina, USA. During each of three sampling events (June 2011, August 2011, March 2012) natural phytoplankton assemblages were manipulated with added nitrogen (as urea or nitrate) and reduced grazing pressure (by filtering out zooplankton grazers). Treatments were incubated for 48 hours in an experimental pond, and subsamples taken daily to assess phytoplankton growth responses to treatments through chlorophyll a, diagnostic photopigments and cell enumerations. The effects of nitrogen additions and reduced grazing pressure varied throughout the events. In June, only nitrogen addition stimulated phytoplankton community growth (chlorophyll a), while in August, only grazing reduction had a significant impact on community growth. Neither treatment had a significant effect on community growth in March, as the phytoplankton community faced phosphorus-limitation and decreased grazing pressure associated with cooler winter/spring temperatures. While both treatments did not continuously effect overall phytoplankton growth throughout all experiments, there were always effects seen in some diagnostic photopigments, indicating varying taxa-specific responses to treatments throughout the year, which can be explained by shifts in phytoplankton community composition and environmental factors. These results demonstrate the importance of both bottom-up (nutrient availability and form) and top-down (grazing) controls in a temperate, eutrophic estuary. Results also hint at the potential for other factors (i.e. light and phosphorus-limitation) to play a role in phytoplankton growth as well. Phytoplankton growth, biomass and community dynamics are relevant indicators of environmental change and this study highlights the need to consider the potential interactive effects of controlling factors for proper management of estuarine ecosystems.

Common Carp, (Cyprinus carpio), have long been associated with the degradation of wetlands worldwide. Through their feeding activities they resuspend sediments leading to reductions in the abundance and diversity of submerged macrophytes, and the alteration of water chemistry which can lead to the phytoplankton-dominated state. This study took in Delta Marsh, a freshwater coastal wetland of Lake Manitoba, in Manitoba, Canada. It was the second part of a four-year study in which baseline data were collected in 2001 from ten ponds (1-13 ha) with varying degrees of connectivity to the main marsh and carp-accessibility. I continued to monitor a subset of the control and altered ponds two and three years following their alteration (2003 and 2004); I included new ponds, including one large open bay (20.3 ha). The overall four-year study has shown that the presence of carp is at least partially responsible for the turbid, phytoplankton-dominated state that exists in Delta Marsh, and that carp abundance is an important factor. Ponds previously isolated then exposed to carp activity, particularly in the spring when they were gathered at high densities, shifted to the turbid, phytoplankton-dominated state with few macrophytes, and the removal of carp from ponds led to the clear-water state, though not necessarily an abundance of macrophytes. Due to the complexity of natural ecosystems, the effects of carp were not as predictable as smaller-scale studies would suggest. In my study, water quality, submerged vegetation biomass and algal growth varied both temporally and spatially in carp-accessible and carp-free ponds. Nutrient deficiency among periphyton assemblages was hypothesized to be alleviated by the presence of carp. Using nutrient diffusing substrata, I found that nutrient deficiencies varied from year to year among carp-free and carp-accessible ponds. In 2003 the hypothesis was supported, however, in 2004 two of the carp-free ponds exhibited no-nutrient limitations to periphyton assemblages while N and P co-limitation became prevalent in one carp-accessible pond. Parameters over which there was no control, such as the spatial and temporal distribution of carp, their density within a pond, water depth and unquantified top-down effects, including zooplankton grazing, may have contributed to the variability of the results.

Over the last few decades increasing attention has been paid to the effects of land use activities and land management on stream water quality. Recent research has largely focused on dominant land uses such as urban development and agricultural cropland. The relative effect of land use activities and management on stream chemistry in sub-tropical rangeland ecosystems, where much of the land use is converted to pasture and agriculture is largely unknown. This study examined stream water quality and land use in a sub-tropical watershed in Northeast Texas largely dominated by rangeland. The study site, White Oak Creek Watershed located in the Sulphur River Basin, has been identified as an impaired stream due to low dissolved oxygen concentrations and subsequently listed on the Texas Commission for Environmental Quality's 303d list (TCEQ). In an attempt to determine potential sources of the low dissolved oxygen concentrations, twenty different chemical constituents were analyzed at 18 different sample sites in the tributaries of White Oak Creek and also along the main stem from April 2010 to March 2011. Dissolved oxygen concentrations over the study period were consistently above the minimum standard required by TCEQ and showed no indication of impairment. Correlation analysis did not show any clear correlation between dissolved oxygen and any specific land use, or any chemical constituent. Some nutrients and suspended sediment concentrations were significantly different among the sub-catchments of White Oak Creek. Urban land uses were significantly and positively correlated to electrical conductivity, ammonium-N, magnesium, calcium, and dissolved organic carbon. Agricultural land use was significantly and positively correlated to orthophosphate-P, dissolved organic nitrogen, total suspended solids, and turbidity. Forests were inversely and significantly related to nitrate-N, orthophosphate-P, sulfate, dissolved organic carbon, total suspended solids, and turbidity. The study suggested that by maintaining a relatively high proportion of forested land in a watershed that water quality can be improved.

No description available.