Colour Underwater

September 2nd, 2019

The current storms indicate that summer is passing into autumn, and at Lancashire MCS we are starting to think about our winter lectures; which we hope will bring some interest into the darker months for you! Each year those of us on the committee dive deep into our store of knowledge to bring some element of the underwater world to life…

A number of years ago the subject of underwater colour was brought up, and I had thought this would be an interesting subject (though I did not know enough about it to present a talk;-) Over the years since then I have been gathering some relevant publications, and thought that perhaps this year I would try to bring them together.

The subject rather quickly expanded, as considerations of physics (transmission of light underwater), incidental colour (plants cannot help but be green – though seaweeds often are not!) and behaviour (how animals manipulate colour for communication and camouflage) all have an important part to play. When we look at how organisms produce colour, we get a glimpse into deep-time; the genes for green fluorescent protein (or their analogues) are present in all metazoans, suggesting colour may have been important to the Ediacaran biota 540 MYA.

Is red a colour?

Our eyes have adapted to life above water, but reds and oranges are strongly absorbed in seawater, leaving a monochromatic green-blue world. A lot of sea life is red, however, and some deep sea fish generate red light. We might, therefore, suggest that the colour red is significant even if it is only visible up close: At distance red light is absorbed, so anything red appears grey or black. If you only want to advertise locally, and don’t want to attract the attention of the big fish lurking in the gloom, red might be the most important colour!

Two photographs of brittlestars on kelp. the main image is taken from 5m in natural light, and they appear monochrome. The inset is taken at a distance of 30cm with a white strobe.
Two photographs of brittlestars on kelp. the main image is taken at a distance of 5m, and they appear monochrome. The inset below is taken at a distance of 30cm. To the best of my knowledge the colours displayed do not have any importance for the brittlestars concerned.

A comparison with other land animals suggests that colour perception in different species is likely to be very different to our own. Indeed, when age, visual defects, ill-health and genetics are taken into account, I might argue that colour is a personal experience, with even crude descriptions of ‘blue’ or ‘yellow’ meaning quite different things to each of us. (Web design in my day job, and it is quite important to ensure that text/background colour combinations are likely to be legible to readers!)

When we look at marine life, we see species with true colour perception ‘superpowers’. The most studied of these is that of the mantis shrimp – with twenty visual receptor types – twelve for colour (we have three), six for polarisation (we cannot detect this at all) and two for luminance (we have one). This suggests that the oceans are far from monochromatic, and there is hope for my talk…

See Unconventional colour vision by Justin Marshall and Kentaro Arikawa in Current Biology 24.24 (2014), R1150-R1154, for a primer in colour vision, and animal superpowers!

Barry Kaye

We are currently finalising our winter programme of lectures, and hope to have some external speakers this year alongside the ‘old guard’. please join us if you can – our Newsletter will keep you up-to-date.

Posted in Marine science update, MCS talks, Science

Risk and reward – the Roa Island shore walk 2019

September 2nd, 2019
Sand mason worms against the sunset at Roa, August 31 2019. By Barry

The drive up to Roa on Saturday was not very promising, with periods of torrential rain it was no surprise that only a few made the effort… In the event, however, other than a strong wind, the evening was very pleasant. We spent the first little while, however, spelling one of the lifeboat crew watching some kayakers to make sure they reached Piel Island safely!

Due to the wind we spent a little more time than usual to the West of the lifeboat jetty. The mud flats here are the home of a large number of sand mason worms (pictured above), and scattered with common starfish, which have been stranded by the tide as they hunt for cockles in the mud. Starfish have a hydrostatic skeleton, so are completely incapacitated in the absence of water. It is clear from the sad, deflated bodies, that a few do not survive exposure, but for many the chance of a meal must be worth the risk…

The visit also allowed me to take a plankton sample, which looks very different to the one I took on the dive in July, when there were no phytoplankton, and few zooplankton. The rougher weather recently may have helped spur some activity, as the sample from Saturday had high concentrations of phytoplankton, and lots of zooplankton and larvae, to recolonise the Bay. A few weeks can make a massive difference!

Barry Kaye

Posted in Marine science update, Shore walks

Invisible World: marine primary production

February 5th, 2019

Man and animals are in reality vehicles and conduits of food, tombs of animals, hostels of Death, coverings that consume, deriving life by the death of others. Leonardo da Vinci

Plants are rather different – quietly converting sunlight into the food we need to survive; the shepherd with his grazing flock is the subject of a painting, the meadow, a beaucolic backdrop. In the worlds oceans, however, the plants that form the meadow are microscopic – completely invisible to the naked eye. Indeed, for most of the 20th century, the main players remained elusive even to the best optical microscopes!

