Sinking marine oil snow was found to be a major mechanism in the transport of spilled oil from the surface to the deep sea following the Deepwater Horizon (DwH) oil spill. Marine snow formation is primarily facilitated by extracellular polymeric substances (EPS), which are mainly composed of proteins and carbohydrates secreted by microorganisms. While numerous bacteria have been identified to degrade oil, there is a paucity of knowledge on bacteria that produce EPS in response to oil and Corexit exposure in the northern Gulf of Mexico (nGoM). In this study, we isolated bacteria from surface water of the nGoM that grow on oil or Corexit dispersant. Among the 100 strains isolated, nine were identified to produce remarkable amounts of EPS. 16S rRNA gene analysis revealed that six isolates (strains C1, C5, W10, W11, W14, W20) belong to the genus Alteromonas; the others were related to Thalassospira (C8), Aestuariibacter (C12), and Escherichia (W13a). The isolates preferably degraded alkanes (17-77%), over polycyclic aromatic hydrocarbons (0.90-23%). The EPS production was determined in the presence of a water accommodated fraction (WAF) of oil, a chemical enhanced WAF (CEWAF), Corexit, and control. The highest production of visible aggregates was found in Corexit followed by CEWAF, WAF, and control; indicating that Corexit generally enhanced EPS production. The addition of WAF and Corexit did not affect the carbohydrate content, but significantly increased the protein content of the EPS. On the average, WAF and CEWAF treatments had nine to ten times more proteins, and Corexit had five times higher than the control. Our results reveal that Alteromonas and Thalassospira, among the commonly reported bacteria following the DwH spill, produce protein rich EPS that could have crucial roles in oil degradation and marine snow formation. This study highlights the link between EPS production and bacterial oil-degrading capacity that should not be overlooked during spilled oil clearance.
Rivers are essential sources of plastic litter in the marine environment. Recently, the Philippines was reported as the biggest polluter of plastic litter from riverine sources. However, the riverine plastic litter's origin has been less established. In this study, we determined the density, composition, and accumulation of plastic litter on the riversides of Pulot River and its tributary in Palawan Island, Philippines. We also identified the possible sources of plastic litter. Results showed that the plastic litter density was highest at the river edge during the first sampling period. Litter densities for the predefined zones and sampling periods all showed no significant differences. The most dominant plastic litter types were food packaging and plastic bags, followed by toiletries. ‘Others’ consisted of multilayers, mixed, and plastics accounted for the most abundant polymer types. We identified the residents in the vicinity illegally dumping litter, for there were small illegal dumping sites along the river. These results suggest the urgent need for better waste policy implementation measures to protect the riparian environments and reduce the input of riverine plastic litter into the marine environment to ensure river resource sustainability.
In early 2018, the recreational water of Bacuit Bay in El Nido, Palawan, Philippines was declared by the Department of Environment and Natural Resources (DENR) to be contaminated with a coliform count of 1,139 MPN 100 ml-1 sample water. Although water quality assessment was done in the area, no study was conducted on the associated clinically important bacterial pathogens. This study was conducted to assess the microbial contamination and presence of some pathogens, and to compare microbial contamination between 2018 and 2019 in Bacuit Bay. Surface water samples were collected from 11 stations in Bacuit Bay in June 2018 and June 2019. The multiple tube fermentation technique was done to assess the coliform contamination. Selective and differential microbial culture media were used to isolate some clinically important pathogens. Results showed that in 2018, all stations were positive with coliform where nine out of 11 stations exceeded the acceptable level of coliform count for recreational waters. Also, there were eight clinically important putative bacterial pathogens isolated, the Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Shigella sp., Salmonella sp., Vibrio parahaemolyticus and Vibrio cholerae. In 2019, the coliform count and the associated bacterial pathogens decreased in number with only two out of 11 stations exceeded the acceptable level and two of eight bacterial pathogens were detected. These could be attributed to the activities that were conducted by the local government unit of El Nido to mitigate the pollution in the coastal environment.
The brown seaweed Sargassum spp., locally known as “samò,” is subject to increasing overexploitation in the natural environment; thus, culturing the species for mass production is necessary. Understanding the required environmental factors is essential in the successful culture and mass production of this species. This study aims to determine the egg release and fertilization of Sargassum polycystum in response to the different environmental conditions that may influence its reproduction. Fertile thallus of S. polycystum was collected at Naawan, Misamis Oriental, Philippines in March 2018. Reproductive receptacles were excised and placed in Petri dishes and were exposed to varying environmental conditions under laboratory conditions. The experiments were conducted in triplicate Petri dishes per treatment. Percent (%) egg release and percent fertilization were observed for about 2 wk. Results showed that percent egg release and percent fertilization did not differ significantly across temperature ranges (20–30°C) and desiccation time (5–60 min). Receptacles treated with nutrients resulted in only ~ 45% egg release with a daily decrease of 10% towards the addition of AGP fertilizer. The highest % egg release (80%) was observed in the control treatment (no fertilizer). Percent egg release in receptacles subjected to 20–45 PSU showed no significant difference. This study suggests that the optimum condition for the release of eggs and subsequent fertilization can be achieved under ambient temperature, with no direct exposure to sunlight, no addition of fertilizer, and within the ambient salinity of 30–32 PSU.
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