वैज्ञानिकों ने खोजा ‘भूत’ जीवाश्म – ‘पूरी तरह से अप्रत्याशित’

उप-माइक्रोन-स्केल संरचनाओं (दाएं) के उल्लेखनीय संरक्षण को दिखाने के लिए छवियां प्राचीन कार्बनिक पदार्थ (बाएं) के एक टुकड़े की सतह पर एक ढह गई कोशिका भित्ति (कोकोस्फीयर) को अलग-अलग प्लेटों के साथ आवर्धित (कोक्सीक्स) दिखाती हैं। नीली छवि को एक आभासी जीवाश्म छवि देने के लिए उल्टा किया जाता है, यानी मूल 3D आकार दिखाने के लिए। मूल स्लैब को भंग करके तलछट से हटा दिया गया था, केवल भूतों के निशान को पीछे छोड़ दिया। श्रेय: एस.एम. स्लेटर, पी. बोवेन/साइंस जर्नल

शोधकर्ताओं की एक अंतरराष्ट्रीय टीम ने एक नए प्रकार के जीवाश्म की खोज की है।

‘भूत’ जीवाश्मों की खोज से पिछले ग्लोबल वार्मिंग की घटनाओं के सामने प्लवक के लचीलेपन का पता चलता है।

यूनिवर्सिटी कॉलेज लंदन (यूसीएल), प्राकृतिक इतिहास के स्वीडिश संग्रहालय, प्राकृतिक इतिहास संग्रहालय (लंदन) और फ्लोरेंस विश्वविद्यालय के वैज्ञानिकों की एक अंतरराष्ट्रीय टीम ने एक उल्लेखनीय प्रकार का जीवाश्म पाया है जो अब तक लगभग किसी का ध्यान नहीं गया है।

जीवाश्म सूक्ष्म उंगलियों के निशान हैं, या एकल-कोशिका वाले प्लवक के “भूत” हैं, जिन्हें कोकोलिथोफोरस कहा जाता है, जो लाखों साल पहले समुद्र में रहते थे, और उनकी खोज ने हमारी समझ में क्रांति ला दी कि जलवायु परिवर्तन महासागरों में प्लवक को कैसे प्रभावित करता है।

यॉर्कशायर में जुरासिक चट्टानों से भूत नैनोफॉसिल

यॉर्कशायर, यूके में जुरासिक चट्टानों से भूत नैनो-जीवाश्म। क्रेडिट: एस.एम. स्लेटर एट अल।

Coccolithophores आज के महासागरों में महत्वपूर्ण हैं, जो हम सांस लेते हैं, उनमें से अधिकांश ऑक्सीजन प्रदान करते हैं, समुद्री खाद्य जाले का समर्थन करते हैं, और कार्बन को समुद्री तल तलछट में फँसाते हैं। वे एक प्रकार के सूक्ष्म प्लवक हैं जो अपनी कोशिकाओं को कठोर चूना पत्थर के स्लैब से घेरते हैं, जिन्हें कोकोलिथ कहा जाता है, जो आमतौर पर चट्टानों में विघटित होते हैं।

इन जीवाश्मों की प्रचुरता में कमी को कई पूर्व-ग्लोबल वार्मिंग घटनाओं से प्रलेखित किया गया है, यह दर्शाता है कि ये प्लवक जलवायु परिवर्तन और समुद्र के अम्लीकरण से गंभीर रूप से प्रभावित हुए हैं। हालांकि, आज जर्नल में एक अध्ययन प्रकाशित हुआ विज्ञान तीन के प्रचुर मात्रा में भूत जीवाश्मों के लिए नए विश्व रिकॉर्ड प्रस्तुत करता है[{” attribute=””>Jurassic and Cretaceous warming events (94, 120, and 183 million years ago), suggesting that coccolithophores were more resilient to past climate change than was previously thought.

Modern and Jurassic Coccolithophore Exoskeletons (Coccospheres)

The individual plates are coccoliths. Credit: Images from Nannotax https://www.mikrotax.org/Nannotax3/

“The discovery of these beautiful ghost fossils was completely unexpected,” says Dr. Sam Slater from the Swedish Museum of Natural History. “We initially found them preserved on the surfaces of fossilized pollen, and it quickly became apparent that they were abundant during intervals where normal coccolithophore fossils were rare or absent – this was a total surprise!”

