Mussel Beds and Byssal Threads

Intertidal organisms experience enormous amounts of stress,

Water levels, salinity and temperature can quickly become a mess

As a result organisms produce structures from biological components

Which help them tolerate environmental conditions and their opponents

The factors that affect the integrity of these materials was the aim of my project

I tested the effects of pH, predation, mass and material abundance on the attachment force in my subjects

My organisms of choice was Mytilus trossulus, the pacific blue mussel

An important sessile, filter feeder that doesn’t go anywhere in a hustle

I collected the mussels, and then proceeded to record their mass and measure their length

They were then left under different experimental conditions for three days at which point I measured their strength

I counted the number of byssal threads produced by each individual

A number around twenty was pretty typical

Then using a handmade paperclip claw attached to a spring scale

I measured the point at which their threads would fail

After all of the mussels had been dislodged from their settlement tiles

They were put back in the seawater table as there was no time for another trial

It was time for data analysis so I headed to my mac book pro

I couldn’t wait to see what the multifactor ANCOVA would show

As it turns out the effects of pH and predator cue were insignificant

But mussel mass and the number of threads produced did make a difference

As mussel mass increased so did their attachment force to the surface below

Attachment force also increased with an increasing number of byssal threads though

These results mean that smaller mussels could be more vulnerable to predation

With less force to overturn the predatory dogwhelk and prevent penetration

Producing more threads could increase their attachment force

but the chemical cues released in the processes could make the mussel the predator’s main course

Mussel populations may be able to tolerate current predation levels

The problem will be when global warming heats up the earth like a kettle

This could cause an increase in the metabolism and appetite of animals

and predation on the small mussels could become maximal

This would have a great effect on the stability of populations

and all other organisms for which mussels are a foundation

Without mussels around to filter the ocean and make areas more habitable

Other populations will decline as well; the implications are unimaginable

To see a mussel building a byssal thread check out this video 


Mussels on settlement tiles set up in a mesocosm


Paperclip claw used to dislodge the mussels and measure attachment strength

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