The Monitoring of Harmful Algae Blooms in Sabah, Malaysia

The first record of harmful algae bloom (HAB) in Sabah was in 1976 where 202 victims were reported to be suffering from Paralytic Shellfish Poisoning (PSP) and 7 deaths. The causative organism was Pyrodinium bahamense, a dinoflagellate which produces saxitoxin. Since then, Department of Fisheries Sabah has been doing monitoring to safeguard seafood safety, especially shellfish harvested for food consumption. Cochlodinium polykrikoides bloom for the first time in Sabah in year 2005 where Kota Kinabalu and Tuaran experienced fish kill. Since then, other HAB species such as Gymnodinium catenatum, Gonyaulax polygramma and Noctiluca scintillans were identified in waters of Sabah. Sabah is the only state in Malaysia in which the monitoring program is done consistently throughout the year since 1976. Samples were collected once or twice a month, according to high and low risks areas which have been identified, most of which are in the west coast. The collection frequency may be increased depending on the situation such as whether there is an outbreak of red tide or PSP in the area. Due to this effort, PSP cases involving the public have declined during the last 40 years without duly affecting the income of fishermen and the fisheries industry. After successfully implementing toxin monitoring between 1984 to 2013, it recurred back in 2013 when 3 deaths were reported. The purpose of this paper is to review all HABs incidences that occured in Sabah over the last few years from January 2000 – December 2017.


Introduction
Harmful algal bloom (HAB) occur when there is an increase of phytoplankton abundances in natural marine or freshwater environments. It causes toxic or harmful effects on people, fish, shellfish, marine mammals and birds. Some microalgae species produces toxins and bioaccumulate in shellfish and cause harm to people who consume them. Other species of microalgae causes fish kill by clogging their gills and they die from lack of oxygen.
Paralytic shellfish poisoning (PSP) is caused by consuming bivalve mollusks (mussels, clams) which are contaminated with saxitoxins (STX). PSP toxins accumulated in shellfish because of filtration of toxic algae produced by several dinoflagellates (including Alexandrium, Gymnodinium and Pyrodinium). The first PSP case in Sabah caused by Pyrodinium bahamense was recorded in 1976 where 202 victims were reported to be suffering from PSP and seven deaths [1]. Paralytic shellfish poisoning was only confined to the west coast of Sabah until 1990. In early 1991, Peninsular Malaysia experienced the first recorded red tide event, where three people became ill after consuming farmed mussels from Sebatu, Malacca caused by Alexandrium tamiyavanichii. West coasts of Sabah have been experiencing HABs annually for the past four decades since then. The presence of HABs in Sabah occurs sporadically since 1976, but the pattern of occurrence was different from district to district. The east coast of the state is considered low risk area as no occurrence had happen before. The west coast is considered a highrisk area for HAB and PSP.  [2] where Kota Kinabalu and Tuaran experienced fish kill. Sabah Fisheries Station which was situated in Tanjung Badak, Tuaran suffered a huge loss due to the mass fish mortality. Other fish cage farmers in Kota Kinabalu and Tuaran areas were caught unprepared during the bloom. However, no data on scale of damage was obtained. In 2014, Tanjung Kupang, Johor, massive fish kills were caused by Karlodinium australe bloom which has never been reported as toxic. Reported losses were amounting to RM150,000 according to fish cage operators.
The purpose of this paper is to review all HABs incidences that occured in Sabah over the last few years from January 2000 -December 2017.

Red tide monitoring system
Red tide monitoring has been conducted by Department of Fisheries Sabah (DOFS) since 1976 to safeguard seafood safety, especially shellfish harvested for food consumption. Table 1 shows summary of coastal fisheries district offices in Sabah. The red tide monitoring area covers all the Sabah coasts and has been regularly conducted at 69 monitoring stations (under the responsibility of 13 fisheries district offices) since 1976 ( Figure 1). Sabah is the only state in Malaysia in which the monitoring program is done consistently throughout the year since 1976. Red Tide and Public Health lab which is situated in Likas Fisheries Complex is the main laboratory to conduct PSP and HAB analysis under the supervision of Sabah Biosecurity Fisheries Division. DOFS have been collaborating with Ministry of Health Sabah (MOHS) in monitoring, mitigating and managing red tide occurrences in Sabah to take care of the public health and protect the local fisheries industry. Due to this effort, PSP cases involving the public have declined during the last 40 years without duly affecting the income of fishermen and the fisheries industry.  Figure 1. The 13 strategic coastal fisheries district offices along the Sabah coast that has been conducting monitoring since early 1976.
DOFS is primarily in charge of routine red tide monitoring. Thirteen strategic coastal fisheries district office are responsible for HAB monitoring, mainly targeting potential areas where there have been frequent red tides. Sampling was done once a month for low risk areas (East Coast of Sabah -4 sites) and twice a month for high risk areas (West Coast of Sabah -9 sites). All samples were collected by the appointed personnel from respective district offices and sent to Likas Fisheries Complex for analysis. In addition, once there is PSP case, MOHS joins the red tide monitoring program by collecting and sending HAB or PSP samples to DOFS laboratory for analysis. Table 2 shows the red tide monitoring program conducted by agencies in Sabah where three types of red tide monitoring have been conducted since 1976.

