Marine trophic cascade is an ecological concept that has attracted a lot of attention in the recent days owing to the increase in overexploitation of marine resources. It is paramount that we gain clear understanding of the impacts brought about by the changes in the food web. Other possible causes include the environmental changes brought about by the climatic changes such as the global warming effects. Recent studies have shown an increase in the overexploitation of the marine top predators that has the potential to initiate a marine trophic cascade. Various scholars have studied the subject and accumulated reports on the same. There is a general consensus on the existence of trophic cascades. More studies have been carried out on small scales and thus limited data exist on large scale impacts like in the open sea/ocean waters. However, a precise understanding on the findings in those experiments will shed light on the possible impacts on a large scale.
A paramount principle in any ecological system is that alteration of a particular component will have a trickle effect that will be felt across the system. In the marine life, that information on the food chain is used to gain insight into the possible trickle effect that can result from such disruptions. An example of such disruption is overfishing or establishment of marine protected areas that are meant to preserve certain species. Overexploitation of the marine resources has been named as one of the most prevalent form of disruption today. This is in form of overfishing, either for food or for leisure. Owing to the huge impacts that human have on the marine life; they are at times included as a trophic level (Pinnegar, et al.).
Pinnegar et al. reviewed 39 cascades from 21 locations spread throughout the globe in an effort to gain insight into the prevalence and extent of the effect. 19 of the locations were shallow and a hard substrata and were located in north-eastern and central-eastern pacific. There were no data from other parts of the world; an indication of how the phenomenon is not well studied in the open sea. In addition, there were gaps in the available studies and as well variations in the extent and methodologies. This is an indication that there is need for further studies in those regions and as well in the others. The lack of data and information will make it impossible for the researches to suggest possible interventions (Pinnegar et al.).
In another study, Casini, et al. attempted to gain an insight into the effect in a pelagic marine environment. The data was collected for 33 years and was able to demonstrate a four-level trophic cascade in Baltic Sea. The study showed that a decrease in cod had a direct impact to their main prey, that is the zooplanktivorous sprat and as well a top-down process on the biomass of zooplankton and phytoplankton. In order to control the harmful algal blooms in the sea, the focus should be on controlling the anthropogenic nutrient and preserve the structure of the upper trophic levels. This is a good example that demonstrates the importance of studying the trophic cascades as the insight is used to design response strategies and advice marine communities on better ways of conserving the environment and protecting marine life. However, this is another indication of how intensive the experiment can be in terms of the period of data collection and analysis (Casini, et al.).
In another study, Pace, et al. revealed some findings on the researches that have been carried out in the open ocean. This created a new understanding into the matter shedding light on the factors that accelerate or decelerate the transfer of the predatory effects. The study identified several factors such as the productivity of the ecosystem, compensation. One notable finding is that the trophic cascades are heavily influenced by human beings, thus inhibiting their ability to recover and restore the natural balance (Pace, et al.). In another study, Heithaus, et al. focused on the trophic cascade effects brought about by the decline of the top marine predators. The researcher attempted to elaborate on the need for a holistic approach in the decision to control the populations of the large marine species. The author rushes on the decision that are made based on the mortality rates in certain regions and sought to explain a deeper role of a predator. Once again, the author attempts to demonstrate the need for the policy makers to have a clear understanding of the trophic cascade effect in making critical decisions that affects the marine life.
Trophic cascade is a complex phenomenon that requires thorough study and strict analysis as a miscalculation can lead to a policy that can trigger another trophic cascade with devastating effects. An example is the northwest Atlantic Ocean where an increase in cownose ray abundance was thought to be a result of trophic cascade brought about by the depletion of coastal shark. This decrease was also thought to trigger the collapse of commercial bivalve stocks. This analogy is thought to be reason behind the campaign run in the region, (Save the Bay, Eat a Ray) targeting to conserve that species. A later study suggested that the timing of the decline in shark did not coincide with the increase in cownose ray. Also, the increase in cownace ray did not coincide with the depletion of commercial bivalves (Grubbs et al.).
It is therefore important for the researchers to get the data on temporal, demographics and distribution right in order to make the right decisions. There is also a need for more studies to be conducted on open water and in harmony to ensure comparability of the results.
Works Cited
Casini, M., et al. "Multi-level trophic cascades in a heavily exploited open marine ecosystem." Proceedings of the Royal Society B: Biological Sciences, vol. 275, no. 1644, 2008, pp. 1793-1801. Retrieved from <http://rspb.royalsocietypublishing.org/content/275/1644/1793>
Grubbs, R. D., et al. "Critical assessment and ramifications of a purported marine trophic cascade." Scientific Reports, vol. 6, 2016, p. 20970. Retrieved from <http://www.nature.com/articles/srep20970>
Heithaus, Michael R., et al. "Predicting ecological consequences of marine top predator declines." Trends in Ecology & Evolution, vol. 23, no. 4, 2008, pp. 202-210. Retrieved from <http://www.sciencedirect.com/science/article/pii/S0169534708000578>
Pace, Michael L., et al. "Trophic cascades revealed in diverse ecosystems." Trends in Ecology & Evolution, vol. 14, no. 12, 1999, pp. 483-488. Retrieved from <http://www.caryinstitute.org/sites/default/files/public/reprints/Pace_et_al_TREE_1999.pdf>
PINNEGAR, J.K., et al. "Trophic cascades in benthic marine ecosystems: lessons for fisheries and protected-area management." Environmental Conservation, vol. 27, no. 2, 2000, pp. 179-200. Retreived from <https://www.environment.gov.au/system/files/pages/4ac5dc59-1f14-4a01-9ded-b1cc63a05905/files/co17pinnegaretal.pdf>
