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Climate Change Effects on Cephalopod Population and Distribution
Advantageous Characteristics

In higher temperatures it is seen that cephalopods produce more small sized offspring rather than few large offspring which improves survival rate and decreases the life span of the generation. This decreased life span positively impacts the phenotypic plasticity of the species, allowing for adaptations for temperature, dissolved gas and salinity to quickly occur between generations. Decreased size of cephalopod eggs allows for decreased oxygen requirements in maturation and as an adult, allowing more species to inhabit anoxic and H2S containing waters.

Increased Population

Large number of offspring, a low infant mortality rate, and a rapid reproduction rate allow cephalopods to rapidly adapt to changing environmental factors. By examining the catches of commercial fisheries and research surveys over the past six decades, scientists have found a significant increase in cephalopod populations. The reproduction rate of Japanese Flying Squid is related directly to surface water temperature between 15-23C. As the range of suitable habitat expands, the recruitment rate and size of adult population increases.

Expanded Range

With a warming ocean, the range of cephalopods has expanded to areas where before some species would be accidental migrants Loliginids and ommastrephids like Lesser Flying Squid and Shorfin Squid have been recorded as permanent residents of the North Sea in the last few decades, where before these species would migrate to the North Sea for foraging and spawning Many species of cephalopods seem to handle anoxic conditions better than other species. Purpleback Flying Squid inhabit the oxygen minimum zone of the Arabian Sea. They spend the day in this zone, avoiding large predators, and migrate vertically at night in order to feed. Cephalopod’s ability to handle anoxic conditions, in an ocean where dead zones are expanding, may allow them to survive future ocean conditions. Humboldt squid seem to have an affinity for these regions with 10% of standard surface oxygen levels, as they seem to use them as natural highways to reach new habitats. Humboldt squid effectively have become the apex predator of dead zones, as the oxygen levels are too low to support their predators like billfish and sharks. Other creatures that inhabit dead zones, like krill and lantern fish, use the anoxic conditions to avoid their own predators, but now humboldt squid find themselves in a niche high on the food chain without any competitors, fueling their population growth.

Dissolution of Nautiloid Shells

Like many shelled creatures today, shelled cephalopods such as Nautiloids are under threat of dissolution as the ocean temperatures rise and pH falls. A study was conducted on a number of Argonauta nodosa, or Paper Nautilus to determine the effects that near future ocean conditions can have on their shells. These nautiloids have a very thin shell used as a brood chamber of underdeveloped embryos, while other species primarily use theirs for defense. The study found that increased temperatures and decreased pH levels caused dramatic dissolution of nautiloid shells and significant weight loss. The study does show the effects of ocean acidification on shelled cephalopods, so while some species may not be as affected as paper nautilus’, the dissolution of shells means that many shelled cephalopods will have to deal with a weaker shell, making them more vulnerable to predators and parasites.

Effect on Metabolism

An increase in CO2 and ocean acidity seems to cause a decrease in the metabolic rate and activity rate of cephalopods. This would cause cephalopods to not eat as much which would have negative impacts both on their development and their ecosystem. As keystone predators, a decrease in activity rate could have a trophic cascade effect on their ecosystem, as the old, weak, and sick are not consumed. An increase in attack time has also been recorded, meaning that rising acidity provides prey animals a larger window of opportunity to escape, decreasing cephalopod success rate.