The first 3D seismic survey of the sea bed in Montenegro has ended. The ship “Polar Empress” carrying out the survey started from the harbour of Bar on the 16th November around 3pm and the survey lasted 33 days finishing on the 19th December in the early morning hours. You can check the statements of Montenegrin government officials welcoming the ship using standard phrases on “transparency, nature protection, process monitoring” etc. although neither the seismic survey nor the activities before were completely transparent.

According to the details in the “Environmental Impact Assessment Study for 3D Geophysical Survey in Offshore Montenegro – EIA” (Eni Montenegro BV, 2017, 341 pp) the seismic survey ship should be towing 24 airguns with total volume of 5085 cubic inch (83,3 liters) But, the specification of seismic equipment aboard Polar Empress, the seismic vessel used in the survey, indicate that it is equipped with 22 streamers and unknown number of Bolt long-life airguns with volume up to 10.000 cubic inch! That means that seismic ship used in Montenegro could use airguns of double volume producing much more noise than it was presented and used for modelling in the EIA. That effectively means that the EIA could be completely wrong in presenting the evaluated peak sound level (PSL) of 256 dB* as noise produced by the seismic equipment of the ship and could be completely wrong in presenting what could be the impact on the species and how far it would spread in the environment!

But, how loud is 256 dB*? Peak noise levels of Boeing 747-400 during take-off measured by UK Civil aviation agency is 100,7 dB. For humans, sound above 90 dB causes hearing damage after only two hours, while levels above 120 dB causes immediate pain. In dolphins, even lower peak levels can cause permanent damages to their hearing making them incapable to survive in the sea where they rely on their hearing to sense their environment. After traveling through thousands of meters of water, noise produced during seismic surveys is still loud enough to penetrate many kilometres deep into the sea floor. Seismic survey can raise background noise for about 20 dB in an area of more than 300,000 km2. So, imagine yourself living in the environment where every 10 seconds there is an explosion of several dozen airguns simultaneously, producing noise at least twice that produced by the largest airplane in the world during take-off!

What is even worse, sound travels several times faster in the water than in the air and can propagate over much longer distances. The sound propagation model that was developed in the Montenegrin EIA to assess the impact of noise generated with this seismic survey predicted that sound produced with the airguns will be heard in northern Adriatic with levels above 150 dB and all the way to northern Africa with levels of 80 dB. The authors concluded that temporary threshold shift (that is actually a temporary hearing loss) in Cetaceans will occur up to 50 km from source! That means that dolphins in Croatia are affected all the way to Dubrovnik and Mljet, in Albania all the way to Durres and Karavasta and in the large part of offshore southern Italy. The EIA also modeled that fish injury could occur in the radius of 60 m to 4 km from the source and sea turtle death is possible in radius of 20 m and 1,4 km! Still, the EIA was accepted and survey was carried out.

During the survey, the seismic ship “Polar Empress” covered over 6.600 km surveying, while within the licensed blocks it covered approximately 3.500 km! Looking at the map of planned survey effort from the EIA it is visible that seismic ship covered larger area than it has been planned to cover.

If we consider roughly that the airguns fired every 10 seconds, it would mean that some 285.000 explosions occurred during 33 days of seismic survey (if all airguns fired simultaneously, or almost 7 million if we consider each airgun)! At the closest point the ship was less than 4 km from the coast. No wonder divers were reporting incredible underwater noise and headaches after spending time in the sea. But, marine animals cannot report stress and injuries they suffered. Unfortunately, although prescribed as one of the conditions in the Strategic Environmental Assessment for Hydrocarbon Exploration and Production in Offshore Montenegro, the Montenegrin authorities have not requested from the developers of the EIA to provide the baseline status on marine mammals and sea turtles in the area that will be impacted by this survey, nor did they use the real data on the occurrence and distribution of species in Montenegrin and surrounding waters to evaluate the impact. Equally, as far as we know, no authority from neighboring countries issued any kind of reservation for this seismic survey. That is why we will not be able to assess the real damage this survey caused to the sensitive species and habitat of the southern Adriatic. But what is evident, generated noise in the sea has drastically affected the quality of lives of Cetaceans in particular and long-term injuries to their auditory system will reflect on the populations in many years to come.

Sadly, it seems that is not the end of suffering for Adriatic dolphins as other oil and gas concessioner – Energean – is planning the seismic survey in their near-shore blocks in the near future.

*Because sound travels differently in different media (gases, liquids and solids) the measured values use different common reference. All here listed dB values are referenced to 1µmPa/1m in water and 20µmPa/1m in air. As common reference is different for air and water, sound levels cannot be directly compared but are listed just to give you the sense of noise generated in the sea during seismic surveys. As a very raw method to convert sound levels you can simply subtract the 62 dB from the sound levels in water to get the comparable level in the air. That would mean that 256 dB in the sea roughly equals 194 dB in the air.