#005 The Kingdom of Clones

One night after dinner in the city, I drove Keen through the winding dark streets of Bellambi and parked on a grassy verge overlooking a narrow strip of beach. The ocean was black. The lights of freight ships could be seen far away across the water. We watched a storm roll in over the horizon. White legs of lightning stabbed between the ships. Fat drops of rain splattered on the windshield. Wynhilde’s windows shuddered in the echo of thunder. We felt very safe in our tin can, connected to the ocean as we were by the onslaught of the storm.

By day Bellambi Rock Pools sit squarely between the long strip of Bellambi Beach and the gravel shoot of the boat ramp. “Ramp” doesn’t do the structure much justice: there’s room for a hundred cars, fish cleaning bays at the seaward end, and bright orange spotlights that stand out starkly all the way from Sublime Point atop the Escarpment.

But the beach is nice. The surfers like it, and I tend to trust their taste in beaches. By the rock pools is a pool where the water sloshes in at high tide, and where you can swim without fear of waves, sharks or freak freight ship accidents. Although on this particular stunning morning in April I did spy a school of pufferfish skirting around the pool’s edges.

Maybe it’s the calmness of the bay. Maybe it’s the fish blood in the water. Whatever it is, there’s an abundance of life amongst the rock pools of Bellambi not found anywhere else in the Gong.

The hunting area is small, even at mid tide. Even so you will find Brittle Stars, Elephant Snails, Eleven-Armed Seastars, Blackspot Sergeants, Common Silversides, Cocos Frillgobies, Spengler’s Tritons, Waratah Anemones, green banks of Cunjevoi sticking out into the ocean, and even if you’re not looking for one, a Gloomy Octopus may find you.

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Tube worm colony atop cunjevoi sea squirts.

Keen and I started high on the beach and worked our way towards the lowering tide line. To our great pleasure we were joined by a photographer and her daughter, who was about 4. The little girl had accompanied her mother on a photoshoot, but her patience only lasted so long, and so the pair ended up at the beach.

I’m always impressed by the amount kids know. At Windang Island a couple of little girls had shown up Keen by naming Zebra Top Snails, limpets and mussels. If kids know that much, and take such delight in combing through the rock pools, I think there really is hope for the future of the ocean.

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Dwarf Cushion Stars feeding in an algae bed.

Chasing gobies in a pool, I noticed the irregular shape of a Dwarf Cushion Star suckered to the rock wall. These tiny seastars are so well camouflaged that Keen did not see them at all, even when he was staring right at them. What started as one on the rock turned out to be dozens of all different sizes, some resting in the sun-dappled water, others slowly twirling in search of second breakfast.

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#092 Dwarf Cushion Star (Parvulastra exigua)

Unlike many seastars, Dwarf Cushion Stars are herbivorous, scraping microalgae from the rock. What makes them interesting is not just their camouflage ability, but the way they reproduce. A Dwarf Cushion Star may mate to fertilise its eggs, which are laid in a sticky mass on the underside of boulders. However, these stars are found all the way from Australia to South Africa. Such tiny stars in such a huge territory are spread out enough that one may never find a partner. In this case, the Dwarf Cushion Star is able to go asexual reproduction – creating a clone of itself. This ensures that even without a mate, the seastars survive another generation, and have another chance to find their perfect somebody.

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Top and underside of Dwarf Cushion Star. The mouth is on the bottom. Note the small grasping hands near the mouth.

As Salty excused himself to chase crabs, Keen and I moved further towards the water, where we could peer beneath the eroded rock shelf into a honeycomb of caves.

Water dripped into pools stained emerald with sea grass. Giant Spengler’s Tritons clustered in the shallows. I peered beneath an overhang to find a colony of dangling red blobs. Each was about the size of a Lindt chocolate ball, shiny and slick and deep, lustrous crimson.

Pressing a finger to the red side, I felt firm, slick flesh, like an overdone jelly. The colony of some few dozen animals was mysterious in its silence. Only a puckered opening in the blob’s apex gave any clue to the creature’s true form. Here there were wriggling scarlet fingers. As if in reflection in the water below, another colony had blossomed into a mass of red fingers like a flower of Cthulhu.