Red tide alert system
Presently, the Assistant Director of Sabah Biosecurity Fisheries Division will issue out letter to the respective fisheries district offices to increase monitoring frequency as early precautionary measure when the cell densities of P. bahamense and C. polykrikoides exceeds 1,000 cells/L. The fisheries district office will also inform the District Officer, village heads, chairman of village community and district Health Office to take necessary precaution to refrain from eating shellfish from affected district. When both cell densities of P. bahamense exceeds 7,000 cells/L and collected shellfish sample toxicity level from the same area exceeds 80 μg Poison/100 g meat, the Director of DOFS will issue a press statement to advise the public from consuming any type of shellfish or bivalves from the affected areas, besides banning of selling and collection of shellfish. For C. polykrikoides, once the cell densities exceed 5,000 cells/L, the Assistant Director of Sabah Biosecurity Fisheries Division will issue out letter to the respective fisheries district offices to increase monitoring frequency and the district offices will take immediate action to notify fish cage farm operators to take precautionary measure such as harvesting of fish or to move their cage away from affected areas. Warning will be lifted once cell density and PSP toxicity level are lower than the safety limit for three consecutive weeks. Table 3 summarizes the red tide warning standards in Sabah since 1976. When cell density lower than safety level for 3 consecutive weeks.

Materials and Method
Environmental data of pH, dissolved oxygen (DO) and temperature were recorded in-situ at two meters depth from surface using Hydrolab Quanta Multi-Probe Meter (OTT Hydromet, Germany). Phytoplankton samples were collected vertically with a 2.5 L Van Dorn water sampler at 1 m and 3 m water depth. Sedgewick-rafter counting chamber was used for cell counting and species identification. Qualitative and quantitative analysis of phytoplankton was performed using a normal light microscope (Leica Microsystems, Wetzlar, Germany). The smallest algae were counted under 40x and the larger ones under 10x. The bloom density was determined by direct cell counts of target species [3].
Mouse-bioassay (MBA) was adapted since 1976 until to date according to AOAC (Association of Official Analytical Chemists) Official Method 959.08 to determine PSP toxicity level [4]. Strain of mice used were Balb C and cultured in Likas Fisheries Complex prior analysis. Stock of mice were sometimes an issue and DOFS is in the process of using LC-MS/MS analysis in the future. Before this, all results were expressed in MU/100 g and since 2015, results were expressed as μg Poison/100 g meat. Any value above 80 μg/100 g meat was considered hazardous and unsafe for human consumption.

Results and discussion
During the red tide events on March -April 1976, surface temperature was reported around 28.5 °C with pH was constant at 8.1. Surface salinity ranged from 33-35 ppt and dissolved oxygen was around 4.1 mL/L [5]. No environmental data was obtained until 2016. Environmental data was collected on September 2017 in Kota Kinabalu where surface temperature ranged from 23.6-25.5°C. Range of pH and dissolved oxygen were recorded at pH 7.23-8.55 and 4.57-6.95 mg/L respectively. No surface salinity data was taken.

Red tide seasons
The monthly variations of red tide events in the coastal water of Sabah over the years is shown in figure  3. Sabah is under the influence of monsoons namely northeast monsoon from November to March, southwest monsoon from May to September and inter-monsoon (April and October). From 2000 to 2017, more than 70% (2,142 events in total) of the red tide events occurred during wet season. The greatest number of red tide events has occurred in January (25%) and the lowest was found in November (2%). During dry season, the number of red tide events started to increase from May (74 events in total), reached the highest in August (183 events in total) and started to fluctuate until October (85 events in total). While for wet season, it started to increase from November (64 events on total), highest in January (756 events in total) and lowest in April (259 events in total). The overall trend of red tide events can be seen in both seasons and started to increase after inter-monsoon. Numerous of studies had been done on triggering factors of Pyrodinium blooms such as nutrient concentrations, water parameters, monsoon season and geomorphology of the locations [6]. [7] stated that these monsoons have been reported to be responsible for the Pyrodinium blooms, particularly in Sabah. [8] found out that P. bahamense occurred during both northeast and southwest monsoon periods, but no clear combination of environmental conditions was observed. Rainfall was found to trigger the occurrence of C. polykrikoides blooms after one or two days caused by high amount of nutrients through run-off [9].