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Researchers from the University of Barcelona, in collaboration with a team from Zoological Station Anton Dohrn (Italy), have analyzed the impact of diatom algae on the development of Oikopleura dioica (O. Dioica) , a type of marine invertebrate of zooplankton that plays an important role in the global dynamics of marine food webs and the carbon cycle of the biosphere. The results, published in Biology of communication, show that the biotoxins produced by these algae at the end of flowering can affect the embryonic development, and therefore the reproduction of O. Dioica, with serious ecological consequences.
The study is particularly relevant, as ocean acidification and climate change-induced warming may intensify the frequency of harmful algal blooms such as diatoms.
Diatoms are a type of microalgae that contribute to photoautotrophic marine phytoplankton production, as they provide nutrients to all other life forms without sunlight. However, diatoms can produce biotoxins (polyunsaturated aldehydes) as a defense mechanism against predators such as copepods. These substances are liberated massively at the end of flowering and can modify the biology of the marine animals of the region.
The new study analyzed the impact of these biotoxins on O's development. dioca, a type of marine invertebrate of appendicular chordates (Appendicularia or Larvacea). Appendiculae are key organisms in the ocean food chain, since they treat about 10% of the primary production of the ocean and serve as food for fish larvae of the marine food chain.
"The results show that biotoxins produced by diatoms can result in significant alterations in the development of O. Dioica, inducing a phenotype called" golf ball ", which affects embryogenesis morphogenesis and differentiation their trunk and tail, "says researcher Cristian Cañestero. "Although in our study, embryonic malformations occur at higher concentrations than those found under natural conditions, we have also observed fatal embryonic abnormalities at concentrations similar to values measured in nature after flowering," explains the researcher. .
This discovery is particularly relevant given the increased acidification and warming of the oceans, as climate change may intensify the severity and frequency of algal blooms. "It is important to discover how the proliferation of harmful algae and the massive production of toxins can alter the physiology of larvae because of its impact on the marine food web and to predict future fishing problems caused by the change. climate change, "says the researcher.
A potential biomarker of zooplankton
The study also analyzed the gene response of O. Dioica to the impact of biotoxins. "We found that O. dioica could respond to the stress caused by diatoms by delaying zygotic transcription of developmental genes in the early stages and by activating defensive genes (a set of genes protecting the cell against the environment), even at harmless concentrations of proteins, biotoxins in which we have not observed any embryonic alteration, "says Cristian Cañestero.
According to the findings of the study, this response could be part of a mechanism developed during evolution that protects embryos from environmental hazards and that could serve as a potential biomarker. "Defensive genes would constitute a molecular biosensor that marine ecologists could use to control genetic stress in natural populations of appendicitis and other organisms exposed to algal blooms in their habitat and then to evaluate the potential impact of blooms associated with climate change, "says the researcher.
These results open up a new study area for the UB research team. "The article brings the foundations of a new line of research in the field EcoEvoDevo, the intersection between ecology, developmental biology and evolution, which will determine if embryos of marine organisms are ready to react to climate change, "concludes Cristian Cañestero.
Explore further:
Researchers are developing a stress test to predict how diatoms will react to ocean acidification
More information:
Nuria P. Torres-Águila et al. Biotoxins derived from diatom blooms cause aberrant development and gene expression in the appendicular chordate Oikopleura dioica, Biology of communication (2018). DOI: 10.1038 / s42003-018-0127-2
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