Impact of Climate Change on Marine Food Webs

A new study has discovered that levels of commercial fish stocks could be harmed because rising sea temperatures affect their source of food.

Reduced energy flow means that the amount of food available for predators – such as fishes – at the top of food webs is reduced, with potential consequences for fisheries species. (Photo Credit: Lance Anderson, Unsplash)

Scientists from the University of Adelaide have now established how climate change can drive the downfall of marine “food webs”.

Featured in the open access journal PLOS Biology, the study’s key author PhD student Hadayet Ullah, alongside Professor Ivan Nagelkerken and Associate Professor Damien Fordham of the University’s Environment Institute, demonstrates that increased temperatures decrease the main flow of energy from the key food producers at the bottom (for example, algae), to transitional consumers (herbivores), to predators at the top of marine food webs.

Such disturbances occurring in energy transfer can possibly result in a decrease in the availability of food for top predators, which in turn, can cause negative impacts for a number of marine species within these food webs.

Healthy food webs are important for maintenance of species diversity and provide a source of income and food for millions of people worldwide. Therefore, it is important to understand how climate change is altering marine food webs in the near future.

Hadayet Ullah, Key Author

Twelve large 1,600 liter tanks were built in order to mimic predicted conditions of elevated ocean temperature and acidity brought about by increasing human greenhouse gas emissions. The tanks harbored a variety of species including shrimp, sponges, algae, fishes, and snails.

For six months, the mini-food web was maintained under future climate conditions, and during this time the researchers succeeded in measuring the survival, biomass, growth, and productivity of all plants and animals, and then used these measurements in a refined food web model.

“Whilst climate change increased the productivity of plants, this was mainly due to an expansion of cyanobacteria (small blue-green algae),” said Mr Ullah. “This increased primary productivity does not support food webs, however, because these cyanobacteria are largely unpalatable and they are not consumed by herbivores.”

Comprehending how ecosystems exist under the effects of global warming is considered to be a challenge in ecological research. Most research on ocean warming deals with short-term, simplified experiments based on just one or a few species.

“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, that provide more reliable data for sophisticated food web models,” said project leader Professor Nagelkerken.

Marine ecosystems are even now experiencing great impacts from global warming, thus enabling it to be important for improving the understanding of how these results can be extrapolated to ecosystems all over the world.

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