Monday, November 28, 2011

A Parasitism, Predation, and Other Forms of Interactions in a Peaceful Pond

By Paul and Alexis

Nosehill. A simple park, or a complex ecosystem? Careful study of the intricate ecosystem present at Nosehill reveals an elaborate and sophisticated environment where a plethora of organisms dwell, feeding trophic levels throughout Calgary. This seemingly simple park contains some of the largest mammals found in Calgary, along with a multitude of birds and bugs. Study of the ecosystem and structures show that a multitude of interactions between species transfer energy and establish an advance community. However, exactly which species can be found at Nosehill? Many citizens in Calgary are unaware of any organisms smaller than their hand, yet dozens upon dozens of organisms dwell at Nosehill. From the multitude of organisms it is only natural that a complex but sturdy web of interactions is formed.
One of the most interesting areas at Nosehill is the pond located near the the John Laurie Blvd and Shaganappi Trail entrance. The multitude of microscopic organisms found lead way to a community where organisms smaller than a finger thrive. Organisms such as the water boatman and water strider can be found just on the surface on this intricate aquatic ecosystem. Leeches and diving beetles can be found under the surface living off plants and sometimes other organisms that they encounter. These organisms interact in mingle in unique ways, ranging from mutualism to predation to mimicry. Through this blog we will discuss the various relationships that have been established between organisms along with succession that would occur at Nosehill.
One of the most integral interactions that can be found at Nosehill is that of the predation reaction, where an organism consumes prey for energy. This interaction builds the stable ecological community we experience when we go for a serene walk through Nosehill, feeding organisms such as the  ducks, spiders and many members of the dytiscidae species. Although these predation interactions are often changing, they build upon careful symbiotic relationships between organisms. One such example of symbiosis is parasitism. Parasitism is the relation between organism in which one organism benefits (the parastite) while the other organism is harmed (the host). At the Nosehill pond, a parasitic relationship would be between organisms and the leeches we find at the pond. The parasite - being the hungry leech - is able to feed on the human therefore gaining a food source, ducks and cat tails are the hosts they attach on to, and therefore are harmed because consumption and transferred diseases would instigate the decline of the population. Thus, the population of the leeches would increase. This process is cyclic, the population of leeches will plateau and decline once the population of cattails is not great enough to maintain the consumption of leeches. As the leech population declines, the cattail population will increase due to less predation, and so on.
However the interactions we find at Nosehill are not always damaging to one of the participants. We find examples of mutualism and types of mimicry (Batesian mimicry) that allows both organisms or species involved to benefit. A unique example of this would be the mullerian mimicry of bees and hornets found there. Since both these organisms are harmful predators will start to avoid them, and due to the shared coloring of their bodies will avoid the other organisms as well. This benefits both species, and is considered mutualism, because once a predator encounters one of the similar looking dangerous species, it will learn to avoid anything with similar qualities. This also benefits the predator, because it isn’t putting itself at risk by attacking other dangerous organisms. Both organisms  Another example of this mimicry found at Nosehill is that between a robber fly and a bee.  The robber fly imitates the patterns found on the bee, causing predators who see it to avoid eating it due to likely previous experiences in being stung. In this case, the robber fly is able to benefit off the fear caused by the model bees without really harming the bees. This type of mimicry is that of Batesian mimicry, where a non-threatening organism (the mimic) copies the behaviours and physical qualities of that of a threatening or dangerous organism (the model). Batesian mimicry is therefore a type of commensalism, where one organism benefits, and the other organism is not affected (in that it is neither harmed nor does is benefit). This is because the mimic benefits - predators will generally try to avoid them since they resemble dangerous organisms, therefore the likelihood of survival increases. The model neither benefits, nor is harmed.
Interspecific and intraspecific competition were also discovered throughout the pond ecosystem at Nosehill, mainly between the plethora of plant species and organisms found. Although sunlight does not seem like a scarce resource for us, for many plants only the highest one may get the most sunlight. This leads to competition within species, such as the number of grasses and cat tails discovered, as well as competition between species, such as algae, seaweed often cat tails.       
The plants that obtain the most sunlight will be able to survive the best, grow the most and be most likely to reproduce. This leads to the ecological community we see at the Nosehill pond. However, this community hasn’t been as it is today for very long: a wide range of events and processes formed and established the community we see today. An early community we would see would be that of mainly grasses in a pioneer community. This succession would sprout mainly from the dirt already present due to the fact that Nose Hill was prairie land previously, causing this process to be secondary succession. The only primary succession likely to occur would be that from any completely destroyed ecosystems - caused mainly be roads - that have been replaced by any expansion in the area of Nosehill that may have occured. This series of succession-based changes - known as a sere - in a community would eventually lead to an ideal climax community in which further stages of succession would most likely not continue to occur. Since this community is most likely the final stage in succession, it is probable that the pond ecosystem at Nosehill hasn’t reached a climax community. If the pond ecosystem did reach a climax community however, a large amount of aquatic fishes and larger aquatic organisms would most likely exist. Unfortunately the only organisms discovered at the pond that were larger than a hand were ducks - showing that the Nosehill pond is most likely at a middle stage in succession.
However with that said, there seems to be an optimistic future for the Nosehill pond ecology. Events such as the addition of dog prevention signs around the pond - increasing the population of ducks found substantially - allow optimum development in succession stages, hopefully leading one day to an ideal climax community. This in combination with the stable interactions and habits - such as mimicry, commensialism and protective coloration - carefully established in the ecosystem will lead way to more organisms, hopefully leading way to a plethora of organisms being able to strive. However the pond ecosystem isn’t the only seemingly successful microecosystem so far. Stable forest and grassland habitats were discovered across Nosehill, showing promise for a bright future for not only this ecosystem, but for the environment of Calgary as a whole.

Figure 1. An image of the pond in the corner of Nosehill Park, beside the entrance on John Laurie Blvd. and Shaganappi Trail.

Figure 2 Leeches discovered on the leaves of cattails in the water on the shore of the pond

Figure 3. A duck found in the Nosehill pond, there aren't many large organisms like ducks, meaning that the Nosehill pond may not have reached a climax community yet.

Figure 4. Dr. Ted Pike standing beside the "No Dog" sign at Nosehill Pond

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.