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Right whales go wrong way

December 9, 2013 in Endangered Species, Marine ecology, Ocean Warming, Wildlife

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A right whale mother and calf: Warmer waters may be changing their feeding grounds Image: NOAA Photo Library via Wikimedia Commons

A right whale mother and calf: Warmer waters may be changing their feeding grounds
Image: NOAA Photo Library via Wikimedia Commons

By Kieran Cooke

One of the world’s rarest whale species seems to have deserted its habitual feeding grounds during 2012 – and scientists think climate change may be a factor.

LONDON, 9 December – A mystery is unfolding in the waters of the North Atlantic. Every summer and autumn, numbers of North Atlantic right whales gather in the waters between the eastern Canadian provinces of New Brunswick and Nova Scotia to feed on massive amounts of zooplankton.

But this year the right whales – one of the rarest and most endangered animals on earth – have not turned up in a stretch of water called the Bay of Fundy.

While no-one is sure what is causing the change in the whales’ behaviour, a report in the Yale environment360 online magazine says alterations in the whales’ feeding patterns are taking place against a backdrop of major climate-related ecosystem shifts throughout the north-west Atlantic Ocean.

The right whale – Eubalaena glacialis – came by its name because it was considered by whalers as “the right whale” to hunt, due to its large concentrations of valuable blubber.  It was also easy prey: adult right whales average between 12 and 16 metres in length and can weigh up to 70 tons. They move relatively slowly through the water and float when killed, making them easy to handle.

Record year

At one stage the North Atlantic right whale was hunted to the point of extinction: in recent years numbers have grown to more than 500 individuals.

Marine scientists are now investigating whether changes in water temperature are responsible for shifting the whales’ food supplies and so causing their migratory pattern to alter.

The main ingredient in the whales’ diet is the zooplankton Calanus finmarchicus. Researchers say there’s been a scarcity of the zooplankton in waters around the Bay of Fundy recently: marine scientists say warming waters in the Gulf of Maine, south of the Bay of Fundy, are one likely cause of the decline.

In 2012 waters in the Gulf of Maine and elsewhere in the north-western Atlantic underwent a sharp rise in temperature due, say scientists, both to long-term climate change and to an unusually warm year in the area. In the continental US, 2012 was the hottest summer ever recorded.

Fleeing the heat

Various marine species, including cod and red hake, have been moving more to the north in recent years. A study by the US National Oceanic and Atmospheric Administration found that of 36 fish stocks examined, more than half were shifting northwards or to greater depths to compensate for warming water temperatures. Lobster and shrimp – vital to the Gulf of Maine’s fishing industry – are also believed to be moving to cooler waters further north.

Shifts in stocks of species at the base of the food chain – phytoplankton and zooplankton – are thought to be due both to warming waters in the north-west Atlantic and to changes in ocean currents.  Scientists have shown that the melt of Arctic sea ice, together with more melting of ice sheets in Greenland and Canada, is likely to mean more freshwater being poured into the north-west Atlantic, leading to increased stratification of ocean waters and alterations in plankton stocks.

But the disappearance of right whales from their usual autumn feeding ground in the Bay of Fundy remains a mystery.  Some have been reported in waters well to the north. In winter, large numbers have been sighted further south, in Cape Cod Bay, off the US coast.

In winter right whales usually move more than 1,000 miles south to breeding grounds off the coasts of the states of Georgia and Florida. Now, with waters staying relatively warm further north, they might be changing their migratory behaviour, deciding not to make the long journey south in the winter months. – Climate News Network

Tiny plankton may have big impact

September 23, 2013 in Adaptation, Arctic, Marine ecology, Ocean acidification

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Scientists check the mesocosms off the coast of Svalbard Image by courtesy of Ulf Riebesell/GEOMAR

Scientists check the mesocosms off the coast of Svalbard
Image by courtesy of Ulf Riebesell/GEOMAR

By Alex Kirby

As the oceans become more acidic because of rising carbon dioxide levels, smaller plankton will thrive at the expense of larger species, with potentially serious effects.

LONDON, 23 September – Some of the most minute forms of marine life may have a significant effect both on more developed creatures and on the oceans’ ability to absorb carbon dioxide.

An international team of scientists has found that the smallest species of plankton thrive when levels of CO2, the main greenhouse gas from human sources, rise and increase the acidity of the oceans.

Writing in Biogeosciences, a journal of the European Geosciences Union, they say this could knock the marine food web off balance and also lessen the oceans’ uptake of CO2, a mechanism which helps to regulate the global climate by absorbing gas which would otherwise heat the atmosphere.

