{
  "id": 11978659,
  "title": "One giant clam contains a month‑by‑month diary of the Great Barrier Reef's climate 200 years ago",
  "url": "https://urgent.news/2026/10/04/one-giant-clam-contains-a-month-by-month-diary-of-the-great-barrier",
  "topic": "science",
  "section": "Science",
  "published": "2026-10-04T18:00:01.000Z",
  "source": {
    "name": "Phys.org",
    "slug": "phys-org",
    "url": "https://phys.org/news/2026-09-giant-clam-monthbymonth-diary-great.html"
  },
  "original_language": "en",
  "account": "The world's largest living bivalve, Tridacna gigas, known as the giant clam, possesses an extraordinary ability to record its environment. Throughout its life, each day is inscribed in its shell, creating a unique diary of the sea's conditions. In a groundbreaking study published in Global and Planetary Change, researchers analyzed a giant clam shell from the Lizard Island Group in the northern Great Barrier Reef. This shell belonged to a clam that lived between 1785 and 1827, during a period known as the Little Ice Age. The researchers meticulously counted the daily growth lines, which totaled nearly 10,900, demonstrating that the clam lived for approximately 30 years. The shell's composition and structure yielded crucial insights into the preindustrial climate. The oxygen isotopes in the shell provided estimates of past sea temperatures, while the carbon isotopes offered clues about rainfall patterns. By correlating these chemical clues with the shell's growth structure, the researchers reconstructed a month-by-month picture of the reef environment. The findings revealed that average sea temperatures were significantly cooler than today's, with annual temperatures being 0.6–0.9°C lower and summer temperatures 0.9–1.2°C cooler. Importantly, winter temperatures remained remarkably similar to modern levels. This unique climate record, combined with other evidence from corals, Antarctic ice, and other global archives, paints a comprehensive picture of the Southern Hemisphere's climate during this period. The research highlights the importance of local climate records, as cooler temperatures and shifts in ocean conditions observed at Jiigurru were not uniform across all regions. This study underscores the value of giant clam shells as a rich source of climate data, potentially revealing additional chapters in the story of Earth's climate.",
  "summary": "When you swim through the azure waters of the Great Barrier Reef, there is one creature on the seafloor that's almost impossible to miss: the giant clam. Its huge, fluted shell frames a soft mantle shimmering with electric blue, green and gold.",
  "key_points": [
    "Giant clam shell records climate for 30 years (1785-1827)",
    "Oxygen isotopes reveal past sea temperatures 0.6-0.9°C lower",
    "Carbon isotopes provide clues about rainfall patterns"
  ],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}