World Oceans Day

Tomorrow is World Oceans Day, but today you can get a live stream from the Great Barrier Reef. Expert marine biologists are apparently on hand (I can't load the website) to answer your questions and you can even talk to SCUBA divers on the Reef. Check you social media too because it'll be on Twitter, G+ and YouTube.

My favourite science books

I've been talking to a few people recently about good science books. My favorite books that deal with similar topics to this blog are in descending order:

Mapping the deep - Robert Kunzig

The World without us - Alan Weisman

The wavewatcher's companion - Gavin Pretor-Pinney

Trilobite - Richard Fortey

At the water's edge - Carl Zimmer

Books outside the topic area of this blog that I found to be excellent are:

The demon-haunted world - Carl Sagan
The elegant universe - Brian Breene
Chaos - James Gleick

Neil Shubin's "Your inner fish" is sitting on my bookshelf just waiting to be read. I hear it is very good and will probably make it onto my list. Several books by Dawkins and Gould are also among my favorites, but I liked them less than the ones above. The ancestor's tale (Dawkins) and Wonderful life (Gould) are probably the best I've read of their books.

Attack of the jellyfish swarm

Jellyfish are not as charismatic as some marine species and consequently they have not received much research attention. Recently though, there has been increasing interest in them because their numbers appear to be on the rise worldwide. There are a few hypotheses about why this might be the case floating around in the literature.

The beautiful and under appreciated jellyfish, Cyanea capillata. Perhaps the World's biggest (photo Wikipedia).

Corals, which are in the same phylum (Cnidaria) as jellyfish, have been on the decline in northern Australia and other parts of the world. Two major hypotheses have been proposed to explain this; overfishing reducing herbivorous fish numbers leading to algal overgrowth and agricultural runoff decreasing water clarity through sedimentation and by promoting phytoplankton growth. These same pressures are thought to have a positive effect on jellyfish populations.

Overfishing is argued to increase jellyfish numbers by reducing predation and competition for food, particularly of young jellyfish. While agricultural runoff stimulates phytoplankton blooms that directly or indirectly provide increased amounts of food to jellyfish. Some others argue that changes to marine communities that are occurring as a result of climate change are tipping the ecological balance in favour of jellyfish. But there isn't much agreement, even among experts, about whether jellyfish have actually increased globally.

Nomura jellyfish, Nemopilema nomurai, causing problems for Japanese fishermen (Photo Shin-ichi Uye)

Recently, a collaboration of scientists from around the world have conducted one of the most comprehensive and rigorous analyses of the available data on jellyfish numbers. Condon et al. found that jellyfish numbers go through cyclical population booms roughly every 20 years. Their data suggest that increasing jellyfish numbers in the last few years are simply a part of this 20-year population oscillation. But, there is a hint in the data that since 1970 jellyfish numbers have be increasing.

During the last population minimum, which occurred in 1993, jellyfish numbers were higher relative to previous population minimums. This resulted in a weak, but statistically significant trend towards increasing jellyfish abundance in the last 40 years. The authors caution that the trend is too weak, given the limitations of the data set, to conclude that jellyfish populations really are on the increase. Data collected in the next few years should be able to determine, with confidence, whether the upwards trend is real.

Although they found no strong evidence that jellyfish numbers are increasing worldwide, there was good evidence that numbers are increasing in some regions. These regions included the Sea of Japan, North Atlantic shelf regions, the Barents Sea, and parts of the Mediterranean Sea. All of these regions exhibited the 20 year oscillation, but local factors seem to have acted in concert with the global population fluctuations. Notably, fishing is heavy in many, if not all, of those regions.

