Note: Descriptions are shown in the official language in which they were submitted.
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Bac~grou~d and Summary of the Invention ~ I
Freshwater and marine plants:represent important poten-
tial sources of food and che~icals. For example in the Orient,
;..
acroalgae are consumed extensively as a human food source while
; 5 1 in many areas of the world they are used for animal feeds, medi-
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. cine, an-mal feed suppiemen~s and fertilizers. In the United
States, ~acroalgae are presently used for the production of agar,
; i' algin, and carrageenin Current demand for these useful marine
and fresh~iater macrophytes greatly exceeds their availability,
ll a~ l~ast on an economical basis. A basic objective of the
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¦linvention, therefore, is to provide procedures and means for the
large scale commercial culture, on an economically feasible basis,
of fresh and salt water macrophytes.
I !
I Marine and freshwater macrophytes with which the invention
may be employed include macro forms in the Subkingdom I Prokaryonta
Division Cyanochloronta, Subkingdom II~ Chloronta, Division Chloro-
. phycophyta (green algae~, Phaeophycophyta ~brown algae),
¦Chrysophycophyta Xanthophyceae (yellow green algae), Rhodophycophyt
¦I(red algae), Charophytà (stoneworts)O Hydrophytic members of
Hepatvphyta (liverworts), Bryophyta (mosses), Pterophyta (ferns)
and Anthophyta (flowering plants) are also included in this in- j
ventionO
~. I . I
;~ 15 There is one fundamental underlying difference in culti-
~ Ivation technique among hydrophytic members o the various plant
Iclassification groups presented aboveO A number of plants derive
; Inutrition from the water i.e. Chondrus crispus (Rhodophycophyta),
Ricci.a natans (Hepatophyta), Azolla ~Pterophyta) and I.e~na (Antho--
` 20 phyta)O Other plants derive mineral nutrition from the bottom
sediments via anchored rhizomes or roots i~eO Watercress (Antho-
~ Iphyta)O Intergradations between the two physiological extremes
: are also knownO This lnvention may be employed for hydrophytes - 1i
1~ Iwhich derive their nutrition from the water or bottom sediments
.: 25 I'or some intergradation in betweenO
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Chondrus crispus and Gigartina stellata are a source of
carrageenin for commercial applications and are of particular
¦, interest in this invention~ If not found floating in their
1~ natural habitat they are found attached to a substrate no~ by a
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¦ root system but by a holdfastO Nutrients are not obtained from
the bottom sediments but from the surrounding waterO Often due to
water movement caused by tidal currents, wàve action and other
I forces, these plants are in constant motion which provides maximal
11 exposure to sunlight 2S well as water bearing nutrients.
1' I
¦¦ We have found that both Chondrus crispus and Gigartina
¦l stellata grow faster in water charged atmosphere than underwater
¦l under equivalent conditions and grow without attachment-as well as
¦~' obtain nutrients from the surrounding spray or mistO
,.~ 11 . . i
In accordance with the present invention, freshwater and
marine macrophytes are grown in a controlled, substantially closed
¦¦ atmosphere, in which the plants may be continually wetted by a
~` 15 ¦I mist or spray or the nutrient-containing water, either fresh or
marine, as the ca$e may be. This technique enables optimal con-
¦ ditions of light, temperature and nutrition utilization to be 1,
~;~ I maintained, resulting in greatly enhanced growth rates and harvest
!' I cycles as compared to conventional underwater teehninAues for
.~ ~ 20 1¦ culturing and harvesting. When freshwater or marine hydrophytes are removed from their native ~ueous habitat and furnished a
¦, quantity of water-borne nutrients by means of a spray or mist it ¦
¦ results in the ~ormation of a thin film of liquid on the plant
jl foliagec The thin film culture technique results in a significant
¦! improvement of nutrient utilization and growth rates are greatly
enhanced~ By comparison, prior efforts to stimulate the growth
, of macroalgae in their natural environment have proven to be of
¦, limited effectiveness, for several reasons: among them, efficient
I use of nutrient additives is almost impossible to achieve in open
j' water because of the necessity of dispersing sufficient quantities
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of costly fertilizer into a rather large volume of water, which
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typically may be subject to at least some degree of current 10~7
j which carries the nutrients away from the intended targets. In
addition, signifieant amounts of the fertilizer may be taken up
by weed species as well as the cultivated plants, often with un-
desirable results.
¦ Pursuant to one of the more specific aspects of the in- ¦
I vention, nutrient additions may be controllably imparted to the
¦ sprayed freshwater or seawater vehicle, not only to enhance growth
I rates but also to control the desirable product ratio of the
I
plantsD In addition to achieving greater nutrient efficiency, one
' ¦, may controllably impart to the sprayed freshwater or seawater
` vehicle plant growth substances, hormones, antibiotics J fungicides
and herbicides. After harvest, shelter sterilizing agents may be
` 15 l introduced prior to restocking the cultivar.
