Monday, 16 September 2019

Joania cordata & Argyrotheca cuneata: The discovery of abundant Brachiopods in a Seagrass meadow on the south coast of Crete suggests that these 'rare' Invertebrates may be more common than previously thought.

Brachiopods (or Lampshells) superficially resemble Bivalve Molluscs, though they are not closely related. They were abundant in the seas of the Palaeozoic, often dominating benthic faunas, but today are comparatively rare, and seldom seem outside the tropics. Brachiopods have a filter feeding apparatus called a lophophore, unlike anything found in any Mollusc, but also found in Bryozoans and Phoronid Worms. This is encased with in a shell with two valves, each symmetrical about a midline, but not necessarily the same as each other, along with the rest of the organs of the body; there is typically remarkably little flesh to a Brachiopod compared to a Mollusc with a shell the same size. Brachipods formed a dominant part of benthic invertebrate communities during the Palaeozoic, but became steadily rarer during the Mesozoic Marine Revolution, during which the appearance of many types of grazing invertebrates, such as Starfish, carnivorous Snails, and Decapod Crustaceans, caused many earlier benthic groups to decline or disappear. Brachiopods are still around today, but are rare, with most species found either in deep waters or cryptic environments such as caves.

In a paper published in the journal Marine Biodiversity on 14 June 2019, Paolo Albano and Martina Stockinger of the Department of Palaeontology at the University of Vienna, describe the discovery of a dense population of Brachiopods living within a Seagrass meadow on the south coast of Crete.

Albano and Stockinger used a vacuum pump system to suck up organisms from the dense rhizome (root) mat layer of a meadow of Neptune Grass, Posidonia oceanica, at depths of between 5 and 20 m off the south coast of Crete. This environment is difficult to sample using traditional methods such as dredging or handpicking by divers, due to the dense nature of the Neptune Grass, and therefore little is known about the organisms which live their.

A meadow of Neptune Grass, Posidonia oceanica, note the density of the colony. Alberto Romeo/Wikimedia Commons.

This method revealed colonies of two species of Megathyrid Brachipod, Joania cordata and Argyrotheca cuneata, living on the rhizomes of the Neptune Grass, as well as many shells of these species, plus large numbers of a third species, Megathiris detruncata, and a single specimen of a fourth, Novocrania anomala, in the sediments below. None of thee species reaches more than a few millimetres in size, making them more-or-less impossible for divers to spot among the dense Neptune Grass.

Living Brachiopods from the rhizome layer of the Posidonia oceanica meadow in Plakias, southwestern Crete Greece. (a) Joania cordata on plant debris, from a depth of 20 m; (b) Argyrotheca cuneata on plant debris, from a depth of 20 m; (c) Joania cordata inside the aperture of an empty shell of the Gastropod Bittium latreillii, from a depth of 10 m; (d) Joania cordata beneath the Bryozoan Patinella radiata, from a depth of 10 m; (e) Joania cordata attached to the Foraminiferan Miniacina miniacea, from a depth of 20 m; (f) Argyrotheca cuneata attached to the Foraminiferan Miniacina miniacea covered by a Bryozoan colony of Hippaliosina depressa. Scale bar is 1 mm. Albano & Stockinger (2019).

Most living populations of Brachiopods are found below the photic zone, or in cryptic environments such as caves (or shipwrecks), environments where predator numbers are lower, but so is nutrient availability. As such Brachiopods are considered to be minor parts of modern ocean faunas. The discovery of Brachiopods living in a dense population within a Seagrass meadow challenges this assumption, as such meadows are one of the most widespread habitats in shallow marine environments, suggesting that Brachiopods could be much more abundant today than is generally realised.

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Asteroid 2019 RT3 passes the Earth.

