As an expert in aquatic biology, I can tell you that dissolved oxygen (DO) in water is generally considered to be good for aquatic life. It is essential for the respiration of fish and other aquatic organisms. However, the levels of DO that are beneficial can vary among different species. Too little dissolved oxygen can lead to stress and even death for aquatic life, while too much can cause a condition known as supersaturation, which can lead to gas bubble disease. This disease can cause physical damage to the gills and other tissues of fish, as the excess gas forms bubbles that can be harmful. In the context of your reference, it seems to suggest that while adequate dissolved oxygen is necessary for good water quality, levels that are too high can be problematic. It's a delicate balance that is crucial for maintaining a healthy aquatic ecosystem. read more >>

External bubbles (emphysema) can also occur and be seen on fins, on skin and on other tissue. Aquatic invertebrates are also affected by gas bubble disease but at levels higher than those lethal to fish. Adequate dissolved oxygen is necessary for good water quality.read more >>