40,000-Acres Seagrass Dieoff Now Underway In Florida Everglades; Bonus! H2S AND Algae Blooms

EVERGLADES NATIONAL PARK, Florida — The shallow coastal waters of Florida Bay are famed for their crystal clear views of thick green seagrass – part of the largest stretch of these grasses in the world.

But since mid-2015, a massive 40,000-acre die off here has clouded waters and at times coated shores with floating dead grasses. The event, which has coincided with occasional fish kills, recalls a prior die-off from 1987 through the early 1990s, which spurred major momentum for the still incomplete task of Everglades restoration. “It actually started faster as far as we can tell this year,” said James Fourqurean, a Florida International University marine scientist who studies the system. “In the 80s, it continued to get worse for 3 years.”

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Flows through Shark River Slough, which feeds water to the Everglades and eventually Florida Bay, plunged to just 200,000 acre-feet in 2015. That’s just a quarter of standard annual flows, which themselves are less than half of historic flows of 2 million acre-feet per year before major projects blocked and redirected the Everglades’ water. The center of the bay then heated up last summer, saw considerable evaporation, and became quite salty – for some parts of the bay, twice as salty as normal sea water.

“It’s a really delicate balance between how much freshwater comes in each year, how much rainfall falls, and then how much evaporation occurs,” Johnson said. “In the absence of rainfall, salinity takes off in the bay, and we get a lot of harmful impacts of that.” In very salty conditions, waters hold little of the oxygen that sea grasses need to live. At the same time, other marine organisms turn to a different “anoxic” process – one that goes forward without oxygen – that has a nasty by-product: hydrogen sulfide.

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https://www.washingtonpost.com/news/energy-environment/wp/2016/04/27/this-unprecedented-event-has-now-happened-twice-massive-seagrass-die-off-hits-florida-bay/