The water in Baltimore’s Inner Harbor is giving off a very fishy odor. Wondering why? If nutrient levels are high enough, warming waters can sustain increased numbers of microscopic plants or algae. Nutrient runoff from our recent spring rains fueled a brown algae bloom in the inner harbor giving the water a mahogany color last week. Algae has a short life span, and as it dies oxygen is consumed and is no longer available for other organisms in the water column. At this point, fish and other animals that cannot escape the low oxygen zones die. These are commonly referred to as “dead zones” which cause fish kills, and the bad smell over the weekend. The bacteria then devours the dead fish killed by oxygen depletion, fueling more bad odors.
Some animals, like jellies require very little oxygen and manage to live through these dead zone events. This is part of the reason jellies populations are thriving in bodies of water around the world.
These excess nutrients that cause the algae blooms can come from a variety of sources including fertilizer, storm water runoff, and even atmospheric deposition. So what can be done about it? The National Aquarium is actively working to improve the water quality of the Bay by restoring vital habitats like tidal wetlands. These habitats remove excess nutrients, help prevent flooding and provide important habitat to the animals that live there. You can volunteer – check it out!