Critical Review 1
Competition between Chara aspera and Potamogeton pectinatus as a function of temperature and light
In the article “Competition between Chara aspera and Potamogeton pectinatus as a function of temperature and light” by authors Marcel S. Van den Berg, Hugo Coop, Jan Simons and Annemarie de Keizer, it was theorized that one type of aquatic plant may be a better competitor for sunlight than another plant that is more of a bottom dweller. They argue that “P. pectinatus and C. aspera have different growth forms and the canopy forming P. pectinatus may be a better competitor for light than the bottom-covering C.aspera.” to support this first argument. In addition they also put forth a second argument in that the bottom dwelling aquatic plant may, in the long run, be a better competitor in clear water as it may be better able to use sunlight in a more efficient manner and also due to its faster emergence in the annual life cycle of both plants, “The latter however, might be able to survive in clear water due to a more efficient use of light. Because both species have an annual life cycle, P. pectinatus might be outcompeted for light or space in Lake Veluwemeer due to the emergence of C. aspera earlier in the year.” The scientific team certainly does make a valiant effort to prove that this hypothesis is true and it can be deduced that the authors took great time in conceptualizing, realizing and working through the experiment and prove this for the most part but it does fall short in some areas.
The authors include a brief history of Lake Veluwemeer and give a concise overview of how eutrophication led to the survival of the P. pectinatus species within the lake and later C.aspera. They then go into the specifics of how the emergence experiment was set up and carried out. This is the first of two experiments conducted and revolves around the effects of temperature and length of day on the emergence of the two specified species of plants. The article then goes on to reveal how the second experiment was set up and conducted and revolved around light source competition between the two plant species. It was then explained how the data collected was processed and analyzed using a “statistical treatment” involving various logarithmic functions. The results were then presented for the two experiments with the emergence experiment first and then the competition experiment lastly. In general, plants emerged more rapidly at a higher temperature than they did at a lower temperature. It was also revealed that different planting techniques emerged faster than others and which type of technique ended up being more dominant to the conclusion of the experiment. The results of the second experiment were presented and confirmed that P. pectinatus was the larger plant species and, for the most part, thrived better in a more generous light area of the water (near the surface) due to its shape and size. Although it was noted that both plants had diminished growth and biomass in the lower light areas of the lake (near the sediment). Not surprisingly it was also determined that due to the canopy shape of C.aspera, the irradiance levels were drastically lower underneath the plant leaves. In the discussion section of the article, the data and results were reiterated and the authors then compared the results to their hypothesis. It was then stated that although the results should have shown that P. pectinatus outcompeted the plant species C.aspera, this was not the case. The results showed that C.aspera outcompeted the plant species P. pectinatus and there was no reason or theory given as to why this was the result of the experiment. It was noted that neither light nor early emergence explained this twist. Possible errors in the study were then given by the authors.
To start, the experiment and the execution were both a great design. There was...
References: Van den Berg, M. S., H. Coops, J. Simons & A. De Keizer, 1998. Competition between Chara aspera and Potamogeton pectinatus as a function of temperature and light. Aquatic Botany 60: 241–250.
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