OUR GRASSY OCEAN MEADOWS

“Grass that grows in seawater?”, Dalton Koss HQ is often asked. Yes, grass that can grow in and withstand seawater. But how?

Seagrass is similar to land-based grass, having leaves, veins and roots. The leaves grow from the base of the leave and reproduce with flowers and seeds. Many individual seagrass plants found growing together is termed a seagrass bed or seagrass meadow. Seagrass meadows can be found across the globe, usually in coastal areas close to shore where sunlight can penetrate the water column. Like all plants, seagrass needs sunlight to grow.

The different parts of the seagrass, Amphibolis antarctica, or commonly known as the sea nymph.
The different parts of the seagrass, Amphibolis antarctica, or commonly known as the sea nymph.

Although seagrass meadows may not look like much to the casual observer, they play an incredibly important role in supporting not only the health of our coasts and oceans, but also to humans. There are so many incredible facts about seagrass that DKHQ would like to share with you.

Did you know that seagrass meadows are nurseries for baby sea animals, providing shelter and protection from bigger animals and food to help them grow? Most of the fish we buy to eat would have spent some of their younger years living and growing in seagrass meadows before swimming to the oceans as adults.

An eleven arm seastar (Coscinasterias muricate) and small mussels (Electroma georgiana) living in swan grass (Zoestera muelleri).
An eleven arm seastar (Coscinasterias muricate) and small mussels (Electroma georgiana) living in swan grass (Zoestera muelleri).

Due to the amazing root network of seagrass, they are able trap and stabilise soft sediments, sand and other very small items floating in seawater. This means seagrass plays an important role in protecting our shorelines from erosion and helps improves seawater clarity.

In areas of seagrass meadows there are less toxic algal blooms. Seagrass is amazing at absorbing a whole lot of different nutrients, that often contribute to algal blooms, and using it as food to grow.

The seagrass plant is like a small cosmos to itself. It provides a solid surface for other small seaweeds, sponges and animals to grow.

A meadow of Southern strapped (Posidonia australis) in Corner Inlet Marine National Park, Victoria.
A meadow of Southern strapped (Posidonia australis) in Corner Inlet Marine National Park, Victoria.

Worried about high carbon levels in the atmosphere? Seagrass is able to absorb and store large quantities of carbon in their leaves and roots. Let’s protect seagrass so it can be a wonderful and natural way to address our high carbon lifestyles.

If you ever have an opportunity to snorkel in a grassy ocean meadow, do not pass it up! You might just be surprised with what you find.

A beautiful and vibrant red sponge growing in the Southern strapweed.
A beautiful and vibrant red sponge growing amongst the Southern strapweed.

Sea Anemones of the Southern Ocean

At DKHQ we are constantly asked whether some of the facts portrayed on Finding Nemo are true, specifically the much difficult to pronounce Sea Anemone. Pixar did a wonderful job raising the profile of tropical reefs, although to the detriment of Clown Fish who, if the facts are correct, were being flushed down toilets by young children wanting to release ‘Nemo’ back into the ocean.

This aside, the often asked sea anemone questions at DKHQ are: a. can sea anemones sting, and b. can their poison kill humans? The answer to a. is yes and to b. is no. This public fascination with sea anemones inspired today’s DKHQ Marine Fact, with a focus on southern sea anemones.

Unlike the large sea anemones of our tropical reefs systems found across the globe’s equator line, the sea anemones of the southern ocean are comparatively smaller but just as beautiful and colourful. Here are some interesting facts:

1. Southern sea anemones always occur as solitary individuals usually in intertidal and subtidal areas.

2. All sea anemones have one opening, function both as its mouth and anus (this fact usually elicits some funny facial and noise reactions). Sea anemones are carnivores, on other animals.

3. The sea anemone body is supported by water pressure, which means when not in water their body and tentacles become floppy.

