Download Living Shipwrecks: Science Under the Sea

Living Shipwrecks: Science Under the Sea
1. UNDERSTANDING LIFE IN THE SEA
We are land animals. It is hard for us to begin to understand what it is like to
live in the sea. Sea creatures have to face all sorts of problems, quite strange
to us. Even those familiar seashore plants and animals such as crabs, snails
and seaweed have to put up with salty water, the tide going in and out, sun
and wind, crashing waves, not to mention us poking them about! Under the
sea the main factors that decide what lives where are: depth and light,
currents, food, competition and the type of seabed.
 Depth and Light
Sunlight, shining down on the sea, is absorbed by the seawater as it goes
down. In shallow water there is plenty of light but as you go deeper it gets
dimmer and dimmer. A diver exploring a wreck in deep water would have to
take a torch.
Why is sunlight so important?
Seaweeds, like all plants, need sunlight to grow. They get their energy from
the sun. So… You only find seaweed growing in shallow water.
Animals, such as sea snails, that eat seaweed have to live where their food is.
So… You find plant-eating animals (herbivores) only in shallow water.
Animals that need to see their prey must live where there is plenty of light.
So…You find some predators only in shallow water.
Animals that use their eyes to avoid being caught and eaten by a predator
must live where there is enough light.
So… You find some prey only in shallow water.
?
Why is the sea blue?
Sunlight contains all the colours of the rainbow: red, orange, yellow,
green, blue, indigo and violet. Seawater absorbs all the colours to a
different degree. Red colour is absorbed quickly, so can only travel to
a very shallow depth. Blue can travel to depths. This is why animals
living in shallow water use many different colours to defend themselves
or attract a mate.
Colour becomes less important as you go deeper; fish use variations of
lightness, darkness and brightness, instead.
Blue colour is reflected in all directions, making the sea look blue. The
brighter the sunlight, the bluer the sea looks. Particles, suspended in the
water, can also reflect light, altering the blueness – that is why the sea
looks turquoise when the cliffs and the beach are made of chalk or clay.
 Currents - Rivers in the Ocean
The sea does not stay still, like a pond. It is constantly moving. On the
surface waves are formed by wind blowing over the surface of the water.
The water moves beneath the surface, too. These water movements are
called currents. they are often mapped on charts to help sailors work out
where they are and plan their voyages. The rise and fall of the tides cause
horizontal currents. The wind also creates horizontal currents. Water may
also move up and down when salty water meets less salty water.
Why are currents so important?
Many creatures in the sea feed on microscopic plants and animals in the
seawater called plankton. Currents bring them a fresh supply of plankton.
So… animals that feed on plankton live where there are currents.
Many creatures in the sea release eggs and sperm into the seawater. The
fertilised eggs form microscopic larvae, which are swept away in the current
to settle and grow somewhere else.
So… animals that produce larvae and need to find space for the larvae
to settle, live where there are currents.
 Food
Understanding Marine Food Webs
From the microscopic plankton to the largest whales, all the plants and
animals in the sea depend on each other. They are all important links in
marine food chains and form a pyramid of life. Energy is passed from link to
link.
Plants trap the sun’s energy, herbivores (plant-eaters) feed on marine plants,
small animals prey on the herbivores, larger predators hunt the smaller ones
and so on, up to the top predators (sharks, dolphins and, of course,
humans).
Long food chains are formed, making up a complicated food web. Energy
is transferred from level to level. These are known as trophic levels. Energy
is lost each time it is transferred from trophic level to trophic level.
The upper trophic levels are very much limited by the availability of energy.
Animals use energy up as they swim, feed, hide, fight...and just exist.
Therefore, because energy is lost along the way, many small creatures are
required to support the larger animals further up the pyramid. As a result there
are far fewer animals at the higher levels – being a top predator is hard work so the ocean food web forms a pyramid of life with millions at the bottom and
only a few at the top.
Trapping the Sun
The sun's energy is first trapped by plants – not just seaweeds but the
seawater is also full of tiny plants (phytoplankton). You need a microscope
to see them but they are the base of our pyramid. We call these plants
producers. We refer to the amount of the sun’s energy harnessed by marine
plants, as productivity. Because sunlight can only penetrate seawater to a
limited depth, the areas of highest productivity are the surface layers of
oceans and shallow waters around our coast.
