Arxiu d'etiquetes: israel

Nature in times of war

The actual world  is in turmoil. News related to terrorism, drug trafficking, coups d’état,  refugees crisis or the numerous wars still present flood our screens day after day. And, in a completely understandable bias, the focus is almost exclusively on the people and countries involved. But (and it’s something I ask every time I watch the news) what happens to nature in these regions punished by violence? In this entry we review the most important armed conflicts nowadays and their consequences for the nature surrounding them.

INTRODUCTION

Any human action has repercussions on natural life, and even more wars, intrinsically destructive. A series of damages on the wildlife are associated with them such as deforestation, soil degradation, pollution or hunting, among many others. The first time we really became aware of the great impact of the wars on nature was in the Vietnam War. The US army, in its fight against an invisible enemy, threw more than 75 million liters of herbicides into the jungles, in order to defoliate the trees to find their enemies. However, despite partially achieving its objective (we all know how that war ended) nature was seriously damaged. A study carried out in Vietnam in the mid-1980s found that there were only 24 birds and 5 mammals in an area where there were previously between 145 and 170 birds and between 30 and 55 mammals.

800px-us-huey-helicopter-spraying-agent-orange-in-vietnam
A Huey helicopter from the US military overhangs the jungles of Vietnam while ‘bathing’ them with orange agent. Agent Orange was a potent herbicide and defoliant used by the United States during the war to make more visible enemies hidden in the jungle. A single plane could defoliate tens of hectares in a single flight. The US government spent $ 60 million a year on Agent Orange. Source: Zmescience.

Other wars, such as the Civil War in Rwanda, apart from causing more than 500,000 deads and displacing more than 2 million of people, left the nature of the country in a state of absolute crisis. In the Akagera National Park, one of the most emblematic environments in the country, deforestation wreaked havoc: 200,000 of the 300,000 hectares of forest were lost in just 3 years, as well as 90% of large mammals.

But what is happening today? How are the wars of today affecting the survival of nature? Here we review the most important current conflicts and their difficult coexistence with the wildlife of the region.

Israeli-Palestinian Conflict (1948-present)

Although the last war between Israel and Palestine began in 2005, violence between the two countries has been present since the creation of the state of Israel. Thousands of people have been dead for decades, and millions have been displaced against their will. And, of course, nature has not come out unscathed.

One of the most famous cases occurred in 2006. The Israeli army bombarded two oil tanks near a power station in Jieh, Lebanon (where a terrorist group called Hezbollah was emplaced) causing a spill of 10,0000 and 15,000 cubic meters of oil in the Mediterranean sea. This black tide spread along 90 km of the coast of Lebanon, carrying the death with it. In addition, this phenomenon severely affected the habitat of the green turtle (Chelonia mydas) in one of the last well-preserved places that this species still had in the Mediterranean basis.

2316325_xl
The bombing of two oil tanks by the Israeli army left 80 km of the Lebanese coast as can be seen in the image. In 2014, the United Nations Assembly urged Israel to compensate Lebanon with $ 856.4 million for this environmental catastrophe. Source: hispantv.

However, in early 2016, images that would call even more international attention came to light: dozens of animals from the Gaza zoo appeared completely mummified after suffering a terrible agony and starving. It happened twice since the zoo opened in 2007, but the strongest famine took place in 2014, following a conflict between Israel and Hamas’s Palestinian forces. It is estimated that about 80 animals died because of famine, including crocodiles, tigers, baboons or porcupines. When rescue services were able to reach the zoo, only 15 animals remained alive, many of them with severe symptoms of malnutrition.

gaza-zoo-2
The Gaza zoo became the World’s Worst Zoo due to the shocking images of mummified bodies as a result of the famine that caused the war. According to Abu Diab Oweida, the owner of the zoo, the bodies were mummified so that everyone could see that even the animals were affected by the war. Source: Dailymail.
caballos-muertos
The continuous bombing in the Gaza Strip cause numerous casualties, such as those of the horses in the picture. Unfortunately, the end of the conflict is still so far. Source: helpinganimalsingaza.

Second Congo War (1998-2003)

This war, also known as the Great War of Africa or the African World War, has caused the death of more than 5 million people since then, which has given it the dubious honor of being the deadliest armed conflict since The Second World War. Although the war officially ended in 2003 and there is an elected government since 2006, the Democratic Republic of the Congo lives in a state of instability typical of a country at war.

