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Good morning everyone, it’s very nice to
be here and take part in this meeting. I admit was not familiar with this
organization in the past and I’m especially glad of course that the
organization is interested in the invasive species issue. I’m sure some to many of you have dealt with
invasive species up-close and personal and probably wish the issue would go
away. So do I.
Just as background, according to Dr.
James Carlton, an expert in exotic introductions, no systematic studies have
been done on the nonindigenous marine invertebrates of Florida. Because Tampa
is a busy shipping port, it would be advantageous to systematically examine
the exotics there and around the the rest of the coast of Florida as
well. I’m sure you are well aware of
how important it is to have baseline data so you have something to compare new
data or data collection in the future to.
Again according to Dr. James Carlton, no
marine organism, once established, has ever been successfully removed or
eradicated in the US. New introductions can cause problems for native species
such as predation, competition, disturbance, and diseases and parasites. There now may be an exception, an exotic
sabellid worm which was devastating abalone population on the West Coast. A localized population was eliminated below
the detection level by eliminating the intermediate host.
This is the mussel we are talking about,
Perna viridis. It is aptly named the green
mussel and is in the family Mytilidae along with other edible mussels that we
are more familiar with like the blue mussel Mytilus edulis that you see on restaurant
Green mussels first observed at TECO’s Gannon power station July 15, 1999 in the
seawater intake system.
Perna viridis collected from TECO Gannon Plant October 13, 1999.
Photographed November 4, 1999 in
a Tank at Mote Marine
According to biologists at Mote,
the mussels moved across
the sediment and climbed the piece of wood.
There are 3 species of Perna
worldwide. Shell color can be variable
in them all. They all used to be
geographically isolated, location was used to tell them apart. Location of a specimen can no longer be used
to identify them because they are being moved around the world. Although you can loosely identify them by
shell color and shape, the best scientific method to identify them from each
other is by genetics.
The green shells showed up in Tampa,
they were unfamiliar to biologists here and never seen in the US before.
natural range of Perna viridis extends from the Persian Gulf east to the South
The natural range of Perna
perna is Africa and South America.
The red shaded circles represent
populations that we are aware of in the Caribbean region which are located in
Trinidad (1990), Venezuela (1993), and Jamaica (1998).
Tampa is a large port where millions of gallons of ballast water are dumped in
port every year. Much of the shipping traffic (~43%) comes from Gulf of Mexico
and Caribbean regions including the northern coast of South America. Only a
negligible amount (~1.5%) of shipping traffic comes from the home range of
Other mussels in the area besides Perna
viridis (Tampa Bay), include Perna viridis (Trinidad), Perna perna
(Texas). All the mussels from Trinidad
(~30) had a distinct green outer margin.
Virtually all the green mussels collected from Tampa Bay had entirely
green shells. The brown mussel here is
entirely brown and has a much thicker shell.
The green mussel shells have been very thin in comparison.
According to the literature, these are
some of the conditions where green mussels live in their native range. The
temperature is 26-32 C. The LC50 is 10 and
36 C after 2 weeks exposure (50-96).
Salinity is 27-33 ppt but can tolerate 20 ppt for short durations. Marc
Blouin has documented even lower salinity measurements where green mussel
exist in the Alafia River. The temperature and salinity tolerances vary
somewhat in the literature. I do not
know how many eggs are produced.
Perna viridis collected from TECO Gannon Station's intake tunnels
October 13, 1999. Over 150
specimens were collected. Sizes ranged from
6 to 63 mm (.24 to
Our first survey in November 1999 just 3
months after we were made aware of there presence. We weren’t really sure
where to begin looking. So we decided to
look in Old Tampa Bay because we already knew they must be in Hillsborough
Bay, that’s where the power plants were. The first green mussel revealed
itself to us on the bottom of this buoy out in the middle of the bay.
Next we decided to start looking at the
bridges in the bay. This I-275, the Howard
Frankland Bridge over Old Tampa Bay.
Here are a few more gaping open. Also you may notice that the mussel inhabit structures
that are exposed at low tide.
This is a good example where you can
clearly see them intertidally. These mussel
are attached the the concrete bridge pilings.
Gail Case of Mote Marine Lab inspects channel marker maintained by Coast Guard Cutter
Joshua Appleby crew in
St. Petersburg, Florida.
We also examined the structures that help
mark the center of the bridge where large boats can pass under it. They are made up concrete with wooden
This mussel we attached to the underside
of the wooden fenders at the underpass.
As you can see they are pretty well covered with barnacles and exposed
out of the water.
This is Mote Marine Laboratory's west
intake pump from the New Pass dock, Sarasota Bay August 3, 2000. Bay water
goes through this pump and is distributed to the lab. One Perna viridis was
It was 7.6 mm (0.30 inch).
The east pump had nine P. viridis ranging
from 1.2 to 4.0 mm (0.05 to .16 inches).
The east pump was last cleaned April 19, 2000. Here you can see the fouling
of Mote Marine Laboratory's west intake system discharge expansion collar from
the New Pass dock, Sarasota Bay. On August 3, 2000 two Perna viridis collected
ranged from 26.9 to 38 mm (1.06 to 1.50 inches).
This is the 1000 ft. pier (shore to 1/4
of the length) at Ft. Desoto Park, St.Petersburg. July 29, 2000, specimens were found on the
on the 3rd and 4th support piling from shore, on the "low" profile
jetty directly to the north of the pier, and on the "high" profile
concrete rubble farther north of the pier.
The furthest south I have personally seen them was on the fishing pier
These are Lido Beach jetties on the Gulf
on Mexico, Sarasota, Florida, on September 21, 2000.
