As explained in The Sites / The Seed / Arrays, the apparatus we're using to grow our kelp are simple: rope, anchors, buoys, and a handful of hardware. It was time to put these pups together, and I opted to find as much used gear as possible; not only to save some money but because the aforementioned ingredients litter sheds everywhere near the ocean.

Anchors: A friend offered me an unbeatable deal of $0 for two mushroom anchors, with the condition that I repair them. The metal eyelets that connect the anchors to their chains had worn thin enough to require reinforcement; a relatively quick fix with a welding machine on hand. These will be used for the Island site. The beach site will use two, helical screw anchors (3/4”x48”), which were purchased new for $25/each.

Left: Mushroom anchors, one 250lb and one 300lb. Right: Reinforcing the anchor eyelets. Yay for welding.

Note on anchors: The optimal anchor type and weight is based on the characteristics of the seafloor (ie. sandy vs rocky vs something else) and the required holding strength. The seabed at the Island site is soft, so a mushroom anchor should settle in and hold well. The anchor weight was determined with the help of Greenwave’s farm design tool, which accounted for the array/rope length, water current speed, and drag to calculate a recommendation.

Rope: I bought the rope new, but I bet I could have found it used if I looked harder. I've read that used rope, with a somewhat fuzzy texture, might provide a better growing surface for the juvenile kelp.

For the growline and buoy lines, I'll use 1/2" Esterpro sinking rope. All rope used for this project needs to be free of lead (lead is sometimes used in sinking lines 👎) as well as anti-fouling treatment that may deter kelp growth. Sold by the pound, 300ft (I purchased extra, just in case) cost $65.00.

For the anchor lines I’ll use 3/4” 3-strand polydac (comprised of polyester over a polypropylene core). 80ft cost $48.

Note on line density: A rope’s density determines whether it floats, sinks, or is neutrally buoyant in the water column. Different materials have different densities. Nylon, polyester, and natural fiber ropes are usually sinking lines. Polypropylene ropes are floating lines. Neutrally buoyant lines are a blend between polyester and polypropylene.

Selecting the appropriate line density for a given application is key. For the seaweed arrays, sinking line will be used to keep the rope from floating to the surface and getting tangled in boat props – or anything else moving around on the water (ie. ducks).

Chain: Galvanized chain will be used between the anchor and anchor rope to provide extra durability. The common recommendation is that the chain portion makes up 10% of the total distance of your anchor rode; that is, the distance from the anchor to the growline. I’ll be using previously used, free (but totes sturdy) chain.

Old buoys, new buoys, and a whole lotta rope.

Buoys: My nautical uncle donated three rubber buoys (the orangey-pinkish orbs in the picture above) which will be used to suspend the growline. They're a bit grimey but fit the bill + float. I purchased two additional buoys, like these but green, for $20. These two will mark the anchors at either end of the array.

Hardware:

1,100lb Breakaway Links (x4): These were purchased new, totaling $16.

Left: Link Breakaway. Right: Swivel Breakaway

In MA, connections between vertical and horizontal ropes used in marine projects like ours – as well as lobstering operations – must include breakaway links, also referred to as weak links. Breakaway links are designed to break/release when a specific amount of force is applied. They're used to reduce the severity of whale entanglements in fishing gear; the breaking points allow ropes to separate from their anchors and other rigging, hopefully letting the entangled whale to move freely.

Galvanized Clevises/Shackles (4 x 1/2”, 2 x 6”): These metal fastening devices will be used at a number of points, connecting anchors to chains and anchor-lines. A couple were found in in the garage, leftover from other projects. The rest were purchased new for ~$35.

Total Materials Cost: ~$234

Not much, but this figure would have been approximately $1,200 more had all items been purchased new, with the mushroom anchors being the most expensive line item at ~$500/each.

It is important to clarify that we are attempting to grow kelp at a very small scale – two relatively short growlines with relatively light anchors, on a couple acres for exploratory and educational purposes; not commercial operation. Commercial sugar kelp farms usually deploy many more lines per acre, and some are operating on hundreds of acres. If we were scaling or aiming to maximize yield per acre, our design and startup costs would be significantly different. For example, we’d likely use multi-line arrays (like those noted in The Sites / The Seed / Arrays).

How much would it cost to set up your seaweed farm? The answer depends on many factors, from the scale to the location. Greenwave’s Farm Design tool takes these factors into account, and is a great resource for determining a budget as well as dimensions, equipment, and more. You can access it at: https://www.greenwave.org/ocean-farming-hub

Alternately, you could sketch out your proposed array(s) and get a ballpark figure by Googling the various components (rope, anchors, buoys, etc.) and populating a spreadsheet with their costs. If you’re in the United States, permitting fees may be found via your state’s regulatory agency for aquaculture, likely listed in Sea Grant’s State Of The States document. Furthermore, you can learn a ton by talking with folks who work on/in/around the water, such as mooring installers, fisherman, and marine equipment suppliers. You may even come across deals on gear and helping hands. You’ll certainly get more people thinking about seaweed.