Scaling climate effects from individual physiology to population responses

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2017

End date

12/31/2020

Budget

1,157,676 EUR

Fundings

Abstract

Although a few compelling case studies have demonstrated biological effects of global warming, a common denominator of these studies is that they tend to focus on populations, communities, and ecosystems. However, it is necessarily individuals that feel and respond to changes in the environment. The sum of environmental influences on an individual determines its survival and ability to reproduce and grow, which are the links between individual traits and population dynamics. A central component of climate change and of great physiological importance is an increase in temperature. In this project we have therefore examined to which extent temperature affects maturity, spawning and early life stages survival. The project has resulted in major advancements in knowledge within this research field, based on integration of experimental studies, field sampling, time series analyses and further developments of migration models (consulting also data-storage tag information). A spawning temperature above 10 deg C results in negative effects on a series of reproductive traits: 1) increased prevalence of atresia (resorption of developing oocytes), 2) declining levels of estradiol, 3) significantly altered gene expressions, and 4) decreasing sperm activity (velocity). Consulting the data-storage tag information, environmental temperature stands out as being important for selection of spawning depth, but an individual seems to return very much to the same spawning ground indicating a well-developed adaptive capacity in this regard. Improvements in geolocation algorithms have been important, but further works continue. Barents Sea cod show delayed spawning time at higher water temperature. This unexpected result may be explained by longer periods of feeding at high latitudes, i.e., near the ice edge, and thus lower experienced temperature during gonad maturation (prior to spawning). We found that larger cod typically spawn earlier than smaller cod, supporting our original hypothesis that this earlier spawning will increase the chances of the larvae matching temporally the advanced peak prey (zooplankton) availability in warmer waters, which is a basis for enhanced survival. In contrast, small cod appears not to spawn sufficiently early despite the higher temperatures, resulting in more of a mismatch with larval prey. Consequently, the early spawning of large females seems to be a precondition for increased early stage recruitment in warm years. The 3.5 year project is now ended (December 2020). Several articles have already been published, and new ones will appear in 2021.