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The effects of extreme intertidal variation on water retention in molluscs
Abstract
The ability of marine organisms to retain water is fundamental to their survival in the intertidal zone
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The Ria Formosa is a tidal lagoon that is highly susceptible to changes in sea level as a result of
climate change
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In the
study we measured the percentage of mass lost by both species when they were immersed and kept
out of water for different periods of time
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The study showed that Mytilus galloprovincialis lost significantly more water than Gibbula
umbilicalis and that both species lost significantly more water when they were left out for long
periods of time
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These results indicate that gastropod molluscs could be much more effective at retaining water than
bivalve molluscs
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This shows that both species of mollusc could be
very effective at maintaining water balance in the event of rising sea levels as a result of climate
change
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Such changes can drastically alter the
amount of time a species is immersed or out of water
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Tidal ranges would be
altered, potentially causing organisms to endure longer intervals of exposure and immersion
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Exposing an individual to different constant conditions enables us to test whether they have the
ability to respond to environmental changes and maintain internal stability in terms of water
retention
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(Pers obs
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To extend on this study, the experiment will compare Gibbula umbilicalis and Mytilus
galloprovincialis to see whether gastropods and bivalves can endure extreme changes in water
levels, by testing their ability to retain water in different conditions, such as long exposure and long
submersion (simulating the extreme tidal range)
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In addition, when testing the species
individually in different constant conditions we predict the individuals will retain less water after
longer submersion times
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Both Mytilus galloprovincialis and Gibbula umbilicalis retained significantly less water the
longer the post-treatment (in a linear fashion) SF,123= p<0
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SF,123= p<0
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This in turn will affect periods of immersion and emersion in intertidal zones on
all coasts
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Our first hypothesis was that Mytilus galloprovincialis would retain more water than Gibbula
umbilicalis It can be seen from the results that this is not the case, with Gibbula umbilicalis retaining
on average 3% more water than Mytilus galloprovincialis The cause of this difference is unclear, but
could be due to differences in shell size/colour, or available space for water storage within each
species
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Our second hypothesis was that an organism would retain less water after a longer period of
submersion
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This was observed in in a previous study in Roscoff, 2015, in Gibbula umbilicalis
where individuals lower on the shore, which were therefore submerged for longer, retained
significantly less water than those on the upper shore
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The driving force behind this change is unclear, but perhaps
exploring circa-tidal patterns of behaviour in these species would be a good area of further study to
pursue
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