And the colours fade to grey: What is coral bleaching?

By Stephan Kamrad

Hermatypic corals may look like lifeless rocks but they are really living creatures which belong to the animal phylum Cnidaria, together with jellyfish and sea anemones. Many members of the Cnidaria have tentacles equipped with specialised stinging cells that contain venom. These are used for self-defence and to prey on small fish and crustaceans. Hermatypic corals, however, have no stinging cells; they defend themselves with a rock-like, calcareous exoskeleton that is slowly deposited over years. Nor are they predators, instead they live in association with photosynthetic plankton from the genus Symbiodinium, often called zooxanthellae, and the photosynthetic pigments of these unicellular algae give corals their bright colours! Members of the Symbiodinium belong to the Dinoflagellates, a group only very distantly related to land plants and green algae. They are endosymbiotic, meaning they are completely engulfed by the coral’s plasma membrane and live inside their cells. The coral provides the algae with a protected environment and a number of nutrients, like ammonium and phosphate, which it filters out of the water. In return, the Dinoflagellates fix CO2 dissolved in the water to provide the coral with sugar.

coral

Bleached coral (credit Acropora)

Coral reefs are found in tropical oceans, usually only few kilometres off the coast or on sand banks where the ocean is still shallow enough for light to reach the photosynthetic corals at the ground. They are globally rare, covering only about 0.1% of ocean surface but are the habitat of over a quarter of all known marine species! Their incredible biodiversity make coral reefs a valuable resource. Millions of people depend on the reefs as rich fishing grounds. Additionally, reefs physically protect the coastline form incoming waves and prevent erosion. The great reefs of Australia, Florida and the Caribbean yearly attract hundreds of thousands of tourists. When considering their social and economic importance, ecologists speak of ‘ecosystem services’ provided by coral reefs and it turns out their monetary value is immense!

It is thus very concerning that we have seen an immense decline of coral reefs over the last decades. The Caribbean for example has suffered an 80% loss of their coral populations over the last thirty years! The underlying phenomenon known as coral bleaching is a process during which the usually so beautifully coloured corals expel their symbiotic algae causing them to turn white and die. The picture shows a bleached, white coral in the foreground and a healthy coral in the background. Coral bleaching is associated with high peak water temperatures and increasing water acidity, both of which are a direct consequence of rising CO2 levels in the atmosphere.

A group from the University of Georgia recently published new detailed insights into the bleaching process. The research team was able to observe a bleaching event as it was happening at a reef off the coast of Mexico. Their key findings, published in the Journal of Limnology and Oceanography, shows how coral/algae populations can adapt to changes and sometimes even recover from bleaching events. There are many different species of endosymbiotic Dinoflagellates, classified into 9 major clades, and it turns out some of them are more resistant to high temperatures than others. Single corals often host three different algae species at once and their relative abundance determines the temperature tolerance. Furthermore, bleached corals do not die immediately; they can be repopulated and their new composition of Dinoflagellate species is significantly different to their pre-bleached one.

The symbiotic relationship between corals and Symbiodinium is an active area of research. The hope is that through a deepened understanding, we might find ways to protect reefs from bleaching and dying.

Reference: Dustin W. Kemp et al. (2014) Community dynamics and physiology of Symbiodinium spp. before, during, and after a coral bleaching event. Limnol. Oceanogr., 59(3), 2014, 788-797 DOI: 10.4319/lo.2014.59.3.0788

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Fluffy Horror

By Nathan Smith

As a general rule, the fluffier a pet is the better. Fluffy things are cuter, more cuddly, and funnier when they move; it’s a win-all situation. But like all general rules, there are always exceptions. In this case the exception is fish.

Fish, as many will have already noticed, are not usually fluffy. Indeed it would be reasonable to put forward the hypothesis that fish and fluffiness are mutually exclusive and, for healthy fish, this is certainly the case. Unfortunately fish cannot always be healthy and sometimes unhealthy fish go fluffy.

Not a happy fish (credit Émilie Proulx)

Not a happy fish (credit Émilie Proulx)

The cause of such fluffiness is an oomycete, or water mould; a type of organism which looks like a fungus but is closely related to kelp. Specifically, it is caused by the oomycete Saprolegnia parasitica, which infects freshwater fish. S. parasitica causes grey/white cotton wool like patches on the skin and gills of infected fish and can coat up to 80% of the host’s body. These patches are external signs of destruction of the host’s skin and underlying tissue and this result in lethargy of the host, making it more susceptible to predation. If the host avoids predation, symptoms of late stage infection are impaired osmoregulation, which is caused by increased haemodilution due to the large scale surface wounds. This is followed by respiratory failure, caused by the extensive infection of the gills. Organ failure is the final result. A closely related species, S. diclina, also infects fish eggs.