Asteroid 2019 RT3 passed by the Earth at a distance of about 555 800 km (1.45 times the average  distance between the Earth and the Moon, or 0.37% of the distance between the Earth and the Sun), slightly after 4.10 am GMT on Monday 9 September 2019. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2019 RT3 has an estimated equivalent diameter of 18-57 m (i.e. it is estimated that a spherical object with the same volume would be 18-57 m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere between 25 and 10 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2019 RT3. JPL Small Body Database.

2019 RT3 was discovered on 11 September 2019 (two days after its closest approach to the Earth) by the Atlas MLO Telescope at Mauna Loa Observatory in Hawaii. The designation 2019 RT3 implies that the asteroid was the 91st object (bject T3 - in numbering asteroids the letters A-Z, excluding I, are assigned numbers from 1 to 25, so that T3 = (24 x 3) + 19 = 91) discovered in the first half of September 2019 (period 2019 R).

2019 RT3 is calculated to have an 904 day orbital period and an eccentric orbit tilted at an angle of 4.35° to the plane of the Solar System, which takes it from 0.99 AU from the Sun (i.e.99% of the the average distance at which the Earth orbits the Sun) to 2.67 AU from the Sun (i.e. 267% of the average distance at which the Earth orbits the Sun, outside the orbit of the planet Mars). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). 2019 RT3 is thought to have had one previous close encounter with the Earth, on 13 October 2014.

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Indian schoolgirl dies after being bitten by Cobra.

A schoolgirl has died after being bitten by a Cobra in Tamil Nadu State, India, on Sunday 15 September 2019. The girl, identified as R Varsha, 14,  was bitten by the Snake while sleeping in a hostel attached to a government-aided school in the city of Dindigul. She alerted her friends to the incident after feeling the bite and beginning to feel ill, but rapidly went into convulsions and died on the way to hospital. A Cobra was later found in the room and killed.

A fatal Snake bite attributed to a 'Cobra' in India (the term Cobra is used to describe a variety of Snakes in Asia, Africa, and the Americas, not all of which are closely related) will almost certainly have been the work of an Indian Cobra, Naja naja, an Elapid Snake which is one of four species of Snakes that are responsible for almost all Human fatalities in South Asia, along with the Common Krait, Bungarus caeruleus, the Russell's Viper, Daboia russelii, and the Indian Saw-scaled Viper, Echis carinatus. About 30% of Indian Cobra bites are fatal, falling to about 9% with prompt medical treatment. The species does not intentionally target Humans, which it is far too small to consume, reaching a maximum size of about 1.5 m (larger specimens have been recorded from Sri Lanka). However the species does regularly enter Human dwellings in pursuit of small Rodents (it's main prey), and will sometimes attempt to nest in Human bedcloths, which can have fatal consequences if Snakes are disturbed and lash out.

An Indian Cobra, Naja naja. Snake Facts.

Although not considered to be endangered, Indian Cobras are protected by law in India. This is due to their former use in street entertainment by Snake charmers, and in staged Mongoose fights, both of which are now illegal as they are considered to be cruel. The species is also listed under the Convention on the International Trade in Endangered Species (CITES), although this is due to the resemblance of its skin to that of more endangered species.

The King Cobra, Ophiophagus hannah, is also present in Tamil Nadu, and is certainly capable of delivering a fatal bite. However King Cobras are essentially a woodland species, and tend to avoid Humans and Human structures. Even when provoked King Cobras tend to try to escape before biting, and will typically give an impressive display to try to frighten away aggressors before actually attacking. As such almost all people bitten by King Cobras are professional Snake handlers, although the fatality rate among those bitten can be as high as 50%, requiring that the species be treated with considerable respect.

A King Cobra, Ophiophagus hannah. World Atlas.

King Cobras are considered to be Vulnerable under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species, due to habitat loss and hunting for their skins (King Cobras can reach almost six metres in length, massive for a venomous Snake, and therefore produce a large and desirable skin). They are strongly protected in India, and killing one can result in a six year prison sentence.

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Cetacean sightings within the Great Pacific Garbage Patch.

