by Erin Thursby
Some of the most important ecology goes on in those hidden areas and transition between one environment and another. Because such areas aren’t clearly delineated and change from season to season as conditions change, it’s hard to know what kind of impact these places have. We do know for certain that these in-between environments often serve as a place to raise young and very often support species that can adjust between the two environments or are specific to the transitional environment.
Nowhere is this truer than in the brackish estuary waters at the mouth of the St. Johns. Courtney T. Hackney, Director of Coastal Biology and Biology Department Chair, is particularly interested in this little studied in-between environment.
“For a lot of years scientists either spent their time in the swamps with the cypress trees or down in the salt marsh, because they’re a little more glorious than the places that are in between, going back and forth,” says Hackney.
The study of these transitional waters is even more important, now that water usage and sea level rise has quickened the changes between salt and freshwater.
“With the sea level rise, what has happening is that there is a change from cypress swamps into salt marsh. The process by which that happens is very poorly known…If sea level rises and more of these swamps get flooded, there’s a potential that more of these swamps can actually function like salt marshes did.”
The changes are happening so quickly that it’s difficult to tell how the flora and fauna will react and if they will be able to adjust and bounce back.
Salt in the St. Johns where salt has never been can have a detrimental effect on native wildlife. Vegetation not equipped to deal with salinity dies, as does the animals that feed on that vegetation. Freshwater fish move further upstream or die and are replaced by marine creatures.
Other contributing factors are drought, the removal of water from the St. Johns and our own water usage here in Jacksonville.
Fishermen who are finding saltwater or brackish types of fish in places they’ve never caught them shouldn’t necessarily attribute the change to a rapid sea level rise, but as a result of what we have done locally. Fish kills, sometimes attributed to pollution, are sometimes the result of a rapid change in salinity.
“When we widen and deepen rivers, like we’re doing her in the harbor and channels in Jacksonville, what happens is that it allows more salt water upstream. So when we manipulate the river at the mouth, we cause a lot of changes upstream that aren’t apparent…That’s been happening all over the world…It sort of makes the sea level rise seem to be happening much faster than it actually is.”
If we keep our aquifer at a higher level, the St. Johns will stay balanced as far as salinity is concerned. But if we wantonly water our lawns, deepen the river and sell our water, we might find that the ocean will eat our river, bite by bite and fishing hole by fishing hole.
Salt in the St. Johns
by Erin Thursby