Summary: The Top-Down Effects Of Brine Shrimp On Algae

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Rodriguez Silva

The Top-down Effects of Brine Shrimp on Algae

INTRODUCTION An ecosystem is a delicate structure moderated by the network of interactions between all of the organisms that inhabit it. These organisms can be arranged into trophic levels, forming a chain or pyramid in which energy flows from one level to another. In a top-down trophic cascade, the higher-leveled consumers regulate and dictate the biomass of the trophic levels below (Leroux and Loreau 2015). The removal or addition of these consumers would initiate major changes in the survivability and overall diversity of most of the other species in the ecosystem. The balance between populations is maintained through natural growth and decline, predation, and resource

In a trophic system that is stable, most organisms are equally thriving, without any extreme stress or pressure to cause drastic population reduction as well as without limitless resources to allow unrestricted growth. A disturbance in the stability of a trophic system, or food web, could trigger a chain of reactions in which most, or sometimes all, of the trophic levels are affected. Some populations benefit from alterations in the system, but others suffer huge declines in numbers. Regarding consumer-driven effects, a change in consumer populations is often a product of immigration/emigration, development of prey adaptations against predators, as well as other biotic and abiotic factors, such as introduction of new species and weather (Evans 2011). In the case of an increase of a higher-leveled consumer, the trophic level directly below experiences intensified predation and rapid deterioration. The overpopulation of one species serves as an overwhelming pressure on other species that are either directly competing for resources or that serve as prey. In our experiment, we explore

The brine shrimp were hatched from cysts in seawater and placed in jars, and the algae were contained in large flasks of seawater in various concentrations, for everyone to access. The number of brine shrimp were our independent variable and the algae concentration were our dependent variable. We obtained 6 clean jars for our group in which we created our miniature ecosystems. We labeled each jar with our group name, lab section number, and replicate number. After deciding on what algae concentration we wanted to hold constant in our jars, we calculated the volume of seawater and algae solution required to achieve the desired algae concentration of 50,000 cells/mL and a total volume of 50 mL (C1V1=C2V2). We measured out the required volume of seawater with a graduated cylinder, pouring the contents into each jar. Because our calculated seawater volume was not a whole number, we utilized a micropipette to transfer the remaining amount of seawater. We then proceeded to collect algae from the large flask after carefully swirling around the algae to evenly distribute it within the water (Flipped Lab Videos 2016a). Using the micropipette, we transferred the appropriate volume of algae to the jars. We collected a sample of brine shrimp and added them to petri dishes in order to view them underneath a dissection microscope. Because we were testing the top-down effects, we decided on having