Ultimately, eggs are the key to the survival of fairy shrimp species, families, and the Anostraca order itself. Populations survive as long as some eggs remain viable. What would it take to kill off fairy shrimp eggs and put an end to the Anostraca order?
- Not an asteroid impact, at least as long as it left most of Earth intact. Fairy shrimp fossils have been found in rocks that are somewhere between 393 and 419 million years old (see Taxonomy and Origin of Anostraca). That oldest family of fairy shrimp is extinct but fairy shrimp are still here so some family or families survived the dramatic end-Cretaceous extinction due to an asteroid impact about 66 million years ago. That’s the one which ended the dinosaur fossil record. Of course no adult fairy shrimp survived; they generally don’t live longer than several months anyway. New generations arose from the eggs.
- Not a period of intense volcanism with voluminous ash and gases causing nuclear-winter-like conditions. That happened during the end-Permian extinction about 252 million years ago. Fairy shrimp inhabited Earth before and after the event.
- Not a period of warming that eliminates the polar ice caps. These were absent 145-34 million years ago (Cretaceous through Eocene) and at other times (e.g., O’Brien and others, 2020). Fairy shrimp are still here.
- Not cosmic ray bursts from a local supernova. There have been 2 such events in the last 10 million years (Thomas and others, 2016) and fairy shrimp are still here.
- Not a temporary increase in ultra-violet radiation due to a large solar storm. These occur every few years and fairy shrimp are still here.
- Not cyclical glacial coolings and interglacial warmings. These have occurred repeatedly over the last 1.6 million years, as documented by the Illinois State Geological Survey (see “Quaternary Glaciations in Illinois” at isgs.illinois.edu) and earlier in Earth history. Fairy shrimp are still here.
- Not a period of glaciation where ice extends down to the mid-latitudes. The Wisconsin glaciation 75-15 thousand years ago did that (see “Quaternary Glaciations in Illinois” by the Illinois State Geological Survey at isgs.illinois.edu). Fairy shrimp are still here.
- Not earthquakes, hurricanes, floods, droughts, forest fires, or sea level changes. These happen in various parts of Earth all the time. Floods could wipe out a fairy shrimp population by washing all the eggs downstream but the other events are unlikely to affect fairy shrimp eggs much. Even if they do, they are unlikely to be extensive enough to affect a large proportion of fairy shrimp ponds. Fairy Shrimp in the Long Term – top
- Probably not a nuclear holocaust.
- The immediate impacts of direct radiation, heat flash/fireball, blast wave, and subsequent fires are unlikely to affect all fairy shrimp-hosting ponds globally as fairy shrimp are distributed from Antarctica and the Arctic to South America, southern Africa, and Australia in addition to the regions likely to be most affected (for a synopsis of the effects of a nuclear exchange see Wolfson and Dalniki-Veress).
- The longer duration “fallout” of radioactive isotopes would be deadliest within kilometers/miles of detonation sites and would produce increased risk of cancer and later cancer death in metabolizing individuals farther away but would have less of an effect on cryptobiotic resting eggs. Radiation effects decrease exponentially over time but persist at low levels for decades. Effects also decrease as the isotopes diffuse into water/ice droplets and fall out of the atmosphere as rain/snow but then the receiving soil or water becomes more radioactive. That could be a problem for some ponds.
- Over periods of months and years, ozone would be depleted by nitrogen oxides and soot lofted into the stratosphere and the resulting increase in ultraviolet radiation at the surface would increase disease and cellular dysfunction (Birks and Stephens, 1986). The shells of resting eggs block some ultraviolet radiation. Pond bottom dirt could block some more. Ultraviolet radiation effects would greatest at higher elevations and at the poles but lower and lower latitude ponds might be okay for resting eggs.
- Toxic chemicals would be spread into the atmosphere and distributed globally by blasting or burning of petroleum products, building materials, road materials, asbestos, plastics, and chemical and other industrial facilities. Toxicity would be greatest closest to, and downwind of, urban centers and major industrial complexes. Like radioactive isotopes, toxic chemicals would eventually accumulate in soils and water as they are rinsed from the atmosphere. Some humans would certainly die from the inhalation of highly toxic compounds like hydrogen cyanide and sulfur dioxide from the air but that wouldn’t affect eggs. Cancers caused by a wide variety of chemical toxins in soil and water could affect eggs over a longer term (Birks and Stephens, 1986). Even if all ponds within 30 km (19 miles) of urban centers and major industrial complexes become uninhabitable, that leaves plenty of others for fairy shrimp.
