Evaluation of management scenarios for controlling eutrophication in a shallow tropical urban lake

Urban lakes are typically smaller, shallower, and more exposed to human activities than natural lakes. Although the effects of harmful algal blooms (HABs) associated with eutrophication in urban lakes has become a growing concern for water resources management and environmental protection, studies focussing on this topic in relation to urban lakes are rare and knowledge of the ecological dynamics and effective management strategies for controlling eutrophication in urban lakes is lacking. This study applied an integrated three-dimensional hydrodynamics-ecological model for a small shallow tropical urban lake in Singapore and evaluated various management scenarios to control eutrophication in the lake. It is found that in-lake treatment techniques including artificial destratification, sediment manipulation and algaecide addition are either ineffective or possess environmental concerns; while watershed management strategies including hydraulic flushing and inflow nutrients reduction are more effective and have posed less environmental concerns. In this study, inflow phosphorus reduction was found to be the best strategy after evaluating the advantages and drawbacks of the management strategies studied. Runoff from the watershed exerts significant influence on urban lakes and thus an integrated water resources management at the watershed level is critical for the control of eutrophication

Nutrients, palaeolimnology and cyanobacterial blooms in Lake Wallace, Western Victoria

The basic limnology, nutrient and hydraulic budgets and recent history (using fossil remains in the sediments) of Lake Wallace have been studies to determine factors that predispose the lake to the development of potentially toxic algal blooms.

The use of artificial biofilms to strip nutrients from an industrial smelters waste water under conditions of low temperature and high pH

The Victorian Environment Protection Authority (EPA) has identified Alcoa’s Point Henry aluminium smelter as being a major source of recognized pollutant input due to its disposal of effluent into Corio Bay. Historically, the water quality parameters that have most often exceeded Point Henry’s EPA limits have been pH and suspended solids from the smelter’s discharge points. These waste water discharges also experience high nitrogen and phosphorus concentrations which result in algal blooms that occur at the onset of warm weather. The main hypothesis of this study was that “prevention of algal blooming with the onset of warm weather by removal of nutrients during the cooler months, and continued removal thereafter, is better than curing the problems chemically”. Biofilms have been used to remove nutrients from waste waters, but not under the conditions experienced at Point Henry. The aim of this study, therefore, was to determine if significant biofilm growth would be observed on floating structures suspended in the Point Henry waste water stream during the cooler, winter months of the year. Statistically significant biofilm growth occurred on all suspended structures in all discharge ponds during the winter and early spring of 2000. The use of suspended structures, such as AquaMatTM, as an artificial substrate to attract and support periphyton and bacterial communities (biofilms), which are then able to out-compete phytoplankton communities for available nutrients, is therefore a viable option for the Point Henry smelter. However, further research on the competitive performance of biofilms in the Point Henry ponds during the summer months is required before adequate biofilm management strategies can be developed.

Nutrient contribution to hyper-eutrophic wetlands in Perth, Western Australia

This thesis investigates nutrient contribution to six hyper-eutrophic lakes located within close proximity of each other on the Swan Coastal Plain and 20 kilometres south of the Perth Central Business District, Western Australia. The lakes are located within a mixed land use setting and are under the management of a number of state and local government departments and organisations. These are a number of other lakes on the Swan Coastal Plain for which the majority are less than 3 metres in depth and considered as an expression of the groundwater as their base is below the regional groundwater table throughout most of the year. The limited amount of water quality data available for these six lakes and the surface water and groundwater flowing into them has restricted a thorough understanding of the processes influencing the water quality of the lakes. Various private and public companies and organisations have undertaken studies on some of the individual wetlands and there is a wide difference in scientific opinion as to the major source of the nutrients to those wetlands. These previous studies failed to consider regional surface water and groundwater effects on the nutrient fluxes and they predominantly only investigated single wetland systems. This study attempts for the first time to investigate the regional contribution of nutrients to this system of wetlands existing on the Swan Coastal plain. As such, it also includes new research on the nutrient contribution to some of the remaining wetlands. The research findings indicate that the lake sediments represent a considerable store of nutrients (nitrogen and phosphorus). These sediments in turn control the nutrient status of the lake's water column. Surface water is found to contribute on an event-basis load of nutrients to the lakes whilst the groundwater surprisingly appears to contribute a comparatively low input of nutrients but governs the water depth. Analysis of the regional groundwater shows efficient denitrifying abilities as a result of denitrifying bacteria and the transport is localised. Management recommendations for the remediation of the social and environmental value of the lakes include treatment of the lake’s sediments via chemical bonding or atmospheric oxidation; utilising the regional groundwater’s denitrifying abilities to ‘treat’ the surface water via infiltration basins; and investigating the merits of managed or artificial aquifer recharge (MAR).