Tiny Drifters
The phytoplankton share their microscopic world with tiny animals
(zooplankton). That crystal clear seawater is teeming with zooplankton;
many are the young (larvae) of creatures like crabs, barnacles and starfish.
They feed on phytoplankton.
Sieving the Sea
Many marine animals, such as soft corals, sea squirts and sponges, sieve
plankton from the passing seawater. We call them filter-feeders. They are
consumers and the next trophic level of our pyramid.
Hungry Browsers
Filter-feeding animals, anchored to the rocks, provide endless low energy
snacks for fish such as wrasse, whose sticking-out teeth are specially
designed to nibble at the animal growth on the rocky reefs. Other animals,
such as sea urchins and starfish, also prey on filter-feeders.
Predators and prey
The energy is starting to build up now, enough to sustain larger fish and
shellfish, such as the lobster. These are predators hunting for their prey.
The Hunters
There are fewer animals at the 'top' of our pyramid but they are large and
must hunt to get their share of the sun's energy, originally trapped by tiny
plants. A good-sized fish for lunch will provide the bottle-nosed dolphin with
the energy it needs to search for its next meal. It is a top predator.
Scavengers, such as crabs, prawns and some snails have an important role
to play in the ocean food web. Like vultures on land, they clean up dead
matter.
? Where do you think people fit into the marine pyramid of life?
So… animals are found where their food is.
 Competition
Marine animals compete for space and food. The more competition there is
for food, the less chance there is of getting your share. Different types of
animals therefore have special design features – we call it adaptation – to
live and succeed in a particular place (niche).
This adaptation might give them an edge over competitors. They might be
camouflaged to sneak up on their prey or to prevent a predator spotting them.
They might be specially adapted to burrow. If other conditions (light, currents
etc.) do not suit, another type of animal will occupy the niche.
If animals are adapted to live in particularly difficult conditions, they have less
competition to worry about!
So… animals are found where they are adapted to live and can compete
successfully for food.
 The Seabed
Non-divers often make the mistake of thinking the seabed is a flat, sandy
desert. In fact, it is like a landscape under the sea – a seascape. There are
rocky reefs with overhangs, caves and crevices – plenty of hiding places for
sea-dwellers; sandy plains – perfect for burrowing; coarse gravely areas;
rocks and boulders. And… there are shipwrecks! All these provide a
physical environment (habitat) – ‘a home’ for communities of marine life.
We have all these marine habitats off the Dorset Coast.
So… seaweeds, and animals such as barnacles, sponges, soft corals
and sea firs, which are stuck to the rock, are found on reefs, rocks and
wrecks.
So… animals, such as lobsters and crabs that need safe hiding places
are found in cracks, crevices and caves.
So… animals, such as sea squirts and fan worms, which like shady
places, are found under rocky overhangs.
So… burrowing animals are found in soft sand or gravel.
 Finding a Home
Different types of marine animals have different strategies to make sure their
young have a chance of surviving and spreading to other similar habitats in
the sea. Some fish, like the Cuckoo Wrasse, guard their eggs until they hatch
– in wrasse, it is the male who plays nursemaid!
Most marine creatures, however, release eggs and sperm (spawn) into the
sea. Huge numbers of larvae are swept away. These are the plankton –
microscopic larvae of crabs, lobsters, starfish, mussels, sea squirts and many
more marine animals. Perhaps better not to think about it next time you are
sea bathing and swallow a mouthful of ‘clear’ seawater!
Often these larvae bear no resemblance to the adult. They drift with the
currents and most get eaten, but… and here’s the strategy… a few make it
and settle down in a suitable place and change into adults.
So… so long as there are communities of these animals fairly nearby
and currents to transport their larvae, a suitable new habitat will be
colonised.
A shipwreck might provide such a habitat.
2. SHIPWRECKS AS HABITATS
 Artificial Reefs
When a ship sinks, it is a disaster for the sailors and passengers on board
and the owners of the ship and its cargos. Every cloud has a silver lining,
though. It is great news for sea life!