The guerrillas use the country’s many natural resources to obtain money so they can continue the war. And ivory is the most precious commodity, the one that produces the most benefits. That is why African elephant populations (Loxodonta africana) have been reduced by 90% since the beginning of the conflicts. Something worse has occurred to the northern white rhinoceros (Ceratotherium simum cottoni) a subspecies of the white rhinoceros. Its last specimens, 2 males and 2 females living in the Garamba National Park, are believed to have died between 2006 and 2008 at the hands of the guerrillas, causing the extinction of this subspecies.

gorila-de-montana
The mountain gorilla (Gorilla beringei beringei), with an estimated population of  only 700 individuals, lives almost exclusively in the Virunga Mountains, a territory shared by the Democratic Republic of Congo, Rwanda and Uganda. In the picture, a mountain gorilla killed by unknown causes in 2007. It is believed that the rangers were involved in his death. Source: The Guardian.

Bushmeat, or the food coming from wild animals, is another major problem stemming from the numerous military conflicts in the country. In the wake of extreme poverty, many villagers have been forced to hunt to survive. And the primates has been one of the most harmed groups. The populations of the great primates, once counted by millions, have been drastically reduced. It is believed that there are only 200,000 lowland gorillas, 100,000 chimpanzees and 10,000 bonobos in freedom.

bonobo-killed
Bonobos (Pan paniscus) are our closest relatives, and one of the most threatened animals in the Congo. It is endemic to this country, but is being heavily hunted for food and, more recently, to serve as a delicacy to the Asian market. Specimens such as it appears in the image can easily be found in the markets of Kinshasa and Brazzaville. Source. National Geographic.

Syrian Civil War (2011-present)

Undoubtedly, the most famous war at the moment. This conflict has killed more than 500,000 people and has caused one of the most important humanitarian crises of our time: it is estimated that there are more than 10 million of refugees because of the war. Those who have remained in Syria, have been displaced from the interior to the coastal zone, becoming a great threat to the forests of the region. According to Aroub Almasri, a Syrian government environmentalist, most people need food, electricity and fuel to cook and warm up, which has lead to clear the area’s forests, mostly in protected areas. Apart from the severe impact of deforestation, there are also a large number of fires that have been spreading throughout the region in recent times. A particularly affected area is the Fronlok forest on the border with Turkey. In these mountains the degree of endemism is high, and many species are at a serious risk of disappearing from the area, especially a type of oak, Quercus cerris, native to the region and which would begin to be threatened.

Due to the fragmentation of the habitat, it is believed that an iconic species of the Mediterranean zone and classified as critically endangered by IUCN has become extinct in Syria. It is the bald ibis (Geronticus eremita), a bird of which only 500 individuals remain and is present only in three countries: Morocco, Turkey and Syria. In spite of Syria‘s enormous effort to maintain a stable population in its territory, the war wiped out the last individuals of this species in the region. Only one individual of the species remains, a female named Zenobia, who was seen for the last time in Palmyra before ISIS troops entered the city.

ibis-eremita
It seems that the numerous efforts made by the Syrian government in the early years of the twenty-first century have been insufficient to save this iconic species from extinction. Formerly present in large parts of Europe (from Austria to the Iberian Peninsula) the bald ibis has the most important populations in Morocco, its last redoubt in the natural state. Source: New Scientist.

Second Libyan Civil War (2014-present)

After the first Libyan civil war, which ended with the fall of Colonel Gaddafi, the country entered into a spiral of violence sponsored by the numerous armed groups that control the country. The importation of meat from abroad has stopped, and the owners of sheep, goats and camels keep their animals as if they were gold because of shortages. Because of this, armed groups are heading to the south of the country, where anarchy prevails and there are a lot of wild animals to take advantage of.

One of the most harmed species has been the rhim gazelle (Gazella leptoceros), classified as threatened by IUCN and with its populations in decline. Ten years ago the population did not exceed several hundred individuals, and it is believed that today the situation is much worse.

slender-horned_gazelle_cincinnati_zoo
Rhim gazelle is native to North Africa, where there are less than 2,500 individuals. The militias use their meat to feed or sell it in the Libyan market, where it is scarce. Source: Creative Commons.

But the gazelles are not the only ones harmed by the banditry and impunity reigning in Libya. Large numbers of migratory birds, which have to cross the African country on their way to Europe, are slaughtered by hunters. In addition, the oases that they use to rest are being opened by the hunters, which causes that hundreds of cranes, ducks, herons and flamingos are annihilated without anyone can do anything.

In addition, the effect of the Libyan war on nature does not remain within its borders. In 2015, weapons from Libya were found near elephant corpses in Mali, a heavily threatened elephant subspecies. It is believed that the ivory of the Mali elephants is serving to finance the Libyan militias.

A slaughtered elephant is seen in Bambara-Maoude
Mali’s elephants are one of the only two populations of elephants living in the desert. The last air census (2007) revealed the presence of only 350 individuals in the country. In 2015, 80 elephant were hunted, so the forecasts are not at all flattering: scientists believe that the population will die out in 3 years. Source: Reuters.

