Journal of Survey in Fisheries Sciences 7(2) 231-247 2021 Causes of fish kills in , in year 2019, in conjunction to Typhoon Lekima

Aileen Tan S.H.1, 2*; Sim Y.K.1; Norlaila M.Z.1; Nooraini I.1; Masthurah A.1; Nur Aqilah M. D.1; Nithiyaa N.1; Noraisyah A.B.3

Received: July 2020 Accepted: December 2020

Abstract Mass fish mortalities was recorded, a day after the Typhoon Lekima passed the coastal areas at Penang, Malaysia in August 2019, which caused huge losses among the fish culturists. Being within the vicinity of a National Park, one would think that the water qualiy around a protected area should be of pristine quality but obviously it is not. Scientists and researchers from both Universiti Sains Malaysia and Department of Fisheries, with the help from NaFish have conducted several tests on the water and fish. The dead cultured fishes were mainly groupers, which prefer to stay at the bottom of the nets. The storm created by Typhoon Lekima had churned up all sediments in the shallow coastal areas. This had caused additional sediment and nutrients in the ecosystem, leading to algal bloom and also depletion of oxygen levels in the water, causing mass fish mortality. Water quality monitoring (physical, chemical and biological) was conducted along the coastal areas as well as extending towards the sea and at different depth to further understand the causes of fish kills over a period of three weeks after the incident. Sampling was done 3-days, 11-days and 26 days after the typhoon, Results had shown extremely low dissolved oxygen and high concentrations of nitrate, nitrite and chlorophyll a recorded after the typhoon. However, water quality slowly became normal and within the Malaysian Marine Water Quality Criteria & Standard for Class 2- Marine Life, Fisheries, Coral Reefs, Recreational & Mariculture.

Keywords: Mass mortality of fish, Hypoxia, Eutrophication, Algal bloom

Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] 1-Centre for Marine & Coastal Studies, Universiti Sains Malaysia, 11800 Penang, Malaysia. 2-School of Biological Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia 3-Department of Fisheries Malaysia, Penang State Fisheries Office, Jalan Akuarium, Kampung , 11700 Gelugor, Penang, Malaysia. * Corresponding author’s Email: [email protected] 232 Aileen Tan et al., Causes of fish kills in Penang, Malaysia in year 2019, in conjunction to …

Introduction upwelling, terrestrial runoff particularly Fisheries are an important sector in increase in nutrient concentration, and Malaysia, contributing to the economic sediment resuspension, which affect growth, employment, and also as food marine ecosystems to some extents source. In the year 2017, Penang was (Lim et al., 2015; Aoki et al., 2019). ranked as the third highest in the An intensive field investigation in country for the wholesale value of fish the area was conducted on the very next th production, 96,970.4 metric tonnes, day, 11 August 2019 on the water values at RM1.4billion (DOF, 2017; quality and also fish samples by Centre Negin, 2019). The sector, particularly for Marine and Coastal Studies aquaculture industry in Penang has kept (CEMACS), Universiti Sains Malaysia expending annually to meet both (USM). The present study investigates domestic and international demand. the connection between the substantial Teluk Bahang, Penang, is a coastal effects of typhoon, environmental town located off the north western coast changes in water quality, phytoplankton of Peninsular Malaysia in Straits of density and the massive fish kill event Malacca. This area resided by fishing that took place in Teluk Bahang. We communities and about five villages aim that our findings will provide basis with 244 households (Farhana et al., in finding an adaptive solution to such 2012). Massive fish kills alarmed the incident in near future. area for the second time on 10th August 2019 after the first incident in April Materials and methods 2019. The occurrence and reoccurrence Study stations of fish kills has resulted in considerable The water quality monitoring was done public concern. In this incident all the using a 2-dimensional approach i.e. six fish culturists in the vicinity of along the coastal areas, towards the Teluk Bahang were badly impacted. ocean from shore and the depth profile (Fig. 1a and Fig. 1b). The details of the This not only involved commercially sampling stations are shown in Table 1. important fishes such as groupers and Water samples were collected both snappers, but also wild fishes in the from the surface and bottom. Results surrounding environment. were presented as depth profile as well This massive fish kill event as distance from the shoreline. coincides with the storm brought on by

Typhoon Lekima, which hit Penang Sampling methods Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] Island on 9th August 2019. All the Both surface and bottom of seawater coastal areas of samples were collected on 13 August experienced heavy rain, strong wind of 2019, 21 August 2019 and 5 September 100 kph, and strong waves from around 9 p.m. till midnight (Loh, 2019). Storms 2019 respectively at a transect sites brought by typhoons could cause along the coastline and also environmental changes such as perpendicular to the shore (Fig. 1b). Journal of Survey in Fisheries Sciences 7(2) 2021 233

Figure 1a: Location of Penang, Malaysia.

