16 ms·

Underwater power cables affects crabs biology at a cellular level

ohazi 5y ago
Wait, so you're telling me that lobster actually does stick to magnet? [0] https://www.albinoblacksheep.com/flash/lobster https://www.albinoblacksheep.com/flash/lobster
nonrandomstring 5y ago
I think there's a difference between them being "attracted" to the short range field, and being disoriented as they climb over the cable. Maybe it's the heat or inductive heating effect they like. EM shielding the cables would make them too heavy. Switching to DC transmission might fix it, but the cable loss would be higher and the cost of rectifying and remodulating to AC would be high. Two thoughts come to mind. More cables in parallel carrying less current, which gives the added advantage of redundancy. Short breaks in the flow, like a railway crossing for crabs, for 5 minutes or however it takes them to get unstuck and go along their crabby business.
- croisillon 5y ago
  crabby business <3
- jakear 5y ago
  Combine the two? Several smaller cables with a cycling subset powered at any given moment.
- 7952 5y ago
  More cables could disrupt the sea bed more during construction and cause more harm to plants and animals.
- xxs 5y ago
  >Switching to DC transmission might fix it, but the cable loss would be higher AC loses due to reactive impedance and skin effect should always be higher than DC transmission. DC might make sense if the generation is solar based, as it naturally generates DC, although converting it to higher voltages must have an AC step.
  - roomey 5y ago
    The highest capacity sub sea transmission cables are DC now I think. There is an interconnect between Ireland and France that is DC if memory serves. I think it's only efficient for the largest capacity lines tho
    - 7952 5y ago
      AC cables are just more expensive per km, I think due to skin effects.
      - Johnythree 5y ago
        That and the enormous capacitance between a long cable and the sea.
    - XorNot 5y ago
      DC is also used because you avoid grid synchronization issues, and this is generally the trend for long distance connects now in general. It means the grids can have frequency divergence without affecting the transmission line itself.
      - Lascaille 5y ago
        The issue with DC transmission in subsea cables is that the XLPE insulation can become polarized and - from what I remember - have water drawn into it due to the consistency of the field.
        spookthesunset 5y ago
        You could probably flip the current at periodic intervals to deal with this.
        Lascaille 5y ago
        You're talking about flipping the polarity, going occasionally from conductor-positive to conductor-negative (the shield must remain at ground potential.) If I remember correctly that actually makes things much worse if you've operated at one potential for a considerable amount of time. You could operate the cable at AC ~ 0.1Hz but your ability to actually transmit MWH would suck.
- lm28469 5y ago
  > More cables in parallel carrying less current, which gives the added advantage of redundancy. Every time we have a problem with tech the answer always is "just add more", idk how to feel about that
  - politelemon 5y ago
    Or more abstractions. Where the original problems that we were trying to get away from, resurface in new ways, and previously solved problems have to be reimplemented.
  - riskable 5y ago
    Adding more of something is often the simplest and cheapest way to fix problems. Example: Adding a few more VMs or containers costs almost nothing. Paying developers to eke out 10% more performance is expensive. Another example: Microcontrollers that have loads of pins (e.g. 100) and support many different peripherals (i.e. protocols like I2C) are expensive (say, $10-20). Little ones with a medium amount of pins (e.g. 56) and support for limitless protocols are cheap ($1). So if your PCB needs just a few more GPIO pins to accomplish something it makes more economic sense to just "add another" little MCU rather than "go big". Even if it makes programming the thing slightly more complicated.
- HPsquared 5y ago
  Maybe a barrier to prevent underwater critters from getting too close to the cable. Some kind of tubular fence?
- rand0mx1 5y ago
  You are claiming that DC losses are high, can you cite any source.
  - bluGill 5y ago
    Probably only historical ones. In the past it wasn't easy to get high voltages with DC, so losses where higher. These days we are better at changing voltages, and so DC losses the same as AC with similar voltages (skin effects still can be a small difference). I understand we can actually run DC at higher voltages than AC, though I'm not enough of an EE to explain why. IF this is true, then DC losses would be less than AC.
  - riskable 5y ago
    DC-to-AC losses used to be high (historically) because of inefficient inverter technology. These days we have 90-95% efficiency inverters (that are built to match their HVDC voltages). It's interesting because the reasons why we built everything using AC in the past don't really apply anymore (well, most of the time). DC is more efficient for most domestic and industrial electricity utilization. Things like lighting, air conditioning/heating, refrigerators, etc are all more efficient if fed from DC. Think about it: How many "wall warts" have we got in our homes these days? All our LED light bulbs have built-in inverters and that decreases their efficiency. Our PCs use DC for literally everything internally. The list goes on and on. I had also read a while back that grid-scale DC power transmission could be more resilient because the power transformers aren't as expensive. It's like $8 million for one of those giant high voltage AC transformers they have at power stations whereas with high voltage DC the equipment is cheaper but you have more of it (or something like that; I wish I could remember the details but this was an explanation given to me from a DC fanboy lineman over 10 years ago). The idea being: If bad weather breaks your giant $8 million AC transformer that's a real expensive pain in the ass but if it breaks a handful of small DC transformer components that's a quick (and cheap) fix.