The Colombian government against the FARC and other guerrillas (1964-2016)

Despite the peace agreement reached few months ago between the Colombian government and the FARC, both social and environmental wounds will take a long time to be closed. For a long time the militias have been financed largely from the money generated by illegal cocaine crops. Placed deep in the Colombian jungle, thousands of hectares of pristine forest have been cleared for the construction of laboratories and coca plantations. In addition, in an attempt to stop this type of illegal crops, the government fumigated extensive forest areas with glyphosate, a herbicide that, despite being considered harmless, caused the death of birds, small mammals and insects, what in turn left without sustenance the people who live on hunt. Another added problem is that illicit crops have spread to protected areas. Thus, according to a report by the National Parks of Colombia, FARC were present in 37 protected areas of the country, and 3791 hectares of coca plantations were also detected in there.

However, the illicit activity that most threatens Colombia’s nature is illegal mining, one of the most lucrative activities for armed groups. Not for less, since while 1 kg of coca is sold at about 4.3 million pesos, 1kg of gold is sold at 85 million pesos, about 20 times more. For this reason, large areas of jungle have been destroyed by backhoes to open gold (60%), coltan (25%), charcoal (10%) and tungsten (5%) mines. Deforestation resulting from illegal mining reaches unimaginable numbers: between 1990 and 2010, an average of 310,349 hectares of forest per year were deforested, that is, 6206.000 hectares in all that time, or what is the same, 5.4% of the Colombian surface.

mineria-ilegal2
Mercury and cyanide, highly contaminating metals, are used for the extraction of gold. It is estimated that about 200 tons of mercury go to Colombian rivers each year. This has caused, at least, the contamination oh 90 rivers, affecting the local fauna and flora. Source: Semana.

Finally, FARC actions against oil extraction have caused serious oil spills in areas of high environmental value. This is the case, for example, of the 492-liter oil spill in Puerto Asis, Putumayo, in June 2015. The FARC intercepted a convoy containing tanks with oil and spilled them, affecting 9 wetlands and spreading oil along the Putumayo River.

petroleo-derramado
In 2013, the FARC’s systematic attacks against the oil industry accounted for 132 only in the province of Putumayo. Hydrocarbons contaminate the soil and remain there for years. In water, oil, due to its oxygen consumption, creates anoxic conditions that causes the death of fish. Source: elcolombiano.

War in Afghanistan (2001-2014)

Either the last war and the previous one had a strong impact on the region’s wildlife. It is estimated that between 1990 and 2007, more than one-third of Afghanistan’s forests were cleared, either by refugees to use wood for cooking, fuel or construction, or by logging industries, which cut down the forests of the region with impunity.

Nevertheless, the news are more optimistic than would be expected of a country plunged into war for decades. Between 2006 and 2009, the first censuses since the 1970s were carried out in the province of Nuritán, with the help of trap cameras, the study of faeces and the realization of transects. The results were encouraging: 18 black bears, 280 porcupines and many red foxes, gray wolves, golden jackals, wildcats, palm civets and rhesus macaques were observed, and even the elusive snow leopard (Panthera uncia), concretely 3 distinct individuals.

leopardo-de-las-nieves
Photo-trapping cameras captured images of the elusive snow leopard in the rugged Afghan mountains. With no doubt, they are encouraging news for its conservation. Source: James Nava.

However, there are still threats for Afghan wildlife. The large number of bombs thrown during the years made a dent in the abundance of migratory birds. Many birds died directly from the impact of the bombs or poisoned when they came into contact with contaminated water. Others, however, varied their rute due to the bombing and no longer cross the country. This is the case of the Siberian crane (Grus leucogeranus), a species critically endangered by IUCN that has not been seen in Afghanistan since 1999. In addition, due to the war and the incipient Afghan economy, hundreds of hunters Are forced to catch live birds for subsequent smuggling into rich Arab countries. This has led to the fact that, in some regions of Afghanistan, migratory bird watching has declined by 85% since the start of the war.

afganistan-pajaros
According to the Afghanistan Environmental Protection director, every year around 5000 birds are hunted for contraband, especially in the regions of Syed Khel and Kohistan. Many of the Houwa bustards (Chlamydotes undulata) and different types of hawks are sent to rich Gulf countries to serve as pets. In the picture, Afghan hunters near their rudimentary cages. Source: focusingonwildlife.

