Giant Kelp
Giant Kelp are a type of macroscopic brown algae. They are characterized by having a holdfast, stipe, bladder, and blades. Two species of Giant Kelp frequently found along the Pacific coast of the United States are the Macrocystis integrifolia, a northern species and Macrocystis pyrifera, a more southern species. Macrocystis integrifolia resides in the area extending from central California all the way up to Alaska (U.S. Dept., 1985). It is the dominant species of kelp in Puget Sound and the Strait of Juan de Fuca (Schafer, 1998). Macrocystis pyrifera is found from central California down into the Baja of California (U.S. Dept., 1985). These giant masses of algae that extend from the sea floor up to the surface of the water make giant forests. The blades that reach the surface form a dense canopy. These kelp forests are similar to those of land in their importance for wildlife habitat. Giant Kelp are important ecologically as the sole component of the kelp forest, commercially in the production of algin, and economically as a possible future energy source. These three factors stress the broad significance of Giant Kelp.
Before diving into the importance of the Giant Kelp, a thorough explanation regarding the characteristics of the Giant Kelp should be given. Macrocystis integrifolia differs from Macrocystis pyrifera in that it is smaller, its holdfast is flattened, and it resides in the shallow subtidal (not exposed to the rising and falling of ocean tides) to intertidal (exposed to the rising and falling of oceanic tides) regions. Macrocystis pyrifera resides in the subtidal region and its holdfast is conical in shape (Waaland, 1977). Features common to both include a cylindrical stipe that is branched into long unequal parts as well as blades that are unilateral and appear shiny brown with corrugated sharply toothed edges (Guberlet, 1956). A single blade can measure 25cm to 35cm long and 5cm wide (Waaland, 1977). Pear shaped air bladders (floats) are present to keep the algae blade afloat on the surface. Giant Kelp prefer water 35ft to 50ft deep and they form great beds that can grow to encompass several miles in area (Guberlet, 1956).
Giant Kelp are characterized by both a microscopic and macroscopic stage. The macroscopic stage is the one most familiar and has the common kelp look. The macroscopic brown algae that are commonly seen are in the sporophytic stage. Sporophylls, or the part of the algae that produces spores, liberates them continually throughout the year and over many years. Production of spores occurs at the age of 9 months to 12 months. It can release as many as 76,000 spores/min/cm2. It is said to be perennial. These spores are transported away from the sporophyte by the water. The spores find an appropriate substrate and attach within a few hours of their release. The organism is now called a haploid gametophyte (makes sperm or eggs). It can be either multicellular (male) or remain unicellular (female). The gametophyte produces gametes within about two weeks. The sperm from the male gametophyte and the ova from the female gametophyte are released and fertilized. The zygote, now diploid, is microscopic. This embryonic sporophyte measures < 0.25 inches long. The embryonic sporophyte continues to grow making its holdfast, stipe, bladder, and blades. In simpler terms, the kelp releases spores which settle to the ocean floor releasing sperm or eggs. The sperm fertilizes the egg and becomes a new adult kelp.
Giant Kelp derive their energy by the process of photosynthesis. Photosynthesis occurs on all parts of the algae above the holdfast contrary to plants where it occurs only in the leaves. The Giant Kelp requires ample light, cool water, internal waves, and good translocation of photoassimilates (photosynthesis reactants) to the growing areas of the kelp. The temperature of water and nutrient content are inversely related. If the water is warm then there is lower nutrient content as opposed to if the water was warm and there were greater nutrients in the soil (State of California, 2000). Nutrient pulses are associated with internal waves (Zimmerman, 1985). Nutrients are not taken up by the holdfasts. Uptake is through the blades and requires this internal wave action to deliver the nutrients to all the blades (State of California, 2000).
Shifting sediments that can bury newly forming sporophytes and gametophytes contribute to the mortality of Giant Kelp. Wave driven projectiles accumulated during severe storms also account for some of their mortality. Storms and large swells can cause massive entanglements of the algal blades or completely tear the algae out of the substrate for which it is attached. Higher temperature water with low available nutrients limit growth and cause potential death. Black rot, a fungal disease, develops on the blades of the Giant Kelp if the temperature of the water is too high and causes its decay. Stipe rot is correlated with human sewage in the water. Animals such as sea urchins, fishes, amphipods, and isopod crustaceans can also cause mortality. Sea urchins are the largest threat to the survival of the Giant Kelp by devouring the holdfast (State of California, 2000).
Giant Kelp are ecologically very important because of their development of massive kelp forests. These forests lessen the effect of winds, water currents, and nutrient fluctuations. Watch closely when the wind blows over the water. You will see riffles form outside the kelp area and it will be as smooth as if there were no wind present in the center of the kelp area. The kelp forest also provides food, habitat, and a substrate for invertebrates, fish, birds, marine mammals, and plants (State of California, 2000). The kelp forest can be divided up into three types of habitats: canopy, stipe or midwater, and holdfast or seafloor. The canopy consists of mainly bryozoans (moss animals). In the midwater reside motile forms that are free to swim and climb and some sessile forms that are stationary. The holdfast may contain thousands of small animals and over 150 species (Bushing, 2000). Tissue of the holdfast is used as food and crevices make for a good hiding spot. It is also a good spot for the early development of urchins and abalone. Brittle stars are abundant also on the holdfasts. The invertebrates that the Giant Kelp harbor are prey for many fish. The forest also provides a hiding place for juvenile fish. Birds are benefited as well by not only the attached kelp but also drift kelp floating freely in the ocean and the kelp that has washed up on shore. The birds may perch upon the kelp canopy and scavenge for food amongst the blades by surface plunging. Mammals also utilize the Giant Kelp forests. In California, the sea otter, gray whale, killer whale, harbor seal, and California sea lion have been associated with the kelp. Sea otters wrap themselves in the kelp and use it as an anchor while they sleep. The forest is also a nursery area for female otters and their pups. The parent otters also use the kelp forest to forage for invertebrates within the fronds to feed their young. Gray whales use the kelp forest for protection from predation by killer whales on their journey with their young calf. They may also use this area to feed their infant. Seals and sea lions rest and also feed in the kelp forests (State of California, 2000).
