Farm Findings: Seaweed thrives in Wales' Powerful Seas

Wales has kilometres upon kilometres of unsheltered coastline. Enclosed on three sides by the chilly Atlantic, the unofficial peninsula faces its fair share of battering by storms and strong currents. But while the ocean might be annoyingly temperamental to the average holiday-maker, it serves as a perfect home for plant life that can tough out the waves, currents and changing tides. It may even be serving them a significant benefit

Just as cold air sinks and hot air rises, water does the same. Across the world’s oceans cold water rises from the seafloor, bringing minerals and nutrients from the depths to the surface in a phenomenon known as “upwelling.” When those crucial resources get to the surface, they are distributed outwards through “mixing” by currents, and are absorbed by plants to be used as they grow and spread.

The strong currents off the coasts of Wales speed up mixing and make more nutrients available, purportedly creating an ideal environment for both wild and cultivated seaweeds to thrive.

To quantify the supposed advantages of cultivating seaweeds in Wales’ ocean environment, we examined the length and biomass changes at Câr-y-Môr’s Porthlysgi site over the course of the growing season. With the samples sent to us, we measured blade length, and weighed the seaweed per meter of cultivation rope.

Left: Photo of sugar kelp in February 2022 (2 months after seeding). Centre: Photo of sugar kelp in May 2022 (5 months after seeding). Right: Seaweed samples laid out for measurement (in May 2022).  All photos taken at Porthlysgi seaweed farm.

What We Found?

Seaweed biomass increased rapidly between April and May before plateauing in June and July. The seaweed blade length however, increased most rapidly in March and April, peaking mid May before dropping off slightly in June (Figure 1). To put this into the context of Europe-wide cultivation productivity we plotted the peak biomass and blade length against previous studies in other locations to find that both metrics were highest at Porthlysgi (Figure 2).

Figure 1: Seaweed biomass and length data collected at one of the study sites throughout the cultivation season showing a plateauing in May to June of 2022.

Figure 2: Comparing maximum seaweed biomass and length data collected at 5 study sites growing sugar kelp. 

What Does This Mean?

While we collected environmental data at Porthlysgi using our GrowProbes and water samples, the farms we compared Câr-y-Môr’s yield to did not have similar data available. Thus we cannot say for sure which specific characteristics of Wales’ oceans are responsible for their greater yield. 

However, Câr-y-Môr was the most exposed of all the European farm sites we compared – opening directly onto the Atlantic ocean with very little shielding from landmass. Thus, based on prior studies, we suspect that these conditions are creating ideal conditions for the growth of seaweed. The continuous cycling of nutrients and mixing of deeper cool waters, may allow seaweeds in Wales to thrive and grow beyond expectations.

To explore this assumption, we would need to conduct a multi-year study at Câr-y-Môr, taking into account human-controlled factors such as the type of kelp seedlings used, the configuration of the farm ropes and buoys, and timing of the farm work. These factors are all known to have a very strong influence on crop production, and need to be further examined. To pinpoint the exact ocean conditions that lead to thriving seaweed, we would also need environmental data from the other European farms we compared to. 

We’re looking forward to this deeper exploration of our early results, but even now it’s exciting to see Câr-y-Môr’s resounding success in seaweed cultivation. It’s a result full of promise for Wales’ future – in the blue economy, sustainable development, and environmental protection. 

Reference

1. Kerrison, P.D., Stanley, M.S., Edwards, M.D., Black, K.D., Hughes, A.D., 2015. The cultivation of European kelp for bioenergy: Site and species selection. Biomass and Bioenergy 80, 229–242. https://doi.org/10.1016/j.biombioe.2015.04.035