Korean Conflict (1950-present)

The Korean Demilitarized Zone is the proof that even something as tragic as a war can bring positive consequences. In 1953, following the peace agreement by both countries, the Korean Demilitarized Zone, a strip of land 4 km wide and 250 km long that separates both countries, was created. The area, which has a strong military presence of about 2 million soldiers, has remained virtually unchanged and sparsely populated since then.

separacion-corea
The Demilitarized Zone of Korea, or DMZ, separates both countries thanks to a buffer zone 4 km wide. In this place, the leaders of both countries usually hold the infrequent and tense meetings. Source: Creative Commons.

The area is characterized by a great topographic richness and high variety of ecosystems, which allows it to contain a great diversity. Some scientific expeditions have documented more than 1,100 species of plants, 80 species of fish, 50 of mammals and hundreds of birds. In addition, it is a frequent stop for many species of migratory birds that head towards Mongolia, the Philippines or Australia.

zdc2
The area has a great diversity of flora and fauna. Deer, bears, wild boars and large numbers of birds inhabit the territory. It is even believed that it could contain some individuals of the siberian tiger, habitual inhabitant of the zone before the Japanese occupation of Korea. Source: BBC.

Recently, thanks to improved relations between the two countries, the area can be visited for only about 43 euros. In addition, due to its exceptional conservation status and high diversity, some campaigns are under way to turn the area into a protected area. One of these campaigns, the DMZ Forum, proposes to declare the area as World Heritage Site and World Park for Peace, in order to be able to protect it from a possible urban development on the day that peace between the two countries is reached.

zdc
The area has received numerous supports to convert it into a nature reserve in order to protect it from a possible future exploitation. Among the personalities who have supported the plan are the former US President Bill Clinton and the CNN founder Ted Turner. Source: BBC.

REFERENCES

DeWeerdt, Sarah (January 2008). “War and the Environment”. World Wide Watch. 21
King, Jessie (8 July 2006). “Vietnamese wildlife still paying a high price for chemical warfare”. The Independent.
Kanyamibwa S (1998). Impact of war on conservation: Rwandan environment and wildlife in agony. Biodiversity and Conservation, 7: 1399-1406.
Cover picture: Earth in transition.

Ricard-anglès

Mercuri en dofins llistats (Stenella coeruleoalba) del Mediterrani (I): origen i nivells

Després de setmanes sense poder escriure una entrada elaborada sobre un tema de cetacis, us deixo aquí una entrada força extensa sobre el mercuri en els dofins llistats que viuen al Mediterrani. En concret, tracta sobre l’origen i els nivells de mercuri en aquesta espècie. En una segona entrada es parlarà sobre l’efecte tòxic i la detoxificació d’aquest metall en els dofins llistats.  Espero que sigui del vostre interès.

 

INTRODUCCIÓ

El dofí llistat o ratllat (Stenella coeruleoalba) és un delfínid pelàgic petit comú en aigües temperades i tropicals d’arreu del món. La longitud mitjana dels individus del Pacífic oest és de 2,4 m en mascles i de 2,2 m en femelles (Archer i Perrin, 1999), tot i que els espècimens del Mediterrani mesuren un 10% menys que aquests (Andre et al. 1991). La seva dieta es composa principalment de peixos i calamars pelàgics i bentopelàgics (Archer 2009).

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El seu rang de distribució és ampli (Archer 2009): es troba al Pacífic Nord i Tropical; a l’Atlàntic, del nord d’Amèrica del Sud fins a Amèrica del Nord i a l’Atlàntic Nord est en aigües del Regne Unit; a l’Índic; i al Mar Mediterrani, on és l’espècie més abundant. La figura següent mostra el seu rang de distribució al Mediterrani.

dist

El seu estat de conservació a nivell global és de preocupació menor, però al Mediterrani és vulnerable degut a la interacció accidental o no amb la pesca (de palangre principalment, Aguilar 2000), la contaminació i al canvi climàtic (Otero i Conigliaro 2012).

 

ORIGEN DEL MERCURI DEL MEDITERRANI

La font principal de les elevades concentracions de mercuri observades als organismes del Mediterrani són dipòsits naturals de mercuri d’origen volcànic en moltes regions de la seva conca, en forma de cinabri (HgS) (André et al. 1991, Augier et al. 1993, Cardellicchio et al. 2000, Cardellichio et al. 2002b). A més, l’ús del mercuri en activitats industrials podria contribuir a augmentar els nivells de mercuri al mar (Cardellicchio et al. 2002b), tot i que el seu efecte en dofins llistats no sembla que pugui ser important pel fet de ser una espècie pelàgica i rarament els trobem prop de la costa (a 10 km de la font, el mercuri torna a nivells de fons, Andre et al. 1991).