These are Waratah Anemones, prolific and beautiful. When immersed in water they open to reveal tendrils tipped in stinging cells to paralyse small prey. When the water level drops, they envelop themselves in a tight bundle, conserving water and protecting their soft inner parts from damage.

You would never guess from the sight of them, but these strange red flowers are animals.

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#012 Waratah Anemone (Actinia tenebrosa)

Yet their appearance is not the strangest thing about them. That colony beneath the overhang at Bellambi Rock Pools? They are most likely clones of one another. An individual settling on a rocky beach will give birth to live young, well-developed miniatures of the adult form. These babies settle close to the parent, establishing a colony. Clones are able to identify one another, via chemoreception or some mysterious superpower known only to clones. If a genetically diverse anemone attempts to settle near the colony, the clones will attack it, ensuring the Kingdom of Clones.

While clones are highly adapted to their strip of beach, not all Waratah Anemones are genetically similar. An anemone may release its gametes (eggs or sperm) into the ocean’s plankton, where it will be external fertilised by another drifting gamete. The resulting embryo washes up on a distant beach, where with any luck, it will being a new colony.

And it is a long-lived colony. On average, Waratah Anemones live 50 years, but they can live as long as 210 years. This really is a Kingdom of Clones.

 

I was measuring urchins in a deep tunnel near the low tide, when to my shock a black tentacle wrapped around my ruler. Instinctively I tried to yank the ruler from the water. A second tentacle joined the first, pulling my hand into a shadowy crevice in the tunnel.

Laughing now, and maybe not trying as hard as I should have, I pulled back against the octopus hidden in the corner of the tunnel. It delicately reached out and gripped the ruler in a third tentacle, and plucked it cleanly from my hand.

I put my cheek against the water, hoping to catch a glimpse of the cheeky cephalopod. It had disappeared completely into the shadow of the ledge.

Amused, I stuck my head out of the tunnel. The young girl and her mother were still looking for interesting things amongst the rocks. “Did you want to meet an octopus?”

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Do you want to meet an octopus?

The young girl charged over without hesitation. I called Keen over, and asked him sweetly if he could free the urchin from the rocks in the bottom of the pool. Keen obligingly stuck his hand into the water. A moment later, he squealed. The octopus was fishing for humans!

The octopus was a Gloomy, probably a young adult, identified by the rusty orange blush on the underside of its tentacles. Octopuses (or octopodes, but never octopi) are members of the mollusc order, the same as periwinkles, oysters and limpets. Like most molluscs, they have a siphon and a tough tongue called a radula, in octopuses modified into a beak.

That is almost where the similarities end. Octopuses are as intelligent as they are alien. An octopus is a master of camouflage and imitation, a puzzle solver, an ingenious hunter and escape artist. Each of their eight arms is partly capable of autonomous action, reducing the brain work an octopus has to do to co-ordinate.

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#067 Gloomy Octopus (Octopus tetricus)

Keen had pitted himself in a battle of strength against the octopus. The Gloomy was holding fast to the side of the tunnel, three of its tentacles squeezing Keen’s wrist. As the octopus surged forward to gain ground, its elongated head and bright orange eyes peered around the tunnel mouth. Its pupil was the shape of a bowtie, set in a streak of golden orange. Strange but beautiful eyes, fixed upon these giants of the air.

My ruler dropped down into the water. It must have slipped from the octopus’s grip. The Gloomy let go of Keen. I reached into the water to retrieve the ruler and had just a glimpse of the Gloomy retreating into the darkness of the tunnel.

I sat by the water a while, and twice more the octopus returned. I made sure the rocks I’d moved were back in place, in case they had been part of the Gloomy’s home. I imagine it must have though the ruler would make a charming addition to its living room.

While it may have been defending its home, or simply getting a taste for humans, I couldn’t help but feel the octopus was playing with us. It was happy to test its strength against ours, but never went all out, just as Keen and I restrained ourselves. There was intelligence in its gaze and the purposeful way it moved, returning the second time along the roof of the tunnel, in a place we would not expect to find it.

 

Out of a seastar, an anemone and an octopus, did you know the animal most closely related to us is the seastar? Yet all of these creatures are mysterious and strange. One looks like a cookie, another is an alien intelligence, and the last, longest-lived of them all, conquers the beach with its very own Kingdom of Clones.