Figure 1b: Sampling points for water quality (13th Aug, 21st Aug & 05th Sep 2019; 0900am – 1200pm).

Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] Table 1. Maximum depth (m) of each sampling station during sampling and periods. Maximum depth (m) Station 13 August 2019 21 August 2019 05 September 2019 River mouth 1.6 1.2 0.7 Teluk Bahang (fish farm) 4.2 3.1 2.9 CEMACS jetty 3.3 3.0 2.2 4.4KM from shoreline* 9.5 8.1 8.4 5.4KM from shoreline* 11.8 10.4 11.1 6.8Km from shoreline* 13.0 10.8 12.5 *Reference point for Shoreline located at Teluk Bahang with Lat: 05°27’34”N & Long: 100°12’32”E 234 Aileen Tan et al., Causes of fish kills in Penang, Malaysia in year 2019, in conjunction to … Triplicate samples were collected each the absorbance of the solution using a 1 for surface and bottom of seawater prior cm quartz cuvette and distilled water as to water quality analysis. Water blank for all nutrient analysis. samples for bottom depth were All the readings were compared to the collected using a Van Dorn water Malaysia Marine Water Quality Criteria sampler. For both surface and bottom of & Standard (MMWQCS) for CLASS 2 seawater samples, 500 mL polyethylene - Marine Life, Fisheries, Coral Reefs, bottles were rinsed with seawater prior and Recreational & Mariculture to seawater collection (n=3). The (Ministry of Environment, 2005); bottles were labelled and stored in an  Dissolved oxygen - 5.00 mg/L ice box at 0°C to inactivate bacterial  Water temperature - ≤ 2°C increase activities during the sampling occasion. over maximum ambient All water samples for nutrient analysis  Ammonia (unionized) - 0.07 mg/L were immediately filtered upon arrival  Nitrate (NO3) - 0.06 mg/L at the laboratory and were stored in a -  Nitrite (NO2 ) - 0.055 mg/L deep freezer. All the samples were 3-  Phosphate (PO4 ) - 0.075 mg/L analyzed within a period of one month. During the collection of water samples Surface and bottom seawater samples at the various sampling stations, the in- were collected to an aliquot of 1L situ physical parameter readings such as volume using a Van Dorn sampler for dissolved oxygen (DO), salinity and phytoplankton analyses. Upon reaching temperature were taken using YSI to the laboratory, the seawater samples ProPlus water quality meter. were pre-concentrated through 120-μm Measurements for dissolved oxygen and 15-μm mesh sieves. The samples (mg/L) were done with YSI ProPlus were then preserved with Lugol’s unit with Polarographic DO sensor; the iodine solution for phytoplankton probe was calibrated before every field density and composition analyses. Cell sampling. The values taken for counts were performed using a dissolved oxygen at 100% air saturation Sedgewick-rafter chamber under a - 6.95mg/L. Meanwhile, measurements trinocular inverted light microscope for pH reading were done in laboratory (Motic AE2000). Identification was using calibrated Mettler Toledo pH carried out until species levels meter. whenever possible following Tomas Analysis of nitrite, nitrate, phosphate (1997), Omura et al. (2012), and Tan et Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] and ammonia were carried out using the al. (2016). standard titration method modified from Results from the water samples Strickland and Parsons (1972) and Hing taken on 13 August (3 days after event et al. (2012) in order to determine the of fish kills), 21 August (11 days after nutrient conditions of the seawater. A the event) and 5 September 2019 (26 spectrophotometer (UVmini-1240, days after the event) were presented. Shimadzu, Japan) was used to measure Journal of Survey in Fisheries Sciences 7(2) 2021 235

