6.5 Ocean Resources and Human Impacts

The oceans are a vital source of food, minerals, and energy for humans. From fish and shellfish to offshore oil and wind farms, we rely on these resources. But our use of the seas comes at a cost, impacting marine ecosystems through overfishing, pollution, and habitat destruction.

Climate change is also taking a toll on our oceans. Rising temperatures cause coral bleaching, while increased CO2 leads to acidification. These changes, along with sea level rise, threaten marine life and coastal communities. Sustainable management practices are crucial to protect our oceans for future generations.

Ocean Resources

Food Sources

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• The oceans provide a wide range of food resources, including fish (tuna, cod, salmon), shellfish (shrimp, crabs, oysters), and seaweed (kelp, nori), which are important sources of protein for many people around the world
• Aquaculture, the farming of aquatic organisms, is increasingly being used to supplement wild-caught seafood and meet growing global demand for fish and shellfish
• Seaweed is not only used as a food source but also has applications in the production of food additives (carrageenan, agar) and biofuels

Mineral Extraction

• Minerals such as salt, magnesium, and bromine are extracted from seawater through various processes, including solar evaporation and electrolysis
• Salt is the most commonly extracted mineral from seawater and is used for a variety of purposes, including food preservation, de-icing roads, and chemical production
• Magnesium and bromine are used in the production of various industrial and consumer products, such as fire retardants, pharmaceuticals, and batteries

Energy Resources

• Oil and natural gas are extracted from offshore reserves using drilling platforms and pipelines, providing a significant portion of the world's energy supply
• Offshore oil and gas production occurs in many regions around the world, including the Gulf of Mexico, the North Sea, and the Persian Gulf
• Renewable energy sources, such as offshore wind farms, tidal power, and wave energy, are increasingly being developed to harness the power of the oceans
• Offshore wind farms, such as the Hornsea Wind Farm in the United Kingdom, can generate significant amounts of electricity while reducing greenhouse gas emissions

Biotechnology and Pharmaceuticals

• Marine organisms, such as algae and bacteria, are being researched for their potential use in biotechnology and pharmaceutical applications
• Compounds derived from marine organisms have been used to develop drugs for treating cancer (bryostatin), pain (ziconotide), and viral infections (vidarabine)
• Marine microalgae, such as Spirulina and Chlorella, are used as dietary supplements and have potential applications in biofuel production and wastewater treatment

Human Impacts on Marine Ecosystems

Overfishing and Bycatch

• Overfishing occurs when fish are caught at a rate faster than they can reproduce, leading to the depletion of fish populations and the disruption of marine food webs
• Examples of overfished species include Atlantic cod, bluefin tuna, and several species of sharks
• Bycatch, the unintentional capture of non-target species during fishing, can result in the death of many marine animals, including dolphins, sea turtles (loggerhead, leatherback), and seabirds (albatrosses, petrels)
• Fishing methods such as bottom trawling and longline fishing are particularly prone to high levels of bycatch

Pollution and Marine Debris

• Pollution from land-based sources, such as agricultural runoff (pesticides, fertilizers), industrial waste (heavy metals, chemicals), and sewage, can introduce harmful chemicals and excess nutrients into marine ecosystems, leading to eutrophication and the creation of dead zones
• The Gulf of Mexico dead zone, caused by nutrient runoff from the Mississippi River, is one of the largest in the world and can reach sizes of over 6,000 square miles
• Marine debris, particularly plastic waste, can entangle or be ingested by marine animals, causing injury, starvation, and death
• The Great Pacific Garbage Patch, a large accumulation of plastic debris in the North Pacific Ocean, is estimated to cover an area twice the size of Texas

Habitat Destruction

• The destruction of coastal habitats, such as mangrove forests and coral reefs, through development (coastal construction, aquaculture), pollution, and climate change, can reduce biodiversity and the ecosystem services these habitats provide
• Mangrove forests, which serve as nurseries for many fish species and protect coastlines from erosion and storms, have declined by over 35% worldwide in the past 50 years
• Coral reefs, which support an estimated 25% of all marine life, are threatened by a combination of factors, including ocean acidification, warming temperatures, and pollution
• The Great Barrier Reef, the world's largest coral reef system, has experienced several mass bleaching events in recent years, leading to widespread coral mortality