 

Find out more about Waratah Anemones: University of Queensland’s Fact sheet

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A Windang Shindig

The Gong 151
#003 A Windang Shindig

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On a cool and blustery day in March, Salty, Keen Wasabi and I hiked around Lake Illawarra foreshore to the sandy arm of Windang Island. The island’s green top rises conspicuously from the lip of the lake. Anglers endure relentless plumes of spray on the seaward cliffs, each wave sending waterfalls cascading down deep flutes in the rock. Snorkelers proliferate in the summer, diving from ledges exposed at low tide, while swimmers wander up from Warilla Beach to survey the long and peaceful bay. The island is also notorious for sharks.

At 11 o’ clock the tide was at about 0.6 metres and dropping. Things that are usually submerged were becoming exposed. Keen and I dropped our nets and tanks on a rock ledge and waded out amongst the pools.

Soon we were walking on mats of Neptune’s Necklace (Hormosira banksii). This brown alga is made distinct by the string of olive-coloured beads that make up its thallus (body). Like plants, brown algae uses chlorophyll to photosynthesise and  absorb energy from the sun. Unlike plants, it also produces xanthophyll, a yellow pigment. This gives brown algae its distinct brown-green colour.

While at first it seems weird – after all, chlorophyll works perfectly well for plants – the secret of brown algae is where it exists in the ocean. Red light is bad at penetrating the ocean’s surface. Green light however penetrates deeply into the water. Because a thing’s colour is determined by the light it reflects (meaning green plants reflect green light) algae need to be differently coloured to absorb the light available to them beneath the waves. For Neptune’s Necklace, this means disguising its green chlorophyll with red pigment.

What I find fascinating about Neptune’s Necklace is just how well-equipped it is to maximise its light exposure. The alga is made up of multiple strands of beads called thalli. Each bead is made of a  spongey tissue filled with air and protected by a waxy coating. When submerged, the air makes the beads float, drawing them towards the surface, where there is more light. When the tide drops, the beads lay like a carpet across the rocks, their waxy coating preventing them from losing too much moisture.

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Shells embedded in the island’s dirt wall.

Neptune isn’t the only one who fancies his algae. As we sat by twin rock pools on the low intertidal, Keen and I counted 135 Zebra Top Snails (Austrocochlea porcata) in and around the strings of beads. Interestingly, of all the species of snail in the pools, only Zebra Tops were found on the Neptune’s Necklace. Smaller snails seemed to prefer the shelter of the algae more than the larger ones, who preferred grazing on an encrusting brown algae on the bottom of the pools.

Up until last week, I kept five Zebra Tops Snails in my laboratory aquarium. They eat the slimy brown algae that is a fact of aquarium life, and it’s fun watching a snail licking glass.

Woe betide me, this week I am down to three Zebra Tops. The reason? Clever fish. Working together, two of my fish (Holly, a Black Drummer, and Dart, a Blackspot Sergeant) repeatedly ram the Zebra Tops until they come unstuck from the glass and tumble upside-down into the sand.

Like other marine snails, Zebra Tops have a tough disc called an operculum that they can draw over the opening in their shell, like shutting a door. My fish are quite unable to get past the operculum. But, as they learned, if the snail wants to right itself, it has to push its operculum aside and stretch its soft body around the top of the shell to grab a hold of something solid. When that is done, the snail gives a quick pull and flips around upright.

Holly and Dart wait until the snail’s soft body is exposed, and attack. In just a few strikes the fish have conquered a snail as big as themselves. This bringing down of the mammoth results in tank-wide excitement, as the other drummers rush in for a nibble and the crab dances out of his cave, claws waving.

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Scary-story-snail face.

On the beach, Zebra Tops have more insidious enemies than tiny fish. Seastars prowl for young snails. You will have seen seastars sold as trinkets and jewellery. Dried and bleached, they offer poor comparison to these active hunters.

A sea star’s underside is covered in hundreds of tube feet. At the end of each arm, there is a splay of probing fingers and a rudimentary eye. A seastar can move as swiftly as a snail or abalone. It crawls over its pray, wrapping it in powerful arms. It then everts its stomach, coating its prey in digestive juices. Finally the seastar draws its stomach and its melted pray back into its body.

