Diatoms, Algae and the Environment: a tidbit

I first started working with algae in 1999, during my undergraduate work at Oklahoma State University. My advisor, Bill Henley was working on a project at the Great Salt Plains National Wildlife Refuge to collect and identify the extremophile algae that lived there. In my years working there I became familiar with many of the algae taxa that inhabit inland saline habitats, especially the diatoms. Studying the diatom assemblages of the Salt Plains turned into my Masters Thesis and an enduring interest in diatoms. 


A diatom of the genus  Navicula  collected in Peru. 

A diatom of the genus Navicula collected in Peru. 

Diatoms are of great global importance. To start with, diatoms are responsible for between 20-40% of the earths oxygen production. This fact alone should make you want to hug a diatom. However, this huge contribution to global oxygen supplies is just a byproduct (even considered to be a waste product) of photosynthesis. The primary objective of any diatom is to fix carbon dioxide into energy and biomass. The resulting biomass happens to be tasty and nutritious to many organisms, and is therefore the base of many aquatic food chains, especially in marine systems. So, much of that tasty seafood we love, was once an unpretentious diatom. 

Anyone can quite quickly grasp the difference between having potatoes and not having potatoes. It is somewhat more difficult to establish the consequences of, for example Cyclotella americana Fricke being extirpated from Lake Erie.
— Stoermer and Smol, The Diatoms: Applications for the Environmental and Earth Sciences

Sometimes the high productivity of diatoms can get out of hand, especially in response to nutrient pollution into aquatic habitats. As this story reports, we are seeing an unprecedented bloom of the toxin producing diatom, Pseudo-Nitzschia all along the Pacific coast. 

Our understanding of nature and the environment is incomplete, as stated by Stoermer and Smol in the above quote about potatoes and Cyclotella. And, the limited application of the knowledge we do have may be keeping us from making breakthroughs in areas of environmental remediation and environmental industrialism. 

Simple Solutions for Increased Algal Productivity

I firmly believe in the K.I.S.S method. Ockham, of Occam's razor surmised that in the absence of certainty, a hypothesis with the fewest assumptions should be chosen. To me, this means that the simplest answer is the most correct. Although it is not easy to find the most elegant answer to a problem we must try. Since large scale production is still in its infancy, I've tried to determine how simplicity relates to yield of algae and algae products.

Often it seems like some people are employed to make things more difficult. Imagine how much time and resources would be saved, how many more projects would succeed if efficiency and efficacy were the rules. You get the idea, no matter which side of the line you stand. 

So, reducing complexity to simplicity is our goal. In terms of algal production the complexity is nature itself. All abiotic and biotic factors converging to influence the productivity and biochemical composition of a single cell. Much valuable work has been done studying how and where all of these data lie. But, we have yet been able to successfully apply this knowledge to meet our own estimates of algae production. 

My contention is that something as simple (yet with complex implications) as harvest and feeding regimes can have positive influences on algal biomass yields and biocompound production rates. If we can alter the culture management to influence our yields, within the range as defined by our system parameters, then we might be one small step closer to a operable production system. 

Now, look at this graph and see if you agree. 

Yield of algal cells in response to harvest volume, nutrient addition and media type. 

The above figure shows total number of Nannochloropsis salina cells yielded from an experiment with 12 treatments over the course of 25 days. The treatments are media, either f/2 or wastewater, added nutrients (+) or normal, and harvest volume (15, 30 or 45%). Letters above the bars indicate similarity (for shared letters) or dissimilarity. With this data set I am able to show that increasing harvest volume always results in increased yield, no matter the media or nutrient levels. This, I think, is simple and useful for anyone wanting to produce algae. That is the simple answer, and I will stop there. There is more to talk about in terms of harvest and feeding timing, and how this all influences bio-compound production. Keep thinking.