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Monday, 26 October 2015 10:35

Oceans on the Brink: New Report Predicts Food Chain Collapse Featured

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Bleached coral coloy, no fish Bleached coral coloy, no fish ead72/Fotolia

Our oceans contain anywhere from half to 80 percent of all life on our planet, but changes brought on by a variety of factors could impact that immensely within this century. A journal published this past week, Proceedings of the National Academy of Sciences, contained a peer-reviewed report that warned of the potential collapse of the food chain within Earth’s waters. The report was a meta-analysis of 632 published studies that gave a dire view of the future of many marine ecosystems.

"We know relatively little about how climate change will affect the marine environment," says Professor Sean D. Connell, from the University of Adelaide and one of the authors of the report. "Until now, there has been almost total reliance on qualitative reviews and perspectives of potential global change. Where quantitative assessments exist, they typically focus on single stressors, single ecosystems or single species. This analysis combines the results of all these experiments to study the combined effects of multiple stressors on whole communities, including species interactions and different measures of responses to climate change."

Significant factors that include the acidification of our waters as well as climate change could lead to die-offs in habitats ranging from the open ocean to kelp forests to seagrass beds, as well other diverse concentrations of oceanic life. The leading cause of this cataclysm will be the increasing carbon dioxide rates in our waters, which many species will have a great deal of difficulty adapting to, if they are able to adapt at all. This will lead to plummeting diversity, with carnivorous species at the top of the food chain being the hardest impacted by the narrower range of species hanging on in these precipitous environments.

Increases in Carbon Dioxide within our atmosphere will cause seawater to become a corrosive to the shells of many organisms beneath the waves. Acidification will also heavily impact the survival rates of coral, the central organism on which reefs are dependent. Reefs are an incredibly important part of the various oceans overall ecosystems, and support around a quarter of all marine life according to the National Oceanic and Atmospheric Administration (NOAA).

"With higher metabolic rates in the warmer water, and therefore a greater demand for food, there is a mismatch with less food available for carnivores -- the bigger fish that fisheries industries are based around," Associate Professor Ivan Nagelkerken, also from the University of Adelaide, said. Nagelkerken was the other author of the report, along with Connell. "There will be a species collapse from the top of the food chain down."

While not all marine life will be negatively affected by the CO2 increase, that should not bring much comfort to observers. Life lower on the food chain, such as algae and plankton, could see their numbers increase in these new environs, but the report predicts that their success will not translate to those species that feed upon them as acidification will decrease their productivity.

"This 'simplification' of our oceans will have profound consequences for our current way of life, particularly for coastal populations and those that rely on oceans for food and trade," Nagelkerken said.

Profound could be underselling it. Nearly half the people on the planet depend of fish as a primary source of protein, and fisheries and similar industries provide a means of living for over 10 percent of the people on Earth. The Living Blue Planet report published by the WWF earlier this year, and covered by a Sun Bay article in a previous issue, already warned of the impacts of overfishing by a rapidly growing population. The report published the startling finding the there was a 52 percent decline in the species of fish, reptiles, amphibians, and birds that call the ocean their home between the years of 1970 and 2010. That report also noted that half the world’s coral and seagrass have been lost due to a multitude of factors.

“When we look at the fish species most directly tied to human well-being – the fish that constitute up to 60 per cent of protein intake in coastal countries, supporting millions of small-scale fishers as well as a global multibillion-dollar industry – we see populations in a nosedive,” Marco Lambertini, Director General of WWF International, said in the WWF report. “The habitats they depend on, such as coral reefs, mangroves and seagrasses, are equally threatened.”

“The pace of change in the ocean tells us there’s no time to waste,” Lambertini said. “These changes are happening in our lifetime. We can and we must correct course now.”

The pressure that humans are placing on the oceans will only grow larger over the next half century, as many predict that our global population will reach 10 to 11 billion people by the year 2050. Earth’s population just reached 7 billion roughly two years ago, around Halloween of 2013. That itself was a stark increase from the 1.5 billion people inhabiting Earth at the beginning of the twentieth century.

The significant and rapid increase in population will mean greater pressure on fisheries, and well as increased pollution affecting our coasts, around which a significant percentage of humanity have settled. It’s estimated that nearly 60 percent of all humans live within one hundred kilometers of a coast.

In addition to the predicted effects of the increase of CO2 in the water, increased human activity such as agriculture, coastal tourism, increased sea traffic, and unsustainable fishing practices will put additional pressures on the various ecosystems of our oceans. Runoff from both sewage and agriculture are thought to be responsible for nearly 500 dead zones globally, covering almost 245 square kilometers of ocean. Dead zones are areas of water so oxygen-deprived from excessive nutrients introduced into the water that marine life is unable to survive in them.

By Trent Townsend

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