Assessment of Ennore Oil Spill 2017 on Chennai Coastal Water and Biota

In the wee hours of 28 January 2017, the BW Maple (a liquefied petroleum tanker) collided with another Tanker (MT Dawn Kanchipuram) in the coastal waters off Kamaraj Port, Ennore resulting in an estimated 196 MT of bunker fuel (Grade 6) resulting in an oil spill. On the next day, large patches of oil were observed on the rocky shores approximately 13 km south of the Port. Sentinel satellite images displayed the movement and spread of oil slicks along the coast. Reconnaissance surveys were conducted to assess the implication of oil spills by analyzing various physicochemical and biological parameters at 72 locations comprising of 34 shores and 38 offshore stations. Total petroleum hydrocarbon (TPH) at Kasikoilkuppam was recorded from 1560 μg/l on 30th Jan to a maximum concentration of 5573 μg/l on 8th February 2017. Though the TPH was initially high, the value returned to normalcy in the subsequent months. The variation between air temperature (AT) and sea surface temperatures (SST) was almost about 5˚ C observed off Tiruchanakuppam (TRK-O), where oil had accumulated. Chl-a concentration was higher during pre-than-post-spill. Chl-a value has substantially reduced in all the coastal stations indicating the impact of oil on biomass. On average, there was a slight decline of 1 mg/L in dissolved oxygen (DO) level during the oil spill event. Phytoplankton, zooplankton, and macrofaunal composition did not indicate any major changes, however, the spatial variations attributed to the local variability. A few cases of mullets and anchovies fish mortality were reported. Though the fish catch remained unaffected, however, a sharp decline in sales was noted due to the notion that the fishes were contaminated with oil. Remarkably, the results obtained during the survey benefitted in assessing the impact on the environment as well as resolving appropriate compensation for different stakeholders.