The Intertidal Zone

Over the past few weeks, quite a number of the Dalton Koss HQ Marine Facts have referred to the intertidal zone. Many DKHQ readers have curiously responded with the questions:

  1. Where is the intertidal zone located?
  2. Exactly what is the intertidal zone?

At Dalton Koss HQ we are more than happy to answer these two questions.

The intertidal zone is located along our coastlines, specifically where the sea meets the land. This zone varies all across the globe. It can be made up of rocky shores with many fun rockpools, mudflats or sandflats, mangroves, salt marsh and seagrass beds, sandy beaches and coral reefs. The intertidal zone can be exposed to the rough and tumble of open oceans or located in sheltered places such as bays and inlets. Some scientists refer to the intertidal zone as the littoral zone.

An exposed intertidal rocky shore at low tide along Victoria's Great Ocean Road. Notice the prolific range of seaweeds adorning the rocks.
An exposed intertidal rocky shore at low tide along Victoria’s Great Ocean Road. Notice the prolific range of seaweeds and mussels adorning the rocks.

At Dalton Koss HQ we often refer to the intertidal zone being in a liminal state. This is because the intertidal zone is either covered with ocean waters or exposed to the sun and air due to the constant movement of tides. It is never in one state of being within a 24 hour period; rather it is in continuous flux.

Being exposed to two completely different types of conditions means that as an animal or plant living in this zone, one needs to have some incredibly amazing adaptations to survive. Intertidal plants and animals need to be resilient to wave wash, tides and currents, sun exposure, predators and drying out all while trying to photosynthesise/eat and reproduce.

An exposed intertidal sandy flat located along Cape Conran Coastal Park in eastern Victoria, Australia.
An exposed intertidal sandy flat located along Cape Conran Coastal Park in eastern Victoria, Australia.

This makes the intertidal zone a fascinating area to explore and discover the spectacular range of marine animals and plants. To conserve this amazing zone while you explore, please be careful where you tread/snorkel, place rocks back to their original positions when you examine what is beneath and keep all rockpool animals and plants fully immersed in water to reduce their stress.

An intertidal coral reef exposed at low tide located in Fiji's Coral Coast.
An intertidal coral reef exposed at low tide located in Fiji’s Coral Coast.

Slugs in the nud’

At Dalton Koss HQ we come up with some creative names to describe some of the more interesting creatures that can be found in our marine front yards.

Slugs in the nud’  are nudibranchs. Nudi what? Nudibranchs.

Nudibranchs are oceanic snails, do not possess a shell and are mostly brightly coloured.

To break it down, Nudi = nude and branchs = gills. As these snails do not have shells for protection, their gills are nude and exposed (see image below).

Without a shell covering, the nudibranch's gills can be found on the top part of its body and exposed to the water.
Without a shell covering, the nudibranch’s gills can be found on the top part of its body and exposed to the water.

Nudibranch Facts

1. The bright colours of nudibranchs are used as defence mechanisms to avoid predators.

2. Many are able to camouflage with their surrounding environment, such as corals and sponges.

nudi3 fixed
3. Nudibranchs do not make a tasty meal. In fact, they are toxic and poisonous to eat. This is because nudibranchs feed on the stinging cells of sea jellies, anemones and corals.

4. Nudibranchs can be found at different depths in both warm and cool ocean waters.

WA July 2005 041

Although not in the same size category of many other sea creatures, they do create a level of excitement for DKHQ when spotted under water.