A wreck, like other man-made structures in the sea – sea walls, groynes and
piers - creates an artificial reef with all the different habitats found on a real,
rocky reef: a hard surface to cling on to, shady overhangs and lots of hiding
places.
Marine life is quick to colonise any suitable man-made structure, as any boatowner will know! We have many such structures in Dorset…

The piles of Swanage Pier are an underwater photographer’s paradise.
Shaded by the pier itself, they are colonised by the invertebrate animals
you would normally have to dive to some depth to see. They are covered
with sponges, plumose anemones, dead man’s fingers, fan-worms and
much, much more.

The breakwater around Portland Harbour provides a habitat for several
rarities because the currents and wave action are weak, allowing silt to
build up. Rarities include the shy Black-faced Blenny.

Artificial reefs are being placed under the sea in various parts of the world
to attract fish. In Poole Bay in Dorset, in 1989, an experimental artificial
reef was laid on the seabed by Southampton University to study
colonisation by marine life. The reef was made from blocks of coal ash
and cement.
The growth of animals on the reef was monitored. Within an hour, small
shoaling fish, such as Pout and Pollock, were attracted – in hope of
finding a meal sheltering there, or perhaps the ‘reef’ was a welcome hiding
place, or just curiosity, who knows? Wrasse, which are typical territorial
fish of inshore rocky reefs, arrived within the first month and lobsters and
crabs soon began to move in.
The surfaces of the blocks were first colonised by tube worms and sea
squirts and after 3 months, small red seaweeds were growing on the
tops of the blocks. Now it is covered with a dense growth of plant-like
animals – hydroids, bryozoans and sea squirts. 90 different types of
plants and animals have been recorded on and around the ‘reef’.
Poole Bay is a perfect place for an artificial reef because the seabed is soft
and sandy so hard reef is in short supply, but there are natural, rocky
reefs within a few miles. So… the currents bring a constant supply of
larvae of reef-dwelling animals just looking for a home.
?
What can we make artificial reefs out of next?
Marine Scientists at Southampton University are currently researching the use
of old car tyres to build reefs… and there are plenty of them around!
So… what about Dorset’s wrecks?
Just like the natural habitats under the sea, what lives on, in and around
wrecks depends on the depth and the amount of light, currents, food,
competition and the surrounding seabed. It also depends on the material the
ship was built from and how long it has lain on the seabed.
 Marine Life on and Around Wrecks
In this section are listed some of the plants and animals that are found on and
around wrecks. For each is given some information on where it likes to live.
All plants and animals have a Latin name as well as their local common
name. This is so that there is no confusion when it occurs in different
countries. Scientists always use the Latin name to describe a type of plant or
animal.
The Latin name is always written in italics, or underlined. The first word is like
your surname and is the generic or name of the genus. It begins with a
capital letter. The second word, the specific or name of the species, is like
your Christian name. It is all written in lower case.
Fish
Pouting (Trisopterus luscus) – Common, shallow water, shoaling fish, often
found around wrecks more than 10m. deep.
Pollack (Pollachius pollachius) – Common, shallow water shoaling fish, often
found around wrecks more than 10m. deep.
Tompot Blenny (Blennius gattorugine) – In kelp forests, small holes and
crevices in reefs down to a depth of 35m. Omnivorous - feeds on sea firs,
molluscs, shrimps, worms and seaweed.
Conger Eel (Conger conger) – Hides in large holes in rocks and wrecks
during the day from shallow to very deep water. Has a very large mouth and
strong jaws. A top predator, feeding on fish and shellfish – anything that
moves – at night! Can inflict a serious bite.
Brill (Scophthalmus rhombus) and Plaice (Pleuronectes platessa) – Flat fish,
adapted to live on sandy seabed to about 100m depth. They feed on small
shrimps and fish on the surface of the sand.
Ballan Wrasse (Labrus bergylta) – Among rocks and seaweeds down to
20m. They scrape barnacles and mussels from rocks and wrecks with their
teeth.
Sea Squirts
Star ascidian (Botryllus schlosseri) – a colony of tiny, jelly-like animals,
forming a smooth mat showing star patterns on weed, rocks and wrecks from
the shore down to 20m. depth.
