Brigid McKenna

Acidification and Oyster Mortality


Acidification and Oyster Mortality

Image courtesy of Martha's Vineyard Shellfish Group

Image courtesy of Martha's Vineyard Shellfish Group

Rising pH Levels Linked to Increased Spat Mortality. Economic, Ecological and Social Impacts on West Coast Oyster Industry

Ocean acidification is a present and future threat to a variety of ecosystems and biological processes (detailed in the OCEAN 30 issue by Safe Harbor), and one of the more recent and publicized victims of global warming is the oyster industry of the United States’ West Coast.

The oceans act like carbon sinks, and anthropogenic fossil fuel emissions have caused seawater to be 30% more acidic than pre-industrial times on a logarithmic scale. The eastern Pacific of the United States is particularly vulnerable to this decrease in pH because it already experiences deep upwelling and therefore inherently encounters more extreme acidic conditions more often. The driving force for the oyster farm failures along this shoreline is the inability for young oysters (known as spat) to develop successfully. The oysters are most vulnerable when young and just forming their calcium carbonate shells. This failure to thrive is due to a combination of extra energy required to form a shell (due to lack of necessary ions in the water now bound by acidic molecules) and possibly even dissipation of the fragile shells themselves.

Seed production in the Pacific Northwest plummeted 80% between 2005- 2009, with majority of the larvae dying within merely 2 days. To put into perspective how problematic this is the shellfish industry in this region contribute more than $250 million dollars to the economy annually and provides jobs for over 3,000 individuals. Parallel studies have started on the East Coast comparing conditions and bracing for future ocean acidification catastrophes. New Bedford, Massachusetts, is a major American port with shellfishing making up over 70% of its productivity, so job losses and community demographics would irreparably change for the worse if it is subjected to the consequences of ocean acidification like the Northwest Pacific has.

There has been much active research studying the mechanisms of spat failures and possible ways to rectify this problem both short and long term.  One example is Bodega Bay Marine Lab of UC-Davis working with Hog Island Oyster Company based in Tomales Bay, California. Hog Island raises their oyster spat in different water conditions in order to see the effects of various water quality scenarios, including excessive rain, water run-off, on the seed. The seawater of these tanks can be modified in real time if shell degradation is observed and documented for future hatcheries. Bodega Bay Marine Lab in turn records these fine scale aquatic changes in real time. It models how projected increased acidity will affect oysters and other shellfish in 10, 50 and 100 years in the future, and also how possible adaptations to counteract these caustic circumstances could help or hurt the oyster harvests.

Many of these susceptible oyster farms in the Pacific Northwest are multi-generational, family run companies who have to quickly troubleshoot this regional (and imminently global) disaster by changing techniques, importing spat, and monitoring water chemistry in order to adapt. One family, the Taylors of Shelton, Washington, have a separate oyster hatchery prior to planting in the Puget Sound. Hatcheries have been forced to incessantly monitor the incoming seawater acidity and either shut down flow is the water is too corrosive or add seagrass or sodium carbonate to help neutralize it more. This is a drastic change of how these companies have done things historically, but these alterations are a necessity in order to adapt to the changing seawater.

This, however, is just a stop gap. Models predict that corrosive water will be more prevalent at the sea surface and ubiquitous, up to 150% more, by the end of the century. The oyster harvest in the Northwest Pacific could increase by 25% over the next 50 years. This area is the canary in the coal mine- it is the first to show effects of increased acidification and gives insight on the dynamics of how these sensitive ecosystems will react. There are many short and long term strategies being constructed in attempts to rectify the situation, especially because of potential devastating consequences rippling up the entire food web. This research alone, costs from tens to hundreds of million dollars to complete. It is not cheap researching this evolving problem due to fossil fuel emissions; however, losing any of these shellfishing stocks would be detrimental on a much larger scale and immeasurable effects to local economies.

Thank you to OCEAN Researcher Brigid McKenna

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Gulf of Maine Fisheries

This year's winter shrimp fishery in Maine failed to produce. The shrimp fishery failure has significant economic impacts for coastal communitiesThe possible causes may be changing water temperatures, poor management decisions, or over fishing. The shrimp fishery targets female shrimp just before they lay their eggs. The greater question is what lies ahead, socially, economically, and ecologically.

“Where have all the shrimp gone?”

