Last week our BIOL 326 class took part in a virtual field trip organized by the Bamfield Marine Sciences Center. During the tour we had the opportunity to look at the huge variety of of intertidal marine organisms living around the research center in Bamfield, BC.
What is the intertidal zone?
The intertidal zone can be found on any shore with a tidal body of water. During high and low tide organisms experience higher temperature and salinity variations in addition to longer times exposed to air and direct sunlight. On top of all these factors, organisms, especially those that cannot move (i.e. sessile) also have to compete for space. This combination of biotic and abiotic factors result in high competition and distint levels of the intertidal zone being occupied by different organims. This is what intertidal biologists call “zonation”.
Image source:https://www.pinterest.ca
What we saw at Bamfield?
At Bamfield we had an opportunity to look at both the rocky intertidal and also tide pools that emerge during low tide.
The Grainyhand Hermit Crab
This little critter is one of the common inhabitants of the intertidal, it can be easily identified by the blue dots on its body and also the orange-coloured antennae. Like other hermit crabs they do not make their own shells, but rather use shells discarded by marine snails that do make shells!
Speaking of shells, in Bamfield you’ll see hermit crabs using shells from Black Turban Snails and Dire Whelks that are also found in the intertidal. The Black Turban Snail is a herbivore and feeds on algae, whereas Dire whelks are predatory and feed on other snails by using their radula, a nail file-like tongue that can drill holes in shells!
Black Turban Snail on the left (Image source: https://www.centralcoastbiodiversity.org/black-turban-snail-bull-tegula-funebralis.html) and Dire Whelk on the right (Image source https://inaturalist.ca/taxa/117642-Lirabuccinum-dirum)
Porcelain crabs are also one of the species we saw at Bamfield. When the tide goes out, they like to hide under rocks where it’s still wet which means they have an easier time breathing. Even though crabs venture onto land they still use gills to breathe, so keeping them wet is very important for the crabs. Porcelain crabs, despite their name are not true crabs. They technically classify as false crabs due to having one fewer pair of walking legs than true crabs, which have four.
One other cool thing about porcelain crabs is that they can remove limbs at will! When they are attacked by an animal that wants to eat them they can detach a limb to confuse their predators, but don’t worry they can grow them back as they continue to molt.
Why is the intertidal important?
The intertidal zone maintains a balance between the land and the sea. It provides a home to specially adapted marine plants and animals. Those organisms, in turn, are part of the complex food webs of many other animals.
The intertidal zone also stops erosion caused by storms. Oyster reefs are one such example that prevent the endless battering of the waves on shore from damaging natural and artificial structures on the shore
All of the animals I mentioned are only a small part of the intertidal ecosystem. No blog can help you to truly understand the diversity and beauty of the intertidal, to accomplish that you need to go outside and see it for yourself. Remember to put everything you find back where it belongs!
In the meantime you may want to watch this documentary on the intertidal, it even features UBC’s own Dr. Patrick Martone!
https://www.cbc.ca/natureofthings/episodes/kingdom-of-the-tide
BIOL 326: Experimental biology of invertebrates 