Despite the bizarre symptoms, infection by Saprolegnia is no niche occurrence. Whilst it is generally not an issue for wild fish, generally only infecting wounded or otherwise immunocompromised individuals, it is a considerable problem in aquaculture hatcheries and farms, due in part to the overly high densities in which fish are kept. In these environments, losses of more than 10 % due to Saprolegnia are commonplace and as high as 50% in some more extreme cases. Furthermore, it has a significant economic impact, with conservative estimates putting the losses due to Saprolegnia infection at five million pounds per year in Scotland alone.

That Saprolegnia infection is so endemic in aquaculture indicates generally low health in the fish population and highlights issues within the industry. Fluffy fish may not be cute but they can’t be ignored.

Packaging: Is there mushroom for change?

By Sophie Harrington

It’s nearly Christmas and nowadays that seems to mean lots of online shopping. There’s nothing quite so convenient as avoiding the crowds, anxiety, and Christmas music on loop in favour of leisurely browsing from the comfort of your couch. For the most part, deliveries these days are highly reliable, even when you’ve ordered something that doesn’t do well with rough handling—perhaps a new set of glasses, or a bottle of champagne. It’s thanks to the use of packing materials such as polystyrene that we can even consider ordering such fragile items online.

A new use for corn stalks? (Credit Phoebe Baker)

A new use for corn stalks? (Credit Phoebe Baker)

Yet despite their convenience, there are a whole host of environmental concerns that come with traditional packing materials. Most people have heard that this sort of packaging never breaks down, and while that isn’t strictly true, polystyrene discarded in landfills, or left as litter will not degrade for hundreds of years. Our love for packing peanuts and Styrofoam has left us with a mass of polystyrene clogging up our landfills and environment.

But what if there was a better option? Enter mushroom materials, the brainchild of Ecovative. As an alternative to the petroleum-based polystyrene that forms a majority of the packing market, mushroom materials use only natural agricultural waste, such as cornstalks, and mycelium, or the “roots” of fungi. The agricultural waste is placed into a specific mould, through which the mycelium are able to grow, turning the material into a solid block. After growth is completed, the material is fully sterilised before being shipped out to their growing base of customers.

The use of agricultural waste in producing the blocks is only the beginning of their environmental benefits. Not only is this a use for otherwise discarded waste products from farming, but the products themselves are fully compostable at home. No need for expensive processing or complicated techniques to degrade the blocks—just break them up and leave in your garden.

Not just good for eating (Credit Christine Majul)

Not just good for eating (Credit Christine Majul)

Besides the obvious market in packaging materials, Ecovative are branching out into other areas, including furniture and even surfboards! There materials are perfect as light-weight foam cores and fins for surfboards, with the added benefit of being entirely degradable in a marine environment if the board is lost. The materials are also being developed for use as structural biocomposites, using “Myco Foam” that has been heat and pressure treated to compress into “Myco Board” for use in furniture that has no need for the addition of resin (and thus the use of formaldehyde), unlike traditional wood composites such as MDF. Who knew fungi could be so much fun?

Intrigued? Wish you could get involved in the “mushroom age”? Turns out you can even grow your own mushroom materials via the “Grow It Yourself” kit available from Ecovative. This might just make Christmas shopping even easier…

Thar She Blows: of Saharan Dust and Marine Productivity

By Charlie Whittaker

The Sahara Desert is not something you would usually associate with abundant life and vibrant algal blooms. It is one of the most arid and inhospitable areas in the world, representing the largest subtropical hot desert on the planet. And at well over 9,400,000 square kilometres- i.e. about the size of the United States, it is perhaps one of the most inhospitable areas globally. To say that it is unwelcoming to life is an understatement of epic proportions.

The Sahara Desert (credit mtsrs)

The Sahara Desert (credit mtsrs)

However, the desert is in fact one of the cornerstones of continued survival of one of the most abundant groups of organisms on the planet: the phytoplankton. This vast swathe of barren land is actually responsible for a dazzlingly complex and diverse ecosystem albeit thousands of miles away.

Tiny flecks of sand, red in colour due to the abundance of the element iron, are picked up the winds floating across the sand dunes, and in turn, carried thousands of miles westwards on the air currents. These tiny grains of iron rich sand then land in the ocean off the West coast of Africa, where they are responsible for sustaining a astounding array of life. Though individually insignificant and of little relevance, the sheer scale of their deposition makes them a globally relevant input- it is estimated that something in the region of 1015g/year get deposited courtesy of these Saharan winds Westwards. That’s 1012kg, or 1 billion tonnes!