An integrated observation network for the Gippsland Lakes, Victoria, Australia : balancing the needs of science and management

The Gippsland Lakes region in eastern Victoria is a partially flushed coastal lake system within a diverse catchment of rural and urban communities. Pressure from lakeside developments, re-occurring blue-green algal blooms, declining fisheries, sedimentation and infilling of the ocean entrance, has borne several decades of focussed studies and routine monitoring programs, along with a variety of engineering and management solutions. A recent review recommended that these disparate studies should be enhanced to formulate a coordinated monitoring network that could improve both spatial and temporal coverage, develop a capacity to trigger responsive investigations and was able to serve the needs of system management. Through a series of partnerships an integrated network was developed that comprises event and baseline monitoring of catchment loads, local meteorological forcing and an array of water quality sampling sites within the lakes system. A majority of these sites are incorporated with real-time telemetry that provides up to the minute information to stakeholders via a web-based information management system and vital operational status to technical system management.

Comparative effects of the blue green algae Nodularia spumigena and a lysed extract on detoxification and antioxidant enzymes in the green lipped mussel (Perna viridis)

Nodularia spumigena periodically proliferates to cause toxic algal blooms with some aquatic animals enduring and consuming high densities of the blue green algae or toxic lysis. N. spumigena contains toxic compounds such as nodularin and lipopolysaccharides. This current work investigates physiological effects of exposure from bloom conditions of N. spumigena cells and a post-bloom lysis. Biochemical and antioxidative biomarkers were comparatively studied over an acute 3-day exposure. In general, a post-bloom N. spumigena lysis caused opposite physiological responses to bloom densities of N. spumigena. Specifically, increases in glutathione (GSH) and glutathione peroxidase (GPx) and decreases in glutathione S-transferase (GST) were observed from the N. spumigena lysis. In contrast, N. spumigena cell densities decreased GSH and increased GST and lipid peroxidation (LPO) in mussels. Findings also suggest that at different stages of a toxic bloom, exposure may result in toxic stress to specific organs in the mussel.

Nutrient and phytoplankton status of Lakes Purrumbete and Bullen Merri, western Victoria

The thesis investigates two adjacent volcanic maar lakes, with differences in chemical and biological properties. Lake Bullen Merri a brackish, phosphorous-limited lake that suffers from nuisance algal blooms and Lake Purrumbete a fresh, nitrogen-limited lake with diverse phytoplankton assemblage. Nutrient fluxes for both lakes are dominated by internal cycling.

Innovative reuse options for water treatment plant sludges

Reuse options were investigated for drinking water sludge. Research found sludges could be included with raw materials in brick and cement manufacturing with minimal impact. Poly-aluminium chloride sludge was found to an excellent adsorbent of phosphorus from wastewaters thus indirectly reducing potential algal blooms in our rivers.

Nutrient cycling in Lagoon of Islands, Tasmania : management to control

This research identified the causes of poor water quality and algal blooms in Lagoon of Islands, a small shallow lake in Tasmania. The findings of this research identified options for rehabilitation and remediation of the lake.

Managing alternative stable states in constructed wetlands using artificial substrates

Algal blooms are a management concern in shallow water bodies. This project investigated the use of artificial substrates to enhance biofilm growth and shift primary production from the open water to artificial surfaces. This resulted in a shift from algal dominated wetland back to a clear water macrophyte dominated wetland.

Annual phytoplankton and nutrient fluctuations in the Hopkins Estuary, South-West Victoria, Australia

The Hopkins River drains grazing farmland for most of its length. Nutrients and phytoplankton populations in the Hopkins Estuary are strongly affected by the hydrodynamic cycle. The findings of this research show that nutrient and chlorophyll a levels in the Hopkins Estuary are high enough to indicate that future algal problems may occur and that management of nutrients entering its catchment and improvement of river banks are of high importance.

