{"id":11579800,"date":"2025-07-28T05:00:25","date_gmt":"2025-07-28T09:00:25","guid":{"rendered":"https:\/\/www.baltimoresun.com\/?p=11579800&preview=true&preview_id=11579800"},"modified":"2025-07-28T05:00:49","modified_gmt":"2025-07-28T09:00:49","slug":"hopkins-researching-danger-level-of-foul-pistachio-tides-on-magothy-river","status":"publish","type":"post","link":"https:\/\/www.baltimoresun.com\/2025\/07\/28\/hopkins-researching-danger-level-of-foul-pistachio-tides-on-magothy-river\/","title":{"rendered":"Hopkins researching danger level of foul \u2018pistachio tides\u2019 on Magothy River"},"content":{"rendered":"

Greenish, cloudy, and with a smell like rotten eggs, “pistachio tides” are causing concern among residents who live along the Magothy River.<\/p>\n

Magothy River Association member Bob Moyer said he went out to photograph a particularly large pistachio tide on Cattail Creek in October, and was so overwhelmed by the sulfur smell that he collapsed to his hands and knees and had to crawl\u00a0off the pier.<\/p>\n

Pistachio tides occur when bacteria in the river produce hydrogen sulfide, which depletes the oxygen in the water and creates a rotten smell. The bacteria produce a bright green color, which is where the name comes from.<\/p>\n

Working with the river association, Johns Hopkins University is researching the bacterial booms in Cattail and Old Man creeks this summer to identify where and when they occur. Pistachio tides usually develop between August and October, and Hopkins started collecting water samples in early July to get ahead of the blooms.<\/p>\n

Paul Spadaro, president of the Magothy River Association, is concerned about people breathing in the sulfur, especially on Cattail Creek, where recreational activity often takes place. Without any monitoring or warning system, kayakers may paddle into a pistachio tide.<\/p>\n

\u201cI do think people need to know that when you smell that sewer gas, it\u2019s time to move away,\u201d Spadaro said.<\/p>\n

Part of Hopkins’ research this summer is to determine if there is a danger to wildlife or humans. Sulfur bacteria are naturally occurring, but stormwater and fertilizer runoff entering the creek can increase the pervasiveness of these bacteria by depleting oxygen.<\/p>\n

In October, Spadaro said 380 fish in the Town Neck region of Cattail Creek were found dead during the pistachio tides. In September, a bloom in Baltimore\u2019s Inner Harbor killed 24,000 fish<\/a>. The Department of Natural Resources deploys continuous monitoring of these blooms in the Inner Harbor.<\/p>\n

“It\u2019s the sulfur bacteria\u2019s appetite for oxygen that makes it dangerous to fish, crabs, eels, and other aquatic life that need dissolved oxygen to breathe,” said DNR program manager Cathy Wazniak.<\/p>\n

However, Wazniak said that without long-term data on pistachio tides in the Chesapeake Bay, she could not say whether any trends exist.<\/p>\n