Climate Change and Its Effect on Aquatic Life

April 26, 2021Lu Shegay


Climate change has become a serious issue not only in the animal law community but also had an effect on all of our lives. A lot of people still do not understand the issue with climate change, how it actually affects our lives, and what consequences we may have if no reaction and necessary steps will be taken. Climate change impacted the entire ecosystem causing extreme weather conditions, such as wildfires, ice storms, oceans’ heat, which also affected thousands of animals. This article will discuss how aquatic life, in particular, is already affected by the climate change effect and the possible fatal consequences for our planet. Aquatic animals mean not only fish but also other animals living in the water, such as amphibians, marine mammals, crustaceans, reptiles, mollusks, aquatic birds, aquatic insects, starfish, and corals.

Causes of climate change

A factor that affects the climate is called “climate forcing,” which in its turn has two types: internal forcing mechanism and external forcing mechanism. The former is caused naturally, e.g, thermohaline circulation. The latter one has two types, which are natural disasters (volcanic eruptions) and anthropogenic activities, including greenhouse gas emissions. Unfortunately, there have been a lot of studies proving that human activities are the major cause of climatic change. With that being said, one of the major reasons is livestock farming, where methane is exposed in the atmosphere. CAFOs are known for not only air pollution but also water pollution due to leaks, runoff. Another issue associated with climate change is the use of fertilizers in agriculture and aquaculture. These fertilizers that are applied in the industry contain a large amount of nitrous oxide, which leads to the increase of the Earth’s surface temperature.

"Polar bear" by mape_s is licensed under CC BY 2.0

Major effects of climate change on aquatic life

Oceans’ heat

For the past century, the average temperature of Earth has risen by 1.5°F, and aquatic animals are feeling these changes too. The ocean’s temperature becomes higher, and, according to the National Oceanic and Atmospheric Administration (NOAA), sea surface temperature rose on average by 0.13°F per decade during 1901-2015. But not every part of the world has experienced a temperature rise, some places have been cooling, e.g, the areas of the North Atlantic.

“Sea surface temperature—the temperature of the water at the ocean surface—is an important physical attribute of the world’s oceans. The surface temperature of the world’s oceans varies mainly with latitude, with the warmest waters generally near the equator and the coldest waters in the Arctic and Antarctic regions. As the oceans absorb more heat, sea surface temperature increases, and the ocean circulation patterns that transport warm and cold water around the globe change.”

“Changes in sea surface temperature can alter marine ecosystems in several ways. For example, variations in ocean temperature can affect what species of plants, animals, and microbes are present in a location, alter migration and breeding patterns, threaten sensitive ocean life such as corals, and change the frequency and intensity of harmful algal blooms such as “red tide.” Over the long term, increases in sea surface temperature could also reduce the circulation patterns that bring nutrients from the deep sea to surface waters. Changes in reef habitat and nutrient supply could dramatically alter ocean ecosystems and lead to declines in fish populations, which in turn could affect people who depend on fishing for food or jobs.”

Read more: NOAA: Climate Change Indicators: Sea Surface Temperature


The level of acid in the ocean is increasing because of the increasing carbon dioxide level caused by anthropogenic activities. It has been reported that the carbon dioxide concentrations are now higher than in the last 800 000 years. The increased acidity affects shellfish as they become weaker and easier for predators to eat. Coral reefs are also under the climate change impact because it becomes difficult for them “to create and maintain the skeletal structures needed for their support and protection.” It was reported by the Environmental Protection Agency of the United States that “without action on climate change, dramatic loss of shallow coral cover is predicted to occur.”

