Write a summary (2 - 3 paragraphs) that describes O16 vs O18 behavior in warmer and colder global temperatures. Include a description of how that difference is recorded in forams (sea shells) vs. ice cores.

•Oxygen is one of the most important keys to understanding past climatic conditions. Oxygen comes in heavy and light grades or isotopes useful for post-research meat. Like all elements, oxygen consists of nuclei of protons and neutrons surrounded by a cloud of electrons. Each oxygen atom has 8 protons, but the nucleus can contain 8, 9, or 10 neutrons. Oxygen-16 "light", which has 8 protons and 8 neutrons, is the most abundant isotope in nature, followed by much less than "heavy" oxygen-18, which has 8 protons and 10 neutrons.

•The most valuable fossils in mud nuts come from small animals with calcium carbonate shells called foraminifera. The foraminifera species lives in arctic icy waters near Iceland and Antarctica. As part of an ongoing research project, McManus and other scientists found the water was much colder when they began discovering large numbers of polar maggot fossils in cores collected off the coast of England. After the fossils were dated, they told scientists when the sea was very cold. By looking for cold water larvae of the same age elsewhere in the ocean, scientists can create maps showing the presence of cold water at different times in Earth's history.

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