ultimate.ocean.ranch - THE ULTIMATE OCEAN RANCH Fujio...

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Unformatted text preview: THE ULTIMATE OCEAN RANCH Fujio Matsuda‘, Tom Tsurutani‘, James P. Szyperz, and Patrick Takahashi2 ‘ Pacific International Center for High Technology Research 2University of Hawaii Abstract Significant expansion of global food supply will require new advancements of similar impact to the Green Revolution. The Ultimate Ocean Ranch envisions enhancement of open-sea biological productivity through artificial upwelling of deep-ocean nutrients by means of ocean thermal energy conversion (OTEC); food products will be derived by management of integrated "floating grazing platforms," which could also enhance atmospheric carbon dioxide sequestration and net oxygen production in the photic zone. Some of the required technologies exist; some must be developed. Commercialization of the con- cept will be required; this in turn will require the fullest possible integration of value-generating activi- ties. We estimate, from typical ecological parameters and from some assumptions that can only be evalu- ated through research, that about $ 3.3 M in aquatic food products could be produced annually from the water-pumping capability of a hypothetical Ill-MW OTEC plant. This is not a large return on investment, but it precedes research and engineering development; other values will be generated. The urgency of the food problem and the lack of nullifying obstacles indicates further evaluation of this concept. I. Introduction production rate would require rapid and efficient recycling of limiting nutrient elements. This condition cannot be attained by human agency because natural systems, both forests and the open sea, sequester organic matter in detrital pools (forest litter and soil, deep sea detritus) having long residence times and absolute regeneration rates insufficient for significant expansion of production. Accessing the nutrients of the deep sea, on the other hand, is a potential means of expanding production of food protein with neutral or favorable impact on oxygen and carbon cycles, and a longer term of sustainability. The end—point vision of the Ultimate Ocean Ranch described here is one of intentional human geochemical impact: biological productivity of open sea areas will be enhanced through artificial upwelling of nutrient-rich with more than two—thirds of the harvest derived from fresh SUbSurface Seawater into ,the phoiic zone; fwd fiSheS an? waters in Asia. Total annual production of fish and shellfish Other prOduCts wm be derived by Integrated management 0 is slightly in excess of 100 million tons (FAO, 1998). Fhe "floating‘grazmg Platforms," WhiCh Create the upwell' New advancements of impact similar to the Green mg’ at Phe final S‘tage by meat,“ °_f ocean thermal energy Revolution and the ongoing expansion of aquaculture will Com/6mm (OTECL thus .brmgmg Into Prodtmlvc use the be required if the food problem is to remain Short of cold deep water underlying the unproductive but vast catastrophic. Land use for terrestrial food production snbtropical seas' .Aricmary benefits inelude pOtemiany competes with maintenance of forests, with potential enhanced carbon diox1de sequestration (detritus from new consequences to the global oxygen cycle. Expansion of food chains will sink beneath the photic zone), net oxygen aquaculture remains dependent on feeds containing fish meal prOduCuOn 1-“ the phone Zone’ and COOhng of the ocean - . - - - ‘ face over significant geographical areas which could protein derived from fully exploned capture fisheries. The W , . . . substantial increases of recent decades in aquaculture melhfy Storm formauon (NSF/ISTA’ 1990’ Takahashl’ production have not been sufficient to outpace population 1996)' _The mqmred Infomauon base required for CH“? a1 growth and demand, nor thus to prevent declining total evaluation of the complete concept does not now eXist. (capture plus culture/)1)“ capita production of aquatic food Intermediate stages. Will yield useful increments Iof food products and the consequent price macaw from untapped nutrient resources and generate the informa- Even with a presumption of future consensus on global “on base' food policy, there remains a limit to the potential for Developing ‘CChl‘Ologlts pmm 31mg a .poremlal production of food protein on the earth? Maximizing pathway to the end-pomt v131on, but critical questions stand Significant expansion of global food supply is an inevitable necessity; it will require productive use of untapped resources. World capture fishery landings increased through the 19803, but have since leveled near 90 million metric tons per year, the long-forecast maximum sustain— able yield. Landings have thus failed to increase with population and demand, and have declined on a per capita basis. Approximately two-thirds of the 200 important commercially fished stocks are fully or over—exploited. Many marine fisheries have been depleted, some to the point of economic extinction of the stocks, others having been closed in hope of recovery. Aquaculture now contrib— utes substantially (>20%) to global aquatic food production, O-7803-5045-6/98/$10.00 ©1998 IEEE 971 at the gateway and undoubtedly along the path. This paper briefly reviews some of the component technologies that will need to be integrated, and makes a preliminary estimate of production potential. 