Rivers & Streams
Abbey Rahier and Jackie Sanchez
Rivers and Streams are home to a diverse population of species ranging from small bacteria to large mammals. A variety of factors determine which type of organisms live in these lotic ecosystems including water current, light intensity, temperature, pH levels, dissolved oxygen, salinity, and available nutrients. These factors vary all throughout the stream and river system which is why different species are found at different sections of rivers and streams. Species that live in rivers and streams have adaptations to address the constant presence of water flow currents. Many creatures expend a lot of energy while swimming against the current. This is in contrast to lake animals who are unfamiliar to opposing currents and allow themselves to be passively taken by it. Animals must also adapt to drift, the constant flow of water toward the sea. This carries nutrients and organisms downstream.
Bacteria are present in large numbers in these water systems. They play an important role in energy recycling since they decompose organic matter into inorganic compounds. This is a crucial step so plants and other microbes have material they can use for energy. Invertebrates characterized as having no backbone or spinal column are also a diverse category found in this ecosystem. Examples of this division on the animal kingdom are crayfish, snails, limpets, mussels, insects, and clams.
Invertebrates rely on the current to bring them food and oxygen. They are both consumers and prey in the river and stream food webs. A large number of the invertebrates found in river systems are insects. They are found on the water surface, on and under stones, in or below substrate, and throughout the water column. Insects are an important part of the river and stream food web and are used by ecologists as indicator species. A mix of insects indicates whether a stream is healthy or not. A common species used during stream health surveillance is the mayfly. They are known to only thrive in gently, unpolluted streams. During the surveillance, a stream is considered healthy when there are lots of mayfly larvae. However, if no mayflies are found a stream could be in trouble.
Fish species that are successful in rivers and streams are determined by their speed and stamina. This qualification is required for survival due to the immense amount of energy needed to swim against the current. Most fish remain close to the bottom, the banks, or behind obstructions. Fish only swim in the current to feed or change locations. Fish are both consumers and prey in the food web. Many species, such as the eel, have life cycles that require stages in multiple water systems. The American eel is the only species of freshwater eel found in North America. Adults spawn in the Sargasso Sea. Once hatched, eels will then drift inland with ocean currents into streams, rivers, and lakes which takes many years. Young eels will live in freshwater until they reach maturity and migrate back to the Sargasso Sea.
Birds, although not residents of water, are an important member of the river and stream ecosystem. Rivers and streams are used by bird species as a place to eat, nest, rest, or use as a means of navigation. Fish and water invertebrates are important food sources for water birds. Duck, geese, and other waterfowl are commonly seen on each continent. The bald eagle, an Endangered Species Act success story, requires habitat close to rivers, estuaries, large lakes, and some seacoasts where there is sufficient food supply. They are opportunistic feeders dining on fish, waterfowl, turtles, and water birds.
A variety of amphibians and reptiles are found in rivers and streams including frogs, newts, turtles, crocodiles, alligators, and snakes. This is not a restrictive list as there are many other species of amphibians and reptiles in these ecosystems as well. These species act as both predator and prey in rivers and streams. Water is an important feature for amphibians to complete their life cycle since many amphibian eggs must be laid in water. Reptiles will spend their life cycle both on land and in water. Rivers and streams are an important habitat for reptiles to find food and shelter. Water snakes rely on finding prey associated with rivers and streams. In shallow waters, they will wait with their mouths open until a prey species passes by. They also search for prey by moving rocks and branches and investigation crevices where prey might hide.
Mammals that rely on rivers and streams are truly unique and play a critical role in this ecosystem. Some examples of mammals found in river and stream habitats are platypi, African hippopotamuses, otters, and beavers. Due to overhunting, beavers live in small numbers in certain areas of Europe and throughout North America. Beavers are ecosystem engineers, building dams which alter the flow of rivers and change flood patterns which raise the water table to help purify the water and break down toxins. When flooding occurs, sediment and debris builds up, carbon levels increase, nitrogen decreases and ultimately changes the chemical composition of the area. Now, new types of invertebrates can survive and birds, fish, and amphibians are attracted to the new source of water.
Threats to aquatic species are mainly due to human causes. Some of the main threats to organisms living in river and stream habitats are agricultural practices, recreational activities, chemical or organic pollution, climate change, and the introduction of non-native species. Water quality is very important and slight changes in chemical composition make it harder for these specialized species to survive. Non-native species present challenges to threatened and endangered species by increasing competition, predation, hybridization, and habitat modifications. Although some non-native species range is limited by the freezing water temperature that occurs during winter, non-native species are still diminishing native populations during non-winter months and in places where the water does not freeze over.
Any policy that is limiting the amount of pollution from the industrial sector, agricultural industry, and individual households will improve the water quality and therefore help all the living organisms relying on this ecosystem. It is important to focus on initiatives that are aimed at the root of the issue. It is harder to work on species specific conservation when the rivers and streams are inhabitable.
Issues Within Rivers and Streams
We use rivers and streams for many different purposes. Traditionally, these waters have been used for recreation, drinking, agriculture, sewage, and more. With all of these different uses come a series of issues. Water quality is a growing environmental issue around the world and is affecting not just humans but wildlife as well. Approximately 80% of the world’s waste water is being dumped back into rivers and streams without being treated first. More people are killed due to inadequate drinking water than in war. Pollution can come from many different places. In the United States, the number one polluter is from agriculture practices. Fertilizers, pesticides, and animal waste are polluting rivers and streams when rainwater runoff carries toxins to the natural water sources. Sewage and wastewater are also being added to our waterways. When it rains, chemicals on our streets are being picked up and washed into storm drains which lead to nearby rivers. Many countries don’t have proper ways to treat sewage and it ends up in the water cycle. All of these pollutants are creating poor water quality around the world.