 

NIVELLS DE MERCURI EN DOFINS LLISTATS DEL MEDITERRANI

Distribució en els diferents teixits

La Taula 1 següent mostra la concentració mitjana, la desviació i/o el rang de mercuri total (μg/g pes sec) al fetge, ronyó i múscul de dofins llistats de vàries localitats del Mediterrani. S’han seleccionat aquests tres òrgans per fer la comparativa perquè són els que més s’estudien en la bibliografia. De tota manera, s’ha de tenir en compte que la comparació de resultats de diferents estudis s’ha de fer en compte ja que hi ha múltiples fonts de variació com la condició, l’edat i el sexe els individus, però també amb els mètodes de presa de mostres i de mesura. Malgrat en aquesta taula només hi consten 3 òrgans, l’anàlisi següent s’ha centrat en tots els òrgans que han estudiat els diferents autors mencionats.

  Fetge Ronyó Múscul
  Mitjana SD (rang) Mitjana SD (rang) Mitjana SD (rang)
França(Andre et al. 1991) 1472 131(4,4-392) 104 153(6,3-806) 63 131(4,5-365)
França(Augier et al. 1993) 481 587(68-2271) 62 88(14-341 37 40(7,4-155)
Costa d’Apulia (Itàlia)(Cardellicchio et al. 2002b) 851 128(703-975) 46 9,7(34-59) 49 11(37-65)
Còrcega(Frodello et al. 2000) 460 58 49 4 21 2
Tirrè Nord(Leonzio et al. 1992) 324 (13-4400) 65 (5,8-204) 37 (6,5-168)
Itàlia Oest(Monaci et al. 1998) 593 1120 44 72 53 65
Espanya(Monaci et al. 1998) 1043 835 63 100 28 73
Israel(Roditi-Elasar et al. 2003) 603 900(6,3-2475) 45 50(8,6-122) 40 32(2,0-95)

Taula 1. Concentració de mercuri total (en μg/g pes sec) al fetge, ronyó i múscul de dofins llistats (Stenella coeruleoalba) de vàries localitats del Mediterrani

Tal com es desprèn de la Taula 1, els nivells de mercuri en dofins llistats del Mediterrani són molt elevats, trobant-se la màxima concentració de mercuri al fetge (Andre et al. 1991, Augier et al. 1993, Cardellicchio et al. 2002b, Frodello et al. 2000, Leonzio et al. 1992, Monaci et al. 1998, Pompe-Gotal et al. 2009, Roditi-Elasar et al. 2003). En altres mamífers marins, el fetge també és l’òrgan més contaminat (André et al. 1991, Augier et al. 1993). El segon i tercer òrgans amb una concentració més elevada són el ronyó i el múscul respectivament. En els casos en que s’ha estudiat la concentració de mercuri total al pulmó (Augier et al. 1992, Cardellicchio et al. 2002b, Frodello et al. 2000), aquest s’ha situat com a segon òrgan amb la concentració més alta. D’aquesta manera, es pot deduir el següent ordre en quant a la concentració de mercuri total en dofí llistat pels quatre òrgans: fetge >> pulmó > ronyó > múscul. S’han trobat nivells insignificatius de mercuri a la pell, al meló, al blubber i al cervell (Andre et al. 1991, Augier et al. 1993, Leonzio et al. 1992, Cardellicchio et al. 2002b, Frodello et al. 2000).

Aquest patró en les concentracions de mercuri es pot explicar per les vies d’entrada i eliminació del metall en dofins. L’elevada concentració al fetge dels dofins llistats del Mediterrani es deu a que, un cop ingerit el mercuri a través de l’aliment (que és la via d’entrada principal a l’organisme, Augier et al. 1993) o per la ingesta d’aigua (Augier et al. 1993, Frodello et al. 2000), es transporta fins al fetge i allà es detoxifica i s’hi acumula (Frodello et al. 2000, Krishna et al. 2003). L’elevada concentració als pulmons es pot explicar per la seva inhalació de l’atmosfera (Cardellicchio et al. 2002b). El ronyó, que emmagatzema una fracció important del metall, està involucrat en la seva eliminació, el que explica trobar valors intermedis. Finalment, la concentració al múscul s’explica pel fet de ser un teixit on s’hi emmagatzema, però al representar un volum tant gran, la seva presència queda diluïda, el que explica que sigui, entre els òrgans amb una concentració alta, el que té els nivells més baixos (André et al. 1991, Frodello et al. 2000).

