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Port Dickson Surface Water Quality Status: A Year with COVID-19 Pandemic

The COVID-19 pandemic has become a planetary concern that affecting the sustenance of the human population all around the globe. The effective measured has been taken in Malaysia to control the virus transmission by limiting the human vitality which unsurprisingly propitious to the environment. A monitoring study was conducted to assess the water quality status of surface seawater along the Port Dickson coast based on the Malaysian Marine Water Quality Index (MMWQI) and Malaysian Marine Water Quality Standards (MMWQCS) with an interval period of a year (March 2020-March 2021). In situ, water quality parameters incorporate temperature, pH, salinity, conductivity, dissolved oxygen (DO), and total dissolved solids (TDS) were measured at 14 sampling sites to evaluate the biochemical characteristics of water. Surface water samples were collected from the same sites and transported back to Universiti Putra Malaysia for nitrate (NO3-), ammonia (NH3), phosphate (PO4), biochemical oxygen demands (BOD), fecal coliform (Escherichia coli), and total suspended solids (TSS) analyses. The MMWQI showed the status of surface water from the Port Dickson coast was classified as moderate quality (50.41 - 64.05) for both sampling events. However, there are some indexes that showed significant decreases (p< 0.05) in the latter year. The concentration of nutrient pollution such as phosphate, nitrates, ammonia, fecal coliform as well as oil and grease, was decreased by 11.12%, 77.39%, 82.4%, 90.26%, and 99.9% respectively. The water parameters namely TDS, pH, and BOD levels were significantly decreased by 1.77%, 20.73%, and 77.16%. Certain parameters listed in the MMWQS such as temperature, pH, ammonia, fecal coliform, oil and grease were classified as Class 1 in March 2021. These occurrences recorded were greatly influenced by the reduction of the substantial human activities around the recreational beach of Port Dickson followed by the declaration of Movement Control Order (MCO) in Malaysia.


Sampling Methods and Analytical Procedures
Water sampling has been carried out twice before the COVID-19 pandemic MCO in March 2020 and a year after the MCO in March 2021. The water samples were collected from each station with 50 cm of the surface seawater depth from one kilometer from the coastal beach. The water samples were collected in the specific bottles according to the samples using Van Dorn water sampler. Samples were stored in 500 ml acid-washed plastic bottles for nutrients analysis, amber glass for biochemical oxygen demand (BOD) analysis and 50 ml sterile centrifuged tube for fecal coliform analysis. The collected water samples were stored cooled, transported to the laboratory in Universiti Putra Malaysia and processed within 24 hours.
The in-situ water was measured including temperature, dissolved oxygen (DO), conductivity, pH and salinity using YSI meter, while BOD 5 , TSS, PO 4 , NO 3 , NH 3 -N, and fecal coliform (FC) were analysed in the laboratory. BOD 5 was analysed as described by 5-day test and TSS analysis was used total solid dried method [14]. Moreover, phosphate, nitrate, and ammonia nitrogen were assayed by acid ascorbic, cadmium reduction, and Nessler methods, respectively using Hach DR900 colorimeter. While, the fecal coliform specifically Escherichia coli was identified using Colilert 18 Test. The oil and greases method were using hexane extractable gravimetric method which also known as USEPA Method 10056. The equipment's were calibrated prior to use based on the manufacturer's instruction.

Statistical Analysis
Statistical analysis of the data was carried out using SPSS version 22. The analysis of the variance (ANOVA) was carried out to determine the significant differences between sampling stations.  [16]; [17] ( Table  2). The surface water temperature was greatly influenced by the weather, the sampling time and location [18].

pH
The pH values showed significant differences (p<0.05) between the two sampling occasion which higher in March 2020 before MCO with average of 8.65 than a year after which is much lower with the averaged value of 6.86 (Table 3) The pH values decrease significantly as due to MCO, the domestic discharge and sewage effluent may eventually load into the aquatic ecosystem as well as the invisible pollutants sources that have been build up through bioaccumulation and biomagnification in the environment (Chuan et al., 2021). Another study by [24] concluded that the pH can becomes lower in the coastal area as the mangrove soils experienced decaying of the vegetation and acidification of the clays [25]. Generally, the decreases in the pH as a result of the ocean acidification from the absorption of the anthropogenic greenhouse gases and CO 2 by the ocean. However, overall, the range of pH from 6.5 to 9 is considered appropriate for aquatic organisms. Therefore, it is crucial to maintain the balance pH for the aquatic ecosystem as extreme pH changes can be detrimental.