Environmental influences on akinete germination and development in Nodularia spumigena (Cyanobacteriaceae), isolated from the Gippsland Lakes, Victoria, Australia

This study was carried out to investigate the genesis of N. spumigena blooms by specifically studying the effects of environmental variables (salinity, nitrogen, phosphorus and light) on the germination of N. spumigena akinetes. Optimal conditions for maximum germination and germling growth were determined by exposing akinetes to a range of salinities and nutrient (nitrogen and phosphorus) concentrations under two different irradiances. At pre-determined time periods, treatments were sampled and the percent germination and length of germlings assessed. The results indicated that akinete germination and germling growth were optimal at salinities from 5 to 25 and significantly reduced outside this range. A positive correlation in germination was observed with increasing nutrient (phosphorus and nitrate) concentration. Similarly, germling growth increased with increasing concentrations of both nutrients. Irradiance significantly influenced both germination and growth during salinity experiments, whereas in nutrient addition experiments, irradiance had no effect on germination; however, growth was significantly influenced during phosphorus addition experiments. Consequently, salinity and light appeared to be most critical in the germination process for N. spumigena akinetes, with phosphorus most important for germling growth. The study showed that N. spumigena may be able to germinate under environmental conditions outside its optimal range, but the growth of the germling is significantly reduced, which in turn suggests that its ability to form a bloom outside its optimal environmental conditions would also be greatly reduced.

Toxic marine microalgae and shellfish poisoning in the British isles : history, review of epidemiology, and future implications

The relationship between toxic marine microalgae species and climate change has become a high profile and well discussed topic in recent years, with research focusing on the possible future impacts of changing hydrological conditions on Harmful Algal Bloom (HAB) species around the world. However, there is very little literature concerning the epidemiology of these species on marine organisms and human health. Here, we examine the current state of toxic microalgae species around the UK, in two ways: first we describe the key toxic syndromes and gather together the disparate reported data on their epidemiology from UK records and monitoring procedures. Secondly, using NHS hospital admissions and GP records from Wales, we attempt to quantify the incidence of shellfish poisoning from an independent source. We show that within the UK, outbreaks of shellfish poisoning are rare but occurring on a yearly basis in different regions and affecting a diverse range of molluscan shellfish and other marine organisms. We also show that the abundance of a species does not necessarily correlate to the rate of toxic events. Based on routine hospital records, the numbers of shellfish poisonings in the UK are very low, but the identification of the toxin involved, or even a confirmation of a poisoning event is extremely difficult to diagnose. An effective shellfish monitoring system, which shuts down aquaculture sites when toxins exceed regularity limits, has clearly prevented serious impact to human health, and remains the only viable means of monitoring the potential threat to human health. However, the closure of these sites has an adverse economic impact, and the monitoring system does not include all toxic plankton. The possible geographic spreading of toxic microalgae species is therefore a concern, as warmer waters in the Atlantic could suit several species with southern biogeographical affinities enabling them to occupy the coastal regions of the UK, but which are not yet monitored or considered to be detrimental.

Changes in marine dinoflagellate and diatom abundance under climate change

Marine diatoms and dinoflagellates play a variety of key ecosystem roles as important primary producers (diatoms and some dinoflagellates) and grazers (some dinoflagellates). Additionally some are harmful algal bloom (HAB) species and there is widespread concern that HAB species may be increasing accompanied by major negative socio-economic impacts, including threats to human health and marine harvesting1, 2. Using 92,263 samples from the Continuous Plankton Recorder survey, we generated a 50-year (1960–2009) time series of diatom and dinoflagellate occurrence in the northeast Atlantic and North Sea. Dinoflagellates, including both HAB taxa (for example, Prorocentrum spp.) and non-HAB taxa (for example, Ceratium furca), have declined in abundance, particularly since 2006. In contrast, diatom abundance has not shown this decline with some common diatoms, including both HAB (for example, Pseudo-nitzschia spp.) and non-HAB (for example, Thalassiosira spp.) taxa, increasing in abundance. Overall these changes have led to a marked increase in the relative abundance of diatoms versus dinoflagellates. Our analyses, including Granger tests to identify criteria of causality, indicate that this switch is driven by an interaction effect of both increasing sea surface temperatures combined with increasingly windy conditions in summer.