Index
- Biotoxin Monitoring
- Maine DMR Vibrio Education
- Shellstock Shading
- Part 2 - Flood Sampling and Repealing a Flood Closure
- Upcoming Events
Biotoxin Monitoring - Focusing on the Microscopic - By DMR Marine Resource Specialist Amy Hamilton Vailea
An important component of ensuring Maine shellfish are safe for consumer consumption is monitoring for Paralytic Shellfish Poisoning (PSP), also known as red tide. People who experience PSP after consuming toxic shellfish can have many different symptoms, the most serious of which are respiratory paralysis which can be lethal if medical attention is not sought in time. PSP and other types of marine biotoxins are caused by naturally occurring blooms of marine phytoplankton. In the Gulf of Maine, spring brings longer days and increased ocean nutrient levels, causing the phytoplankton to bloom. When shellfish ingest these microalgae, toxins are accumulated in their tissues. The phytoplankton genus largely responsible for Gulf of Maine PSP is Alexandrium.
The Department of Marine Resource (DMR)'s Bureau of Public Health monitors extensively for Alexandrium and other types of phytoplankton that are also known to have toxins. This monitoring provides an early warning system for the appearance of biotoxins in shellfish tissue. Once the phytoplankton species of concern reach certain levels of abundance, shellfish samples from the affected area are likely to contain toxin levels that can be harmful to humans. Spanning the full coast of Maine, sixteen phytoplankton stations are monitored year round; monthly during the less dangerous seasons and weekly during the months in which harmful algal blooms are known to occur. These stations have been selected based on their historical ability to indicate the annual bloom patterns. At each station, ten liters of seawater are poured through a fine sieve. The resulting phytoplankton are collected in a small amount of filtered fresh seawater. Back in the lab, the samples from each station are individually examined under a microscope to determine whether the dangerous phytoplankton are present and in what concentration. Additional stations are added as needed in response to a harmful algal bloom event.
In addition to the monitoring conducted by staff, DMR is fortunate to work with a number of highly trained volunteers who add to our understanding of the season's phytoplankton blooms. These dedicated citizen scientists monitor additional stations that DMR does not, collecting and analyzing their own unique phytoplankton samples and submitting the results. Their contributions increase our understanding of phytoplankton concentrations and how the shellfish may be affected. Without this work, DMR's understanding of Maine's harmful algal blooms would not be as complete nor include as much of our vast coastline.
DMR uses these analyses to track the progress of the phytoplankton blooms and direct shellfish tissue testing. We focus on PSP as historically in the Gulf of Maine it has been the most dangerous of the biotoxins caused by harmful algal blooms. However, climate change is causing the occurrence of these toxic events to evolve globally. DMR vigilantly monitors the phytoplankton for changes that could negatively affect Maine's shellfish and their consumers.
A look under the microscope at a sampling of Gulf of Maine phytoplankton with a single Dinophysis acuminata clearly visible at top right. Photo credit: DMR phytoplankton volunteer Jennifer Shack
Maine DMR Vibrio Education
Vibrios are a naturally occurring bacteria typically found in marine waters. Several species of Vibrio are pathogens and can cause illness in humans including gastroenteritis and septicemia. Illnesses from Vibrio infections are often associated with the consumption of raw or undercooked seafood including bivalve shellfish. Bivalve shellfish are filter feeders, meaning they feed by straining the surrounding water in order to collect food particles; these particles (including bacteria) can then become concentrated in their guts. Vibrio spp. are present throughout the marine environment, but pathogenic strains tend to be associated with warmer waters. If Vibrios are already present in shellfish, they can multiply exponentially within harvested bivalves which are exposed to warm temperatures such as the exposed deck of a boat on a sunny day in August or an un-shaded summer picnic table. Research indicates the growth rates of Vibrio parahemolyticus (Vp) within harvested bivalves are determined by temperature; at 90 degrees F the Vibrio population will double every hour, at 80 degrees F it takes about two hours, at 60 degrees F it takes over a day for the bacteria population to double, and below 50 the growth of Vp essentially stops. The best way to keep bivalve shellfish safe from Vibrio contamination is by observing temperature controls including cooling product as quickly as possible after harvest. This applies to recreational harvesters and retail purchases as well; keep your catch or purchase in a cooler with an icepack until you are ready to enjoy it!
Maine has recently implemented a Vibrio Control Plan through regulation. The enactment of Chapter 115 Vibrio parahaemolyticus Control Plan, establishes handling requirements for oysters and hard clams harvested from the Damariscotta River north of a line beginning at Montgomery Point, Boothbay, and running southeast to Jones Point, South Bristol. The additional handling requirements are designed to avoid an illness outbreak scenario that would trigger extensive closures. In addition to attending mandatory annual training, harvesters and certified shellfish dealers are required to submit a harvest plan to the Department of Marine Resources by March 1 of each year demonstrating the method to be used to achieve internal temperatures of 50 degrees Fahrenheit in harvested oysters and clams. In addition, the Rule imposes maximum time periods for exposure to ambient air prior to cooling, and resubmergance criteria if the time periods are exceeded. The standards are more stringent if ambient temperature reaches 80 degrees Fahrenheit or above. The rule prohibits harvesters from selling from their homes and prohibits recreational harvest during the control months, exempting Limited Purpose Aquaculture license holders who are harvesting from their licensed site.
