Overfishing
Humans have subsisted on fishing for millennia, however, technological advancement has broadened the scope of our nets with disastrous results. Fisherman focus on catching large species like cod, swordfish, and tuna. Business wise, this makes sense, a bigger fish will be worth more. However, over the last 50 years, the number of large predator fish like tuna has dropped by 90%. The good part is that overfishing can be prevented with better management systems. In places like Belize, Denmark & the United States, the implementation of fishing rights has transformed struggling fisheries. In the Gulf of Mexico, red snapper populations are three times what they were in 2007 after fishing rights were introduced. Marine life is good at bouncing back, but only if humans take the necessary steps to give them a fighting chance.
Coastal Pollution
We have previously written about the massive dead zone that is wreaking havoc in the Gulf Of Mexico. Human runoff increases the amount of nitrogen and phosphorus in the water. These two chemicals cause Cyanobacteria to bloom, and since plankton and animals can’t eat Cyanobacteria, it quickly spreads to epidemic levels. When it dies, bacterial degradation consumes the oxygen from the water creating a state of hypoxia, or lack of oxygen. While some fish can escape, many are rendered unconscious too quickly to take evasive action. One of the major issues with dead zones isn’t the fish that are dying; it’s the fish that aren’t. Jellyfish can thrive in dead zones and the absence of predators attracts massive blooms of them. The mucus and waste produced by the jellyfish lead to major changes in the food webs in the ocean.
Habitat Destruction
Wetlands are filled in to accommodate urban development, runoff wreaks havoc on reefs and coastal areas, and inland dams decrease nutrient-rich runoff. These are just a few of the ways marine habitats are being destroyed. The effects of this destruction have serious implications both in the oceans and on land. Salmon, for example, are struggling to complete their migration in the face of water diversions, dams, and logging. But this isn’t just a problem for the salmon, it’s also a huge problem for the bears that need to eat the salmon in order to bulk up before their winter hibernation.
Warming
As Earth’s temperature rises, the excess heat is primarily absorbed by the oceans. The increased temperature melts ice caps, kills coral and forces species to move into new territories. This also has significant effects on humans. The altered distributions of fish can pose a serious threat to food security and people’s livelihoods worldwide. It also leads to more intense hurricanes that can cause widespread disaster. Warm water is the primary source of energy for hurricanes, so the increasing ocean temperatures have resulted in more frequent and more intense hurricanes in recent years causing massive destruction and loss of life.
Acidification
The ocean absorbs about 30% of the carbon dioxide that’s released into the atmosphere. When absorbed by seawater, the CO2 causes a series of chemical reactions that result in increased concentrations of hydrogen ions, making the water more acidic and decreasing carbonate ions. This is significant because carbonate ions are crucial building blocks for seashells and coral. More acidic waters also affect some species’ abilities to detect predators and find safe environments.