A phytoplankton bloom in the Southern Ocean (credit ESA)

A phytoplankton bloom in the Southern Ocean (credit ESA)

But why all the fuss about iron though? Iron represents a fundamental micronutrient required as a cofactor for the enzymes of a ubiquitous number of different phytoplankton, from cyanobacteria to coccolithophores and diatoms to dizaotrophs. In particular, iron acts as an essential constituent of the enzyme nitrogenase, responsible for the fixation of atmospheric nitrogen. The photosynthetic organisms present in this group are globally significant in terms of the fixation of carbon dioxide from the atmosphere. These so called “forests of the ocean” contribute as much to the control of CO2 levels as tropical rainforests.

Given their dependence on iron then, there has been considerable interest in the concept of “iron seeding” the oceans as a means of generating blooms of these photosynthetic organisms. Such a sudden population rise would lead to increased CO2 drawdown and may have the potential to mitigate, at least in part, some of the consequences of continual anthropogenic mediated CO2 release into the atmosphere. Efforts doing this are still in progress but who would have thought the Sahara Desert, byword for desolate, bleak and lifeless, may have acted as the inspiration for one of the most ambitious biogeoengineering projects currently underway.

Deforestation- whatever that is

By Anna Klucnika

Society is slowly forgetting about deforestation.

That’s not in the sense that we forget it’s happening, but rather forgetting to care. I am one of the few who consciously try to recycle, to use less paper, to switch off lights. My family only recycles because otherwise the normal bin will overflow. My roommate has commented that environmental issues have been made up, as it’s “convenient” to allows us Westerners to stop development in other parts of the world.

The Bornean Rainforest  - how long will it last?

The Bornean Rainforest – how long will it last?

Even Rhett Butler, the man who founded a website that tracks global deforestation and has “devoted tens of thousands of hours to the cause of protecting forests” is not promoting a change in society’s attitude. He unwittingly commented that “lately – for the first time, really – I’ve started seeing cause for optimism about the future of forests”. This was gloriously picked up by the Independent in an article titled “Rainforests ‘out of danger’ thanks to global giants”.

This is like thinking world peace will work out next year.

Now clearly Mr Butler did not mean his words to seem that all of the world’s deforestation issues are resolved. I’m also delighted to hear Sally Uren, head of the sustainable development charity Forum for the Future, say “there is a much greater sense of shared responsibility and I am feeling reassured by the seriousness with which many big multinationals are taking this responsibility”.

But these are just words and many people will jump for joy that they can jump off the eco-friendly bandwagon.

Visiting the rainforest of Malaysian Borneo has made the issue or tropical forest conservation real to me. Driving into the heart of the land you see the town turn into jungle. Then once you get into the core primary rainforest, you realize what you thought was jungle earlier is just the left-over bones. The growing demand of palm oil (have a look at most labels and you’ll find it, probably mixed in with “vegetable oils”) has lead to dramatic fragmentation.

The new forests: Oil Palm plantation

The new forests: Oil Palm plantation

Fresh research by Benny Yeong has revealed that rainforest fragments below a certain size do not yield viable seedlings. This means that the forest will not regenerate. With an increasing proportion of the world’s forests being restricted into national parks, funded by ecotourism, this is a bad omen. Humans must intervene to help sustain forests. Conservation is no longer about stopping deforestation and conversion of land. It’s too late for that. Instead what precious forest we have left must be managed.

But with attitudes concentrating on tree hugging to prevent logging, society’s’ interest is fading. Instead there must be a new green revolution. Just as we try to prevent animal population declines and manage the populations of nearly-extinct species, we must do the same for forests.

Just go into your local bit of woodland and just experience the sense of awe. The sensation that a forest can provide is just as wonderful as that awe of watching wild animals. Forests are an evolutionary masterpiece of conquests, coalitions, and competitions. Since mankind has had such an impact on the Earth, we can no longer rely on the environment sorting itself out. Intervention is needed in a structured and positive manner. Some people are thinking in this way and making plans. But that does not mean that the cause should be abandoned. We must fight on for our forests.

Photos by Anna Klucnika

The Green Killers: Poisonous Plants in History

By Liam Elliott

 

‘My heart aches, and a drowsy numbness pains

My sense, as though of hemlock I had drunk’

                                                               John Keats

 

The word poisoning conjures up, to many imaginations, images of deadly dinner parties straight from an Agatha Christie novel or a world of cold war espionage. Whilst these depictions are perfectly justifiable, they often relied on the variety of deadly inorganic or synthetic poisons. Look further back into history, however, and there emerges the use of naturally occurring plant poisons, entwined with some of the most classical and romantic of legends. Scientifically, toxic compounds that may be found in plants often originate as secondary metabolites of which over 100,000 are known.

Secondary metabolites are, by definition, generally not considered to be essential for plant life and are derived from the smaller pool of primary metabolites. Some of these compounds we use every day including caffeine and theobromine whilst others, hopefully in less frequent usage, include cocaine and morphine. Some plants produce highly toxic secondary metabolites however and the historical use of some of these to silence an unwanted voice, or as forms of execution, is well documented

Let’s have a look at some of the most notorious poisonous plants and their history.