- Climate modeling indicates that the soot produced by firing about one third of the nuclear weapons available in 2006 would cool average global surface temperatures by 3-4 C (5.4-7.2 F) for 4 years and reduce average global precipitation by 20-27%. Local changes would be more dramatic. For example, July temperatures (after a May nuclear exchange) would be about 13 C (23 F) cooler in Iowa the first year and 10 C (18 F) cooler the second year. After 10 years, average global surface temperature would still be 1 C (1.8 F) cooler (Robock and others, 2007). Although it could be several years before ponds warm up to temperatures suitable for the hatching of established fairy shrimp populations and receive sufficient precipitation, fairy shrimp eggs can wait that long.
- Global cooling in a nuclear winter is caused by the unusually dense concentration of soot and dust in the atmosphere reducing the incoming sunlight to 61% of what is normal in the first year and still 83% of normal at the end of the 4th year. Wolfson and Dalniki-Veress (2007) estimated the change in global surface shortwave radiation as -58 Watts/square meter maximum and as -25 Watts/square meter at the end of 4th year [my interpolation on tiny graph] compared to a global mean “net downward (or absorbed) surface SW radiation” for the period 1984-2000 of 149 Watts/square meter (Hatzianastassiou and others, 2005). Soot and dust would eventually be removed from the atmosphere in precipitation, which would be lower than normal for at least a decade due to the decrease in evapotranspiration as a result of cooling by soot and dust. Darker days for several years would greatly reduce photosynthetic activities. The ability of phytoplankton to come back after a nuclear exchange may be just as consequential for fairy shrimp as egg survival. Phytoplankton have graced Earth for more than 2 billion years so they are unlikely to die off.
- The combination of increased ultraviolet radiation, radioactive fallout, toxic chemical fallout, and decreased temperature and sunshine could well affect different species differently and change the balances of predator-prey relations and food competition in ponds. I know too little about other pond species to make a guess about whether predation on, and competition with, fairy shrimp would be better or worse post-nuke.
N.B. Robock and others (2007) presented even more devastating model results for firing all the nuclear weapons known in 2006 (i.e., 150 Teragrams of soot) but I consider that less realistic than the 1/3 case (i.e., 50 Teragrams of soot) because it fails to account for weapons not mounted on launch vehicles when the opponent launches or for those destroyed or disabled in the first exchange. Furthermore, the Stockholm International Peace Research Institute estimated nuclear stockpiles in 2021 were about 63% of those estimated by Robock and others (2007). A large majority of humans will die within the first year in either case. More resilient species would be more sensitive to the length of the nuclear winter.
Fairy Shrimp in the Long Term – top
Does this mean Anostraca is the greatest Crustacean order ever? Not necessarily. Of the 50 Crustacean orders (following Moore, 1969, but splitting Conchostraca into 3 orders after Olesen, 2007, and Cladocera into 4 orders after Olesen, 2007, and Thorp and Covich, 2001), Moore (1969) indicated 14 are extinct. They are retired now regardless of their accomplishments during their times of existence. Although some of the 36 extant orders may be relatively new arrivals, several crustacean orders have been around since before the end-Cretaceous extinction, including the other branchiopod orders Notostraca and Conchostraca (or Spinicaudata, Laevicaudata, Cyclesthriidae) and some may be even more widespread and numerous than Anostraca. Some orders of barnacles (class Cirripedia, order Thoracica) and ostracods (class Ostracoda, orders Myodocopa and Podocopa) have been on Earth longer than Anostraca and are definitely contenders. A detailed comparison of orders is way beyond the scope of this web site but, if nothing else, I can opine that Anostraca is one of the most graceful of crustacean orders.
Humans have driven some species to extinction but, as far as I know, not an order with dozens of species. Ongoing fish-stocking zooicide (see Wind River Mountains, East Central Sierra Nevada) has likely eliminated thousands of fairy shrimp populations and, of course, we will never know if that included some entire species. That, as well as urbanization, suburbanization, agriculture, pavement, and other human effects haven’t come close to wiping out the order. Now that humans are raising Artemia fairy shrimp to feed fish and shellfish, the order doesn’t seem to be in any danger from humans in the near future beyond routine wanton slaughter.
So fairy shrimp might be here until the sun hits the red giant phase and boils off Earth’s water. That’s pretty good for such a small and superficially defenseless animal.