CORVALLIS, Oregon – Climatic conditions play an important role in the reproductive success of mature female Antarctic krill and are a factor in the population fluctuations that occur every five to seven years, according to a new study from Oregon State University .
Environmental factors, including large-scale climate models that affect food availability, influence the overall health of females during the spawning season. While these climate patterns are natural, they tend to heat up and become more intense due to climate change, which is likely to have a negative impact on the krill population, said Kirsten Steinke, a doctoral student working with the oceanographer biologist Kim Bernard at the State of Oregon.
“This ecologically important species serves as the basis of the food chain in the Antarctic Peninsula, supporting everything from whales and penguins to seabirds,” said Steinke, the study’s lead author. âUnderstanding the link between the environment and population health is essential for predicting future demographic trends and responses to climate change in the krill population. “
The results were recently published in the journal Series on Advances in Marine Ecology. The co-authors are Bernard, Associate Professor in the College of Earth, Ocean and Atmospheric Sciences, OSU; and Robin M. Ross and Landgon B. Quetin of the University of California, Santa Barbara.
Antarctic krill, also known as Euphausia superba, is a type of zooplankton that can live for five to seven years and reach a length of just over two inches.
The western Antarctic Peninsula harbors a significant portion of the Antarctic krill biomass. This is also where most of the krill fishing takes place; it is the largest fishery in the Southern Ocean, with around 313,000 tonnes harvested in 2018. Krill is used as a feed for fish farms and as a source of supplements such as omega-3 oil.
“This region is of crucial importance as it is both a popular fishing ground and one of the largest krill spawning grounds and is also warming faster than other parts of Antarctica.” , said Steinke. âThere has been a notable contraction of the population towards the poles and a decrease in the size of the population in recent years. “
Previous research has shown that the Antarctic krill population fluctuates on a five to seven year cycle. The objective of this new research was to better understand the factors that influence population fluctuations.
âYou tend to see two years of high krill recruitment, which means a high proportion of juvenile krill in the population, then a crash, and then the population starts to rebound again,â said Bernard, who has spent a lot of time in the population. Antarctica to study krill. , including a winter at Palmer Station with Steinke. âUnderstanding what drives this cycle is essential. “
Using krill population data from 1993 to 2008, the researchers found a relationship between the condition of female krill of reproductive age during the breeding season and the proportion of juvenile krill the following year; when mature females were in better condition, there were more juveniles in the population the following year.
The degree of reproduction of krill is affected by the length of the spawning season, the lot size per female per spawning period, the number of mature females in the population, the presence of older mature females in the population, or a combination of these elements.
The researchers also found that fluctuations in large-scale climate models and seasonal variations in climate are the main drivers of the health of mature female krill during the spawning season.
The climate in the western Antarctic Peninsula is primarily determined by the annual southerly mode, or SAM, and the multivariate El Ninoto Southern Oscillation Index, or MEI. Both of these climate models have the capacity to affect the availability of food for Antarctic krill, and in particular the resources for mature females.
SAM and MEI are natural climate models, but they change as the planet warms. The SAM in particular had a positive trend, which meant it was hotter and more intense. This positive phase is expected to continue under climate change, Bernard said.
“SAM has been shown to be very important for the health of female krill,” she said. “As SAM continues to have a positive trend, it will continue to warm up, suggesting a negative effect on the general condition of female krill during its spawning season.”
The researchers also found that seasonal variations in SAM and MEI can affect the health of mature female krill. This is likely due to how SAM and MEI are known to affect environmental conditions, Bernard said. Overall, warmer conditions tend to negatively impact the health of female krill of childbearing age, but these impacts can vary depending on the season in which they occur.
Understanding these nuances could help fisheries managers make decisions when conditions in the spring, fall or winter lead to a less than ideal spawning season. The research underscores the importance of considering the impact of climate change as part of the management of Antarctic krill fisheries, Bernard said.
âIt’s really essential to start including the impacts of climate change in the plan,â said Bernard. âThe Antarctic krill is a super unique and fascinating species. So many predators feed on it. If you had a collapse in the krill population, you would put all of those populations at risk. “
AdÃ©lie penguins, for example, feed on mature female krill because they are high in fat, a nutritional benefit that helps penguin chicks survive their first year.
âIf there is a lot of mature female krill, the chicks can get bigger and survive the winter,â Bernard said. “But the AdÃ©lie penguin population has fallen in the northern parts of the Antarctic Peninsula in recent years, in part due to changes in the krill population.”