tropical cyclone observation
...that coral within tropical oceans is being used as a tropical cyclone observation to date past hurricanes, by looking for concentrations of the oxygen isotope O-18?
...that coral within tropical oceans is being used as a <b id="mwCs4"><a href="./Tropical_cyclone_observation" id="mwCs8" rel="mw:WikiLink" title="Tropical cyclone observation">tropical cyclone observation</a></b> to date past hurricanes, by looking for concentrations of the oxygen isotope <a href="./Oxygen-18" id="mwCtA" rel="mw:WikiLink" title="Oxygen-18">O-18</a>?