One such predator on Windang Island is the Eight-Armed Seastar (Meridiastra calcar.) It’s obvious when these seastars are busy eating, as their central disc will be raised into a hump, the prey engulfed beneath it. While snails are high on the menu, Eight-Armed Seastars will also graze on algae, and I have even seen them feasting on crabs’ legs and fishes’ tails.

Perhaps one reason Zebra Tops choose to hide amongst the beads of Neptune’s Necklace is that it is not readily navigated by seastars. Seastars probably also have poor vision, and cannot tell a small Zebra Top from a bead.

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Anglers enticing sharks with their juicy backsides.

“The sale of souls to gain the whole world is completely voluntary and almost unanimous…but not quite.”

As we finished counting Zebra Tops (Keen felt sorry for some and rescued them from seastars. But echinoderms need to eat too!) we noticed a huge white and grey Pelican riding thermals rising from the hot exposed rock. Wind gusted hard over the island’s top, and the Pelican would surf thermals for a minute before lowering itself into the gusts and riding in a wide crescent out over the ocean. Seeming without a care in the world, it would then coast over the island and catch another thermal.

“Do you think it’s having fun?” said Keen.

“Looks like it,” I said.

We watched the seabird, a proud example of Australian Pelican (Pelecanus conspicillatus.) Its wings wobbled as it hovered on the thermal. Then – it dropped and swooped out over the waves. In moments it was back.

“It’s not looking for food,” I said, as the seabird hung suspended in the air. “And that does look like fun.”

Keen sighed. “I wish I had wings.”

We spent a while chasing gobies in rock pools, and then we were hungry, which meant it was time to go. On the return hike to the car we walked past the mouth of Lake Illawarra. The tide was starting to rise and the foreshore was wet and dark. It also appeared to be moving.

“Hey, crabs!” I had ditched my gear and was dancing amongst crabs in a second. “Look, Keen, soldier crabs!”

All across the foreshore, an army of perhaps ten thousand soldier crabs were digging out new holes above the waterline. In amongst the waves of smaller Mictyris platycheles were large Light-Blue Soldier Crabs (Mictyris longicarpus) looking like horses amongst foot soldiers. They were oblivious to us. By the drove they kept on digging, while others processed sand through their mouthparts, restlessly surging across the boundary of surf and sand.

Salty poked his nose into a crab’s back, and watched baffled as the crab burrowed in a spiral into the wet sand. In seconds it was up again, scuttling for higher ground. From the water a Pelican watched on idly, sailing as majestically as a brilliant white yacht. Storm clouds bathed the escarpment beyond.

Keen and I finished the journey to the car in high spirits. The world can be savage, it’s true. But from the snails sampling the finest delicacies of the sea, to the pelican surveying its kingdom, it is also a world of great joy and satisfaction.

Thank you Keen and Salty for a banger of a trip out of Windang Island. Thanks to you two, I’m finally able to present the first five Gong 151 species!

 

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#001 Neptune’s Necklace (Hormosira banksii)

Length: Up to 300 mm

Zone: Low intertidal

Sighted: Day, on rocky substrate in pools and low-lying channels

Locations: Windang Island, common

 

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#027 Zebra Top Snail (Austrocochlea porcata)

Height: Up to 25mm

Zone: Low intertidal

Sighted: Day, on rocky substrate and algae fronds

Locations: Windang Island, common

 

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#078 Light-Blue Soldier Crab (Mictyris longicarpus)

Carapace width: Up to 25mm

Zone: Low intertidal (brackish water)

Sighted: Day, on border of sand and sea

Location: Windang Island (Lake Illawarra entrance), common

 

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#090 Eight-Armed Seastar (Meridiastra calcar)

Arm radius: Up to 50 mm

Zone: Low intertidal

Sighted: Day, on submerged rocks and rocky substrate

Locations: Windang Island, uncommon

 

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# 138 Australian Pelican (Pelecanus conspicillatus)

Wingspan: Up to 2.6 m

Zone: Shore

Sighted: Day, cruising on calm water or riding on thermals.

Locations: Windang Island, uncommon

 

Now it’s up to you. Get out into the Gong and meet some animals!

