Exert from final thesis: Common Algae of the Lake George Watershed, 2008 ; Future posts will include further identification of common algal forms of the Northeast United States.
How to collect algal samples
Algae can be collected in the field and brought back to the laboratory to be identified using a microscope. From identification a trained taxonomist and analyst can determine water quality impacts and possible toxic conditions.
Algae should be collected from all available substrates: (plants, rocks, docks, retaining walls, sand, and within the water column.) If algae are only found within the water column, three samples should be collected and combined into one container. This is called a multi-habitat sample. This method generates a greater understanding of what is taking place in the localized area of algal growth. Algae will respond rather quickly to available forms of nutrients, pollutants and changes in water quality.
Samples should be collected from a variety of substrates. Removable substrates such as: gravel, pebbles, cobbles, and woody debris should be removed from the water, brushed or scraped and rinsed into a container. Macrophytes and roots of other plants should be placed in a sample container with some water. (Shaken hard, and then the alga rubbed off to remove it). Plants are then removed from container. Non-removable substrate such as boulders, trees, and retaining walls need to be suctioned with a pipette. Loose sand and organic matter are gently lifted from water using a spoon, spatula or pipette and then rinsed into a container. All samples from a single site are placed in a single container and labeled with location name, date and collector’s name. While in the field, a field data sheet should be filled out for each site. Data collected on this form will assist in later conclusions. Each algae sample needs to be placed in a cool dark location for transportation back to the lab for identification. On returning to the lab, each sample is logged into the algae lab-processing book and placed in a refrigerator.
In the lab each sample of algae is identified down to lowest taxonomic level possible by use of microscope and varying slide mounts depending on abundance and forms of algae present. On average up to three slides per location is used based on the abundance of algae present. To remove diatoms from macrophytes and filamentous algae, a sample is placed in a small container with water and shaken. Algae are identified if a minimum of 5 cells are present. If after 5 minutes no new genus of algae is identified, no further identification needs to occur. For diatoms, generally 300- 600 individuals are counted.
Enumeration data should then be applied to indices. Following analysis of sample, a sub sample should be preserved if needed and logged for any future analysis (based on Barbour 1999 methods). Useful metrics based on algal composition include: Species and generic richness, number of divisions, presence and forms of Cyanobacteria, % Sensitive diatoms, Percent Achnanthes m., Pollution tolerance index, Trophic index, Salinity index, Siltation index, Palmer pollution Index, Percent community similarity index, Impairment of ecological conditions index, % Cyclotella sp., Area-specific cell densities and bio-volumes and Waste-water similarity index.
Why collect algal samples
Algae are an important foundation of stream and lake food webs, they are also extremely useful for determining impacts before a disturbance is evident in offshore monitoring. Any algal composition change near-shore may have important implications for management practices lake-wide, specifically when near-shore areas are utilized as a breeding and feeding resources for other organisms. Monitoring the littoral zone periphyton provides a useful marker for detecting localized changes resulting from anthropogenic disturbances or intermittent releases of sewage. It is best to monitor all forms of algae (both soft and diatoms).
Periphyton indices or metrics have been developed and tested for use in streams throughout the United States and Europe. These same metrics are just starting to be used in Europe within the littoral zone of lakes. Periphyton studies have been applied within the Water Framework Directive within Europe since 2006.
The principals for monitoring periphyton within streams are broadly applicable to sampling within the littoral zone of lakes. While most metrics focus on diatoms, researchers loose valuable information, if not including soft algae. By including the monitoring of filamentous greens and Cyanobacteria researchers are more likely to see algal composition changes and impacts to the food web.
Useful periphyton protocols and metrics have been created by the USEPA, USGS, and localized state agencies. When sampling within the littoral zone of a lake, it is best to utilize a multi-habitat sample that represents the area. This sample does not represent the entire lake, only that specific, localized location. Because of this, periphyton sampling can determine near-shore, upland disturbances. From faulty septic systems to excessive nutrients from stormwater runoff.
When sampling periphyton within the littoral zone, it is useful to first conduct a field biomass assessment. This can be done by developing a periphyton biomass index that incorporates littoral aerial flyovers, boating the littoral zone, and walking the near-shore areas. This also allows researchers to visually inspect the upland area for any anthropogenic disturbances.
As discussed earlier, there are many useful metrics that can be applied to algal samples. Other metrics and relationship between forms of algae and the water-quality and habitat are being created. While it is best to identify all forms down to species level, much information can be gathered by genus level only. This is important for a financial reasons, as the cost for analysis can be quit substantial if you have to have it sent out to be analyzed. It is also difficult to and time consuming to identify some forms of algae down to species level, as a fruiting body is necessary.
By coupling both field assessments with laboratory identification and application of metrics, researchers can determine changes in water quality, and the possible upland source.
Future post will include further identification of common algal forms found within the Northeast United States.
Please feel free to contact me. Corrina Parnapy: corrinaparnapy@yahoo.com, (518) 791-3256.
I am currently seeking a position in Vermont/ New Hampshire/ Mass.
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