By Trevor Smith The kelp forest ecosystem is named as such because of the higher density of kelp. Kelp plants are large brown seaweeds that typically have three main features consisting of a holdfast, a stipe, and a blade (Noaa). The holdfast as its name suggests is the anchor of the plant, somewhat like tree roots except the holdfast does not absorb nutrients (Noaa). The stipe of the marine algae is the connector between the holdfast and the blades, somewhat like the trunk of a tree (Noaa). The blades extend from the stipe and are what allow to plant to take in nutrients and photosynthesize. Since it is crucial that these blades receive sunlight some kelp species have even adapted gas filled pneumatocysts that act as floats for the blades to stay up toward the surface of the water (Noaa). As shown in figure 1 there are kelp forests found all over the globe, typically in colder water that receives a significant amount of upwelling. This upwelling brings an incredible amount of nutrients for the kelp and other marine organisms to absorb. These kelp forests provide very unique and diverse habitats for a multitude of sea creatures. To obtain a better understanding of this habitat one must look into the main features that make the kelp forests unique, what organisms live and thrive in this habitat, and the status and threats to this habitat. The main feature of the kelp forests is the kelp, which in itself is not uncommonly rare. However, the large amount of kelp in one area is what allows the habitat to take on the uncommon role of being a nursery habitat. Being a nursery habitat it means that the kelp forests have a greater level of productivity per unit area than other juvenile habitats (Noaa). The reason for this higher level of productivity is the kelp provides protection from a multitude of environmental dangers (Kelp Forests). The kelp itself acts as a wave break causing slower and less forceful waves inside the kelp forest (Jackson & Winant, 1983). The kelp also provides shelter from predators, allowing juvenile organisms to survive into maturity (Noaa). Perhaps the main attribute that allows for such a high diversity in a small area is the fact that the kelp forests is divided into layers shown in Figure 2. This multilayered habitat allows multiple different species to exist in the same area while filling the needs of each organism. The kelp forest ecosystem not only provides shelter and protection in unique ways but is also a food source for the herbivores. The main herbivore feeding upon the kelp are sea urchins but there are many others including kelp crabs, isopods, gastropods, and herbivorous fish (Kelp Forests). As figure 3 indicates the food web in this ecosystem is diverse due to the sheer amount of different organisms living in this habitat. Obviously different kelp forests will have different species inhabiting them but Figure 3 presents a good look into how diverse the ecosystem is. Kelp forests not only feed the organisms that call it a home but sometimes other animals move into the kelp forest in search of food. These roving feeders include pelagic fishes and sometimes seals, sea lions, sharks, and even whales (Noaa). The keystone species for many kelp forests is the sea otter (Noaa). The sea otter is incredibly helpful to the ecosystem because it eats the sea urchin that feeds on the kelp. It also helps that sea otters have such high metabolic needs that they require a relatively high amount of food. Sea otters have also been seen wrapping the kelp around themselves like a blanket in order to stop themselves from drifting out with the tide (Kelp Forests). The sea otters are not alone in keeping the herbivorous kelp forest populations down, other predators include lobsters and large fish. However, when much of the predatory forces are overhunted or overfished for one reason or another it causes a multitude of problems for this ecosystem (Dayton et al., 1998). The kelp forest ecosystem is so diverse and unique that it may also hinder the ecosystem, since if even one pressure is applied too forcefully it can have catastrophic effects. The diversity and relative safety of the kelp forest makes the ecosystem a prime candidate for fishing as well as hunting. When the main predatory forces such as the larger fish are taken for food, or the sea otters hunted for the incredibly dense fur, it causes a major paradigm shift in the ecosystem. When herbivores no longer feel the predatory pressure their populations explode. This increase of herbivores, mainly sea urchins, results in over grazing of the kelp forest and may eventually lead to an urchin barren (Filbee-Dexter & Scheibling, 2014). This chain of events effectively kills the kelp forest with little hope of a resurgence without some sort of outside assistance. Problems in the kelp forest ecosystem are not only caused by the removal of higher level trophic predators. The kelp can be severely damaged by storms such as El Niño. The increase in the temperature of the water weakens and may even kill the kelp (Smale & Vance, 2016). While the increased wave activity can snap the stipes or even rip up the holdfasts of the kelp. The storms also decrease the nutrient inclusion that normally occurs with upwelling, further weakening the kelp (Smale & Vance, 2016). These are all normal occurrences in nature that the kelp forest can normally rebound from. If the kelp canopy is sheared off due to increased wave action the normally light limited species underneath will begin to flourish while the canopy repairs itself. However, the kelp forest ecosystem is typically also afflicted by pollution. The pollution causes the plants to weaken and not grow to its full potential or strength (Wernberg et al., 2016). All of these factors combined make it all too easy for the kelp forests to collapse into barrens void of the life that once flourished here. Kelp forests are habitats filled with a diversity rarely matched in other ecosystems. This diversity is caused by the unique features that are so prevalent in this ecosystem. These unique features allow the ecosystem to be a home to an incredible amount of fauna and flora. However, all of this diversity cannot protect this ecosystem from the various threats posed against it. With all of these threats and the decline of kelp forests in the past, there is a hopeful future for this ecosystem. The predators which were over hunted and overfished before are now protected to hopefully increase their numbers into non-threatening levels. Pollution has been made illegal allowing the kelp to strengthen. Some kelp forests have been made into marine protected areas, keeping them safe from multiple threats. Sadly, nothing can be done to protect against strong storms but with all of these other protective measures in place the return of kelp forests to their former glory seems assured. Figure 3. California kelp forest food web; From: http://qvcproject.blogspot.com/2013/09/ References Dayton, P. K., Tegner, M. J., Edwards, P. B., & Riser, K. L. (1998). Sliding Baselines, Ghosts, and Reduced Expectations in Kelp Forest Communities. Ecological Applications, 8(2), 309. doi:10.2307/2641070 Filbee-Dexter, K., & Scheibling, R. (2014). Sea urchin barrens as alternative stable states of collapsed kelp ecosystems. Marine Ecology Progress Series, 495, 1-25. doi:10.3354/meps10573 Jackson, G. A., & Winant, C. D. (1983). Effect of a kelp forest on coastal currents. Continental Shelf Research, 2(1), 75-80. doi:10.1016/0278-4343(83)90023-7 Kelp Forests. Retrieved October 27, 2017, from http://life.bio.sunysb.edu/marinebio/kelpforest.html Noaa Kelp Forests - a Description. (n.d.). Retrieved October 27, 2017, from https://sanctuaries.noaa.gov/visit/ecosystems/kelpdesc.html Smale, D. A., & Vance, T. (2016). Climate-driven shifts in species distributions may exacerbate the impacts of storm disturbances on North-east Atlantic kelp forests. Marine and Freshwater Research, 67(1), 65. doi:10.1071/mf14155 Wernberg, T., Bennett, S., Babcock, R. C., Bettignies, T. D., Cure, K., Depczynski, M., . . . Wilson, S. (2016, July 08). Climate-driven regime shift of a temperate marine ecosystem. Retrieved October 27, 2017, from http://science.sciencemag.org/content/353/6295/169
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