Protistiary - Protocols: Sampling Exposed Sediments

PROTOCOLS Sampling exposed sediments (muds and sand)
Look for clues as to the presence of microbial communities - such as coloration of the surface. With experience, it is possible to distinguish blue green algae, euglenids, dinoflagellates, diatoms, iron oxidising bacteria, p[urple sulphur bacteria, non sulphur bacteria and so on. When samples are collected, they should be returned to the laboratory for observation fairly quickly. If they have been concentrated during the sampling procedure, for example sdamples were taken with a plankton net, then the samples may degrade quickly. Avoid significant or sudden changes in temperature. Retain some fluid that can be filtered as used as trhe basis of a medium. Keep a record of where you sampled. Typical sampling gear includes: buckets 50 - 500 ml wide-mouthed flasks / jars sealable plastic bags sealable plastic containers - such as sandwich boxes wok-spoon forceps trowel tape - for containers indelible pens - to write on tape notebook Some folk like to take notes, GPS readings, temperature, pH etc. etc.
Intertidal sands and muds are good locations for collecting microbes. Organisms may be more abundant in muds, but the finer nature of muds requires greater care in collecting. This is a mangrove grove where the sediment is a mixture of fine sand and mud. Typically you arrive at sites such as this as low tide is approaching. The organisms take a little time to migrate up to the surface after the tide recedes, so collect in the middly of the tidal range.	Mangrove stand near Sydney Australia. Image and copyright, D J Patterson
Caution needs to be exercised in collecting from sediments. Only the upper layer of the sediment will be oxic. Deeper in the sediment, the supply of oxygen from photosynthesis within the sediment or from diffusion from the overlying water or air is insufficient to meet the metabiolic needs of the microbial community. The sediments become anoxic and sulphur-based metabolic pathways dominate. The result is the sediment is darkened by the presence of metal sulphides. Most species are restricted to the oxic regions or to the anoxic regions. Most are capable of withstanding short exposure to conditions they don't like. However, if a sample is taken with a lot of anoxic sediment, most of the oxygen-liking species will be killed.	The color of the sediment changes with depth. Only the top 2 mm or so are light colored, the remainder is grey or black indicating that these regions are anoxic. Note the subtle greeny/brown colours on the surface of the sediument, mostly cause by diatoms within the oxic regions of the sediment. From mangrove stand near Sydney Australia. Image and copyright, D J Patterson
A wok spoon is an ideal tool for sampling the surface of the sediment without picking up too much anoxic sediment.	Using a wok spoon to remove the top millimetre or so of the sediment . From mangrove stand near Sydney Australia. Image and copyright, D J Patterson.
When the sample is returned to the laboratory it can be seived in a tray using a flour seive. This removes any snails or other small animals in the sediment. The sediment is allowed to settle, the excess water can be removed with a turkey baster. The mud is then placed in trays and allowed to stand for an hour or so, after which time the surplus water is removed. The mud surface should be damp. One sheet of lens tissue is added, and 22 X 22 mm No 1 coverslips added. After 6-72 hours, representatives of the community will have migrated to the surface and can be observed. Keep some of the surface water as it may come in useful if you want to pick cells our from the sample.	Samples returned to the laboratory are placed in trays, surplus water removed, one sheet of lens tissue placed over the sediment and coverslips (22 mm X 22 mm No. 1. Image and copyright, D J Patterson
Leave the preparation to stand for 6-72 hours, and observe. Anoxia develops at the bottom of the trays and drives the organisms onto the coverslips that can be easily picked off with forceps. The rate at which the samples mature is a function of the amount of fine particles in the sediment, the amount of organic matter, and temperature. After some time, the sediment under the coverslips will darken indicating that anoxia has developed. Enjoy.	Image and copyright, D J Patterson
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PROTOCOLS

Sampling exposed sediments (muds and sand)

Look for clues as to the presence of microbial communities - such as coloration of the surface. With experience, it is possible to distinguish blue green algae, euglenids, dinoflagellates, diatoms, iron oxidising bacteria, p[urple sulphur bacteria, non sulphur bacteria and so on. When samples are collected, they should be returned to the laboratory for observation fairly quickly. If they have been concentrated during the sampling procedure, for example sdamples were taken with a plankton net, then the samples may degrade quickly. Avoid significant or sudden changes in temperature. Retain some fluid that can be filtered as used as trhe basis of a medium. Keep a record of where you sampled.

Typical sampling gear includes:

buckets
50 - 500 ml wide-mouthed flasks / jars
sealable plastic bags
sealable plastic containers - such as sandwich boxes
wok-spoon
forceps
trowel
tape - for containers
indelible pens - to write on tape
notebook

Some folk like to take notes, GPS readings, temperature, pH etc. etc.

Intertidal sands and muds are good locations for collecting microbes. Organisms may be more abundant in muds, but the finer nature of muds requires greater care in collecting. This is a mangrove grove where the sediment is a mixture of fine sand and mud. Typically you arrive at sites such as this as low tide is approaching. The organisms take a little time to migrate up to the surface after the tide recedes, so collect in the middly of the tidal range.

Mangrove stand near Sydney Australia. Image and copyright, D J Patterson

Caution needs to be exercised in collecting from sediments. Only the upper layer of the sediment will be oxic. Deeper in the sediment, the supply of oxygen from photosynthesis within the sediment or from diffusion from the overlying water or air is insufficient to meet the metabiolic needs of the microbial community. The sediments become anoxic and sulphur-based metabolic pathways dominate. The result is the sediment is darkened by the presence of metal sulphides.

Most species are restricted to the oxic regions or to the anoxic regions. Most are capable of withstanding short exposure to conditions they don't like. However, if a sample is taken with a lot of anoxic sediment, most of the oxygen-liking species will be killed.

The color of the sediment changes with depth. Only the top 2 mm or so are light colored, the remainder is grey or black indicating that these regions are anoxic. Note the subtle greeny/brown colours on the surface of the sediument, mostly cause by diatoms within the oxic regions of the sediment. From mangrove stand near Sydney Australia. Image and copyright, D J Patterson

A wok spoon is an ideal tool for sampling the surface of the sediment without picking up too much anoxic sediment.

Using a wok spoon to remove the top millimetre or so of the sediment . From mangrove stand near Sydney Australia. Image and copyright, D J Patterson.

When the sample is returned to the laboratory it can be seived in a tray using a flour seive. This removes any snails or other small animals in the sediment. The sediment is allowed to settle, the excess water can be removed with a turkey baster. The mud is then placed in trays and allowed to stand for an hour or so, after which time the surplus water is removed. The mud surface should be damp. One sheet of lens tissue is added, and 22 X 22 mm No 1 coverslips added. After 6-72 hours, representatives of the community will have migrated to the surface and can be observed.

Keep some of the surface water as it may come in useful if you want to pick cells our from the sample.

Samples returned to the laboratory are placed in trays, surplus water removed, one sheet of lens tissue placed over the sediment and coverslips (22 mm X 22 mm No. 1. Image and copyright, D J Patterson

Leave the preparation to stand for 6-72 hours, and observe. Anoxia develops at the bottom of the trays and drives the organisms onto the coverslips that can be easily picked off with forceps. The rate at which the samples mature is a function of the amount of fine particles in the sediment, the amount of organic matter, and temperature. After some time, the sediment under the coverslips will darken indicating that anoxia has developed.

Enjoy.

Image and copyright, D J Patterson

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