Guest essay by Eric Worrall

A new study published by Adelaide University, claims that ocean acidification and global warming will cause a major collapse of ocean food chains.

The abstract of the study (the fully study is paywalled);

Global alteration of ocean ecosystem functioning due to increasing human CO2 emissions

Ivan Nagelkerken1 and Sean D. Connell

Significance

People are not only concerned about climate change and its effects on plant and animal diversity but also about how humans are fundamentally changing the globe’s largest ecosystem that sustains economic revenue and food for many countries. We show that many species communities and ocean habitats will change from their current states. Ocean acidification and warming increase the potential for an overall simplification of ecosystem structure and function with reduced energy flow among trophic levels and little scope for species to acclimate. The future simplification of our oceans has profound consequences for our current way of life, particularly for coastal populations and those that rely on oceans for food and trade.

Abstract

Rising anthropogenic CO2 emissions are anticipated to drive change to ocean ecosystems, but a conceptualization of biological change derived from quantitative analyses is lacking. Derived from multiple ecosystems and latitudes, our metaanalysis of 632 published experiments quantified the direction and magnitude of ecological change resulting from ocean acidification and warming to conceptualize broadly based change. Primary production by temperate noncalcifying plankton increases with elevated temperature and CO2, whereas tropical plankton decreases productivity because of acidification. Temperature increases consumption by and metabolic rates of herbivores, but this response does not translate into greater secondary production, which instead decreases with acidification in calcifying and noncalcifying species. This effect creates a mismatch with carnivores whose metabolic and foraging costs increase with temperature. Species diversity and abundances of tropical as well as temperate species decline with acidification, with shifts favoring novel community compositions dominated by noncalcifiers and microorganisms. Both warming and acidification instigate reduced calcification in tropical and temperate reef-building species. Acidification leads to a decline in dimethylsulfide production by ocean plankton, which as a climate gas, contributes to cloud formation and maintenance of the Earth’s heat budget. Analysis of responses in short- and long-term experiments and of studies at natural CO2 vents reveals little evidence of acclimation to acidification or temperature changes, except for microbes. This conceptualization of change across whole communities and their trophic linkages forecast a reduction in diversity and abundances of various key species that underpin current functioning of marine ecosystems.

Read more: http://www.pnas.org/content/early/2015/10/06/1510856112.abstract?sid=90ebddb6-a731-4a13-99c1-eb94a2cf5bdc

The obvious question – why didn’t this hypothesised collapse occur during previous epochs with high CO2 levels, such as the Cretaceous Age? According to Wikipedia, the Cretaceous age enjoyed CO2 levels of around 1700ppm. Yet the Cretaceous was also the age of the Dinosaurs – the period was characterised by large tropical jungles, shallow warm seas, and a vast abundance of life, both marine and terrestrial. I suggest it takes a pretty robust food chain to support a predator like the Tyrannosaurus Rex.

Regarding the alleged impact of acidification on calcifying species like corals, it seems a shame the Adelaide boffins didn’t compare notes with their colleagues down the road in Perth, who recently discovered that corals have the ability to manage their internal pH levels – they grow just fine in a wide range of naturally occurring CO2 levels. Or the recent Woods hole study, which demonstrated coral reefs have astonishing resilience and ability to thrive, even in the most extreme conditions.

As for the direct effect of warming – even if warming occurs, the net result in most cases would surely be a slight shift in geographic habitat. For example, the range of temperatures on offer as you travel along say the Australian East Coast far exceeds temperature changes most alarmists predict will occur in the next century, due to global warming.