It’s Valentine’s day this weekend. A time to celebrate that activity that marks the difference between living and non – living components of our planet. Love and Reproduction.
Living things are incredibly single minded and stubborn. Their sole objective is to reproduce, and organisms go to extraordinary lengths to achieve this goal. To be successful in reproduction or replication , living things usually need certain things. Firstly a place to safely settle. (A habitat.) Food to provide energy (Nutrients) and water that is essential for cell growth and metabolism.
Now here is where things get complicated. Living things range from micro-organisms which on their own cannot replicate or do not have every characteristic of a living cell such as a virus through to incredibly complex and large collections of cells as found in Blue Whales and elephants. Despite the huge differences in size the virus and the elephant need the basic requirements of habitat, energy and water to reproduce. Hold that thought whilst I start off on an apparently unrelated rumination.
What is Lava? It is the liquid magma that reaches the surface of our planet as it is ejected by a volcanic eruption. It is composed of a myriad of chemical elements and compounds. We have been watching it for the last few month being pumped out in Iceland. Surrounding the fissure there, there are square kilometres of hot but now cooling rock.
Lava can kill. Lava creeps or races down the sides of volcanoes destroying all in it’s path leaving death and devastation. It may spread but it is not reproducing. Spreading a the behaviour of a liquid. The volume stays the same it just changes depth. At the rifting Zone Iceland is growing. It is not reproducing it is spreading.
A cooled lava flow is a black and grey , jumbled mass of sharp sulphurous rock that scars the landscape. A doom-monger’s hell. A biologist’s heaven.
In structure and composition all lavas differ. However on average they are mineral rich and porous. The porosity is due to the rounded cavities produced by the bubbles of gas that help drive the eruption .
The surface of the lava is uneven, Folds and creases. Hollowed broken bubble cavities like mini basins. Wind, rain and frosts start breaking down the rough,sharp edges. The loosened particles collect in the corners and hollows of the rock.
Now let us go back to our life forms. seeking a home to raise their offspring.
At first the lava provides no place to in which to anchor sensitive roots of plants such as grasses. The mineral composition is more than likely toxic and any water collecting in the newly cooled lava hollows will be highly acidic. Certainly not a gardener’s paradise. Any insects that somehow arrive will find little food so will move on or die.
No insects to eat, so no larger vertebrates will be arriving to hunt for food.
The lava flow therefore appears to be an impossible place to live. Not so. It is a very desirable place for bacteria. Not the sort that cause dire health problems to us humans, but similar single celled organisms. The unforgiving habitat provided by a bare, wet or dry, smooth or rough rock surface provides us with an insight into my statement about the stubbornness of life to find a way to survive and so reproduce. At some stage in the history of our planet a cynobacteria met up with an algae and a fungus. They “fell in love” and decided to live together. The bacteria could form a mat on which the algae and fungus could cling too. The algae and bacteria could use the sun for photosynthesis to obtain the energy to grow. The fungus could absorb water and collect minerals in solution and, being larger, could provide some protection for this unlikely Ménage a Trois . So together they formed a symbiotic relationship to form a mini habitat that provided security,water and nutients. This complex structure is called a lichen and would be one of the first organisms to colonise the newly cooled lava.
Lichens like all living things eventually die Their remains contain some nutients including nitrates. Their skeletal remains may not completely disintegrate and the organic particles will collect in nooks and crannies in the hardened, rocky lava flow mixing with the volcanic ash and minutely fragmented particles of lava created by wind and frost erosion. This mixture forms a vitally neccessary substance to all higher life on earth. On land it is called soil and beneath water, the oceans and lakes it is called sediment. (sediments contain organic remains washed off the land and also remains from bacterial mats.)This substrate allows more complex plants to find an anchoring site for their roots.
For simplicity in this short artcle I will concentrate on a land lava flow
The first plant to find these substrate filled hollows are mosses. They form dense clumps or carpets and as they too die their remains add to the depth of the soil.
Mosses are followed by grasses. The height and structure of the grass determined by availability of nutrients,water and light. Btween the grasses other tough little plants that we call weeds grab a niche in the crevices. Their death and decay adds yet more depth to the substrate.
Sooner or later there is enough substrate to support a larger plant such as a tree or bush. Gradually the surface of the lava flow gets covered as the multitude of plants reproduce and their offspring grow, breeds and dies.
These plants provide shelter and food for animal life.. Insects, worms and others such as wood lice and thrips. They are food for larger vertebrates and so a new ecosystem has been created that can support hundreds of varying life forms.
This amazing process is called succession.
Each instance of succession will never be identical ot another. Every lava flow has a different mineral content. Our Icelandic lava flow as we see through the web cams is subject to cold winds, low light levels in winter and low temperatures. Pecipitation falls often as snow most of the year.
A similar flow on the slopes of Kilauea in Hawaii would have warm temperatures all year round, plenty of sunlight and warm rains.
It stands to reason that the succession on each of these lava flows will be considerably different although the initial or Primary succession as it is called, would follow a similar course. Bacterial and lichen growths, mosses, grasses then higher plants.
To illustrate these differences let’s look at two islands that have emerged from the sea. And briefly think about how such inhospitable surfaces can possibly be colonized successfully without any interference from us humans.
Surtsey and Krakatau
Surtsey Photograph courtesy of Kristjan Jonasson
Photgraph of Anak Krakatau 2014 Courtesy of Oystein Lund Andersen with my thanks.
Surtsey erupted out of the sea in 1963 and soon it became apparent that this new volcanic island was going survive the sea’s attempts at erosion.
The island was a perfect setting for the world’s first organized biological monitoring and recording of a pristine succession of life on new land.
So much has been discovered there that it is impossible to even start to list the findings. If you want to find more then do read the information on this site as a starter.
The findings there confirmed the basic progress of primary succession as described above.
But how did the bacteria and lichens get there? Firstly the wind carried fungal spores from the land close by and even further away. Animal hairs and bird feathers carried by the wind were carriers of other spores and bacteria.
Seeds of higher plants were washed up on the shore and managed eventually to put down roots. Birds carry seeds and spores on their feet and caught in theur feathers. Think of the burrowing puffin. Grass seeds get trapped on their feet and feathers as they go in and out to feed their young. Within ten years here was a diverse range of plants on the previously barren island and soon birds arrived and used the island as a breeding site.
However the progress of succession was not easy. The more sheltered areas and hollows allowed for a steady increase in species but the damaging storms that affected the island on a regular basis and the harsh, cold winters has resulted in patchy colonisation.
In 1883 Krakatau exploded leaving only several small islands showing above the sea. Since that date a new island has formed around the volcanic vent now known as Anak Krakatau. The huge eruption killed everything and the islands appeared bare and devoid of life. However with the warm climate and monsoon rains seeds that washed up on the shore by the sea and were carried by the wind found a fertile habitat. By 1886 there were 23 new species growing and in 20 years there were 115 species colonising the slopes. Interestingly each island’s succession was very different. Different species became dominant. Read a little more about it here.
This article just scratches the lichen covered surface of how life survives and flourishes in volcanic areas and I hope maybe I have encouraged some further reading on the subject.
To all my fellow Volcanoholics I wish you all nutrients in the form of chocolates, shelter in the form of a cosy sofa and may your water be turned into wine. Have a Happy Valentine’s Day and if you are on your own , celebrate anyway for Love and Succession makes the world a better place.
With thanks to the following:-
Yellowstone National Park
The Sertsey Research Society