Measuring Biomass

Biomass refers to the total number of living organisms in a certain area. It is the amount of energy that is available for the next trophic level. It is important to measure biomass because it gives an idea of the state of the ecosystem. By knowing the amount of energy available, one can know how many species it can support.

One way to measure biomass is to obtain the dry weight of an organism (since it is a rough approximation to the amount of biomass) and multiply it by the number of those organisms in a given area. The units are grams per meter squared (or cubed if it is an aquatic ecosystem). This is a commonly used method. However, the difficulty here is knowing with accuracy the total number of individuals, particularly if one wants to measure biomass in a wide area.

The way to get the 'most accurate' biomass measurement would require counting absolutely every organism. However, there are ways to get an estimate. One method is by making a transect, which means tracing an imaginary line across the selected ecosystem, and counting the organisms that are in the quadrants following the transect. That data can then be extrapolated to the rest of the ecosystem, or several transects can be made, to get a more accurate estimate.

Quadrats are another method in which a rectangular area is selected and biomass is counted in that specific place only. Random quadrats can be selected, and as with the transect, the more measurements (quadrats) you select, the better the estimate.

There is also a remote sensing technique that surveys the earth's surface from the air or using satellites. Images generated are analyzed to determine total biomass productivity. However, this is only used with producers, and works mostly on dense woodlands.

In the future, more technological tools will be developed and improved in order to measure biomass easily. This could include better imaging to determine biomass, as well as a technological tool that will help get an accurate number of the individuals of a species in an area. The main benefit is that the measurement will be non-destructive, harming no ecosystem.

After biomass is collected at different trophic levels, a biomass pyramid can be made. Here's an example of an estuary, more specifically, Chesapeake Bay. Taking the following food chain:

phytoplankton -> clams -> blue crabs -> sandbar sharks

Firstly, the units will be measured in kg per cubic kilometer, since it is a aquatic ecosystem. We can calculate the amount of each species in the food chain, and we get the following information:

There are 31,333,333 units of phytoplankton in 2320 cubic km of water in Chesapeake Bay.
There are 9,200,000 clams in that same area.
There are 278,666 blue crabs.
There is one sandbar shark.

Then, considering the weight of each specie and the area, we can calculate biomass, which then can be shown in what is known as a biomass pyramid. Results are shown below.

Bibliography:
Rosillo Callé, Francisco. The biomass assessment handbook. Illustrated ed. Earthscan, 2007. Print.

Kimball, John W. "Food Chains." Biology Pages. N.p., 23 Apr 2010. Web. 27 Aug 2010. .

Tackenberg, Oliver. "A New Method for Non-destructive Measurement of Biomass, Growth Rates, Vertical Biomass Distribution and Dry Matter Content Based on Digital Image Analysis." Oxford Journals (2007): n. pag. Web. 27 Aug 2010. .

Measuring Biodiversity

Biodiversity is the total amount of different species that are found in a given ecosystem, biome or the entire planet. It is an indicator of the health of an area. The greater biodiversity there is, the healthier the ecosystem is.

There are several ways to measure the biodiversity of a given area. The two most popular indices are the Shannon Index and the Simpson Index.

However, before we can talk about measuring biodiversity, two key terms we should know are richness and evenness.

Richness: Number of species per sample.

Evenness: Relative abundance of the different species making up the richness of the area.

The Shannon Index

H= Shannon Diversity Index

S= Total # of species in a community (richness)

Pi= Proportion of S made up of ith species

Eh= Equitability (evenness)

Equitability is measured H/Hmax. Hmax=lnS

To learn more about the Shannon Index go here: http://www.tiem.utk.edu/~mbeals/shannonDI.html

The Simpson's Index

It measures the probability that two individuals randomly selected belong to the same species (or other category)

n= total # of organisms of a particular species (in plants, the % of coverage is measured)

N= total # of organisms of all species

There is also Simpson's Index of Diversity, which measures the probability that 2 randomly selected individuals in a zone belong to different subspecies.

The formula is 1-D.

Finally there is the Simpson's Reciprocal Index, which measures the number of equally common subspecies that will produce the observed Simpson's index.

The formula is 1/D

For more information: http://www.countrysideinfo.co.uk/simpsons.htm

The Key to Classifying

We know that organisms are classified using the Linneaen taxonomic system, and they are named using binomial nomenclature. However, what do we do when we encounter an unknown organism? How can we name an organism found in the wild?

A dichotomous key is a tool used to identify organisms in a systematic way. It can be used to identify organisms parting from a certain taxonomic level. These keys are organized in such a way that the user has to make certain choices according to certain characteristics of the organism. Each step of the dichotomous key offers two choices (thus the name; dichotomous means: divided in two parts) until it points to a specific organism that has all the characteristics previously chosen.

Dichotomous keys are useful for identifying organisms in the field, or even in the lab when there is no other information available about the organism. Keys make come in diagram or in written form.

Here are two examples:

MLA: McGraw Hill. "Taxonomic Classification and Phylogenetic Trees." McGraw Hill Higher Education. The McGraw-Hill Companies, 2001. Web. 12 Aug 2010. .

Species Classification

There are so many different species on the planet that it's difficult to keep track of all of them. Scientists needed to find a way to classify each of them, and so taxonomy emerged.
Taxonomy is the science of identifying, describing, naming, and classifying living things. There are various ways of classifying organisms, but scientists currently rely on the Linnaean taxonomic system, created by Carl Linnaeus, a swedish biologist.

