Persistent organic pollutants in animals in the deepest ocean trenches.

The presence of man-made chemicals is known to be a problem in a wide variety of environments, not just locations where Humans are present, but in remote areas such as the Arctic and High Himalayas. Such pollution in the world’s oceans is of particular concern, with visible concentrations of plastics on the ocean gyres and remote areas of the seafloor, and man-made chemicals, many with known ill-effect, recorded in a wide variety of marine organisms, including many species that form part of our own diet. The only areas where such pollutants have not been found are the deep ocean trenches that form in the subduction zones where one tectonic plate is pushed under another, though this is not evidence of actual absence, as these areas have not to date been sampled for such chemicals.

In a paper published in the journal Nature Ecology & Evolution on 13 February 2017, Alan Jamieson of the Oceanlab of the Institute of Biological and Environmental Sciences at the University of Aberdeen and the School of Marine Science and Technology at Newcastle University, Tamas Malkocs and Stuart Piertney of the Institute of Biological and Environmental Sciences at the University of Aberdeen, Toyonobu Fujii, also of the Oceanlab of the Institute of Biological and Environmental Sciences at the University of Aberdeen, and Zulin Zhang of Environmental and Biochemical Sciences at The James Hutton Institute, describe the results of a study that looked for two persistent organic pollutants in benthic Amphipod Crustaceans collected from the Mariana and Kermadec Trenches in the Pacific.

The Mariana Trench in the North Pacific is considered to be the deepest point in all the world’s oceans, and is a highly oligotrophic (low nutrient) environment, while the Kermadec Trench of the South Pacific is only slightly shallower and is more eutrophic (i.e. more nutrients are available). Amphipods were collected from both trenches using traps deployed by deep sea landers. Two species of Amphipods, Hirondellea dubia and Bathycallisoma schellenbergi, were collected from the Kermadec Trench at depths of between 7227 and 10 000 m, while a single species, Hirondellea gigas, was collected from the Mariana Trench at depths of between 7841 and 10 250 m.

 

Specimens of Hirondellea gigas, an Amphipod Crustacean from the Mariana Trench. Alan Jamieson.

These were tested for two persistent organic pollutants known to bioaccumulate in food chains, being absorbed by organisms close to the bottom and becoming more concentrated with each step up the chain. These were polychlorinated biphenyls (PCBs), which were used in the manufacture of electronic goods between the 1930s and 1970s, and polybrominated diphenyl ethers (PBDEs), which are used as flame retardants. Both are extremely hard to break down in natural environments, and have previously been recorded from coastal sediments, open ocean waters and the polar regions.

Both PCBs and PBDEs were present in the majority of samples from both locations. PCBs were found in Amphipods from the Mariana Trench at concentrations of 147.3-905 nanograms per gram, and in the Kermadec Trench at concentrations of 18.03-42.85 in the Kermadec, while PBDEs were present at concentrations of 5.82-28.93 in the Mariana Trench and 13.75-31.02 in the Kermadec Trench. There was no clear correlation between depth and pollutant concentration, though in both locations the highest chemical concentrations were found in Amphipods captured near the shallower end of the range, at 7841 m in the Mariana Trench and 7227 in the Kermadec Trench.

The PCB levels in the Mariana Trench were notably higher than those in the Kermadec, and indeed in comparison to samples from shallow and surface environments. Crabs from paddy fields on the Liaohe River, considered to be one of the most polluted in China, only have PCB levels about one fiftieth that seen in the Mariana Trench, while highly polluted coastal sediments from Guam, Japan and Australia had levels of 314, 240 and 160 nanograms per gram respectively.

This high concentration is remarkable, and requires explanation. Jamieson et al. consider a number of possibilities. Firstly the Mariana Trench is close to the highly polluted North Pacific Subtropical Gyre (also known as the ‘Great Pacific Garbage Patch’) a massive patch of plastic debris which partially overlies the trench. This can potentially lead to degraded plastic debris and plastic derived chemicals sinking directly into the Trench. Secondly the chemicals may be derived from carrion falls into the trench (a major source of food for benthic Amphipods) which have high levels of plastic-derived chemicals. However the consistently high PCB levels across the nutrient poor Mariana Trench make this seem unlikely. Thirdly it is possible that the species present in the Mariana Trench (Hirondellea gigas) is particularly prone to bioaccumulating PCBs due to some aspect of their physiology, though this would be surprising given the ecological similarity of the Mariana Amphipods to the Kermadec species, this also seems unlikely.

