Holocene DNA sequences – a dream come true

Abstract

Microscopic marine planktons have played a major role in the Earth's ecosystem and accounts for half the globe's primary production. Predicting the fate of marine planktons is imperative to understanding how ocean life will change in future centuries and how organisms have adapted to changes in the past over long timescales (over thousands of years). Studies of revived resting spores of marine diatoms will serve as excellent proxies of environmental change in marine environments. Thus far, only about a century old marine diatom resting spores could be revived. This severely limited the use of diatom resting spores to investigate the effects of environmental perturbations over longer time scales. Here, we, for the first time report revival of thousands of years old resting spores from the deposits of ancient diatoms (Chaetoceros) in sub-seafloor sediments using a revival protocol that involved recreating the ancient environmental conditions (salinity, temperature and light). Our revived diatom resting spores samples range from recent (0-80 years) to ~7200 years old. Importantly, we also extracted the DNA from the ancient resting spores of Chaetoceros species from the Baltic Sea. Our findings will enable us to compare DNA sequence data obtained from these natural archives of resurrected organisms and provide predictive models to forecast evolutionary responses of natural populations to environmental changes resulting from natural and anthropogenic stressors, including climate change Significance StatementOur results address the important topic of adaptive evolution in marine species due to climate and environmental change induced due to anthropogenic perturbations. We present a new model system Chaetoceros muelleri which will help us address important evolutionary and long-term adaptation questions across evolutionary timescales. Our study reports (1) the revival of recent (0-80 years) to ancient (7200 years old) resting spores of Chaetoceros (2) the extraction of DNA and amplification of chloroplast and ribosomal genes from recent and ancient (~1300 years old) resting spores of Chaetoceros (3) Radiocarbon dating to determine age of sediments (4) Identification of species by reviving the resting spores (5) Baltic sea an excellent ecosystem to study long-term effects of environment on species adaptation

Tolerance of Benthic Diatoms to Severe Environmental Stress: A Case Study in Shatt Al-Arab River, Basrah, Iraq

“…Resting cells and spores are also resistant to dark, cold and nutrient limited conditions (McQuoid & Hobson, 1995). According to Sanyal et al (2019), resting spores of diatoms can survive for centuries in nature and the diatoms spores are still viable if the perfect conditions are given. The present results showed that the germination period for most of the species exposed to desiccation can occur within a short period, mostly after 72 hours after return of natural conditions, which coincide with Sanyal et al (2019).…”

Revival of Ancient Marine Dinoflagellates Using Molecular Biostimulation

“…Some of these dormant propagules can be stored and accumulate in the environment. In marine sediments, resting stages are observed for marine ciliates (Verni and Rosati 2011), sponges (Simpson and Fell 1974), jellyfish (Kawahara et al 2013), zooplankton (Radzikowski 2013), and many taxa comprised of phytoplankton such as cyanobacteria (Perez et al 2017), diatoms (McQuoid et al 2002, Sanyal et al 2019, dinoflagellates (Anderson andRengefors 2006, Ellegaard and, prasinophytes, and haptophytes (Ellegaard et al 2016).…”

“…Marine propagules can be used to determine the effect of environmental changes on marine ecosystems (Dale et al 1999, Brede et al 2009, Harnstrom et al 2011. For instance, the research field of resurrection ecology is based on the revival of organisms in dormant stages that can remain viable for long periods in soils, sediments, ice, and permafrost (Angeler 2007, Orsini et al 2013, Radzikowski 2013, Houwenhuyse et al 2018, Sanyal et al 2019. The term revival is used to designate the germination of seeds, spores, or cysts and/or the hatching of eggs of metazoans.…”

“…Successful germinations were observed in sediments that are more than a century old for dinoflagellate cysts (McQuoid et al 2002, Harnstrom et al 2011, Lundholm et al 2011, Miyazono et al 2012, Feifel et al 2015. A recent study demonstrated the viability and germination of diatom spores in sediments dated up to 7200 years ago (Sanyal et al 2019). For dinoflagellates in particular, resurrection ecology studies have been constrained by the difficulty of inducing germination in enough individuals to accurately represent a past population.…”