“Although the ocean’s ability to take up carbon dioxide prevents atmospheric levels from climbing even higher, rising levels of carbon dioxide dissolved in the ocean can have a negative effect on some marine life. Carbon dioxide reacts with seawater to produce carbonic acid. The resulting increase in acidity (measured by lower pH values) changes the balance of minerals in the water. This makes it more difficult for corals, some types of plankton, and other creatures to produce a mineral called calcium carbonate, which is the main ingredient in their hard skeletons or shells. Thus, declining pH can make it more difficult for these animals to thrive. This can lead to broader changes in the overall structure of ocean and coastal ecosystems, and can ultimately affect fish populations and the people who depend on them.”

Read more: NOAA: Climate Change Indicators: Ocean Acidity


Another effect of climate change is heavy precipitation that can pollute coastal waters. For example, heavy rain in coastal areas can lead to increased runoff and flooding. Some coastal regions are already experiencing so-called “dead zones,” where “water is depleted of oxygen because of pollution from agriculture fertilizers, delivered by runoff.”

“Climate change can affect the intensity and frequency of precipitation. Warmer oceans increase the amount of water that evaporates into the air. When more moisture-laden air moves over land or converges into a storm system, it can produce more intense precipitation—for example, heavier rain and snowstorms. The potential impacts of heavy precipitation include crop damage, soil erosion, and an increase in flood risk due to heavy rains (see the River Flooding indicator)—which in turn can lead to injuries, drownings, and other flooding-related effects on health. In addition, runoff from precipitation can impair water quality as pollutants deposited on land wash into water bodies.”

Read more: NOAA: Climate Change Indicators: Heavy Precipitation

"Sea Ice in the Chukchi Sea" by NASA Goddard Photo and Video is licensed under CC BY 2.0

Animals affected

Aquatic animals are affected by the changes in our climate as well as other categories of animals. It was reported that the Indian seas’ temperature will increase by 33-37°F (1-3°C). These numbers may seem insignificant to us, but the Earth may simply be erased if the temperature continues rising by 2°C every year. One of the first species that will be affected is plankton because they form “the basis of the food chain in the marine ecosystem.” Along with planktons, other animals will be affected, such as coral reefs, fish, sea birds, etc. Of course, melting ice cannot be missed when talking about the climate change effect on aquatic animals. With melting ice, polar bears, for example, are losing their habitat, and, with no steps taken, they may become extinct in 50 years. Moreover, due to increased level of acid in the ocean, such animals as oysters, shrimps, and coral reefs will not be able to “form their outer covering or shell through the process of calcification,” and “the entire marine food web will be affected because of the formation of cracks in the marine food chain.”

With regard to freshwater species of aquatic animals, they are too vulnerable to climatic change. “According to Field and coworkers, the negative impact was observed on the cold-water species and positive impact on the warm-water species. Due to the acute effects of climate change, alteration of shapes and distribution is seen in the freshwater lake system, and in some cases, they might disappear. These are the attributes of the dynamics change in precipitation, evaporation, and run-off. Climate change promotes long-term increases in fish production by inducing the enhancement of the production rate of invertebrate prey logarithmically with increasing temperature. The increasing rates are 2–4 times for each 10°C increase in temperature. But on the other hand, climate change will result in a change in prey-species composition. This change may cause antagonistic effects on the long-term enhancement of fish production. In short-time, climate change will cause a decrease in fish production because of timing mismatch. The ability of the movement of the freshwater species is vital in determining the resistance of those species to withstand climate change.”

Read more: Effect of Climate Change on Aquatic Ecosystem and Production of Fisheries


Aquatic animals are now in big danger due to direct human activities, such as fishing, whaling, and indirect human activities, such as plastic pollution, climate change, global warming. There is an urgent need to save our oceans and aquatic life because “If the Ocean Dies, We Die.”

There are so many ways to prevent climate change, one of the most effective is to speak up, to raise awareness, to let as many as possible people know about the necessity to prevent the changes in our climate and how this affects the entire ecosystem. It is also important to recycle, to reduce waste, and, the most accessible thing that one can do is to change one’s lifestyle and go vegan not to contribute to the industry of agriculture that causes climate change in the most way.

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