Instead Jamieson et al. suggest that high levels of PCBs may be accumulating in the Mariana Trench due to the topology of the Trench itself. The Trench is generally seen as an exceptionally deep structure, with the bottom remote from surface waters, and often depicted with a comparison to Mount Everest (which would not reach the sea surface if it sat in the Mariana Trench). However it is not as deep as part of the Mississippi River is wide, nor Manhattan Island is long, so the waters at the bottom of the Trench cannot be seen as truly separate from those at the surface. Studies made in the Japan Trench following the 2011 Fukushima Dia-ichi nuclear disaster suggested that particulate matter in the ocean sank at rates of 64–78 m per day, which would enable material derived from the North Pacific Subtropical Gyre to reach the deepest parts of the Mariana Trench in under 170 days. Such material settling on the seafloor of the ocean plains would be subject to further movement by deep ocean currents, eventually spreading more-or-less evenly across these vast areas, but chemicals sinking into the Mariana Trench would become concentrated, as the depth of the trench protects its contents from the ocean currents.

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The Penguins of Africa.

A single species of Penguin, Spheniscus demersus, or the Blackfooted Penguin, lives in Southern Africa today, though two species, Nucleornis insolitus and Inguza predemersus are known to have lived there in the Early Pliocene. It has generally been assumed that the modern Penguins are descendants of the fossil penguins, though since they are also clearly closely related to other Penguins of the genus Spheniscus, which live in South America and the Galapagos, it is difficult to say what the exact relationship is.

Issue 279 of the Proceedings Of The Royal Society B contains a paper by Daniel Ksepka of the Department of Marine, Earth and Atmospheric Sciences at North Carolina State University and the Department of Zoology at the University of Cape Town and Daniel Thomas of the Department of Paleontology at North Carolina Museum of Natural Sciences in which they describe the results of a thorough investigation into South Africa's Penguins and the conclusions derived from this.

Reconstruction of the Pliocene Penguin Inguza predemersus (right) with a modern Blackfooted Penguin (left) for scale. From Ksepska and Thomas (2012).

Ksepska and Thomas examined over 200 fossil Penguins from the Iziko South African Museum collections, and compared them to recent and fossil penguins from South Africa and elsewhere. The came to the conclusion that modern Blackfooted Penguins are closely related to the Chinstrap Penguins of South America and the Galapagos, but not closely related to either of the fossil Penguins, and certainly not descended from either. Nor are the two extinct forms closely related.

This means that Penguins have invaded Africa on at least three separate occasions, something that Ksepska and Thomas examined next. Penguins appear first in the fossil record of New Zealand, but by the end of the Eocene are widespread in Antarctia, Australia and South America. They do not appear in Africa until the Early Pliocene, 30 million years later, and have never reached Madagascar of the Northern Hemisphere.

The inability of Penguins to colonize the Northern Hemisphere is the easiest to explain. Currents around the equator tend to flow away from it; in the Northern Hemisphere to the north and in the Southern Hemisphere to the south. There are also strong thermoclines to cross; water forms 'streams' within the ocean (such as the Gulf Stream) dependent on temperature, things flow easily within these streams, but it is hard to cross from one to the other. Similarly Madagascar is separated from Africa by the strong Agulhas Current, which sweeps away from Madagascar.

Africa can be reached from South America by the South Atlantic Current and the Antarctic Circumpolar Current, but these currents have not always flowed on their current paths. Prior to the Pliocene Antarctica and South America were still connected together; the Antarctic Peninsula was attached to the tip of Patagonia. This stopped the flow of the Antarctic Current, and trapped Penguins in the South Pacific. After the continents broke apart the Penguins were free to colonize the South Atlantic and soon reached Africa.

Map of the South Atlantic showing the prevalent currents and fronts. Dots show the location of modern Blackfooted Penguin colonies, and open stars locations where fossil Penguins have been found. From Ksepska and Thomas (2012).

