Courses / Monitoring & Maintenance

Course Content

Cadence of Monitoring
Create a Rhythm Be Storm Aware
Common Gear Issues
Slack in Your Growlines Anchor Drag
Change in Line Depth Loose or Broken Seed string Floating Debris Line Chafing and Fouling Sea Ice
Monitoring Kelp Biomass and Quality
Growth Rate Water Quality Biofouling
Resources & Tools
Farm Operations Forum
Kelp Growth Rate Measurement Protocols
Download file
Harvest Tracking Farm Map
Download file
Guide to Common Biofouling Organisms for Ocean Farmers
Download file
Lesson 2 Common Gear Issues

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Change in Line Depth

Over the course of the growing season, you might also notice that the depth of your growlines will change. As your kelp grows, the increase in biomass can cause your lines to sag. If your kelp drops too deep in the water column, it could fall below the optimal photic zone and grow at a suboptimal rate. Making sure that your kelp is 4-8 feet below the surface is something you want to constantly be monitoring. You’ll want your lines to be below the depth where they could be caught by a passing outboard or disturbed by the chop of the waves, but close enough to the surface to capture the maximum amount of light. Another risk of your growline dropping too low in the water column, it’s that it’s also more likely to become fouled by organisms that live near the bottom.

A drop in line depth can pull kelp below the optimal photic zone.

Over the course of the season, you can adjust your line depth by either adding or removing flotation along your growline. You can do this by swapping out smaller or larger growline buoys and adjusting the length of the buoy lines. Some farmers choose to only use corks or very small marker buoys for mid-growline buoys throughout the early part of the season and then swap them out with more substantial buoys when the kelp starts to grow quickly in the spring. If you’re using 5-line arrays, this can often be a good choice for mid-line spreaders. Your choice might depend on how much wind and foul weather you see on your farm. Bad weather can cause buoy lines to tangle with your growlines and strip off kelp.

On a 5-line array, it’s possible to install the mid-spreader buoys later in the season once the kelp starts to grow. This can reduce the risk that the mid-spreader buoy might cause the array to flip.
Industry Tip

If you’re growing bull kelp you may experience the opposite flotation problems of sugar and ribbon kelp. The pneumatocysts (the bulb-like structures at the end of the stipe) are naturally filled with carbon monoxide gas. As the kelp grows, it will want to float toward the surface. To keep the kelp growing optimally and reduce the risk of it getting tangled or damaged at the surface, you may need to add weights along the run of the growline. Some farmers clip on milk jugs full of concrete as the kelp grows. Remember to stay away from leaded line or weights that contain heavy metals the kelp could absorb.