I recently illustrated The Hidden Universe by Alexandre Antonelli.  This image of the zonation of a rocky shore ecosystem was one of the illustrations.

The timing of this illustration was an extraordinary stroke of luck.  Alex wanted a drawing that shows the different animals and seaweeds on rocky shores.  These plants and animals grow in different zones going up the shoreline.  The factors that cause these differences (also known as zonation) include physical forces such as salt levels, dehydration, physical damage from the waves.  There are also biological, or biotic factors at play, such as predation, competition for food, and competition for space.

How do I know?  Well, the week I started this project, I went on a fabulous weekend course.  All about Discovering life on rocky shores!  The course is hands on, so I took tons of photos and copious notes.  I sketched barnacle speciation, and shrieked with delight at Porcelain crabs.  I even saw my first blue-ray limpet.

My very poor photo of Blue-ray limpets

So when this illustration turned up, I was exceptionally well equipped.  Here’s the pencil rough, which I annotated so that it made a bit more sense.

Annotated rocky shores illustration

And here’s the final illustration.  Inking it up was an absolute joy, although it took a great deal longer than I would have liked!

Rocky shore line ecosystem zonation of species

In this blog, there are so many animals and plants discussed, that I’m taking the decision not to give every scientific name.  It’s just be a jumble of italicised Latin if I did. Apologies in advance to the purists among you!

Rocky shores: Splash zone

The very top of a shore is known as the splash zone.

Sea plantain Plantago maritima

The top zone has very little growing there except for the odd brave plant and Xanthora lichen.  you might get tough periwinkles, but the combination of dry and salty splashing is lethal to most organisms.

Plants that do survive here have amazing adaptations to allow them to tackle the salt.  They’re known as Halophytes, and I wrote a blog on them a while back.

Animal wise, shore flies visit, and slaters (relatives of woodlice) crawl about.  You get limpets, clinging on and anchoring themselves to the exact same spot for most of their lives.

Thrift Armeria maritima

Rocky shore Intertidal zone

Lower down, you’ve got the high tide or intertidal zone.  Animals and plants living here have to handle massive fluctuations in temperature and being out of water for 12 plus hours every day.  the crashing waves cause physical damage.  On the plus side, it’s so hard to survive here that there’s not a lot of competition.

Limpet (with mating barnacles on the side)

Chitons, whelks, winkles, and barnacles live here alongside hardy sea anemones and the toughest of all seaweeds, channelled wrack.

The whelks travel around when the tide is in, predating on mussels and other bivalves by drilling a hole through their shells and sucking out the meat.

Detail of the intertidal showing chitons, whelks, and a sea anemone

Rocky shore Mid tidal

This stretch is exposed for shorter times between tides.  There’s less wave action as a lot of the time the area is submerged.  You need to handle the changes in temperature and salt, but it’s a less extreme environment than the upper tidal or splash zone.

Mid tidal zone: Crab and Breadcrumb sponge with coral weed

More animals and plants live here.  Tons of shells like top-shells, barnacles, Perwinkles, and mussels, hang out amidst the seaweeds.   Different species of top shell and winkle favour different areas of the rocky shore.

Topshell

You can tell Periwinkle and Top-shell species apart by the shape of their operculum, the door at the bottom of their shells.  In top-shells this is invariably round.  Periwinkle operculum are tear shaped.

Detail of the mid tidal: Smooth periwinkle, Pin cushion starfish, mussels and bladderwrack

There are more sea anemones, and visiting shore crabs.  Sponges and starfish abound.

The drawback is that there are more animals surviving here, so there’s more competition for space.  Predation kicks in too, with the starfish feeding on mussels, flat periwinkles chewing seaweeds, and whelks feeding on bi-vales.  These are the biotic factors starting to kick in.

If space does become free, it’ll quickly be re-colonised.

Rocky shore Mid tidal: Barnacles

Barnacles have a good system; they can grow on top of other shellfish, and can extend their filtering arms from this substrate.  Barnacles are actually crustaceans, related to crabs and shrimp.

Free living barnacle larva land on intertidal rocks where their heads split and they establish themselves for a stationary life.  They filter food particles form the sea with their legs, which are adapted to work as sieves.

