Friday, November 30, 2012

Sometimes the cure is worse than the illness...


Pictured: Rotifer.

 I just finished reading a shocking article on ScienceDaily.com.  It covers a study of the toxicity of oil and chemical dispersants in the Gulf of Mexico during/after the 2010 BP Macondo Spill.

 Read on for the disturbing details...


Gulf of Mexico Clean-Up Makes 2010 Spill 52-Times More Toxic; Mixing Oil With Dispersant Increased Toxicity to Ecosystems

ScienceDaily (Nov. 30, 2012) — If the 4.9 million barrels of oil that spilled into the Gulf of Mexico during the 2010 Deep Water Horizon spill was a ecological disaster, the two million gallons of dispersant used to clean it up apparently made it even worse -- 52-times more toxic. That's according to new research from the Georgia Institute of Technology and Universidad Autonoma de Aguascalientes (UAA), Mexico.
The study found that mixing the dispersant with oil increased toxicity of the mixture up to 52-fold over the oil alone. In toxicity tests in the lab, the mixture's effects increased mortality of rotifers, a microscopic grazing animal at the base of the Gulf's food web. The findings are published online by the journalEnvironmental Pollution and will appear in the February 2013 print edition.
Using oil from the Deep Water Horizon spill and Corexit, the dispersant required by the Environmental Protection Agency for clean up, the researchers tested toxicity of oil, dispersant and mixtures on five strains of rotifers. Rotifers have long been used by ecotoxicologists to assess toxicity in marine waters because of their fast response time, ease of use in tests and sensitivity to toxicants. In addition to causing mortality in adult rotifers, as little as 2.6 percent of the oil-dispersant mixture inhibited rotifer egg hatching by 50 percent. Inhibition of rotifer egg hatching from the sediments is important because these eggs hatch into rotifers each spring, reproduce in the water column, and provide food for baby fish, shrimp and crabs in estuaries.
"Dispersants are preapproved to help clean up oil spills and are widely used during disasters," said UAA's Roberto-Rico Martinez, who led the study. "But we have a poor understanding of their toxicity. Our study indicates the increase in toxicity may have been greatly underestimated following the Macondo well explosion."
Martinez performed the research while he was a Fulbright Fellow at Georgia Tech in the lab of School of Biology Professor Terry Snell. They hope that the study will encourage more scientists to investigate how oil and dispersants impact marine food webs and lead to improved management of future oil spills.
"What remains to be determined is whether the benefits of dispersing the oil by using Corexit are outweighed by the substantial increase in toxicity of the mixture," said Snell, chair of the School of Biology. "Perhaps we should allow the oil to naturally disperse. It might take longer, but it would have less toxic impact on marine ecosystems."
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The above story is reprinted from materials provided byGeorgia Institute of Technology.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
  1. Roberto Rico-Martínez, Terry W. Snell, Tonya L. Shearer.Synergistic toxicity of Macondo crude oil and dispersant Corexit 9500A® to the Brachionus plicatilis species complex (Rotifera). Environmental Pollution, 2013; 173: 5 DOI: 10.1016/j.envpol.2012.09.024
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Georgia Institute of Technology (2012, November 30). Gulf of Mexico clean-up makes 2010 spill 52-times more toxic; Mixing oil with dispersant increased toxicity to ecosystems.ScienceDaily. Retrieved November 30, 2012, from http://www.sciencedaily.com­/releases/2012/11/121130110518.htm
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Tuesday, November 27, 2012

Antarctic Marine Life

Here's an interesting article from BBC Naturre on Antarctic marine life.  Also below is a link to BBC's Antarctic Ecozone page.
BBC Nature's Antarctic Ecozone Homepage


Antarctic marine wildlife is under threat, study finds

The Southern OceanThe research took place in the Southern Ocean

Related Stories

Marine snails in seas around Antarctica are being affected by ocean acidification, scientists have found.
An international team of researchers found that the snails' shells are being corroded.
Experts says the findings are significant for predicting the future impact of ocean acidification on marine life.
The results of the study are published in the journal Nature Geoscience.
The marine snails, called "pteropods", are an important link in the oceanic food chain as well as a good indicator of ecosystem health.