Over the last decade or so satellite imagery, coupled to unmanned submersibles, have begun to reveal the true extent of marine ‘plant life’. We find a complex, dynamic pattern of blooms, and rapid disappearances keyed to the seasons, currents and climate. Alongside this, genetics has begun to unravel the complexities of the interrelationships between the different groups of marine plants – and animals…

Join us on Wednesday 13th February between⋅19:30 and 21:00 at the Gregson Centre, 33 – 35 Moor Gate, Lancaster LA1 3PY for a personal look at some of the recent research in this area.
Admission £3.00, everybody welcome!

Posted in Events, Marine science update, MCS talks, Science

Dark and dull? Underwater wildlife photography in British waters

November 27th, 2018

Tunicates and worms by Barry Kaye

At our next meeting, members of the group will take personal views on the subject of photography around UK coastline. This will include a look at the photographic equipment they use, and the challenges they face in getting a ‘good’ photograph. Main speakers: Gordon Fletcher (film), Lewis Bambury (digital), Jo Kaye (macro).

Dark and dull? Underwater wildlife photography in British waters (PDF 117kB)
Wednesday, 12th December, 19:30 – 21:00 at the Gregson Centre, 33 – 35 Moor Gate, Lancaster LA1 3PY.
Admission £3.00, everybody welcome!

Please note, we do not have a meeting in January 2019, our first meeting of the New Year wil be in February, the remainder of our winter lecture programme is available in the PDF linked below:

MCS winter lectures 2018 (PDF format 82kB)

Posted in Marine science update, MCS talks

Life in Liverpool docks

April 7th, 2018

Review of ‘What’s up Dock?’, a talk presented by Wendy Northway (MCS North West England Seasearch Coordinator) on 14th March 2018.

While Liverpool’s pre-eminence as a maritime centre in the North West is undisputed today, it was only in 1751, with the construction of the world’s first commercial wet dock that she cemented her call to that title. Previously the most important port in the area was Chester, a position the city had held since Roman times.

The first wet docks allowed ships to be unloaded in a day and a half, significantly undercutting the older practice of unloading cargo to smaller boats at sea for transfer to shore – a process that could take two weeks on good weather. This gave the port a massive commercial advantage, and soon the docks were over-subscribed, leading to the rapid construction of new, larger facilities, which were also required as the expansion of trade with the industrial revolution lead to ever larger vessels…

Liverpool's Albert Dock with the Liver Building in the background. Photo B Kaye
Above: Liverpool’s Albert Dock (with the Liver Building in the background) has been cleaned up and is now a major tourist destination, housing Tate Liverpool and a number of museums. Diving in the docks is now strictly controlled. Photo B. Kaye

As each new dock was built, unseen and rather unheralded, we also built a new marine habitat, and it is these that were the subject of the talk What’s up Dock? by Wendy Northway (MCS North West England Seasearch Coordinator) to the group on 14th March 2018. The docks are no longer used commercially (having closed in 1972), but are actively managed leisure spaces. Water from the river Mersey is not used, as it is too polluted, instead the docks are topped up from the Irish sea on high water springs, giving a salinity in the range 24‰ to 28‰. The exchange of water with the Irish Sea allows for migration of marine wildlife between the Irish Sea and the docks, which have as a consequence become colonised by a fairly select group of organisms.

Mussels and algae colonising a discarded bicycle. Photo (c) BrokenDiver
Above: An old bicycle thrown into the dock has been colonised by mussels and algae. Photo © BrokenDiver.

In 1988 the docks were colonised by up to 1000 mussel spat per square meter. The absence of common starfish in the docks have allowed very large population densities of mussels to be established, and larger individuals have grown too big to have any natural predators. The mussels have been calculated to filter the entire of the docks water every four days, and are probably vital to maintaining water quality. Other filter feeders include bryozoans, sponges and tunicates, while cockles have colonised the soft, muddy bottom of the docks.

Black goby amidst mussels, bryozoans and sea squirts in Liverpool docks. Photo (c) Catherine Gras
Black goby amidst mussels, colonial hydroids and sea squirts (Ciona and Ascidiella) in Liverpool docks. © Catherine Gras

The modern docks are home to a thriving marine community, including a number of fish and crustaceans. I was, however, particularly interested to hear that the seasearch divers had confirmed the presence of an introduction from the southern hemisphere, the worm Ficopomatus enigmaticus in the Collingwood Dock. This species may have been introduced on the bottoms of ships or as larvae in bilge water. Unfortunately we do not know if this is a relatively modern introduction on pleasure craft, or a relict from the Liverpool port’s trading days.

