Marine Life: Surviving Polluted Waters

Marine life is severely affected by polluted water. The oceans are the endpoint for much of the pollution we produce on land, and the types of pollution that humans generate are vast. From dangerous carbon emissions and choking plastic to leaking oil and constant noise, marine life is suffering. Water pollution can cause physical harm to fish and other aquatic organisms, such as gill damage, fin and tail rot, and reproductive problems. It can also reduce oxygen levels, creating 'dead zones' where fish and other marine life suffocate. Additionally, pollution can destroy marine habitats and food sources, such as coral reefs, and spread diseases that harm invertebrates, including shellfish. Plastic pollution is a significant concern, with plastic debris entangling, suffocating, and being ingested by marine animals. Water pollution also has knock-on effects on the food chain, impacting birds, bears, big cats, and wolves that rely on fish as a food source.

Plastic pollution

One of the most prominent issues caused by plastic pollution is entanglement. Marine animals, such as dolphins, seals, turtles, and birds, often find themselves entangled in plastic debris like fishing nets, six-pack rings, and plastic bags. This can lead to severe injuries, lacerations, and even death. The size of the plastic plays a crucial role, as smaller pieces, known as microplastics, can be ingested by marine organisms, causing internal injuries and death. These microplastics are often consumed by filter-feeding animals like whales or manta rays, leading to a decrease in their food supply and potentially affecting their reproductive capacity.

In addition to entanglement and ingestion, plastic pollution also contributes to chemical toxicity in the marine environment. Plastics contain various additives and pollutants that can leach into the water. When ingested or absorbed by marine animals, these chemicals can disrupt their endocrine systems, impair their reproductive health, and cause long-term health issues. This, in turn, can lead to population decline and even the extinction of certain species.

The impact of plastic pollution on marine life is far-reaching and devastating. It leads to increased mortality rates, disrupts the food web, and alters the behaviour of marine animals. Addressing this issue and reducing plastic pollution are crucial steps in protecting marine life and preserving the health and integrity of our oceans.

Noise pollution

Marine animals are highly dependent on underwater sound. Visibility is often low underwater, but sound is transmitted extremely well through water. As a result, sound has evolved as an important sensory signal for marine wildlife, especially for marine mammals such as whales, dolphins, and porpoises. They rely on sound to communicate, locate mates and prey, avoid predators, navigate, and defend their territories.

However, noise pollution from ships, seismic surveys, explosions, construction, and sonar devices has turned the once peaceful ocean environment into a loud, chaotic place, threatening the natural soundscape. This type of pollution is often overlooked compared to others, but its impacts are now being documented across all types of marine ecosystems.

Underwater noise can interfere with the key life functions of marine mammals, causing a variety of negative effects such as temporary or permanent hearing loss, behavioural and physiological changes, masking of sounds, injury, and even death. Very loud sounds can cause panic, leading to decompression sickness and tissue damage from gas bubble lesions. It can also alter the behaviour of marine mammals, causing them to move away from the noise, adjust their activities to avoid noisy times, or increase their anti-predatory behaviour.

To reduce noise pollution in the marine environment, policies are needed to mitigate propeller noise from ships and the sounds of sonar equipment, seismic air guns, pile driving, and construction. Quieter technologies must also be developed to make it easier to reduce noise pollution and improve the ocean soundscape, potentially enabling the recovery of some marine life.

Oil spills

Firstly, ingestion occurs when animals swallow oil particles directly or consume prey items that have been exposed to oil. This can cause gastrointestinal irritation, ulcers, bleeding, diarrhoea, and digestive complications, impairing the ability of animals to digest and absorb food, ultimately leading to reduced health. For example, baleen whales can become incapacitated when oil clogs their filtering device, and in extreme cases, this can lead to starvation and death.