Ice picks

"They are a major grazer of phytoplankton and... a key prey item of a number of higher predators - larger plankton, fish, seabirds, whales," said Dr Geraint Tarling, Head of Ocean Ecosystems at the British Antarctic Survey (BAS) and co-author of the report.
The study was a combined project involving researchers from the BAS, the National Oceanic and Atmospheric Administration (NOAA), the US Woods Hole Oceanographic Institution and the University of East Anglia's school of Environmental Sciences.
Ocean acidification is a result of burning fossil fuels: some of the additional carbon dioxide in the atmosphere is absorbed into oceans.
This process alters the chemistry of the water, making it more acidic.
Marine snailsPteropods are an important food source for fish and birds
During a research cruise in the Southern Ocean in 2008, scientists assessed the corrosive effects of upwelled water on pteropod shells.
Upwelling occurs when winds push cold layers of deeper seawater from around 1,000m towards the surface layers.
Seawater from these depths is more corrosive to aragonite, the type of calcium carbonate that forms pteropod shells. The point at which this occurs is known as the "saturation horizon".
"Carbonates in shells dissolve more when temperatures are cold and pressure is high, which are the characteristic properties of the deep ocean," Dr Tarling explained.
Scientists found that the combined effect of increased ocean acidity and natural upwelling meant that in some areas of the Southern Ocean the saturation horizon was around just 200m - the upper layer of the ocean where pteropods live.
Dr Tarling explained the significance of these findings: "The snails do not necessarily die as a result of their shells dissolving, however it may increase their vulnerability to predation and infection, consequently having an impact to other parts of the food web."
He said that although upwelling sites are a natural phenomenon in the Southern Ocean, "instances where they bring the saturation horizon above 200m will become more frequent as ocean acidification intensifies in the coming years".
Marine snail shell dissolutionA pteropod (Limacina helicina antarctica) showing acute levels of shell dissolution
Interpreting the results
Dr Tarling said the study is "very much... a pilot study" and that it has provided an important body of work regarding "how pteropods will respond to future oceanic conditions".
To date there have been a number of laboratory studies predicting the effects of ocean acidification on marine organisms, but none assessing the impacts on live specimens in their natural environment.
"It took us several years even to develop a technique sensitive enough to look at the exterior of the shells under high-power scanning electron microscopes, since the shells are very thin and the dissolution pattern, subtle," commented Dr Tarling.
He went on: "We are now undertaking a much more comprehensive programme completely focussed on the effects of ocean acidification, not just on pteropods but to a wider range of organisms."
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Monday, November 19, 2012

Coral "Forests"



NOAA recently had a recent post on its National Ocean Service website.  The video describes a number of different coral environments.

Ocean Service coral video
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Wednesday, November 14, 2012

Hurricane Sandy's Size

Check out the fascinating article by Dr. Jeff Masters, of Weather Undergound, regarding Hurricane Sandy's enormous size.

Hurricane Sandy's huge size: freak of nature or climate change?


Published: 1:10 PM GMT on November 13, 2012
Hurricane Sandy was truly astounding in its size and power. At its peak size, twenty hours before landfall, Sandy had tropical storm-force winds that covered an area nearly one-fifth the area of the contiguous United States. Since detailed records of hurricane size began in 1988, only one tropical storm (Olga of 2001) has had a larger area of tropical storm-force winds, and no hurricanes has. Sandy's area of ocean with twelve-foot seas peaked at 1.4 million square miles--nearly one-half the area of the contiguous United States, or 1% of Earth's total ocean area. Most incredibly, ten hours before landfall (9:30 am EDT October 30), the total energy of Sandy's winds of tropical storm-force and higher peaked at 329 terajoules--the highest value for any Atlantic hurricane since at least 1969. This is 2.7 times higher than Katrina's peak energy, and is equivalent to five Hiroshima-sized atomic bombs. At landfall, Sandy's tropical storm-force winds spanned 943 miles of the the U.S. coast. No hurricane on record has been wider; the previous record holder was Hurricane Igor of 2010, which was 863 miles in diameter. Sandy's huge size prompted high wind warnings to be posted from Chicago to Eastern Maine, and from Michigan's Upper Peninsula to Florida's Lake Okeechobee--an area home to 120 million people. Sandy's winds simultaneously caused damage to buildings on the shores of Lake Michigan at Indiana Dunes National Lakeshore, and toppled power lines in Nova Scotia, Canada--locations 1200 miles apart!

