coli results indicate that ebb tides enable domestic wastewater to flow through groundwater into the coastal waters. This is also supported by sediment analysis. Fig. 8 Quantification of Escherichia
coli at high tide and low tide in the reef-flat seawater at site 2-2 As shown in Fig. 9, relatively high numbers of E. coli were detected during the ebb tide on 7 August 2010 and 29 August 2011. However, the maximum number of E. coli during the ebb tide on 7 August 2010 was 2.5 × 104 MPN/100 mL, while it was 1.1 × 103 MPN/100 mL on 29 August 2011. The transition period from neap tide to spring tide would gradually increase the amount of sea water flowing into the septic tank from the bottom and the amount of domestic Fludarabine cost wastewater leaking and subsequently flowing into the coastal waters, due to the gradual LY3039478 increase in water-level difference between high tide and low tide. On the other hand, just after a spring tide, domestic wastewater inside the septic tanks would mostly have leaked out, because of the maximum water-level difference. Thus, high numbers of E. coli as observed on 7 August 2010 would not be found. These runoff mechanisms give the explanation of the differences in the numbers of E. coli on 7 August 2010 and 29 August 2011. Fig. 9 Temporal variation in E. coli in the reef-flat seawater on 7 August 2010 and 29 August 2011 at site 2-2 Surficial sediments at sites 2-1, 2-2, 2-3 and 2-4 were grey sand with a hydrogen sulfide
odour. AVS concentrations ranged from 0.024 to 0.133 mg/g. This corresponds to the sediment quinone analysis that detected MK-7, which occurs in sulfate-reducing bacteria. Digging in the sandy beach between the households and the coast revealed similar grey sand. However, no grey sand was found at the other sites and AVS concentrations were less than the detection limit (0.002 mg/g). Therefore, sulfate reduction occurs in sediments from sites 2-1, 2-2, 2-3 and 2-4. This further lends support to the hypothesis
that domestic wastewater runoff migrates to the coast through the groundwater. There is a strong possibility that the coastal water pollution in the lagoon due to poorly constructed sanitary facilities is connected Idoxuridine to the decrease in sand supply as observed in other atolls (Ebrahim 2000; Fujita et al. 2009; Hirshfield et al. 1968), because the coastal environments are chronically damaged. In other words, the results from this study demonstrate an urgent need for the development and implementation of effective water quality control strategies. To consider such strategies, we RG7112 research buy should pay attention to both hard and soft infrastructures. The former in order to improve the purification capability of existing sanitary facilities for wastewater treatment. Improved sanitary facilities should be suitable for the geophysical and social surroundings specific to atolls. The latter in order to establish a policy for the water quality improvement and to develop local capacity building.