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oyster farmer with bag Oyster farmer with oyster bags, supported by "tables," in the bay of Brest, France. Photo credit: NOAA Fisheries/Mark Dixon, NEFSC
oysters in a tote Oysters in a tote after being cleaned, sorted, and graded. These oysters are destined for the market. Photo credit: NOAA Fisheries/Mark Dixon, NEFSC
scientists calibration aquaculture equipment Hélène Hégaret (LEMAR), Shannon Meseck, Gary Wikfors, and Judy Yaqin Li May (NOAA Fisheries/NEFSC, Milford) calibrate the biodeposition equipment at an oyster farm in the Bay of Brest, France. Photo credit: NOAA Fisheries/Mark Dixon, NEFSC

September 29, 2017
Contact: Heather Soulen

Joining Forces to Understand the Impacts of Harmful Algal Blooms on Aquaculture

On September 17, 2017 Mark Dixon, Judy Li May, Shannon Meseck, and Gary Wikfors from our Milford Laboratory traveled to Brittany in the northwest of France to work with collaborators led by Dr. Hélène Hégaret of the Laboratoire des sciences de l’environnement marin (LEMAR Lab). This was part of a Galway Initiative project studying Harmful Algal Blooms (HAB) interactions with shellfish aquaculture. Harmful algal blooms produce biotoxins – poisons – normally in amounts too small to be harmful. While some biotoxins can be potent with only a small amount leading to illness or death, other less potent biotoxins may accumulate in fish and shellfish. This can cause serious harm, affecting human health and coastal economies. To help understand how HABs can impact shellfish aquaculture, the US-French team conducted biodeposition-method measurements of oyster filtration, feeding, and assimilation at two sites where HABs occur seasonally. While no blooms were occurring at this time, the team collected baseline data and logistics to help with their HAB research in the future. We sat down with Gary Wikfors to learn about this important collaboration.

Q. What are Harmful Algal Blooms (HAB)?

A.Harmful Algal Blooms occur when populations of algae that produce biotoxins flourish under the right conditions. These biotoxins can harm people, fish, shellfish, marine mammals and birds. We pay close attention to these kinds of algae. Our lab was among the first to recognize the effects of microalgal toxins upon bivalves.  We collaborated with French colleagues on this from the start -- oysters are VERY important in France -- and they are doing the most-sophisticated work in the world to advance this science.

Q. Why are oysters so important to France?

A. It’s a cultural thing. A celebration is not a celebration without oysters –especially at Christmas time. There’s investment on the part of the French government almost at every level to make sure this marine resource is healthy and abundant for the future, especially in oyster growing areas like Brittany where the Milford team works.

Q. Why are HABs a concern for the aquaculture industry?

A. Harvest closures because of Paralytic Shellfish Poisoning (PSP), Diarrhetic Shellfish Poisoning (DSP), Amnesic Shellfish Poisoning (ASP) and others are just the start. When shellfish like oysters eat biotoxin-producing algae, the toxin can accumulate in shellfish tissue and when people eat these shellfish, they can become sick with PSP, DSP and ASP. Harmful Algal Blooms can also reduce oyster performance (i.e. growth and survival), making them more susceptible to other environmental challenges and diseases.

To hear how HABs reduces performance and makes oysters susceptible to disease and other stressors, listen to this audio clip.

Q. What is the connection between HABs and biodeposition?

A. The biodeposition method is an innovative way of quantifying filtration, feeding, selection, ingestion, and assimilation of plankton and other little particles in the water in a natural setting. Many HAB and shellfish studies have been done in a laboratory setting with cultured algae, often under very controlled conditions. That’s a great first step, but farmers need to understand the full magnitude of risks imposed by HABs on their farms. We need to document HAB and shellfish interactions in the real world because natural settings tend to be dynamic where there’s other algae, temperature can fluctuate, pH can fluctuate, the tide moves in and out, the salinity goes up and down, the dissolved oxygen changes. All of these things can affect oyster filtration and disease susceptibility. 

To hear more detail about the biodeposition method and what is meant by “natural settings,” listen to these two audio clips.

Q. Why is this kind of study important for the future of aquaculture?

A. Risk analysis, farm siting, options for protecting shellfish from HABs – shellfish aquaculture is expanding at the same time as HABs are expanding in geography and intensity.  We need to understand the challenges to mitigate and manage aquaculture development.

The Milford team hopes to receive funding to return in June 2018 when the HAB bloom of interest will likely be present. During that trip, they hope to place their deposition rig on the oyster farmer’s boat and run their deposition study at the actual farm location and not dockside as the team did this time.

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(File Modified Oct. 03 2017)