Environmental Factors Influencing the Association of Vibrio Species and Phytoplankton in Northern Sarawak
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Universiti Malaysia Sarawak
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The genus Vibrio is commonly found in aquatic environments such as rivers, estuaries and coastal areas, where they thrive under favorable conditions like warm temperatures, moderate salinity and their attachment to planktonic organisms, for example, phytoplankton during algal bloom. Pathogenic strains such as Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus, pose significant health risks, leading to illnesses ranging from gastroenteritis to septicemia. Phytoplankton blooms create nutrient-rich conditions that enhance Vibrio growth and persistence in the aquatic ecosystems. The estuary in northern Sarawak offers an ideal environment for studying the interaction between Vibrio species and phytoplankton. Despite numerous reports of Vibrio-related outbreaks globally, limited studies have been conducted on the occurrence and association of Vibrio species with phytoplankton in this region. The aim of this study is to examine the relationship between environmental parameters and the occurrence of Vibrio species and phytoplankton in the estuarine of northern Sarawak. Water samples were collected from two estuaries, Coco Cabana, Miri and Kampung Limpaku Pinang, and environmental parameters were recorded in-situ at the study sites. Phytoplankton abundance was measured microscopically, while bacterial isolation was performed using selective media (TCBS agar). Molecular identification of Vibrio species was conducted using PCR amplification of species-specific genes (OmpW for V. cholerae and ToxR for V. parahaemolyticus). In this study, PCR analysis revealed that 36.7% (22/60) samples were tested positive for V. cholerae, as evidenced by the detection of OmpW gene (588 bp). The OmpW gene encodes an outer membrane protein that plays a crucial role in the structure integrity and environmental adaptability of V. cholerae. Furthermore, 31.7% (19/60) of the samples collected from both estuaries were positive for V. parahaemolyticus, confirmed by the presence of the ToxR gene iv (368 bp) that encodes the regulatory protein that governs the expression of virulence factors essential for the pathogenicity in aquatic environments and during human infection. Statistical analysis one-way ANOVA revealed significant correlation (p < 0.05) between Vibrio abundance, water temperature and salinity, but not pH. Pearson’s correlation analysis showed a negative relationship (r = -0.45 and -0.73) between the concentration of Vibrio species and phytoplankton in both sampling sites. This suggests that the increase in Vibrio species abundance heightens the competition for resources, resulting in a reduction in phytoplankton density. The analysis also revealed that phytoplankton was influenced by temperature and salinity. Elevated temperatures led to a decrease in phytoplankton count, indicating that high temperature can negatively affect their growth and abundance. Furthermore, the measured high salinity reduced phytoplankton abundance, possibly due to osmotic stress, thereby further influencing interactions with Vibrio species. This result will offer understandings to the potential public health risks posed by Vibrio species in estuarine ecosystems and contribute to the understanding of their ecological dynamics in estuarine environments in northern Sarawak, Malaysia.