The Great Pacific Garbage Patch is an area of the Pacific Ocean between Hawai'i and California, and is one of a series of patches where an ocean gyre (rotating current) tends to trap floating plastics, resulting in an ever growing patch of discarded nets, ropes, lighters, toothbrushes, water bottles, pens, baby bottles, cell phones, plastic bags, and microplastics. The area is known to be on one of the major sea routes used by migrating Whales, and a variety of Whale species have washed up dead on the Californian coast with plastics in their stomachs, leading to concerns that the debris may be causing Whale fatalities, both through ingestion and entanglement, though there has to date been no direct studies of the impact of the garbage patches on Whales.

In a paper published in the journal Marine Biodiversity on 9 April 2019, Susan Gibbs of the Ocean Cleanup Foundation, Chandra Salgado Kent of the Centre for Marine Science and Technology at Curtin University, Oceans Blueprint, and the Centre for Marine Ecosystems Research at Edith Cowan University, Boyan Slat, also of the Ocean Cleanup Foundation, Damien Morales, again of the Ocean Cleanup Foundation, and of Blue Planet Marine, Leila Fouda, once again of the Ocean Cleanup Foundation, and of the School of Biological and Chemical Studies at Queen Mary University of London, and Julia Reisser of the Minderoo Foundation, and the Oceans Institute at the University of Western Australia, describe the results of an aerial survey of the Great Pacific Garbage Patch, which specifically targeted Whales present within the area.

Gibbs et al. made two survey flights over the Great Pacific Garbage Patch using a Hercules C-130 aircraft flying out of Moffett Airfield in California, during October 2016, during each of which a series of transects of the patch were made. During each flight eight people were used to record Whale sightings, working in pairs from each of the plane's paratroop doors, with one person acting as a spotter and the other a recorder. Where possible Whales were also photographed.

A total of 14 Whales were spotted in seven groups, plus 1280 large plastic items (fishing nets etc.). The Whales were not evenly distributed across the patch, five of the seven sighting having occured in a brief period of time, large items of plastic were quite often seen in close proximity to Whales.

The first sighting comprised a group of four small Toothed Whales, Odontocetes, of an unknown species. The second sighting was of three Sperm Whales, Physeter macrocephalus, a mother, calf and an escort; the calf was about four and a half metres in length, suggesting it was vert young (Sperm Whale Calves are about four metres long when born, and grow very rapidly). The third sighting was of a large dark Whale of uncertain species, possibly another Sperm Whale. The fourth sighting was of a single 'relatively large' Whale.the fifth sighting was of two large Baleen Whales, Mysticeti, identified by the observation of two large blows with shapes consistent with those produced by the double blowholes of Baleen Whales. The sixth sighting was of a single Beaked Whale, Ziphiidae, of uncertain species. The seventh sighting was of two further Beaked Whales. The final three Whales were probably Cuvier’s Beaked Whales, Ziphius calvirostris, but could not be confidently identified, and may not all have been of the same species.

Cetaceans and ocean plastics within the Great Pacific Garbage Patch. In the map, background colour levels represent predicted plastic pollution gradient (red = highest levels, blue = lowest levels); grey lines show the survey transects (~665 km each) and black dots indicate locations of the seven Cetacean sightings. Photographs above the map show some of the Cetaceans observed in this study: Sperm Whales (sighting 2, and sighting 3) and Beaked Whales (sighting 6, and sighting 7); red circles in sighting 3 indicate debris locations. Photographs in the right side of the figure give examples of debris types sighted: ‘ghostnets’, ropes, crates and buoys. Gibbs et al. (2019).

The most common identifiable large items of plastic were abandoned fishing nets, followed by containers, buoys, lids, and ropes. Only three of the Whales could be identified to species level, but the observed specimens included Sperm Whales, Beaked Whales and Baleen Whales, all of which have been found washed up on Californian beaches with plastics in their stomachs, implying that they are affected by the plastic waste in the garbage patch.