Salinity
The salinity of the both sampling occasions were averaged of 31.33 ppt and 30.54 ppt in March 2020 and March 2021 respectively. There are no significant varied (p>0.05) between sampling stations in both sampling occasions. The salinity around the coastlines area were in lines with the previous report ranged from 28.0 ppt -31.00 ppt ( [20]; [21]; [17] greatly influenced the salinity in the Port Dickson coastlines. The salinity of the coastal water could be influenced by the heavy rainfall causing the large freshwater inflow into the sea. The ocean salinity is playing important roles in the world climate and its aquatic organism as well as the its habitability [26].

Dissolved Oxygen
The maximum dissolved oxygen recorded was in station 2 in March 2020 with averaged reading of 9.29 mg/L, while the other sampling stations recorded the mean value of 7.80 mg/L before the MCO. However, the dissolved oxygen in the coastal surface water of Port Dickson has significant decreases (p<0.05) after a year with COVID-19 with average of 5.51 mg/L. According to the [12], these occasions may result from the urban runoff of the greywater as the product of greywater increased since the stay-at-home policy were implemented. The greywater domestic discharged were usually carried along the dissolved nutrient into the aquatic ecosystem through the stream that can caused the low dissolved oxygen in the coastal surface water of Port Dickson. Also, the lowered dissolved oxygen may due to the high decomposition of the organic matters in the coastal mangrove areas which also impacted the lowered pH values in this study. Despite the lower dissolved oxygen after a year with COVID-19, the results are within the standard acceptable levels of MMWQCS for Malaysian marine ecosystem which classified in Class II. The saturation level of dissolved oxygen >5.00 mg/L is important for the growth of the marine fish and plankton as well for other aquatic organisms [27]. Previous study conducted by [17] also reported the similar ranged dissolved oxygen from 5.42-6.66 mg/L.

Biochemical Oxygen Demand
The biochemical oxygen demand (BOD 5 ) of the coastal surface water was ranging from 3.99 to 6.33 mg/L in March 2020, before the MCO and showed significant decreases of 77.16% of the BOD in March 2021. The value of the BOD was averaged of 1.12 mg/L after a year of movement control order. This study showed that the regular influx of anthropogenic sources causing the BOD higher event though the dissolved oxygen in the surface water is highly concentrated before the MCO regulations. After a year with MCO, the BOD decreases significantly showed that the limited human activities give a positive impact towards the aquatic environments. According to [23], the average BOD in the surface water of the Straits of Malacca was 0.604 4±0.077 mg/L, however he reported that the Port Dickson areas are susceptible to higher BOD. The BOD values might increase as the economic and tourism activities can be carried out after the movement control order lifted. Therefore, in order to maintain the good water quality of the Port Dickson coastlines, a good plan of environmental management program should be conducted by the authorities and supported by the local communities.

Total Suspended Solids
The coastal surface water of Port Dickson recorded high TSS in March 2020 before the MCO and recorded higher TSS in March 2021 with mean ranged between 475.93 mg/L and 594.64 mg/L respectively. in addition, ANOVA result showed there is no significant difference (p>0.05) in TSS between the sampling stations. Based on the MMWQCS for Malaysia marine ecosystem, the TSS were classified in Class III of which the coastal water has directly exposed of the effluent discharged from the industry, commercial activities and coastal settlements. Port Dickson as an ecotourism site proved that high human activities around the coastlines area caused the high concentration of the suspended solids in the water body. Also, the rainy events happened before the sampling occasions could affect the suspended solids came along with the sediment's runoff from the terrestrial surrounding area. The high TSS also can be contributed by the high concentration of phytoplankton or the living microorganism as well as the non-living matters which suspended in the water body [28]. Besides, the strong ocean current during sampling occasions can affect the re-suspension of the sediments along the coastlines [29].