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The sun is man's primary source of energy and the amount
of energy which reaches the earth's surface is colossal~ Unfor-
il tunately, when light penetrates water it is subject to the excep-
1 tional light absorbing qualities of the waterO Even in trans-
parent water free of wave action significant amounts o~ sunllght
are absorbed in the upper layers of water, making limited light
¦! available for photosynthesis, particularly when solar energy is
~~ i relatively low due to variational solar radiation with the sea-
!.
l, sons and variable cloud coverO Thus, the;average efficiency with
which plants convert solar energy is low and as a result plants
store something like 0~1 to 0~2% vf available radiation annuallyO
Plants like the water hyacinth on the other hand may have a very `
il high conversion efficiency given sufficient radiation~ In the
I process of the present invention, cultivation of marine and fresh-
water hydrophytes in the atmosphere, supplemented by a fine mist ;
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or spray, enable greater effi.ciencies to be realized in the trap-
lping of solar energy, since less solar radiation absorption occursO
¦Thus, plants grown in the atmosphere in a spray or'mist environment
llwill receive more solar energy on a daily as well as seasonal basis
¦ In general, the apparatus o the invention includes a
transparent solar shelter, forming a substantially enclosed at-
. . lospheric environment having large roo areas exposed on an axis
suitable for achieving maximal solar radiationO Provisions may be
Illade for minimizing the effectiveness of the sunlight during times
of intense light, and for enhancing the sun's rays at low anglesO
ursuant to the invention, provisions are made inside the trans-
Iparent solar shelter for maintaining a rather constant fog or mist
f freshwater or seawater, supplemented by periodic additions of
15 j!nutrients and growth substancesO For the group of hydrophytes
hich require rooting in the sediments, the plants. are cultivated
. . on the floor of the shelter.in either a sediment or hydroponic cul-
l ureO For the group of plants which obtain nutrition from the
:~ ater, approFriate rack~ ~re ~rovided for holding those plants
2Q Iduring the growth cycle and, if desired, the racks may be in the
ature of rotatable cylinders or the likeO
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¦~ The use of a spray medium for mariculture has four signif-
Ilicant advantages over present aquacultural practices employing water
~in pools or underwater farming techniques. The most practical ad-
vantage is~less water is required (e.g., a cubic foot of seawater,
weighs approximately 1000 oz. while a cubic foot of air at 100%
relative humidity, 55 F and one atmospheric pressure contains 0.01
: oz. of water vapor). Therefore under theoretical conditions five
~ 30 lorders of magnitude less water is required resulting in a significan
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reduction in cost of heating and cooling. A process employing a
. Iwater charged atmosphere also allows for more uniform distribution
,.~ ¦of nutrients to the plants because the control of nutrients in the
~much smaller quantity of water, is far greater and significant
~¦economic benefits are thus realized~ Further, since the volume
of water employed is minimal in comparison to existing methods,
¦it is economically feasible to utilize filtration techniques, eOgO
ultraviolet sterilization and filtration for bacteria, fungi,
~ lphytoplankton and zooplankton, control of pathogens or symbionts, ¦
:~ ~ 10 li etcO ' I
¦l A further advantage of the use of a spray medium is that
the particle size of the spray can vary from micron size to rain-
drop size, and spray nozzles are readily available for this broad
Irange~ The new method can make use of several particle sizes, I
~` ¦depending on the desired effect. For example,.a fine mist can
¦be used for more effective nu-trient distribution, and large drop-
lets can be used to "wash" the plants for disease control or when i
t.~e~ acc~lmulate p~rticulate matter or extracellular metabolites
I,or organisms lightly attached or clinging to the cultivar~ More- ¦
over, if water mist is introduced at temperature A into an air .
! atmosphere at temperature B then the heating/cooling efficiency
` !1 is a function of heat transfer surface area. Therefore, the fine
¦ mist particle size is more efficient than the large particle size
1l in heating and cooling the water charged atmosphere for equivalent
masses of water.
For a more complete understanding of the above and other
~: ! features and advantages of the invention, reference should be madeto the following detailed description of preferred embodiments
and to the accompanyin_ drawings.
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Description of the Drawin~s
Il Fig. l is a simplified schematic illustration of one
¦,preferred form of controlled environment, transparent solar
ilshelter according to the invention, for use in carrying out the
1Iprocedures of the invention.
l l
Fig. 2 is a schematic view of a modified form of trans- ¦
parent solar shelter for carrying out the processes of the in-
Ivention.
