Please select your home edition
Edition
Marine Resource 2016

Black Sea rich in ancient genetic data

by WHOI on 10 May 2013
WHOI researcher Alan Gagnon, Marco Coolen (center, in blue safety helmet), and the crew from the Bulgarian research vessel Akademik sample the sediment core that was used for this study. Dimitri Dimitrov, IO-BAS http://www.bas.bg/cgi-bin/e-cms/vis/vis.pl?p=0200
When Woods Hole Oceanographic Institution (WHOI) marine paleoecologist Marco Coolen was mining through vast amounts of genetic information from the Black Sea sediment record, he was astounded by the variety of past plankton species that left behind their genetic makeup (i.e., the plankton paleome).

The semi-isolated Black Sea is highly sensitive to climate driven environmental changes, and the underlying sediments represent high-resolution archives of past continental climate and concurrent hydrologic changes in the basin. The brackish Black Sea is currently receiving salty Mediterranean waters via the narrow Strait of Bosphorus as well as freshwater from rivers and via precipitation.

'However, during glacial sea level lowstands, the marine connection was hindered, and the Black Sea functioned as a giant lake,' says WHOI geologist Liviu Giosan.

He added that 'the dynamics of the environmental changes from the Late Glacial into the Holocene (last 10,000 years) remain a matter of debate, and information on how these changes affected the plankton ecology of the Black Sea is sparse.'

Using a combination of advanced ancient DNA techniques and tools to reconstruct the past climate, Coolen, Giosan, and their colleagues have determined how communities of plankton have responded to changes in climate and the influence of humans over the last 11,400 years. Their results will be published in the Proceedings of the National Academy of Sciences, USA (PNAS), and will be available online on May 6.

Researchers traditionally reconstruct the makeup of plankton by using a microscope to count the fossil skeletons found in sediment cores. But, this method is limited because most plankton leave no fossils, so instead Coolen looked for sedimentary genomic remains of the past inhabitants of the Black Sea water column.

'DNA offers the best opportunity to learn the past ecology of the Black Sea,' says Coolen. 'For example, calcareous and organic-walled dinocysts are frequently used to reconstruct past environmental conditions, but 90 percent of the dinoflagellate species do not produce such diagnostic resting stages, yet their DNA remains in the fossil record.'

However, ancient DNA signatures in marine sediments have thus far been used for targeted reconstruction of specific plankton groups and those studies were based on very small clone libraries. Instead, the researchers used a high throughput next generation DNA sequencing approach called pyro sequencing to look for the overall plankton changes in the Back Sea from the DE glaciation to recent times.


In addition, the researchers reconstructed past changes in salinity and temperature as the possible causes for plankton community shifts in the Black Sea.

To reconstruct the salinity, the WHOI team analyzed sediments containing highly resistant organic compounds called alkenones, which are uniquely produced by Emiliania huxleyi—the same photosynthetic organism oceanographers study to determine past sea surface temperatures. By examining the ratio of two hydrogen isotopes in the alkenones, they were able to map the salinity trend in the Black Sea over the last 6,500 years.

'One of the isotopes, deuterium, is not very common in nature,' explains Coolen, 'And it doesn't evaporate as easily as other isotopes. Higher ratios of deuterium are indicative of higher salinity.'

The WHOI team was funded through the National Science Foundation and they collaborated with Chris Quince and his postdoc Keith Harris from the Computational Microbial Genomics Group at the University of Glasgow, and with micropaloentologist Mariana Filipova-Marinova from the Natural History Museum in Varna, Bulgaria.

Their study revealed that 150 of 2,710 identified plankton showed a statistically significantly response to four environmental stages since the deglacial. Freshwater green algae were the best indicator species for lake conditions more than 9,000 years ago although the co-presence of previously unidentified marine plankton species indicated that the Black Sea might have been influenced to some extent by the Mediterranean Sea over at least the past 9,600 years.

Dinoflagellates, cercozoa, eustigmatophytes, and haptophyte algae responded most dramatically to the gradual increase in salinity after the latest marine reconnection and during the warm and moist mid-Holocene climatic optimum. Salinity increased rapidly with the onset of the dry Subboreal climate stage after ca. 5200 years ago leading to an increase in marine fungi and the first occurrence of marine copepods. A gradual succession of phytoplankton such as dinoflagellates, diatoms, and golden algae occurred during refreshening of the Black Sea with the onset of the cool and wet Subatlantic climate around 2500 years ago. The most drastic changes in plankton occurred over the last century associated with recent human disturbances in the region.

