At least fourteen people dead as Storm Daniel sweeps across Greece, Turkey, and Bulgaria.

At least nine people have died, and several more are missing, after Storm Daniel swept across Greece, Turkey, & Bulgaria on Monday 4 and Tuesday 5 April 2023. In Greece a man died when a wall collapsed onto him in Volos on the Pagasetic Gulf, on Monday 4 September, and another man was killed in a vehicle-related incident, while on Wednesday 6 September the body of an elderly woman who was missing was found close to the city, having apparently drowned in the storm. Another four people are still missing in Greece. Considerable damage to infrastructure has occurred, and about a hundred people were evacuated from affected areas.

A collapsed bridge at Kala Nera on the western Pelion Peninsula. Stamos Prousalis/Reuters.

In Turkey at least two people have died in flooding in Istanbul and dozens have had to be rescued as floodwaters covered two neighbourhoods of the city, while in Kirklareli Province, close to the border with Bulgaria, five tourists are known to have died when a flash flood hit a campsite at which they were staying, and another one is still missing. Across the border in Bulgaria, four people are known to have died and three more are still missing after flooding hit the Black Sea coastal region.

Flood damage at Arnavutköy in Istanbul Province, Turkey. Ugur Yildirim/Getty Images.

Most storms form due to heating of air over the sea. As the air is heated the the air pressure drops and the air rises, causing new air to rush in from outside the forming storm zone. If this zone is sufficiently large, then it will be influenced by the Coriolis Effect, which loosely speaking means the winds closer to the equator will be faster than those further away, causing the storm to rotate, clockwise in the northern hemisphere and anticlockwise in the southern hemisphere.

A caravan swept out to sea on Bulgaria's Black Sea coast. Sofia Globe.

Whilst the high winds associated these storms is extremely dangerous, the real danger from such storms is often the flooding. Each millibar drop in air pressure can lead to a 1 cm rise in sea level, and large storms can be accompanied by storm surges several meters high. This tends to be accompanied by high levels of rainfall, caused by water picked up by the storm while still at sea, which can lead to flooding, swollen rivers and landslides; which occur when waterlogged soils on hill slopes lose their cohesion and slump downwards, over whatever happens to be in their path.

Such storms are common in tropical regions, but less so on the more temperate Mediterranean. However, this summer much of the eastern Mediterranean has suffered a prolonged heat wave, with temperatures regularly exceeding 40°C, and heat related deaths recorded across much of southern Europe, as well as a series of wildfires which have swept across Greece and other countries as vegetation has dried out. These events have been caused by a combination of an anticyclone (high pressure system) which formed over the Sahara then migrated northwards, intensified by an El Niño system over the southern Pacific, which tends to drive temperatures upwards in the Northern Hemisphere, both of which are considered to have been intensified by global warming.

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Magnitude 4.3 Earthquake beneath the northern Black Sea.

The United States Geological Survey recorded a Magnitude 4.3 Earthquake at a depth of about 36.8km roughly 14 km off the coast of the Town of Anapa in Krasnodar Krai, Russia, slightly after 8.35 am local time (slightly after 5.35 am GMT) on Sunday 15 March 2020. There are no reports of any damage or injuries relating to this quake, but people have reported feeling it in Anapa.

The approximate location of the 15 March 2020 Black Sea Earthquake. USGS.

The Black Sea is largely upon the Eurasian Plate, as are Georgia and Russia. Turkey, however, lies on a separate plate, the Anatolian Plate. This is being pushed to the west by the northward movement of the Arabian Plate, which is in turn being pushed by the African Plate, further to the south. This creates as zone of faulting along the northern part of Turkey, the North Anatolian Fault Zone, as the two plates are pushed past one-another (transform faulting). This is not a simple process, as the two plates constantly stick together, then break apart as the pressure builds up, leading to Earthquakes, which can be some distance from the actual fault zone.

 How the movement of the Arabian Plate causes movement on the North Anatolian Fault Zone. Université Montpellier 2.

This northward movement of the African and Arabian Plates also causes folding and uplift in the Caucasus Mountains, which separate Georgia from Russia. Again this is not a smooth process, with the rocks sticking together, then moving sharply as the pressure builds up enough to break them appart, which can also lead to Earthquakes in the region.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.

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Huge swarms of Moon Jellyfish seen in Balaklava Bay, Crimea.

People in Russian-annexed Crimea have reported vast numbers of Moon Jellyfish, Aurelia sp., in the Balaklava Bay are of the Black Sea over the past month. Moon Jellyfish are a usual occurrence in the Black Sea, but this years swarms are far larger than are usually seen, probably due to a  population boom fuelled by unseasonably warm waters, combined with a high nutrient level in the sea, which can in turn be traced to high rainfall levels on land, caused by higher evaporation from the warm water. Although the number of Jellyfish is startling, there is little cause for concern, as, while Moon Jellyfish can sting, their venom is not generally strong enough to cause a serious health risk to Humans.

 Moon Jellyfish, Aurelia sp., in Balaklava Bay, Crimea, this month. Evqesha Land/Instagram/Moscow Times.

Members of the genus Aurelia are inshore Jellyfish found in coastal waters in tropical, subtropical and temperate seas around the world. They are large Jellyfish, reaching a maximum size of about 40 cm in diameter, a slight purplish tinge and four large, horseshoe-shaped gonads. Moon Jellyfish often undergo major blooms in the summer months, due to their tolerance for low oxygen conditions, which are harmful to most of their competitors and predators (Fish and large invertebrates), enabling them to dominate environments where these animals are excluded. This tends to lead to summer blooms in enclosed areas (heat and lack of exchange with the open ocean can rapidly deplete oxygen levels), which can be worse in areas where pollution from agriculture or other Human activities leads to eutrophication (excess nutrients which can lead to eutrophication and the rapid growth of blooms of Algae, Bacteria or other micro-organisms, which absorb oxygen from the water leading Fish and other aquatic organisms to asphyxiate). 

