I am currently conducting research on benthic microalgae in the intertidal zone along the central California coast, specifically focusing on grazing by marine snails. As part of this study, I have captured a series of scanning electron microscopy (SEM) images to analyze the morphological diversity of microalgae.
I am hoping to differentiate between various morphologies at a higher taxonomic level (e.g., distinguishing diatoms, cyanobacteria, and other microalgae) without delving into species-level identification. However, I have encountered some challenges in identifying the specimen depicted in the attached image (what higher taxonomic level it belongs to or if it is, in fact, even algae!) I have drawn a box around the specimen in question.
I would greatly appreciate any insights or guidance regarding the identification of this specimen. Any suggestions or references to relevant literature would be invaluable.
Thank you for the help!
Alexis
Hello Alexis, do you have a higher magnification image? Perhaps the small details are bacteria or a coating of a salt.
Alexis--as David Patton mentioned, perhaps there is a salt coating that results in a less clear image of the micro-organisms--should be relatively easy to check for presence of salt coating using the elemental analysis capabilities of most SEMs. If salt coatings are indeed present; how about first rinsing your samples with a diluted aliquot of your seawater samples (or maybe can use an ion-exchange/membrane device for sample prep), to reduce the amount of salt coating. Of course there may be other undesirable structural effects on micro-organism morphology caused by the lower osmotic pressure of the diluted sample solution; however likely not as significant as the morphological changes accompanying the dessication that occurs in the near- vacuum environment of the SEM sample chamber.
you have to rince your sample with distilled water using a Nuclepore filter (1µm pore size)...here it is impossible to see anything
and sorry but benthic diatoms is a world !!!
CRG
Thank you so much David Patton & James C. Trask & Catherine Riaux-Gobin I feel more confident that this is likely not algae - bacterial coating or salt does seem more likely. Furthermore, your recommendations to use the elemental analysis features and rinsing through a Nuclepore filter are much appreciated. After briefly clicking around with the live elemental analysis, there did seem to be a high presence of sodium in this area. Thank you for the advice! I have also attached a second image at higher magnification.
Hello Alexis, thanks for the new image. Your image was captured using a backscattered electron detector with a 15kV beam. Your biological material is probably the wispy "gauze" like substance on top of the "particle layer". You may be able to see this more clearly by using a secondary electron detector at 2-5 kV. I see you used a Phenom - it may not have an SE detector. You could try dropping your voltage with your BSE detector but image quality may drop off. The "particles" are 300-500 nm so too small to be microalgae (Chlorella is 5 microns). They could be bacteria or an inorganic substance. They are quite easy to see - have you fixed and gold coated this sample. EDX should help. The sodium peak should have a larger chloride peak if there is a lot of salt. It can crystalize as cubes or show a dendritic pattern.
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