Assessment on environmental status and consideration for the impact of cage aquaculture on sediment quality in Vung Ro bay, Phu Yen province.

The results of investigated and analyzed sediment samples were collected during May, 2014 in Vung Ro bay showed that the distribution of particles sizes in the sediment samples had almost type of muddy and muddy – clay sediments (the average particle sizes ranged from 0.063 - 0.004 mm, with the proportion > 40%). Content of TOM in surface sediments slightly changed among areas) with the average value of 71.04 ± 7.52 mg/g (ranged from 52.92 to 75.56 mg/g). The profile distribution of TOM, TOC and total P contents in the depth of the sediment cores at inside and outside of farming areas were not highly fluctuated among sediment layers. The differences of the total N content in sediment layers showed that there was the gradually increasing trend from the lower sediment layers upwards (higher from 6 cm to 0 cm depths) in both of sediment cores. Heavy metal contents slightly ranged among the investigated points and were relatively low: Cu ranged from 6.19 to 7.90 mg/kg; Pb ranged from 22.53 to 25.76 mg/kg; Zn ranged from 41.48 to 59.58 mg/kg; Cd ranged from 0.14 to 0.31 mg/kg and As ranged from 2.80 to 8.10 mg/kg. The results of petroleum hydrocarbon also showed very low content with the average value was 4.4 ± 1.7mg/kg. Total Vibrio spp. showed high density in most points, and average value was 132,249 ± 69,948 cfu/100g. The contents of heavy metals in the bay did not exceed the critical values in QCVN 43: 2012/BTNMT.