The study took place off the coast of Svalbard, the Norwegian high Arctic archipelago, and was led by Ulf Riebesell, a professor of biological oceanography at the GEOMAR Helmholtz Centre for Ocean Researct Kiel in Germany.

“If the tiny plankton blooms, it consumes the nutrients that are normally also available to larger plankton species,” he says.
But the bigger plankton play an important role in transferring carbon down to the ocean depths. So in a system dominated by the minute pico- and nanoplankton, less carbon will leave surface waters and the oceans could in future absorb less CO2, says Riebesell.

The potential imbalance in the food web may have an even bigger impact. Large plankton are also important as producers of a climate-cooling gas called dimethyl sulphide, which stimulates cloud formation over the oceans. Less dimethyl sulphide will mean more sunlight reaches the Earth’s surface, adding to the greenhouse effect.

The root of the problem is the growing acidity of the Arctic. This, coupled with the availability of nutrients, allows the very smallest plankton to thrive at the expense of their larger cousins.

Natural laboratory

The Arctic seas are among those most vulnerable to acidification, because the cold allows them to absorb more CO2. This increasing acidity is already known to affect some Arctic creatures which use calcium to build their shells, including some sea snails, mussels and other molluscs.

But scientists had not known unil now how acidification alters both the base of the marine food web and oceanic carbon transport. The five week-long field study, conducted in the Kongsfjord in Svalbard, sought to close this knowledge gap.

For the experiment the scientists deployed nine large “mesocosms” – eight-metre long flotation frames carrying plastic bags with a capacity of 50 cubic metres. These bags let researchers study plankton communities in their natural environment under controlled conditions, rather than in a laboratory.

The scientists gradually added CO2 to the mesocosm water so that it reached the acidity levels expected in 20, 40, 60, 80 and 100 years, with two bags left as controls. They also added nutrients to simulate a natural plankton bloom.

They found that, with higher CO2, pico- and, to a lesser extent, nanoplankton grew, consuming nutrients and leaving fewer for larger plankton. “The different responses we observed made it clear that the communities’ sensitivity to acidification depends strongly on whether or not nutrients are available,” Riebesell says.

“…the tiniest plankton benefit from the surplus CO2, they produce more biomass and more organic carbon, and dimethyl sulphide production and carbon export decrease.”

Researchers at two UK universities reported earlier this month that they had found that rising temperatures in the oceans would affect plankton development, upsetting the natural cycles of carbon dioxide, nitrogen and phosphorous.  – Climate News Network

Plankton will suffer as oceans warm

September 8, 2013 in Climate, Marine ecology, Warming

EMBARGOED until 1800 GMT on Sunday 8 September

Phytoplankton off the coast of SW England: Warmer oceans will leave less available to feed fish Image: NASA via Wikimedia Commons

Phytoplankton off the coast of SW England: Warmer oceans will leave less available to feed fish
Image: NASA via Wikimedia Commons

By Alex Kirby

One effect of the warming of the oceans will be to depress the growth of plankton, with consequences for fish and other species that depend on it.

LONDON, 8 September – Researchers at two UK universities have found that rising temperatures in the world’s oceans will affect the development of the plankton on which most marine life feeds.

The research team, from the universities of East Anglia and Exeter, has demonstrated that the increasing warmth caused by a changing climate will upset the natural cycles of carbon dioxide, nitrogen and phosphorous.

This will affect the plankton, making it scarcer and so causing problems for fish and other species higher up the food chain. There are also likely to be implications for climate change, but just what they will be, the team leader says, is far from clear.

Plankton play an important role in the oceanic carbon cycle by removing half of all CO2 from the atmosphere during photosynthesis – the process during which plants and other organisms convert light, usually from the Sun, into energy.
The carbon then falls deep into the ocean and ends up on the sea bed, where it remains safely isolated from the atmosphere for centuries.

But the novel point about the team’s work, published in Nature Climate Change, is their discovery that water temperature has a direct impact on maintaining the plankton’s delicate ecosystem. This means the effects of oceanic warming will affect plankton and drive “a vicious cycle of climate change”.

Researchers from UEA’s School of Environmental Sciences and the School of Computing Sciences investigated phytoplankton – microscopic plant-like organisms which rely on photosynthesis to reproduce and grow.

The lead researcher, Dr Thomas Mock, says: “Phytoplankton, including micro-algae, is responsible for half of the carbon dioxide that is naturally removed from the atmosphere.

“As well as being vital to climate control, it also creates enough oxygen for every other breath we take, and forms the base of the food chain for fisheries, so it is incredibly important for food security.

“Previous studies have shown that phytoplankton communities respond to global warming by changes in diversity and productivity. But with our study we show that warmer temperatures directly impact the chemical cycles in plankton, which has not been shown before.