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Sunday, 15 September 2019

Seven killed in landslides in Nepal.

Seven people have died in two landslides in Nepal this week. Six members of the same family died when their house was swept away when a road collapsed onto it in the village of Cherlabang in Rolpa District on Thursday 12 September 2019. They have been identified as Jaya Budha, 38, his wife Muljyoti Budha, 36, and their two daughters, Bewasti, 9, and Karishma, 2, as well as Shiva Kumari Budha, 28, and her son Asal, 4. Shiva Kumari Budha's husband is understood to be working overseas. The incident was caused by the collapse of a section of the Ghartigaun-Thawang Highway above the village. Residents of the village had been raising concerns about the construction of this highway for some time, claiming that contractors had carried out shoddy work in the absence of proper governmental supervision, and it is understood that Shiva Kumari Budha and her son had moved in with Muljyoti Budha's family out of concern that her own home might be vulnerable to such an event. 

The approximate location of the 12 September 2019 Cherlasbang landslide. Google Maps.

On Friday 13 September a rockfall on the Siddhartha Highway at Siddhababa in Palpa District, hit two vehicles, killing the driver of one, who has been identified as Kamal Pariyar of Gulmi District. Two people in the other vehicle escaped unhurt. 

The scene of a landslide in Palpa District, Nepal, that killed the driver of a car on Friday 13 September 2019. Mukti Neupane/MyRepublica.

The incidents have been blamed on torrential rainfall that has fallen across the area in the last few days. Landslides are common during the monsoon season in Nepal, which lasts from May to September, with  the highest rainfall occurring in July. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall.

Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate. This situation is particularly intense in South Asia, due to the presence of the Himalayas. High mountain ranges tend to force winds hitting them upwards, which amplifies the South Asian Summer Monsoon, with higher winds leading to more upward air movement, thus drawing in further air from the sea. 

Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.
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Magnitude 2.0 Earthquake in the Scottish Borders.

The British Geological Survey recorded a Magnitude 2.0 Earthquake at a depth of about 7 km, roughly 2 km to the northwest of the village of Eddleton in the Scottish Borders Region of Scotland, slightly after 4.10 pm British Summertime (slightly after 3.10 pm GMT) on Wednesday 11 September 2019. This was not a major event, and presented no threat to human life or property, but people have reported feeling it in the village of Lyne.

The approximate location of the 11 September Scottish Borders Earthquake. Google Maps.

Earthquakes become more common as you travel north and west in Great Britain, with the west coast of Scotland being the most quake-prone part of the island and the northwest of Wales being more prone  to quakes than the rest of Wales or most of England. 

The precise cause of Earthquakes in the UK can be hard to determine; the country is not close to any obvious single cause of such activity such as a plate margin, but is subject to tectonic pressures from several different sources, with most quakes probably being the result of the interplay between these forces.
Britain is being pushed to the east by the expansion of the Atlantic Ocean and to the north by the impact of Africa into Europe from the south. It is also affected by lesser areas of tectonic spreading beneath the North Sea, Rhine Valley and Bay of Biscay. Finally the country is subject to glacial rebound; until about 10 000 years ago much of the north of the country was covered by a thick layer of glacial ice (this is believed to have been thickest on the west coast of Scotland), pushing the rocks of the British lithosphere down into the underlying mantle. This ice is now gone, and the rocks are springing (slowly) back into their original position, causing the occasional Earthquake in the process. 
(Top) Simplified diagram showing principle of glacial rebound. Wikipedia. (Bottom) Map showing the rate of glacial rebound in various parts of the UK. Note that some parts of England and Wales show negative values, these areas are being pushed down slightly by uplift in Scotland, as the entire landmass is quite rigid and acts a bit like a see-saw. Climate North East. 

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. If you felt this quake, or were in the area but did not (which is also useful information) then you can report it to the British Geological Survey here.

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