For the five species listed, we need to find:

  • Which locations they can be found
  • Their numbers in each location
  • Their interactions with other species
  • What they eat
  • What they do all day

You can join Salty and I for a day of discovering sea creatures on Saturday 8th April 2017 at Bellambi Beach. Some snacks will be provided. Bring a bottle of water, your camera, and let’s see what we find.

*Coming soon: Updated link to the 151 Field Guide*

The Gong 151

#001 The Gong 151

Welcome to the world of marine biology!

My name is Anneque “Dangerpus” Machelle. I’m studying to become a marine biologist. This world’s oceans are inhabited by a vast array of fascinating creatures. Some are playful, others could swallow you whole. But what we know about life in the ocean is, well, just a drop in the ocean. Some biologists think over 90% of the life in the ocean remains undiscovered!

That’s why I’ve dedicated my life to studying marine life. Together with my best buddy Salty, I’m on a mission to find 151 marine species in the Gong region. Yet we can’t do it without your help. If you’ve ever dreamed of working with marine animals, discovering new species, and learning incredible things about old ones, The Gong 151 is for you. We need your help to complete this guide and become masters of the ocean.

Each week, Salty and I will explore a new species. Come with us to swim, snorkel, dive and explore to make the ultimate guide to marine life in the Gong region.

Get ready to make amazing discoveries!

For each species, hit the beach and help us find:

  • Distribution
  • Population: common, uncommon, rare or legendary
  • Size
  • Interactions within a  species
  • Interactions with other species (including humans!)
  • And lots and lots of photos

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Links:

Species discovered so far

Area map

Submit data or suggest species

Make your own field notebook DIY

Secrets of the Rock Pools

The quest to uncover the secrets of rock pools continues…

Have you ever wondered exactly what is living in the pretty little rock pools scattering the beach? You hear the crunch of littoral snails underfoot and gaze out upon a veritable starfield of similar creatures: little blue and grey shells in hunkering packs on every available rock, others clustered like refugees at the edges of pools. Now and then you may see the silvery flash of a fish darting for cover. A crab may scuttle under a rock, or bump into another crab and simply stand there, wondering what to do. As you peer deeper, you begin to make out the long red spines of urchins, the mottled blue and green backs of sea stars, and a lonely sea hare drifting amongst pink fronds of coralline algae.

But life in the rock pools is tough. Temperatures are extreme, salinity ranges wildly from hypo to hyper in the space of a rain shower, the waves constantly hammer, hammer, hammer, throwing in new cell mates and dragging out the old, pushing in sand and cold water, offering respite and obscuring shelters in the same breath. Birds circle, and humans flounder clumsily over generations of nerites, and big crabs drive the small crabs to the lesser hunting grounds, and small crabs strip away generations of nerites that the humans couldn’t get to.

Just what are the limitations of life in this war zone? What stops a blenny from living in two inches of water? Is it the hypersalinity? The temperature? Predation from birds? Or is it simply a lack of space? Similarly, why will a green anemone attempt to take root in half a centimetre of water in the midst of a minefield of Pacific oysters?

I wanted to know. And, because no one tried to stop me, I picked 11 rock pools out on a bluff at my local beach to study with the intensity of Charles Darwin observing a barnacle. If you haven’t caught it, you can read my first post of Crab Bluff here, or what the hell, jump right in, the water is warm (-er than ambient temperature.)

High tide at Thirroul Beach averages 1.525 metres above the datum. Low tide averages 0.46 metres above the same datum. Average water level is 0.99 m, meaning anything less altitudinous than 0.99 m is inundated more often than not, and anything above 0.99 m is exposed more often than it is inundated. All pools surveyed on the Bluff remain above the waterline even during high tide.

The Pools

#1 Little Crater

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Volume: 0.24 L

Temperature: Warmer than ambient.

Exposure: This pool could be considered submerged at high tide; water constantly pushes over Big Pool into a water course encompassing Little Crater and Dry Triangle. This stream then flows across the back of the Bluff onto the beach.

As the water drops, less and less water flows over this pool, until the stream narrows and dries to isolate Little Crater. After isolation, water in this pool quickly evaporates, reducing its small volume even further.

Species:

This tiny pool is devoid of sheltering algae. What life there is clusters around the overhanging crater lip.