    - pitaj 5y ago
      > LED light bulbs have built-in inverters Think you meant rectifiers here.
plufz 5y ago
Time to start making cute tinfoil hats for the crabs!
- amelius 5y ago
  Tinfoil does not block magnetism.
  - deleted 5y ago
    [deleted]
  - chiefalchemist 5y ago
    It's a cheeky reference to power grid cables on land having (negative) influence on the health of humans; and that being dismissed as "conspiracy theory." Regardless, at a more practical level, sea creatures can't wear hats, tinfoil or otherwise.
    - mschuster91 5y ago
      > It's a cheeky reference to power grid cables on land having (negative) influence on the health of humans; and that being dismissed as "conspiracy theory." The thing is, there is no scientifically validated evidence of that effect; also, there is no proof of humans being able to sense (electro-)magnetic fields.
      - kenniskrag 5y ago
        They can. If it is strong enough you can feel dizzy if you move the head. Heat and nerve stimulation is also possible according to https://en.m.wikipedia.org/wiki/Safety_of_magnetic_resonance_imaging https://en.m.wikipedia.org/wiki/Safety_of_magnetic_resonance...
      - nashashmi 5y ago
        At a sufficiently intense fields, humans can detect them. Besides, for science you need to provide evidence for an affect to prove it exists. For people you need to provide the “negative” of evidence to prove it doesn’t exist. People and science are not the same.
Gravityloss 5y ago
There are things like bottom trawling that basically swipes the whole sea floor. Plants and corals are destroyed. https://www.youtube.com/watch?v=NKG5sbnhvWg https://www.youtube.com/watch?v=NKG5sbnhvWg But it's not visible to the surface directly.
londons_explore 5y ago
Underwater power cables can be designed to have zero electrical and zero magnetic fields emitted from them. Typically that's done by using a grounding shield (which eliminates electrical fields), and by making sure currents in all directions are balanced (eliminating magnetic fields). As far as I'm aware, nearly all modern high capacity cables are built this way already. It's only old stuff (which tries to use the earth as a conductor) or low capacity stuff (which is sometimes AC and not well balanced) where this isn't true.
- londons_explore 5y ago
  > a grounding shield (which eliminates electrical fields), This makes all electrical fields zero... but in the ocean there may be other natural electrical fields that don't appreciate being zeroed out...
- nonrandomstring 5y ago
  Right. Not an electrical engineer, but isn't there something like a counter-twisted pair (quad) that minimises EMR? Maybe that's tuned to work best for 50Hz-60Hz?
- Johnythree 5y ago
  Using a twisted pair cancels out both the magnetic and electric field. But it also more than doubles the cost and the size of the cable. Which is why all existing DC transmission lines use earth return circuits.
kuhewa 5y ago
The sugar metabolism part really doesn't strike me as too interesting. Less movement explains less lactate production.
sitkack 5y ago
Also of note, Ants are attracted to electric fields as well. https://www.jstor.org/stable/25085325 https://www.jstor.org/stable/25085325 > Ants are strongly attracted to both AC and DC electric fields (Fig. 2). The numbers that accumulated increased with an increase in the voltage for both DC and AC voltages, and for all species. Some species (P. comanche, Ph. hyatti) show little or no response to voltages lower than 50 volts. Other species showed slight responses to lower voltages, although the response greatly increased at voltages above 60 volts. No difference in ants' responses was detected between AC and DC generated fields (Fig. 2), although ants leave AC powered points at a slower rate due to a possible residual effect of AC (MacKay et al., 1989). Ants of all three subfamilies responded in a similar manner.
- beeforpork 5y ago
  Volt is not a unit of an electric field. Talking about '50 volts' is complete nonsense in a context of an electric field. Also, a magnetic field around a wire will establish if there is a moving charge inside the wire, which can be established with any voltage -- as long as there is current, which is measured in ampere. Electric charge is measured in coulomb and magnetic fields are given in tesla -- so there cannot be a connection if they talk about 'volt'. I am not saying there isn't any link but I am saying that 'volt' is surely the wrong connection, so this should be taken with utmost caution.
  - mattkrause 5y ago
    It's better in context. The unit of electric field strength is V/m. They put ants inside a test apparatus, so the "per meter" part is fixed (by its design) and the voltage is experimentally manipulated. They do use the right units elsewhere in the paper. I imagine this was done to avoid measuring the electric field in the electrode/air/floor/ant medium, which is not exactly homogeneous.
beeforpork 5y ago
This is highly, highly dubious without a physical explanation. Or with representative statistical data. Magnetic and electric fields do not interact much with biological matter, so something 'special' needs to be shown here before there is a point. This should be treated with utmost caution without statistical and physical proof.
