How are some of the tiniest creatures changing their habitats? 

In middle school, you probably learned about the significant role animals play in keeping the ecosystem balanced. For instance, beavers contribute by building dams; this helps retain water and reduces the incidence of flooding downstream. Similarly, fish release nutrient-rich excretions into the ocean that aid in the growth of underwater vegetation, such as seagrass and algae.  

But does every creature have a positive effect on the environment? What if some creatures harm their environments instead? You may be surprised to know that such creatures do, in fact, exist—not only do they negatively impact their environments but also permanently modify them. Let’s explore two such tiny organisms that have proven to be detrimental to their habitats.   

Signal crayfish burrow river banks 
Signal crayfish are freshwater crustaceans that resemble lobsters. In the 1970s, they primarily served as sources of human food in the United Kingdom (UK). Presently, they’re widespread across Europe. But what distinguishes them from other freshwater species? Scientists have found evidence that they’re negatively affecting their habitat. And how do they do this? For starters, they feed on aquatic plants, some of which are already endangered, thus, further depleting their numbers. Additionally, due to their highly competitive nature, they eliminate their own relatives, such as white-clawed crayfish by feeding on them.    

And that’s not all. They’re also greatly affecting rivers by burrowing unnecessary banks. In the UK alone, they have burrowed into clay banks causing several bank failures. This, in turn, has led to the collapse of nearby infrastructures. Accumulation of clay in water-bodies has also led to large-scale clogging, making it difficult for fish and other aquatic species to survive. The Prior Park Landscape Gardens in Bath, England, serves as the most powerful example of the damage caused by signal crayfish; they burrowed into earth dams there and the repairs cost millions of pounds.  

Mussels glue themselves to nearby objects 
Mussels are generally known to benefit their habitat as they filter their resident water-bodies by getting rid of sediment and organic detritus. In fact, native freshwater mussels also play a vital role in multiplying the populations of their fellow aquatic invertebrates. But not all mussel species are the same. There are certain invasive mussels that are actually endangering instead of replenishing their habitat.  

For example, zebra mussels that are native to Russia and Ukraine, are known to choke up underwater pipes with gravel. They’re doing even more damage after migrating to countries, such as Canada and the UK. Specifically, they have caused many multinational companies tremendous losses worth $18 million annually. And believe it or not, their larger cousins, quagga mussels, are even more dangerous! They have the ability to attach themselves to anything in sight, be it river gravel, other mussels or even each other. When this type of attachment happens, a dense mass is formed which solidifies the riverbed, putting all the other aquatic organisms at risk.