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Sulfurimonas marisnigri: A Manganese reducing Bacterium from the Black Sea.

Most familiar organisms respire using oxygen, a process in which the oxygen is 'reduced' by when it accepts an electron from a donor atom, typically carbon (electrons have a negative charge, so the charge on the oxygen atom goes down when it accepts an electron, hence it is reduced, even though it has gained something). Many Bacteria, however, respire using sulphur instead, a system of respiration that is thought to be older than oxygen respiration. Many enclosed ocean basins, such as the Black Sea, have a heavily stratified water column (i.e. little movement of water between upper and lower layers), with an oxygen rich upper layer, with abundant oxygen-respiring Bacteria, and a sulphur rich bottom layer, with many sulphur-respiring Bacteria. Between these layers is a middle layer lacking abundant sulphur or oxygen, but yet which appears to host a large Bacterial population, particularly immediately above the sulphur-rich layer, where something is actively fixing carbon from carbon dioxide at a high rate. Quite what the Bacteria in this layer might be respiring is unclear; the element manganese has been suggested as a possible electron acceptor which would be present in these waters, but to date no manganese-respiring Bacterium has ever been discovered.

In a paper published in the Proceedings of the National Academy of Sciences of the United States of America on 3 June 2019, Jan Henkel of Biological Oceanography at the Leibniz Institute for Baltic Sea Research Warnemünde, Olaf Dellwig of Marine Geology, also at the Leibniz Institute for Baltic Sea Research Warnemünde, Falk Pollehne, also of Biological Oceanography at the Leibniz Institute for Baltic Sea Research Warnemünde, Daniel Herlemann, again of Biological Oceanography at the Leibniz Institute for Baltic Sea Research Warnemünde, and of the Centre for Limnology at the Estonian University of Life Sciences, Thomas Leipe again of Marine Geology at the Leibniz Institute for Baltic Sea Research Warnemünde, and Heide Schulz-Vogt, once again of Biological Oceanography at the Leibniz Institute for Baltic Sea Research Warnemünde, describe a new species of Bacterium from the Black Sea, which is able to respire manganese.

The Bacterium was collected in November 2013 during a voyage of the Research Vessel Maria S. Merian to the Black Sea, which sampled water from several layers within the suboxic zone. They found a high prevalence of  Epsilonproteobacteria (a group which includes the pathogenic Helicobacter and Campylobacter, as well as marine bacteria responsible for the fixation of carbon from carbon dioxide below the photic zone) within a layer above the sulphur-rich layer, which contained hydrogen sulphide (i.e. reduced sulphur, which can act as an electron donor), but not a recipient), but no oxygen or nitrates (which are known to be respired with hydrogen sulphide by some bacteria). From this they were able to obtain an unknown species of Sulfurimonas, which appeared to be closely related to Sulfurimonas gotlandica, a species known to respire nitrates with hydrogen sulphide.

The new species is named Sulfurimonas marisnigri, where 'marisnigri' means 'Black Sea' in Latin. It was found to be able to respire manganese dioxide with hydrogen sulphide, making it the first known Bacterium to be able to gain energy using manganese as an electron acceptor, and also to be able to fix carbon dioxide from the water column, producing manganese calcium carbonate. The cells of Sulfurimonas marisnigri are slightly curved, and 1-4 μm in length.

Scanning electron microscopy image of the isolate Sulfurimonas marisnigri. Henkel et al. (2019).

Henkel et al. note that unknown species of the genus Sulfurimonas are abundant in the oceans, both in open pelagic waters (waters not near land) and around hydrothermal vents and in marine sediments, environments in which manganese respiration is thought to be occurring, producing large amounts of sulphates and manganese calcium carbonate.

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Earthquake beneath the eastern Black Sea.

On Sunday 23 December 2012, slightly after 5.30 pm local time (slightly after 1.30 pm GMT) the United States Geological Survey recorded a Magnitude 5.5 Earthquake 10 km beneath the eastern Black Sea, roughly 35 km off the coast of Georgia. This is a fairly large quake for the area, but this far offshore is unlikely to have caused any damage or casualties. The quake was felt in Georgia, Turkey and Russia.

The location of the 23 December Earthquake. Google Maps.

The Black Sea is largely upon the Eurasian Plate, as are Georgia and Russia. Turkey, however, lies on a separate plate, the Anatolian Plate. This is being pushed to the west by the northward movement of the Arabian Plate, which is in turn being pushed by the African Plate, further to the south. This creates as zone of faulting along the northern part of Turkey, the North Anatolian Fault Zone, as the two plates are pushed past one-another (transform faulting). This is not a simple process, as the two plates constantly stick together, then break apart as the pressure builds up, leading to Earthquakes, which can be some distance from the actual fault zone.

How the movement of the Arabian Plate causes movement on the North Anatolian Fault Zone. Université Montpellier 2.

This northward movement of the African and Arabian Plates also causes folding and uplift in the Caucasus Mountains, which separate Georgia from Russia. Again this is not a smooth process, with the rocks sticking together, then moving sharply as the pressure builds up enough to break them appart, which can also lead to Earthquakes in the region.

See also Two major Earthquakes in northeast Iran, leading to heavy death toll, Earthquake in eastern Turkey, Earthquake off the Turkish coast, Earthquake in northwest Azerbaijan and Earthquakes on Sciency Thoughts YouTube.

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