We are all well aware the catastrophic effects of climate change in our oceans. The consequences of rising carbon dioxide in salt water, agitating marine life and ecosystem is well documented. But now researchers have indicated that similar things are happening in freshwater too. The small water flea, Daphnia falls in the middle of this.

pCO2-Dependent Freshwater Acidification

pCO2 is the partial pressure of carbon dioxide. It gives a measure of carbon dioxide exchange between the lake and its environment.

With the rise of pCO2(partial pressure of carbon dioxide), the freshwater ecosystems are becoming more and more acidic. A study of four reservoirs in Germany revealed that there was a 0.3 decrease in pH level within 35 years, an indication that fresh water may be getting acidified at a much faster pace than the oceans.

The carbon dioxide in lakes may come from the atmosphere but the majority of the greenhouse gas enters through emissions settling in the soil and washing into freshwater.

The consequences are not just limited to the supply of acidified water at our homes. The freshwater food webs, nutrient cycles, and the whole biodiversity of freshwater is falling under threat.

CO2 Altering the Habitat of Daphnia, the Water Flea

A research team at Ruhr-University Bochum in Germany reporting in Current Biology studied the effect of rising acidity in the water on the behaviour of two species of water fleas, or pinhead-sized lake dwellers also called Daphnia.

The unheard tiny crustaceans are one of the essential and dominant species of many lakes, ponds, and reservoirs.

They are at the bottom of many food webs and act as a primary food source for many large animals like tadpoles, newts, and larvae of phantom midges. When they feed on Daphnia, the predators release a chemical signal that alarms various species of water fleas to defend themselves.

They respond by raising neck spikes, some grow giant “helmets” making themselves tougher to eat. But the rising level of carbon dioxide is altering their protective ways.

Daphnia fails to detect the predators under the high level of CO2 in the water. “High levels of CO2 reduce the Daphnia’s ability to detect their predator,” says Linda Weiss, one of the team member. “This reduces the expression of morphological defenses, rendering them more vulnerable.”

The vulnerability is likely to hit other freshwater communities with much worse consequences. The study is done on the four reservoirs and the team is curious to know the global degree of the phenomenon.

Image Credit: Wikimedia Commons, Naomi Tamar via Unsplash