Molluscs:

  • Little blue periwinkles (Austrolittorina unifasciata)
  • Pyramid periwinkles (Nodilittorina pyramidalis)
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What little there is of Little Crater, with scattered little blue periwinkles.

#2 Dry Triangle

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Volume: 211 L

Temperature: Cooler than ambient up to the point of isolation. Shallow depth means it warms rapidly.

Exposure: As with Little Crater, this pool could be considered submerged at high tide. Water constantly pushes over Big Pool into a water course encompassing Dry Triangle. The pool is shallow with low walls and so the water in it is constantly changing. Outlets are to #3 Left Twin and in the tidal stream running down the back of the Bluff.

As the tide recedes, this pool still receives water, but is changed far less often. Volume is still above that of isolation. Ninety minutes from low tide, the pool is isolated from incoming water. It continues to output a small amount to #3. Eventually the pool is drained completely, and remains dry until it is restored by the rising tide.

Species:

Prone to being drained, there is no macroalgae in this pool.

Molluscs:

  • Pacific oyster (Crassostrea gigas)
  • Striped conniwink (Bembicium nanum)
  • Little blue periwinkle (Austrolittorina unifasciata)
  • Pyramid periwinkle (Nodilittorina pyramidalis)

Crustaceans:

  • Swift-footed crab (Leptograpsus variegatus)

 

#3 Left Twin

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Volume: 105 L

Temperature: Offers sustained respite from high ambient temperatures.

Exposure: At high tide this pool receives regular water from the tidal stream. #2 runs into this pool even after the tide has receded. Additional water is provided by large waves. Left Twin outputs into Right Twin, which then flows down the back of the Bluff. As the tide reaches average height, inlets and outlets to this pool stabilise, leaving it isolated.

Species:

On original observation, this pool was deep with a rocky substrate, harbouring numerous small algae. In early December a storm pushed sand into the pool, halving its volume and obscuring most of the algae. Young crabs still find it a convenient hiding spot on their hunting ventures.

Molluscs:

  • Black nerite (Nerita atramentosa or N. melanotragus … orange and black operculum suggests melanotragus)
  • Pacific oyster (Crassostrea gigas)
  • Pyramid periwinkle (Nodilittorina pyramidalis)
  • Striped conniwink (Bembicium nanum)
  • Little blue periwinkle (Austrolittorina unifasciata)

Crustaceans:

  • Swift-footed crab (Leptograpsus variegatus)

Annelids:

  • Spirorbid worms (Spirorbis sp.)
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Orange and black operculum on Nerite sp. Note cute spirorbid worm spirals on shell.

#4 Smoking Gun

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Volume: 85 L

Temperature: Warms rapidly after isolation.

Exposure: Inundated at high tide from backwash across the Bluff, this pool is otherwise relatively higher than the rest and so protected from most inlets. Still, rough wave action sees a total water change of this pool at least once per minute.

Two hours after high tide, no regular inlets remain, and there is only one small outlet to Dry Triangle.

Species:

While shallow and readily overlooked, this pool contains a good deal of encrusting and stringy algae, and supports a surprising amount of life.

Molluscs:

  • Black nerite (Nerita sp.)
  • Little blue periwinkle (Austrolittorina unifasciata)
  • Pyramid periwinkle (Nodilittorina pyramidalis)
  • Striped conniwink (Bembicium nanum)
  • Zebra winkle (Austrocochlea porcata)
  • Variegated limpet (Cellana tramoserica)
  • Flamed limpet (Notoacmea flammea)
  • Pacific oyster (Crassostrea gigas)

Crustaceans:

  • Swift-footed crab (Leptograpsus variegatus)

Annelids:

  • Spirorbid worm (Spirorbis sp.)

 

#5 High Triangle

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Volume: 99 L

Temperature: With no spray to refresh it, temps reach ambient and above.

Exposure: High Triangle is the most isolated pool tested. Its west banks are dry even at the peak of high tide; it’s a safe place to stand and not be doused. Water, even spray, does not reach is regularly. Silty sediment on the pool’s bottom and persistent crab skeletons suggest only in rough weather and rain does this pool receive new water.

Species:

Any algae in this pool is on the micro scale. A few hardy periwinkles are all that survive here. On hot days they clustered above the pool’s edges. The empty white carapaces of crabs drift along the silty bottom.