 

Condon, R., Duarte, C., Pitt, K., Robinson, K., Lucas, C., Sutherland, K., Mianzan, H., Bogeberg, M., Purcell, J., Decker, M., Uye, S., Madin, L., Brodeur, R., Haddock, S., Malej, A., Parry, G., Eriksen, E., Quinones, J., Acha, M., Harvey, M., Arthur, J., & Graham, W. (2013). Recurrent jellyfish blooms are a consequence of global oscillations Proceedings of the National Academy of Sciences, 110 (3), 1000-1005 DOI: 10.1073/pnas.1210920110

Evolution, climate change and coral

Increased carbon dioxide in the atmosphere poses several problems for organisms living in the marine environment. Increases in temperature and ocean acidification are the two best known and most worrying. In order to predict how climate change and ocean acidification will affect marine species, we need to know how they respond to these conditions. The effect of climate change on corals has attracted a lot of attention because of their importance for biodiversity.

We can't just expose corals to predicted conditions because corals of the future won't be naive to these environments and are likely to have evolved. We know that evolution can be extremely rapid, often within decades. Ignoring the potential for evolution to influence the effects of climate change on marine organisms could lead to inaccurate projections of the effects of climate change on extinction risk. Yet many authors are ignoring the effects of evolution and acclimation in making their predictions. 

The three-spine stickleback, Gasterosteus aculeatus has been documented adapting to freshwater conditions from saltwater ancestors in just 13 generations (photo Wikipedia)

In their 2007 paper, Hoegh-Guldberg, et al. dismiss the importance of evolution because "reef-building corals have relatively long generation times and low genetic diversity, making for slow rates of adaptation". But, long generation times are not present in all coral species and the response of corals to climate change is going to depend partly on their algal symbionts, which have short generation times. 

Unfortunately, the rates of evolution in corals and their symbionts are extremely poorly known. In terrestrial systems though, genetic variation for traits related to thermal performance is common and evolutionary responses to changing climate are typical. For instance, changes in allele frequencies consistent with responses to global warming have been documented in a number of insects, such as fruit flies and mosquitoes (e.g. Bradshaw & Holzapfel 2001, Umina et al. 2005).

Acclimation, or phenotypic plasticity, will also affect the way that corals respond to climate change. Plastic responses to the environment can occur within generations and across them. For instance, Donelson et al. (2011) looked at the tropical damselfish, Acanthochromis polyacanthus, and found that their offspring could completely compensate for the negative effects of higher temperatures. But, this only occurred when both they and their parents where reared at the same temperature.

The tropical damselfish, Acanthochromis polycanthus (photo Wikipedia)

There are indications that some acclimation is occurring in corals too. Under stress, corals expel their algal symbionts, which gives them the appearance of having been bleached. Coral reefs that experience greater variability in sea surface temperature and those that have recently been subjected to bleaching are less susceptible to bleaching. This greater resilience suggests that some acclimation to climate change is possible within short time-frames. 

A bleached coral in the foreground with an unbleached coral of the same species behind (photo Wikipedia)

We need a better understanding of how evolution and acclimation may influence the response of corals to climate change so that our predictions are accurate. But, we already know which direction things are probably going to go. John Pandolfi's work has shown that under historical climate change, diversity on corals reefs has declined and populations have moved to higher latitudes (e.g. Pandolfi et al. 2011, Kiessling et al 2012). 

Climate change is currently more rapid than previous episodes and this will limit the amount of adaptation that can occur. Corals are also already under significant pressure from other anthropogenic sources of stress that have resulted in substantial declines and changes in population composition. These pressures, too, will decrease the ability of corals to cope with the effects of climate change. By removing these pressures, we will give corals the best chance possible to adapt to a warmer and more acidic ocean.

Hoegh-Guldberg, O., Mumby, P., Hooten, A., Steneck, R., Greenfield, P., Gomez, E., Harvell, C., Sale, P., Edwards, A., Caldeira, K., Knowlton, N., Eakin, C., Iglesias-Prieto, R., Muthiga, N., Bradbury, R., Dubi, A., & Hatziolos, M. (2007). Coral Reefs Under Rapid Climate Change and Ocean Acidification Science, 318 (5857), 1737-1742 DOI: 10.1126/science.1152509  

Bradshaw, W., & Holzapfel, C. (2001). Genetic shift in photoperiodic response correlated with global warming Proceedings of the National Academy of Sciences, 98 (25), 14509-14511 DOI: 10.1073/pnas.241391498

