discussion / Sensors  / 26 April 2022

Nutrient sensors - affordable, user-friendly, effective - do they exist?


Hi all, at the Kelp Forest Foundation we are researching the ecosystem services of cultivated giant kelp in and around Kelp Blue's offshore farm in Namibia. We are creating baseline studies of biodiversity (fauna and flora) and geochemistry to be able to assess the impact of kelp forests once they have grown (they will be seeded in the next few months) . One of the most important things for us to measure is nutrient uptake of the kelp farm - to produce data for a kelp carbon model, to assess competition with phytoplankton as well as the filtering potential of the cultivated kelp.

I am finding it difficult to find the right sensors which are commercially available, affordable, user-friendly and don't need constant recalibration in a marine environment. I have been told the microfuid based sensors for continuous monitoring of nutrients could be the best. I would welcome any leads, ideas or help on this subject.

Samantha Deane

Managing Director, Kelp Forest Foundation, The Netherlands

[email protected]

Hi Samantha,

This looks like a really interesting and beneficial project. Wishing you all the best with it.

Are you scouting for sensors that are archival and deployed / recovered over set period of time, or do you need telemetry / daily / hourly data to monitor change from tethered buoys etc? We are working on a similar solution with another partner, although not with microfuid-based sensors, but there are similar barriers regarding cost reduction and data collection.

Kind regards,


It sounds like you're looking for multiparameter probes to deploy in the water to log in situ readings as part of the baseline you want to establish, and you might be deploying BRUVs, doing video transects, or taking soundscapes in addition, if I'm not too far off the mark.

The multiparameter probes will run you around USD10k each, kitted for let's say pH, conductivity, DO, turbidity, nitrate, and temperature.  If you can rent these probes and the manpower to run them, that may be the best option if local expertise is lacking, as there are subtle gotchas.   You might want to look into an automatic winched system which raises and lowers the probe, so you get readings throughout the whole water column.  This may not be much more expensive than having 3 probes (at surface, bottom, and mid-depth).  Other advantages include reduced biofouling (since the probe parks in air) and potentially reduced maintenance load due to this.  But the disadvantages include fishers tying up to the system and boats colliding with it, and birds pooping on it, all of which have happened to me.