microbiology - What does "cellular" mean in this context?

I came across a confusing word when I was reading a Scientific American story, “Controversial Spewed Iron Experiment Succeeds as Carbon Sink” (by David Biello). It goes like this:

“One key to the whole experiment’s success turns out to be the
specific diatoms involved, which use silicon to make their shells and
tend to form long strands of cellular slime after their demise that
falls quickly to the seafloor.”

I'm wondering what “cellular” means in this context. Does it mean “of (diatom) cells” or “porous”?

Could someone kindly enlighten me on this?