Umina, P., Weeks, A. R., Kearney, M. R., McKechnie, S. W., & Hoffmann, A. A. (2005). A Rapid Shift in a Classic Clinal Pattern in Drosophila Reflecting Climate Change Science, 308 (5722), 691-693 DOI: 10.1126/science.1109523

Donelson, J., Munday, P., McCormick, M., & Nilsson, G. (2011). Acclimation to predicted ocean warming through developmental plasticity in a tropical reef fish Global Change Biology, 17 (4), 1712-1719 DOI: 10.1111/j.1365-2486.2010.02339.x

Pandolfi, J., Connolly, S., Marshall, D., & Cohen, A. (2011). Projecting Coral Reef Futures Under Global Warming and Ocean Acidification Science, 333 (6041), 418-422 DOI: 10.1126/science.1204794 

Kiessling, W., Simpson, C., Beck, B., Mewis, H., & Pandolfi, J. (2012). Equatorial decline of reef corals during the last Pleistocene interglacial Proceedings of the National Academy of Sciences, 109 (52), 21378-21383 DOI: 10.1073/pnas.1214037110

It's currently complicated

A few weeks ago I wrote about the problem of plastic in the ocean. In that post I used a simple graphic showing the location and direction of rotation of the five oceanic gyres. On seeing that diagram you may have guessed that things were actually a little more complicated. Well, they are. Something that might have tipped you off was the swirls in the photos of plankton blooms I posted, here and here. If you want to get a sense of just how complex the ocean currents are, here is a great visualisation of a NASA ocean current model. This too, is a simplification.

An ocean of plastic

There are five major oceans in the world. There's the Arctic Ocean, the Atlantic Ocean, the Pacific Ocean, the Indian Ocean and the Southern Ocean. In the Pacific, the Atlantic and Indian oceans there are huge circular currents called gyres. The Indian Ocean has a single gyre, while the Atlantic and the Pacific have two, one in the northern hemisphere and one in the southern hemisphere.

The five great oceanic gyres showing the direction of rotation

The northern hemisphere gyres rotate in a clockwise direction, while the southern hemisphere gyres rotate in an anti-clockwise direction. The direction of rotation has to do with the Coriolis effect, which is what people joke about when the say that water goes down plug-holes in different directions in Europe compared to Australia. The Coriolis effect doesn't matter too much for water going down plug-holes (other forces are far more important), but operating over long time periods and over large distances it produces gyres.

Because the gyres rotate they are good at accumulating floating items in their centres. Waste material is drawn into the gyres from the countries that surround the gyre. When the waste reaches concentrations that are significantly higher than the rest of the World's oceans that area of ocean is termed a garbage patch. So far surveys have found garbage patches in the North Pacific, North Atlantic and Indian Ocean gyres. Garbage patches also form in other places, but the oceanic gyres form the biggest patches.

Of all the garbage patches the North Pacific gyre is the largest by a considerable margin. Mainland Australia has an area of 7.69 million square kilometres and estimates of the size of the North Pacific Garbage Patch are as high as 15 million square kilometres. So, basically there's a patch of garbage that could cover an area almost twice the size of Australia floating in the North Pacific. It should be noted, however, that other estimates are considerably smaller. Estimates vary largely because different studies use different densities of debris to define what a garbage patch is.

Plastic particles hanging underwater in the North Pacific garbage patch (photo Scripps Oceanography).

The garbage patches collect a huge array of debris and chemical waste. A lot of it, about 80%, comes from land-based sources. Natural disasters, such as a tsunami or a hurricane can lead to large amounts of waste entering the sea. However, the most common route is through storm water and waste water inputs. The other 20% of waste is lost or deliberately dumped from ships at sea. Although it has been illegal to dump waste at sea for the last 20 or so years, the law is almost impossible to enforce.

