Stanford University, California

A palaeoceanographer worries not about corals, but about coral reefs.

To understand what the consequences of human-induced CO2 increases might be, I study how atmospheric CO2 concentrations fluctuated in the past.

One outcome of high atmospheric CO2 that is inevitable is ocean acidification. Atmospheric CO2 dissolves in sea water, lowering the pH of the ocean’s surface layer.

We expect this to create problems for marine creatures that precipitate their skeletons from calcium carbonate, because the mineral dissolves in acid. Some researchers have suggested that scleractinian corals might even be driven to extinction.

But what does the geological record tell us? Corals’ reef-building fossils have appeared and disappeared over the past 200 million years and despite periods of elevated atmospheric CO2, the organisms did not go extinct.

A recent experiment (M. Fine & D. Tchernov Science 315, 1811; 2007) resolves this apparent paradox. The team grew scleractinian corals for a year in sea water with a lower-than-normal pH. They found that the corals reproduced and grew happily in this acidic environment — albeit without their hard skeletons. The corals adjusted their skeleton-forming physiology in response to the different growing conditions.

So corals seem to be quite adaptable. But I would like to know whether other calcifying organisms have such physiological versatility.

Moreover, we have to remember that although corals may survive in an ocean with a lower pH as sea-anemone-like organisms, they are currently major contributors to the intricate physical structure of coral reefs. What will be the future of these ecosystems if their calcium-carbonate scaffolding disappears? Will our grandchildren enjoy the spectacular beauty of these ‘rainforests’ of the ocean?

College of William and Mary, Gloucester Point, Virginia, USA

A marine scientist marvels at connections between the cold war and slimy mudflat worms.

Having grown up on the coast of New England, my childhood involved a good deal of digging around in the intertidal mud, unearthing things that most people of good sense do their best to avoid — things such as slimy, slithering worms, which often bite or smell bad, or both.

Older but no wiser, I was delighted to come across a recent paper (E. Teuten et al. Mar. Ecol. Prog. Ser. 324, 167–172; 2006) that has cleverly extracted a surprising scientific result from studies of such mudflat worms.

As well as reminding me of my dubious childhood pastime, the work recalls the period in which I grew up, during the cold war, when much of the world lived in fear of the nuclear weapons then being tested. This work takes advantage of one legacy of those tests.

The bomb tests sent into the atmosphere lots of the isotope carbon-14, normally present only at low levels. This bomb carbon-14 subsequently made its way into the oceans, where it became incorporated into plankton. The plankton in turn sank and became part of the coastal mud, providing a home and a food source for marine sedimentary animals.

Mudflat worms are generally believed to ingest wholesale the nondescript sediment in which they live, yet the worms examined in this study contained more bomb carbon-14 than the sediment surrounding them.

Thus, it seems that the worms assimilate from the amorphous goop, material that has been deposited since the cold war and so is younger than the average age of the sediment. Presumably, they do so because the newer material is more nutritious, but how they extract it is unknown.

Makes me want to get back out by the sea with my bucket.

University of British Columbia, Vancouver, Canada

A marine biologist dives into the history of the Gulf of California.

A decade ago, I coined the term ‘shifting baselines’ to describe how society perceives environmental change. The concept has caught on: there’s even a website, at https://www.shiftingbaseline.com, featuring short, explanatory films.

The films push the idea that the standards by which society assesses change are themselves changing. We tend to use the state of affairs that prevailed when we first became aware of an issue as our reference point for evaluating future change — a baseline that shifts with each generation.

A set of three brilliant papers illustrates how this can shape our understanding of ecosystems.

The most recent paper (A. Sáenz-Arroyo et al. Fish Fish. 7, 128–146; 2006) reconstructs from historical sources, such as pirates’ logs, details of the Gulf of California’s ecosystem stretching back to the sixteenth century. The researchers argue that the past abundance of creatures such as marine mammals, turtles and oysters recounted in these sources should be considered when setting conservation targets today.

Their previous work examined records of Gulf groupers, fish that once dominated the area’s reefs (A. Sáenz-Arroyo et al. Fish Fish. 6, 121–133; 2005), concluding that fishery statistics didn’t go back far enough to accurately map the species’ decline.

Further, they quizzed three generations of artisanal fishers (A. Sáenz-Arroyo et al. Proc. R. Soc. Lond. B 272, 1957-1962; 2005), and found that fishers’ knowledge of the location or habits of species disappeared within one generation, if the species became rare.

We are all affected by this kind of collective amnesia. It allows us to handle change. But it is also the reason why we accept losses that would be intolerable, were we aware of them.