 

Atropa belladonna: Deadly Nightshade

Belladonna’s attractive berries and flowers have helped to entrain its place in mythology.

Belladonna’s attractive berries and flowers have helped to entrain its place in mythology.

Perhaps one of the best known poisonous plants and commonly known as belladonna (literally: beautiful woman), this plant produces a variety of poisonous alkaloids including atropine and hyoscine. The plant is a member of the Solanaceae family which also includes potatoes. Belladonna’s attractive berries are very poisonous and it is therefore somewhat ironic that the plant has a long history of medicinal and cosmetic use. Macbeth of Scotland, immortalized by Shakespeare, is said to have used the plant to poison an invading English army.

Aconitum: Monkshood

Also known as wolf’s bane and devil’s helmet, plants of this genus synthesise toxic aconitine via the terpenoid synthesis pathway. Aconitine is a neurotoxin which targets sodium channels in mammalian neurons. The striking flowers of these plants resemble the hooded clothing of monks and whilst their natural distribution is largely restricted to mountainous regions of the northern hemisphere they are reasonably common features in gardens. Nazi Germany is known to have used bullets coated in aconitum during WWII.

Abrus precatorius

Abrus precatorius berries as recently seen by some enthralled Part II students.

Abrus precatorius berries as recently seen by some enthralled Part II students.

A legume which produces the protein toxin abrin. This is similar to the infamous poison ricin, only around upwards of 70 times as toxic making it perhaps the most potent of plant poisons. The abrin produced is mainly confined to the seeds and the ingestion of a single one may be fatal to an adult human (whilst around 7 ingested berries of the legendary belladonna provide a fatal dose). Traditionally used to make jewelry in areas of South America, aphrodisiacs have also been historically produced from the plant.

Conium maculatum: Poison Hemlock

Native to the Mediterranean, the alkaloids produced by hemlock target neuromuscular junctions and can cause eventual respiratory paralysis and an unpleasant death. The famous Greek philosopher Socrates was sentenced to be executed in 399BC by drinking an infusion of hemlock. It has also been suggested that, in contradiction to traditional beliefs, that the final pharaoh of Egypt, Cleopatra, killed herself by drinking a hemlock-based poison. On the Greek island of Kea, where euthanasia was a societal norm in ancient times, the elderly are said to have drank hemlock infusion once they passed a certain age.

Plant toxins, and their often medicinal potential, give an example of the key place of plant sciences within society. Moreover, a basic level of plant biochemistry and history can give a fascinating insight into the way plants have shaped humanity.

The Future is No Clockwork Orange

By Nathan Smith

Imagine a life without citrus. No glass of orange juice in the morning. No slice of lemon for your iced tea. No having to segregate the green jelly babies because no one honestly likes them and you don’t understand why they continue to be produced. It would be a very different world indeed, but perhaps one we need to start considering.

Credit Father.Jack

Down with the green jelly babies… (Credit Father.Jack)

The threat to our favourite sources of Vitamin C comes from the double-pronged assault of the bacterial diseases citrus canker and huanglongbing (or citrus greening disease), which are currently having a massive impact on the citrus industry. To make matters worse there are few signs of resistance among the plants. This is mainly because the majority of citrus fruits aren’t natural species, they’re cultivars which are the result of varying inter-specific crosses. A few examples are the sweet orange, which is the result of a cross between a male mandarin and a female pomelo; and the grapefruit which is the result of a cross between a male sweet orange and a female pomelo.

800px-Fortunella

The invincible kumquat (Credit Acongagua)

A study by a group from Pakistan tested how various citrus cultivars responded to the citrus canker disease and found that some are more susceptible (like Valencia Oranges) than others (like Pigmented Oranges). While two cultivars were identified as highly resistant, Tahiti Lime and Kozan Sweet Oranges, all the cultivars showed some levels of disease. Unfortunately this indicates that all would eventually succumb to the ravages of citrus canker. That is, all except for the kumquats!  Both cultivars of kumquat tested (Meiwa and Naghmi) lacked the canker-caused lesions that unfairly graced the other plants. This may be because kumquats are only citrus fruits in the loosest sense. Unlike most of these other fruits, which belong to the Citrus genus or are products of genetic crosses within the genus, kumquats belong to the genus Fortunella. This makes them distinctly different to oranges and lemons genetically and means they may be a non-host for citrus canker and perhaps by extension for other diseases plaguing citrus; though reports of a huanglongbing-type disease in Kumquats in Taiwan suggests otherwise.

Even so resistance to citrus canker is promising. Humanity may learn to adapt and a future without oranges certainly seems brighter with the potential for Kumquat Flavoured Jelly Babies. At the very least they might taste better than the green ones.