Largest Atlantic tropical cyclones for area covered by tropical storm-force winds:

Olga, 2001: 780,000 square miles
Sandy, 2012: 560,000 square miles
Lili, 1996: 550,000 square miles
Igor, 2010: 550,000 square miles
Karl, 2004: 430,000 square miles



Figure 1. Hurricane Sandy’s winds (top), on October 28, 2012, when Sandy was a Category 1 hurricane with top winds of 75 mph (this ocean surface wind data is from a radar scatterometer on the Indian Space Research Organization’s (ISRO) Oceansat-2.) Hurricane Katrina’s winds (bottom) on August 28, 2005, when Katrina was a Category 5 hurricane with top winds of 175 mph (data taken by a radar scatterometer on NASA’s defunct QuickSCAT satellite.) In both maps, wind speeds above 65 kilometers (40 miles) per hour are yellow; above 80 kph (50 mph) are orange; and above 95 kph (60 mph) are dark red. The most noticeable difference is the extent of the strong wind fields. For Katrina, winds over 65 kilometers per hour stretched about 500 kilometers (300 miles) from edge to edge. For Sandy, winds of that intensity spanned an region of ocean three times as great--1,500 kilometers (900 miles). Katrina was able to generate a record-height storm surge over a small area of the Mississippi coast. Sandy generated a lower but highly destructive storm surge over a much larger area, due to the storm's weaker winds but much larger size. Image credit: NASA.

How did Sandy get so big?
We understand fairly well what controls the peak strength of a hurricane's winds, but have a poor understanding of why some hurricanes get large and others stay small. A number of factors probably worked together to create a "prefect storm" situation that allowed Sandy to grow so large, and we also must acknowledge that climate change could have played a role. Here are some possible reasons why Sandy grew so large:

1) Initial size of the disturbance that became Sandy was large
Sandy formed from an African tropical wave that interacted with a large area of low pressure that covered most of the Central Caribbean. Rotunno and Emanuel (1987) found that hurricanes that form from large initial tropical disturbances like Sandy did tend to end up large in size.


Figure 2. The initial disturbance that spawned Sandy, seen here on October 20, 2012, was quite large.

2) High relative humidity in Sandy's genesis region
The amount of moisture in the atmosphere may play an important role in how large a hurricane gets (Hill and Lackmann, 2009.) Sandy was spawned in the Caribbean in a region where the relative humidity was near 70%. This is the highest humidity we saw during 2012 during the formation of any Atlantic hurricane.

3) Passage over Cuba
Sandy struck Cuba as an intensifying Category 2 hurricane with 110 mph winds. While the core of the storm was over Cuba, it was cut off from the warm ocean waters surrounding Cuba. Most of Sandy's large circulation was still over the ocean, though, and the energy the storm was able to extract from the ocean went into intensifying the spiral bands over water. When Sandy's core re-emerged over water, the hurricane now had spiral bands with heavier thunderstorm activity as a result of the extra energy pumped into the outer portion of the storm during the eye's passage over land. This extra energy in the outer portions of Sandy may have enabled it to expand in size later.

4) Interaction with a trough of low pressure over the Bahamas
As Sandy passed through the Bahamas on October 25, the storm encountered strong upper-level winds associated with a trough of low pressure to the west. These winds created high wind shear that helped weaken Sandy and destroy the eyewall. However, Sandy compensated by spreading out its tropical storm-force winds over a much wider area. Between 15 and 21 UTC on October 25, Sandy's area of tropical storm-force winds increased by more than a factor of two.

5) Leveraging of the Earth's spin
As storms move towards Earth's poles, they acquire more spin, since Earth's rotation works to put more vertical spin into the atmosphere the closer one gets to the pole. This extra spin helps storms grow larger, and we commonly see hurricanes grow in size as they move northwards.

6) Interaction with a trough of low pressure at landfall
As Sandy approached landfall in New Jersey, it encountered an extratropical low pressure system to its west. This extratropical storm began pumping cold air aloft into the hurricane, which converted Sandy into an extratropical low pressure system, or "Nor'easter". The nature of extratropical storms is to have a much larger area with strong winds than a hurricane does, since extratropical storms derive their energy from the atmosphere along a frontal boundary that is typically many hundreds of miles long. Thus, as Sandy made landfall, the hurricane's strongest winds spread out over a larger area, causing damage from Indiana to Nova Scotia.