- samatman 5y ago
  This is categorically false, both magnetic and electric senses in other animals have been proven to exist, pigeons for magnetism and the electric organ in bony fishes. It's not at all physically implausible that crabs sense some electric or magnetic character in the surrounding water through their antennae or some other organ. Electroreception is known in bees, why not crabs? This could easily be the first evidence of that. https://en.wikipedia.org/wiki/Electroreception https://en.wikipedia.org/wiki/Electroreception
  - beeforpork 5y ago
    But I am not saying that the phenomenon does not exist. I am saying that I am lacking evidence in the article. Evidence could be statistical (if we don't know how yet) or physical (if we do know how, like, a sense was identified). But for me, pointing to a bunch of crabs on a cable and making assumptions is not enough.
    - samatman 5y ago
      No, you were saying it's inherently dubious without either statistical or physical evidence. I'm replying, no, there's nothing dubious about it. Which doesn't mean it's accurate. Biology has always prominently featured observation from life, and this is, in general, how the field first starts to suspect that, say, bees can sense electric fields. Experiments on crabs might and should follow, but your skepticism isn't grounded in anything here.
      - beeforpork 5y ago
manholio 5y ago
The obvious solution to this is to change the design of the cable so that it won't emit significant electromagnetic radiation. For example, a coaxial cable will successfully contain magnetic fields for both AC and DC lines.
- riskable 5y ago
  Yet another reason why the world needs room temperature superconductors. Actually, in this application the water temperature only goes up to 20°C (at the surface) but at the bottom of the ocean in these areas it's more like 10°C. So the bar is slightly lower.
ganzuul 5y ago
The description made it sound like they discovered how to live like a vegetable in front of cable TV. Perhaps this is the final stage of crustaceanification?
myfavoritedog 5y ago
superkuh 5y ago
This is crackpottery. What is the mechanism of action that such a weak low frequency AC magnetic field could effect the biology? There is none. This makes about as much sense as that crazy neighbor who lives without power and rants about how they can feel cell phones.
- mattkrause 5y ago
  Neurons and muscles are electrically active, so an external electric field can weakly polarize a cell, and thereby alter its response to ongoing activity. They're not magnetically active, but moving conductors in a magnetic field produce current, so it's not wildly implausible. Indeed, if you were a crab getting unexpectedly stimulated, sitting still would be one way to make it stop!
  - superkuh 5y ago
    The rate of change in current, dI/dt, determines the rate of change in magnetic field and so induced voltage. In order to depolarize neurons in transcranial magnetic stimulation dI/dT in the magnetic coils placed directly above the tissue is about 2000-6000 amps per millisecond. Even a lot of AC power at low frequency in a single wire pair (or whatever) is not in any circumstances going to induce a voltage across or along a membrane or even in extracellular space that can effect the polarization of a neuron. So it is clear that changes in the magnetic field inducing voltages cannot be the mechanism of action in this case.
    - mattkrause 5y ago
      TMS produces suprathreshold stimulation: it can take a neuron from its (passive) resting potential to spike threshold, all by itself. The numbers you give are correct for that. Weaker stimulation can't do that, but subthreshold stimulation can "nudge" the timing of spikes. In a living brain, neurons are constantly bombarded with synaptic input, and therefore sit closer to spike threshold and occasionally spike. Weak stimulation can therefore cause them to fire a bit sooner or later than they otherwise would. Since information is carried not just by the overall amount of firing, but also the spatiotemporal structure of that activity, these subthreshold changes can lead to overt changes in behavior. The recurrent nature of the brain can also amplify these effects. I know this because I've literally measured it in macaques and found that fields well below 1 V/m (produced by ±2 mA 5-40 Hz AC on the scalp) are enough to reorganize spike trains. Here's one of our papers: http://packlab.mcgill.ca/Krause%20et%20al%202019.pdf http://packlab.mcgill.ca/Krause%20et%20al%202019.pdf FWIW, I was surprised by these results--and deeply relieved when they replicated!
willis936 5y ago
>Dr Alastair Lyndon, from Heriot-Watt University, said: “Underwater cables emit an electromagnetic field. When it’s at a strength of 500 microTeslas and above, which is about five percent of the strength of a fridge door magnet, the crabs seem to be attracted to it and just sit still. For reference, this is the magnitude of Earth's magnetic field. What's the strength of magnetic fields around undersea cables? https://www.mdpi.com/2077-1312/9/7/776/htm#B15-jmse-09-00776 https://www.mdpi.com/2077-1312/9/7/776/htm#B15-jmse-09-00776 From the paper: >EMF strengths predicted around subsea power cables, as reported in the literature, vary from 140–8000 µT [15,17,18]. A commonly utilised cable operating at 1600 A is expected to produce an EMF of 3200 µT in a perfect wire, at the cable surface [17]. As with all EMF, the values will decrease with distance from the source, resulting in a field strength of 320 µT and 110 µT at 1 m and 4 m respectively [17]. 15: https://dspace.lib.cranfield.ac.uk/bitstream/handle/1826/7785/Final%20report.pdf?sequence=1 https://dspace.lib.cranfield.ac.uk/bitstream/handle/1826/778... 426 pages sheesh. Page 25 (37 in the pdf) discusses the magnetic field strength model. No math but references. I'm getting more nervous because the references are all related to modeling power lines in air. Table B-1 shows a list of submarine power lines and Table B-2 contains their simulated magnetic field strengths. Medium does affect magnetic field geometry. It'd be nice if someone took some actual measurements if they're not going to use a decent model.