Ficopomatus enigmaticus, an Austrolian introduction. Photo Wendy Northway (c) PhoebeSparke
Above: The characteristic pagoda shape of the tubes created by the worm Ficopomatus enigmaticus, an Australian introduction. Photo Wendy Northway © PhoebeSparke

NOTES: Ficopomatus has become a nuicance in many areas it has colonised, producing dense aggregations that can interfere with dock gates and other marine/estuarine structures, though at high densities in docks may help clear the water of particulates, and improve bottom biodiversity (JNCC report linked below). In some places it forms large reef structures in shallow brackish water. Needing a temperature above 18°C to breed, it may not be as invasive in our local open waters, but has been recorded in the docks at Barrow, so we should be looking out for it in the Bay! More information on Ficopomatus enigmaticus at ‘The Exotics Guide‘ and JNCC.

Posted in Marine science update, MCS talks

World Ocean Day at Freeport Fleetwood

June 24th, 2016

Thanks to everybody who made the recent World Oceans day at Freeport Fleetwood such a success. Trawls in Fleetwood harbour resulted in us finding and identifying nearly 50 species, many of which were available for visitors to Freeport to see, and touch – before being returned safe and unharmed on the Saturday evening! Stars of the event included a European eel, a lobster, a greater pipefish and several species of flatfish.

More from this event on That’s Lancashire TV (via YouTube):

Posted in Conservation, Events, Marine science update, Shore walks

Wanderers of the sand

December 12th, 2015

Bernard the hermit crab

At our December meeting we looked at some of the birds and fish that use the Bay – waders feeding on the rich pickings in the mud while the tide is out, replaced by flatfish swimming in with the tide to feed while the mud banks are immersed. The Bay is ranked second most important area for migratory birds in the UK, offering a vital stop-over point on the East Atlantic Flyway, connecting wintering grounds in South Africa with feeding and breeding grounds in Norther Canada, USA and Russia. Rather less is known about the fish population, but both birds and fish are free to move in three dimensions, and have the freedom to exploit the Bay. Our next talk looks at groups of animals that have more limited movement, and must stick to channels, or suffer being flooded and dried out twice a day…

Hunters and hunted – those that crawl the sands of the Bay are an alien band of creatures, armoured, multi-armed, poisonous; whatever it takes to survive… Bernard the hermit crab (above) has sharp eyes, but he is too slow to escape the fish that might snack on him, so he retreats into an old whelk shell, guarding the entrance with his impressive claws.

On Wednesday the 13th January we will have three short talks on starfish, crustaceans, slugs and snails:

‘Wanderers of the Sand’ 19:30hrs Wednesday 13th January at the Gregson Community Centre, Moore Lane, Lancaster LA1 3PY
All welcome – admission £2, proceeds to Lancashire Marine Conservation Society.

Posted in Marine science update, MCS talks

MCS Marine Life ID course at Leighton Moss Nature Reserve

May 28th, 2015

Saturday 18th July 10:00-17:00: Members of the Lancashire MCS will be presenting an introduction to marine life, with a particular focus on life in the Bay area and the North West Coast of the UK. This course is suitable for beginners, and introduces many of the important groups of marine life, from shore plants to fish. Price £10 per person.

Booking is essential for this event, please contact us to confirm your place.

Download our poster for more details (PDF 446kB).

Posted in Marine science update, MCS talks

Algae spring surprises

January 6th, 2014

Any of you who have attended one of our marine plants ID courses will recall that we are a bit hazy about identifying the coralline, pink encrusting species. It looks as though our reticence (or ineptitude!) on this topic is more than justified, with recent genetic studies from Mexico indicating that their most common coralline alga is actually a community of five species.

Science Daily – coralline algae species

(New ID courses are planned for 2014 – see our diary for more information)

Posted in Marine science update

Estimating diving conditions in Morecambe Bay

October 14th, 2013

By Barry Kaye, Local MCS, 9th October 2013

The talk reviewed a web project that brings together physical information about the Bay from a range of sources, including weather, sea state and river inputs. This data informs our current understanding of physical processes in the Bay. Data are interpreted in a map that shows sea states, wind directions and the levels of principle rivers over the last five days. In addition, graphical displays review sea-sate (wave height and period) and river levels over the last fifteen days.

Graph showing river levels into Morecambe Bay
Graph showing river levels into Morecambe Bay over the last fifteen days (archival data)

The talk went on to look at how physical conditions might interact with the geography of the Bay to influence diving conditions. There is no formal model of the Bay’s ‘underwater weather’, but a number of approaches to developing such a model were proposed.

A link to the observatory is given below, users are advised, however, that this is a ‘work in progress’, there are a few rough edges, and information is provided without warranty of any kind:

[Editor’s note: Sorry, this resource has been removed.]

Posted in dive trips, Marine science update, MCS talks