11. Component Technologies A. Open-Ocean Facilities The end-point vision of advanced upwelling mariculture systems is closer to "ocean ranching" (management and technological recovery of "unconfined" animal stock) than it is to fish farming with captive stocks. However, open-sea grazing platforms will probably require similar infrastruc— ture and culture support facilities to those of open-water aquaculture operations. Intensive photosynthetic production of biomass for larval rearing or other purposes may involve confinement of upwelled water. Cage culture facilities may be required if juvenile fish are grown to their optimal release size in cages, or when product fish are caged pending harvest. Floating platform technology for commercial aquaculture is reasonably well-developed; open- seaworthiness is a continuing development goal. Cages can be positioned tens of meters below the wave—influenced surface layer, with the ability for variation of depth. Most systems to date have been moored to the sea floor, but there are mooring-free designs in development. Culture facilities have not yet been integrated with the generally larger-scale hardware developments aimed at other purposes. Very Large Floating Structure (VLFS) technol- ogy may readily accommodate the requirements of the aquaculture component (NSF/JSTA, 1996). There are no large-scale OTEC deployments in the open sea, but designs exist, developed during the intense period of research and development in the late 1970s to early 19805. The develop- ing technologies of floating breakwaters will also be useful, particularly the concept of large circular breakwater struc- tures with central "lagoons" suggestive of oceanic atolls. Floating platforms of any type and size will attract fishes; a characteristic community will develop if a facility remains in place for a sufficient time. This phenomenon is used to the advantage of commercial and recreational capture fisheries by the deployment of anchored fish aggregation devices. The impact and potential utility of this aggregation effect on the neighborhoods of platforms will need to be assessed. B. Artificial Upwelling Artificial upwelling, along with ocean ranching, is a key technological concept to the end—point vision, because only by augmentation of the inorganic nutrient supply to the photic zone can there be enhancement of marine photo— synthesis-based food chains leading to harvestable protein. Oceanographers use the term "new" production for the portion of photosynthetic production derived from nutrients that have moved (however slowly) into the photic zone from below the base of the mixed layer, as distinct from 972 production supported by nutrient recycling within the mixed layer. Thus the upwelling mariculture concept aims to enhance new production in the sea. This decade's open-ocean iron-enrichment experiments, in which addition of iron at the sea surface stimulated productivity in the equatorial upwelling, suggest that further supplementation of artifi— cially upwelled nutrients might intensify the photic zone enrichment. Artificial upwelling can be produced by a variety of means. Existing land-based research facilities (in the U.S. Virgin Islands, at Kochi Artificial Upwelling Laboratory in Japan, and at the Natural Energy Laboratory of Hawaii) produce artificial upwelling with conventional pumps. A wave-driven artificial upwelling device has been developed at the University of Hawaii, which will permit small—scale examination of plume behavior and management strategies. Another upwelling strategy is illustrated by the Japanese work with artificial seamounts, in which artificial structures are placed in the way of natural ocean currents to bring deep ocean water to the surface. Ultimately, the "grazing platforms" will be powered by OTEC, which will draw water up from depths near 600 m with temperatures below 10 °C and content of nitrate and phosphate near 90% that of the deepest ocean depths. These nutrient concentrations are greater than those of the thermo- cline—depth waters that supply the world's natural upwelling zones, which in turn account for a major portion of world fishery production in a very small percentage of the ocean's area. The practical region of the world ocean for OTEC is approximately that of deep waters between the tropics, the actual area being affected by land masses and ocean currents. Both closed-cycle and open—cycle plants have been operated at the Natural Energy Laboratory of Hawaii Authority (NELHA) in Kailua—Kona on the island Hawaii, as research and demonstration projects by PICHTR. Although the more distant future for OTEC will likely lead to relatively large floating facilities, a nearer-term application may be in land— based plants of 1-10 MW capacity, designed for small island developing states and funded by international aid agencies. This might be examined as a collaborative means to initiate an upwelling mariculture platform