Lightbulb sea squirt (Clavelina lepadiformis) – Transparent, jelly-like,
stalked creatures, resembling light bulbs. On rocks and wrecks, where there
are strong currents, from 5 to 20m. depth. Feeds on tiny particles of food,
suspended in the water.
Starfish
Brittle star (Ophiothrix fragilis) – Has a central disc and long, thin arms.
From 10 m. to 150m. depth. They can form a thick carpet on the seabed (up
to 10,000 sq. m.). They feed on plankton and occasionally scavenge dead
material.
Shellfish (crustaceans)
Lobster (Homarus gammarus) – Lives in holes and gullies in reefs and
wrecks, where there are strong currents, from 5m. to deep water. They come
out at night and are scavengers, feeding on dead animals.
Edible Crab (Cancer pagurus) – They hide under rocky ledges and in
wrecks, where there are strong currents, from 5m. to deep water. They feed
on other crabs, molluscs and sometimes scavenge.
Barnacle (Balanus crenatus) – On any hard surface in fairly still water. They
catch plankton with their legs, which protrude from their hard shells.
Molluscs
Shipworm (Teredo navalis) – Not a worm but a mollusc with a small, hinged
shell (bivalve) and a long body in a tube. They bore into any wood, under the
sea – piers, bridges, ships and wrecks – and feed on tiny bits of wood and
plankton.
Grey Sea Slug (Aeolidia papillosa) – On rocks and wrecks from the shore to
30m. depth. Feeds on sea anemones.
Mussel (Mytilus edulis) – Clings to rock and wrecks between 5 and 10m.
depth. Feeds on tiny particles of food, suspended in the water.
Worms
Candy stripe flat worm (Prosthecereus vittatis) – Lives on clumps of light
bulb sea squirts and beds of mussels.
Peacock worm (Sabella penicillus) – This worm creates a tube from mud to
live in. It occurs at all depths, attached to rock, wrecks, mooring chains in
muddy areas.
Soft Corals, Cup Corals and Sea Fans
Dead man’s fingers (Alcyonium digitatum) – Aptly named, finger-like mass
of tiny polyps with tiny, stinging tentacles. They are attached to rocks and
wrecks from 5m. to 50m. depth where there are very strong currents.
Devonshire cup-coral (Caryophyllia smithii) – On rocks, boulders and
wrecks at all depths below 5m. Very rarely found east of Portland.
Pink Sea Fan (Eunicella verrucosa) – Attached to rocks, boulders and
wrecks, where there are strong currents, below 20m. depth. Very rarely found
east of Portland.
Anemones
Plumose Anemone (Metridium senile) – A large, fluffy anemone often found
attached to wrecks from 5m. depth to deep water, where currents are strong.
Sea Firs
Sea firs – Branching, plant-like animals – like tiny anemones on stalks,
forming dense, bushy mats from below 10m. depth, where there are strong
currents.
Sponges
Many different types of encrusting sponges (animals) cover any hard
surface, from 5m. to deep water, where the currents are strong.
Seaweeds
Kelp (Laminaria hyperborea) – This is a heavy plant that needs something
hard to attach to. It grows in a dense forest in shallow water (5 – 15m.) where
there is plenty of light. Many smaller, red seaweeds attach to kelp plants for
support (epiphytes).
 Dorset Wrecks Factfile
The Royal Adelaide
Type of vessel: Iron sailing ship
?…
Length overall: 235 feet (
metres)
Weight: 1500 tons
Date sunk: 25 November 1872
Position: Chart Reference 50 34.65N; 02 28.50W. Map Reference SY664
755.
? Can you find out what these mean?
Description of location: Approximately 100 metres (depending on the tide)
off Chesil Beach, south west of Weymouth.
Seabed: At the bottom of steep, terraced shingle seabed, where it levels off.
It is an underwater desert. Towards Portland, there are kelp-covered rocks.
Depth and visibility: 10m. Visibility up to 13m
Physical factors: Scoured by shingle in winter seas.
Type of dive: Dive from the beach using SCUBA or snorkelling.
Access: Swim out from Chesil Beach. Impossible if wind is from the south
and more than a Force 3-4.
