Many marine organisms contribute to the ocean's carbon cycle, but few have as complex an influence as coccolithophores. These single-celled algae construct intricate calcium carbonate shells, a process that absorbs dissolved carbon from surrounding waters. Under standard assumptions, this shell formation should act as a net carbon sink, helping to mitigate atmospheric carbon dioxide levels. However, the biochemical reaction that produces calcium carbonate also releases dissolved carbon dioxide back into the water column. Consequently, coccolithophores can actually function as net carbon sources under certain ecological conditions, complicating models that predict how marine ecosystems respond to global climate shifts.
Which choice best describes the function of the underlined sentence in the text as a whole?
- AIt presents empirical data supporting the claim that shell formation is the primary driver of oceanic carbon absorption.
- It outlines a widely accepted assumption about coccolithophores' ecological role that the subsequent sentences go on to qualify.Cevap
- CIt summarizes the overall conclusion of the passage regarding how marine organisms adapt to changing ocean conditions.
- DIt proposes a speculative explanation for algae behavior that the author later demonstrates to be entirely incorrect.