Using Photovoltaic Panel to Positively Charge Bidum Surface for Mussel Spat Attachment

I work in reseeding mussels to denuded rocky intertidal zones along the Africa East Coast.
I've developed a mussel spat nursery and spat collector. (image attached).
The cut out tyre wall is covered with nylon and polypropylene, (drainage bidum).
The process involves bolting the nursery over hand selected juvenile mussels. They attach to the rock to form a clutch, protected from the pounding surf. The apparatus is moved, the process duplicated.
The bidum/nylon shroud acts as a substrate for collect floating mussel spat... The scientific theory being that they seek out adult colonies by association.

Now, my question:
Untested research indicates that spat have an affinity to attach to a positively charged surface.
Is it possible to attach a small photovoltaic panel to the tyre wall, and using daylight current generated, it it possible to create a positive charge across the bidum surface ?

I'm willing to research various wiring options, and publish findings on the forum.

This could be an interesting project in science for conservation, and would certainly help me in my work.

Bruce Goodwin
Shell Reef Projects NGO
South Africa

Very simply, yes, its very easy. Set up your solar panel facing the sun, (pointing south in the northern hemisphere), and attach the two bare ends of the wires to your chosen rock or surface, perhaps a foot apart. Seawater, being salty, is conductive, so a current will flow through the water, or across any wetted surface. Alternatively, you could attach one contact to a surface and place the other in the sea about a foot away. Experiment with different polarities and distances between the contacts.

You can observe whether the mussles prefer to settle near to either the negative or positive contact, or even whether they avoid the path of the current. (I personally suspect that most creatures prefer to avoid electric shocks.)

By adding a voltage regulator to the circuit, you could limit the voltage applied to the test area. By adding a battery, which is charged during the day by the solar panel, you could maintain the voltage at night.

The solar cell itself would need to be very well waterproofed and protected from mechanical damage, and the wires well sealed around their exit from the panel.

It would be fascinating to hear of your results.

A thought occurs to me: what would be the effect on electric eels ?

The simplest arrangment I can suggest for powering the contacts would be to open up common garden solar LED lights, and take your voltage supply from the battery through a resistor to the wires leading to the external contacts. But again, at sea and in surf, a more thorough waterproofing will be needed. I would guess that silicon filler, as used around baths or as a window sealant, would do the job.

Here is a simple concept circuit.
The diode D1 prevents the battery discharging through the solar cell at night.
The resistor R1 limits the current drawn from the battery.
Different resistances could be tried, perhaps between 1 kOhm (1 000 Ohms) and 50 kOhms (50 000 Ohms).

Avoid putting Silicone I [That's "Silicone roman numeral 1"] directly on wire (or metal) surfaces. It releases Ascetic Acid as it cures and will corrode the wires. Use Silicone II instead, which exudes ammonia and methanol, instead, which won't corrode the wires. BUT make sure it's a fresh batch! I made the mistake of using a tube of Silicone II that was a year past the "Use before" date and it never cured!

Also, because sea water is such a conductive medium, it seems like it will be difficult to generate a positive field over a large enough area. I would suggest a large conductive mesh made of a material that won't corrode (carbon or perhaps stainless steel or even conductive plastic [though I know nothing about the properties of conductive plastic -- i.e. toxicity, etc.])

Depending on how strong the field needs to be, I imagine a large current will be involved and thus the need for a fairly large PV array, but experimentation will tell, and of course try this on a smaller scale at first.

Also, I'm wondering what, in nature, produces positive fields that mussels are bound to encounter? Perhaps discover what this is and reproduce it. Perhaps a steady (or relatively steady) stream of salt water, which is very conductive, passing through a magnetic field (such as produced by a deposit of magnetite), or even a stream of sea water flowing past a rocky surface in just the right orientation to the Earth's magnetic field to produce such a charge across the face of the rock.

Though, maybe the concentration of salt needs to modulate for this to work, such as might be the case in an estuary.

Also consider the possibility that the "positive field" might be a _red herring_. That they might not be attracted to just any old positive field, but are actually attracted to some chemical process going on between the salt water and some mineral deposit that just happens to also generate a positive field, for instance. Or there's some other, perhaps microscopic, life form involved -- some sort of symbiosis, etc.

Thanks for that warning about the silicone, Steve. I'm about to use some to seal my car windscreen.

From Wiktionary:
Ascetic: Of or relating to ascetics; characterized by rigorous self-denial or self-discipline; austere; abstinent; involving a withholding of physical pleasure.

Difficult stuff to work with, that ascetic acid !

I think it may actually be acetic acid which is the problem !-)

But back to the `current' subject:
I was thinking of a small current, milli or micro amps, flowing through the seawater, but might it be interesting to (very well) insulate the underwater contacts and apply a high voltage field ?

Steve, good thinking from basic principles on the conductive seawater moving in a magnetic field. If I could remember my basic principles, I would work out the magnitude of the voltage per metre in a ten knot south-easterly current in equatorial waters. (Any takers ?)

Birds are reckoned to use the earth's magnetic field for migratory navigation, so sea creatures might well have a few as-yet-unknown-to-man tricks up their sleeves.

You never know, we may be just starting Bruce on his own little voyage to world fame and a Nobel prize. (Just give us a mention from the podium, Bruce !-)

For the "electrode" consider using something like a Fluval brand carbon pad replacement filter available at PetSmart for about $4 (assuming you have a PetSmart in Africa -- if not, then try an aquarium or pet store -- assuming such things exist where you are).

Truly, one must assume an _ascetic_ deprivation of respiration as they engage in a _religious_ application of the stuff -- that, of course, was what I was referring to
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[@!#$$!@!!%$ spell checker!]

I mean, for the test case -- probably too small for real-world application.

Guys. You are dealing with the most electrically challenged person on the planet. I'm busy taking all of this in. Believe me If I should wire up any device, take immediate shelter. A black hole cometh.
Your comments on magnetic fields, tides, bird migration and the like are all part of the mystery of why these wonderful creatures do what they do.
I shall try Frank's suggested solar garden light. However as I go along I shall post pictures and data related to spat fall.
A pilot project is intended in S Mozambique April- May. The first step being all the community interface, state permissions et al.
I'd like to begin with a simple rig, and trust in your advice and guidance as things go along. It may take some time, trial and error, but on the strength of your expertise I feel confident that a successful prototype may not be too far away.
Thanks for the mind share.

Here's a little pic of which way round diodes go. The resistors are not fussy.

If you manage to find a way to have an opening watertight door in the casing, a variable resistor could be used, checking its value with a small multimeter, which in this century are very cheap.

The solar cell provides current to charge the battery in daylight.

Diodes allow electrical current to flow in only one direction, so in the above diagram, the solar cell can charge the battery, but won't discharge it at night.

As long as the battery retains a moderate charge, it will supply a reasonably constant voltage.

(Relatively, the conductivity of the seawater is fairly high, so the value of the resistor will mainly determine the strength of the electrical current.)

A typical suitable diode could be a 1N400x, where x is any digit from 1 to 7, so any diode marked from 1N4001 to 1N4007 will work. (These are very common.)

(The higher numbers are just higher voltage versions, but any will do for this very low voltage application.)