By far the most common thing found in the garbage patches is plastic. Mostly it's small particles of plastic, but sometimes very large items like fishing nets that are kilometers long can be found. The fact that it is mostly plastic is pretty amazing seeing as plastic has only become common since the Second World War. But the plastic is able to accumulate because, unlike many other type of rubbish that finds its way into the sea, there are very few organisms that can break it down.

A ghost net floating in the North Pacific garbage patch (photo Scripps Oceanography).

Plastic has a number of negative effects on marine animals. Probably the effect that most people would be familiar with is that large items of plastic, like ropes, fishing line and fishing nets can entangle marine animals. This can cause them to drown, if they breath air, it can inhibit their movements making them more vulnerable to predators and it can cause them injuries as they try to struggle free.

A beached whale's tail entangled with ropes (photo Mike Baird).

Another effect is that marine animals can consume the plastic because it looks to them like a tasty piece of food. At its most minor the animal has simply wasted its time and effort catching the plastic. But, if an animal eats enough plastic it can clog their digestive tracts making it hard for them to eat and digest real food. And it is not just the larger animals like whales, turtles and sea birds that are at risk from ingesting plastic. We know that there are some very small, even microscopic animals that are eating plastics.

Plastic bag fragments found in the contents of a turtle's stomach (photo Victoria González Carman).

Plastics have also been reported to accumulate toxic chemicals on their surface in high concentrations. And if marine animals eat the plastics the chemicals can be released during digestion and become incorporated into their tissues. So even if an animal eats plastic rarely, it can acquire a toxic dose of some chemicals that enter its system via the plastic. The research on toxic plastic is controversial and not yet widely accepted.

So plastic waste is a huge problem for life in the ocean. In fact, one researcher looking at plastics in the ocean has argued in a recent book that the biggest effect on the marine environment this century won't be climate change, it'll be plastic waste.

Phytoplankton from space

The plankton consists largely of small organisms such as bacteria, plants and animals that drift at the mercy of ocean currents. The phytoplankton is the component of the plankton that is able to photosynthesize and it therefore very important in marine food-webs as primary producers. Indeed, phytoplankton are important for almost all life on Earth as they carry out about half of all photosynthetic activity, and therefore produce much of the oxygen in the atmosphere.

Diatoms, one of the most numerically dominant types of phytoplankton. Other important groups include dinoflagellates, cyanobacteria and algae.

Phytoplankton are restricted to the surface water where sunlight can reach them. Their numbers there are limited by the availability of certain nutrients. When these nutrients become abundant, such as during the upwelling of water from the deep ocean, the phytoplankton numbers increase rapidly. Such events are called 'blooms' and can be large enough to be detected from space.

A false-colour image of a phytoplankton bloom in the South Atlantic Ocean taken by the Earth-observing satellite Envisat. The colours represent the density (shade) and types (colour) of phytoplankton present.

Different types of phytoplankton use different combinations of pigment for photosynthesis. Different pigments absorb different wavelengths of light and this allows satellites to make a coarse identification of the species of phytoplankton present in a bloom by detecting the reflected light. Using this information false-colour pictures of a bloom, such as the one above, can be constructed to identify when, where and what types of phytoplankton are blooming. This is important information that assists with our understanding of the effects of human impacts on the marine environment, such as pollution and climate change.

Like life on the deep seafloor, the diversity of species in the plankton presents a paradox. Phytoplankton exist in a seemingly uncomplicated environment and compete for a small number of limiting resources, a situation that should favour a limited set of species, yet there is a huge diversity. Perhaps small variations in the spatial and temporal availability of the resources and variations in temperature create the complex set of niches required to support high diversity, as they do in the deep.

This post was inspired by a post on Sandwalk. The image of the phytoplankton bloom can be found (and downloaded) on the European Space Agency website here.

Japanese incursion

Two days ago a Japanese vessel, the Yushin Maru No. 3, associated with the whaling fleet in the Southern Ocean sailed 8 nautical miles into Australia's Territorial Waters in pursuit of a Sea Shepherd vessel. The Yushin Maru No. 3 is a harpoon ship used for whale catching and is unwelcome in Australian Territorial Waters where whaling is illegal. Despite Australian Government protests to Japan the vessel stayed within Australian waters for more than 24 hours. Moreover, it stayed within Australian waters for several hours after it was said to be leaving. It continues the pugnacious approach that Japan has adopted in its dispute with Australia over its whaling activities in the Southern Ocean. 