The problem with living on a shellfish is that if and when that shell dies, you get plunged to the floor where it’s every likely you will die.

Blue mussels Mytilus edulis with barnacles and bladder wrack

Rocky shore Mid tidal: Seaweeds

Seaweeds thriving in the mid-tidal zone are bladder-wrack, egg-wrack, toothed wrack, spiral wrack.  These grow at very specific heights along the shore, depending on their adaptations and tolerance to heat and dry conditions.

Bladderwrack Fucus versicolor

Rocky shore Lower tidal zone: Species

The lower tidal zone is altogether more comfortable.  Exposure to air, desiccation and the heat of the sun is far less frequent.  In fact, it only happens at low tides.  The waves are less problematic.

The bladder wracks give way to kelp.  Brown algal wracks are unpalatable to most animals.  In the UK, it’s only the Flat periwinkle that can handle eating it.  Oar weed and sugar kelp are an entirely different prospect and are clearly much easier to eat.  If you are lucky and look closely at low tide, you might see the tiny and stunning Blue-ray limpets grazing on a blade of Oar weed.

Edible crab, sea urchins, tube worms, star fish, brittle stars, more sea anemones, sea lemons and nudibranch hang out here, along with bivalves.

You also see Porcelain crab with their strange, squashed bodies.  Decorator crab, often festooned with bits of seaweed can be seen too.  Hermit crabs spend much of their time in this zone.

Lower tidal zone: Spiny Decorator crab, Sugar kelp, and blue ray limpets

Rocky shore Lower tidal zone: Biotic factors

Flip side? Biotic (rather than physical) factors. Far more predation.  And intense competition for space and things to eat.  Of course, with the physical factors being so much easier to handle, many organisms will migrate from this zone to the Mid tidal once the sea covers them.  There they can eat and predate on other species before retuning to the safety of the lower shore before the tide exposes them again.

Rocky shore Lower tidal zone

You even get sun-stars.

The biological factors such as predation and competition are extreme here.  Predation is fierce.  And competition for space in intense.  Yes, you don’t get smashed up by waves or dried out twelve hours a day.  But you do get eaten, and may well find it impossible to get a foothold in such a heavily populated zone.

Seahorse family groups

Some seahorse and pipefish species will spend time in this zone, although drying out is a real problem for them, so they tend to stay in the sub littoral.

Rocky shore: Sub littoral

Below the lower tidal zone is the sub littoral.  This area of the shore is never exposed to the air, not even at the lowest of tides.  It tends not to figure in rocky shore zonation as it’s more like shallow ocean than the shore.  Fish, crabs, lobster, kelp forests all abound here.

American lobster Homarus americanus

Complicating factors: Rockpools

Rockpools are vital for lots of these organisms, although they can suffer from enormous halinity and temperature fluctuations.  But to the aspiring rocky shore ecologist, rock pools can be confusing,  As they remain wet, you get organisms living there that should not be seen in the Upper tidal zone, or mid tidal areas of the beach.  Luckily, this is catered for by ecologists who examine rock pool life as a subset of the larger ecosystem.

The illustration above was done many years ago.  I now know that brittlestar (lower littoral specialists) and razor clams (sand living specialists) are unlikely to appear in any European rockpool.  You live and you learn.

Complicating factors: Exposure

It should also be remembered that the exposure of a rocky shoreline will have an enormous effect on the life there.  High exposure means it’s even harder to exist in the splash zone and Upper tidal.  More sheltered shores offer an easier existence.

Conclusion

This is truly a whistle-stop tour of the zonation of the rocky shoreline.  I have no doubt this blog is peppered with mistakes.  The FSC course tutor, John Archer Thompson probably has his head in his hands as he reads my version of his wonderful teaching.

As an excellent launch pad to much more on this subject, thanks to John, please check out his FSC rocky shore pages.

The post Rocky shore ecosystem illustration appeared first on Lizzie Harper.

I’m very fond of these plants; that warm, mauve blue coupled with the glossy green leaves makes for a pretty garden plant.  It was a pleasure to spend time comparing the Lesser periwinkle, Vinca minor (a problematic invasive species in Sweden) with the Greater periwinkle, Vinca major.

