ICYMI, a June 2023 day at the beach in Brazoria County south of Houston, Texas would have been less than pleasant. Sarah Kuta via Smithsonian Magazine:
Conditions created a “perfect storm” that robbed the water of dissolved oxygen near the coast
Tens of thousands of dead fish washed up on the beaches of Texas’ Gulf Coast over the weekend—and wildlife officials say low levels of oxygen in the water are likely to blame.
The carcasses began covering sand in Brazoria County south of Houston on Friday, prompting beach closures and creating a stinky mess for clean-up crews. County officials initially urged people to steer clear of the beaches because of high bacteria levels and sharp fins. On Tuesday, after employees cleared away or buried the dead fish, they gave the all-clear for beachgoers to return.
One of the consequences of a warming planet is the atmosphere can hold more water vapor as temperatures rise. This can lead to ever bigger downpours and flash flooding events. The reverse is not true for warming oceans; as water warms it holds less and less dissolved oxygen — and fish begin to suffocate and die for lack of oxygen.
I still remember a high school chemistry demonstration. The teacher put a beaker of soda over a bunsen burner flame. It began bubbling furiously — and then he stuck he finger in it without getting burned. The soda wasn’t boiling. The dissolved gases in it from carbonation were being driven out as the soda heated. The ocean may not be boiling — yet — but the same thing is going on as the waters warm.
This is a ‘normal’ event. This kind of thing happens all the time wherever water begins to warm to a point where the fish living in it can’t get enough oxygen out of it to live. The problem is, this is only going to become more ‘normal’ as the planet continues to warm.
What happened in Texas was a combination of things. The waters near shore had been warming up for weeks. The weather had been relatively calm, so that there was little wave action which would have helped mix oxygen into the water. Cloudy conditions had held down the photosynthesis by phytoplankton in the water, which cut their release of oxygen. All of this combined to bring local menhaden fish to the point of mass death. The statement from the Brazoria County Parks treated it as no big deal:
However, oxygen levels should return to normal in the near future, because “Mother Nature has a way of balancing that out,” says Bryan Frazier, Brazoria County Parks Department director, to the New York Times’ Chris Cameron.
emphasis added
This is a ‘good thing’ from a certain point of view.
Though the massive die-off has caused some temporary unpleasantness for beachgoers, it also likely contributed a “huge nutrient pulse into our environment,” as Katie St. Clair, sea life facility manager at Texas A&M University at Galveston, tells NPR’s Juliana Kim. Many of the fish washed up on shore as “shredded skeletons,” per a Facebook post from Quintana Beach County Park, meaning their flesh got eaten or was left to decompose in the water.
emphasis added
Pure speculation on my part, but I suppose a mass die-off of humans from extended heat above survivable levels would also release a huge nutrient pulse. Certainly vultures would benefit — assuming they survived the heat.
While this kind of event is not unprecedented, what will have to be taken into consideration is how this is going to happen more frequently as global temperatures continue to rise. Besides fish kills, there can be other major consequences. See what’s happening in Florida.
“This will likely be the worst mass-extinction and bleaching of coral in the Florida Keys in our time.”
It’s not just the oceans where this heat stress is having consequences; fresh water species are not immune to decreasing oxygen levels as temperatures rise. FROM 2021
Winter-run Chinook salmon are born in the Sacramento River, traverse hundreds of miles to the Pacific, where they normally spend three years before returning to their birthplace to mate and lay their eggs between April and August. Unlike the fall-run Chinook that survives almost entirely due to hatchery breeding programs, the winter run is still largely reared in the wild.
Federal fisheries officials predicted in May that more than 80% of baby salmon could die because of warmer water in the Sacramento River. Now, state wildlife officials say that number could be higher amid a rapidly depleting pool of cool water in Lake Shasta. California’s largest reservoir is filled to only about 35% capacity, federal water managers said this week.
“The pain we’re going to feel is a few years from now, when there will be no naturally spawned salmon out in the ocean,” said John McManus, executive director of the Golden State Salmon Association, which represents the fishing industry.
It’s not just the heat; it’s also degradation of the natural habitat that puts increasing stress on wildlife. In New York State, people are being warned against building dams and rock pools to try to improve swimming in waterways where trout are trying to survive.
Don’t move rocks in streams
Now that summer’s officially here it’s important to understand the detrimental impact building rock dams with the intent of creating swimming holes can have on trout streams.
Trout are sensitive, cold-water fish that require cold, clean water to survive. Water temperatures warmer than 68°F can put extreme stress on trout and temperatures approaching 75°F can even be lethal.
Rock dams…
- Alter the natural flow of the stream by slowing down or trapping the water, allowing it to warm up faster.
- Prevent the migration of trout to colder headwaters where they can seek thermal refuge in the warm summer months, as well as spawning habitat in the spring and fall.
- Prevent upstream and downstream movement of animals, such as aquatic insects- a major diet item for trout.
- Weaken the stream bank, increasing erosion and sedimentation into the stream, further altering its natural flow.
So, this summer if your favorite swimming hole is drying up, think about the trout that live there. Instead of building a rock dam, maybe go for a walk downstream and find a natural pool to cool off in.
More information here for anglers going after trout and salmon.
We have to remember that dealing with climate change isn’t just our problem (and our responsibility). It’s vital for every life form with which we share the planet.
See “What is so rare as a day in June” for some perspective on the natural world.