Everglades 3

Gar: living fossil tolerant of low oxygen
Swim bladder
Exchange across tissue layers like placenta
Fish can inflate or deflate bladder and stay in place
Gar has tube that creates link between gut and swim bladder
By coming up for air
Vascularized tissues associated with this
Can use like a lung
Fish that can't do this were weeded out
Don't see zero oxygen in Everglades but not much
Cattails an anthropogenic effect
Nutrient enriched water into national park
Cattail monocultures
Big federal lawsuit
Under supervision
Ag interests want court to rule quickly
But clean water act says you can't dump water into Everglades
As we go north the cattails disappear
Becomes sawgrass: historical vegetation for the ridges
Serrated blades
You have to wear protection
Nutrient enrichment drops off quickly in this canal because of flow from north to south
Boat disturbance releases nutrients
This ecosystem is supersensitive to phosphorus
Very low phosphorus in water historically cf wetlands in Jamaica
So when people add it it has cascading effects
Changes in algal community
Changes in cattails
You need a number to enforce the rules
Phosphorus is accumulating
2-8 ppb historically
Near or below detection limit
Hard when you're enforcing a standard
We argued that over 10ppb is problematic
Closer to 10, easier to reach nutrient rich ecosystem
Nutrient spiraling
Ecosystem flips
"loading" or accumulating over time
Slowly saturated system
No practical way to take phosphorus out
Which is worse? Overstrung or adding more phosphorus? This is a common argument
Trexler thinks it's better to leave dry then slowly add water back
But peat oxidizes and compacts, takes hundreds of years to take back
Dilemma