SCCF Water Quality & Beach Report

Date: Fri Jun 5, 2009 2:20 pm ((PDT))


June 5, 2009

SCCF Water Quality & Beach Report

Sun-bleached manatee grass washes up on Sanibel and Captiva beaches
At the end of May and into this week, piles of what looked like spaghetti
washed up on beaches from Naples to Sarasota. SCCF Marine Lab Director, Dr.
Loren Coen and Research Scientist, Dr. Rick Bartleson, identified the
substance as dead shoots of Manatee Grass (Syringodium filiforme). Our Lab
has been in touch with other groups to help evaluate the event, including
the Town of Fort Myers Beach, City of Sanibel, Florida Gulf Coast University
and Mote Marine Laboratory.

As of Thursday, it was still thick at Bowman’s Beach and floating offshore
from Tarpon Bay Beach to the Clam Bayou area. There have been no fresh
accumulations on Captiva. Mote Marine reported that it was very abundant on
Casperson Beach, and on beaches north of Venice but there had been no
reports of large amounts of fresh material coming onshore there.
Photo above taken on June 4 shows the dried manatee grass (white), freshly
washed in (beige) and manatee grass in the water) breaking wave and out a
little).  Photo right show healthy and dead shoots.

The manatee grass washing up does not pose a nutrient concern because
nitrogen and other organic content has already leached from the shoots as
they decomposed in the Gulf.  Living seagrass blades are green, but they
turn white after they die and bleach as they float in the Gulf.

While the manatee grass is harmless on the beach, anytime that seagrasses in
this volume wash up, it’s a concern and SCCF will be working with colleagues
up and down the coast to look at potential causes.

For more information, please visit our web site.  If you want to read some
of the local press:
Link to the June 2 News-Press story
Link to the June 2 Naples Daily News story


Hypoxic Zone in Caloosahatchee
On June 4, SCCF’s RECON sensor at Fort Myers detected a low oxygen zone,
also known as hypoxia, in the Caloosahatchee, with DO (dissolved oxygen)
levels below 2 milligrams/liter.  If DO concentrations fall below 3
milligrams per liter, mobile animals will move to areas with higher DO
concentrations. Sardines die when concentrations fall to 2.2 milligrams per
liter. Hypoxic (very low oxygen) conditions occur when DO falls below 2
milligrams per liter and many species are affected. Anoxia (no oxygen) is a
term for when there is no dissolved oxygen and most organisms die.

The Caloosahatchee experienced hypoxic zones last summer, following Tropical
Storm Fay, which delivered record volumes of freshwater into the river.