Another issue that impacts rivers and streams is deforestation. Deforestation is the act of removing trees to make room for alternative use such as commercial development or housing. Trees hold water within them which eventually evaporates and returns to the water cycle through transpiration. Without these trees water isn’t being evaporated in that area and instead ends up flowing away in rivers. So, the area that was once rich in forests and rain are now turning into dry deserts. Deforestation also adds to climate change which creates extreme weather events. Events such as floods or droughts are then changing the shape and size of streams and rivers, and altering the type of wildlife that live there. Trees not only hold water within them, but also anchor soil. When the trees are taken away and a heavy rainfall occurs, soil is then loosened and added to nearby rivers and streams. The extra soil can raise riverbeds and create floods. It also can kill organisms like fish eggs by smothering them with soil.
Dams were created for hydropower, to help control water flow, and for irrigation. However, they are damaging to rivers and their ecosystems. In the United States, there are at least 90,000 dams that are blocking our waterways. Rivers and streams are homes to migratory species like fish. When dams are in place, they take away their access to spawning habitats, food, and places to hide from predators. Some dams create fish ladders to help fix this issue, but this usually isn’t enough. Dams slow down water flow which can lengthen migration periods and impact natural flow variations. They create pools of still or slow moving water which is able to heat up and impact the organisms that reside there. Algae blooms occur in warmer water and can create water quality issues. Just like deforestation adding sediment to rivers, dams build up sediment and can bury fish eggs on the bottom of the river.
Dams, deforestation, and water quality all tie into the big issue of climate change. Climate change impacts rivers the most by increasing temperatures. This creates less consistent winter weather, usually ending up with less annual snow and precipitation, and earlier snowmelt in the spring resulting in low water flows and increased water temperatures. These increased water temperatures can create toxic algae blooms which kill organisms within the water. As well, many fish species can only live in a small range of water temperatures so if these change they have to find new rivers to live in or they will die. Pollution impacts intensify when there is low water flow. Droughts and floods also increase due to changing weather patterns, which can completely alter a landscape. In some instances rivers have completely dried up due to changing weather patterns.
Policies Addressing the Issues
Around the world there are cases of countries trying to protect our waterways. In the United States, the Clean Water Act was created to protect water from pollution. The longest river in Africa, the Nile River, has been undergoing serious issues and 10 countries have come together to form the Nile Basin Initiative in order to fix some of the problems. In China, the Yangtze River has the Yangtze River Economic Belt which doesn’t allow industry projects within one kilometer of the river.
Before the Clean Water Act was created in 1972, rivers around the country were catching on fire due to high amounts of industrial pollution being freely dumped. The most famous river fire on the Cuyahoga River in Ohio was a turning point for America. After this fire, people were protesting for laws to be put in place to protect water. The Clean Water Act was then created in order to protect all waters from pollution and destruction. Point sources, which are direct sources of pollution like a sewage treatment plant, are monitored well under this act and have saved billions of pounds of pollutants from entering waterways. Where there needs to be stronger laws is when it comes to nonpoint sources. Nonpoint sources come from water picking up pollution on roads or landscapes and taking them to waterways. A lot of good has come from the act, but in order to lessen the amount of pollutants entering the rivers and streams now would be to find ways to restrict nonpoint sources.
In 1999, the Nile Basin Initiative was formed within 10 different countries in Africa. This initiative was created to bring each country that is within the Nile Basin come together to protect the river while still benefiting each country economically. The river is the only source of renewable water within this area, and most countries within the basin are semi-arid or arid drylands. It is also essential to most food and water security and there have been conflicts between countries due to the dependency everyone has on the river. The main task the initiative is focused on today is making sure the water is being managed sustainably since climate change can greatly impact these countries. Many communities are financially impoverished and economically rely on the river for agriculture, fishing, etc. If the water isn’t managed properly, many people could be without clean water or income.
China has been rapidly developing for decades and the Yangtze River has taken a heavy toll from it. Heavy amounts of pollution as well as low water flow has impacted almost every province’s ecosystem along the river. Over 400 million people rely on the river. This is why the Yangtze River Economic Belt was created. With this came the removal of the Chemical Industry Park which was located along the river. The goal of the Yangtze River Economic Belt is to lessen industry pollution by not allowing industry projects within one kilometer of the river. In one city alone, over 256 factories have been moved off of the river. Since the creation of the economic belt in 2016, water quality and GDP have improved.
What You Can Do
Each of those examples show that there are laws and initiatives being implemented in hopes of protecting the world’s rivers and streams. There are also ways that each of us can help in our own ways to protect waterways. One way would be to learn where your water comes from. We use water in our homes in a multitude of ways – drinking, showering, appliances, and even watering our lawns. But, that water is usually sourced from rivers and streams. In order to protect our health with clean drinking water, we need to keep our rivers clean. This can be done by knowing what you can and can’t put into wastewater treatment facilities. For example, a lot of prescription pills get dumped into toilets or sinks and can’t always be removed at treatment facilities and end up in our waterways.
Another way you can take care of rivers and streams is by recycling. Around 0.5 to 2.75 million tons of trash comes from rivers. Streams and rivers eventually lead to the ocean, where 1 million seabirds, 100,000 sea mammals, and too many to count fish die each year due to pollution in our waterways. By following the refuse, reduce, reuse, recycle motto we could lessen the amount of plastic ending up in our waterways. To benefit rivers and streams even more, clean up trash within your community. Get your friends and family together and walk around to find trash that has been left behind and dispose of it properly (don’t forget to wear gloves). These few ideas can go a long way and can create safer water for not only your community but others around the world.
Sources: American Rivers, Big Think, California Coastkeeper Alliance, International Rivers, Mongabay, Nile Basin Initiative, NRDC, The Brussels Times