- idealmedtech 5y ago
  My understanding is that, in an ideal case, the medium only affects epsilon and mu, the permittivity and permeability, which are easily found and substituted from lookup tables.
  - throwawayninja 5y ago
    "In theory, practice and theory are the same. In practice, they are not."
    - CyberDildonics 5y ago
      Do you have a reason why lookup tables don't work here or are you regurgitating this quote without evidence that it makes sense in this context?
paul_f 5y ago
The area affected is infinitesimal compared to the total area of the sea floor. This is hardly an issue to get worked up about.
- _Microft 5y ago
  If a/every cable separates the seafloor into two different habitats that cannot be moved between then this actually is an issue.
gigatexal 5y ago
Aww man I feel terrible for the crabs. But I doubt the impact to them, no, I doubt the save-the-crabs-lobby will out influence the under-water-power lobby. RIP brown crabs.
zelon88 5y ago
Isn't this the animal that covers Christmas island with population numbers in the billions and we watch cars drive over thousands of them at a time every couple years? Yeah sounds like a Darwinian problem to me.
eternityforest 5y ago
Is there any way, even in theory, we could practically carry power without all these wires? Copper isn't exactly eco friendly or all that cheap or common(Which doesn't stop anything from using it in purely mechanical things that could have been plastic or steel....). Maybe we just need more point of load solar.
- pengaru 5y ago
  > Copper isn't exactly eco friendly or all that cheap or common(Which doesn't stop anything from using it in purely mechanical things that could have been plastic or steel....). TFA doesn't mention copper at all, the high-tension wires running above my street are composed of stranded tubes of aluminum.
dshpala 5y ago
So now we have a simpler way of harvesting crabs? I'm all for it, crabs are delicious.
thehappypm 5y ago
Interesting. Presumably these are AC lines? By first principles, DC current doesn’t produce magnetic fields. HVDC I think is more niche
- Johnythree 5y ago
  DC current most definitely does create magnetic fields.
  - thehappypm 5y ago
    Right right, they produce static magnetic fields, which are rather boring compared to AC’s changing magnetic fields which can induce currents. I would imagine inducing currents could be a problem in seawater.
iancmceachern 5y ago
What if it's not em related and is just that the cables are warm?
treszkai 5y ago
> “This could mean we have a build-up of male crabs in the south of Scotland, and a paucity of them in the northeast and islands, where they are incredibly important for fishermen’s livelihoods and local economies." Thankfully that prediction can be verified easily before we jump to solutions such as burying underwater power cables. Which is great, as such a falsifiable prediction is a welcome part of a scientific paper.
giuliomagnifico 5y ago
Looks like the underwater power cables are almost "a drug" for crabs, very curious: >Dr Alastair Lyndon, from Heriot-Watt University, said: “Underwater cables emit an electromagnetic field. When it’s at a strength of 500 microTeslas and above, which is about five percent of the strength of a fridge door magnet, the crabs seem to be attracted to it and just sit still. >“That’s not a problem in itself. But if they’re not moving they’re not foraging for food or seeking a mate. >“The change in activity levels also leads to changes in sugar metabolism - they store more sugar and produce less lactate, just like humans.”
- marcusverus 5y ago
  Alternative hypothesis: It seems to me that they're being drawn to these power cables like moths to a flame. There's a comment above in which some guy observes that the strength of the EM field emitted by these cables is similar in strength to the Earth's EM field. The article also mentions that these crabs migrate. Presumably they migrate using some organ that is sensitive to the earth's magnetic pull. We know what happens when moths--who use light to navigate--encounter artificial lights. Their navigation hardware can't handle it, and they end up circling the light. This seems like the same kind of thing.
  - jaquers 5y ago
    I thought the same thing - reminded me of birds. (I was casually aware that we knew they had some sort of magnetism sensing, but hadn't caught up with the fact that we think it is a visual thing) https://www.sciencealert.com/birds-see-magnetic-fields-cryptochrome-cry4-photoreceptor-2018 https://www.sciencealert.com/birds-see-magnetic-fields-crypt... One last random association "I want to see Gamma Rays!" https://youtu.be/mPnx3zO3SDc?t=70 https://youtu.be/mPnx3zO3SDc?t=70
mentalpiracy 5y ago
>> “The change in activity levels also leads to changes in sugar metabolism - they store more sugar and produce less lactate, just like humans.” Sounds like someone has just discovered a way to farm tastier brown crabs.
- myfavoritedog 5y ago