            One of New England’s most historically prolific fisheries is now in jeopardy with an uncertain future. The shrimp industry, which has been predominately utilized by Maine fisherman for over half a century, may be facing a new threat that could potentially cease its existence as we know it. The 2013 season has been lining up to be one of the least productive in its history, and if it gives insight to the oncoming years, then its outlook is bleak.

Shrimp cultivation in the Gulf of Maine has not been without its fluctuations and modifications. It formally began in 1938, as an inshore winter fisheries. It subsequently expanded to an offshore, year round endeavor that peaked in 1969, collapsed in 1977, and shut down in 1978.  As a result of these events, stricter management was enforced to stabilize the stock. This meant limiting the season to three months peaking in late winter, setting daily and yearly limits as to how much may be caught, and even stipulating how many days per week one could fish. Additionally, the stock biomass level, a number calculated to support maximum sustainable yield and prevent overfishing, is set and referenced for these quotas. Since there is such range from year to year, federal and state agencies work together to constantly assess and compromise in consideration of both the shrimp and fishermen’s interests.

Exploitation of North Atlantic fisheries had not been limited to shrimp. Sardine canneries were once a fecund business in the U.S. beginning in the 19th Century, with over 400 factories based in Maine alone. Consisting of multiple species of herring, these small fish packed together proved to be a lucrative endeavor providing jobs in Maine until 2010, when the last processing facility in the country closed its doors. This was attributed to a difficult combination of decrease in consumer demand and an increase in government regulations for cultivating these fish.

Despite all of these cautionary measures put into place to preserve this shrimp stock, there has been a steady decline of shrimp caught in recent years, and may be the worst since it bottomed out in the late 70’s. In 2011, 13.3 million pounds of shrimp were netted, followed by 5.3 million in 2012. This year fishermen have been struggling to even reach half of the substantially lower allowable quota of 1.4 million pounds. Prices are reflecting this “bust,” and are close to $3.00 more per pound than last year. Regulators have attempted to assist fishermen with this struggle by loosening stipulations but it has not initiated a positive effect.

Some may argue that this stock came close to (or even teetered on) the tipping point previously when it had crashed completely in 1977, but then successfully rebounded. However, this occurrence was attributed to overfishing practices that were then corrected to allow regrowth of the population. It is thought that this recent trend of population decline could be due to warming ocean temperatures, an environmental variable much more difficult to influence.

The life cycle and seasonal transitions of the Gulf of Maine northern shrimp (Pandalus borealis) have been cited as to how the fishery is managed. Mature shrimp live offshore where they mate late summer to early fall. Mature females carry the embryos until they travel inshore to release the larvae. These spawning females are the main target of the fisheries because of location, quality and sustainability. The shallow position they dwell in throughout winter makes trawling easier and safer. These are the best quality because post-hatching females deteriorate in body condition. It maintains the specie’s viability due to the fact that these females spawn once and die, so the practice is not taking any productive females out of the ecosystems.

Through much research efforts it has been determined that this annual migration inshore is temperature dependent, meaning that changing oceanic temperatures would have a significant impact on these crustaceans. These northern shrimp have adapted to local temperatures and, accordingly, mating occurs to coincide with phytoplankton blooms. Phytoplankton is the main food source of the larvae, and being off by a slight period of time, even a week, has been argued to have a monumental impact. Female shrimp carry their eggs for almost half a year, and evolved to release hatchlings when food is most abundant. Eggs hatching too early lead to a poorer survival rate and these shrimp are not capable to adapt fast enough as temperatures drastically change.

The question at the forefront of this issue is: what is causing this temperature increase in our oceans? This is a controversial topic at present with convoluted hypotheses. Could it be the naturally occurring North Atlantic Oscillation or Arctic Oscillation links? Is it due to an anthropogenic global warming? There is much research being conducted to find out exactly what systems are active to cause these climate changes, and it is also logically possible that it could be a combination of nature and manmade influences. No matter what, a likely certainty if this “trend” continues is that the Gulf of Maine northern shrimp stock will not be the only shrimp fisheries negatively affected down the road and we must be prepared for what the future may hold if this is the case.

Thank you to OCEAN Researcher Brigid McKenna

Works Cited

Clark, Stephen, Steven Cadrin, Daniel Schick, Paul Diodati, Michael Armstrong and

David McCarron. “The Gulf of Maine Northern Shrimp (Pandalus borealis) Fishery: a Review of the Record.” Journal of Northwest Atlantic Fishery Science 27 (2000): 193-226. Web.

