Seasons greetings after a long absence from the blogging world. Since my last post, circumstances have limited the time available for making progress. The little bit of time spent on synthediment has brought some challenges, and on-going trials with my two partner-laboratories have been very insightful to me. Although the trials "failed" to achieve the original goals, they uncovered factors that I had not recognized to be so important to synthetic sediment uses. Edison made lemonade from his lemons in similar fashion.
To get back into a more regular posting schedule, I am starting a mini-series of blog posts dealing with theoretical uses and benefits of using synthetic sediment. Not only will this provide me with blog material during lulls in lab-development, but ideas presented in these blog entries might seed your (the reader's) mind with other ideas for possible uses of synthetic sediment in the real world. Theoretical applications shared in this and future "uses and benefits" posts may be so specific that they would require extremely detailed and nuanced synthetic sediment formulations (recipes). It is my belief that these theoretical applications might only be realized through my "synthediment" procedural system of synthetic sediment preparation [... sorry for the crass commercial statement].
The first application envisioned for synthetic sediment is as a microcosm habitat for organisms that are kept and cultured in laboratories. Here's why:
[1] Commercial laboratories exist that provide testing services for assessing sediment quality. A common activity those labs do is to test a field-sediment sample for toxicity to live organisms (a bioassay). Scientists try to set up their tests so that all conditions are controlled and none of their test conditions will cause negative effects on the live organisms in the test. The only negative effects (if any) need to be attributed to the sediment sample with a high level of confidence. Since live organisms are complex entities, they can be a challenge to "control." If they are not, negative effects in the tests can be caused by poor health of the organisms. For this reason, organisms captured in the wild are seldom used in sediment toxicity tests.
[2] To minimize the chance of poor organism health being the cause for negative test results, labs cultivate and maintain their own population of organisms. Some of the more common test organisms cultured in biological laboratories are called aquatic macro- (visible to the unaided eye) or micro- (undetectable to the unaided eye) invertebrates ("lacking a vertebral column"). They are the river/lake/stream equivalent of spiders, worms and beetles we find on land. Proper care for these lab cultures requires expertise in the biology and physiology of these organisms. Such cultures are meticulously cared-for by maintaining consistent feeding, water, lighting and temperature conditions, among others.
[3] Aquatic systems (lakes, rivers, streams, ponds, etc.) are complex systems containing a range of habitats suitable for an even wider array of organisms. Some aquatic invertebrates are free-floating, swimming organisms that live and feed in the water column (e.g., plankton, water fleas, bacteria). Others exist almost entirely on the surface bottom sediment, at the junction of the water column above and the sediment material below. Those organisms (called epibenthic invertebrates) may burrow into the sediment a bit, but only into the very surface layer and never more than a few body lengths deep before coming back up to the surface. They may swim in the water column a times, but always very close to the sediment surface (e.g., snails, shrimp-like amphipods, copopods, etc.). A third group of organisms are true benthic organisms, spending the majority of their development cycle "underground" within the sediment material (e.g., worms, midge larvae, clams, etc.). Each type of organism, and at times even individual species, require their own specific "living conditions" or habitat for maximum growth, metabolism and reproduction.
[4] Organisms that naturally associate with sediment material as part of their normal development cycle in nature (the epibenthic and benthic invertebrates) will require some form of sediment substrate for maximum growth, metabolism and reproduction. If these types of organisms are cultured in the laboratory, their growing tanks or containers must contain some form of sediment substrate. The question is: What substrate can be used? If field sediment is used, there is a chance the sediment is contaminated and detrimental to the organisms in the lab. Material not collected in the field may be used to act as a surrogate substrate or artificial sediment. In this case, although the material can be guaranteed to be "clean" (not chemically harmful to the organisms), there is a chance that the artificial material is not suitable for the organisms' growth and health. It could be too fine, not fine enough, too fluid, or not containing organic material in sufficient quantities or of appropriate composition, for examples. The more realistic that substrate is, the better the benthic or epibenthic organisms may respond during culturing.
[5] Synthetic sediment, composed of a set of components that represent natural components in field sediment, can be created and conditioned in such a way that organisms will thrive in the laboratory. Substrates used currently are good enough; they include sand, nylon mesh, shredded paper towel, etc. However, could those same cultures be improved with more realistic synthetic sediment used as their culture substrate? Would organisms cultured in the realistic synthetic sediment provide better response when used in sediment bioassays? If so, those organisms can provide good quality data that helps environmental managers make good decisions about the true conditions of sediment in the field. That's the theory, at least...
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