Despite their microscopic size, coccolithophores can be hugely abundant in the present ocean, being visible from space as cloud-like blooms. After death, their calcareous exoskeletons sink to the seafloor, accumulating in vast numbers, and forming rocks such as chalk.

Ghost Nannofossils With Virtual Casts

The fossils are approximately 5 µm in length, 15 times narrower than the width of a human hair. Credit: S.M. Slater, P. Bown et al. / Science journal

“The preservation of these ghost nannofossils is truly remarkable,” says Professor Paul Bown (UCL). “The ghost fossils are extremely small ‒ their length is approximately five-thousandths of a millimeter, 15 times narrower than the width of a human hair! ‒ but the detail of the original plates is still perfectly visible, pressed into the surfaces of ancient organic matter, even though the plates themselves have dissolved away.”

The ghost fossils formed while the sediments at the seafloor were being buried and turned into rock. As more mud was gradually deposited on top, the resulting pressure squashed the coccolith plates and other organic remains together, and the hard coccoliths were pressed into the surfaces of pollen, spores, and other soft organic matter. Later, acidic waters within spaces in the rock dissolved away the coccoliths, leaving behind just their impressions – the ghosts.

Ghost Nannofossils Were Found in Rocks From Global Warming Intervals

Ghost nannofossils were found in rocks from global warming intervals where normal coccolithophore fossils were rare or absent. Credit: S.M. Slater, P. Bown, et al. / Science journal

“Normally, paleontologists only search for the fossil coccoliths themselves, and if they don’t find any then they often assume that these ancient plankton communities collapsed,” explains Professor Vivi Vajda (Swedish Museum of Natural History). “These ghost fossils show us that sometimes the fossil record plays tricks on us and there are other ways that these calcareous nannoplankton may be preserved, which need to be taken into account when trying to understand responses to past climate change.”

Professor Silvia Danise (University of Florence) says: “Ghost nannofossils are likely common in the fossil record, but they have been overlooked due to their tiny size and cryptic mode of preservation. We think that this peculiar type of fossilization will be useful in the future, particularly when studying geological intervals where the original coccoliths are missing from the fossil record.”

Ghost Nannofossils Were Found Globally

Ghost nannofossils were found globally, in rocks from three rapid warming events in Earth’s history (the T-OAE, OAE1a, and OAE2). Credit: S.M. Slater et al.

The study focused on the Toarcian Oceanic Anoxic Event (T-OAE), an interval of rapid global warming in the Early Jurassic (183 million years ago), caused by an increase in CO2-levels in the atmosphere from massive volcanism in the Southern Hemisphere. The researchers found ghost nannofossils associated with the T-OAE from the UK, Germany, Japan, and New Zealand, but also from two similar global warming events in the Cretaceous: Oceanic Anoxic Event 1a (120 million years ago) from Sweden, and Oceanic Anoxic Event 2 (94 million years ago) from Italy.

“The ghost fossils show that nannoplankton were abundant, diverse, and thriving during past warming events in the Jurassic and Cretaceous, where previous records have assumed that plankton collapsed due to ocean acidification,” explains Professor Richard Twitchett (Natural History Museum, London). “These fossils are rewriting our understanding of how the calcareous nannoplankton respond to warming events.”

Finally, Dr. Sam Slater explains: “Our study shows that algal plankton were abundant during these past warming events and contributed to the expansion of marine dead zones, where seafloor oxygen-levels were too low for most species to survive. These conditions, with plankton blooms and dead zones, may become more widespread across our globally warming oceans.”

Reference: “Global record of “ghost” nannofossils reveals plankton resilience to high CO2 and warming” by Sam M. Slater, Paul Bown, Richard J. Twitchett, Silvia Danise and Vivi Vajda, 19 May 2022, Science.
DOI: 10.1126/science.abm7330

READ  शोधकर्ता तेजी से रेडियो फटने के स्रोत पर ध्यान केंद्रित करते हैं

प्रातिक्रिया दे

आपका ईमेल पता प्रकाशित नहीं किया जाएगा.