human impact on marine life human impact on marine life human activities affect marine life and marine habitats through overfishing, habitat loss, the introduction of invasive species, ocean pollution, ocean acidification and ocean warming. these impact marine ecosystems and food webs and may result in consequences as yet unrecognised for the biodiversity and continuation of marine life forms. global cumulative human impact on the ocean part of a series of overviews onmarine life marine habitats marine microorganisms marine microbiomes marine viruses marine prokaryotes marine protists marine fungi marine invertebrates marine vertebrates marine primary production marine food web marine carbon pump marine biogeochemical cycles human impact on marine life marine conservation marine life portal the ocean can be described as the world's largest ecosystem and it's home for many species of marine life. different activities done and caused by human beings such as global warming, ocean acidification, and pollution affects marine life and its habitats. for the past 50 years, more than 90 percent of global warming brung on by humans has been absorbed into the ocean. this results in the rise of ocean temperatures and ocean acidification which is harmful to many fish species and causes damage to habitats such as coral. with coral producing materials such as carbonate rock and calcareous sediment, this creates a very unique and valuable ecosystem not only providing food/homes for marine creatures but also having many benefits for humans too. ocean acidification caused by rising levels of carbon dioxide leads to coral bleaching where the rates of calcification is lowered affecting coral growth. additionally, another issue caused by humans which impacts marine life is marine plastic pollution, which poses a threat to marine life. according to the ipcc (2019), since 1950 "many marine species across various groups have undergone shifts in geographical range and seasonal activities in response to ocean warming, sea ice change and biogeochemical changes, such as oxygen loss, to their habitats." it has been estimated only 13% of the ocean area remains as wilderness, mostly in open ocean areas rather than along the coast. overfishing fishing down the foodweb. overfishing of high trophic fish like tuna can result in them being replaced by low trophic organisms, like jellyfish overfishing is occurring in one third of world fish stocks, according to a 2018 report by the food and agriculture organization of the united nations. in addition, industry observers believe illegal, unreported and unregulated fishing occurs in most fisheries, and accounts for up to 30% of total catches in some important fisheries. in a phenomenon called fishing down the foodweb, the mean trophic level of world fisheries has declined because of overfishing high trophic level fish. "it is almost as though we use our military to fight the animals in the ocean. we are gradually winning this war to exterminate them." – daniel pauly, pioneer on human impacts on global fisheries, habitat loss relationship between annual trend and current cumulative impacts for different marine ecosystems coastal ecosystems are being particularly damaged by humans. significant habitat loss is occurring particularly in seagrass meadows, mangrove forests and coral reefs, all of which are in global decline due to human disturbances. coral reefs are among the more productive and diverse ecosystems on the planet, but one-fifth of them have been lost in recent years due to anthropogenic disturbances. coral reefs are microbially driven ecosystems that rely on marine microorganisms to retain and recycle nutrients in order to thrive in oligotrophic waters. however, these same microorganisms can also trigger feedback loops that intensify declines in coral reefs, with cascading effects across biogeochemical cycles and marine food webs. a better understanding is needed of the complex microbial interactions within coral reefs if reef conservation has a chance of success in the future. seagrass meadows have lost 30,000 km2 (12,000 sq mi) during recent decades. seagrass ecosystem services, currently worth about $us1.9 trillion per year, include nutrient cycling, the provision of food and habitats for many marine animals, including the endangered dugongs, manatee and green turtles, and major facilitations for coral reef fish. one-fifth of the world's mangrove forests have also been lost since 1980. the most pressing threat to kelp forests may be the overfishing of coastal ecosystems, which by removing higher trophic levels facilitates their shift to depauperate urchin barrens. invasive species a cargo ship pumps ballast water over the side. an invasive species is a species not native to a particular location which can spread to a degree that causes damage to the environment, human economy or human health. in 2008, molnar et al. documented the pathways of hundreds of marine invasive species and found shipping was the dominant mechanism for the transfer of invasive species in the ocean. the two main maritime mechanisms of transporting marine organisms to other ocean environments are via hull fouling and the transfer of ballast water. mnemiopsis leidyi ballast water taken up at sea and released in port is a major source of unwanted exotic marine life. the invasive freshwater zebra mussels, native to the black, caspian, and azov seas, were probably transported to the great lakes via ballast water from a transoceanic vessel. meinesz believes that one of the worst cases of a single invasive species