When in doubt, go with the subject. Or you can rephrase it in the plural.
'The major sound scatterers in hydrothermal plumes are temperature fluctuations.'
Student or Learner
I want to know if I should use 'is' or 'are' in the following sentence and why.
'The major sound scatterer in a hydrothermal plume is/are temperature fluctuations.'
I think 'is' is correct since the subject 'the major sound scatterer' is singular. However, there is another voice in my mind saying I should use 'are' since the object 'temperature fluctuations' are plural.
Or Temperature fluctuations are the major sound scatterers in hydrothermal plumes.