Another importance of Giant Kelp is in commercial uses. Giant Kelp are harvested using an underwater mowing machine pushed by a motor driven barge. The mowing machine only cuts off the short-lived blades up to one meter from the surface. It leaves the long-lived holdfast intact to re-grow the fronds. This method of harvest supports a sustained yield throughout the years. A large amount of the kelp must be harvested because 92% of the organism is water (Guberlet, 1956). During WWI, 400,000 wet tons of the Giant Kelp were harvested each year in 1917 and 1918. It was used for making potash, a source of gunpowder and fertilizer. By the 1930�s an important algin extract industry surfaced. Kelco Alginates is the name of the first commercial harvester of kelp for algin in California. Algin is a mucilaginous intercellular (between cells) material found in kelp. This material is highly efficient in thickening, stabilizing, suspending, and as a gelling agent. It is used as an emulsifier to bind oily and watery liquids together. In this case, it prevents salad dressings from separating. Algin makes ice cream smoother and cake icings stiffer. It thickens more than 300 preparations from ice cream to paints, sauces, and toothpaste. Algin is also used in paper coating, sizing, and textile printing (Bushing, 2000). Algin is used in the art of reforming meat products into formations like nuggets or steaks. A series of steps are taken when converting kelp into a usable form of alginate. For example, in the processing of sodium alginate, wet chopped kelp is combined with sodium carbonate solution and this forms an alkaline extract. The next step is to separate out the kelp residue. The product is a sodium alginate solution. From here calcium chloride or an acid are added. If the acid is added it is termed the Alginic Acid Process and if the calcium chloride is added it is termed the Calcium Alginate Process (McHugh, 2003). Drying and milling proceed to form powder forms (See Appendix 3).
The third importance of Giant Kelp is the possible production of natural gas from the Giant Kelp. Ocean farms of Giant Kelp can be used as a future source of ocean-based biomass. These large ocean kelp farms could hypothetically supply generous quantities of natural gas in the form of methane. The process of fermentation by the kelp would produce the methane. Fuels have been produced in minute quantities during testing. A 400,000 hectare of ocean farm can produce 0.2 quads of gas which is 1% of total US consumption at 20 quads per year. A key problem of this hypothetical situation is the ability of getting all the nutrients needed to the kelp to fertilize them. This is a problem because the surface layer of the ocean water is devoid of nutrients while the deeper water is plentiful in nutrients. A fertilizing technique being tried is artificial upwelling using a pump to transfer nutrient rich deeper water to the surface waters. There is a test farm off the coast of California. The Department of Ecology and the Gas Research Institute support the ocean biomass project. What would be the environmental impacts of the ocean kelp farms? The large ocean kelp farms will reduce water circulation, dampen wind generated waves, and possibly slow ocean currents. Some project that these things in combination will have an effect on weather patterns. The kelp farms may also become sediment traps and will lower the chance of sporophytic attachment to the substrate. Pollution is also a possible problem. Human worker associated waste, wastes from machinery, and storm debris could increase the pollution level. The largest concern is the possible alteration of the ecosystem in that area. The upwelling of water to supply nutrients could also bring up fish, invertebrates, and bacteria too quickly causing them to die due to rapid pressure changes. Since these farms will take up quite a bit of space other users of the ocean must be considered. Some of the users to be considered include commercial fishermen, recreational fishermen, recreational boaters, coastal and local shippers, military activities, and dredgers and their disposal (Cannon, 1980). Many factors must be considered and studied before ocean kelp farming popularizes.
Giant Kelp forests are a rich source of biodiversity and its ecological role is unparalleled. They are a source of algin, a major commercial product. The forests also hold the key to a possible energy source. Although it may be seen as a nuisance to some, Giant Kelp hold much importance and will continue to on into the future.
Work Cited
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McHugh, D. 2003. A guide to the seaweed industry. FAO Fisheries Technical Paper 441. Available From: http://www.fao.org/documents/show_cdr.asp?url_file=/DOCREP/006/Y4765E/y4765e08.htm 2005 Feb. 25.
Shaffer, Anne J. Kelp Bed Habitats of the Inland Waters of Western Washington. Puget Sound Research 1998: 353-362. Available from: Washington Department of Fish and Wildlife. http://www.psat.wa.gov/publications/98_proceedings/pdfs/2c_shaffer.pdf Accessed 2005 Feb. 20.
State of California Department of Fish and Game. 2000. Giant and Bull Kelp Commercial and Sport Fishing Regulations. Sections 30 and 165, Title 14. [Internet] Available from: http://www.dfg.ca.gov/mrd/kelp_ceqa/chapter3.pdf. 2005 Feb 25.
U.S. Department of the Interior. 1985. The Ecology of Giant Kelp Forests in California: A Community Profile Biological Report. 85 (7.2).
Waaland, R. 1977. Common Seaweeds of the Pacific Coast. Washington: Pacific Search Press; 58-59.
Zimmmerman, R., Robertson, D. 1985. Effects of El Nino on local hydrography and growth of the Giant Kelp, Macrocystis pyrifera, at Santa Catalina Island, California. Limnology and Oceanography 30: 1298-1302.
