"This is my family's favorite way for using leftover salmon. We came up with it once based on what we liked and what we had in the fridge, and kept making it ever since. It makes a healthy, yummy, low-fat dish that is quick and easy to prepare. Serve garnished with shredded cucumber or fresh cilantro."
Pour water into a large pot. Add celery, carrots, potatoes, onion, and ginger to the water; season generously with salt and pepper. Bring the water to a boil, reduce heat to medium-low, and cook at a simmer until carrots are tender, about 10 minutes. Stir turnip greens and soy sauce into the soup; cook until greens wilt, about 5 minutes.
Stir spaghetti into the simmering mixture; cook until the pasta is just beginning to soften, about 10 minutes. Add salmon and lemon juice to the liquid. Remove pot from heat and let salmon steep in the soup until warmed, about 5 minutes.