Eutrophication risk assessment in Hamilton Harbour: System analysis and evaluation of nutrient loading scenarios

The ecological history of Lake Ontario according to phytoplankton

“…Harris and Piccinin (1980) reported that the extremely high summer N:P ratios in the harbor favored green algal dominance and a prevalence of cryptophytes and chrysophytes. Although municipal sewage treatment discharge greatly improved, excessive eutrophication from P, ammonia (NO 3 ), suspended solids, and other contaminant loading still continues in Hamilton Harbour Gudimov et al, 2010). Dermott et al (2007)) reported that eutrophication symptoms included offensive algal growths, poor water clarity and depleted oxygen.…”

Estimation of tributary total phosphorus loads to Hamilton Harbour, Ontario, Canada, using a series of regression equations

“…Most of the winter TP loads in 2011 were comprised of a spring freshet loading, whereas sporadic winter runoff events comprised much of the winter TP loads in 2012. Use of a daily or seasonal metric in a watershed such as Hamilton Harbour will make it possible to draw potential causal connections between changes in winter TP loads from the watersheds, the magnitude of the spring algal bloom, and the subsequent impact of the autochthonous material on the summer hypoxia patterns in the Harbour (Gudimov et al, 2010).…”

Towards the development of an ecosystem model for the Hamilton Harbour, Ontario, Canada

“…This prediction is on par with recent empirical evidence that the microbial community (bacteria, autotrophic picoplankton, heterotrophic nanoflagellates, and ciliates) of the Hamilton Harbour constitutes an important vector of autochthonous energy transfer to higher trophic levels (e.g., Fitzpatrick et al, 2007;Munawar et al, 2005). Furthermore, the microbially mediated mineralization is likely to be an important supplier of bioavailable nutrients in the Harbour mixed layer and can largely determine the compliance of the system with the targeted water quality goals as the subsidies of phosphate associated with rapid nutrient turnover rates significantly modulate the epilimnetic phytoplankton dynamics and can conceivably cast doubt on the projected efficacy of the on-going restoration efforts (Gudimov et al, 2010). An intense nutrient regeneration can also explain the relatively small fraction of dissolved inorganic phosphorus relative to the contemporaneous total phosphorus or epilimnetic phytoplankton levels .…”

“…Increases in macrophyte growth and diversity will create more spawning and nursery habitat for certain native species, which in turn may be another regulatory factor (along with the reduction of the exogenous nutrient loading) to influence the duration of the transient phase and the future resilience of the system. The bottom-up approach historically followed in the Harbour was sufficient to bring the system to its present state, but any further improvements should be viewed in the context of a combined bottom-up and top-down control (Gudimov et al, 2010Ramin et al, 2011).…”

“…By the 1940s, local beaches were closed to swimming and soon thereafter the Harbour water quality deteriorated to its lowest level, resulting in limited public access to the shoreline. The water quality problems were primarily manifested as excessive algal blooms, low water transparency, predominance of toxic cyanobacteria, and low hypolimnetic oxygen concentrations during the late summer (Gudimov et al, 2010Hiriart-Baer et al, 2009;Leslie and Timmins, 1992;Ramin et al, 2011). Further, the elimination of the vegetated littoral zone and the disappearance of essential wetlands and fish nursery habitats, due to infilling for industrial activities as well as for railway or highway construction along the south and east shores of the Harbour, posed major threats to the integrity of the native fish community Holmes and Whillans, 1984;Minns et al, 1994).…”