Total Dissolved Solids
The values of total dissolved solids (TDS) before MCO were recorded with average of 31.22 g/L and the value slightly decreases in March 2021 with average of 30.67 g/L. The values recorded between sampling stations did not show significant varied (p>0.05) between them. The TDS values showed the typical seawater dissolved solids in the water body ranged up to 35.0 g/L. The high concentration of dissolved solids was attributed by the immense anthropogenic activities and sedimentation runoff with high contents of suspended matters [24].

Electrical Conductivity
In this study, the electrical conductivity ranged between 46.64 -47.50 μs/cm in March 2020 and increases in March 2021 ranged between 51.03 -51.48 μs/cm. The conductivity in both sampling occasions showed there are no significant differences (p>0.05) between sampling stations. Overall, the conductivity of the seawater can be up to 50.00 μs/cm and affected by the inorganic dissolved solids such as sodium, magnesium, chloride, calcium and cations [30]. A part of inorganic dissolved solids, the organic compounds such as oil, and phenol can affect the water conductivity.

Nitrate
The nitrate (NO3) concentration ranged from 1.4 -3.5 mg/L in March 2020 and had significantly decreases (p<0.05) in March 2021 with ranged between 0.369 -0.776 mg/L. The highest concentration was recorded at station 8 in March 2020 which then decline to 0.46 mg/L with percentage of 86.86%. The nitrates values recorded at the both sampling stations in this study are within the permissible limit of Malaysia Marine Water Quality Criteria and Standards (MMWQCS) (>0.1 mg/L) which classified as a Class III. The overall percentages of decrease are up to 77.39 % showed that the less human activities around the area decreases the nutrient pollution released into the water body. Generally, the values recorded in this study were higher than the previous study ranged between 0.01-0.05 mg/L [17]. The high concentration of nitrates could be attributed by the runoff of various water sources such as agricultural fertilizer as well as the natural events such as atmospheric and geological depositions [31]. The concentrations of the micro-nutrients in the coastal water of Port Dickson and its classification have been summarized in Table 4.

Ammonia-Nitrogen
Unionized ammonia (NH3-N) concentrations of the coastal water samples ranged between not detected to 0.003 mg/L with averaged of 0.001 mg/L in March 2020. Few stations showed increases in the readings recorded up to 0.0003 mg/L in March 2021. Overall, in average the ammonia concentration showed a significant decrease (p<0.05) in March 2021 with percentages of 82.47% as compared from the March 2020 with ranged between 8x10 -6 -2.95x10 -4 mg/L. Based on the Malaysia Marine Water Quality Criteria and Standards, the concentration of unionized ammonia was within the permissible limit of Class I (0.0035 mg/L). Previous study showed higher concentration of ammonia in water body ranged between 0.12 -0.18 mg/L could be contributed by the sources of nutrients from inland discharged and freshwater runoff during rainy seasons [17]. The scale down in industrial and ecotourism activities due to COVID-19 pandemic positively impact the marine ecosystem along the Port Dickson coastlines from the overloading of the nutrient into the seawater that can eventually threaten the aquatic organisms.