Next Ksepska and Thomas looked at the extinction of the Pliocene Penguins. It is of course impossible to state the exact causes of such extinctions with absolute confidence, but this does not stop scientists from attempting to come up with plausible scenarios. During the Early Pliocene the sea-level was about 90 m higher than it is now. At the end of the Early Pliocene it dropped sharply, due to the increasing glaciation of Antarctica; another consequence of the separation of South America and Antarctica, which enabled the developing Circumpolar Current to isolate the southern continent in its own climatic zone, and caused the temperature to plummet. Ksepska and Thomas theorize that the Pliocene African Penguins may have been dependent on offshore islands as breeding grounds, and that either the falling waters left them vulnerable to African predators that they were unable to cope with, or that fluctuating sea levels associated with the changing climate left them unable to find safe nesting sites.

See also Was Archaeopteryx black? A new fossil bird from the Palaeocene of Brazil, Giant Bird from the Cretaceous of Kazakhstan, New 'oldest bird' found in China and Birds on Sciency Thoughts YouTube.

New deep-sea hydrothermal vent ecosystem discovered in the Southern Ocean.

Deep-sea hydrothermal vents (or 'black smokers' are) areas where super-heated, mineral-rich water escape from fissures in the Earth's crust into deep ocean water. They typically occur on divergent plate margins (ocean ridges), where two tectonic plates are moving apart and new ocean crust is being formed, but have also been found at transform margins, where plates are moving past one-another (also volcanically active areas).

A hydrothermal vent on the boundary between the South Scotia and South Sandwich Plates. It gets the nickname 'Black Smoker' from the minerals in the water which turn it opaque. From Rogers et al. (2012) (see bellow).

In 1977 an ecosystem was discovered at a black smoker on the Galapagos Rift, dominated by tube worms which derived their energy not from the sun by photosynthesis, or eating plants that had derived it from the sun by photosynthesis, but by the action of chemotropic (literally 'chemical eating') bacteria within their bodies. This caused a considerable stir among biologists, as it was the first time an ecosystem had ever been discovered that was not dependent on the light of the sun for energy (deep-water and cave communities that had been discovered before were out of the light, but ultimately derived their energy from organisms in it, typically by eating the dead). In addition the environment was particularly strange and hostile seeming; lightless, at very high pressures and very, very hot. Water from hydrothermal vents typically has temperatures of several hundred °C, but is be to remain a liquid due to the very high pressure in the deep ocean.

The tube worms of the Galapagos Vents.

Since this time communities have been found at vents at a number of locations about the world. All have been dependent on chemotropic bacteria for sustenance, but a variety of organisms have been found hosting these bacteria, including mussels, worms, crabs and shrimps. In a paper published in the journal PLoS Biology on 3 January 2012, a team of scientists lead by Alex Rogers of the Department of Zoology at the University of Oxford describe the discovery of a new vent system and accompanying ecological community on the boundary between the South Scotia and South Sandwich Plates in the Southern Ocean, close to the Antarctic Peninsula.

Map of showing the location of the study areas (E2 & E9), on the East Scotia Ridge (ESR) between the South Scotia (SCO) and South Sandwich (SAN) Plates. Other legends are: (ANT) Antarctic Plate, (AP) Antarctic Peninsula, (PF) the Polar Front (the boundary between the polar atmospheric cell and the warmer Ferrel cell), (SACCF) the Southern Antarctic Current Front (a deep-sea current front), (SAF) the Sub-Antarctic Front (the northern boundary of the Antarctic Circumpolar Current), and (SAM) the South American Plate. From Rogers et. al (2012).

Scientists have thought there were probably hydrothermal vents in the area since the area was visited by the Towed Ocean Bottom Instrument (TOBI) in 1999. TOBI is a sonar mapping instrument used to build a three dimensional model of the sea-floor, it is operated by the National Oceanography Centre at the University of Southampton. The new study details the first actual visits to the site, first by a lowered camera system in 2009, then by the ROV Isis submersible in 2010.

The East Scotia Ridge vents produce highly acidic, hydrogen sulphide (H₂S) rich water at temperatures of up to 383 °C. This supports a diverse community of organisms based around a type of Yeti Crab, which cultures filamentous sulphur-oxidizing bacteria on hair-like setae covering its body.

