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Human impact on aquatic environments

Human activities, including the use of resources, have physical, chemical, and biological consequences for ecosystems. Damage to coral reefs, the impacts of oil spills, and oceanic dead zones are some examples of human impacts on aquatic environments. Created by Khan Academy.

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Video transcript

- [Narrator] When you go to the beach and you look at the ocean, it oftentimes might look fine. But as we'll see in this video, we, human beings have been stressing aquatic environments. And if we're not careful, we might completely ruin them. For example, this is what a healthy coral reef looks like. And coral are fascinating organisms. You can view them as little animals that are fixed in place because they're releasing this calcium carbonate the same things that eggshells are made of that they're fixed too and then that builds the coral reef. But they can exist, they have their homeostasis in a particular temperature range and a given amount of various chemicals that are in the water. Now we know that human beings were causing the climate to warm, and that's all also causing ocean temperatures to warm and as ocean temperatures warm, many of our coral reefs are not able to be as sustainable. For example, this is a less healthy coral reef. Some of the coral is still alive and seemingly doing okay, but in other places, you see what is known as bleaching, where the reef is now white and that's because in those situations, the coral is essentially dying off. Now you might say, well, this is unfortunate because coral reefs are very beautiful and now it is less beautiful. But what are the other impacts? Well, all sorts of organisms and animals live in coral reefs, get their food from it, get their shelter from it and if the coral reef start to die off, then the animals are going to die off. On top of that, these coral reefs that the coral are essentially building as they live, they prevent erosion on the coastlines. So one change that affects one organism or one part of an ecosystem can have a lot of follow on effects on other parts of the ecosystem. Another perhaps more obvious way that we've been not being nice to aquatic environments is things like oil spills. And you've probably seen this on the news when you have major oil spills, they tend to be pretty disturbing images, but this right here is a bird that is covered in oil. And you can imagine when a bird is covered in oil, it's not going to be able to fly, it's not going to be able to swim, it's not going to be able to have food and in a lot of cases, it is likely to die. And just as we described at the coral reef, this doesn't just affect the bird, it affects the entire ecosystem, including human beings. And this is just the effect on a bird, it has affects on the fish, it has effects on the just natural balance that occurs in that aquatic environment. Now, another idea that is less talked about is this notion of oceanic dead zones. And this right over here is a picture of the gulf coast right off the coast of Louisiana, I was actually born right around there. And what it shows is every year, this hypoxic zone, which is a zone of low oxygen levels in the water form off the coast, and this shows how bad it is. The red areas are the really bad, very low oxygen. Sometimes you might forget, and you might say, okay, for all of us who live in the land or live on the land or in the air, we breathe oxygen, but organisms in the water need oxygen as well. Oxygen that has been dissolved in the water. And what's interesting is why this forms, it's actually a little bit counter-intuitive. It turns out that chemicals from human runoff, especially fertilizer. So you might not realize it, but this is the Delta of the Mississippi river. And that has run off farm runoff from as far north as Minnesota and Chicago and sewage and that farm runoff and that fertilizer and that sewage, as it comes into the Gulf, it actually promotes algae formation. And you might say, well, that's good. Some more life is growing, but so much algae gets formed and when that algae finally dies and it gets decomposed, the decomposers actually use the oxygen. Remember, when you are actually trying to metabolize things, you're using oxygen in order to extract that energy. And so the oxygen in the ocean in that area gets depleted, and then you have a situation where almost nothing can live in these zones right over here. And this is just a sample of the things that we are doing to our aquatic environment. And there's other things, there's elemental sources of mercury that we throw into aquatic environments, and it makes the water highly toxic. There's obviously other forms of trash, pollution, that we've put into the water but this is just to give you a sense and to start giving you an appreciation about how imbalanced everything is and how in one part of the country say in Chicago waste that's going into the Mississippi River can affect aquatic environments, thousands of miles away.