Wait, so you're telling me that lobster actually does stick to magnet? [0] https://www.albinoblacksheep.com/flash/lobster https://www.albinoblacksheep.com/flash/lobster

nonrandomstring 5y ago

I think there's a difference between them being "attracted" to the short range field, and being disoriented as they climb over the cable. Maybe it's the heat or inductive heating effect they like. EM shielding the cables would make them too heavy. Switching to DC transmission might fix it, but the cable loss would be higher and the cost of rectifying and remodulating to AC would be high. Two thoughts come to mind. More cables in parallel carrying less current, which gives the added advantage of redundancy. Short breaks in the flow, like a railway crossing for crabs, for 5 minutes or however it takes them to get unstuck and go along their crabby business.

croisillon 5y ago
crabby business <3
jakear 5y ago
Combine the two? Several smaller cables with a cycling subset powered at any given moment.
7952 5y ago
More cables could disrupt the sea bed more during construction and cause more harm to plants and animals.
xxs 5y ago
>Switching to DC transmission might fix it, but the cable loss would be higher AC loses due to reactive impedance and skin effect should always be higher than DC transmission. DC might make sense if the generation is solar based, as it naturally generates DC, although converting it to higher voltages must have an AC step.
- roomey 5y ago
  The highest capacity sub sea transmission cables are DC now I think. There is an interconnect between Ireland and France that is DC if memory serves. I think it's only efficient for the largest capacity lines tho
  - 7952 5y ago
    AC cables are just more expensive per km, I think due to skin effects.
    - Johnythree 5y ago
      That and the enormous capacitance between a long cable and the sea.
  - XorNot 5y ago
    DC is also used because you avoid grid synchronization issues, and this is generally the trend for long distance connects now in general. It means the grids can have frequency divergence without affecting the transmission line itself.
    - Lascaille 5y ago
      The issue with DC transmission in subsea cables is that the XLPE insulation can become polarized and - from what I remember - have water drawn into it due to the consistency of the field.
      - spookthesunset 5y ago
        You could probably flip the current at periodic intervals to deal with this.
        Lascaille 5y ago
        You're talking about flipping the polarity, going occasionally from conductor-positive to conductor-negative (the shield must remain at ground potential.) If I remember correctly that actually makes things much worse if you've operated at one potential for a considerable amount of time. You could operate the cable at AC ~ 0.1Hz but your ability to actually transmit MWH would suck.
lm28469 5y ago
> More cables in parallel carrying less current, which gives the added advantage of redundancy. Every time we have a problem with tech the answer always is "just add more", idk how to feel about that
- politelemon 5y ago
  Or more abstractions. Where the original problems that we were trying to get away from, resurface in new ways, and previously solved problems have to be reimplemented.
- riskable 5y ago
  Adding more of something is often the simplest and cheapest way to fix problems. Example: Adding a few more VMs or containers costs almost nothing. Paying developers to eke out 10% more performance is expensive. Another example: Microcontrollers that have loads of pins (e.g. 100) and support many different peripherals (i.e. protocols like I2C) are expensive (say, $10-20). Little ones with a medium amount of pins (e.g. 56) and support for limitless protocols are cheap ($1). So if your PCB needs just a few more GPIO pins to accomplish something it makes more economic sense to just "add another" little MCU rather than "go big". Even if it makes programming the thing slightly more complicated.
HPsquared 5y ago
Maybe a barrier to prevent underwater critters from getting too close to the cable. Some kind of tubular fence?
rand0mx1 5y ago
You are claiming that DC losses are high, can you cite any source.
- bluGill 5y ago
  Probably only historical ones. In the past it wasn't easy to get high voltages with DC, so losses where higher. These days we are better at changing voltages, and so DC losses the same as AC with similar voltages (skin effects still can be a small difference). I understand we can actually run DC at higher voltages than AC, though I'm not enough of an EE to explain why. IF this is true, then DC losses would be less than AC.
- riskable 5y ago
  DC-to-AC losses used to be high (historically) because of inefficient inverter technology. These days we have 90-95% efficiency inverters (that are built to match their HVDC voltages). It's interesting because the reasons why we built everything using AC in the past don't really apply anymore (well, most of the time). DC is more efficient for most domestic and industrial electricity utilization. Things like lighting, air conditioning/heating, refrigerators, etc are all more efficient if fed from DC. Think about it: How many "wall warts" have we got in our homes these days? All our LED light bulbs have built-in inverters and that decreases their efficiency. Our PCs use DC for literally everything internally. The list goes on and on. I had also read a while back that grid-scale DC power transmission could be more resilient because the power transformers aren't as expensive. It's like $8 million for one of those giant high voltage AC transformers they have at power stations whereas with high voltage DC the equipment is cheaper but you have more of it (or something like that; I wish I could remember the details but this was an explanation given to me from a DC fanboy lineman over 10 years ago). The idea being: If bad weather breaks your giant $8 million AC transformer that's a real expensive pain in the ass but if it breaks a handful of small DC transformer components that's a quick (and cheap) fix.
  - pitaj 5y ago
    > LED light bulbs have built-in inverters Think you meant rectifiers here.

