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I'm just wondering how the predicted dead zone and past dead zones have impacted little lagoon. It does have a continuous supply of oxygenated (fresh/brackish?) water, so hopefully the dead zone wouldn't affect it- or at least not as much? I really have no idea since I've seen the water flow both ways in the pass. Just hopeful that the lagoon provides a sort of sanctuary for the fish that can handle decreased salinity.
I'm no expert, but my understanding is that the heart of the dead zone is in deeper nearshore water ( few miles offshore mostly) and a result of a lack of mixing (mostly vertical mixing).
The oxygen problems that have plagued the Little Lagoon are a result of lower inflow and the inlet being restricted so that there is not enough interchange with the oxygenated surf zone. When I was a small child (late 1940s and early '50s) there were multiple inlets, but now only one. There is a court order mandating that the inlet be dredged regularly to maintain that interchange.
Little Lagoon, while it has oxygen problems, would only be affected by the dead zone problem if the major dead zone comes our way and extends to the nearshore environment. Pray for strong east-west currents.
Little Lagoon seems to stay 'healthy; as long as the mouth remains open to the gulf.
This hypoxic zone that folkses get so worked up about every year has been a natural phenomenon since the Mississippi River (and Mobile River, etc.) was created. The conditions however, have been exasperated due to excessive nutrients via human activities.
But it tends to only affect benthic zones farther out in the gulf (or bay) on a temporary basis.
Not 'high energy' locals like passes and the surfzone.
Smaller, temporary so-called 'dead zones' may pop up occasionally all along the coast farther offshore though as decay of dead algae and other detritus from inland runoff occurs simultaneously with peak water temperatures.
how long does the average "dead zone" last?
Not sure of your sources but from 1988-2012 Little Lgoon didn't have any meaningful dissolved oxygen issues...
it did have issues related to stormwater runoff, waterfront lot owners fertilizing their yards, and old septic tank issues.
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Originally Posted by frednic
Perhaps poorly stated, but what I meant was that the lagoon would have low oxygen at times if the dredging were not maintained. Fertilizers and septic tanks lead to blooms which lead to die-offs which lead to low oxygen.Quote:
Originally Posted by JayHook
The amount of water being exchanged now compared to 20-30 years ago is so low that there has not been a meaningful brown shrimp crop there in at least 15 years. The number of larvae entering is directly related to the amount of gulf water coming into the lagoon through the pass. It applies to other species as well and a lack of food for trout and reds has led to a severe decline in their numbers in the lagoon as well as their condition (many are very skinny). Some that haven't fished there but the last 10 years and who think it is great fishing have no idea how good it used to be in the pre Ivan years.