MY RESEARCH PROJECT

DEVELOPMENT OF ESTUARINE NUTRIENT RESPONSE MODEL FOR CIRCULATION AND WATER QUALITY

PROJECT LEADER: DR. NOOR BAHARIM HASHIM
RESEARCHERS: PROF. MADYA DR. RAZALI ISMAIL, MAZNAH ISMAIL and ANIE RAFLIKHA ABDUL MALIK

KEYWORDS: Hydrodynamic, water quality, eutrophication, numerical model,estuary



OBJECTIVES:
1) To develop a hydrodynamic and water quality model
2) To verify the hydrodynamic and water quality model using intensive field survey
3) To determine the linkages between physical transport, nutrient input and dissolved oxygen dynamics.

LITERATURE REVIEW SUMMARY



In South East Asia, the incidence of eutrophication of coastal waters has increased dramatically in recent years. Occurrences of harmful algal blooms have been reported in Hong Kong (Lam and Ho, 1989; Ho and Hodgkiss, 1996) and Philippines (Bajarias and Relox, 1996). Between 1976 and 1991, there have been seven incidents of red tide outbreak in Sabah resulting in 12 fatalities from paralytic shellfish poisoning (PSP) and 200 cases of red tide related poisoning. During that period only one incident was recorded in the South China Sea area bordering the east coast of peninsular Malaysia, off the coast of the State of Terengganu (Choo, 1994). Choo (1994) noted that red tide incidents recorded off the west coast of Peninsular are associated with industrial pollution. Based on nutrient levels from field data and modeling results in the Straits of Johor and Singapore Straits, Cheong (2001) noted the likelihood of algal bloom in the region.

There is an increasing concern in Johor River Estuary that oversupply of nutrients from multiple sources is having pervasive ecological effects on the shallow coastal and estuarine areas. These effects include reduced light penetration, loss of aquatic habitat (submerged aquatic vegetation-seagrass), harmful algal blooms, a decrease in dissolved oxygen (hypoxia or anoxia), and impacts on living resources. Prolonged oxygen depletion can distrupt benthic and dermesal communities and cause mass mortalities of aquatic life. Hypoxia affects living resources, biological diversity, and the capacity of aquatic systems to support biological populations. Degraded water quality has adverse effects on critical habitats in Johor River Estuary such as seagrass, which is an essential food for dugong (Dugong dugon) and many herbivorous fish (i.e., rabbitfishes and wrasses). Hence, there is the need for comprehensive and intensive baseline studies of the water quality in the Johor River Estuary in order to assess the impact of all existing and future developments on the ecology of the Johor estuarine and coastal waters.



In order to understand the long-term response of the coastal ecosystem to anthropogenic activities and to assess a threat of eutrophication of the Johor River Estuary, it is necessary to establish up-to-date baseline conditions of the physical, chemical, and biological parameters in the estuarine and coastal waters over a range of space and time scales. These data are important for quantification of the eutrophication processes and for proper management of marine ecosystems.



In order to predict phytoplankton and nutrient concentrations in Johor River Estuary, it is necessary to use a hydrodynamic and eutrophication model, coupling major physical, chemical, and biological processes. In this study, a multi- imensional, finite-difference model will be developed for Johor River Estuary. The model source code will be written in FORTRAN 77. The generic source code will be compiled and executed on PC compatible. The source code will be compiled by using Absoft and Lahey compilers. The model will solve the multi-dimensional, vertically hydrostatic, free-surface, turbulent averaged equations of motions for a variable density fluid. Dynamically coupled transport equations for turbulent kinetic energy, turbulent length scale, salinity and temperature will also be solved. The model will use a stretched vertical coordinate and Cartesian or curvilinear, orthogonal horizontal coordinates and allowed for wetting and drying in shallow areas by a mass conservation scheme. The model will implement a second order accurate in time and space, mass conservation fractional step solution scheme for the Eulerian transport equations for salinity, temperature, suspended sediment, water quality constituents, and toxic contaminants. Horizontal boundary conditions for the model will include time variable material inflow concentrations, upwinded outflow, and a damping specification of climatological boundary concentration.

The developed model will be tested against several analytical solutions. The model will be applied to Johor River estuary. The Johor River Estuary model will be calibrated and verified using two different intensive surveys. Descriptive statistics will be conducted to provide detail on model performance. Additionally, regression analysis will be used to determine how well the model accounted for variability in the field data.

Experimentation with the model will be conducted to determine the influence that discharge and wind each had on lateral salinity variation in the estuary. After the model was validated, it will be utilized to study the linkages between physical transport and mixing, nutrient inputs, phytoplankton growth and dissolved oxygen dynamics.