QE: Toxic cyanobacteria in Singapore’s reservoirs: effects of ecological variables on population growth and toxin production (Maxine Allayne Darlene Mowe, 28 June 2012: 10.00am)

Department of Biological Sciences, NUS
Qualifying Examination

Toxic cyanobacteria in Singapore’s reservoirs: effects of ecological variables on population growth and toxin production
Speaker:               Maxine Allayne Darlene Mowe (Graduate Student, Dept. of Biological Sciences, NUS)
Date:                    28 June 2012, Thursday
Time:                   10am
Venue:                 DBS Conference Room (S3 Level 5, #05-01)
Supervisor:         Assistant Prof. Darren Yeo (NUS)
Co-supervisors:   Assistant Prof. Peter Todd (NUS), Sr. Lecturer Simon Mitrovic (UTS), Assoc Prof. Richard Lim (UTS)

Abstract:

Singapore has 17 reservoirs, with a combined catchment amounting to two-thirds of the city state’s total land area. With more unprotected catchments in urban areas, the likelihood of anthropogenic nutrient input to the reservoirs has increased. Nutrient input is one of the many factors that leads to harmful algal blooms, which have been recorded over the past 20 years in various local reservoirs. Although the trophic status of some reservoirs has improved, others are encountering eutrophication problems (Yang & Chiam- Tai 1991).

There are a variety of causes behind harmful algal blooms, which are frequently dominated by cyanobacteria, in Singapore’s reservoirs; it is often not one causative factor that triggers a bloom, but the combination of several. Factors that play a role in increasing the occurrence and severity of cyanobacterial blooms include increased phosphorous, nitrogen and micronutrient loads from runoff (Downs et al. 2008). Ecological interactions between the cyanobacterial species and herbivorous zooplankton may also influence the ability of cyanobacterial species to dominate the phytoplankton community (Kirk & Gilbert 1992).

To understand the effects of this range of environmental factors on harmful cyanobacterial blooms in Singapore, water sampling will be carried out and individual strains of toxic cyanobacteria will be isolated in the laboratory. Once isolated, approximately 10 cyanobacterial species will be cultured ex situ under different environmental conditions. Toxin production and growth will be monitored with changing environmental parameters such as light, temperature, macronutrients (nitrogen and phosphorous). Extensive laboratory manipulations will then be carried out in order to ascertain the conditions for optimal toxin production of the isolated cyanobacterial species.

The study will be carried out over all reservoirs to pinpoint the level of possible harmful algal bloom formation for each species. Using the cultured strains, microcosm experiments with herbivorous zooplankton will be carried out, in order to ascertain if the presence of zooplankton causes an increase in toxin production of cyanobacteria. Hypotheses based on the findings from the manipulative laboratory experiments will be tested with in-situ exclusion experiments using limnocorrals to be placed in various reservoirs. The outcome of this study would help to inform raw water management practices for prevention or control of cyanobacterial blooms in Singapore reservoirs.

All are welcome

Thu 28 June 2012: 10.00am @ DBS_CR – Maxine Mowe on “Toxic cyanobacteria in Singapore¹s reservoirs: effects of ecological variables on population growth and toxin production”

Department of Biological Sciences, NUS
Qualifying Examination

“Toxic cyanobacteria in Singapore’s reservoirs: effects of ecological variables on population growth and toxin production”

By Maxine Allayne Darlene Mowe
Graduate Student, Dept. of Biological Sciences, NUS
Supervisors: Darren Yeo (NUS), Peter Todd (NUS), Simon Mitrovic (UTS) & Richard Lim (UTS)

Thu 28 June 2012: 10.00am
DBS Conference Room (S3 Level 5, #05-01)
Map: click

All are welcome

Abstract:
Singapore has 17 reservoirs, with a combined catchment amounting to two-thirds of the city state’s total land area. With more unprotected catchments in urban areas, the likelihood of anthropogenic nutrient input to the reservoirs has increased. Nutrient input is one of the many factors that leads to harmful algal blooms, which have been recorded over the past 20 years in various local reservoirs. Although the trophic status of some reservoirs has improved, others are encountering eutrophication problems (Yang & Chiam- Tai 1991).

There are a variety of causes behind harmful algal blooms, which are frequently dominated by cyanobacteria, in Singapore’s reservoirs; it is often not one causative factor that triggers a bloom, but the combination of several. Factors that play a role in increasing the occurrence and severity of cyanobacterial blooms include increased phosphorous, nitrogen and micronutrient loads from runoff (Downs et al. 2008). Ecological interactions between the cyanobacterial species and herbivorous zooplankton may also influence the ability of cyanobacterial species to dominate the phytoplankton community (Kirk & Gilbert 1992).

