Diatoms: Microscopic Clues of Death By Drowning?

14 Mar
Light micrograph of radial and pennate diatoms under darkfield illumination


What are diatoms? How do they help the Medical Examiner determine that a death was from drowning?

Determining that someone has drowned is not as easy as it might seem. The finding of water in the lungs isn’t enough. Sure drowning victims most often have water-filled lungs but if a corpse is tossed into a body of water, the lungs will often passively fill as the water replaces the trapped air in the airways and lung tissue. However, if the ME finds inhaled debris such as plant and water-born insects, etc. deep in the lungs, this suggests that the victim was breathing at the time they entered the water and inhaled the debris-filled water. But this isn’t always found.

So a method for determining drowning is needed. Diatoms might help. Though controversial and definitely not universally accepted as a sign of drowning, this search for diatoms is an interesting forensic science technique. And this search is not in the lungs, but rather in the bone marrow.


The ME might also find clues to indicate that the victim was conscious before drowning by examination of the bone marrow. This might sound odd at first, but the key is in finding tiny creatures called diatoms within the marrow.

Diatoms are tiny single-celled organisms that scurry around in both salt and fresh water. They have silica in their cell walls and are very resistant to degradation. If the victim’s heart is still beating when he enters the water, any diatoms in the inhaled water will pass through the lungs, enter the bloodstream, and be pumped throughout the body, where they tend to collect in the bone marrow.

If a microscopic analysis of the marrow reveals diatoms, the victim must have been alive at the time of water entry. This technique may be useful in severely degraded or skeletal remains where no lungs or sinus tissues are available for examination. Unfortunately, diatom testing is not exactly that straightforward and is controversial. Some experts feel that diatoms are an inexact tool for determining if a drowning occurred. Some bodies of water contain no diatoms.

Also, they are found in air and soil and even on the clothing of the examiner. This makes contamination of the tested sample a possibility.


Howdunnit Forensics Cover


6 responses to “Diatoms: Microscopic Clues of Death By Drowning?

  1. Kathleen Mayger

    March 15, 2016 at 5:09 am

    This is my first time to your blog and it’s great! Thanks for all the great information and answers you provide. This post is very interesting. When you say some bodies of water don’t carry diatoms, is that regional? Just curious. Thanks!


    • D.P. Lyle, MD

      March 15, 2016 at 8:03 am

      Like all types of evidence, diatoms might or might not be found in the bone marrow in a given drowning victim but to get there at all requires that the person inhale water and the heart be beating so these little guys can be pumped from the lungs to the bone marrow via the bloodstream. There are regional differences in the types of diatoms present but virtually all bodies of water have them.


  2. Sue Coletta

    March 15, 2016 at 5:23 am



  3. Frank Karl

    March 24, 2016 at 5:10 am

    Diatoms are some of my favorite microscopic subjects. They were and still are used as test subjects for resolution test of microscope objectives. You can find them in some toothpaste or powders, polishing compounds and as filler materials. Many people use diatom powder as an insect retardant, their sharp silica shells puncture insect’s hard cases, the the insect drys to death. Your swimming pool may have them as will a long standing puddle and some flush tanks in the bathroom. Microscopists can quickly divide them by pore size into modern freshwater vs saltwater and fossil fresh and salt water varieties. Some microscopist collect them from around the world. It’s still and area that a amateur can still catch a march on the professional and identify an unknown species.



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