The best defense against the threat of Vp in Maine shellfish is education of the industry and consumers, as well as a commitment from harvesters and dealers to adhere to time/temperature controls and the new Vibrio Control Plan. Keep Maine shellfish safe by keeping it cool!
Shellstock Shading - By DMR Seafood Inspection Supervisor John Fendl
we're in that time of year where temperatures are climbing, both in the air and in the water. While it comes as a welcome relief from the long cold winters, it also creates an excellent breeding environment for bacteria. A major concern in the shellfish industry is the control of Vibrio bacteria. This is naturally occurring in the marine environment and harmless to the shellfish itself but if we humans ingest it we can become seriously ill. This is particularly important with shellfish that are consumed raw since there is no cooking process that will destroy the bacteria. Keeping your shellfish clean and cold is paramount for healthy consumption and it starts as soon as the shellfish is harvested. If you are out in the hot sun and the temperature is rising, one of the first things you want is shade. Shading works well for shellfish too, in fact it's a requirement for harvesters that participate in a Vibrio management plan. A certified dealer is required to transport shellstock in an enclosed, refrigerated truck. Shading for a harvester can come in many different forms such as a cap for the truck bed or a tarp covering the totes. Whatever you use should be clean and not a cross contamination hazard for the shellstock. Seaweed is NOT suitable shading because it is loaded with bacteria from the marine environment and should not be placed on shellstock.
The second part of keeping it clean and cold is obviously keeping it cold. When you combine shading with temperature control you have a very effective defense against bacteria growth. Placing shellstock in some type of insulated container with ice is the best method. The key here is that the container MUST have an open drain in the bottom to prevent any water buildup, and the ice must be from a clean source. The best ice is something that Won't drip like a one liter plastic bottle filled with drinking water and frozen. More details about Vibrio Control Plans can be found in DMR Regulation Chapter 115.
Part 2: Flood Sampling and Repealing a Flood Closure - By DMR Scientist Erick Schaefer
This is a follow up to an article in the Winter 2016 Maine DMR Public Health Newsletter on the procedure for flood closures
Now that the flood closure is in place what happens next?
DMR Growing Area Staff pre-selected an array of sampling stations located from Kittery to Calais to be used during flood events. These sample stations were selected using the following criteria:
- Located in Approved or Conditionally Approved areas (not rainfall areas)
- Able to be sampled under most tide conditions (prevents missed stations)
- Easy access for staff (for quicker collection)
- Located in high priority areas for wild harvest or aquaculture
- Located to facilitate targeted re-openings (drawing lines to open half a bay for example)
Once these stations were selected they were than grouped together in flood runs based on the ability to collect all samples and return to the lab in an 8-10 hour time period. As an example, in Eastern Maine there are 4 runs with 48 total sample sites that cover from the Penobscot River to the St. Croix River. These runs are between 150-250 miles in length.
Once a flood closure has been put in place the protocol is to wait 48 hours and then start flood sampling. We wait 48 hours to allow the initial bacterial pollution to dilute as well as allowing time for pollution from the upper drainages to reach the receiving waters. Once sampling is initiated it continues on a daily basis (weekends and holidays included) until the flood closure is completely lifted.
Samples are brought to the regional lab (Boothbay or Lamoine) where they are set up by lab staff using the membrane filtration method. This test is a 24 hour test so samples set up on a Monday are read out on Tuesday. For example, say DMR institutes a statewide flood closure on Wednesday. Staff would start sampling on Friday; samples would arrive at the lab Friday afternoon/evening and be set up by lab staff Saturday morning. These samples would be read on Sunday. The results are sent to senior staff as soon as they are available. Senior staff personnel review the results and determine if any reduction in the flood closure is warranted. If a change to the current flood closure is made, a legal notice and map will be drafted and posted online and emailed to the DMR interested parties list (sign up by selecting the red envelop icon at the bottom of any DMR web page). This pattern of sampling, set up, read out and evaluation repeats until the entire flood closure is repealed.
Flood sampling and flood closure repeal is a team effort involving all DMR Public Health staff from the newest hire to the most senior supervisors. The emphasis is on opening harvest areas as soon as they are clean so folks can get back to work!
Upcoming Events
Municipal shellfish program trainings designed to provide information on running town shellfish programs according to state laws and regulations and are scheduled as follows:
September 6, 2016 10am-12pm- University of Maine at Machias
September 7, 2016 10am-12pm- Ellsworth City Hall
September 14, 2016 10am-12pm- Brunswick Town Office
Please contact Angel Ripley at 633-9515 or find her e-mail address here to confirm attendance to one of the three sessions as space is limited. There is no cost for attendance, and it is strongly encouraged to have a representative from each town with a municipal shellfish program attend.
Shellfish Advisory Council meeting to be held on October 27, 2016 at Ellsworth City Hall-Council Chambers from 10am-1pm.
HOLD THE DATE: Maine will be hosting the annual Northeast Shellfish Sanitation Association (NESSA) meeting April 11-13, 2017 in Freeport. This meeting is open to the public and anyone with an interest in shellfish sanitation and management is encouraged to attend. More information will be released as the date gets closer.