Scientists are increasingly stating that the environmental issue which is changing the freshwater ecosystems of multiple continents, “lake browning”, will be resulting in larger effects on fish populations than what has been expected so far. The new studies show that the countries of North America and Europe, as well as other parts of the world with freshwater, are experiencing changes in water, food webs, and fish communities due to increasing levels of organic matter in lakes.
Lake browning is the event of lakes and rivers becoming darker in color due to the washing in of organic materials like rotting vegetation and soil particles. Researchers have noticed that over the past few decades, browning has been increasing at a number of water bodies. Among the factors believed to be causing this trend are global warming, changing rainfall patterns, land-use practices, and shifts in ecosystem dynamics.
Great efforts have been made to learn more about the impact these changes have on the aquatic world. Freshwater ecosystems offer the greatest biological variety on the planet. They support not only fish but plants, insects, and microorganisms too. Slight variations in water quality can have a series of effects that spread to the food chain.
Mostly, the researchers’ observations reveal that browning of the water is capable of changing fish communities dramatically, simply because fish rely on sunlight. With clear lakes, the sun can reach deeper so the water plants can grow and conditions for fish are good. When the water is tinted, the sun goes in less and the habitats are altered, and fish food.
The study revealed that fish species can be categorized into those which are unable to adjust to the modified habitats and those who may benefit from it. Predators who hunt the prey through sight usually have a harder time in clear water so they will be the ones to lose mostly in the situation of dark water. Their food may be hidden from them – less food, less growth, less mating, and eventually, less survival.
Meanwhile, fish that do not rely upon sight so much, or who are naturally good in dim light, can be the ones that will win. These changes can slowly shift the culture in fish species and indicate which species will be the ruling one in different aquatic territories. Eventually, the changes can be manifested in the biodiversity and the ecosystem and the way it functions.
The consequences cover more than just the fish that are on their own. Change in the color of the water can also lead to drastic change of the food web by affecting the primary producers of the aquatic systems: plankton, aquatic plants, and invertebrates. A change of any of these populations will lead to changes in the food chain, and even the very top predators will be influenced.
Among the most significant reasons for the increase in lake browning is the existence of climate change. The warming of the globe will cause more extreme weather events, changes in precipitation patterns will also allow for more of the organic materials to be transported from the surrounding landscapes to the lakes and rivers. Heavier rainfall in some regions has already been observed to carry larger amounts of vegetation and soil into freshwater systems, thereby exacerbating the browning process.
Given the great threats to these ecosystems, Mostly the rivers and lakes – ones that supply us with water, food, and economic benefits – the scientists are quite worried. Besides lake browning, which is known to a lesser extent, these ecosystems suffer from pollution, the loss of their natural habitats, invasive species, and the effects of warming, to list a few. Protecting aquatic biodiversity and sustaining healthy fisheries have always been complex goals, but lake browning is adding to that complexity.