Climate change could lead to marine food shortage, posing a serious threat to sea life

As the world continues to battle climate change and its disastrous consequences, a group of Australian researchers have demonstrated how global warming is on track to ruin marine food chains, ultimately affecting life which thrives under water.

In a new study, published in the journal PLOS Biology, the researchers have shown that warming oceans and rising levels of dissolved carbon dioxide can affect the transfer of 'energy' from the lowest to the highest member of marine food chains, leading to a decrease in the availability of food for different species.

The team posited this scenario after simulating adverse underwater conditions in 12 tanks of 1,600 litre capacity for a period of six months.

They populated the artificial ecosystem with a range of species, including algae, shrimp, sponges, snails and fishes, and created adverse conditions by raising water temperatures by 2.8° Celsius and maintaining water acidity with elevated CO2 levels.

The survival, growth, biomass and productivity of all animals and plants in this ecosystem helped researchers create sophisticated food models which revealed the disturbance in the flow of energy.

The results revealed higher temperatures disturbed transfer of energy from plants to grazers (herbivores), while a combination of high temperatures and CO2 levels affected the energy flow of both – from plants to grazers and then from grazers to predators.

This was mainly caused due to the fact that warmer water triggered the growth of inedible blue-green algae at the expense of plants which are crucial for marine food webs. "This increased primary productivity does not support food webs because these cyanobacteria [blue-green algae] are largely unpalatable and they are not consumed by herbivores."

Ultimately, this would mean that, under the effect of drastic climate change, the population of plant-eaters would decline due to the lack of energy and, in turn, predators sitting on top would also have nothing to eat. This would obviously have a serious impact on a range of species which thrive underwater.

"Healthy food webs are important for maintenance of species diversity and provide a source of income and food for millions of people worldwide," said the study's lead author Hadayet Ullah. "Therefore, it is important to understand how climate change is altering marine food webs in the near future."

Though the study highlights the plausible risk to water-dwelling plants and animals, the researchers believe the work should continue on a larger scale to provide scientists more insights into the effects of climate change on marine life and ways to deal with it.

Project leader Professor Ivan Nagelkerken said, "If we are to adequately forecast the impacts of climate change on ocean food webs and fisheries productivity, we need more complex and realistic approaches, such as large mesocosms that provide more reliable data for sophisticated food web models."