I won't describe in much detail the geology and astronomy of the world I'm creating here, whose unnatural shape and so far unexplained non-Einsteinian large-scale mechanics to maintain it may not be truly relevant (and I could ask about in another question).
Suffice to say, in this world, you have extremely slow seasonal changes with one cycle lasting about ten thousands years, give or take one or two millennia. During the winter, there is no sunlight of the surface at all and during the millennia before and after, very little sunlight. Note the duration of the winter can be adjusted, but we'd like it to be superior to 400 years long.
The world has some negative curvature, and in such places, you can see part of the distant world in the night sky. Also, the cold winter seas are often connected to warm summer oceans, being a big body of water exposed to the sun or not by two different surfaces.
What strategies could an ecosystem use to live through the winter? By "survive", I do not mean "preserve". A large part of the life can die off. But some portion of it would be able to seasonally adapt to the winter until the spring. A sub-portion need not to be active during winter, just be ready to bloom/hatch/awaken in the spring.
Note: this is similar to this question, How could a small fantasy world survive hundreds of years of darkness?, but I'm asking in a general non-fantasy-magic setting for the entire ecosystem (but not 100% accurate to reality).