The primary focus of this experiment wasto observe the cause of marshes dying off. This could be seen from shifts onthe dense grass in the marsh to the unvegetated mud flats in the marsh. In theexperiment, the top-down and bottom-up effects were monitored to investigatethe cause of shift or die-off.
This experiment is significant because it would beconsidered the first experiment to explain the die off factors that are causedby top-down and bottom-up control instead of physical factors. There were cagetreatments implemented across the marsh to see if the hypothesis thatquestioned whether or not top predators would affect marsh productivity throughregulating herbivores was accurate. The cages did not allow entry from toppredators but did allow herbivores to go in and out. This was a way for theauthor to see total effects on predator exclusion.
Based on the results, it wasobserved that the unvegetated space in the cage treatments went up by over 150%when compared to the control treatments within one growing season. Due to theresults, the author concluded that top predators do control the marsh productivityby predation on the herbivore. The top predators have a positive impact onproductivity so when the Sesarma reticulatum are freed from predation, themarshes will die off in a matter of time. The paper can be considered a reliablesource of information because the methods involved in this experiment weredeliberate. Every factor that could possibly alter or affect the results wereaccounted and measured for.
An example would be the physical factors ofnitrogen composition and wave exposure, which were tested to see their effects.The data showed that eutrophication and wave exposure were not effectexperienced in this marsh, the authors results that revolved around the topdown controls affecting die off were reinforced. This study is applicable toecology since it is the first published experiment to provide evidence thattrophic cascade control is responsible for die-off.
Based on the results, theydisproved the thought that physical factors determined the die-off present inthe marshes. The paper is overall written in a concise manner because there arepoints stated and explained thoroughly without leaving the reader confused. Thefigures and photos provided in the paper also allow the reader to attain anunderstanding on the concept, which expand the effectiveness of the paper. Theresults are what make this paper strong since the results prove that thehypothesis is accurate by stating how herbivory increased by more than 100%,the biomass of the grass declined by more than 60%, stating how disturbancesfrom herbivory on the marsh increased by more than 95%, and how the unvegetatedspace went up by more than 150%. Overall, the results provided in this papershow that marsh die off has an important relationship with the rejection of toppredators.
Even though this paper is strong, thereare also weak parts to it that can be adjusted accordingly. At one point in thepaper, the author states that marsh recovering from die off resulted from themarsh where treatments were placed. This could have affected the results in theexperiment because it was not an entirely recovered area. It would’ve beenbetter to look at the die-off in a marsh that was not affected by die-off tograsp an idea that die-off would’ve took place just as rapidly in marshes thatare pristine.
There could have been more experiments on other marshes to setright this predicament but it would be a strenuous experiment to duplicate amarsh that is different compared to the one that was used by the author. Boththe methods and cage systems in this experiment were calculated for the marshthat was used so it wouldn’t be easy to copy anywhere else. Other than that,these weaknesses don’t take away the significance of this experiment and theconclusions about marsh die off being impacted by trophic cascade.