Currents: Strong, running parallel to the beach.
Speciality: Trigger Fish, which have been recorded by divers during the
last few years in the summer months. Were they there before but were
just not recorded?
Earl of Abergavenny
Type of vessel: Sailing ship, timber clad with copper.
?…
Length overall: 176 feet 11 inches (
metres)
Weight: 1200 tons
Date sunk: 5 February 1805
Position: Chart Reference 50 36.15N; 02 24.95W.
? Can you find out what this means?
Description of location: 1 1/2 miles south east of Weymouth Harbour
entrance.
Seabed: Mud. Weymouth Bay mainly sand and mud.
Depth and visibility: 18m. Visibility good but divers can easily stir up the
mud.
Physical factors: The wreck is fairly well buried in mud. Sheltered from
west and south-west winds.
Type of dive: SCUBA.
Access: Boat dive from Weymouth or Portland Harbour.
Currents: Mostly weak.
Avalanche
Type of vessel: Iron sailing ship with timber decking
?…
Length overall: 214 feet (
metres)
Weight: 1210 tons
Date sunk: 11 September 1877
Position: Chart Reference 50 26.56N; 02 50.65W.
? Can you find out what this means?
Description of location: West of Portland Bill
Seabed: Silt, sand and broken shale
Depth: 52 metres.
Physical factors to consider: Depth
Type of dive: SCUBA.
Access: Boat dive from Weymouth or Portland Harbour.
Currents: Mostly weak.
The Halsewell
Type of vessel: Timber sailing ship
?…
Length overall: 139 feet 7 inches (
metres)
Weight: 785 tons
Date sunk: 6 January 1786
Position: Chart Reference 50 34.10N; 02 01.75W.
? Can you find out what this means?
Description of location: Off Seacombe cliffs, near Winspit, west of
Swanage
Seabed: High rocks near the cliff. Gravel and sand patches with areas of
bedrock showing.
Depth: Less than 10 metres
Physical factors to consider: At the base of the cliff – waves and swell.
Type of dive: SCUBA.
Access: Boat dive from Swanage
Currents: Weak.
3. THE MARINE SCIENTIST
 A New Science
The modern study of marine science began with the voyage of The
Challenger (1872) and was furthered by the curiosity of Victorian naturalists,
so marine science didn't really exist earlier than that.
The sea - still a mystery
Only in the last century have people been able to explore under the sea –
either SCUBA diving (using self contained underwater breathing apparatus),
and in submersibles. We know more about space than the deepest parts of
the ocean. Marine scientists have to face a whole different set of problems to
scientists studying the land.
Just think about why surveying the sea is "a different kettle of fish".
What are the problems a research diver has to face?
 Weather (rough sea)
 Tides and currents
 Cold
 Air
 Bulky equipment
 Depth (a diver can only spend a limited time at depth)
 Boat transport
 Communicating underwater
 Limited vision
 Sea sickness
 And more….
A simple task on land can become difficult once you are underwater.
? How would you make field notes?
? How would you collect a water sample from exactly 20 metres depth?
Can you design a piece of equipment to do this?
? How would you collect a sample of sediment from the seabed? Can you
design a piece of equipment, which can be operated from a boat, to carry out
this task?
 Preparing to Dive
Equipment the marine scientist might need to survey a wreck:
 A buddy to dive with – YOU NEVER DIVE ALONE
 A warm dry or wet suit – the deeper you go, the colder it is
 SCUBA (self-contained underwater breathing apparatus)
 Mask and fins
 A buoyancy device – a life-jacket, which can be inflated underwater to
help the diver go up and down and maintain any depth in the water
 A weight belt – a diver has to have weights to compensate for the air in
his / her tank and suit
 A slate and pencil for writing notes
 An underwater torch
 An underwater camera/video camera
 Sample pots to collect specimens to identify
 An underwater compass
 A tape measure
 A quadrat – a 1 metre or ½ metre square frame, used to work out how
much seaweed or how many animals there are.
Before the survey, the marine scientist would find out as much as s/he could
about the wreck. S/he would study plans and charts. If the location is not well
documented, s/he might map the seabed using side scan sonar. This is a
form of echo sounding, operated from a boat. It produces a ‘picture’ of the
seabed, showing the hard and soft areas. A large wreck can be seen on a
soft seabed.
