Maryland Sea Grant Marine Education_ Biofilms & Biodiversity - How

Maryland Sea Grant Marine Education_ Biofilms & Biodiversity - How

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5/30/2017 Maryland Sea Grant Marine Education: Biofilms & Biodiversity ­ How 1/4 How To Calculate Biodiversity? The Steps To Follow | More About Measuring Biodiversity | Some Examples The Steps To Follow 1. Identify the number of different organisms present. How we did it . . . A stereomicroscope was used to identify the organisms found on the plexiglass discs (check out Featured Creatures to learn about what these organisms are and why they are found on the discs). An area on the disc was selected at random for biodiversity analysis before it was viewed under the stereoscope (check out Random Sampling to learn how it is done). The total area of the field of view (diagram w/formula for area of circle) analyzed was 1.5 cm 2 at a magnification of 15 (x) times. This technique was used for each sample to keep the data consistent. 2. Count the total number of each organism. 3. Use the numbers to estimate various measures of biodiversity . Species Richness (S) ­ the total number of different organisms present. It does not take into account the proportion and distribution of each species within the local aquatic community. Simpson Index (D) ­ a measurement that accounts for the richness and the percent of each species from a biodiversity sample within a local aquatic community. The index assumes that the proportion of individuals in an area indicate their importance to diversity. Shannon­Wiener index (H) ­ Similar to the Simpson's index, this measurement takes into account species richness and proportion of each species within the local aquatic community. The index comes from information science. It has also been called the Shannon index and the Shannon­Weaver index in the ecological literature. A comparison of one or all of these measures of biodiversity can illustrate changes in water quality conditions within a local community. Water quality parameters like light penetration, dissolved oxygen and salinity can have dramatic impacts on levels of biodiversity. Return to top More About Measuring Biodiversity When measuring diversity it is good to remember that what we are trying to describe is the relationship of individuals of varying categories within a community. These categories can be species, genera, families, or any other categories that you consider to be important. In our biofilm research, we use the number of individuals in each species observed (e.g., found on each acrylic disc). There are some underlying assumptions that all the measures of biodiversity have in common: 1. The categories are well known.
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