trial. Although open- and hybrid—cycle OTEC plants generate fresh water and closed- cycle plants do not, the generated power will be able to produce sufficient water for the associated human staff or community with any OTEC strategy. The artificial upwelling concept has generated consider- able research literature, which contains speeifics pertinent to initial design considerations, biological experimentation on effects of enrichment of surface waters with nutrients from therrnocline depths, and pre- and post-deployment ecological surveys of OTEC test sites. Physical ' oceanography, including plume characteristics and behavior, has been addressed. Upwelled waters discharged near the surface of the sea tend to sink as they mix with surfacewater, and can be traced as water masses to their depths of equilibrium density. Such waters can move fairly rapidly away from an anchored source; it is possible, on the other hand, for a mobile facility to track the plume precisely, as was done for the iron experiments. Upwelled water can be purposefully mixed with surface water to control its mixing behavior. C. Ocean Ranching Ocean ranching is the second key concept to the end- point vision. Except for the case of salmon, ocean ranching is at present less well-developed technologically and commercially than confined open-ocean aquaculture. Ocean ranching is related to the idea of fisheries stock enhance- ment, in that ocean ranching also aims to take advantage of growth in the biomass of released hatchery stock, supported by the natural productivity of the sea. Ocean ranching differs in its inclusion of technological advantage in control or recovery of the stock. In the ease of salmon, their anadro— mous nature causes them to seek to return to the stream system of their origin, though they are typically captured en route. With other species, means to the advantage for recapture may include natural barriers, of water temperature for example, that keep organisms from dispersing from the stocking point unduly, and technological strategies for concentration and recovery (behavioral training for response to artificial stimuli such as sound). Much of the existing research is from Japan. Upwelled cold water potentiatcs temperature isolation of the stock; the renewable energy source is available for other recovery and harvest strategies. Near-shore ocean ranching necessarily involves issues of proprietorship, tenure, and shared use of ocean areas. These issues have not been addressed for the case of mobile platforms in the open sea. D. Species Selection Species selection and development for the fisheries products are critical for sufficient productivity as well as for consideration of impact on oceanic ecosystems. Upwelling is expected to produce “natural” changes in the species composition of the fertilized microbial communities. With artificial upwelling providing nutrients, food- chain efficiency of the product would be greatest for a readily harvested primary producer, such as edible macroal- gae. Seaweeds are not, however, a concentrated form of protein, and it is questionable that such a product could be competitive with present culture systems on and near the land. Food-chain efficiency with an animal product will be greatest with a planktivorous herbivore or filter-feeder. Whale sharks, under study at the Sun Yat Sen University aquarium in Kaohsiung, or presently—cultured herbivorous food fish such as rabbit fish, would be examined for feasible use in these systems. Their advantages include their ability to grow rapidly to desirable market sizes for food fishes. The fisheries productivity of the natural upwelling zones is derived from small planktivorous fishes (anchovies and sardines), some of which have been cultured. The depletion and decreasing reliability of the upwelling zones' capture fisheries, which produce fish meal used by the terrestrial and aquatic animal feeds industry, suggests a ready 973 market for filter-feeding fishes as efficient products of upwelling mariculture systems. Natural trophie position is by no means the sole determinant of a species’ potential for efficient aquaculture production. Numerous species, which in nature are carnivo- rous or omnivorous, have been developed for practical culture in open-water systems using fish meal- and fish oil— based feeds economically. Such systems, however, consume rather than enhance oceanic productivity of bulk foodstuffs, though they produce economic value. A small-fish produc— tion strategy could gain advantage from the facts that larvae and juveniles of most fish species are planktivorous, that some are likely faster-growing and more amenable to culture than the upwelling zone planktivores, and that these species are of high value even at small food portion sizes. Open— water oceanic fishes (mahimahi, tunas) tend to grow rapidly as a natural adaptation against predation in an environment devoid of shelter. The common optimization of harvest size vs. production cost in commercial culture production will interact intimately in these systems with feeding strategy. E. System Integration Commercialization, the only practical basis for expan— sion of the vision to significant