Mid to late May, 2000: Large amounts of Sargassum weed and 'blue-water' were reported about 20 km from shore.
1st week of June: First specimen of Phyllorhiza collected several km south of Mobile Bay. This specimen was placed on display in our public aquarium (and as of July 5 is still doing well). To see a picture of the exhibit animal click here.
Mid-June: Heavy fouling of beaches of northwest Florida, Alabama and Mississippi with Sargassum.
Last week of June: Reports begin filtering in that abundant, large 'spotted' jellies (Phyllorhiza) are being recovered in shrimp trawls inside of Mobile Bay.
July 3: On our first sampling trip, we find large numbers of Phyllorhiza within the southern Mobile Bay and along the Gulf of Mexico shore of Dauphin Island. Animals range in size from about 5 cm to the largest recovered at 43 cm (picture). Median size was about 35 cm. There were medusae that would not fit into our dipnet, therefore we believe animals were as large as 50 cm across (or larger). Picture of large animal below the surface.
Medusae were most dense along the Gulf shoreline of Dauphin Island. We estimated medusae swimming to the surface every 10-15 meters or so.
All animals appeared to be void of zooxanthellae (verified microscopically later in the lab). As many as 200 small (1-3 cm) butterfish were collected with a single jelly. Picture of Phyllorhiza held in our kreisels at DISL.
A single animal was dissected. This male was actively shedding sperm off the tips of the oral mass when it was in its bucket. A picture of this particular animal.
July 7: A trip documenting that bleaching of individuals was widespread. An example image with color reference is shown here. Note that the brown color in the center is the animal's gonadal tissue and not zooxanthellae.
August 1: An areal survey was conducted to assess the extent of Phyllorhiza in the northern Gulf. We have suspected that the main core of medusae are moving westward with the prevailing nearshore current. Very few medusae were spotted around, and to the east of, Mobile Bay. Medusae were more concentrated in the passes between barrier islands between Mobile Bay and Cat Island along the western Mississippi Sound. Medusae were rare to absent beyond the southern tip of the Chandaleur Islands (off Louisiana). By far the greatest concentration of medusae were to the northwestern corner of the Mississippi Bight; more medusae were found within the Mississippi Sound than in the adjacent Gulf, but only along the north side of the islands (i.e., they don't span across the Sound).
Two extreme aggregations were observed during the survey. One series of aggregations (highest concentrations observed) was at the mouth of Lake Borgne (LA). I say series because they occurred as 'waves' of aggregations about 100 m across and perhaps a kilometer or so long - not sure why. The other aggregation was on the north side of Horn Island in the Mississippi Sound. This aggregation was not quite as concentrated, but perhaps more contiguous (not banded) than the Lake Borgne aggregation.
Here is an image of one of the Lake Borgne aggregations. It shows a slice through a band of jellies about 100 m wide (going up and down in the image). It isn't the clearest image (small plane + lots of excitement), but the 'specks' are ALL Phyllorhiza. I estimate that a 100 m2 area contains easily 50 medusae - and these are only the ones near the surface that we can see.
