The title helps unlock this tiny poem. "Lotic" describes flowing water, like a river or stream, as opposed to still water like a pond. So the speaker is joining forces with something that never stops moving.
The "one-way creed" is a belief or rule with no turning back: rivers run downstream, and so do human lives. The speaker and the river become allies because they share that direction. Then the three short lines shift the idea inward. The speaker is "a body," and a body is also "water," which is true in a very literal sense. The last line is the surprise: "mother to ice." Water can freeze and give rise to something solid and still, so it can be a parent to its own opposite.
The mood is calm, compact and a little awed. The speaker sounds accepting rather than afraid, content to be part of a cycle of change. The poem suggests that flowing, freezing and perhaps ending are all part of the same process.