Much of the U.S. just experienced the warmest spring on record, with temperatures shattering previous highs. On land, cherry trees bloomed early in Baltimore and Washington. Apple and peach trees blossomed prematurely in the Midwest. And in the Chesapeake Bay, algal blooms exploded early in the central and northern Bay.
“This is all part of a trend,” Dr. Donald Boesch, President of the University of Maryland Center for Environmental Science, said of the rising temperatures. “Nationally we have the warmest 12 month period, leading up to just last month, ever recorded in the United States. And we are breaking records continuously… It’s because of the greenhouse gas effect. We are emitting greenhouse gases and it’s warming the planet. That much the science is pretty clear on.”
Richard Batiuk, Associate Director for Science at the EPA Chesapeake Bay Program, said the early explosion of large “mahogany tides” (including of the algae prorocentrum minimum) this spring appear to have been accelerated by heat and an influx of nitrogen and phosphorus pollution flushed
off lawns, streets, and farm fields during Tropical Storm Lee last fall.
In a normal spring, on land, a procession of plants will flower as the temperatures warm –- with daffodils giving way to irises and then daylilies. The same thing happens in the water with a variety of algal species, which bloom under certain light and temperature and conditions, especially when the water becomes warmer than about 52 degrees Fahrenheit, according to Peter Tango, Chesapeake Watershed Monitoring Coordinator with the U.S. Geological Survey.
“That we had record warm water temperatures by several degrees earlier in the year, we would expect the biology, in this case the mahogany tides, might arrive earlier,” Tango wrote in an email.
Usually, algae bloom at the right time to feed spawning oysters, fish, and other critters. This year, however, the timing of the algal blooms appeared to be out of sync -– with some toxic species normally seen in May or June in the central and northern Bay instead erupting in February or March, Batiuk said.
“To see those blooms earlier, and the timing not really matched up with when we want to have the algae as good fish food out there, that’s a problem for the Chesapeake Bay,” Batiuk said.
The picture in the southern Chesapeake Bay this spring has been slightly different, with
only one relatively small bloom seen by Chesapeake Bay Foundation scientists in
Virginia so far. Parts of Virginia experienced heavy rains and a relatively cool late May and early June that may have created different conditions than in Maryland.
In general, warmer waters can’t hold as much oxygen as cooler waters. And algae blooms, when they rot and die, suck oxygen out of the water, which can kill young fish and oysters.
The stench of more than 100,000 dead menhaden and other fish fouled Memorial Day celebrations in Baltimore’s Inner Harbor and in several creeks in Anne Arundel County, Maryland, that feed the Patapsco River.
“Basically, there was this algal bloom, it used up the oxygen in the water,” said Dr. Richard Eskin, Director of the Science Services Administration at the Maryland Department of the Environment. “As the bloom died off, they decomposed and that decomposition uses up oxygen. And that’s what killed the fish. Obviously, they need oxygen to survive.”
The state agency recorded 32 fish kills through the first five months of the year in Maryland -– which was more than the 23 recorded over the same time period last year. However, the state in 2011 had a record low number of fish kills, stretching back to 1985. Compared to the historic average since that time, the winter and spring of 2012 actually saw about 20 percent fewer fish kills than is normal, according to state figures.
Scientists caution not to read too much into the fish kill numbers, because fish kills are an erratic indicator of water quality, with die-offs sometimes happening because of natural causes, such as spawning stress or overcrowding. And overfishing (for example, of menhaden in recent decades) means there are fewer fish -- which can also translate to fewer fish kills.
The big picture is that the Bay’s health has been improving slightly in recent years, with more crabs and striped bass, and less pollution from sewage plants, for example. But an overdose of runoff pollution -- combined with the destruction of wetlands, underwater grasses, and oyster reefs
that clean the Bay’s waters -– has made the Chesapeake’s health fragile.
There is only a limited amount we can do to control the weather. But there is a lot we can do -- right now -- to control runoff pollution. And the most important way we can do that is by defending and implementing EPA's new pollution limits for the Chesapeake Bay, which call for a 25 percent reduction in pollution from all sources by 2025.
By Tom Pelton
Chesapeake Bay Foundation
(Photo from Chesapeake Bay Program)