Major threats to the marine ecosystem include overfishing, various types of pollution, and climate change. Human activities, both on land and at sea, are the primary causes of these stressors, resulting in habitat destruction, biodiversity loss, and ecological imbalance.
What are the Threats to Marine Ecosystems?
Overexploitation and habitat destruction
Overfishing has depleted global fish stocks, disrupted the marine food web, and led to the near extinction of key species, ultimately affecting the entire ecosystem. Practices like bottom trawling and dredging damage the seafloor. Bycatch, the accidental capture of non-target animals, such as dolphins and turtles, also reduces marine populations. Coastal development, including land reclamation and shoreline construction, harms vital habitats such as mangroves, seagrass beds, and coral reefs.
Pollution
Plastic pollution introduces millions of tons of waste into the ocean each year, threatening over 2,000 marine species. Animals get tangled in plastic or mistake microplastics for food, risking starvation. Chemical pollution from land runoff carries toxins, waste, and pesticides, which accumulate in the food chain and cause health problems, including diseases and reproductive issues. Nutrient pollution from fertilizers and sewage leads to algal blooms that deplete oxygen, resulting in "dead zones" where marine life cannot survive. In addition to large tanker spills, thousands of smaller ones release toxic hydrocarbons every year, harming marine life.
Climate Change
Climate change affects oceans through warming, acidification, and rising sea levels. Ocean warming has absorbed over 90% of the excess heat, causing coral bleaching and altering species migration patterns. Ocean acidification, driven by absorbing approximately one-third of human CO2, lowers the pH of seawater, harming organisms such as corals and plankton. Rising sea levels, resulting from melting ice, threaten coastal ecosystems through flooding and changes in salinity.
Other threats
Invasive species, often transported in ship ballast water, can outcompete native species, disrupt food webs, and cause economic harm. Underwater noise from shipping, sonar, and surveys interferes with the communication, migration, and hunting of marine mammals. Land clearing causes soil erosion, leading to sediment runoff that smothers bottom-dwelling organisms and blocks sunlight, disrupting photosynthesis.