4. The tentacles of all sea anemones radiate from the mouth in one or many rows and are hollow. These tentacles contain stinging cells known in marine science as nematocysts. Each nematocyst contains a pressurised coil that can be pushed out to capture prey or used as self defence. The sea anemone use the nematocysts to stun, and in some cases, kill the prey.

5. Nearly all southern ocean sea anemones grow attached to a rock or some other type of hard structure. The exception to this rule (and when it comes to Mother Nature, there is usually one exception to the rule) is the Swimming anemone known by its scientific name as Phlyctenactis tubercles. (See image below). The Swimming anemone can move through the current or crawl along hard structures.

The Swimming anemone, Phlyctenactis tuberculosa.
The Swimming anemone, Phlyctenactis tuberculosa.

So why can’t sea anemones sting us? Our skin is too thick to be penetrated by its stinging cells, unlike many sea creatures with very thin skin. In the case of Clown fish, they have adapted over a long time for their skin to not be affected by the stinging cells and use the sea anemone as a place of protection from enemies.

DKHQ hopes you enjoyed these sea anemone facts and will leave you to enjoy the beautiful colours of some of the southern ocean’s sea anemones.

This beautiful sea anemone is known as Phlyctenanthus australis and can be found along Australia's intertidal shoreline that is exposed to ocean waves.
This beautiful sea anemone is known as Phlyctenanthus australis and can be found along Australia’s intertidal shoreline that is exposed to ocean waves.
This gorgeous red sea anemone is known as the Waratah Anemone and it's scientific name Actinia tenebrosa. This lovely Waratah Anemone can be found along the intertidal shoreline, often looking like a red blob at low tide.
This gorgeous red sea anemone is known as the Waratah Anemone and it’s scientific name Actinia tenebrosa. This lovely Waratah Anemone can be found along the intertidal shoreline, often looking like a red blob at low tide.
This fun orange and white stripped sea anemone is known as Anthothoe alboctinia and can be found under rocks or underhangs along Australia's intertidal shoreline that is exposed to ocean waves.
This fun orange and white stripped sea anemone is known as Anthothoe alboctinia and can be found under rocks or underhangs along Australia’s southern intertidal shoreline that is exposed to ocean waves. There are two variations to this sea anemone, white and orange stripes and brown and green stripes.

What are those round smooth shells you find on the beach?

At DKHQ the creative talents of individuals who use natural elements in their art often fascinate us. This holds true when we see shells made into jewellery or used as decorative placements in homes and businesses.

When DKHQ was asked to identify a bowl full of white round shells used for decoration purposes, we realised its potential as a new marine fact.

This round white item (see image above) is officially known as an operculum. Attached to the upper surface of the snail’s foot, it functions as a door to the snail’s shell. Like the door to your house, the snail uses the operculum to keep unwanted visitors out.

Unfortunately, sometimes our doors do not keep pesky visitors out. When you find an operculum washed up on the shore, it usually means the snail experienced an unwanted guest and is no longer alive.

What creates those circular holes on seashells?

At Dalton Koss HQ we are often asked wonderful questions about the coastal and marine environment that we are only too happy to answer.

One question beach lovers often ask us is how are those incredibly circular holes made on the shells? The holes are so perfect, that the shells can be used as a necklace pendant (see image above).

If you recall last week’s Marine Fact, Dalton Koss HQ discussed the difference between carnivore and herbivore marine snails. Leading on from this discussion, the holes you see on these shells are made by carnivore marine snails, or more specifically by their radula.

A radula is similar to our tongue in that it assists the snail to eat. However, unlike a human’s tongue a radula looks and functions like a chainsaw (see image below). The radula is comprised of teeth like structures that have the ability to cut through hard surfaces, such as a calcareous shell. The snail will stay in one place while the radula chainsaws through the shell, hence creating a beautiful concentric circle.

Once the snail breaks through the shell, it will kill and eat the animal inside. Unfortunately, a sad ending for the prey but enabling the carnivore marine snail to survive another day.

Radula
The radula is located inside the snails mouth and acts like a chainsaw drilling through tough surfaces. Image sourced from: noaa.gov/ocean