Complex sentence: They suck in water and filter out the plankton and detrius to swallow, then spit the water back out, thus cleaning the water around them and getting rid of much of eastern Chesapeake Bay's notorious water polution.
Split into simpler sentences: They suck in water and filter out the plankton and detrius to swallow. Then they spit the water back out; thus, cleaning the water around them and getting rid of that vicinity's water polution.