Molluscs:

  • Little blue periwinkle (Austrolittorina unifasciata)
  • Pyramid periwinkle (Nodilittorina pyramidalis)

 

#6 Big Pool

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Volume: 8998 L

Temperature: Cooler than ocean – possibly due to high evaporation levels from Big Pool.

Exposure: Hammered and inundated by violent wave action at high tide, this huge pool has outlets into the ocean on its east side and a tidal stream on its west side. Rock forms a natural funnel at this point of the Bluff and white water jets dramatically over Big Pool.

Two hours after high tide, far less is received and output. The water level remains about 5 cm above the pool’s algae line. On Big Pool’s surface, the only hint of its violent past are in the foam and shredded bladderwrack.

Species:

Big Pool is home to all sorts of interesting creatures washed in from the sea. Large amounts of coralline algae, sand and rocky crevices provide a multitude of lifestyle options, and creatures here are both visitors and regulars.

Arthropods:

  • Honeycomb barnacle (Chamaesipho tasmanica)
  • Rosy barnacle (Tesseropora rosea)

Molluscs:

  • Warrener (Turbo undulatus)
  • Mulberry whelk (Morula marginalba)
  • Black nerite (Nerita sp.)
  • Tent shell (Astralium tentoformis)
  • Zebra winkle (Austrocochlea porcata)
  • Striped conniwink (Bembicium nanum)
  • Little blue periwinkle (Austrolittorina unifasciata)
  • Variegated limpet (Cellana tramoserica)
  • Sea hare (Aplysia sp.)

Anemones:

  • Green anemone (Aulactinia veratra)
  • Shellgrit anemone (Oulactis muscosa)
  • Pacific oyster (Crassostrea gigas)

Echinoderms:

  • Tuberculate urchin (Heliocidaris tuberculata)
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Big Pool at high tide. Ride those waves!

#7 Stream Pool

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Volume: 9.6 L

Temperature: Struggles to remain cool after isolation.

Exposure: Although this pool is high above the water, waves channelled against the Bluff jet into it, changing its volume several times a minute. It outlets to Big Pool.

Two hours after high tide, Stream Pool receives far less water and is not inundated, though it still receives regular small doses from wave action.

Species:

This narrow crevice is thickly grown with Pacific oysters. A few very small urchins also hide out amongst the regular smattering of littoral snails.

Molluscs:

  • Pacific oyster (Crassostrea gigas)
  • Black nerite (Nerita sp.)
  • Zebra winkle (Austrocochlea porcata)
  • Striped conniwink (Bembicium nanum)
  • Little blue periwinkle (Austrolittorina unifasciata)
  • Variegated limpet (Cellana tramoserica)

Anemones:

  • Shellgrit anemone (Oulactis muscosa)
  • Green anemone (Aulactinia veratra)

 

5_anemone

Shellgrit anemone, full of sand and grit.

#8 Elephant Pool

8

Volume: 162 L

Temperature: Pool temp measured in the afternoon was cooler than the ocean temp measured in the morning. Could be due to evaporation, or cooler waters pushing onto the beach after initial ocean temperature was measured.

Exposure: Elephant Pool is the most exposed of any pool tested. It receives intense wave action during high tide, with water constantly pouring in and out of this deep pot of a pool, often violently.

Even at low tide, this pool continues to receive water, and is always at capacity. Its only outlet is the ocean.

Species:

Generous algae grows provide shelter and food for the curious inhabitants of this pool, all of whom seem to be regulars. In particular, a pair of large elephant snails hide amongst the sea grass at the bottom, while crabs and urchins tuck themselves into a deep crevice.

Anemones:

  • Green anemone (Aulactinia veratra)

Arthropods:

  • Swift-footed crab (Leptograpsus variegatus)

Molluscs:

  • Elephant snail (Scutus antipodes)
  • Zebra winkle (Austrocochlea porcata)
  • Black nerite (Nerita sp.)
  • Striped conniwink (Bembicium nanum)
  • Little blue periwinkle (Austrolittorina unifasciata)
  • Variegated limpet (Cellana tramoserica)

Echinoderms:

  • Tuberculate urchin (Heliocidaris tuberculata)

 

#9 Big Crater

9

Volume: 229 L

Temperature: Is able to resist some heat from the sun after isolation. This measurement, taken at nearly low tide, suggests the pool would reach ambient temperature before regular cool spray was restored.

