The rapid expansion in the renewable energy industry has led to a significant growth in marine development activity. Piling associated with wind farm development has increased significantly over recent years and this is set to continue for the next decade. Further development of tidal energy is also expected as the technology for tidal turbines advances. Noise from piling and blasting are both transient and impulsive in nature and source levels are extremely high. In the immediate vicinity of the activity lethal injury can be expected with non-lethal physical injury and behavioural changes expected as the distance from the source increases.
The offshore oil and gas industry is well established however advances in technology have meant that fields may now be exploited that were previously considered uneconomical. Seismic surveys remain the primary method used for assessing the geology below the sea bed and this is likely to continue in support of oil exploration as well as to inform engineering decisions for renewables development.
It is well understood that SONAR from military sources can have an impact on marine life and there have been well documented cases of marine mammals beaching as a result of the use of SONAR during military exercises. However, whilst military SONAR is generally very high power, its use is relatively small when compared to other sources. Recent years have seen the cost of marine electronics fall to the point that all but the smallest fishing and leisure vessels are now equipped with SONAR depth sounders and fish finders. In regions with a high concentration of fishing ground or popular with leisure vessels it is reasonable to expect SONAR to be a significant contributor to underwater noise levels.
Shipping and Harbour Development
The number of vessels in the global shipping fleet increased by 27% between 2005 and 2010 and over the same period the total tonnage increased by 55% highlighting not only the increase in total traffic but also the trend towards larger vessels. Noise from shipping tends to be continuous and transitory in nature and relatively low level. It has generally been assumed that any noise from shipping does not significantly affect marine life. However the trend towards larger vessels does have an impact in other areas as dredging and other development activity has increased as ports adapt their capacity to accommodate larger vessels.
Vibration of any sort, when in contact with the sea will transmit noise into the marine environment. Offshore installations, once operational, will generate continuous persistent noise in the surrounding sea. Typical levels from wind turbines or oil platforms are usually sufficiently low as to be negligible when compared with natural sources such as breaking waves or rain. However, it is now becoming apparent that the cumulative impact of all sources of anthropogenic noise needs more detailed consideration.