Patrick has two sites permitted for shellfish cultivation. One is just off the shore of a small island, where the water is 15 feet/4.5 meters at high tide. We’ll call this the Island site. The second site is off a sandy dike, in shallower water, roughly 5 feet/1.5 meters at high tide. We’ll call this the Beach site.
Knowing that scientists at Stony Brook University had successfully grown sugar kelp in shallow water – with that kelp growing up to 12ft/3.6m in length! – we’re pumped to see if our outcomes are remotely similar (acknowledging that the waters of Cape Cod are not the same as Long Island Sound, and that kelp growth is influenced by a wide range of factors). We're also looking forward to seeing how growth at the two sites, with differing depths, compares.
The Island Site: The orange dots and green line indicate the proposed growline location.
The Island Site: The orange dots and green line indicate the proposed growline location.
We won’t be growing any kelp if we can’t acquire kelp seed. The first supplier I checked with was Greenwave, only to find that all of their seed spools for the upcoming season were spoken for (I consider this a good problem, indicating high interest in the budding seaweed biz). Greenwave informed me that I could: 1) Get on a waiting list, or 2) Reach out to Woods Hole Oceanographic Institution (WHOI), and see if they had seed spools to spare. Conveniently, WHOI is a mere 20 miles from our prospective kelp sites.
Apparently the cosmos wishes for our project to succeed and for seaweed to envelop the earth – or maybe the folks at WHOI are just cool and considerate – because my inquiry was soon answered with confirmation that WHOI would be happy to supply the seed. A single seed spool from WHOI would be enough for roughly 200ft of growline. Patrick and I decided that we’d split a single spool over two growlines, 100ft at each site. This is a far cry from commercial scale but suitable for our experiment.
Populating the application involved a mix of research methods: ground truthing, seeking advice from other MA-based kelp farmers, and leveraging Greenwave’s training courses and farm design tool. The latter was invaluable for configuring the array for the Island Site – an array being the entire kelp cultivation system: the growline, anchors, hardware, buoys, etc.
Island Site Array
Using Greenwave’s design tool, I entered the info we knew – including site/environmental conditions (ie. depth, current speed, bottom type) and array expectations (ie. length, estimated yield, growline depth). The tool then ran calculations and provided answers to what we didn’t know – including anchor weight (based on the calculated drag), anchor distance (based on the site depth, growline depth, and appropriate scope for the anchor/bottom type), aggregate footage of rope needed, and more.
The design tool is in a beta stage. Consequently, it didn’t offer a function to calculate every single aspect of our proposed array. Ie. Our growlines would be 100ft, and the tool’s minimum growline option was 200ft (based on the fact that most seed spools come in ~200ft lengths). Nonetheless, the design tool provided an exceptional baseline from which I could re-calculate figures corresponding to our goals.
The array design for the Island site, created with input from Greenwave and local mooring experts. A detailed materials list will be provided in a later post.
Note on arrays: There are different types of growline arrays, with the simplest being the single-line array (the type we plan to deploy). A farmers array choice will be dictated on their goals and needs. Ie. budget, desired yield, and site size. More advanced arrays include: