Hi, How are y'all on this find morning? What does the author mean when he says he has “truly seen the light and dark of the Antarctic”?

Here's the article.

Emerging back into the light at the surface, the bubbles of the submarine hull clearing, it was like waking from a dream, the creatures of the ocean deep left far behind.

I had truly seen the light and the dark of the Antarctic. At its surface, penguin colonies stretch for miles on snow-capped islands, with millions of breeding pairs across the region, raising their chicks in this difficult environment. Enormous whales' surface all around, feeding on huge pink clouds of the small shrimp-like krill, which nearly all wildlife here relies on. Fur seals and elephant seals lounge on drifting blocks of ice. While below, another world goes on existing in the dark.