Gill, Victoria. “Shrimp tuned to ocean temperature.” BBC News, 7 May 2009. Web. 7

May 2009.

“Gulf of Maine shrimp fishery goes bust.” Associated Press. Morning Sentinel, 13 Mar

2013. Web. 13 Mar 2013.

Richards, Anne, Jay O’Reilly and Maureen Taylor. “Oceanographic Indicators of Fishery

Management of Northern Shrimp (Pandalus borealis).” NOAA Research proposal (2006).

Rudalevige, Christine Burns. “Maxing out the mini season for Maine shrimp.”

24 Jan 2013. Web. 24 Jan 2013.

Visbeck, Martin, James Hurrell, Lorenzo Polvanis and Heidi Cullen. “The North Atlantic

Oscillation: Past, present, and future.” Proceedings of the National Academy of Sciences of the United States of America. 98.23 (2001): 12876-1877. Web.


The Devastation by Cyclone Cleopatra


In mid-November 2013, Cyclone Cleopatra tore through the Italian island Sardinia, exacting long lasting damage in a matter of hours. The intense extratropical cyclone poured almost 18 inches of rain in an hour and a half and nearly destroyed this beloved western Mediterranean tourist destination. When rivers broke their banks it caused flash floods that swept away cars, washed bridges out and took the lives of at least 18 people.  

          A cyclone, by definition, is a system of winds that rotate around a low pressure area. They belong to a low pressure storm family that are categorized as cyclones, typhoons or hurricanes depending on geographical region. There are a variety of cyclone magnitudes ranging from mild to severe, with the largest of the low pressure systems being cold core and, as in this circumstance, extratropical. These mid-latitude cyclones can occur any time and are present in both hemispheres, and during the winter and when severe they are generally called “nor’easters.” Extratropical cyclones form as waves along weather fronts, and favor warm sea surface temperatures and atmospheric instability. Cyclone Cleopatra developed from northern cold air entering the Mediterranean and interacting with humid warm air, and because of increased sea surface temperatures due to climate change, it is highly possible that global warming strengthened this system since the difference between air and water temperature would be larger than before.           

           There was no choice by Italian officials other than to declare a state of emergency for this region within 24 hours of Cyclone Cleopatra’s commencement. It has been estimated that over 2,000 people had been affected by this natural disaster and £17 million for emergency relief has been allocated by the Italian government. The northeastern port city Olbia was among the most severely hit, and areas had been submerged in almost 10 feet of water-ruining roads and destroying homes.  For comparison, the amount of water that fell in 90 minutes is comparable to the rainfall in the city of Milan over 6 months. A local mayor deemed the storm “apocalyptic,” and experts have stated that this locale has not experienced a storm of this calibre in centuries. Other towns were hit by heavy rains as well coupled with gale force winds, and the heavy rains continued to threaten other parts of Italy, including Rome and Venice, while moving east days later.

          The geography of Sardinia has been devastated by Cyclone Cleopatra with its heavy rainfall and winds up to 58 mile per hour. Crops were ripped up and mud was spread across the landscape, which will affect agriculture production indefinitely in the region. Sardinia’s road and bridge infrastructure have been broken and severely damaged. This will not only impede access for relief efforts in the area but also yield the high priority task of rebuilding and repairing immediately. Italy has been in a fiscal recession for over two years, so these responsibilities may have unforeseen consequence by taking a higher toll on the unstable government and complicating restoration plans.

          There are bureaucratic complications to this tragedy as well. Italy has experienced more than two years of recession so may not be well prepared to deal with this unexpected crisis financially. An alert system was in effect but the efficiency of it is questionable since evacuation orders had been ignored and it has been said that the weather predictions were understated. Though this event was due to a variety of factors, the risk was said to have been heightened by faulty construction of buildings, especially in coastal areas, and need for better emergency planning.

          Needless to say that Cyclone Cleopatra has left a long road of healing and repair for the people of Sardinia. With climate change being very real, and the anthropogenic contributions to it, the potential of this or storms like this occurring again seems to be likely. Hopefully better, advanced preparations for these devastating natural disasters will minimize future detrimental effects and mortalities.  

Thank You to OCEAN Researcher Brigid McKenna

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