scale, may well require the fullest possible integration of value-generating activities. An OTEC plant of sufficient size to substantially enhance the fertility in its vicinity will generate more power than is needed to support the aquaculture activity. Excess power could generate exportable hydrogen fuel. Platforms may well be large enough for profitable harvest of solar energy by photovoltaic cells. Secondary research uses would bring with them funding to defray overhead costs. The term "integrated farming" has been associated mainly with subsistence agriculture, but has begun to be applied to industrial farming. Integration concepts could be used on upwelling mariculture platforms to minimize organic discharges and grow additional crops by recycling carbon and nutrient elements in dissolved and particulate forms through further biological uses. Excess stock of phytoplankton may be used to culture filter-feeding organisms such as shelled mollusks; fishes other than the primary crop may be produced on excess zooplankton and non-living particulates, and possibly used as additional feedstock for the primary crop animal; other microbes may process dissolved organic matter, for example producing hydrogen as done by “purple non-sulfur” bacteria. A primary crop of fish produced on a grazing platform could have its feed supply supplemented with the by—catch of nearby capture fisheries, thus address- ing a global fisheries problem. F. Environmental Impact The potential environmental impact of the end-point vision is wide-ranging. Positive effects of artificial upwell- ing include increased photosynthetic production of oxygen, and sequestration of atmospheric carbon dioxide in the organic matter (product animals and wastes) of the enhanced food chain. Enhancement of photosynthesis is in itself of no net effect on the atmospheric carbon budget because the new organic matter is soon returned to the carbon dioxide form by respiration. Harvested fishery products will be respired by consumers ranging in size from human to microbial. However, the portion of the new organic matter that sinks below the thermocline will constitute a sequestra- tion of carbon and an enhancement of photic zone or atmospheric oxygen. Negative potential impacts include loading of the environment with superfluous feed materials, animal wastes, and products of human habitation of the platforms. Sinking organic matter, which has been an environmental problem to commercial cage culture in its impacts to both water-column and bottom environments, is of less negative potential in the deep open sea, and of potential benefit in carbon sequestration as noted above. However, the areal capacity of deep ocean water columns to process organic carbon is not well known in practical terms. Artificial upwelling in the open sea will change the species composition of the phytoplankton community. Such change will be advantageous, in fact necessary, for the useful enhancement of production leading to food, but may spread some distance from the platform. This is another factor in the need for understanding of plume characteristics. The genetic composition of cultured organisms released into natural waters for stock enhancement and ocean ranching may well differ from that of the natural stock. This phenomenon is advantageous for recognition of such organisms in catches and harvests, but creates concern that wild stocks will be modified by interbreeding with the cultured ones. Potential solutions include attention to renewal of diversity in captive gene pools by periodic wild capture and integration, and development of sterile stocks for release (which limits stock enhancement potential but is appropriate for ranching). III. Feasibility Discussion of the feasibility of the end point vision is necessarily speculative. We are seeking funding for an effort of some years’ length to assess the current status in detail and to plan an orderly approach to conceptual and engineer— ing development. In this section, we present theoretical approximations of yields and comparison with some from other sources. With the exception 'of section C below, quantities are chosen to make final yield estimates conserva- t1ve. A. Upwelling Pumping Rates Associated with OTEC Power Plant Capacity A 100—MW OTEC plant pumps approximately 500 m3 s'1 (= 4.32 x- 107 m3 d'l). As noted, lO-MW systems are more likely to be demonstrated soon than larger facilities. Calculations proceed from a presumed pumping rate of 50 m3 s'1 (= 4.32 x 106 m3 d'l), 0.1 times the rate of a 100—MW plant. 974 B. Deep Ocean Water Nutrient (Nitrogen) Resource and Its Rate of Delivery to the Surface Classical nutrient profiles (e.g., Sverdrup et al., 1946) and actual measurements made in Hawaiian waters show concentrations of oxidized nitrogen (nitrate plus nitrite) in excess of 30 11M at the presumed OTEC draw depth of 600 m (25 ttm at 600 m in the Atlantic; 20 11M at 300 m in the Pacific). The following series of calculations is summarized in Figure 1. 