 

Efecte de la localització geogràfica

Els dofins llistats del mediterrani presenten nivells de mercuri més elevats que els de l’Atlàntic i Pacífic (André et al. 1991, Leonzio et al. 1992, Augier et al. 1993, Monaci et al. 1998, Frodello et al. 2000, Cardellicchio et al. 2002b, Krishna et al. 2003, Roditi-Elasar et al. 2003, Pompe-Gotal et al. 2009). Tot i que les concentracions de mercuri trobades en dofí llistat al llarg del Mediterrani prenen valors similars, els nivells de mercuri més elevats es produeixen a la costa francesa, al mar de Liguria i al mar Tirrè, seguit per la costa adriàtica de Croàcia (Andre et al. 1991, Augier et al. 1993, Cardellicchio et al. 2000, Cardellicchio et al. 2002b, Pompe-Gotal et al. 2009). L’explicació més plausible és la proximitat als dipòsits de cinabri d’Itàlia central (Monaci et al. 1998, Cardellicchio et al. 2000, Cardellicchio et al. 2002b).

 

Efecte de l’edat i el sexe

El mercuri tendeix a acumular-se amb l’edat en organismes marins (André et al. 1991, Monaci et al. 1998, Roditi-Elasar et al. 2003), de manera que la seva taxa de creixement influencia el patró d’acumulació en les espècies, el que significa que també augmenta amb la longitud. El patró d’increment amb la longitud es pot explicar molt bé al múscul (Buffoni et al. 1982, Bernhard 1985): en els joves, com que creixen molt ràpid (d’1 m a 1,5 m en 6 mesos) la concentració augmenta poc per un efecte dilució; quan el creixement decreix, la concentració augmenta i quan s’atura als 2 m (12 anys) s’acumula en un volum constant i augmenta molt més ràpidament.

Per altra banda, no s’observa una influència significativa del sexe en la concentració de mercuri total als diferents òrgans (Monaci et al. 1998, Cardellicchio et al. 2002b).

 

REFERÈNCIES

  • Aguilar A (2000). Population biology, conservation threats and status of Mediterranean striped dolphins (Stenella coeruleoalba). J. Cetacean Res. Manage. 2:17-26
  • Andre J, Boudou A, Ribeyre F i Bernhard M (1991). Comparative study of mercury accumulation in dolphins (Stenella coeruleoalba) from French Atlantic and Mediterranean coasts. The Science of the Total Environment 104:191-209
  • Archer FI i Perrin WF (1999). Stenella coeruleoalba. Mammal. Species 603:1-9
  • Archer FI. Striped Dolphin (Stenella coeruleoalba). Encyclopedia of Marine Mammals. Perrin W, Würsig B i Thewissen JGM. 2ª edició. 1127-1129
  • Augier H, Park WK i Ronneau C (1993). Mercury Contamination of the Striped Dolphin Stenella coeruleoalba Meyen from the French Mediterranean Coast. Marine Pollution Bulletin 26:306-311
  • Bernhard M (1985). Mercury accumulation in a pelagic foodchain. In: Martell AE i Irgolic KJ (Eds), Environmental Inorganic Chemistry. VCH Publishers, Deerfield Beach, Florida, 349-358
  • Buffoni G, Bernhard M i Renzoni A (1982) Mercury in Mediterranean tuna. Why is their level higher than Atlantic tuna? A model. Thalassia Jugosl. 18:231-243
  • Cardellicchio N, Decataldo A, Di Leo A i Misino A (2002b). Accumulation and tissue distribution of mercury and selenium in striped dolphins (Stenella coeruleoalba) from the Mediterranean Sea (southern Italy). Environmental Pollution 116:265-271
  • Cardellicchio N, Giandomenico S, Ragone P i Di Leo A (2000).Tissue distribution of metals in striped dolphin (Stenella coeruleoalba) from the Apulian coast, Southern Italy. Marine Environmental Research 49:55-66
  • Frodello JP, Roméo M i Viale D (2000). Distribution of mercury in the organs and tissues of five toothed whale species of the Mediterranean. Environmental Pollution 108:447-452
  • Krishna D, Virginie D, Stéphane P i Jean-Marie B (2003). Heavy metals in marine mammals. In: Vos JV, Bossart GD, Fournier M i O’Shea T (Eds.) Toxicology of Marine Mammals. Taylor and Francis Publishers, Washington DC, 135-167
  • Leonzio C, Focardi S i Fossi C (1992). Heavy metals and selenium in stranded dolphins of the Northern Tyrrhenian (NW Mediterranean). The Science of the Total Environment 119:77-84
  • Monaci F, Borrl A, Leonzio C, Marsili L i Calzada N (1998). Trace elements in striped dolphin (Stenella coeruleoalba) from the western Mediterranean. Envirnmental Pollution 99:61-68
  • Otero MM i Conigliaro M (2012). Marine mammals and sea turtles of the Mediterranean and Black Seas. IUCN, 14
  • Pompe-Gotal J, Srebocan E, Gomercic H i Prevendar Crnic A (2009). Mercury concentrations in the tissues of bottlenose dolphins (Tursiops truncatus) and striped dolphins (Stenella coeruleoalba) stranded on the Croatian Adriatic coas. Veterinarni Medicina, 54(12):598-604
  • Roditi-Elasar M, Kerem D, Hornung H, Kress N, Shoham-Frider E, Goffman O i Spanier E (2003). Heavy metal levels in bottlenose and striped dolphins off the Mediterranean coast of Israel. Marine Pollution Bulletin 46: 504-512