Two Perna viridis collected from the
southern jetty ranged from 27.3 to 42.9 mm (.39 to 1.67 inches).
These specimens were found in the outer edge
of the jetty which receives high wave energy and sandblasting.
They showed irregular growth and
On October 5, 2000 one P.
viridis was found on the south jetty. It was 39 mm (1.53 inches).
Lido Beach, north jetty rocks on the Gulf on Mexico, Sarasota, Florida, September
Five Perna viridis collected
here ranged from 12.5 to 18.0 mm (0.49 to 0.70 inches).
They were collected in high energy
intertidal zone which experiences sandblasting.
All were collected in "protected
crevices or tidal pools on the rocks - all in areas receiving the most wave
Here is a close up of the
"high" profile concrete rubble and its position to the shore line
north of the 1000 ft. pier at Ft. Desoto, St. Petersburg July 29, 2000.
This area receives high energy waves and
experiences "sandblasting" .
This is where very irregularly shaped and colored Perna viridis
specimens were found in the intertidal zone (some fairly high up in the
This is a close up of Perna viridis
growing on the "high" profile concrete rubble (north of the1000 ft.
pier at Ft. Desoto, St. Petersburg, July 29, 2000) in the upper intertidal
area growing among oysters, barnacles and algae. This is an area of high wave energy,
"long" periods of exposure to air, and constant sandblasting.
They were attached very firmly by their
byssus and were difficult to remove by hand.
This is what they look like just having been removed. Some were nearly completely covered with
barnacles. I have some literature that
mentions this fouling in their native range.
Here are two mussels showing the mass of
byssal threads that are used to to attach themselves to a substrate.
This appears to be a ripe female as their
ovaries become this bright orange color.
Males gonad appear white when ripe.
But it becomes difficult to distinguish the sexes when not near
The highest growth rate recorded in an
aquaculture situation was 10.6 mm per month in Singapore (Cheong and Chen
(1980). Preliminary growth rate in Tampa Bay (Apollo Beach) was estimated to
be 7.2 mm per month (Ingrao). Out in
the Bay, preliminary data shows in to be closer to 5.8 mm per month (Benson et
al.). The literature makes mention of a
case where a mussel reached 300 mm. This mussel from Tampa Bay was 109.8 mm
and was estimated to be about 15 months old suggesting that it may have
settled about September 1998.
To sum up where we have found green
mussels, all the symbols represent a location where green mussels were
collected. The difference between
symbols is simply who collected them, which includes USGS, FMRI, Mote Marine
Lab, TECO, and the US Coast Guard. We have found them as far north as Johns
Pass in St. Petersburg and as far south as Boca Grande outside Charlotte
Harbor. We don’t know the complete
range as mussels were collected as the outermost sites we sampled. Blue dots
are Mote Marine collections.
This is Debi collecting Perna viridis from the intake pipes at TECO's Gannon Plant,
October 13, 1999. Over 150 specimens were collected.
Sizes ranged from 6 to 63 mm (.24 to 2.48 inches).
This is one of the mussel
found inside the power plant last August 1999.
Small mussel ~20 mm such as these were gravid at the time they were
This mussel was probably
about 2 months old.
This is the US Coast Guard Cutter Joshua Appleby, St. Petersburg. Whose crew collected
Perna viridis from channel
marker buoys in Port of Tampa, Tampa Bay Florida, December 14, 1999. Twenty one (21) specimens were collected; sizes ranged
from 19 to 109 mm (.74 to 4.29 inches).
Mote Marine Laboratory's west intake pipe
from the New Pass dock, Sarasota Bay August 3, 2000. No specimens clearly
visible on the outside of the intake pipe.
The inside of the intake end of this pipe was scraped approximately 6 inches
in. One 1.7 mm (0.07 inch) Perna viridis was found. It was beige with golden concentric zig-zag
Green mussels may have remedial
properties for helping some common ailments as rheumatoid arthritis and
Green mussel are edible and are consumed
in great numbers in Southeast Asia and South Pacific Islands. Will this help keep their numbers in
check? Maybe where harvesting is
legal. But Tampa Bay will always be a
source for recruitment of young since harvesting is illegal there.
I found several seafood market with
websites advertising green mussels for sale.
I know you can’t read this, but the next to last item on this list has
green mussels selling for $2.95 per pound.
It does give the species name of course, so you can’t be sure exactly
what you’re buying.
This is green mussel culture in Thailand
where they grow on bamboo poles stuck in the bottom. Cotton rope supposedly makes the best
substrate when hung from floating rafts.
Perna viridis have been sold in the
aquaculture industry since at least 1972.
They have been shipped to other islands in the South Pacific to start
an aquaculture industry there.
To summarize : They were first discovered
in a Tampa area power plant July 1999.
They are intensively cultured in Thailand and the Philippines.
They are probably a ballast water introduction.
They are reproducing and spreading out of the bay.
Of course everyone wants to know how far
could they spread and survive. The dark
red represents areas of coastlines where I believe green mussel can overwinter. The pink areas are less suitable based
solely on their temperature tolerance.
They have already survived temperatures as low as 12oC
in Tampa Bay last winter.
Unfortunately, they are too well
established to eradicate on Florida’s west coast. The only way we can attempt to control them
is by not spreading them intentionally or unintentionally.
There is much
interest already by commercial fisherman to harvest green mussels where it’s
legal for human consumption.
This is another species to be on the
lookout for along the Atlantic coast. Currently,
it is found in the Chesapeake Bay area since 1998. It feeds on other mollusks
such as oysters.