Friday, July 22, 2011

Jellyfish: Missing in Action

A few weeks ago I blogged the expected arrival of Sea Nettles to our Bay.  However, as of yet, the dreaded Sea Nettle has not put in an appearance.  Low from the heavy rains in late Spring are likely the cause:
Normally by this time, the rangers at Sandy Point State Park have put out their warning sign about jellyfish. Complaints of jellyfish sightings and stings typically start coming the weekend after Independence Day.

"You can almost set your calendar by it," said Ranger Mike Travers, who is in charge of the beach and lifeguards.

But record-low salinity levels in the Chesapeake Bay- and possibly other factors - have kept jellyfish away.

The jellyfish count at Sandy Point is zero.

So, where are they?

Maggie Sexton has some possible answers.

Sexton, of the University of Maryland Center for Environmental Science in Cambridge, studies jellyfish populations and distribution. Most years, jellyfish have shown up by now, she said.

"I'm really surprised that we're not seeing at least a handful," Sexton said. "It's curious, but it's not shocking quite yet."

What would be shocking to Sexton is if the jellyfish don't show up in the next three weeks or so.

The most obvious factor in the absence of jellyfish is salinity.

Jellyfish prefer water much saltier than that in the Chesapeake right now. Sexton said peak jellyfish populations tend to happen when salinity is between 12 and 16 parts per thousand.

A monitoring station at the Bay Bridge shows salinity of 7.1 parts per thousand for July - below last year's 11.2 and below the average of 9.01 for this time of year.
This is low salinity is a mixed blessing.   The lack of Sea Nettles makes wading and swimming in the Bay much more enjoyable.  However, it also brought with it a big slug of nutrients, which is working its way through the system and making it a bad year for anoxic bottom waters, the so called "dead zone"  (It's not dead - some bacteria love it!). Low salinity appears to be make it easier for the dreaded Northern Snakehead to move to new habitats around the Maryland portion of the bay (although I wouldn't necessarily claim that the Rhode River Snakehead got there this year).  I think it has also affected the fishing, for the worst, at least in my region.

1 comment:

  1. I had a report of a jellyfish at Calvert Beach on Monday. I didn't see any myself on Tuesday and after the storms Tues nite, Without serious wading, I couldn't cross either creek on Weds and Thurs. I declared it too hot and humid this morning.