causing harm to an ecosystem can be attributed to a seemingly harmless jellyfish. mnemiopsis leidyi, a species of comb jellyfish that spread so it now inhabits estuaries in many parts of the world, was first introduced in 1982, and thought to have been transported to the black sea in a ship's ballast water. the population of the jellyfish grew exponentially and, by 1988, it was wreaking havoc upon the local fishing industry. "the anchovy catch fell from 204,000 tons in 1984 to 200 tons in 1993; sprat from 24,600 tons in 1984 to 12,000 tons in 1993; horse mackerel from 4,000 tons in 1984 to zero in 1993." now that the jellyfish have exhausted the zooplankton, including fish larvae, their numbers have fallen dramatically, yet they continue to maintain a stranglehold on the ecosystem. invasive species can take over once occupied areas, facilitate the spread of new diseases, introduce new genetic material, alter underwater seascapes, and jeopardize the ability of native species to obtain food. invasive species are responsible for about $138 billion annually in lost revenue and management costs in the us alone. marine pollution this section is an excerpt from marine pollution. marine pollution occurs when substances used or spread by humans, such as industrial, agricultural and residential waste, particles, noise, excess carbon dioxide or invasive organisms enter the ocean and cause harmful effects there. the majority of this waste (80%) comes from land-based activity, although marine transportation significantly contributes as well. since most inputs come from land, either via the rivers, sewage or the atmosphere, it means that continental shelves are more vulnerable to pollution. air pollution is also a contributing factor by carrying off iron, carbonic acid, nitrogen, silicon, sulfur, pesticides or dust particles into the ocean. the pollution often comes from nonpoint sources such as agricultural runoff, wind-blown debris, and dust. these nonpoint sources are largely due to runoff that enters the ocean through rivers, but wind-blown debris and dust can also play a role, as these pollutants can settle into waterways and oceans. pathways of pollution include direct discharge, land runoff, ship pollution, bilge pollution, atmospheric pollution and, potentially, deep sea mining. the types of marine pollution can be grouped as pollution from marine debris, plastic pollution, including microplastics, ocean acidification, nutrient pollution, toxins and underwater noise. plastic pollution in the ocean is a type of marine pollution by plastics, ranging in size from large original material such as bottles and bags, down to microplastics formed from the fragmentation of plastic material. marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. plastic pollution is harmful to marine life. another concern is the runoff of nutrients (nitrogen and phosphorus) from intensive agriculture, and the disposal of untreated or partially treated sewage to rivers and subsequently oceans. these nitrogen and phosphorus nutrients (which are also contained in fertilizers) stimulate phytoplankton and macroalgal growth, which can lead to harmful algal blooms (eutrophication) which can be harmful to humans as well as marine creatures. excessive algal growth can also smother sensitive coral reefs and lead to loss of biodiversity and coral health. a second major concern is that the degradation of algal blooms can lead to consumption of oxygen in coastal waters, a situation that may worsen with climate change as warming reduces vertical mixing of the water column. nutrient pollution nutrient pollution is a primary cause of eutrophication of surface waters, in which excess nutrients, usually nitrates or phosphates, stimulate algae growth. this algae then dies, sinks, and is decomposed by bacteria in the water. this decomposition process consumes oxygen, depleting the supply for other marine life and creating what is referred to as a "dead zone." dead zones are hypoxic, meaning the water has very low levels of dissolved oxygen. this kills off marine life or forces it to leave the area, removing life from the area and giving it the name dead zone. hypoxic zones or dead zones can occur naturally, but nutrient pollution from human activity has turned this natural process into an environmental problem. there are five main sources of nutrient pollution. the most common source of nutrient runoff is municipal sewage. this sewage can reach waterways through storm water, leaks, or direct dumping of human sewage into bodies of water. the next biggest sources come from agricultural practices. chemical fertilizers used in farming can seep into ground water or be washed away in rainwater, entering water ways and introducing excess nitrogen and phosphorus to these environments. livestock waste can also enter waterways and introduce excess nutrients. nutrient pollution from animal manure is most intense from industrial animal agriculture operations, in which hundreds or thousands of animals are raised in one concentrated area. stormwater drainage is another source of nutrient pollution. nutrients and fertilizers from residential properties and impervious surfaces can be picked up in stormwater, which then runs into nearby rivers and streams that eventually lead to the ocean. the fifth main source of nutrient runoff is aquaculture, in which aquatic organisms are cultivated under controlled conditions. the excrement, excess food, and other organic wastes created by these operations introduces excess nutrients into the surrounding water. toxic chemicals