 

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Mercurio en delfines listados (Stenella coeruleoalba) del Mediterráneo (I): origen y niveles

Después de semanas sin poder escribir una entrada elaborada sobre un tema de cetáceos, os dejo aquí ésta bastante extensa sobre el mercurio en los delfines listados del Mediterráneo. En concreto, trata sobre el origen y los niveles de mercurio en esta especie. En una segunda entrada se hablará del efecto tóxico y la detoxificación de este metal en esta especie. Espero que sea de vuestro interés.  

 

INTRODUCCIÓN

El delfín listado (Stenella coeruleoalba) es un delfínido pelágico pequeño común en aguas temperadas y tropicales de todo el mundo. La longitud mediana de los individuos del Pacífico oeste es de 2,4 metros en machos y de 2,2 m en hembras (Archer y Perrin, 1999), aunque los especímenes del Mediterráneo miden un 10% menos que éstos (Andre et al. 1991). Su dieta se compone principalmente de peces y calamares pelágicos y bentopelágicos (Archer 2009).

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Su rango de distribución es amplio (Archer 2009): se encuentra en el Pacífico Norte y Tropical; en el Atlántico, del norte de Sudamérica hasta a Norteamérica y en el Atlántico Noreste en aguas del Reino Unido; en el Índico; y en el Mediterráneo, donde es la especie más abundante. La figura siguiente muestra su rango de distribución en el Mediterráneo:

dist

Su estado de conservación a nivel global es de preocupación menor, pero en el Mediterráneo es vulnerable debido a la interacción accidental o no con la pesca (de palangre principalmente, Aguilar 2000), la contaminación y el cambio climático (Otero y Conigliaro 2012).

 

ORIGEN DEL MERCURIO DEL MEDITERRÁNEO

La fuente principal de las elevadas concentraciones de mercurio observadas en los organismos del Mediterráneo son depósitos naturales de mercurio de origen volcánico en muchas regiones de su cuenca, en forma de cinabrio (HgS) (André et al. 1991, Augier et al. 1993, Cardellicchio et al. 2000, Cardellichio et al. 2002b). Además, el uso del mercurio en actividades industriales podría contribuir a aumentar los niveles de mercurio en el mar (Cardellicchio et al. 2002b), aunque su efecto en delfines listados no parece que pueda ser importante por el hecho de ser una especie pelágica y raramente los encontramos cerca de la costa (a 10 km de la fuente, el mercurio vuelve a niveles de fondo, Andre et al. 1991).

 

NIVELES DE MERCURIO EN DELFINES LISTADOS DEL MEDITERRÁNEO

Distribución en los diferentes tejidos

La Tabla 1siguiente muestra la concentración media, la desviación y/o el rango de mercurio total (μg/g peso seco) en el hígado, riñón y músculo de delfines listados en varias localidades del Mediterráneo. Se han seleccionado estos tres órganos para hacer la comparativa porque son los que más se estudian en la bibliografía. De todos modos, hay que tener presente que la comparación de resultados de diferentes estudios se tiene que hacer con cuidado puesto que hay múltiples fuentes de variación como la condición, la edad y el sexo de los individuos, pero también con los métodos de toma de muestras y de medida. A pesar de que en esta tabla sólo constan tres órganos, el análisis siguiente se ha centrado en todos los órganos que han estudiado los diferentes autores mencionados.

  Hígado Riñón Músculo
  Mediana SD (rango) Mediana SD (rango) Mediana SD (rango)
Francia (Andre et al. 1991) 1472 131(4,4-392) 104 153(6,3-806) 63 131(4,5-365)
Francia (Augier et al. 1993) 481 587(68-2271) 62 88(14-341 37 40(7,4-155)
Costa de Apulia (Italia)(Cardellicchio et al. 2002b) 851 128(703-975) 46 9,7(34-59) 49 11(37-65)
Córcega (Frodello et al. 2000) 460 58 49 4 21 2
Tirreno Norte (Leonzio et al. 1992) 324 (13-4400) 65 (5,8-204) 37 (6,5-168)
Italia Oeste (Monaci et al. 1998) 593 1120 44 72 53 65
España (Monaci et al. 1998) 1043 835 63 100 28 73
Israel (Roditi-Elasar et al. 2003) 603 900(6,3-2475) 45 50(8,6-122) 40 32(2,0-95)

Tabla 1. Concentración de mercurio total (en μg/g peso seco) en el hígado, riñón y músculo de delfines listados (Stenella coeruleoalba) de varias localidades del Mediterráneo.