Higher nitrogen ratio

“We found that temperature plays a critical role in driving the cycling of chemicals in marine micro-algae. It affects these reactions as much as nutrients and light, which was not known before.”

Team members from Exeter developed computer-generated models to create a global ecosystem model which took into account world ocean temperatures, 1.5 million plankton DNA sequences taken from samples, and biochemical data.

As temperatures warm, marine micro-algae appear not to produce as many ribosomes as they do in cooler water (ribosomes join up the building blocks of proteins in cells and are rich in phosphorous).

If their numbers fall this will produce higher ratios of nitrogen compared with phosphorous. The result, says Dr Mock, would be lower plankton productivity, with implications for the marine carbon cycle. He told the Climate News Network: “There will be consequences both for climate change and for marine food webs.

“The oceans may retain less CO2, though other factors, like the stratification of the water layers under the influence of temperature and salinity, may counteract that.

“But warming the oceans and increasing the amount of nitrogen they contain could equally well mean that they can store more CO2 than they do now.

“So there’ll certainly be an effect on climate change, but the ultimate outcome is really difficult to predict. With food webs it’s much easier: we know there will simply be less plankton available for higher species.” – Climate News Network

Volcano ‘did little to lower CO2′

March 21, 2013 in Science

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Eyjafjallajökull's ash cloud in 2010: Plankton did not benefit much Image: Jon Short

Eyjafjallajökull’s ash cloud: Plankton did not benefit much
Image: Jon Short

By Alex Kirby

The eruption almost three years ago of an Icelandic volcano added iron to the seas south of the island. But it disappointed hopes that it would help a natural process to remove much carbon dioxide from the atmosphere.

LONDON, 21 March – Plankton, tiny marine organisms, are a good way of cleansing the atmosphere of one of the main greenhouse gases, carbon dioxide. To do this they need dissolved iron to help them to grow, and if they lack iron then they cannot do much to reduce CO2 levels.

So the eruption in 2010 of an Icelandic volcano gave scientists a perfect opportunity to see how much the cataclysm helped the plankton by showering them with unexpected clouds of iron.

Their verdict, published in the journal Geophysical Research Letters – the volcano certainly helped, but not for long enough to make much difference.

This is a blow to some supporters of geo-engineering, who have suggested that one way to tackle climate change is large-scale seeding of the oceans with iron to stimulate plankton to absorb more carbon dioxide (see our 14 March story, Who will regulate the researchers?).

The volcano’s impact was assessed by a team led by scientists from the UK’s National Oceanography Centre, Southampton, who were on a shipboard research expedition in the area at the time.

When it erupted in April 2010 the volcano, Eyjafjallajökull, hurled clouds of ash several kilometres into the atmosphere, bringing air travel to a standstill across Europe and, in a less noticeable effect, seeding the seas south of Iceland with ash.

In many parts of the ocean the productivity of phytoplankton – microscopic plants at the base of the marine food chain – is limited by the availability of dissolved iron.

In 2007 the team had shown that, after a large spring bloom, phytoplankton in the Iceland Basin failed to grow much because it lacked iron. The scientists wanted to see whether the ash from Eyjafjallajökull supplied enough iron to sustain the spring blooms for longer than usual.

More iron, less nitrogen

 

The team – from Southampton, the University of Cape Town and the Norwegian Institute for Air Research – conducted three research voyages in 2010 investigating ocean productivity in the area affected by ash from Eyjafjallajökull.

They took samples of ash and dust in the atmosphere, and of nutrients in the ocean, and also measured the activity of the phytoplankton.

The chief scientist for the summer research cruise and lead author of the Geophysical Research Letters paper, Professor Eric Achterberg, said: “The high latitude North Atlantic ocean is a globally important ocean region, as it is a sink for atmospheric carbon dioxide, and an area where deep water formation takes place.

“A limit to the availability of iron in this region means that the ocean is less efficient in its uptake of atmospheric carbon dioxide.”

The team found that the five-week eruption supplied dissolved iron to a region of the North Atlantic of up 570,000 square kilometres, increasing the number of phytoplankton cells.

Biological experiments showed that the ash did release the iron which the phytoplankton needed to stimulate their growth. But the effect was short-lived as the extra iron resulted in the rapid removal of biological nitrate, depriving the phytoplankton of the nitrogen which they also needed, a caveat to proponents of this form of geo-engineering.

Professor Achterberg said: “The additional removal of carbon by the ash-stimulated phytoplankton was therefore only 15 to 20% higher than in other years, making for a significant but short-lived change to the biogeochemistry of the Iceland Basin.”

The National Oceanography Centre develops technology for coastal and deep ocean research. It is based in Southampton and Liverpool. – Climate News Network