The Linnaean taxonomic system divides organisms into 7 major taxonomic levels called taxa: Kingdom, Phylum, Class, Order, Family, Genus, Species. However, there may be subdivisions like: subclass, suborder, etc. Each taxon becomes more specific as you move down the hierarchy of taxa. For example, many organisms may belong to the same kingdom, but not as many belong to the same phylum. Also, one is able to appreciate relationships between organisms using the taxonomic classification of each. Two species that share the same Order and Family are more closely related than two that only belong to the same order.

However, when naming an organism a binomial nomenclature. This means that when referring scientifically to a certain organism, one simply has to name the genus and species. For example, one would not write Atlantic salmon in a research paper, but would write Salmo salar.


MLA: Nixon, Joshua. "Scientific Names." Taxonomy. Michigan State University, n.d. Web. 12 Aug 2010. .

Chesapeake Bay

Chesapeake Bay is an estuary located in the west coast of the United States. It receives water from over 100,000 streams and rivers and empties in the Atlantic Ocean. It is home to around 350 species of fish, dozens of species of shellfish and crabs, 16 species of underwater grasses. Waterfowl, ospreys, and shorebirds also inhabit nearby areas.

All of these species interact in this ecosystem, and form a very complex food web (made up of many food chains). As explained previously, the food chain begins with a producer, which in this case is the phytoplankton, which is then eaten by a number of first consumers, which are then eaten by other predators.

The main purpose of the food chain is to see how energy is transferred from one organism to another. However, pyramids are ways to obtain more data. They represent graphically how energy, matter, and population are distributed in a system. Two of them are the pyramid of biomass and the pyramid of productivity.

The pyramid of biomass shows the amount of biomass at each trophic level, which is calculated by multiplying the mass of an organism times the amount of organisms. The dry weight of an individual is roughly the same as the energy it contains.

The pyramid of productivity shows the flow of energy over time. Since energy is lost as it moves from 1 trophic level to another, the upper levels are always smaller than the lower ones. Only 10% of the energy in one trophic level is passed on to the next one.

Trophic Levels

A trophic level is a hierarchical position that an organism occupies in an ecosystem. This is based on its source of energy. It is also known as feeding level. Trophic levels are represented through food chains, which show the flow of energy from one organism to another with the sun being the first source of energy.

Let's use as an example a food chain in a kelp forest. Here, the kelp would be the producer, which is eaten by blacksmith fish, who in turn is eaten by otters, who are then eaten by sharks.

The kelp is the producer and occupies the first trophic level. Being an autotroph, it is able to convert the Sun's energy into food for itself, and thus supporting the rest of the food chain.

Blacksmith fish would be the first consumers (herbivores), occupying the second trophic level. Otters are the second consumers (carnivore eating a herbivore), and are placed at the third trophic level. Finally, sharks are third consumers (carnivore eating a carnivore), and occupy the fourth trophic level. If we consider that when the shark dies it remains are broken down by bacteria, they would act as decomposers, placing them at a fifth trophic level.

Ecosystem Fun

An ecosystem is a community that interacts with its physical environment. This includes both biotic and abiotic factors.

Some examples of ecosystems include:

• Estuary: Found where a river meets the ocean, resulting in brackish water and a high biodiversity. Producers are submerged aquatic vegetation (SAV) and plankton. Animals consists of several species of fish, crabs, and invertebrates such as polychaetes and flatworms. Some birds, amphibians, reptiles and mammals inhabit the surrounding land areas.
  
• Coral reef: A highly productive ecosystem. Producers include phytoplankton and algae. Other organisms that can be found in a coral reef are sea anemones, sponges, clownfish, butterfly fish, flatworms, sea stars, sea urchins, shrimps, crabs, lobsters, sharks, rays, among many others.
  
• Desert: Have low precipitation. Low vegetation consisting mostly of deep-rooted shrubs. Animals are nocturnal and have adapted to the heat and scarce water availability.
  
• Rainforest: Abundant rainfall allows the growth of broadleaf trees. There are also herbaceous plants and shrubs. There is great biodiversity, serving as a habitat for a great variety of mammals, reptiles, birds, and insects. Some animals include the jaguar, chimpanzees, butterflies, lizards, macaws and boas.
  
• Grassland: The vegetation consists of a variety of grasses with a resistance to drought and animals are herbivores and some predators that feed on them.
  

What is a system?

A system is a set of components that function and interact in a certain way. Some key components of a system are:

• Inputs: These enter the system. (e.g. matter, energy)
  
• Outputs: These flow out of the system.
  
• Flows: These are materials passing through the system.
  
• Storages: These are where something, such as energy, is held in a certain part of the system.
  
• Sources: As its name states, it is where an input comes from (e.g. the sun is a source of energy)
  
• Sinks: This is where the output goes.
  

Studying the environment as a system helps us better understand the relationships between the different components and the causes and effects within that system.

Types of systems include:

• Open system: Both matter and energy are exchanged.
  
• Closed system: Energy is exchanged, but matter is not.
  
• Isolated system: Neither matter or energy are exchanged.
  

A common characteristic of all systems is synergy. It means that "the whole is greater than the sum of its parts." This occurs when two or more components or processes interact in such a way that the result is greater than the individual effect. This can be seen in things as simple as table salt and in complex systems such as the digestive or circulatory systems.

Hello ESS!

Environmental Systems and Societies is a course that challenges us to use critical thinking in order to form a well-based personal response to important environmental issues. This is achieved only through deep understanding of the interrelationships between environmental systems and societies.

As I progress in the second semester of this course, this blog will provide a space in which important and relevant topics can be discussed. It will also serve as an archive of my coursework throughout the following four to five months.