Why so few inverts at Destin jetties?

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Dave C

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Superbugman and other Panhandle divers,

I just read your dive report about the Destin and Panama City jetties. I am curious as to your opinions on why there is so much more invertebrate life at the Panama City jetties. I am an avid snorkeler, and own a vacation condo in Destin, so I've spent a lot time in the water at the jetties there. Obviously, there is very little living on the rocks in Destin except a fuzz of algae, and I have often wondered why. There's a few anemones, maybe I've seen one or two urchins (can't recall specifically), never a sea cucumber, no octopus (I know some photos have been posted so they must exist there), and I once saw someone find a fairly large starfish. In contrast, the Crystal Pier pilings in the Gulf near Destin (an extremely small habitat) seem to be covered with invert life: sponges, live murex snails, shrimp, urchins and numerous anemones living inside hollowed out parts of the pilings, and even octopus sometimes seem to be common (once I saw four or five different octopus on the pilings). I have never been to the St. Andrews jetties, but it sounds from your description as though the inverts there may be similar to what are on the Crystal Pier pilings.

I surmise that perhaps there is occasional heavy input of freshwater to Choctawhatchee Bay that ends up flowing out the pass. If so, this could prevent many of the inverts such as sponges or urchins from ever becoming established. Most species of marine fish are much more tolerant of lower salinity than are invertebrates. I think there is relatively little freshwater input into St. Andrews Bay (the rivers going in there are pretty small, aren’t they?), so maybe invertebrates are better able to survive there. What do you think of this explanation?

By the way, how is the snorkeling at the St. Andrews jetty compared to the Destin jetty? I’ve heard the water isn’t usually as clear at St. Andrews, but your report about all the growth on the rocks makes it sound interesting..
 
St. Andrews definately has more invertabrate life, so does Fort Pickens, although not to the same extent. The jetties in Alabama Point are fairly bare(aside from algae, the occasionaly anenome, urchin, and smaller sponges) much like the Destin Jetties. I've seen octopus in Destin and in Alabama Point, they are just much more active at night and the likelyhood of spotting one is greater. SeaYoda and I spotted a fireworm two weekends ago in Destin as well - so they are out there...

You may be correct with your reasoning for the reduced amount of invertabrate life, although I don't have any hard facts to back it, or work against it. Seems logical to me though..
 
The flow may have something to do with what ends up living on the rocks in a given season. I've seen a change in life on the rocks since the dredging and storms moved stuff around. I have seen a couple urchins, a few small sponges, a few small gorgonians. I have never seen these at all at the jetties. The earlier infestation of arrow crabs was unusual too.
 
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