Species Selection

The initial species chosen for cultivation by the Running Tide macroalgae program management team were:

• Ulva lactuca a common green algae

• Ulva fenestrata, a Northern Atlantic green algae closely related to U. lactuca

• Saccharina latissima, a brown algae commonly known as sugar kelp

These species were selected based on their availability, well-documented life cycles, native ranges, compatibility with cultivation systems, and scalability. Their selection was strategic, aiming to maximize efficiency and output while ensuring sustainability, though not without tradeoffs. Key criteria included:

• Native to our operating locations in the North Atlantic (Maine, Iceland, etc) to improve open ocean growth potential, and refrain from introducing non-native species. We expected to routinely research and identify species and populations for potential cultivation and deployment, as new hatchery locations and deployment permits in varying oceans would mean new species requirements (e.g., we wouldn’t want to deploy Icelandic sourced North Atlantic sugar kelp in the Pacific Ocean).

• Relatively well known life cycle and physiological requirements, to enable fast and efficient set up of cultivation processes.

• Different length of life cycles, enabling a faster start with Ulva (a total of 3-4 months to reach maximum growth) versus a higher total yield with sugar kelp (6-9 months of growth possible after 3-6 months of hatchery cultivation). We wanted to be able to deploy substrate that floated for 2-3 months and still see macroalgae growth, which Ulva gave us, but the long term carbon fixation potential was thought to be in higher yield species like sugar kelp.

In Iceland, we started by conducting multiple sampling trips, searching for Ulva and reproductive sugar kelp material (sorus) at various locations to better represent the genetic variability in the sourced sites. We shipped samples to our genetics lab in St. Louis, MO, USA where we extracted DNA and RNA, and conducted phenotyping work.

This sourcing and genetics work resulted in a paper recently submitted to Ecology and Evolution by Áki Jarl Lárusson et al.: “Whole genome sequencing reveals interbay population structure of Saccharina latissima (sugar kelp) in southwest Iceland"

This work kickstarted research into macroalgae genetics and genomics for the benefit of our breeding program. Ultimately, we wanted to identify the best species and individuals within those species to grow in the open ocean and improve them via selective breeding for a low nutrient, high energy environment. In hindsight, our eagerness to optimize genetic stock before refining the broader system of deploying substrate or even verifying open ocean macroalgae growth was an inefficient and ineffectual order of action.