Another appealing aspect of the Periwinkle species is that telling these two species apart isn’t nearly as tricky as some plants can be (see Comparing Hogweed Heracleum species, and Comparing Goldenrod species  for a taste of what I mean!)

Size

Lesser periwinkle is, as the name suggests, smaller than Greater periwinkle.  Although both have a spreading growth pattern, and put out vegetative stems, all aspects of the Lesser are a little smaller than that of Greater.  In both cases, these trailing stems help the plant colonise new areas, and can form pretty thick ground cover in ideal conditions.  This isn’t surprising, the trailing stems can be up to a meter long!

Lesser periwinkle, V. minor

Lesser periwinkle has one, (rarely two) flowers at each axil.  Greater periwinkle has up to 4.

Leaves

Lesser periwinkle leaves are around 4cm long, whilst those of the Greater periwinkle are almost twice the length, averaging 6cm length.  There’s a clear difference in leaf shape too.  Lesser periwinkle has elliptical leaves with a pointed tip.

Working on illustrating leaves of V. minor

Greater periwinkle leaves are heart-shaped (or cordate; for more on terminology of leaf shape check out my earlier blog).

Lesser vs Greater periwinkle leaves

The petiole, or leaf stalk is noticeably longer in Greater, up to 20mm.  Lesser periwinkle leaves lie far closer to the main stem, with petioles no longer than 3mm.

V. minor plant and illustration showing small leaves and short petioles

Finally, the leaves of the Greater periwinkle have tiny hairs at their base.  These are absent in the Lesser periwinkle.  I did spot these hairs, but it took some doing, and was an instant diagnostic.

I did have the challenge of only having a variegated species of Vinca minor to work with, disregarding the paler blotches can be quite tricky.

Stems

The stems of both plants look similar, being hairless and green, or flushed crimson.  However, Lesser periwinkle stems can root along their length, while Greater periwinkle tend only to root at the stem tips.

Lesser periwinkle showing roots along stem length (not only at tip)

Flowers

Lesser periwinkle flowers are smaller than those of its cousin.  They average 2.5cm across, whereas those of Greater periwinkle are around 5cm wide.  Both periwinkle species have five slightly unequal petals.

Lesser periwinkle flowers

There’s a difference in petal colour, too.  V. minor flowers are a paler and pinker blue, sometimes almost a lilac hue.  V. major flowers are a darker blue-purple.

Lesser vs Greater periwinkle flowers

I was incredibly lucky to find both periwinkle species in flower as I illustrated them, it would have been hard to get the colours right without the flowers right there.  The V. major flower was noticeably smaller than those blooming earlier in the summer, but as long as you’re aware of these seasonal differences you can compensate.

Obviously, it’s vital to keep specimens fresh as you draw them.  I rather enjoy the classy tone the Babycham glass gave to proceedings…

Classy reference

Calyx

The calyx is the outermost part of a flower, which is frequently green and often divided into sepals.  In the periwinkles, it helps differentiate between the species.

V. minor has a smaller calyx (0.5cm long) which is hairless, and has blunt tips.

Calyx of V. major are twice the size, and have pointy tips.  They are fringed with hairs which are absent in the Lesser periwinkle calyx.

Calyx of Lesser periwinkle vs Greater periwinkle

I’m not lying when I say spotting the differences in hair distribution, even under my dissecting microscope was a challenge.  But then I only had one or two calyx from each species to examine.  Looking for such distinctions is always easier when there’s a glut of fresh material to examine!

Conclusion

Before looking at these plants in detail, I didn’t even realise there were two species of periwinkle!  It’s lucky that telling them apart was so straight-forward, and that I managed to get my hands of live reference before autumn closed in.

So if you want to know if that plant in your garden is Lesser or Greater; look our for leaf shape and stalk length, flower size and colour, and get that hand lens out on the calyxes.

This unframed original illustration is available to buy for £125, if you’re interested do drop me a line on info@lizzieharper.co.uk.

The post Comparing Periwinkle Species appeared first on Lizzie Harper.

I thought I’d do a quick step by step on how to go about mixing the colours, and illustrating this flower, not least because blue flowers pose their own challenges.