More detail sampling sites were dissolved oxygen levels were extremely conducted and a projection of 2-D low (below 5 mg/L) from the river results (distance from shoreline and mouth till about 5.4km offshore, depth profile) was presented. especially at the bottom on 21 August Notes to the sampling dates: 2019 (11 days after Typhoon Lekima), 13th August 2019 (3 days after the dissolved oxygen levels recorded typhoon): Close to spring tide/ Flooding were mainly above the MMWQCS tide (Class 2) of 5mg/L. On 5 September 21st August 2019 (11 days after 2019 (26 days after Typhoon Lekima), typhoon): Close to neap tide / Flooding the dissolved oxygen levels recorded tide were all above the MMWQCS (Class 2) 05th September 2019 (26 days after of 5mg/L. typhoon): Close to neap tide / Ebbing tide Turbidity Figure 3 shows the results of turbidity Results measurements at the sampling stations. Temperature and salinity On 13 August 2019, the turbidity levels Average water temperature recorded were higher at the distance of 4.4.km from range 30.20 - 30.70 °C (Surface - till 6.8km offshore (above 20 NTU), 4.0m depending on depth of station) on especially at the bottom. On 21 August 13 August 2020 and 30.30 - 30.70 °C 2019, the turbidity levels recorded were (Surface - 4.0m depending on depth of generally below 20 NTU. On 5 station) on 21 August 2020. Average September 2019, the turbidity levels water temperature slightly low on 5 were low at the surface but were around September 2019 from range 30.00 - 3-40 NTU around the bottom at the 30.20 °C (Surface - 4.0m depending on distance of 2 km till 5.5 km offshore. depth of station) compare to previous sampling dates. Salinity was consistent pH throughout the sampling period range Figure 4 shows the pH levels at all the from 29.89 - 30.52 ppt (13 August sampling stations during the three 2020); 29.32 - 30.40 ppt (21 August sampling events. On 13 August 2019, 2020) and 29.28 - 30.34 ppt (5 the pH levels were more towards acidic September 2019). Salinity recorded especially near the river mouth, both from river mouth slightly low (29.28 - surface and bottom. This is not Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] 30.33 ppt) compare to other stations. surprising due to the heavy rainfall a couple of days before the sampling Dissolved oxygen date. On 21 August 2019, the pH level Figure 2 shows the dissolved oxygen has shown signs of approaching the levels recorded during the water quality normal seawater pH, which is slightly monitoring. On 13 August 2019 (3 alkaline. On 5 September 2019, the pH days after Typhoon Lekima), the levels seemed to be at normal level. 236 Aileen Tan et al., Causes of fish kills in Penang, Malaysia in year 2019, in conjunction to …

Figure 2: Concentration of Dissolved Oxygen (mg/L) at different depths from 0-7KM distance from shoreline (Lat: 05°27’34”N/Long: 100°12’32”E). Graph generated using Ocean Data View ODV 5.1.7 from coordinates and water samples measured on 13th Aug, 21st Aug & 05th Sep 2019.

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Figure 3: Turbidity (NTU) level at different depths from 0-7KM distance from shoreline (Lat: 05°27’34”N/Long: 100°12’32”E). Graph generated using Ocean Data View ODV 5.1.7 from coordinates and water samples measured on 13th Aug, 21st Aug & 05th Sep 2019.

Journal of Survey in Fisheries Sciences 7(2) 2021 237

Figure 4: The pH level at different depths from 0-7KM distance from shoreline (Lat: 05°27’34”N/Long: 100°12’32”E). Graph generated using Ocean Data View ODV 5.1.7 from coordinates and water samples measured on 13th Aug, 21st Aug & 05th Sep 2019.