Secondly, absorption occurs when animals come into direct contact with oil. Exposure to oil can damage the liver and kidneys, cause anaemia, suppress the immune system, induce reproductive failure, and even kill animals. Fish and sea turtle embryos may grow more slowly than normal, leading to lower hatching rates and developmental impairments.

Thirdly, inhalation occurs when animals breathe in volatile organics released from oil or from "dispersants" applied by response teams to increase the rate of degradation of the oil in seawater. Inhalation of these harmful materials can cause respiratory inflammation, irritation, emphysema, or pneumonia in marine animals. Species such as manatees, dolphins, whales, and sea turtles are particularly susceptible to this risk as they come to the surface to breathe periodically.

In addition to these direct effects, oil spills can also have indirect effects on wildlife by causing changes in behaviour. Oil spills may lead to the relocation of home ranges as animals search for new sources of food, increases in the amount of time animals must spend foraging, and disruptions to natural life cycles.

The magnitude of harm caused by oil spills varies depending on factors such as the amount of exposure, the pathway of exposure, the age and reproductive state of the animal, and the type of synthetic chemicals used in the cleanup process. Overall, oil spills have devastating consequences for marine life, affecting both individual organisms and entire ecosystems.

Algal blooms

The impact of algal blooms on marine life is significant. They produce toxins that can be harmful to humans, fish, shellfish, marine mammals, and birds. These toxins can cause a range of health issues, including gastrointestinal illness, mortality in pets and wildlife, and even human death in extreme cases. Additionally, algal blooms can clog the gills of fish and abrade their tissues. The blooms can also indirectly impact aquatic animals by providing a food source for bacteria, which consume the dissolved oxygen in the water, further contributing to the creation of dead zones.

The occurrence of HABs is a growing concern worldwide, as human activities lead to warmer and more nutrient-rich coastal waters. These blooms can occur in fresh, marine, and brackish water bodies and are caused by various organisms, including toxic phytoplankton, cyanobacteria, benthic algae, and macroalgae. While not all algal species produce toxins, those that do can generate multiple kinds, and a single toxin can be produced by multiple species. For example, Anabaena, a type of cyanobacteria, can produce both neurotoxins and hepatotoxins.

The toxins produced by algal blooms can have a wide range of effects on marine life. Dinoflagellate toxins, for instance, are among the most potent biotoxins known and can cause paralytic shellfish poisoning, neurotoxic shellfish poisoning, diarrhetic shellfish poisoning, and ciguatera poisoning in fish. These poisonings can result in a variety of symptoms, including nausea, vomiting, diarrhea, disorientation, difficulty breathing, mouth numbness, slurred speech, and even death.

The study of HABs and their impacts is challenging due to the complex interplay between toxins, human health symptoms, and geographic distribution. However, it is crucial to understand these impacts to develop effective control methods and protect marine ecosystems and human health.

Chemical pollution

One of the main impacts of chemical pollution is the disruption of coral reefs. Excess nutrients from agricultural runoff and wastewater cause coral bleaching, decreased reproductivity, reduced skeletal integrity, and decreased biodiversity. Additionally, herbicides damage symbiotic algae in coral, affecting photosynthesis and contributing to bleaching. Metals and synthetic compounds, such as polychlorinated biphenyls (PCBs), have toxic effects on corals and fish, disrupting reproduction, feeding, and growth, reducing habitat options for other organisms, and increasing mortality rates.

Contaminants of Emerging Concern (CECs) are another concern in chemical pollution. These pollutants, including agricultural chemicals, runoff from cities, household products, and pharmaceuticals, are not regulated under current environmental laws. CECs accumulate in the tissues of marine life and can cause ecological and human health issues. Endocrine disruptors, a type of CEC, impair the reproductivity of fish and corals and contribute to aggressive tendencies.

The persistence of chemical pollutants in the environment poses a significant challenge. Many chemical pollutants are resistant to biodegradation and can increase in concentration as they move up the food web. This accumulation has detrimental effects on marine life, including marine mammals and apex predators such as sharks and orcas.

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