After the survey s/he will complete a log of the dive, identify any specimens
and write up the results.
 Speaking the Same Language
Ecology is the science of plants and animals in their
environment.
Marine scientists use ecological terms. To carry out a scientific survey, you
need to use these terms. Here is a list of some of the terms scientists use.
Many of the words originate from Greek or Latin.
If you wish to carry out the virtual dive activity included in the Teachers Centre
(Diving with a Purpose) (***LINK***) you will need to use these terms … just
to make sure we are speaking the same language!
Organism – A living plant or animal
Adaptation – A feature or features that make an organism able to succeed.
Benthic – Plants and animals that live on the bottom of the ocean are called
benthic organisms. They are not free-floating like pelagic (***LINK**)
organisms are.
Carnivore - An animal that eats meat (other animals).
Consumer - Any organism, which must eat other organisms (living or dead)
to get its energy.
Dispersal - Spread of a species to a new location. In many organisms, this
happens at a particular stage in the life cycle, and is often crucial to the
survival of the species. Organisms may disperse as spores, eggs, larvae, or
adults.
Ecosystem - All the organisms in a particular region and the environment in
which they live. The elements of an ecosystem interact with each other in
some way, and so depend on each other either directly or indirectly.
Environment - The place in which a plant or animal lives, and the
circumstances under which it lives.
Epiphyte - A plant, which grows upon another plant. The epiphyte does not
"eat" the plant on which it grows, but merely uses the plant for structural
support
Food chain / food web - All the interactions of predators and prey within an
ecosystem, describing how energy passes from one organism to another.
Habitat - The place and conditions in which an organism lives.
Herbivore - An animal that eats plants.
Kelp forest - Marine ecosystem dominated by large kelps. These forests are
restricted to cold and temperate waters, and are most common along the
western coasts of continents.
Marine - Refers to the ocean.
Niche - The portion of the environment, which a species occupies. A niche is
defined in terms of the conditions under which an organism can survive, and
may be affected by the presence of other competing organisms.
Nocturnal - Active only at night.
Nutrient - Any element or simple compound necessary for the health and
survival of an organism. This includes air and water, as well as food.
Omnivore – An animal that will eat anything – plants or other animals.
Pelagic - Pelagic organisms swim through the ocean, and may rise to the
surface, or sink to the bottom. They are not confined to live on the bottom as
benthic (***LINK***) organisms do.
Photic zone - Region of the ocean through which light penetrates,
and the place where marine plant organisms live.
Phytoplankton - Tiny, free-floating plants living in water.
Plankton - Tiny, free-floating organisms of the ocean or other aquatic
systems. They may be phytoplankton or zooplankton.
Predator - Organism which hunts and eats other organisms. This includes
both carnivores, which eat animals, and herbivores, which eat plants.
Prey - Organism hunted and eaten by a predator.
Producer - Any organism which brings energy into an ecosystem from the
sun. Most plants and many single celled creatures are producers.
Scavenger – An animal that eats dead animals
Sedentary - Not moving. Many organisms, both plants and animals, spend
the majority of their lives in one place.
Species – A group of individual organisms with common characteristics.
Zooplankton - Tiny, free-floating animals in the sea. Unlike phytoplankton,
zooplankton cannot produce their own food, and so are consumers.
 Find Out More…
If you want to discover more about marine science there are lots of books and
other websites to help you. Check out some of these…
Web Sites
Marine Conservation Society: http://www.mcsuk.org
British Marine Life Study Society: http://ourworld.compuserve.com/homepage/BMLSS/
Southampton Oceanography Centre (Artificial Reef Project): http://soc.soton.ac.uk
Marine Biology Web: http://life.bio.sunysb.edu/marinebio/mbweb.html
Books
Guide to Inshore Marine Life, David Erwin and Bernard Picton (Marine
Conservation Society)
A Discovery Guide ‘Underwater World’, Dr. Richard Pagett (Salamander
Books Ltd.)
Junior Nature Guides ‘Saltwater Life’, Leslie Jackman (Dragon’s World
Children’s Books)