Ammonia Figure 5 shows the ammonia levels at Nitrate all the sampling stations during the Figure 6 shows the nitrate levels monitoring duration. On 13 August recorded at all the sampling sites during 2019, the ammonia levels were above the three sampling events. On 13 the 0.07mg/L MMWQCS standard for August 2019, the nitrate levels were Class 2 water quality. Higher levels of overall above the 0.06mg/L MMWQCS ammonia were recorded beyond 6km standard for Class 2 water quality. On offshore (both surface and bottom). On 21 August 2019, the nitrate levels were 21 August 2019, the ammonia level has within the Class 2 MMWQCS shown signs of approaching the normal Standards except for samples taken Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] seawater ammonia. On 5 September from the river mouth. On 5 September 2019, the ammonia levels were very 2019, the nitrate levels seemed to be at high and the concentration had normal level. increased starting from the fish farm towards offshore (both bottom and surface samples). 238 Aileen Tan et al., Causes of fish kills in Penang, Malaysia in year 2019, in conjunction to …

Figure 5: Concentration of Ammonia NH3 (mg/L) at different depths from 0-7KM distance from shoreline (Lat: 05°27’34”N/Long: 100°12’32”E). Graph generated using Ocean Data View ODV 5.1.7 from coordinates and water samples collected on 13th Aug, 21st Aug & 05th Sep 2019.

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Figure 6: Concentration of Nitrate NO3 (mg/L) at different depths from 0-7KM distance from shoreline (Lat: 05°27’34”N/Long: 100°12’32”E). Graph generated using Ocean Data View ODV 5.1.7 from coordinates and water samples collected on 13th Aug, 21st Aug & 05th Sep 2019. Journal of Survey in Fisheries Sciences 7(2) 2021 239

Nitrite quality. On 21 August 2019, the nitrite Figure 7 shows the results of nitrite levels for all sampling sites and depth concentrations at all sampling stations were within the Class 2 MMWQCS throughout the monitoring period. On Standards. On 5 September 2019, the 13 August 2019, the nitrite levels were nitrate levels seemed to be at normal overall above the 0.055mg/L level but the levels bottom samples of MMWQCS standard for Class 2 water offshore sites were slightly higher.

Figure 7: Concentration of Nitrite NO2- (mg/L) at different depths from 0-7KM distance from shoreline (Lat: 05°27’34”N/Long: 100°12’32”E). Graph generated using Ocean Data View ODV 5.1.7 from coordinates and water samples collected on 13th Aug, 21st Aug & 05th Sep 2019.

Phosphate 13 August and exceeded the Class 2 Figure 8 shows the phosphate levels at MMWQCS Standards. Highest Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] all sampling stations. On 13 August concentration was recoded near surface 2019, the phosphate levels were overall till 4 m for samples taken from the river above the 0.075mg/L MMWQCS mouth. On 5 September 2019, the standard for Class 2 water quality. On phosphate levels seemed to be below 21 August 2019, the phosphate levels the 0.075mg/L MMWQCS Standard were higher compared to results on date Class 2. 240 Aileen Tan et al., Causes of fish kills in Penang, Malaysia in year 2019, in conjunction to …

3- Figure 8: Concentration of Phosphate PO4 (mg/L) at different depths from 0-7KM distance from shoreline (Lat: 05°27’34”N/Long: 100°12’32”E). Graph generated using Ocean Data View ODV 5.1.7 from coordinates and water samples collected on 13th Aug, 21st Aug & 05th Sep 2019.

Chlorophyll a concentration 21 August 2019, the chlorophyll-a Chlorophyll-a is a measure indicating levels were overall high, with the the present of phytoplankton in the highest concentration recorded around water. Figure 9 shows the the river mouth towards the fish farm. concentrations of chlorophyll a at all However, the coverage of high density the sampling stations during all the of chlorophyll-a was lower on 21 sampling events. On 13 August 2019, August compared to samples collected

Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] the chlorophyll-a levels were overall on 13 August. On 5 September 2019, high especially from surface to bottom the chlorophyll-a levels seemed to be at the sites of river mouth, fish farm reduced in concentrations. until about 2.5km from shoreline. On Journal of Survey in Fisheries Sciences 7(2) 2021 241

Figure 9: Concentration of Chlorophyll-a (mg/L) at different depths from 0-7KM distance from shoreline (Lat: 05°27’34”N/Long: 100°12’32”E). Graph generated using Ocean Data View ODV 5.1.7 from coordinates and water samples collected on 13th, 21st Aug and 5 September 2019.

