The ECOHARVEST project

Photo credits: Pereira et al., 2020.

ascophyllum nodosum: the main character of the story

The algae Ascophyllum nodosum (L.) Le Jolis is a large brown alga widely distributed in the North Atlantic intertidal zone, from the Arctic circle to 42º north. . It has been harvested in many countries due to its important commercial interest (Pereira et al., 2020). Along the Irish coast, it has been harvested in a sustainable way for centuries with an increasing demand since most of the harvested biomass it has been used over the years to supply the European alginate industry (Hession et al., 1998). The Irish Government acquired shares from the Irish company “Arramara Teoranta”, the main purchaser of seaweed from local harvesters that kindly embraced this partnership (Arramara, 2021). As a result, new harvesting techniques beyond the traditional one were introduced and with them the need of impact assessment studies. Several studies around Europe were published, comparing the impact of these techniques on A.nodosum morphology, population structure or biomass (see Ang et al., 1993 and Ugarte et al., 2006). Nevertheless, there was no study comparing the impact of both the different techniques on the whole community and along the trophic web.

¿DID YOU KNOW?

These are some of the products derived from seaweed and widely used

The aim of the project

The aim of this project is to evaluate the impacts of two different harvesting techniques (using rakes from boats vs. sickles on foot) on A.nodosum biomass as well as its effect on the ecosystem biodiversity and community composition.

Photo credits: Uist Asco. www.uistasco.com

Hand harvesting using sickles on foot

With this technique, the seaweed is harvested at low tide by foot.

Photo credits: Arramara Teoronta.

Boat harvesting using rakes

The harvester operates with manually with a rake system from the boat at high tide.

¿who's involved in the project?

Photo credits: https://nl.linkedin.com/in/charlene-linderhof

Charlène Linderhof

National University of Ireland, Galway (NUIG)

Se is thePhD student carrying out the investigation.

Photo credits: https://www.arramara.ie

Arramara Teoronta

It is the company founding part of the project and the main seaweed purchaser for Irish local harvesters.

Photo credits: https://twitter.com/drjosemfarinas

Dr.José Maria Fariñas-Franco

Galway-Mayo Institute of Technology (GMIT)

He is one of Charlène's supervisor and also my Professional Practice supervisor.

Let's go do some work!

The sampling sites

Photo credits: Charlène Linderhof.

The Roundstone sampling site at high tide. Photo credits: picture taken by me.

The Kinvara sampling site at low tide. Photo credits: picture taken by me.

Two sheltered intertidal shore sites were selected for this study in Galway Bay: the lower red dot corresponding to the Kinvara site ( Co.Galway) and the upper one to the Roundstone site (Connemara, Co.Galway). As shown in the pictures, the Roundstone site was closer to the shore line.

The experimental design: a stratified sampling method

At both sampling sites three plots 25x25m plots were marked, one representing the ambient conditions or control and the other two for the corresponding treatment levels. Within the plots, a sampling station for each sediment type (H= hard substrate, S= soft substrate) was settle, indicating the area where the three 50x50cm quadrats of seaweed were cutted off. Also, the first 5cm centimeters layer of sediment from the soft sediment samples was collected and sieved thorugh a 500 micra sieve.

The same protocol was followed on three ocasions (three sampling trips) to monitor the study systems:

Baseline: conducted in July 2020 in KInvara and October 2020 for Roundstone.
Post-experimental harvesting: right after the baseline surveys.
Six months post-experimental harvesting: May 2021 for both sites.

Photo credits: Charlène Linderhof.

In order to characterize the potential changes in fish and invertebrate communities, three shrimp pots or fish traps were deployed within each treatment quadrat for the three sampling trips. Each pot containing 5 crushed mussels as bait and a LED light to attract organisms. The pots were left for 12 hours at high tide and 12 hours at low tide. Afterwards, the organisms found were stored for stable isotop analysis.

References

Ang, P. O., Sharp, G. J., & Semple, R. E. (1993). Changes in the population structure of Ascophyllum nodosum (L.) Le Jolis due to mechanical harvesting. Hydrobiologia, 260(1), 321-326.

Arramara Teoranta. (2021) Our story. https://www.arramara.ie/our-story/

Hession, C., Guiry, M. D., McGarvey, S., & Joyce, D. (1998). Mapping and assessment of the seaweed resources (Ascophyllum nodosum, Laminaria spp.) off the west coast of Ireland.

Pereira, L., Morrison, L., Shukla, P. S., & Critchley, A. T. (2020). A concise review of the brown macroalga Ascophyllum nodosum (Linnaeus) le Jolis. Journal of Applied Phycology, 1-24.

Ugarte, R. A., Sharp, G., & Moore, B. (2006). Changes in the brown seaweed Ascophyllum nodosum (L.) Le Jol. Plant morphology and biomass produced by cutter rake harvests in southern New Brunswick, Canada. In Eighteenth International Seaweed Symposium (pp. 125-133). Springer, Dordrecht.

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