Exposure: Regularly sprayed in high tide, where it sits above capacity with only a small outlet draining to the ocean. This pool’s depth and sides give it some protection from wave action. Pool #10, High Half-Crater, also flows into Big Crater.

Two hours after high tide, this pool is close to its isolated volume. It receives only spray, and retains a small volume outlet to the ocean.

Species:

The deep bowl of this pool is a nursery for snail eggs. Young crabs hang out at this pool in the manner of kids at a skate park, having been pushed back from the Bluff by their old folks.

Arthropods:

  • Swift-footed crab (Leptograpsus variegatus)

Molluscs:

  • Little blue periwinkle (Austrolittorina unifasciata)
  • Black nerite (Nerita sp.)
  • Zebra winkle (Austrocochlea porcata)
  • Pacific oyster (Crassostrea gigas)
20161110_131018
A curious Zebra winkle.

#10 High Half-Crater

10

Volume: 68 L

Temperature: Approaching ambient after isolation.

Exposure: Despite this pool’s proximity to the ocean, it is readily isolated by its height and orientation in the rocks. It receives spray only in high tides and rough weather, and more regular inlets across the Bluff from the back of #11, Neptune’s Crater. Here large waves increase #10’s volume and change its water regularly.

Two hours after high tide, the pool’s outlets to #9 Big Crater have subsided, and it receives little new water.

Species:

A small Neptune’s necklace grows here; otherwise algae is microscopic and the pool is superficially barren.

Molluscs:

  • Little blue periwinkle (Austrolittorina unifasciata)
  • Zebra winkle (Austrocochlea porcata)
  • Black nerite (Nerita sp.)

 

#11 Neptune’s Crater

11

Volume: 4 L

Temperature: While small, this pool’s proximity to the ocean keeps it cool. The shade from the many Neptune’s necklaces might also help.

Exposure: This pool rests in a wet site near the ocean edge of the Bluff, where it is doused several times a minute even in receding tides. As tide recedes, waves tend to strike the Bluff wall and then shower down on this pool. Action is intense and disruptive but not violent.

Two hours after high tide, the outlets to #10 and the ocean have subsided, and the inlets from waves are less regular; perhaps not even once a minute for a decent douse of spray.

Species:

Neptune’s necklace grows thickly here, fronds obscuring the surface of the small pool and providing plenty of cover for its inhabitants.

Anemones:

  • Green anemone (Aulactinia veratra)

Molluscs:

  • Black nerite (Nerita sp.)
  • Zebra winkle (Austrocochlea porcata)
  • Striped conniwink (Bembicium nanum)
  • Pacific oyster (Crassostrea gigas)

Crustaceans:

  • Swift-footed crab (Leptograpsus variegatus)

Arthropods:

  • Isopod ~

Annelids:

  • Spirorbid worm (Spirorbis sp.)

 

Conclusions:

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Regular inlets do a lot for a pool. Those pools receiving regular wave and spray action are closer in temperature to the ocean, while those more isolated at the back of the Bluff or higher up can be even hotter than the air temperature.

This means one, that the degree of isolation is a vital component of temperature. Two, that isolation determines what species may survive and flourish in a pool. Also interesting to note is juvenile crabs seemingly pushed back away from the edge of the Bluff, itself a wall of good hiding places, to hunt in the landward pools.

  • Are these young crabs displaced from fertile hunting grounds by larger crabs?
  • Why are larger periwinkles (Austrolittorina unifasciata and Nodilittorina pyramidalis) found in the hottest and most isolated pools – is this to prevent competition with their young?
  • What role is played by salinity and water quality in determining species variation and distribution in the pools?
  • The ocean provides a stable temperature: at night as well as day. How does pool temp behave at night? More day testing is also needed for better results.
  • A cooler daytime pool seems to provide better species diversity, as does accessibility to the ocean. Is this actually because of more stable temperatures, or due to the likelihood of creatures being pushed into the pool by waves?
  • What is the role of substrate – rock, sand, algae – in keeping a “local” population in a pool?

Join us next time for more rock pool action on Danger Ball Z!