The Yushin Maru No. 2, a harpoon vessel similar to the Yushin Maru No. 3

Although the vessel is now within Australian's Exclusive Economic Zone there is apparently little legal recourse for Australia as long as the vessel does not hunt whales. Australia has  claimed its Exclusive Economic Zone as a whale sanctuary. Under international law Australia should have the legal right to regulate fishing, including whaling, within this zone. But, Japan continues to hunt whales within the sanctuary under the guise of scientific research*. Finally, after much dithering by both major political parties, Australia launched legal proceedings against Japan over the whaling in the International Court of Justice. Australia submitted its case in May 2011 and Japan is due to make its submission in March this year.

Map of Antarctic territorial claims. Australia claims two territories (orange) which sandwich the French claim (dark blue). Norway claims the next largest territory (purple). New Zealand (green) also claims territory. The UK (red), Chile (yellow) and Argentina (light blue) have overlapping claims.

Any reduction in the area that Japanese can catch whales in as a result of Australia's action in the International Court for Justice is, unfortunately, unlikely to have a great effect on the supply of whale meat in Japan. Australia claims and exclusive economic zone in the waters off its Antarctic territory, but Japan and most of the rest of the world does not recognise this claim. Indeed, only four countries who also claim large exclusive economic zones in the Antarctic recognise Australia's claim. Japan is therefore likely to be able to continue whaling in these areas. Moreover, Iceland now exports whale meat to Japan, reportedly earning the country $US 17 million in the last four years. Like Japan, Iceland's whale hunt is conducted under the guise of scientific research. I guess they have a lot of collaborators in Japan...

The Japanese and Icelandic whale research programmes produce few, if any, valuable data on whales. Moreover, non-lethal research can be used to produce much of the same information. Scientific reviews of the research programmes conducted by the International Whaling Commission have found that experimental designs are shoddy, and that the information is either not required for management or obtainable by non-lethal means. That has not stopped either of the countries from whaling. Indeed, Japan has tried to use their data to argue that whale numbers are growing and need to be culled to preserve commercially important fish species. Of greater threat to Japan's commercially important fish stocks is certainly Japan's fishing fleets. I'll write more on that sometime.

*As Terry Pratchett and Neil Gaiman joke in Good Omens, the research is primarily concerned with determining how many whales can be caught during the whaling season.

Red Spot, Blue Dot

In September 1977 the Voyager 1 probe was launched. Its primary mission was to study Jupiter and Saturn, which it completed in late 1980. It took some fantastic photos of Jupiter, Saturn and their moons. Like this one of Jupiter's red-spot.

A decade after passing Saturn, Voyager 1 was beyond Pluto and headed for the edge of the Solar System, where it is now. At the request of Carl Sagan, Voyager 1 took this picture:

At first glance it's a boring image of black space with brown bands of sunlight reflecting off dust. But, it is actually an image that I find awe inspiring. If you look about halfway down the right-most band of brown, you'll see a tiny speck of pale-blue. That's Earth. In this image, which contains 640,000 pixels, Earth is little bigger than one tenth of a pixel. In the vastness of the universe our little planet is completely insignificant. But, Carl Sagan saw something in the image that was significant. In his book 'Pale Blue Dot' he wrote:

From this distant vantage point, the Earth might not seem of any particular interest. But for us, it's different. Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.

Earth appears pale-blue partly because of sunlight reflecting from the surface, which is mostly open ocean. The ocean absorbs more of the longer wavelengths of light (such as red) than it does the shorter wavelengths (such as blue), which is why large bodies of water appear blue. However, Rayleigh scattering of sunlight by the atmosphere, which is what makes the sky blue, also contributes to making Earth appear blue from space. If the Earth had no oceans, Rayleigh scattering alone would give it a blue tinge.