The new findings show how sensitive marine ecosystems are to climate and human impact. The high throughput sequencing of ancient DNA signatures allows us to reconstruct a large part of ancient oceanic life including organisms that are not preserved as fossils.

Coolen added that ancient plankton DNA was even preserved in the oldest analyzed Black Sea lake sediments when the entire water column was most likely well mixed and oxygenated. This means that ancient plankton DNA might be widely preserved in sediments and can likely be used to reconstruct past life in the majority of oceanic and lake environments.

The Woods Hole Oceanographic Institution WHOI) is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans' role in the changing global environment.

Barz Optics - San Juan Worlds Best EyewearHella Marine - July 2016Guy Nowell - Red 660

Related Articles

Reef sharks take small bites
Coral reef sharks eat prey that are smaller than a cheeseburger Sharks have a reputation for having voracious appetites, but a new study shows that most coral reef sharks eat prey that are smaller than a cheeseburger
Posted on 20 Mar
Suburbs to Sea - Stopping litter at the source
Over sixty people gathered at Point Cook Community Centre for a special ‘Movies and Muffins’ night to learn about litter Over sixty people gathered at Point Cook Community Centre recently for a special ‘Movies and Muffins’ night to learn about litter and its impact on the environment as part of Wyndham City’s Green Living Series.
Posted on 18 Mar
Good radio communication tips - Video
Good communications could make all the difference in an emergency at sea. Here's some great basic communication tips Good communications could make all the difference in an emergency at sea. Here's some great basic communication tips from Scott Walker and Mal Williams from Outdoors Group.
Posted on 10 Mar
We can fix the Great Barrier Reef
Leading coral reef scientists say Australia could restore Great Barrier Reef to its former glory through better policies Leading coral reef scientists say Australia could restore the Great Barrier Reef to its former glory through better policies that focus on science, protection and conservation.
Posted on 20 Feb
Great Barrier Reef marine reserves combat coral disease
A new and significant role for marine reserves on the Great Barrier Reef has been revealed A new and significant role for marine reserves on the Great Barrier Reef has been revealed, with researchers finding the reserves reduce the prevalence of coral diseases.
Posted on 20 Feb
Powerboat noise gives marine predators a deadly advantage
A pioneering new study shows the rate fish are captured by predators can double when boats are motoring nearby. A pioneering new study shows the rate fish are captured by predators can double when boats are motoring nearby.
Posted on 8 Feb
More recreational boaties wearing lifejackets
In good news for boating safety, more recreational boaties are wearing lifejackets the entire time they are on the water In good news for boating safety, more recreational boaties are wearing lifejackets the entire time they are on the water. Maritime New Zealand has released new research into recreational boating behaviour that shows in 2015 78 per cent of recreational boaties reported wearing a lifejacket the entire time they were on the water. This is up from 67 per cent in 2014, and 62 per cent in 2013.
Posted on 13 Jan
Eco-warriors Sea-Bin crowd sharing critical stage with nine days to go
The automated marina cleaning SeaBin project has raised 86% of their target with 9 days left. The automated marina cleaning SeaBin project has raised $198,020 of $230,000.00 with nine days left on their Indiegogo crowdfunding platform, but they need more help now.
Posted on 29 Dec 2015
Wellington boatie placed under 'house-arrest'
A boatie who had bought a “tired” yacht for just $500 online has had the vessel restricted to use on Wellington harbour A boatie who had bought a “tired” yacht for just $500 online has had the vessel restricted to use on Wellington harbour after threatening to sail to Westport without an engine, radio or safety equipment. Another online shopper did the right thing in buying an emergency beacon (EPIRB - emergency position-indicating radio beacon) before heading out in his boat.
Posted on 22 Dec 2015
New guidelines published for the servicing of inflatable lifejackets
Some inflatable lifejackets failed because they had not been serviced, and boaties were getting unclear information Concerns that some inflatable lifejackets failed because they had not been serviced, and boaties were getting unclear information, have led to new, national guidelines for safer use of inflatable lifejackets. The guidelines were developed by a nation-wide industry group representing manufacturers, importers, retailers, boating organisations and others
Posted on 14 Dec 2015