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Message
re: Louisiana's number one again: Biggest dead zone
Posted on 8/2/17 at 8:49 pm to CptBengal
Posted on 8/2/17 at 8:49 pm to CptBengal
quote:
Examples of Saltwater Organisms and Dissolved Oxygen Requirements
Saltwater fish and organisms have a higher tolerance for low dissolved oxygen concentrations as saltwater has a lower 100% air saturation than freshwater. In general, dissolved oxygen levels are about 20% less in seawater than in freshwater ³.
This does not mean that saltwater fish can live without dissolved oxygen completely. Striped bass, white perch and American shad need DO levels over 5 mg/L to grow and thrive 5. The red hake is also extremely sensitive to dissolved oxygen levels, abandoning its preferred habitat near the seafloor if concentrations fall below 4.2 mg/L ²?.
The dissolved oxygen requirements of open-ocean and deep-ocean fish are a bit harder to track, but there have been some studies in the area. Billfish swim in areas with a minimum of 3.5 mg/L DO, while marlins and sailfish will dive to depths with DO concentrations of 1.5 mg/L ³°. Likewise, white sharks are also limited in dive depths due to dissolved oxygen levels (above 1.5 mg/L), though many other sharks have been found in areas of low DO ³³. Tracked swordfish show a preference for shallow water during the day, basking in oxygenated water (7.7 mg/L) after diving to depths with concentrations around 2.5 mg/L ³4. Albacore tuna live in mid-ocean levels, and require a minimum of 2.5 mg/L ³5, while halibut can maintain a minimum DO tolerance threshold of 1 mg/L ³6.
Many tropical saltwater fish, including clown fish, angel fish and groupers require higher levels of DO, such as those surrounding coral reefs. Coral reefs are found in the euphotic zone (where light penetrates the water – usually not deeper than 70 m). Higher dissolved oxygen concentrations are generally found around coral reefs due to photosynthesis and aeration from eddies and breaking waves ³7. These DO levels can fluctuate from 4-15 mg/L, though they usually remain around 5-8 mg/L, cycling between day photosynthesis production and night plant respiration ³8. In terms of air saturation, this means that dissolved oxygen near coral reefs can easily range from 40-200% ³?.
Crustaceans such as crabs and lobsters are benthic (bottom-dwelling) organisms, but still require minimum levels of dissolved oxygen. Depending on the species, minimum DO requirements can range from 4 mg/L to 1 mg/L ¹³. Despite being bottom dwellers, mussels, oysters and clams also require a minimum of 1-2 mg/L of dissolved oxygen 29, which is why they are found in shallower, coastal waters that receive oxygen from the atmosphere and photosynthetic sources.
LINK
Is a dead zone really a dead zone, or just jibber jabber?
1
Posted on 8/2/17 at 8:56 pm to deeprig9
The idea that nitrogen from fertilizer runoff is creating low dissolved oxygen is inconsistent in my opinion.
In small controls, like a farm pond, the local nitro fertilizer runoff creates algae and other plant life to take off in the pond, explode. Dissolved O2 actually skyrockets.
The problem occurs when days start getting shorter and temps start dropping, all of the algae and plant life start to die off, and the decomposition process then sucks all of the O2 out of the water and displaces it with CO2. This creates fish kills.
This LA Dead Zone doesn't fit into this model.
Temps are still high, days are still long, why would O2 be getting sucked out of the water just because of fertilizer runoff? Fertilizer runoff on its own does not cause this.
Someone smarter than me please explain.
In small controls, like a farm pond, the local nitro fertilizer runoff creates algae and other plant life to take off in the pond, explode. Dissolved O2 actually skyrockets.
The problem occurs when days start getting shorter and temps start dropping, all of the algae and plant life start to die off, and the decomposition process then sucks all of the O2 out of the water and displaces it with CO2. This creates fish kills.
This LA Dead Zone doesn't fit into this model.
Temps are still high, days are still long, why would O2 be getting sucked out of the water just because of fertilizer runoff? Fertilizer runoff on its own does not cause this.
Someone smarter than me please explain.
This post was edited on 8/2/17 at 8:58 pm
Posted on 8/2/17 at 8:58 pm to crewdepoo
I thought this was a New Orleans thread
Posted on 8/2/17 at 9:01 pm to jimbeam
quote:
We could stop growing food with fertilizer if y'all would prefer that
MUSHROOMS TO THE RESCUE
Posted on 8/2/17 at 9:06 pm to crewdepoo
That's a Gulf Coast thing, and you can blame all the farms connected to every river in the Mississippi River valley...