Phosphate
The phosphate (PO 4 ) concentration was ranged between 0.10 -0.22 mg/L in March 2020 and decreases up to 11.12% a year after in 2021. The concentration was decreases to range between 0.003 -0.297 mg/L with averaged of 0.146 ± 0.01 mg/L. The phosphate concentrations were significantly varied (p<0.05) between the sampling stations in both sampling sessions. The highest phosphate concentration recorded in station 11 with concentration of 0.22 mg/L and decreases in March 2021 down to 0.07 mg/L with percentages of 68.18% decline. The phosphate values recorded at the both sampling stations in this study are within the permissible limit of Malaysia Marine Water Quality Criteria and Standards (0.075 mg/L) which classified as a Class II. As mentioned before, the decline in the nutrient concentrations may due to the restricted movement control order during this pandemic and this events directly leave positive impact towards the environment as many sectors including industrial and tourism were not allowed to be operated. Previous study along the coastlines of Port Dickson showed lower concentration of phosphate ranged from 0.06-0.09 mg/L proved that there are intensive population and economic growth around the Port Dickson area over the past years. Overall, the high concentration of phosphate recorded were greatly contributed by the run off of the domestic effluent from detergent, fertilizers as well as the waste-water from the industrial activities [32].

Fecal Coliform
The fecal coliform concentration especially E. coli in March 2020 before the strict standards operation procedures of MCO was ranged between 26.5 -203.0 MPN/100 mL while the concentration was recorded decreases significantly after a year in March 2021. The E. coli concentration decreases up to 90.26% to range within 1.0 -15.0 MPN/100 mL after a year with MCO. There are significant differences (p<0.05) in the mean concentration of the fecal coliform between the sampling stations in both sampling occasions. Stations 14 showed the highest E. coli concentration with 203 MPN/100 mL which later dropped to 11.1 MPN/100 mL after a year with MCO with 94.5% decreases recorded. The MMWQCS on fecal coliform parameters showed the increases in the water quality index as before MCO, there is one station with E. coli concentration higher than the standard in Class III (>200 MPN/100 mL) which then changed to Class I (<70 MPN/100 mL) after a year with strict movement order. The high concentration of the fecal coliform or E. coli along the sampling stations could be caused by the sewage discharged from the surrounding areas. According to [33], the increases of settlements in coastal population as well as the waste-water discharged of the treated and untreated sewage are the main factors contributing to the high number of fecal coliforms. In addition, along the Port Dickson beaches with hotels and houses, there are 82 pipelines that directly discharged the waste-water into the sea which negatively impact the surrounding water quality [34]. Table 5 showed the summary of the previous record of the fecal coliform study along the Port Dickson coastlines which shows the intense tourism activities and the growing population around the area. A year with strict order of any human activities during COVID-19 pandemic can clearly decreases the concentration of fecal coliform in the water body. The fecal coliform concentration might increase as the tourism activities can be operated as previously.

Marine Water Quality Index
Malaysia marine water quality index were calculated using seven crucial parameters to classify the marine water quality index into several categories from poor, moderate, good and excellent. There are many factors that contributed to the marine water quality index including the development and industrialization along the coastlines as well as the ecotourism activities as one of the main attractions. Previous record reported by the Malaysia Environmental Quality Report (2018), showed several areas with similar category of MWQI in moderate class around the area of Port Dickson city, Pantai Teluk Kemang, Port Dickson TNB, Port Dickson Batu 5, with reading of 68, 67, 68, 68 respectively. Maintaining the marine water quality are important in sustaining the aquatic ecosystem.

Conclusion
Water quality of the coastal area of Port Dickson based on several parameters showed positive improvement in the water quality a year after the movement control order in Malaysia. Strict movement control order (MCO) has been implemented in mid-March 2020 since the spread of the COVID-19 pandemic all over the world. Although this COVID-19 pandemic negatively impacts the global human health as well as the world economic sectors, we can see some positive impact towards the environmental pollution. The endless pollution from the anthropogenic activities is declining and natural environment in aquatic ecosystem are recovering by its own nature. Some positive impact reported in this study may be temporary and the pollution index may increase later after the economic and social activities are allowed back to be operated. Therefore, the effective aquatic managements of water quality assessment should be studied from this unfortunate event of COVID-19 to reduce the aquatic pollution for future to ensure the sustainability of the marine ecological functions and integrity.