Circadian rhythms and environmental disturbances ? underexplored interactions

Perjantai 24.8.2018 klo 9.24 - Mikko Nikinmaa

Variation of functions with daily cycles is an important component of environmental responses of organisms, and environmental disturbances can affect daily rhythms. This possibility has been surprisingly little taken into account in environmental studies. For this reason Jenni Prokkola and I have written a commentary on the topic. Its abstract follows:

Biological rhythms control the life of virtually all organisms, impacting numerous aspects ranging from subcellular processes to behaviour. Many studies have shown that changes in abiotic environmental conditions can disturb or entrain circadian (∼24 h) rhythms. These expected changes are so large that they could impose risks to the long-term viability of populations. Climate change is a major global stressor affecting the fitness of animals, partially because it challenges the adaptive associations between endogenous clocks and temperature – consequently, one can posit that a large-scale natural experiment on the plasticity of rhythm–temperature interactions is underway. Further risks are posed by chemical pollution and the depletion of oxygen levels in aquatic
environments. Here, we focused our attention on fish, which are at
heightened risk of being affected by human influence and are
adapted to diverse environments showing predictable changes in
light conditions, oxygen saturation and temperature. The examined
literature to date suggests an abundance of mechanisms that can
lead to interactions between responses to hypoxia, pollutants or
pathogens and regulation of endogenous rhythms, but also reveals
gaps in our understanding of the plasticity of endogenous rhythms in fish and in how these interactions may be disturbed by human
influence and affect natural populations. Here, we summarize
research on the molecular mechanisms behind environment–clock
interactions as they relate to oxygen variability, temperature and
responses to pollutants, and propose ways to address these
interactions more conclusively in future studies. (Source: Prokkola JM, Nikinmaa M, Journal of Experimental Biology 221, jeb179267)

Kommentoi kirjoitusta. Avainsanat: Photoperiod, Climate change, Xenobiotic

Circadian Rhythms and environmental changes

Keskiviikko 21.12.2016 klo 12.19 - Mikko Nikinmaa

As we are now experiencing the shortest day of the year (5 h 43 min from sunrise to sunset in Turku), it is relevant to think how environmental changes affect naturally rhythmic responses.

This is especially important for temperate and arctic/antarctic areas, where the daylength variations are great. The most important biological rhythm is the 24-h or circadian rhythm, and associated day length changes. The day length and its predictable changes generate a cue for many biological phenomena such as timing of migration, reproduction, feeding and hibernation. However, recent disturbances that man has caused can mean that the rhythms, their lack and cues that result from adaptations of thousands of years become inappropriate. Below are a couple of examples:

We and others have recently observed that cold acclimation reduces rhythmicity in fish. This is appropriate, since all phenomena associated with rhythmicity such as spawning are energy-demanding, and should not take place in short day-length conditions, as primary production, which forms the basis of food chains, cannot occur in low  light. Now, with increasing temperature due to climate change, rhythms get more pronounced and oxygen consumption of fish increases, although food resources would not make it possible.

In eutrophic conditions, oxygen levels vary diurnally being highest at the end of the day and lowest in the early morning. In natural conditions fish have adapted to this appropriately with rhythmicity of hypoxia responses. However, the levels of some pharmaceuticals in natural waters have increased to concentrations that disturb or abolish the rhythm of hypoxia responses. Consequently, fish can succumb to conditions, which they could easily tolerate without the contaminant insult.

Despite the dark times, Merry Christmas

Joulukuusi2.JPG

Kommentoi kirjoitusta. Avainsanat: climate change, xenobiotics, day lenght