Posted on 8/2/17 at 9:07 pm to deeprig9
quote:
This LA Dead Zone doesn't fit into this model.
Temps are still high, days are still long, why would O2 be getting sucked out of the water just because of fertilizer runoff? Fertilizer runoff on its own does not cause this.
Someone smarter than me please explain.
I just thought of something....
Hot water holds less O2. Basic physics.
Lots of algae and plant life make dissolved o2 go up. Conversely, a lack of algae and plant life makes o2 go down.
Algae and plant life need sun to thrive.
There's alot of suspended sediment coming out of the mighty Miss. Suspended particles block light.
Hypothesis:
Higher levels of suspended sediment inhibit algae growth resulting in lower o2 levels, compounded by high temperatures, create the so-called "Dead Zone". This "Dead Zone" exists every year, some years it is smaller, some years it is bigger. It has probably always been there. Alarmist media and short-sighted scientists ring the bell, we all get concerned.
This post was edited on 8/2/17 at 9:09 pm
Posted on 8/2/17 at 9:12 pm to crewdepoo
Just my 2 cents.
I have a feeling that this dead zone has been going on since the the Mississippi River was formed. And there is not much that we can do to prevent it. You have nutrient rich fresh water meeting the ocean. Fresh water during high river stages floats on the top and the algae population explodes then sinks to the bottom when the river flow gets low and the algae dies. This results in a low oxygen environment killing anything on the bottom that doesn't move out.
All this "research" is just another scientist's wet dream of finding another easy way to feed off the government's trough of science research funding. It is the same thing with Climate Change.
I have a feeling that this dead zone has been going on since the the Mississippi River was formed. And there is not much that we can do to prevent it. You have nutrient rich fresh water meeting the ocean. Fresh water during high river stages floats on the top and the algae population explodes then sinks to the bottom when the river flow gets low and the algae dies. This results in a low oxygen environment killing anything on the bottom that doesn't move out.
All this "research" is just another scientist's wet dream of finding another easy way to feed off the government's trough of science research funding. It is the same thing with Climate Change.
Posted on 8/2/17 at 9:12 pm to TigerintheNO
quote:
Are they positive it is from farming and not the 200 million gallons of oil that BP spilled in the Gulf?
1) Deadzone research has gone on since the 80's. The previous record was in 2002. The BP oil spill was in 2010.
2) The gulf has natural seeps that release far more oil each year than the BP oil spill. The oil spill was catastrophic because it released so much oil and gas at once.
Posted on 8/2/17 at 9:57 pm to deeprig9
quote:
The idea that nitrogen from fertilizer runoff is creating low dissolved oxygen is inconsistent in my opinion.
In small controls, like a farm pond, the local nitro fertilizer runoff creates algae and other plant life to take off in the pond, explode. Dissolved O2 actually skyrockets.
The problem occurs when days start getting shorter and temps start dropping, all of the algae and plant life start to die off, and the decomposition process then sucks all of the O2 out of the water and displaces it with CO2. This creates fish kills.
This LA Dead Zone doesn't fit into this model.
Temps are still high, days are still long, why would O2 be getting sucked out of the water just because of fertilizer runoff? Fertilizer runoff on its own does not cause this.
Someone smarter than me please explain.
You should first look up Cushing's Match/Mismatch hypothesis.
Basically it is different than your farm pond example...but you have it pretty close.
Nitrates are primarily limiting as a nutrient for phytoplankton growth in the Gulf of Mexico. River discharge increases the amount of available nitrate, thereby increasing the phytoplankton bloom. Unfortunately the zooplankton community cannot respond as quickly to the bloom, and when the nutrients run out...about August, most of those phytoplankton die and begin to sink.
Because we have limited storm activity in the Gulf this time of year, and because of lessened wind vectors, coupled with the freshwater lense from river discharge there is a strong pycnocline (primarily salinity related) that gets established.
This means that the oxygenated surface waters arent mixing below the density discontinuity and the microbial community feasting on the dying phytoplankton that is sinking results in low oxygen.
Posted on 8/2/17 at 10:00 pm to CptBengal
Good post. Years of hurricanes tend to have less of a dead zone as you mentioned.
Posted on 8/2/17 at 10:43 pm to crewdepoo
Thank ethanol.
All the fertilizer to grow extra corn for that shite is why.
All the fertilizer to grow extra corn for that shite is why.
Posted on 8/2/17 at 11:05 pm to crewdepoo
Must be that huge spinning ball of plastic I keep hearing about.
Posted on 8/3/17 at 12:10 am to StrangeBrew
quote:
Must be that huge spinning ball of plastic I keep hearing about.
You would think if is as big as Texas, you would have some satellite photos.
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