Are we likely to see more such storms in the future?
Global warming theory (Emanuel, 2005) predicts that a 2°C (3.6°F) increase in ocean temperatures should cause an increase in the peak winds of the strongest hurricanes of about about 10%. Furthermore, warmer ocean temperatures are expected to cause hurricanes to dump 20% more rain in their cores by the year 2100, according to computer modeling studies (Knutson et al., 2010). However, there has been no published work describing how hurricane size may change with warmer oceans in a future climate. We've seen an unusual number of Atlantic hurricanes with large size in recent years, but we currently have no theoretical or computer modeling simulations that can explain why this is so, or if we might see more storms like this in the future. However, we've seen significant and unprecedented changes to our atmosphere in recent decades, due to our emissions of heat-trapping gases like carbon dioxide. The laws of physics demand that the atmosphere must respond. Atmospheric circulation patterns that control extreme weather events must change, and we should expect extreme storms to change in character, frequency, and intensity as a result--and not always in the ways our computer models may predict. We have pushed our climate system to a fundamentally new, higher-energy state where more heat and moisture is available to power stronger storms, and we should be concerned about the possibility that Hurricane Sandy's freak size and power were partially due to human-caused climate change.

References
Emanuel, K. (2005). Increasing destructiveness of tropical cyclones over the past 30 years. Nature, 436(7051), 686-688.

Hill, Kevin A., and Gary M. Lackmann (2009), "Influence of environmental humidity on tropical cyclone size," Monthly Weather Review 137.10 (2009): 3294-3315.

Knutson, T. R., McBride, J. L., Chan, J., Emanuel, K., Holland, G., Landsea, C., ... & Sugi, M. (2010). Tropical cyclones and climate change. Nature Geoscience, 3(3), 157-163.

Rotunno, R., & Emanuel, K. A. (1987). An air–sea interaction theory for tropical cyclones. Part II: Evolutionary study using a nonhydrostatic axisymmetric numerical model. J. Atmos. Sci, 44(3), 542-561.

The Atlantic is quiet, but a Nor'easter expected next week
The Atlantic is quiet, with no threat areas to discuss. An area of low pressure is predicted to develop just north of Bermuda on Wednesday, and the GFS model predicts that this low could become a subtropical cyclone as moves north-northeastwards out to sea late in the week.

The long-range models are in increasing agreement that a Nor'easter will develop near the North Carolina coast on Sunday, then move north to northeastwards early next week. High winds, heavy rain, and coastal flooding could affect the mid-Atlantic coast and New England coasts next Monday and Tuesday due to this storm, but it appears likely that the Nor'easter will stay farther out to sea than the last Nor'easter and have less of an impact on the region devastated by Sandy. Ocean temperatures off the coast of North Carolina were cooled by about 4°F (2.2°C) due to the churning action of Hurricane Sandy's winds, but are still warm enough at 22 - 24°C to potentially allow the Nor'easter to acquire some subtropical characteristics. I doubt the storm would be able to become a named subtropical storm, but it could have an unusual amount of heavy rain if it does become partially tropical. The Nor'easter is still a long ways in the future, and there is still a lot of uncertainty on where the storm might go.

Jeff Masters
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Friday, November 9, 2012

Help! I'm under attack!

Scientists have discovered an interesting form of symbiosis in the ocean involving corals and "protector fish." The fish, when summoned, consume encroaching noxious algae.

Read on in this ScienceDaily.com article...


Corals Attacked by Toxic Seaweed Use Chemical 911 Signals to Summon Help from Fish