Pencil rough

I draw direct onto hot press watercolour paper, which has a very smooth surface.  This time I’m using Arches hot press.  I like to use mechanical pencils like the Pentel P205, with H or HB leads.  I use a soft eraser; those made by Factis are good.

First, draw up the flower.  Think about what shape you’d get if you drew a circle from the outside edges of the five petals.  It’d be more or less circular.  Bear this in mind as you plot the petals, but remember to draw the individual shape and folds of each one.

Draw the centre of the flower and note the pentagon with the stamens and sepal at the centre,  There are small triangles of blue tucked in there too.

When you’re happy with the pencil drawing, you can move onto mixing your paint.

Mixing the Blue

Rather surprisingly, the colour of this flower is really easy to mix.  I just mixed French ultramarine with Cobalt violet, and made a paler tint by diluting it with water.  I favour Winsor and Newton watercolour pans, and always use their Series 7 sable brushes (in this case a no. 1 size).

Avoid trying to make a watercolour mix paler by adding white; this changes the colour massively and makes it thick, non-transparent, and heavy.  Always dilute it with clean water instead.

Laying down the colour

I build up the colour with lots of tiny lines, following the line of growth of the petals.  There’s a clear gradation on each petal, from pale at the centre out to a darker mauve on the petal edges.  Each line painted echoes this.

The edge of each petal is marginally paler than the body of the petal.  Remember to leave these edges as white paper.

Try to keep the ends of your brush strokes to the petal edges, this is where the colour is deepest.

First top wash

Using the same mix or Cobalt violet and French ultramarine, dilute the colour with clear water.  Paint this over the lower half of each petal, leaving it really wet on the page.  Try to emphasize the gradation from white centre to purple edges by being subtle with this top wash.  It won’t lift all the lines you’ve painted, but will soften them, and add depth to the blue of the flower.

Be patient, and let the paint dry fully.  You can use a hair dryer or a fan heater to speed up the process if you’d like.

Second top wash

Once fully dry, dilute your purple-blue colour further (with clean water).  Apply this over the entire flower, except for the very centre.  Cover up those white petal margins with the pale wash, and the areas closer to the middle of the flower.  Lift off surplus paint with a twist of loo roll or tissue to make sure the centre of the flower is still significantly paler than the petals.

It goes without saying that everything you paint and draw needs to be informed by the flower in front of you.  It’s so much easier to illustrate something right there, rather than a photo! (Saying that, sometimes you need to use photo reference.  For more on how to do this, check out my blog.)

Allow this wash to dry completely.

Painting the centre of the flower

The middle of the periwinkle is a clear pentagon.  Inside the corolla tube, you can see five little blue-purple triangles.  Paint these in, paying close attention to their size and shape, and how they’re paler as you move further from the petals.

You’ll notice shadow within the pentagon.  Mix a neutral colour to plot in these areas.  I used Pthalo green and Cadmium orange.  (If you mix colours which are more or less opposite on the colour wheel, they tend to make wonderful neutral tints.)

I diluted this thoroughly with water, then plotted in the shadow; darker at the top of the corolla tube.

Finally, it’s time to paint the centre of the flower, the pistil and stamens.  This is a pale yellow colour.

I used Naples yellow with a touch of cadmium yellow for this.  Leave a highlight in the centre, then pop an incredibly light yellow tint on top of the whole of this tiny yellow area.  You might see a bit of pale yellow coming up the corolla tube; plot this in too, being very careful not to make it too obvious.

Finishing up

Double check your illustration against the flower.  Are the edges of the petals dark enough?  Is the centre pale enough?  Have your washes dried smoothly or left unsightly edges?  In my case, the wet washes had left a tide mark on two of the petals. I eased this effect with a dry-ish brush, used in tiny little circles.  It lifts enough of the colour to remove the stark line.

Finished.  This is a quick sketch, and I didn’t draw in leaves, the pink-flushed stem, or any flowers showing their beautiful shape from the side.  However, it was a real pleasure to work on, and despite being such lovely and delicate shade of blue, getting a colour match was really straight-forward.

For a brief guide to this step by step, all on one handy sheet, please visit my Pinterest site.  Thanks.

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