Splitting Seurat object creates massive increase in object size

[mesposit]

Hi everyone,

I have a merged Seurat object that contains data from 32 individual samples, in total there are ~200K cells in this object. The size of this object is 19.3GB.

When working with rather large data sets, I often split them up to be able to try something with only one sample or to be able to iterate through my list of samples.

So I usually just do seu_list <- SplitObject(seu, split.by = "sample") which has worked perfectly fine in the past. But for some reason with this particular object, when I do this the size of the resulting list goes up to 225.8GB.

I checked unique(seu$sample) which tells me that I really only have 32 unique sample names in my object meta data and also the resulting list of Seurat objects only has 32 elements.

Does anyone have an idea why the size increases so dramatically and how I could solve this?

I am using Seurat version 5.2.1, please let me know if my full session info is needed to troubleshoot this.