plufz 5y ago

Time to start making cute tinfoil hats for the crabs!

amelius 5y ago
Tinfoil does not block magnetism.
- deleted 5y ago
  [deleted]
- chiefalchemist 5y ago
  It's a cheeky reference to power grid cables on land having (negative) influence on the health of humans; and that being dismissed as "conspiracy theory." Regardless, at a more practical level, sea creatures can't wear hats, tinfoil or otherwise.
  - mschuster91 5y ago
    > It's a cheeky reference to power grid cables on land having (negative) influence on the health of humans; and that being dismissed as "conspiracy theory." The thing is, there is no scientifically validated evidence of that effect; also, there is no proof of humans being able to sense (electro-)magnetic fields.
    - kenniskrag 5y ago
      They can. If it is strong enough you can feel dizzy if you move the head. Heat and nerve stimulation is also possible according to https://en.m.wikipedia.org/wiki/Safety_of_magnetic_resonance_imaging https://en.m.wikipedia.org/wiki/Safety_of_magnetic_resonance...
    - nashashmi 5y ago
      At a sufficiently intense fields, humans can detect them. Besides, for science you need to provide evidence for an affect to prove it exists. For people you need to provide the “negative” of evidence to prove it doesn’t exist. People and science are not the same.

Gravityloss 5y ago

There are things like bottom trawling that basically swipes the whole sea floor. Plants and corals are destroyed. https://www.youtube.com/watch?v=NKG5sbnhvWg https://www.youtube.com/watch?v=NKG5sbnhvWg But it's not visible to the surface directly.

londons_explore 5y ago

Underwater power cables can be designed to have zero electrical and zero magnetic fields emitted from them. Typically that's done by using a grounding shield (which eliminates electrical fields), and by making sure currents in all directions are balanced (eliminating magnetic fields). As far as I'm aware, nearly all modern high capacity cables are built this way already. It's only old stuff (which tries to use the earth as a conductor) or low capacity stuff (which is sometimes AC and not well balanced) where this isn't true.

londons_explore 5y ago
> a grounding shield (which eliminates electrical fields), This makes all electrical fields zero... but in the ocean there may be other natural electrical fields that don't appreciate being zeroed out...
nonrandomstring 5y ago
Right. Not an electrical engineer, but isn't there something like a counter-twisted pair (quad) that minimises EMR? Maybe that's tuned to work best for 50Hz-60Hz?
Johnythree 5y ago
Using a twisted pair cancels out both the magnetic and electric field. But it also more than doubles the cost and the size of the cable. Which is why all existing DC transmission lines use earth return circuits.

kuhewa 5y ago

The sugar metabolism part really doesn't strike me as too interesting. Less movement explains less lactate production.

sitkack 5y ago

Also of note, Ants are attracted to electric fields as well. https://www.jstor.org/stable/25085325 https://www.jstor.org/stable/25085325 > Ants are strongly attracted to both AC and DC electric fields (Fig. 2). The numbers that accumulated increased with an increase in the voltage for both DC and AC voltages, and for all species. Some species (P. comanche, Ph. hyatti) show little or no response to voltages lower than 50 volts. Other species showed slight responses to lower voltages, although the response greatly increased at voltages above 60 volts. No difference in ants' responses was detected between AC and DC generated fields (Fig. 2), although ants leave AC powered points at a slower rate due to a possible residual effect of AC (MacKay et al., 1989). Ants of all three subfamilies responded in a similar manner.

beeforpork 5y ago
Volt is not a unit of an electric field. Talking about '50 volts' is complete nonsense in a context of an electric field. Also, a magnetic field around a wire will establish if there is a moving charge inside the wire, which can be established with any voltage -- as long as there is current, which is measured in ampere. Electric charge is measured in coulomb and magnetic fields are given in tesla -- so there cannot be a connection if they talk about 'volt'. I am not saying there isn't any link but I am saying that 'volt' is surely the wrong connection, so this should be taken with utmost caution.
- mattkrause 5y ago
  It's better in context. The unit of electric field strength is V/m. They put ants inside a test apparatus, so the "per meter" part is fixed (by its design) and the voltage is experimentally manipulated. They do use the right units elsewhere in the paper. I imagine this was done to avoid measuring the electric field in the electrode/air/floor/ant medium, which is not exactly homogeneous.

beeforpork 5y ago

This is highly, highly dubious without a physical explanation. Or with representative statistical data. Magnetic and electric fields do not interact much with biological matter, so something 'special' needs to be shown here before there is a point. This should be treated with utmost caution without statistical and physical proof.

