Curtin University researchers working on ancient DNA samples from deep sea sediments in the northeast Arabian Sea off the coast of Pakistan have revealed the survival story of up to 43,000-year-old single-celled marine planktons, which were exposed to long-term episodes of environmental stress.
The research, published in the journal Earth and Planetary Science Letters, analysed the impact of expanding oxygen minimum zones or OMZs on plankton communities over the last 43,000 years in the Arabian Sea.
Lead author Mr Kuldeep D More, from the School of Molecular and Life Sciences at Curtin University, explained that during intense Indian monsoons, increased nutrient availability triggers the widespread growth of algal blooms in the Arabian Sea.
“When the algal blooms die, more oxygen than normal is consumed during their bio-degradation, which creates the widespread formation of OMZs. Previous sediment studies from the same region showed that OMZ intensity changed in correlation with the intensity of Indian monsoons during the last Glacial-Interglacial cycle. We wanted to know how these changes in oxygen levels affected past marine life,” Mr More said.
“Through ancient DNA profiling, we learned that long-term exposure to increased OMZs caused plankton to adapt in various ways, such as shifting to a parasitic lifestyle or forming new symbiotic relationships with other plankton within their habitat. Others went dormant due to the lack of oxygen.”
Co-author and project leader Associate Professor Marco Coolen, from the School of Earth and Planetary Sciences at Curtin, said the study provides insights into how marine ecosystems might adapt to global climate change.
“OMZs are thought to be increasing worldwide due to global warming causing stratification and increased land-use and discharge of nutrients into coastal waters,” Associate Professor Coolen said.
“Long-term exposure to OMZs will cause a disturbance in the marine food web and can ultimately have negative effects on fisheries and local economies.
“However, our data and research on the historical Arabian Sea algal blooms show that the marine ecosystem is resilient enough to return to healthy conditions soon after the OMZs cease to exist.”
The research paper was co-authored by Professor Kliti Grice from the School of Earth and Planetary Sciences at Curtin, along with Professor William Orsi from Ludwig-Maximilians-Universität München, Dr. Liviu Giosan and Dr. Valier Galy from Woods Hole Oceanographic Institution and Associate Professor Lijun He from East China Normal University.
The research was funded by the Research Office at Curtin, the National Science Foundation and the Centre for Dark Energy Biosphere Investigations.
The report, ‘A 43 kyr record of protist communities and their response to Oxygen minimum zone variability in the Northeastern Arabian Sea’ can be found online here.