Fig. 3 Temporal check details variation in water temperature, electrical conductivity (EC), salinity, dissolved
oxygen (DO), pH and redox potential (Eh) at a site 1, b site 2-2 and c site 3 DO and pH ranged from 4.5 to 7.2 and from 8.1 to 8.3 at site 1, respectively. Site 2-2 and site 3 in particular displayed more variation. DO and pH decreased during the night and increased during the day. These variations are likely in response to respiration and photosynthesis by photosynthetic microorganisms. Surprisingly, negative Eh values were found at sites 2-2 and 3, whilst site 1 showed positive values during the entire observational period. Site 2-2 displayed quite a different trend to that of site 3. The minimum Eh click here value of −61 mV appeared at midnight at site 2-2, although
the trend of variation in Eh was quite similar to those in DO and pH at site 3. From the results, there is a possibility that wastewater flows into the coastal area at site 2-2. Sediment microbial community structure Plastoquinone with nine isoprene units (PQ-9) and VK1 were detected at 0.25 and 0.14 μmol/kg in total at sites 2-2 and 3, respectively, but 0.04 μmol/kg at site 1 (Table 1). The contents at sites 2-1 and 2-3 were also similar to or greater than that at site 3, indicating the presence of sufficient nutrients at these sites to maintain a higher abundance of photosynthetic microorganisms. Table 1 Content of photosynthetic quinones, plastoquinone (PQ) and vitamin K1 (VK1), in coastal sediments at each site Site PQ-9 VK1 (μmol/kg) Liver X Receptor agonist Total 1 0.03 0.01 0.04 2-1 0.17 0.01 0.18 2-2 0.22 0.03 0.25 2-3 0.13 0.01 0.14 2-4 0.07 0.01 0.08 3 0.09 0.05 0.14 At site 1, the respiratory quinone content
in the sediment sample was 0.04 μmol/kg, composed of ubiquinone and menaquinone mafosfamide (Fig. 4). On the other hand, the quinone content at sites 2-1, 2-2, 2-3 and 2-4 ranged from 0.14 to 0.54 μmol/kg and that at site 3 was 0.27 μmol/kg. The sediments near the populated areas had a microbial biomass 2.7–10.4 times that of the unpolluted area sediment. The higher microbial biomass suggests that the organic matter and nutrients used for their growth in sediment are supplied to the four sites, particularly site 2-2, by the coastal communities. Fig. 4 Content of respiratory quinones, ubiquinone (Q) and menaquinone (MK), in coastal sediments at each site At site 1, the most predominant quinone species was ubiquinone with eight isoprene units (Q-8), followed by menaquinone with six isoprene units (MK-6) and MK-8. The order of occurrence of the units at sites 2-1, 2-2, 2-3 and 2-4 was Q-8 > Q-9 or Q-10 or MK-7 > Q-9 or MK-7 or MK-8 and that at site 3 was Q-8 > Q-10 > MK-7.