The curious case of the haploid giant Irish moss

It was ten days in and ~1,500 km traveled aboard the Polar Prince on Leg 3 of the Canada C3 Expedition. Our days had been filled with incredible experiences, and we were arriving in Charlottetown, Prince Edward Island, our final destination for Leg 3. I was on board for this leg to work on marine biology projects with two other scientists.

For this last stop, I hopped on a bus with others from the group to go to Basin Head in Northeast PEI for a relaxing afternoon on the beach. As I prepared to be a beach sightseer, I had forgotten that at each stop along the route the people from that location were excited to show the expedition some special features of their amazing homes, villages or natural areas. This time was no different. As soon as we got off the bus, we were greeted by a group of enthusiastic Fisheries and Oceans scientists and other naturalists.

Basin Head watershed Marine Protected Area in Northeast Prince Edward Island (image: Google Maps)

As we were introduced to Dr. Irene Novaczek, a seaweed expert and key player in a unique environmental case study occurring in a Basin Head lagoon, I put aside my swim suit and towel and instead pulled out my phone with its almost-dead battery to begin rapidly taking notes. Swatting away mosquitoes and enjoying this lesson in nature with other C3 participants, I dug into the fascinating story that Dr. Novaczek was explaining.

Dr. Irene Novaczek showing us the study site in Northeast Prince Edward Island. (Photo: BJGS)

Dr. Novaczek explained to us that the Irish moss Chondrus crispus is an abundant seaweed species that grows along rocky parts of the Atlantic coast of Europe and North America. This seaweed is an important industrial source of carrageenan, a thickener and stabilizer in many standard products (more). However, the commercial capacity of this particular polysaccharide wasn’t what brought Dr. Novaczek and team to the small lagoon where they’ve been working for years.

The Irish Moss in this lagoon, called giant Irish moss, is unique in the world. Found only in this Basin Head lagoon, this is one of the reasons the Basin Head watershed has been designated as a Marine Protected Area (more). The giant Irish moss is haploid as opposed to diploid, meaning it has only one set of chromosomes as opposed to two. It does not reproduce sexually but instead makes clones of itself. Typically, Irish moss found elsewhere attaches itself to the ground and remains stationary by using attachment organs produced during reproduction. Since the giant Irish moss does not undergo sexual reproduction, it has no way to anchor itself. So how does it stay in this tidally-influenced inlet? The natural solution to that question has informed the conservation efforts of Dr. Novaczek and her team.

Giant Irish moss (Chondrus crispus). (Photo: BJGS).

In the 1960s, there were thick mussel beds in the lagoon, interspersed with eel grass. Mussels use thin fibers, known as byssal threads, to attach to rocks or other substrates. These particular mussels also attached byssal threads to free-floating giant Irish moss, and held large amounts of it in the lagoon. The intricately connected ecosystem resulted in an abundance of the giant Irish moss. In 1966, the giant Irish moss growing in the lagoon grew throughout an area of 1 km long, 50 m wide, and 40 cm deep.

Then, things changed. Most importantly, there were two waves of introductions of green crab (Carcinus maenas) from Europe, first in the late 1990s and second in the last few years. This invasive species is a voracious consumer of shellfish. The mussel beds were decimated and therefore no longer able to hold the giant Irish moss in place. The eel grass beds were also lost.

I asked Dr. Novaczek if the green crab was the only reason the giant Irish moss form was almost lost. Unsurprisingly, as we often see in ecology, it is never one thing. She explained that there are many agricultural activities in the area (yumm… PEI potatoes), and as delicious as these crops may be, when intensive, agriculture can result in sediment and nutrient loading into the lagoon. High nutrient levels can produce low oxygen conditions and overgrowth of other species. Of course, factors like climate change can also be a challenge for the growth of the giant Irish moss.

Potatoes being farmed near the study site. (Photo BJGS)

Paddling a canoe out into the lagoon, I went with Dr. Novaczek to get a closer look at their efforts to support the regrowth of giant Irish moss. We pulled up a few mesh bags of seaweed and shells and brought them back to the shore. Cameron Walsh, a student with Fisheries and Oceans Canada, explained to us how they have been filling mesh bags with mussels. These mussels are grown with giant Irish moss and transplanted into the lagoon to encourage new growth. While Cameron was showing us their methods, Jake MacKinnon, another member of the giant Irish moss team from the Souris Wildlife Federation, tracked down some of the invasive green crab in the lagoon to show us one of the crab culprits in the take-down of the giant Irish moss.

Cameron Walsh displaying a bag of mussels grown with giant Irish moss that are helping this unique population regrow (photo: BJGS).

So why is this story important? Dr. Novaczek explained that giant Irish moss produces higher quantities of carrageenan than the typical form, but the main reason she brought us here was to show the complex interaction network that was disrupted by a mix of disturbances. She also discussed the potential for including the giant Irish moss in with other harvested crops, which are grown together to benefit all of the crops and the local environment (also known as Integrated Multi-Trophic Aquaculture or IMTA). Many interesting prospects exist for the future, but for now, it would be great to see this unique form of the Irish moss returned to the Basin Head lagoon.

We took samples of both the giant and normal forms of Irish moss to add to our botany project sample set on the ship. My colleagues, Drs. Paula Piilonen and Mike Wong then inventoried and prepared these to be sent to the National Herbarium at the Canadian Museum of Nature.

I will be cheering on the efforts of Dr. Novaczek and team as they continue to try to re-establish this unique haploid, giant form of Irish Moss.

Byssal threads of mussels creating an anchor for the Giant Irish Moss, with its inability to produce its own anchoring (photo: BJGS)
Off the canoe and learning all of the details about the giant Irish moss conservation efforts, as well as (importantly) some all-natural mosquito repellent. (Photo: Jo-Ann Wilkins of CanadaC3 Photography team)

Disclaimer: I was on the Canada C3 expedition as a scientist to help with the many projects aboard for Leg 3. This blog features unofficial accounts of some of my experiences along the route. I am very grateful to having been included in this group, and I encourage everyone to check out the Canada C3 Expedition at Thanks to Dr. Irene Novaczek and team for showing us around!

Additional Links:

CBC story on the Giant Irish Moss of PEI (Sept 30 2015)