samatman 5y ago
This is categorically false, both magnetic and electric senses in other animals have been proven to exist, pigeons for magnetism and the electric organ in bony fishes. It's not at all physically implausible that crabs sense some electric or magnetic character in the surrounding water through their antennae or some other organ. Electroreception is known in bees, why not crabs? This could easily be the first evidence of that. https://en.wikipedia.org/wiki/Electroreception https://en.wikipedia.org/wiki/Electroreception
- beeforpork 5y ago
  But I am not saying that the phenomenon does not exist. I am saying that I am lacking evidence in the article. Evidence could be statistical (if we don't know how yet) or physical (if we do know how, like, a sense was identified). But for me, pointing to a bunch of crabs on a cable and making assumptions is not enough.
  - samatman 5y ago
    No, you were saying it's inherently dubious without either statistical or physical evidence. I'm replying, no, there's nothing dubious about it. Which doesn't mean it's accurate. Biology has always prominently featured observation from life, and this is, in general, how the field first starts to suspect that, say, bees can sense electric fields. Experiments on crabs might and should follow, but your skepticism isn't grounded in anything here.
    - beeforpork 5y ago

manholio 5y ago

The obvious solution to this is to change the design of the cable so that it won't emit significant electromagnetic radiation. For example, a coaxial cable will successfully contain magnetic fields for both AC and DC lines.

riskable 5y ago
Yet another reason why the world needs room temperature superconductors. Actually, in this application the water temperature only goes up to 20°C (at the surface) but at the bottom of the ocean in these areas it's more like 10°C. So the bar is slightly lower.

ganzuul 5y ago

The description made it sound like they discovered how to live like a vegetable in front of cable TV. Perhaps this is the final stage of crustaceanification?

myfavoritedog 5y ago

superkuh 5y ago

This is crackpottery. What is the mechanism of action that such a weak low frequency AC magnetic field could effect the biology? There is none. This makes about as much sense as that crazy neighbor who lives without power and rants about how they can feel cell phones.

mattkrause 5y ago
Neurons and muscles are electrically active, so an external electric field can weakly polarize a cell, and thereby alter its response to ongoing activity. They're not magnetically active, but moving conductors in a magnetic field produce current, so it's not wildly implausible. Indeed, if you were a crab getting unexpectedly stimulated, sitting still would be one way to make it stop!
- superkuh 5y ago
  The rate of change in current, dI/dt, determines the rate of change in magnetic field and so induced voltage. In order to depolarize neurons in transcranial magnetic stimulation dI/dT in the magnetic coils placed directly above the tissue is about 2000-6000 amps per millisecond. Even a lot of AC power at low frequency in a single wire pair (or whatever) is not in any circumstances going to induce a voltage across or along a membrane or even in extracellular space that can effect the polarization of a neuron. So it is clear that changes in the magnetic field inducing voltages cannot be the mechanism of action in this case.
  - mattkrause 5y ago
    TMS produces suprathreshold stimulation: it can take a neuron from its (passive) resting potential to spike threshold, all by itself. The numbers you give are correct for that. Weaker stimulation can't do that, but subthreshold stimulation can "nudge" the timing of spikes. In a living brain, neurons are constantly bombarded with synaptic input, and therefore sit closer to spike threshold and occasionally spike. Weak stimulation can therefore cause them to fire a bit sooner or later than they otherwise would. Since information is carried not just by the overall amount of firing, but also the spatiotemporal structure of that activity, these subthreshold changes can lead to overt changes in behavior. The recurrent nature of the brain can also amplify these effects. I know this because I've literally measured it in macaques and found that fields well below 1 V/m (produced by ±2 mA 5-40 Hz AC on the scalp) are enough to reorganize spike trains. Here's one of our papers: http://packlab.mcgill.ca/Krause%20et%20al%202019.pdf http://packlab.mcgill.ca/Krause%20et%20al%202019.pdf FWIW, I was surprised by these results--and deeply relieved when they replicated!

willis936 5y ago

>Dr Alastair Lyndon, from Heriot-Watt University, said: “Underwater cables emit an electromagnetic field. When it’s at a strength of 500 microTeslas and above, which is about five percent of the strength of a fridge door magnet, the crabs seem to be attracted to it and just sit still. For reference, this is the magnitude of Earth's magnetic field. What's the strength of magnetic fields around undersea cables? https://www.mdpi.com/2077-1312/9/7/776/htm#B15-jmse-09-00776 https://www.mdpi.com/2077-1312/9/7/776/htm#B15-jmse-09-00776 From the paper: >EMF strengths predicted around subsea power cables, as reported in the literature, vary from 140–8000 µT [15,17,18]. A commonly utilised cable operating at 1600 A is expected to produce an EMF of 3200 µT in a perfect wire, at the cable surface [17]. As with all EMF, the values will decrease with distance from the source, resulting in a field strength of 320 µT and 110 µT at 1 m and 4 m respectively [17]. 15: https://dspace.lib.cranfield.ac.uk/bitstream/handle/1826/7785/Final%20report.pdf?sequence=1 https://dspace.lib.cranfield.ac.uk/bitstream/handle/1826/778... 426 pages sheesh. Page 25 (37 in the pdf) discusses the magnetic field strength model. No math but references. I'm getting more nervous because the references are all related to modeling power lines in air. Table B-1 shows a list of submarine power lines and Table B-2 contains their simulated magnetic field strengths. Medium does affect magnetic field geometry. It'd be nice if someone took some actual measurements if they're not going to use a decent model.

