Plankton's Demise: Unraveling The Mystery Of Noise Pollution

Plankton, a vital species for marine ecosystems, is under threat from noise pollution. From jet-skis to explosions, sonar to shipping, human activity is causing a deafening crisis for marine life. While the impact of sound on our oceans is not as obvious as plastic waste or coral bleaching, it is having a devastating impact on plankton, the base of the marine food chain. This introduction will explore the causes and consequences of noise pollution on plankton and consider potential solutions to this growing problem.

Seismic airgun blasts

Seismic airguns are used to examine the layers of the seafloor to study Earth's history or locate oil and gas deposits. They do so by rapidly releasing compressed air, creating a bubble that produces a loud sound that travels through the water to the ocean floor. These sounds can travel underwater up to 2,500 miles and are repeated as often as every 10 seconds or every 15 seconds for days, weeks, or months at a time.

Zooplankton is vital nutrition for whales and numerous invertebrates like oysters and shrimp. Studies have shown that a large part of the zooplankton population was killed within a radius of 1.2 kilometres by the use of a single airgun. This is particularly concerning as hydrocarbon exploration in the seabed employs 18 to 48 airguns simultaneously.

The use of seismic airguns can also reduce catch rates for fish and disrupt essential behaviours in marine mammals, such as dolphins and whales. For marine animals, sound plays an essential role in feeding, mating, communicating, and avoiding predators. For example, humpback whales deviated from their predicted heading and decreased their swim speeds when exposed to seismic airgun noise. Atlantic spotted dolphins showed a significant, short-term avoidance response to airguns within approximately 1 km of the source.

Underwater explosions

Noise pollution in the ocean is extremely damaging to marine wildlife, as most marine animals depend on sound for survival. Visibility is often low underwater, so sound has evolved as an important sensory signal for marine wildlife, particularly for marine mammals such as whales, dolphins, and porpoises. They rely on sound to communicate, locate mates and prey, avoid predators, navigate, and even defend their territories.

In addition to sonar, commercially produced explosive deterrents, known as "seal bombs," are used in Southern California to protect fishing gear and catch from pinniped predation. These explosives contribute to the increasing level of underwater noise.

The search for oil and gas in the seabed involves the use of seismic airguns, which are among the loudest sources of noise blasts. Airguns can emit noise of up to 260 decibels every 10 to 15 seconds and can penetrate thousands of meters of water and dozens to hundreds of kilometers of the seabed. A single airgun can kill a large part of zooplankton, the basis of the marine food web, within a radius of 1.2 kilometers.

To protect marine life from the harmful effects of underwater explosions and noise pollution, measures such as reducing the speed of vessels and limiting the number and intensity of seismic blasts have been proposed.

Hydrocarbon exploration

The search for hydrocarbons has led companies to explore locations that were previously considered too close to residential and commercial areas. While exploration companies try to accommodate affected landowners, noise pollution has proven to be a challenging issue.

The process of hydrocarbon exploration involves three main activities. Firstly, the collection of scientific data to determine the presence of sufficient hydrocarbons underground. Most of the geologic work is done remotely on computers, but seismic testing is done onsite and involves heavy equipment and specialized vehicles. This phase is relatively quick and quiet. The second phase involves selecting the well location and preparing access roads and a drilling site. The drilling rig and its equipment are then moved to the site, and the drilling process begins. This stage can last for several weeks or months, running 24 hours a day, and generates substantial noise. If the well discovers commercial quantities of hydrocarbons, the third phase begins, where the rig is replaced with production equipment for extraction.

The noise generated during the drilling phase can be addressed through the use of temporary or portable noise screens. Additionally, manufacturers have invested in designing quieter equipment and ancillary products for noise reduction, such as high-performance muffler systems and acoustic baffling. Despite these efforts, the noise levels from some equipment remain dangerously high, exceeding 115 dBA, and pose challenges due to their outdoor location and large physical size.

Boat noise

Marine animals, including plankton, rely on sound for vital functions such as mating, finding prey, and avoiding predators. However, human activities are increasingly contributing to noise pollution in the ocean, making it harder for many species to survive. One of the main sources of this noise pollution is boats.

The use of seismic airguns, which are towed by boats, has been linked to reduced catch rates for cod and haddock, with corresponding negative socioeconomic impacts on local fishermen. In addition, boat noise has been shown to affect the behaviour of fish, causing them to become disoriented and potentially impacting their migration accuracy. This can have knock-on effects on the entire marine ecosystem, as plankton are a crucial food source for many species.

Furthermore, boat noise has been found to impair the risk assessment abilities of some fish species, likely affecting their survival. For example, damselfish failed to respond appropriately to alarm odours in the presence of boat noise, making them more vulnerable to predators. Additionally, embryo development in sea hares, a slug-like marine invertebrate, was impaired by boat noise, leading to increased larval mortality.

Overall, boat noise is a significant contributor to the growing problem of ocean noise pollution, which has far-reaching consequences for marine life, including plankton. Reducing boat noise and finding alternative methods to oil and gas exploration could help mitigate these impacts and improve the health of marine ecosystems.

Ocean shipping

Ocean noise pollution is a growing concern for marine life, and shipping is a major contributor to this issue. The noise from ships can cause significant harm to a wide range of marine wildlife, from plankton to whales.

Plankton, the base of the marine food chain, is vital for the nutrition of whales and numerous invertebrates. Ocean noise pollution can interfere with the ability of plankton to perform photosynthesis and produce oxygen, thereby worsening the climate crisis. Seismic airgun blasts, used by oil and gas companies to find reserves on the ocean floor, have been shown to kill large amounts of plankton within a 1.2-kilometre radius.

The noise from ocean shipping can also cause behavioural changes in marine life, including whales, fish, and lobsters. These animals rely on sound to communicate with one another, find food, reproduce, and navigate. When ship noise overwhelms these natural sounds, they may leave their preferred habitats or change important behaviours such as singing to mates or foraging for food. For example, noise from ferries has caused tuna schools to become uncoordinated, potentially affecting their migration accuracy.

In addition to behavioural changes, ocean shipping noise can also cause physical harm to marine life. Studies have shown that noise from boats can impair the risk assessment abilities of fish, likely impacting their survival. It can also cause elevated stress levels in marine mammals, reducing their resilience to other challenges such as water pollution and climate change.

To address the issue of ocean shipping noise, scientists and organisations have proposed various solutions. These include design changes to propellers and hulls, engine placement modifications, and reducing ship speeds. The International Maritime Organization (IMO) has established guidelines for reducing underwater radiated noise from shipping, which include strategies for noise reduction in design, construction, modification, and operation. Implementing these guidelines and solutions is crucial to mitigate the adverse impacts of ocean shipping noise on marine life.

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