To understand the effects of this range of environmental factors on harmful cyanobacterial blooms in Singapore, water sampling will be carried out and individual strains of toxic cyanobacteria will be isolated in the laboratory. Once isolated, approximately 10 cyanobacterial species will be cultured ex situ under different environmental conditions. Toxin production and growth will be monitored with changing environmental parameters such as light, temperature, macronutrients (nitrogen and phosphorous). Extensive laboratory manipulations will then be carried out in order to ascertain the conditions for optimal toxin production of the isolated cyanobacterial species. The study will be carried out over all reservoirs to pinpoint the level of possible harmful algal bloom formation for each species.

Using the cultured strains, microcosm experiments with herbivorous zooplankton will be carried out, in order to ascertain if the presence of zooplankton causes an increase in toxin production of cyanobacteria. Hypotheses based on the findings from the manipulative laboratory experiments will be tested with in-situ exclusion experiments using limnocorrals to be placed in various reservoirs. The outcome of this study would help to inform raw water management practices for prevention or control of cyanobacterial blooms in Singapore reservoirs.

Lynette’s Sea Wall project in the news (Straits Times)

Turning sea walls into ‘housing’ units for marine life
by Jose Hong. The Straits Times, 05 Jun 2012.

SEA walls defend the coast from erosion by waves and currents, but they are also potentially ‘housing developments’ for marine creatures.

These ‘housing developments’, however, are not ideal habitats. This is because the granite blocks making up these sea walls have steeply sloped, even surfaces – not the best for sea life looking for crevices to anchor themselves, feed, breed, or hide.

Research assistant Lynette Loke, a 24-year-old doing her master’s in science at the National University of Singapore (NUS), wants to change that.

Ms Loke in the middle of mounting specially designed tiles onto sea walls at Pulau Hantu as part of her project in 2009. Designed and created by her, the tiles have ridges and pits which make them a more complex surface than granite for sea life looking for crevices to anchor themselves, feed, breed, or hide. Photo: Peter Todd

Her project now basically ‘renovates’ the sea walls by mounting specially designed tiles onto their surface. Designed and created by her, these tiles are moulded with ridges and pits, making them a more complex surface than just granite alone.

She has been at this for 21/2 years, and will complete an analysis of the effectiveness of the tiles only next year.

But her project has already garnered international praise.

Professor Gee Chapman, a professor of marine ecology at the University of Sydney, was impressed by the project when she visited NUS in March.

She said the research would answer important questions about how plant and animal species that live between the high- and low-tide levels use their habitats.

‘More importantly, the results will provide advice to ecologists, engineers and environmental managers worldwide about ways in which sea walls might be modified or built to reduce their negative effects on local inter-tidal biodiversity,’ she added.

Dr James Reimer, an associate professor at the Molecular Invertebrate Systematics and Ecology Lab of the University of the Ryukyus in Japan, has also come to hear of Ms Loke’s work.

Saying the project fit well with his work of assessing the impact of coastal construction on marine biodiversity, he invited the principal investigator of the project, NUS assistant professor of biology Peter Todd, to give a talk on the project in April.

Dr Reimer, noting the talk was well-received, said: ‘We’re discussing ways to apply their methods to a project here in Okinawa.’

Dr Tjeerd Bouma, a co-principal investigator for Ms Loke’s project, noted that sea walls have been built for decades with little thought to their impact on marine life. Dr Bouma,who is a researcher from the Royal Netherlands Institute for Sea Research and Deltares, said learning how to design these walls in the most ecologically friendly way was therefore important.

Ms Loke cannot agree more, adding: ‘We hope one day to see our design on seawalls around the world.’

Lady McNeice Yuen-Peng, RIP

Lady McNeice, a benefactor to the natural history community, has passed away on Sunday, 3rd June 2012. Many of us in the Department of Biological Sciences have benefited from her generosity and kindness when we were students and after. She was “an ardent supporter in local conservation and a firm believer in investing in young talent”.

We were very glad for the opportunity to acknowledge her role at the Biodiversity of Singapore Symposium I in July 2003. With the help of Ng Bee Choo and Tan Week Kiat, we surprised her with a symbolic gift, an etching of Orcovita mcneiceae, a new species named after her by Ng Ngan Kee and Peter Ng in 2002.

Like many others, we were touched by her wide and enthusiastic participation for a better Singapore over the many decades. We will remember her fondly always.

For more links, see Raffles Museum News.