"Mahogany tides" seen in the bay
It isn't just Baltimore's Inner Harbor that's been plagued lately with fish-killing algae blooms. Scientists with the Department of Natural Resources say they've been seeing "extensive algal blooms" this month across Maryland's portion of the Chesapeake Bay.
The scientists say they've detected especially high concentrations of Prorocentrum minimum, a type of algae with little whiplike arms that enable it to move in the water. Here's a blown-up image of one cell, courtesy of DNR. Scientists say this year's big blooms covering vast stretches of the bay likely have been sparked by unusually heavy runoff of fertilizer and other nutrients during this wet spring. Though generally considered not toxic, these blooms can kill fish by consuming all the oxygen in the water when they die and decay. That's the same type of algae found in the harbor earlier this week, along with more than 3,000 dead fish, mostly menhaden.
Such blooms also can stunt the growth of beneficial bay grasses, discoloring the water and blocking out sunlight needed by the underwater vegetation. A similar surge in 2000 led to a die-back of bay grasses in the mid-bay, according to DNR. It would be unfortunate if that happened again, as bay grasses have been spreading and growing thicker lately. The grasses are important nursery and shelter for crabs and fish, and they're considered a basic indicator of the bay's health.
The good news, probably, is that Prorecentrum blooms tend to dissipate after May, so DNR scientists say. Go here to see a map showing where harmful algal blooms have been spotted so far this year around the bay. Go here to learn more about the blooms.