Hatchery Innovations: In Pursuit of Direct-Seeding
As fall rolls into winter, the kelp hatchery season is fully underway. Across the country, seed spools sit in tanks, growing darker and fuzzier each day as thousands of sporophytes attached to tight wraps of seedstring grow and develop. At northern latitudes some farmers have already outplanted seed onto their growlines, and many are gearing up to do so in the coming weeks. But this fall, kelp hatcheries in Southern New England have struggled to find mature sorus tissue. Many scientists point to unseasonably warm water temperatures causing a delay in the development of reproductive tissue. This delay has caused hatcheries to push back their inoculation schedule which means that seed won’t be outplanted onto nearby farms until mid-December this year.
For decades, kelp hatcheries have relied on the reproductive tissue from wild kelp beds to seed the next season’s crop grown on farms in the region. In the fall, small amounts of reproductive sorus tissue are collected from the wild, cleaned and processed in a hatchery setting, and “tricked” into releasing their meiospores into a small volume of seawater. Spools of tightly wound twine are then submerged in this spore-dense solution, where thousands of tiny meiospores swim in the dark for a number of hours before settling on seedstring. From there the spools are grown in a closed system of recirculated seawater for the next 6-8 weeks.
But this process relies on extracting fertile material from nearby wild kelp beds, and the timing for when spool production can begin, and ultimately kelp farming can take place, is dictated by the natural availability of wild sorus tissue. As the climate changes and environmental factors shift along our coasts, many have begun to wonder, will hatcheries and farms be able to continue to rely on this wild resource? This predicament has led scientist Dr. Charles Yarish, at the University of Connecticut (UCONN), and others like him, to ask if it’s possible to circumvent this reliance on the seasonal availability of wild kelp. His solution involves a method called gametophyte culturing that would allow for a type of application known as direct seeding. Using these methods, kelp farmers could have more control over the timing and availability of seed and even eliminate the need for seedstring entirely.
For the past several years with funding from the ARPA-e MARINER project, scientists at UCONN and Woods Hole Oceanographic Institute (WHOI) have been researching different techniques for direct seeding, running experiments to determine at which life stage, and using which application methods, directly seeded kelp is most successful. The researchers aim to develop a low-cost, easily replicable method that could be utilized at an industrial scale.
“The goal is to reduce the bottom line for the farmer,” said Dr. Yarish, who has been researching direct seeding methods since the 1980s. “Direct seeding will give us the ability to make the whole industry more profitable.”
Scientists from UConn and GreenWave record measurements of kelp grown in direct seeding trials.
Dr. Yarish sees this change happening in a number of ways. First, direct seeding will allow hatcheries to practice a form of selective breeding. The technology would give farmers the ability to identify traits in adult kelp that they find desirable — such as wide blades, short stipes, or a particular flavor — and essentially recreate those characteristics season after season by outplanting the same seed. “It would allow farmers to develop different cultivars,” said Dave Bailey, a scientist at WHOI and partner in this research. “There are inherent morphological differences between wild beds, making it hard to produce the same quality kelp grown at the same site year in and year out.” But direct seeding would allow farmers to reduce this variability and create a more reliably high-quality product, which would help in marketing their kelp to processors. Instead of harvesting sorus tissue from a wild bed and hoping for good results, “It’d be more like ordering vegetable seeds,” said Bailey.
The lifecycle of sugar kelp is complex. To reproduce, it goes through several different life stages. The reproductive sorus tissue of the fertile adult blade releases thousands of microscopic meiospores, which briefly swim through the water column before settling and developing into male and female gametophytes. The gametophytes then mate, and that’s when a juvenile sporophyte — the microscopic version of the adult organism that will one-day grow to upwards of 15 feet long — is born. Traditional kelp hatchery methods have let this whole lifecycle, from the meiospore phase on, play out on the seedspools themselves. But direct seeding targets the kelp at the gametophyte stage and holds it in a vegetative state. Once a cluster of gametophytes has developed, scientists grind them up to create thousands of small clones. By maintaining these cultures of male or female gametophytes and then breeding them with different strains, scientists are able to make selective crosses.
To transfer the gametophytes or juvenile sporophytes to growout lines on the farm, the team has tried different methods of application including both painting the seed solution onto lines with a brush, and spraying the lines with an industrial paint sprayer. They’ve also tested whether or not the kelp needs a binder, such as sodium alginate, to properly adhere. Yaoguang Li, a researcher in Dr. Yarish’s lab, explained that recent trials suggest that spraying gametophytes seems to be the most effective method at getting them to stick. And the force of the sprayer eliminated the need for a binder — the gametophytes appeared to adhere fine on their own.
Although both Dr. Yarish and Bailey acknowledge that the science is still a few years out from becoming a widespread commercial reality, the early results are promising. Bailey imagines in the not-so-distant future, farmers could receive a bucket of gametophyte solution and spray it directly onto their growlines as they outplant onto the farm. This type of technology could allow for bigger farms and farms in more remote areas since it eliminates the concerns of transporting seed spools long distances. It’s possible that farm design might also shift to accommodate the new technology. Right now many farmers use approximately 200-foot growlines since that’s the length of seedstring most hatcheries can fit on a 2” PVC spool. But by eliminating the seedstring, farmers may find there’s a more optimal growline length or configuration.
To make this work, hatcheries would also have to make a shift. Instead of housing racks of aquariums filled with seedspools, a kelp hatchery using this technique might look more similar to phytoplankton lab, such as those often found in shellfish hatcheries growing microalgae to feed broodstock. It would involve new equipment, training, and a shift in the current seasonal cycle. Instead of being active in just the fall — kelp hatcheries might keep cultures all year round. But it could also make for much cheaper and more efficient production. “One hatchery could serve 100 farms,” said Bailey.
Seeding from gametophyte cultures would also give farmers more control on the timing of when they plant their crops. Since they’d no longer be reliant on the development of sorus tissue in the wild, delays like farmers are experiencing in Southern New England this fall could be avoided entirely. It would also reduce pressure on wild kelp beds and eliminate the expensive costs associated with dive collection.
This type of transition takes time, and won’t happen overnight. “Direct seeding has been promised as the Holy Grail for years, but it hasn’t materialized as a viable technology for farmers yet,” said GreenWave’s Bren Smith. “The industry desperately needs it to work.” But Dr. Yarish believes the transition is just around the corner. Directly seeded lines are being tested on farms in Kodiak, Alaska this fall through a partnership with Blue Evolution, which he says is a major step forward. “We’ll be ready for prime time very soon.”
Special thanks to: Charlie Yarish, Dave Bailey, Yaoguang Li, Crystal Ng, Scherry Umanzor, Simona Augyte, Michael Marty-Rivera, Scott Lindell, Lexa Meyer, the University of Connecticut, and the ARPA-e MARINER Cat-1 and Cat-5 projects.