idealmedtech 5y ago
My understanding is that, in an ideal case, the medium only affects epsilon and mu, the permittivity and permeability, which are easily found and substituted from lookup tables.
- throwawayninja 5y ago
  "In theory, practice and theory are the same. In practice, they are not."
  - CyberDildonics 5y ago
    Do you have a reason why lookup tables don't work here or are you regurgitating this quote without evidence that it makes sense in this context?

paul_f 5y ago

The area affected is infinitesimal compared to the total area of the sea floor. This is hardly an issue to get worked up about.

_Microft 5y ago
If a/every cable separates the seafloor into two different habitats that cannot be moved between then this actually is an issue.

gigatexal 5y ago

Aww man I feel terrible for the crabs. But I doubt the impact to them, no, I doubt the save-the-crabs-lobby will out influence the under-water-power lobby. RIP brown crabs.

zelon88 5y ago

Isn't this the animal that covers Christmas island with population numbers in the billions and we watch cars drive over thousands of them at a time every couple years? Yeah sounds like a Darwinian problem to me.

eternityforest 5y ago

Is there any way, even in theory, we could practically carry power without all these wires? Copper isn't exactly eco friendly or all that cheap or common(Which doesn't stop anything from using it in purely mechanical things that could have been plastic or steel....). Maybe we just need more point of load solar.

pengaru 5y ago
> Copper isn't exactly eco friendly or all that cheap or common(Which doesn't stop anything from using it in purely mechanical things that could have been plastic or steel....). TFA doesn't mention copper at all, the high-tension wires running above my street are composed of stranded tubes of aluminum.

dshpala 5y ago

So now we have a simpler way of harvesting crabs? I'm all for it, crabs are delicious.

thehappypm 5y ago

Interesting. Presumably these are AC lines? By first principles, DC current doesn’t produce magnetic fields. HVDC I think is more niche

Johnythree 5y ago
DC current most definitely does create magnetic fields.
- thehappypm 5y ago
  Right right, they produce static magnetic fields, which are rather boring compared to AC’s changing magnetic fields which can induce currents. I would imagine inducing currents could be a problem in seawater.

iancmceachern 5y ago

What if it's not em related and is just that the cables are warm?

treszkai 5y ago

> “This could mean we have a build-up of male crabs in the south of Scotland, and a paucity of them in the northeast and islands, where they are incredibly important for fishermen’s livelihoods and local economies." Thankfully that prediction can be verified easily before we jump to solutions such as burying underwater power cables. Which is great, as such a falsifiable prediction is a welcome part of a scientific paper.

giuliomagnifico 5y ago

Looks like the underwater power cables are almost "a drug" for crabs, very curious: >Dr Alastair Lyndon, from Heriot-Watt University, said: “Underwater cables emit an electromagnetic field. When it’s at a strength of 500 microTeslas and above, which is about five percent of the strength of a fridge door magnet, the crabs seem to be attracted to it and just sit still. >“That’s not a problem in itself. But if they’re not moving they’re not foraging for food or seeking a mate. >“The change in activity levels also leads to changes in sugar metabolism - they store more sugar and produce less lactate, just like humans.”

marcusverus 5y ago
Alternative hypothesis: It seems to me that they're being drawn to these power cables like moths to a flame. There's a comment above in which some guy observes that the strength of the EM field emitted by these cables is similar in strength to the Earth's EM field. The article also mentions that these crabs migrate. Presumably they migrate using some organ that is sensitive to the earth's magnetic pull. We know what happens when moths--who use light to navigate--encounter artificial lights. Their navigation hardware can't handle it, and they end up circling the light. This seems like the same kind of thing.
- jaquers 5y ago
  I thought the same thing - reminded me of birds. (I was casually aware that we knew they had some sort of magnetism sensing, but hadn't caught up with the fact that we think it is a visual thing) https://www.sciencealert.com/birds-see-magnetic-fields-cryptochrome-cry4-photoreceptor-2018 https://www.sciencealert.com/birds-see-magnetic-fields-crypt... One last random association "I want to see Gamma Rays!" https://youtu.be/mPnx3zO3SDc?t=70 https://youtu.be/mPnx3zO3SDc?t=70

mentalpiracy 5y ago

>> “The change in activity levels also leads to changes in sugar metabolism - they store more sugar and produce less lactate, just like humans.” Sounds like someone has just discovered a way to farm tastier brown crabs.

myfavoritedog 5y ago