A vibrant green is etched in my mind, from the countless hours spent snorkelling in Orkney’s seagrass meadows, this summer. Snorkelling through a subtidal seagrass meadow, is in my opinion how seagrass should be experienced. Gliding atop the canopy spying down on the daily rituals of the inhabitants as they forage and seek refuge amongst the towering seagrass blades, is captivating. Aside from the profusion of life living within the meadow, the meadow itself is a spectacular thing to observe. Seagrass meadows have the ability to put on some of the best light displays across the natural world. The interaction of the sun and waves create a mesmerising spectacle; the reaction of the blades to passing waves produces a brilliance of green that shimmers across the meadow. Few people get to experience these sights, a privilege I have been granted by being part of this incredible restoration project.
Figure 1. Seagrass meadows in Orkney (photo credit: Raymond Besant)
Team members from Restoration Forth and I, were back in Orkney for our second year of seed harvesting and community engagement. We were in Orkney as it is host to some of the best examples of intact and healthy seagrass meadows in the UK, alongside Orcadian seagrass belonging to the same genetic profile of that found in the Firth of Forth. Orkney’s unique geography and phenomenal water conditions make it a nexus for seagrass, the muddy firths, bays, and coves found across the archipelago provide the sheltered conditions and suitable substrate conducive for seagrass colonisation.
Figure 2. Seagrass team (photo credit: Raymond Besant)
We were to be in Orkney for just over three weeks this time round, to maximise the potential to collect viable seeds for our restoration efforts back in the Forth. A lesson learnt from the previous year, where we missed the height of seed availability due to less time spent on Orkney and unseasonably warm weather. Seagrass meadows have a short window for when seeds are made available, the timing of this window changes ever so slightly year on year as a result of the interannual variability of climactic conditions. Too hot and the seed production is sped up making seeds available earlier than expected, too cold and the seed production is delayed resulting in seeds becoming available later in the summer. The window is typically two to three weeks during the summer months of July and August, but this can change depending on the latitude of the seagrass meadow. By staying for three weeks, we increased our chance of coinciding with the height of seed production in Orkney’s meadows. Our prayers were answered as we arrived in full swing, the meadows were brimming with seeds. Our elation was hard to match.
Figure 3. A snap shot of the biodiversity we saw in the meadows (left: sea hare, right: juvenile flat fish)
Seed harvesting is a committed and careful practice. Harvesting is governed by the activities of the tide, which translated to early rises and late nights when spring tides were in play. The earliest pick we did this year was at 5am, thankfully being so far north the sun rises before four in the morning, which made getting up at that time of day a little less difficult. Harvesting was performed during low tide to ensure minimal damage was inflicted on the meadow, as individual reproductive shoots needed to be snapped carefully at their base. A practice which does not affect the health of the plant. We restricted our activities to tide heights no greater than 1.15m to limit deeper duck dives in order to reach the sought-after shoots.
Figure 4. Seed harvesting (photo credit: Raymond Besant)
Our mesh bags would steadily fill up over the course of an hour as we purposefully navigated between harvestable reproductive shoots, plucking as we went. At the end of each snorkel session, we would come together and combine our efforts by storing the shoot filled mesh bags in large scallop bags, that we had attached to fixed ropes in the water. The decision was made this year to store the shoots in-situ to remove the pressure of replicating the natural marine conditions in a land-based storage unit. Its safe to say this worked wonderfully, definitely on the cards for next year! This year we were fortunate to be able to invite local Orcadians to participate in our harvesting events. Each day we advertised a few spaces out to the local community, so they could come join us and learn how to responsibly harvest seed baring shoots. It was great to see the aptitude of the community to participate in these seed picks and how elated they were after having spent time in a seagrass meadow (despite cold-water temperatures).
Figure 5. Seagrass filled scallop bags (photo credit: Raymond Besant)
In tandem with seed collection, we were able to produce spatial maps of the donor meadows we were collecting from. My colleague, Esther (Project Seagrass), was able to programme Project’s Seagrass’s state of the art drone to pilot a course over the area where the meadows were positioned. This exercise returned two illuminating maps illustrating the shear size of these habitats. The larger of the two meadows occupies an area of ~50 hectares, which has the capacity to hold over 200 million seeds. While the smaller of the two donor meadows covered an area just over 2 hectares, with a seed capacity of around 8 million seeds. We anticipate that this year’s harvest has returned around 200,00 seeds for our restoration project but stay tuned for the final figure. The possibility of over picking seed baring shoots in these meadows is near impossible. Seagrasses are known as R-selected species, which are animals or plants that prioritise quantity over quality when producing offspring, a trade off that enables seagrass to produce copious amounts of seeds but at the expense of each seed not getting the adequate parental investment to ensure they reach adulthood. This results in a lot of seeds being lost to predation and competition from existing plants for nutrients, light, and space. Seagrasses typically favour asexual rhizomatous growth to produce new shoots over the establishment of new plants via sexual reproduction. Therefore, by collecting seeds from a meadow we should not threaten the existence of these meadows.
Figure 6. Aerial shots of the team in the water (left: seagrass team harvesting shoots & right: the team preparing to enter the water, the dark area is the seagrass meadow) (photo credit: Raymond Besant)
The seeds that we collected during this summer are now peacefully bubbling away in tanks housed at the Lobster Hatchery in North Berwick, awaiting their release date next spring. The team will soon commence seed sorting days for our community members from around the Forth. If you are interested in participating in the sorting of seagrass seeds that will eventually be sown in the Forth, then head over to the Restoration Forth webpage to see when the next event is taking place.
Since returning to the Forth, the team and I have returned to our restoration sites to monitor the success of our trials, that took place earlier this year. We are pleased to see the germinated shoots are holding on and finding their new home suitable. We have been able to record germination and shoot survival records of 10.3% in Drum Sands and 4.3% in Burntisland Sands, which are both positive results! Typical germination rates of seagrass seeds are around 10% so we are hitting and nearing that value across the three sites. The stats have proven difficult to determine for our site in Tyninghame, due to the occurrence of naturally sporting seagrass there but the seagrass is looking happy and healthy. So that’s all we can ask for.
Thanks for reading!
Lyle