Tagged: diatoms


Diatoms

Good things come in small packages

And few eukaryotic things are smaller than diatoms, unicellular algae that are common, numerous and taxonomically extremely diverse, particularly in the oceans. Small? Yes, typically 20 – 200 µm in diameter. Good? Yes; their annual explosion in numbers during the first quarter of the year – the so-called spring phytoplankton bloom – essentially kick-starts productivity and ecology in a large part of the world’s oceans. By dint of their photosynthetic efforts, it is estimated that diatoms not only contribute approx. 25% of total (i.e. aquatic and terrestrial habitats combined) primary productivity on the planet, but also produce between 20 and...

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Image: Wikimedia Commons.

Vital amines

Notwithstanding plants’ rightly applauded self-sufficiency, and remarkable life-sustaining synthetic abilities using basic inorganic ingredients, some plant-like organisms need a little extra help in the form of organic compounds. Such organisms are known as auxotrophs and a common requirement is for certain vitamins (those ‘vital amines’ of days gone by) in the case of certain algae. The good news is that vitamins such as B12 are provided by bacteria, which the algae happily ‘appropriate’. The bad news is that work by Sergio Sañudo-Wilhelmy et al. reveals that coastal waters of large areas of the eastern Pacific Ocean are vitamin-deficient. Which is really bad...

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Image: Hannes Grobe, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany/Wikimedia Commons.

That sinking feeling…

Whilst forests – aided and abetted by cryptogams (see my previous post) – have a major role as biotic carbon sinks on land, in the oceans that role is largely down to the activity of cryptogamous phytoplankton, which ‘draw-down’ vast amounts of CO2 during photosynthesis. However – and unlike trees – much of that aquatic primary productivity is consumed by herbivores, which in turn are preyed upon by various levels of carnivores. Ultimately, a lot of the CO2 that is fixed is released quite soon thereafter in respiration. Which is why attempts to consign such fixed carbon that is retained...

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Rejoice, ‘tis the real Bloom’s Day (to be sure…)

June 16th is the date upon which certain individuals around the world celebrate Irish writer James Joyce’s 1904-set literary classic Ulysses. Termed Bloom’s Day – after Leopold Bloom, the famously impenetrable novel’s main character, whose Dublin comings-and-goings are minutely catalogued over a 24-hour period – this is only a day-long phenomenon. A recently discovered bloom of another – phytoplankton – kind, and which lasts far longer than one day, is reported by Kevin Arrigo et al. But such blooms – a ‘rapid increase or accumulation in the population of algae… in an aquatic system’  – are common enough, and the well-documented,...

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Diatoms

The Enormous Influence of Microscopic Marine Plants

Many phytoplankton share a common feature with their larger non-aquatic cousins, the land plants: chloroplasts. Therefore they are also united in their ability to photosynthesize and their environmental requirement of sunlight. Phytoplankton occupy the surface waters of our oceans where sunlight can penetrate. They account for more photosynthesis, carbon dioxide fixation and oxygen production than all the worlds rainforests combined. As the primary producers of the oceans they provide the basis of the oceanic food chain and have contributed to the evolution of the largest living creatures on earth. Phytoplankton feed zooplankton and these minute organisms in their billions make...

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Image: NASA Earth Observatory/Earth Science Enterprise.

Convoluted carbon cycle collection

Of all the biogeochemical cycles that help to sustain life on Earth, the carbon cycle  is arguably the most important (although not necessarily the most straightforward!). The following collection of papers help to underline how complicated and convoluted this near-perfect cycle is. Brian Hopkinson et al. have examined the efficiency with which marine diatoms concentrate CO2 (PNAS 108: 3830–3837, 2011). Why? Because these abundant unicellular phytoplankters are extremely important in fixing CO2 – ultimately from an atmospheric source via diffusion into sea water – and exporting that fixed carbon to ocean depths, and are responsible for ‘low modern-day CO2 concentrations in...

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