Como puede observarse en la Tabla 1, los niveles de mercurio en delfines listados del Mediterráneo son muy elevados, presentando la máxima concentración de mercurio en el hígado (Andre et al. 1991, Augier et al. 1993, Cardellicchio et al. 2002b, Frodello et al. 2000, Leonzio et al. 1992, Monaci et al. 1998, Pompe-Gotal et al. 2009, Roditi-Elasar et al. 2003). En otros mamíferos marinos, el hígado también es el órgano más contaminado (André et al. 1991, Augier et al. 1993). El segundo y tercer órganos con una concentración más elevada son el riñón y el músculo respectivamente. En los casos en que se ha estudiado la concentración de mercurio total en el pulmón (Augier et al. 1992, Cardellicchio et al. 2002b, Frodello et al. 2000), éste se ha situado como segundo órgano con la concentración más alta. De este modo, se puede deducir el siguiente orden en cuanto a la concentración de mercurio total en delfín listado por los cuatro órganos: hígado >> pulmón > riñón > músculo. Se han encontrado niveles insignificantes de mercurio en la piel, el melón, el blubber y el cerebro (Andre et al. 1991, Augier et al. 1993, Leonzio et al. 1992, Cardellicchio et al. 2002b, Frodello et al. 2000).

Este patrón en las concentraciones de mercurio se puede explicar por las vías de entrada y eliminación del metal en delfines. La elevada concentración en el hígado de los delfines listados del Mediterráneo se debe a que, una vez ingerido el mercurio a través del alimento (que es la vía de entrada principal en el organismo, Augier et al. 1993) o por ingestión de agua (Augier et al. 1993, Frodello et al. 2000), se transporta hasta el hígado y allí se detoxifica y se acumula  (Frodello et al. 2000, Krishna et al. 2003). La elevada concentración en los pulmones se puede explicar por su inhalación de la atmósfera (Cardellicchio et al. 2002b). El riñón, que almacena una fracción importante del metal, está involucrado en su eliminación, lo que explica que se encuentren valores intermedios. Finalmente, la concentración en el músculo se explica por el hecho de ser un tejido donde también se almacena, pero al representar un volumen tan grande, su presencia queda diluida, lo que explica que los niveles sean relativamente bajos.

 

Efecto de la localización geográfica

Los delfines listados del Mediterráneo presentan niveles de mercurio más elevados que los del Atlántico y Pacífico (André et al. 1991, Leonzio et al. 1992, Augier et al. 1993, Monaci et al. 1998, Frodello et al. 2000, Cardellicchio et al. 2002b, Krishna et al. 2003, Roditi-Elasar et al. 2003, Pompe-Gotal et al. 2009). A pesar de que las concentraciones de mercurio encontradas en delfines listados a lo largo de todo el Mediterráneo toman valores similares, los niveles más elevados se encuentran en la costa francesa, el mar de Liguria y el mar Tirreno, seguido por la costa adriática de Croacia (Andre et al. 1991, Augier et al. 1993, Cardellicchio et al. 2000, Cardellicchio et al. 2002b, Pompe-Gotal et al. 2009). La explicación más plausible es la proximidad a los depósitos de cinabrio de Italia central (Monaci et al. 1998, Cardellicchio et al. 2000, Cardellicchio et al. 2002b).

 

Efecto de la edad y el sexo

El mercurio tiende a acumularse con la edad en organismos marinos  (André et al. 1991, Monaci et al. 1998, Roditi-Elasar et al. 2003), de forma que su tasa de crecimiento influye el patrón de acumulación en las especies, lo que significa que también aumenta con la longitud. El patrón de incremento con la longitud se puede explicar muy bien en el músculo (Buffoni et al. 1982, Bernhard 1985): en los jóvenes, al crecer rápido (de 1 m a 1,5 m en 6  meses), la concentración aumenta poco por efecto dilución; cuando el crecimiento decrece, la concentración aumenta y cuando se para a los 2 m (12 años) se acumula en un volumen constante y aumenta mucho más rápidamente.

Por otro lado, no se observa una influencia significativa del sexo en la concentración de mercurio total en los diferentes órganos (Monaci et al. 1998, Cardellicchio et al. 2002b).

 

REFERENCIAS

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