Phytoplankton density and observation dominance of phytoplankton shift The phytoplankton was predominantly towards Chaetoceros spp. with high cell centric diatom and some pennate density of 950,000 cells/L, followed by diatom. No known harmful or Eucampia sp. with 314,286 cells/L. ichthyotoxic dinoflagellate or Raphidophyte Chattonella sp. was raphidophytes species were observed in observed but in acceptable amount of the samples collected on 13 August 1,471 cells/L. On 5 September 2019,

Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] 2019. Figure 10 shows the phytoplankton were dominated by phytoplankton samples were observed Guinardia sp. with cell density of under compound light microscope. 61,945 cells//L. Raphidophyte, Centric diatoms, Coscinodiscus spp. Chattonella sp. was observed but in dominated with cell density of 32,243 acceptable amount of 2,728 cells/L. cells/L. On 21 August 2019, the 242 Aileen Tan et al., Causes of fish kills in Penang, Malaysia in year 2019, in conjunction to …

Figure 10: Phytoplankton composition collected on 13 August 2019, reflecting a dominance of centric diatoms, Coscinodiscus spp.

Discussion kills been reported in the study area. The results of the event and after the However, the dissolved oxygen event (11 days and 26 days after the concentrations were shown to be event) had been compared and a clearer recovering (DO between 3.5-4.5 mg/L) picture to address the issues of fish kills during the sampling at 11 days after the at Teluk Bahang had been generated. fish kills been reported and became The results had shown that the water stable or return to permissible values quality at the studied locations are (DO between 5-6 mg/L) by day 26. DO mostly exceeded the recommended is important to marine life and to limits of MMWQCS standard for Class primary productivity. DO affect 2 water quality (for aquaculture and primarily the composition and recreation), especially for dissolved decomposition of organic matter, the oxygen and the nutrients (ammonia, dynamic processes in seawater and air nitrate, nitrite and phosphate) at 3 days sea interaction. In first three day after sampling after the typhoon. typhoon, the drastic decrease in DO is Chlorophyll levels were also high. followed by increased concentration of The dissolved oxygen concentrations chlorophyll-a show the representative were found to be extremely low at both of phytoplankton abundance and the surface and bottom profiles at the organic matter in seawater. Kress et al. coastal areas but had extended to a (2002) reported that when oxygen

Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] distance as far as 5km away from the required for oxidation of organic matter shoreline for surface profile and 6km exceeds the oxygen produced by away from the shoreline for bottom photosynthesis, the dissolve oxygen profile. This is a reflection that the level in the water might ultimately entire coastal areas to as far as 5-6km decrease. Then, the increase of DO after from shoreline were experiencing low the 11- day typhoon could contribute by dissolved oxygen at 3 days after the fish reduction of chlorophyll-a and nutrient Journal of Survey in Fisheries Sciences 7(2) 2021 243

rich water. It may have an impact in The results for ammonia throughout the improving primary productivity, samplings (3 days, 11 days and 26 days resulting in increased oxygen after the fish kill incident) seemed to be production. Another reason that different from other nutrients. The increases DO return to normal is the extremely high concentrations of effect of lowering water temperature ammonia were recorded on the that increases oxygen solubility in sampling 26 days after the fish kill water. incident, and the source seemed to be The pH had been detected at a lower from the farthest from the shoreline. range at the shoreline for both surface This is very interesting fact, as the and bottom profiles, especially during ammonia concentration increased after the sampling of 3 days after the fish kill day 26 of typhoon. Further incident. The pH levels has shown signs investigation is needed in order to find of recovering on the sampling at 11 the cause of this. The effects of rising days after the fish kill incident and ammonia levels in seawater actually do returned to normal condition after then. not act in isolation; many other factors It was found that the source of pH contribute such as increasing human reduction was land-based. The drop in pressure, including climate change (e.g. pH during early typhoon may be caused temperature, rising carbon dioxide, by current induced strong winds that hypoxia etc.). Ammonia’s aquatic could carry open sea oceanic water with toxicity is principally due to the

