While it is not surprising, it is a bit alarming that scientific evidence is revealing that the impacts of chronic ocean noise on marine life that are broader and deeper than what has heretofore been considered. Some of these revelations come out of evaluating impacts through more inclusive metrics. They also come from looking at ecosystem and habitat compromise, not just physiological and behavioral impacts on individual animals and species.
Noises from boats and ships are the most chronic around the globe, because any human activity taking place in the ocean will be accompanied by boats and ships – and a huge amount of that activity includes commercial shipping.
Shipping noise has historically been considered a “low frequency” noise. In the distant range this is the case; low frequency ship sounds can travel a hundred miles, so when we hear (or record) ships this is mostly what we hear. But in close range cavitating propellers and hull friction also generate a lot of high frequency noise which can interfere with the hunting and communication vocalizations of orcas and dolphins that utilize higher frequencies for close-range bio-sonar and group cohesion.
The orca work in this case was done in Puget Sound by Scott and Val Veirs of Beam Reach Research. This revelation is sure to have some consequences for the ecotourism industry that relies on boats to gain access to pods of whales and other marine life.
There is also mounting evidence that chronic noise is having ecosystem impacts with unknown, but likely deleterious effects. One study by Martin Solan (et.al.) looked at how shipping and windfarm noise disrupted marine invertebrate’s fitness for “fluffing up” the seabed – termed “bioirregation” which is crucial in nutrient recycling and carbon storage of the seafloor sediments.
Mounting evidence also indicates chronic noise from boats can disrupt predator/prey relationships in fishes and eels as well as various marine invertebrates. These understandings are developing from a broader assessment of ecosystems rather than just examining impacts on individual animals.
Given the complexity of the marine web of life – and all of the dynamic acoustical changes occurring in the sea, it is becoming increasingly difficult to pinpoint any particular consequences of any specific noise. We can just assume that any noise we introduce into marine habitats will drive biological changes.