Pirate's Cove

A few fish died, hence, entire coastal food webs could collapse (via Eric Worrall at Watts Up With That?) (Any bold is what Eric did)

Climate change could drive coastal food webs to collapse

Coastal marine food webs could be in danger of collapse as a result of rising carbon dioxide levels, according to our new research. The study shows that although species such as algae will receive a boost, the positive effects are likely to be cancelled out by the increased stress to species further up the food chain such as predatory fish.

We used a self-contained ecosystem in a 2,000-litre tank to study the effects of warming and ocean acidification on a coastal food web. This approach can give us a good idea of what might happen to genuine coastal food webs, because the tank (called a “mesocosm”) contains natural habitats and a range of species that interact with one another, just as they do in the wild.

Our food web had three levels: primary producers (algae), herbivores (invertebrates), and predators (fish).

The results show that carbon dioxide enrichment can actually boost food webs from the bottom up through increased algal growth. This benefited herbivores because of the higher abundance of food, and in turn boosted the very top of the food web, where fish grew faster.

But while this effect of ocean acidification may be seen as positive for marine ecosystems, it mainly benefits “weedy” species – a definition that can be applied to some species of algae, invertebrates, and even fish.

In contrast, habitat-forming species such as kelp forests and coral reefs are more likely to disappear with rising COâ‚‚ emissions, and with them many associated species that are deprived of their habitats and food.

Our results therefore showed that warming had a detrimental overall effect on the coastal food web we studied. Although higher temperatures boosted algal growth, herbivorous populations did not expand. Because herbivore abundances remained similar and elevated temperatures result in a higher metabolic demand, predatory fish consumed more herbivorous prey, resulting in a collapse of these prey populations.

So, utter doom. Because of a bit of research with a fish tank. As Eric notes

Unfortunately the full study is paywalled, but attempting to infer global consequences of increased CO2 from a toy eco-system in a 2000 litre fish tank is absurd.

On the positive side, the researchers performed an actual experiment, rather than just running a computer model.

But anyone who has ever kept fish knows how difficult it can be to keep a fish tank eco-system stable. Fish in a tank are subject to numerous stresses, even a small mistake with feeding, water contamination or filtering waste can lead to disease and death.

2,000 liters is 528 gallons. If you’ve ever watched the Animal Planet show Tanked, many of those (very expensive) tanks are around that size, some bigger. And they take a lot of maintenance to keep in good working shape. Just keeping a small freshwater tank going can be work. I’m looking at my 20 gallon and I can see it needs some more water, about a gallon, and the light hood needs cleaning. I use a few liquids to reduce the stress of the fish. If something goes wrong, it can spread quickly and say goodbye to your fish. Saltwater is even more maintenance intensive.

The ocean ecosystem has survived numerous warm and cool periods. Corals survived when the temps and sea heights were much higher. This is all just typical scaremongering.