0 Concentration: 30 ttM x 14 g N mole“1 = 4.2 x 10'4 g N 1*1 = 0.42 g N m3 - Mass pumping rate: 0.42 g N m‘3 x 4.3 x 106 m3 d‘l = 1.8 x10“ g N d":1.8tNd'1 C. A Non»Conservative Assumption for Convenience It is assumed that 100% of this nitrogen is taken up by photosynthetic cells and enters the food chain. We do not know the requirements to accomplish this nor the most likely actual percentage. D. Efliciency Food chain transfer efficiency .(animal growth/food intake) is taken here at 0.2. In managed systems, marine plankton exhibit "gross efficiency of growth" in excess of 0.3; on the other hand it is traditional to estimate food chain transfer efficiency in nature at about 0.1. Described here is a "worst case" scenario, in which 2 transfers are required between the phytoplankton resource and the product fish. It is possible that a valuable herbivorous fish will be found to eat the phytoplankton, thus eliminating these steps. Until that is accomplished, this longer chain may be considered as a counter—balance to he optimistic assumption of 100% N uptake in item 3 above. E. Projection - If phytoplankton containing 1.8 t N are eaten each day by zooplankton, then 1.8 t N x 0.2 = 0.36 t N d‘1 is incorporated into zooplankton. If zooplankton containing 0.36 t N are eaten each day by small fish, then 0.36 t N x 0.2 = 0.072 t N d“1 is incorporated into small fish. If small fish containing 0.072 t N are eaten each day by the product fish, then 0.072 x 0.2 = 0.014 t N d‘1 is incorporated into the product fish. Taking the composition of the fish at N = 8% of dry weight and dry weight = 20% of fresh weight, then 0.014 t N d'1 / 0.08 = 0.18 t (1‘1 dry weight / 0.20 = 0.92 t (1'1 fresh weight. .mu E “33325: ,Ewmoz find 8 meEioaau BEES on ENE EwohE mm coaunuoa .2 swap—E = 232 E ‘mmoaoEoEoo .259 “8 5 ER: 3 335me 33.05% mm .53 2F 4x8 05 E @890ch mm 9059::me £15 £32 n.qu 53% um Egofifim wiwfiw n Mo 58353 380.85 A Mi Omzb >22 of n29... mEaEsa 35:52 E 39% £02 98321 E0: .398: $8 $8282.. :8: 55cm: skew F w®._0>_c.._m0 E0: hmvwcmb o\oON szFmEwa< com 2522 .0 I 98:39:”. 00¢ 55 __ I wa 9955: .: HH— w 99:28 .E E: N 90>_Emo .>_ D 12“ |_m_>m._ Gin—Om; m_._.<m ZOFODn—Omn. 975 0» If this yield is the daily mean for the year, the annual yield is 330 t y’l; at a hypothetical price of $10 kg‘l ($ 4.54 lb“), the annual revenue from fish culture from a 10-MW OTEC mariculture facility is $ 3.3 M y". Comparison of these outcomes with other work is most conveniently done in terms of annual yield of fresh weight per unit of water pumped. Groves (1959) used units ofg y‘l per cm3 s". Let us call this unit the Annual Yield Unit, AYU. The comparisons must also take account of the trophie level of the envisioned product. Here, the product fish are at trophic level IV, phytoplankton constituting level I, zooplankton level II, and the small fish level III. Alternatively, it may be stated that 3 transfers were required to get the product fish from phytoplankton. Above, we projected 330 ty'1 (= 3.3 x 108 g) from 50 m3 s‘1 (= 5 x 107 cm3 3“), giving a yield of 6.6 g y’1 per cm3 s'1 = 6.6 AYU. Groves (1959) estimated upwelling mariculture poten— tial at 10 AYU, with one fewer transfer. Reducing this estimate by the efficiency factor of 0.2 x 1 level gives 2 AYU. Given the uncertainties, this is an encourag- ing agreement with the figure of 6.6 AYU derived above. Bienfang (1970) began with observations of photosynv thetic rates in deep-water—enriched experimental bottles, projected hourly rates x 10 hours per day, and consid- ered two transfers. His estimated yield was 70 t y'1 from 10 m3 d'1 = 60 AYU. One additional transfer at an efficiency of 0.2 gives 12 AYU. In recent years, one would not project the photosynthetic rate by a factor as large as 10 hours per day. Daily light is approximated by multiplying mean hourly irradiance by about 6. Adopting this factor, Bienfang’s 12 AYU x 0.6 = 7.2 AYU, a very close agreement with this paper’s esti- mate, derived from a very different approach. IV. Conclusion The least-challengeable statement in this paper is its first sentence. The present and inevitably—increasing need for food demands consideration of solutions ranging from the mundane to the esoteric. We offer for consideration that the ideas and analyses presented here fail to exclude the Ultimate Ocean Ranch concept from the realm of possibility. Thus, its continued consideration and pursuit carry potential benefits, which will include significant learning pertinent to the primary problem. V. References Bienfang, P. 1970. On the potential of deep ocean water to increase primary production under surface light and tempera— ture conditions. Senior Honors Thesis, University of Hawaii. 976 Food and Agricultural Organization of the United Nations (FAO). 1998. World Wide Web site: www.fa0.org. Groves, G.W. 1959. Flow estimate for the perpetual salt fountain. Deep—Sea Research, 52209-214. Takahashi, PK, 1996. Project blue revolution. Journal of Energy Engineering, 122: 1 14—124. US. National Science Foundation (NSF) and Japan Science and Technology Agency (JSTA). 1990. Cooperative Workshops in Artificial Upwelling and Open Ocean Mariculture. US National Science Foundation (NSF) and Japan Science and Technology Agency (JSTA). 1996. International Workshop on Very Large Floating Structures. ...
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