Weaker Mussels in Warm Water?

You’d be forgiven for thinking that mussels attach to rocks and other substrates using a muscular foot. After all, that’s what their name implies. But mussels actually hang on using byssal threads – small fibres constructed by the mussel that are very strong while also being highly flexible.

MusselFoot300x267Researchers at the University of Washington are looking at the impacts of environmental conditions on the strength of byssal threads. They found the strength and flexibility of the threads varies with temperature and ocean pH, which could have far reaching consequences in the not too distant future.

Mussel foot (right) and byssal thread (left). Photo: Laura Coutts

The researchers compared the strength of byssal threads at 10oC and 25oC. In warmer water the mussels produced fewer threads and those that were produced were weaker than the corresponding threads created in cooler conditions. These changes were seen even as a result of short-term variations in temperature.

The warming of the ocean due to climate change could impact mussel populations by reducing their attachment strength. They may not be able to hold on as tightly to the substrate and could be washed away by waves and currents. Existing sites may no longer be habitable by mussels and there could be increased mortality if feeding is impacted by the inability to remain attached to the substrate.

Byssus threads 300x271When these temperature impacts are combined with other environmental stressors, such as ocean acidification and a change in the frequency and intensity of storms, mussels could be detrimentally affected. Mussels have a larval stage at the beginning of their life cycle, so the colonisation of cooler and calmer environments is theoretically possible.

Mussels attaching to substrate using byssal threads. Photo: Emily Carrington

Mussel migration due to changes in ocean temperature has the potential to dramatically impact intertidal ecosystem composition and dynamics. Changes in water temperature and mussel attachment strength will also have ramifications for the aquaculture industry as mussel attachment to ropes is important for productive mussel farming.

The mussel species in these experiments was Mytilus trossulus which lives mainly in the intertidal zone of the northern Pacific Ocean. Mussels are also found in warmer environments around the world, but these findings seem to imply that they may not be able to hang on to the substrate in turbulent conditions as well as their counterparts in cooler environments.

Maybe mussels in warmer environments may be more successful in habitats with calmer conditions? It would be interesting to extend these experiments to warmer conditions and possibly freshwater mussels to see if the same limitations apply to their byssal threads.

To find out more:

Newcomb LA, Carrington E, George MN & O’Donnell MJ (2014). Short−term exposure to elevated temperature and low pH alters mussel attachment strength. Abstract of presentation to The Society of Integrative & Comparative Biology, Austin, Texas, 3-7 January.

O’Donnell MJ, George MN & Carrington E (2013). Mussel Byssus Attachment Weakened by Ocean Acidification. Nature Climate Change. doi: 10.1038/nclimate1846.

Hear Professor Emily Carrington discussing this research and Professor Phillip Messersmith talking about the applications of mussel attachment for medical research on the ‘The Science Show’ Radio National podcast here.

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