A carpet of Yeti-Crabs at the E9 Hydrothermal Vent. The seaweed-like growths at the top right are Stalked Barnacles. From Rogers et al. (2012).

The vents also supported a number of other organisms, including stalked barnacles, sea anemones, sponges, worms, snails, limpets, starfish, octopus and shrimps. This is similar (but not identical) to the fauna previously described at the Pacific-Antarctic Ridge (and that found at cold seeps off Costa Rica) but very different to the fauna of the Mid-Atlantic Ridge, which is dominated by a species of mussel.

An image of a vent at the E9 site. The white substance on the chimneys is a carpet of Yeti Crabs, while the brown area to the fore is a carpet of Snails.

The Antarctic shallow sea-floor is strange in that it hosts the most diverse community of benthic (bottom-dwelling) invertebrates on the planet; all other ecosystems are at their most diverse in the tropics, and the Arctic is not especially rich in benthic invertebrates. Most of these invertebrates are highly endemic; that is to say they are exclusive to the Antarctic, and not found anywhere else. The similarity between the invertebrate fauna at the East Scotia Ridge and that at the Pacific-Antarctic Ridge, and the dissimilarity of either to those on other hydrothermal vents in the Atlantic and Pacific suggests that this is also the case for these deep-sea hydrothermal vent communities.

Other animals at the East Scotia Ridge site. (A) Sea anemones and Stalked Barnacles, (B) Sea Anemones and Snails, (C) Sea Anemones and Yeti Crabs, (D) Snails, (E) Stalked Barnacles and Starfish, and (F) an Octopus.

See also New Submarine Volcanoes discovered in the South Sandwich Islands.

2011 Tōhoku Tsunami debris reaches coast of British Columbia.

On 11 March 2011 the Tōhoku Coast of northeast Japan was devastated by an Earthquake with a magnitude of 11 on the Richter Scale, and the tsunami that it triggered (a tsunami is a huge wave caused by an Earthquake or landslide), which reached heights of over 40 m in places and travelled up to 10 km inland. This was the most devastating Earthquake ever to strike Japan, and one of the largest Earthquakes ever recorded.

Video footage of the 11 March Tsunami striking a Japanese coastal town.

In total the earthquake and tsunami are known to have killed 15 844 people, with another 3451 missing and 5890 injured. It devastated coastal towns across eighteen prefectures, destroyed a nuclear power station, a dam, around 125 000 buildings and the infrastructure of a large area of northeast Hokkaido.

As a consequence of this devastation, around 18 million tonnes of debris was washed into the Pacific Ocean, and has been drifting eastward (the prevalent current direction in the North Pacific) ever since. In October 2011 Jan Hafner and Nikolai Maximenko of the International Pacific Research Center at the University of Hawaii calculated that the debris would cover an area roughly 3200 km by 1600 km and would reach Hawaii in early 2013 and British Columbia in 2014, with debris eventually washing up from Alaska to Baja California. This model seemed to have been confirmed when the debris field was observed in the area predicted by the Russian tall ship STS Pallada.

The path of the debris from the 2011 Tsunami, as predicted by the University of Hawaii Team.

Around the beginning of December 2011 reports started to come in of debris from the Tsunami being washed up on the shore of Vancouver Island, around the town of Tofino. At first the local authorities dismissed this, floating rubbish from Japan and China is a regular occurrence on the coast of British Columbia, but by the end of month it was becoming clear that there was a lot more being washed up than usual, and that the items arriving were different from the usual waste; personal items rather than bottles and packaging, and a large amount of timber.

Timber bearing markings identifying it as coming from Japan on beach near Tofino.

Local Mayor Perry Schmunk has been in contact with a number of Canadian governmental agencies in order to develop a plan to deal with any further increase in the debris arriving. Tofino residents have expressed concern at the possibility of radioactive waste from the Fukushima Nuclear Power Plant or even human remains arriving on the local beaches, though the United States National Oceanic and Atmospheric Administration have described this as unlikely.

See also Rethinking Energy, Magnitude 7.1 Earthquake off the Sanriko Coast, Magnitude 6.4 Earthquake off the coast of Honshu, Earthquake off the coast of Vancouver Island and Earthquakes on Sciency Thoughts YouTube.