Galway bay is subject to diurnal tides resulting in the shoreline being exposed twice in roughly each 24 hour period. Every time the tide goes out mobile organisms such as fish, crabs, amphipods and polychaete worms move to places of shelter. Some fish can swim out with the water however others, along with the likes of the common shore crab and various amphipods, simply entrench themselves under rocks and in crevices. Almost anywhere damp will suffice for these animals as they wait and mull over their saltationary existance until the next incoming tide entices them out to continue their particular day to day activities. Polychaete worms can burrow into the mud and there are some which build shelters from sand and shell fragments.
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| What it's all about. Galway bay from the sea to the coast |
In contrast to those animals that can move to an under-rock sanctuary or the like there are slow moving animals along with non-mobile or sessile organisms which includes limpets, periwinkles, sea anenomes, barnacles, bryozoans, various bivalves, seaweeds and other algae which have to come up with another strategy to survive the twice-daily exposure. Limpets and perwinkles simply clamp down to a suitable substrate and wait for submergence. Fixed organisms such as bryozoans are often found on the underside of rocks where it remains damp the longest. Seaweeds and other algae have evolved physiological adaptations to dessication or are simply not able to live in the intertidal zone because they need constant water cover.
This is a really simple view of the life of intertidal flora and fauna however I hope that you appreciate that water is the main deciding factor in the existence of all involved. So, bearing this in mind, if there was a way for an organism to exist happily between each low tide rather than having to wait out the hours until the tide comes in again, this would become the preferred mode of lifestyle. This is why rock pools are hot property in the indertidal world.
More rock pools equals a better standard of living in our scenario, the equivalent of a human moving from the desert along Africa's Skeleton coast to a small well-stocked town in a prosperous country. As a consequence of an increased abundance of rock pools, animal and plant species can become more abundant and live in greater densities.
This increase in the variation of the environment, or in other words, the increased heterogeneity, allows for a greater number of niches which can be filled by a greater number of species; hey presto, more biodiversity!
This quick overview will hopefully help when reading about the experiment itself.
Keith Me inside my plush workspace
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