Climate Change Effects on Oceans

Ocean Warming and Coral Bleaching

• Rising atmospheric carbon dioxide levels, primarily due to human activities (fossil fuel combustion, deforestation), are causing an increase in global ocean temperatures, a process known as ocean warming
• The average global sea surface temperature has increased by approximately 0.13°C per decade since 1901
• Warmer ocean temperatures can lead to coral bleaching, where coral polyps expel their symbiotic algae (zooxanthellae), often resulting in the death of the coral and the loss of reef habitats
• The 2016 global coral bleaching event, the longest and most severe on record, affected over 70% of the world's coral reefs

Ocean Acidification

• The absorption of atmospheric carbon dioxide by the oceans is causing ocean acidification, as the dissolved carbon dioxide reacts with water to form carbonic acid, lowering the pH of the ocean
• The average pH of the ocean surface has decreased by approximately 0.1 units since the start of the industrial era, representing a 30% increase in acidity
• Ocean acidification can impair the ability of calcifying organisms, such as corals and some plankton (coccolithophores, foraminifera), to build their calcium carbonate shells and skeletons, potentially disrupting marine food webs
• Experimental studies have shown that ocean acidification can also affect the behavior and survival of some marine species, such as fish and mollusks

Sea Level Rise

• Melting land-based ice, such as glaciers and ice sheets (Greenland, Antarctica), and thermal expansion of seawater due to rising temperatures are causing global sea levels to rise, threatening low-lying coastal areas and islands
• Global average sea level has risen by approximately 21-24 centimeters since 1880, with about a third of that occurring in the last 25 years
• Sea level rise can lead to increased coastal flooding, erosion, and saltwater intrusion into freshwater aquifers and wetlands
• Low-lying island nations, such as the Maldives and Tuvalu, are particularly vulnerable to sea level rise and may become uninhabitable by the end of the century

Sustainable Ocean Management

Fisheries Management and Marine Protected Areas

• Sustainable fisheries management practices, such as setting catch limits, implementing no-take zones, and reducing bycatch, can help maintain fish populations and ensure the long-term viability of the fishing industry
• Catch shares, a management approach that allocates a portion of the total allowable catch to individual fishers or communities, have been shown to reduce overfishing and improve the economic performance of fisheries
• Marine protected areas (MPAs) are designated regions where human activities are restricted or prohibited to protect marine ecosystems, biodiversity, and ecosystem services
• The Ross Sea MPA in Antarctica, established in 2016, is the world's largest MPA and covers an area of 1.55 million square kilometers

International Agreements and Regulations

• International agreements and regulations, such as the United Nations Convention on the Law of the Sea (UNCLOS) and the International Whaling Commission (IWC), aim to promote the sustainable use and conservation of marine resources
• UNCLOS, adopted in 1982, establishes a legal framework for the use and protection of the world's oceans, including provisions for the conservation of living marine resources and the prevention of pollution
• The IWC, established in 1946, aims to conserve whale populations and regulate whaling activities, and has implemented a moratorium on commercial whaling since 1986

Reducing Pollution and Promoting Awareness

• Reducing land-based pollution through better waste management (recycling, proper disposal), improved agricultural practices (reduced pesticide and fertilizer use), and stricter industrial regulations (wastewater treatment, emission controls) can help protect marine ecosystems and maintain water quality
• The International Convention for the Prevention of Pollution from Ships (MARPOL), adopted in 1973, sets standards for the prevention of pollution by oil, chemicals, sewage, and garbage from ships
• Promoting public awareness and education about the importance of marine conservation and the impacts of human activities on the oceans can encourage more sustainable practices and support for conservation efforts
• The annual World Oceans Day, celebrated on June 8, aims to raise global awareness of the importance of the oceans and encourage action to protect marine environments