high salinity into coastal areas and lead unionised form (NH3) (Wurts, 2003). to increased salinity coastal waters. The As pH increases, the toxicity of heavy rainfall and associated run-off, ammonia increases because the relative however, could balance the changes and proportion of unionised ammonia decrease the salinity, also leading to increases. The toxic level of ammonia decrease in seawater pH (Li et al., to fish is both pH and temperature 2009). Moreover, as the associated dependent (Stuart, 2010). Toxicity chemoautotrophic nitrification process increases as pH increases and as started, the process uses oxygen and temperature increases. Ammonia levels releases hydrogen ions that can cause in excess of the recommended limits pH and DO to fall. Seawater pH may harm aquatic life. normalization is alongside DO. After The other three nutrients measured 11-days of typhoon it seems to have i.e. nitrate and nitrite, were found to be Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] positive impact on pH and DO. In an exceeded the permissible levels of the environment with low organic matter recommended limits of MMWQCS and low respiration levels, any standard for Class 2 water quality (for hydrogen ions released may be aquaculture and recreation), in the absorbed by the alkalinity of results of the sampling on 3 days after surrounding seawater and resulted in the fish kill incident. However, the increased pH (O’Boyle et al., 2013). concentrations of these parameters 244 Aileen Tan et al., Causes of fish kills in Penang, Malaysia in year 2019, in conjunction to … seemed too reduced and returned to was approaching normal range of permissible levels on the 11 days and 100,000 cells/L. This could be due to an 26 days samplings after the fish kills overestimation of chlorophyll, which incident. The results also showed that was caused by high turbidity (Katlane the source of nitrate was land-based et al., 2012). On 21 August 2019, because a higher concentration of chlorophyll a concentration was high nitrate was recorded nearest to the especially in river mouth and fish farm. shoreline. This was in accordance with Phosphate concentrations are abnormally high total phytoplankton extremely high during the sampling on density of 1,563,896 cells/L in surface the 11 day after the fish kill incident and bottom water column compared to comparatively to 3 days and 26 days 13 August 2019. High presence of after the fish kill incident. This finding phytoplankton might cause less result was similar to Wang et al. penetration of sunlight to the seawater (2016); they claimed this incident and eventually may lead to reduced happened due to the role of vertical dissolved oxygen for the other marine mixing resulting from the strong wind organism. In other words, this might effect. As the wind subsided, the run- inadvertently result in fish kill event as off and open oceanic water intrusion in 13 August 2019. The condition was became more important for changing further deteriorated by low pH making the physical and chemical parameter. the fishes more vulnerable than what The rise in phosphate at 11-days after they were used to. Some typhoon also has greatly caused the phytoplanktons were able to adapt to growth of phytoplankton in seawater changes in pH, this mean only the (Fig. 9). phytoplankton composition would shift Phytoplankton composition showed towards more their favourable that the majority of the phytoplankton conditions. During the Typhoon found in the samples was not harmful Lekima, there might be a small scale species but they might have indirect nutrient upwelling in which nutrient association to fish mortality. being brought up to the surface Phytoplankton has the role and seawater and this would promote importance in ecological function as a phytoplankton growth. High nutrient primary producer that directly and concentrations were indicative of high indirectly fuels the food chain phytoplankton productivity, with Downloaded from sifisheriessciences.com at 22:35 +0330 on Thursday September 30th 2021 [ DOI: 10.18331/SFS2021.7.2.20 ] (Domingues et al., 2008). They have conditions conducive to diatom blooms important impacts on water quality by (Roberts et al., 2019). On 13 August affecting turbidity and concentration of 2019 after 3 days of typhoon generally dissolved oxygen and play other major there was high nutrient and suitable for roles in many ecosystem processes. On certain phytoplankton such as 13 August 2019, although chlorophyll a Coscinodiscus sp. coupled with other was high, the phytoplankton density environmental factors and later on shift Journal of Survey in Fisheries Sciences 7(2) 2021 245

towards Chaetoceros sp. on 21 August Acknowledgement 2019 which was abnormally high in cell We are grateful to Penang State density in particular phosphate was Government especially to YB Phee relatively higher than on 13 August Boon Poh, Chairman of State Welfare, 2019. This suggests different species Caring Society and Environment had different preference on the growth Committee for the support of this conditions. activity which was supported The storm and strong water current financially under project account 304 that had been caused by the Typhoon /PPANTAI /650913 /Y113. We also Lekima had churned up the sediments would like to thank Department of and nutrients at the seafloor, thus Fisheries (Penang) and Department of leading to the drastic changes and Environment (Penang) for collaboration degradation of the water quality support and CEMACS staff for helping surrounding the coastal areas of in all the sampling activities. Penang. 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