Yes dolphins do poop or release feces or excrement depending on how you’d like to phrase it.
In fact all species release toxic waste from their bodies in one way or another; however pooping is one of the most common ways to remove toxic waste and non nutrient matter from the body.
As dolphins consume fish and other sources of food their body needs to break down the food and separate the nutrients from the waste in order to the excrete toxic substances from the body while also allowing the body to receive the proper nutrients it needs to be healthy.
This waste makes its way through the dolphin’s anal tract and comes out as poop.
When a dolphin poops or releases its excrement the dolphins poop comes out as an almost liquid like form of fecal matter (often in a plum like cloud) which is light enough to float across the top of the sea water.
Dolphin poop is very important for the oceans ecosystem (up to 50% of an animals poop may contain a large amount of energy) and for the healthy growth and production of variety of organisms such as phytoplankton and/or fish that survive off of eating these organisms.
Studies detailing the effects of how sperm whale poop affects phytoplankton have shown that as phytoplankton grows from the nutrients found in sperm whale poop it pulls more and more carbon from the atmosphere cleaning up the environment and creating a healthier ecosystem for both land and oceanic animals.
While not as much information has been collected regarding the effects of dolphin poop in regards to how it affects the oceans ecosystem there is a good possibility that dolphin poop may serve a similar role/function in maintaining the balance of the oceans ecosystem and aquatic life.