ScienceDaily (Nov. 8, 2012) — Corals under attack by toxic seaweed do what anyone might do when threatened -- they call for help. A study reported this week in the journal Science shows that threatened corals send signals to fish "bodyguards" that quickly respond to trim back the noxious alga -- which can kill the coral if not promptly removed.
Scientists at the Georgia Institute of Technology have found evidence that these "mutualistic" fish respond to chemical signals from the coral like a 911 emergency call -- in a matter of minutes. The inch-long fish -- known as gobies -- spend their entire lives in the crevices of specific corals, receiving protection from their own predators while removing threats to the corals.
This symbiotic relationship between the fish and the coral on which they live is the first known example of one species chemically signaling a consumer species to remove competitors. It is similar to the symbiotic relationship between Acacia trees and mutualist ants in which the ants receive food and shelter while protecting the trees from both competitors and consumers.
"This species of coral is recruiting inch-long bodyguards," said Mark Hay, a professor in the School of Biology at Georgia Tech. "There is a careful and nuanced dance of the odors that makes all this happen. The fish have evolved to cue on the odor released into the water by the coral, and they very quickly take care of the problem."
The research, supported the National Science Foundation, the National Institutes of Health and the Teasley Endowment at Georgia Tech, was reported November 8 in the journal Science. The research was done as part of a long-term study of chemical signaling on Fiji Island coral reefs aimed at understanding these threatened ecosystems and discovering chemicals that may be useful as pharmaceuticals.
Because they control the growth of seaweeds that damage coral, the importance of large herbivorous fish to maintaining the health of coral reefs has been known for some time. But Georgia Tech postdoctoral fellow Danielle Dixson suspected that the role of the gobies might be more complicated. To study that relationship, she and Hay set up a series of experiments to observe how the fish would respond when the coral that shelters them was threatened.
They studied Acropora nasuta, a species in a genus of coral important to reef ecosystems because it grows rapidly and provides much of the structure for reefs. To threaten the coral, the researchers moved filaments of Chlorodesmis fastigiata, a species of seaweed that is particularly chemically toxic to corals, into contact with the coral. Within a few minutes of the seaweed contacting the coral, two species of gobies --Gobidon histrio and Paragobidon enchinocephalus -- moved toward the site of contact and began neatly trimming away the offending seaweed.
"These little fish would come out and mow the seaweed off so it didn't touch the coral," said Hay, who holds the Harry and Linda Teasley Chair in Environmental Biology at Georgia Tech. "This takes place very rapidly, which means it must be very important to both the coral and the fish. The coral releases a chemical and the fish respond right away."
In corals occupied by the gobies, the amount of offending seaweed declined 30 percent over a three-day period, and the amount of damage to the coral declined by 70 to 80 percent. Control corals that had no gobies living with them had no change in the amount of toxic seaweed and were badly damaged by the seaweed.
To determine what was attracting the fish, Dixson and Hay collected samples of water from locations (1) near the seaweed by itself, (2) where the seaweed was contacting the coral, and (3) from coral that had been in contact with the seaweed -- 20 minutes after the seaweed had been removed. They released the samples near other corals that hosted gobies, which were attracted to the samples taken from the seaweed-coral contact area and the damaged coral -- but not the seaweed by itself.
"We demonstrated that the coral is emitting some signal or cue that attracts the fish to remove the encroaching seaweed," Hay said. "The fish are not responding to the seaweed itself."
Similar waters collected from a different species of coral placed in contact with the seaweed did not attract the fish, suggesting they were only interested in removing seaweed from their host coral.
Finally, the researchers obtained the chemical extract of the toxic seaweed and placed it onto nylon filaments designed to stimulate the mechanical effects of seaweed. They also created simulated seaweed samples without the toxic extract. When placed in contact with the coral, the fish were attracted to areas in which the chemical-containing mimic contacted the coral, but not to the area contacting the mimic without the chemical.
By studying the contents of the fish digestive systems, the researchers learned that one species -- Gobidon histrio -- actually eats the noxious seaweed, while the other fish apparently bites it off without eating it. In the former, consuming the toxic seaweed makes the fish less attractive to predators.
The two species of fish also eat mucus from the coral, as well as algae from the coral base and zooplankton from the water column. By defending the corals, the gobies are thus defending the home in which they shelter and feed.
"The fish are getting protection in a safe place to live and food from the coral," Hay noted. "The coral gets a bodyguard in exchange for a small amount of food. It's kind of like paying taxes in exchange for police protection."
As a next step, Hay and Dixson would like to determine if other species of coral and fish have similar symbiotic relationships. And they'd like to understand more about how the chemical signaling and symbiotic relationship came into being.
"These kinds of positive interactions needs to be better understood because they tell us something about the pressures that have gone on through time on these corals," said Hay. "If they have evolved to signal these gobies when a competitor shows up, then competition has been important throughout evolutionary time."
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The above story is reprinted from materials provided byGeorgia Institute of Technology Research News, via Newswise. The original article was written by John Toon.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
  1. D. L. Dixson, M. E. Hay. Corals Chemically Cue Mutualistic Fishes to Remove Competing Seaweeds.Science, 2012; 338 (6108): 804 DOI:10.1126/science.1225748
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Georgia Institute of Technology Research News (2012, November 8). Corals attacked by toxic seaweed use chemical 911 signals to summon help from fish. ScienceDaily. Retrieved November 9, 2012, from http://www.sciencedaily.com­/releases/2012/11/121108142740.htm
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Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.
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