Use of Datapump Import Leads to Streams Memory Issue

I recently used the datapump export and import utilities to to reduce the number of rows in two tables. I exported all rows but on the import I used the query parameter to select only about half of the original rows. Both the export and import ran fine.

About forty-five minutes later, and again fifteen minutes after that, the background process MMON experienced waits in the category "Streams AQ: enqueue blocked on low memory". The waits lasted about seven minutes each time. About twenty-four hours later MMON experienced an identical period of wait.

We do not use streams in this database, but I have been told that datapump does use streams.