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I ¦~ Fig. 3 is a highly simplified, schematic diagram illus-
¦!trating a typical piping system for utilization in the controlled
¦1 environment shelter arrangements of Figs. l and 2.
~; Fig. 4 is a simp1ified representation of yet another
I form of controlled environment transparent solar shelter utilizing
¦¦rotary, cylindrical racks for holding plants not requiring roots
¦ in the sediments during the growth cycle.
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Figs. 5 and 6 are simplified views ilIustrating further
details of the rotary cylindrical racks utilized in the arrange-
ment of Fig. 4.
Fig. 7 is a simplified perspective illustration of an
¦1 advantageous form of cellular roof panel, for utilization in the
controlled env1ronment she]ters according to the invention.
¦ Fig. 8 is an enlarged cross sectional detail as taken
llgenerally along lines 8-8 of Fig. 7.
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Description of Preferred Embodiments of the Invention
In the process of the invention, hydrophytes of the gen-
eral classes heretofore referred to are cultivated in the water
charged atmosphere, in an enclosed environment, rather than in
their natural aqueous environment. With reference to Fig. 1, for
example, a transparent shelter structure 10 may be formed of trans-
parent or translucent materials, including side walls 11, 12 and
a peaked roof structure comprising roof panels 13, 14. The orient-
~ ation of the enclosing structure 10 desirably is such that the
"~ 10 roof panels 13 are arranged on an axis suitable for achieving
maximal solar radiation.
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In the illustrated arrangement, the enclosure 10 is formedwith a base or grade layer 15 of stone aggregate, which provides
efficient drainage. Spaced above the stone aggregate base is
a rack structure 16. The specific structure of the rack is not
a part of the present invention, although it is a nontoxic, open
mesh-like structure which serves to support the propagates or
` cultivars above the grade layer, while providing for the relative-
ly free circulation of air in and about the plants and for the
drainage of excess liquid through to the aggregate base 15. For
rooted plants, the aggregate bed and rack structure ma~ be re-
placed by suitable sediments, and mesh may be used to support
and orient the plants in the atmosphere.
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Within the enclosing structure 10 there are provided a
plurality of spray heads 19, arranged to discharge a fine spray
or mist of the nutrient vehicle, which is typically freshwater
or seawater, depending upon whether freshwater or marine plants
are being cultivated. The nutrient vehicle, as will be discussed
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further, may be used in its as-received condition, or may be
selectively for~ified by the addition of nutrientsD In the par-
ticular arrangement shown in Fig. 1, the nutrient vehicle is de-
rived from an adjacent well 17 or submersible pump in a water body
` ~ 5 ~extending to an appropriate source of reshwater or seawater.
This water is directed by a purnp 18 to the various spray nozzles
19 located appropriately throughout the enclosure so as to enable
the entire plant growth to be periodically maintained with a wet
film of the nutrient vehicleO Drying periods may be desirable for
10 ¦ disease control.
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Since maintenance of uniform temperatures is significant
Ito efficient cultivation, provision is made in the process of the
invention for maintaining the atmosphere within the enclosure 10
15 Isubstantially in a desired or optimal range for the specific
hydrophyte under cultivation. We have found in our experiments
~` Iwith Irish Moss that the optimal temperature range is from 10
r~ Ij to 21C at Montauk, New York~ In warmer climates and seasons, l~
t is particularly important to preven~. water charge~ atmospheric
¦I temperature from changing quickly about a uniform optimumO A uni-
¦¦form temperature may be accomplished by utilizing water extracted
from-a deep well, as well water typically is extracted year around
r' i! at a uniform temperature, without any signiicant seasonal varia-
Il tion. When well water is insufficient, additional cooling means
' are provided~ In the arrangement illustrated in Figo 1~ an ex-
: ternal spray means 20 is provided, which sprays water on the
external surfaces of the roof panels 13, 14 for evaporative cool-
~, ~ ,, ingO Other appropriate means may also, of course> be utilized
.~ 1 for optimizing temperature.
Inasmuch as ex~essiveL~ intense sunlight can inhibit
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growth of some hydrophytes under propagation or cultivation, means
may be provided for reducing the intensity of light at certain
times~ For this purpose, a roof panel 13 may be provided interi-
llorly or exteriorly with 3~1 light control film or movable baffles
ll 21 which may be controllably positioned for reducing light inten- !
sity~ Such ba~fles may also be utilized for heat control in some
instances, as by providing the rotatably mounted baffles with
Ihighly reflective surfaces on one side ~nd-~ac~, light-absorbing
llsurfaces on the opposite sideO
:lo 11 !
, With reference to FigD 3, a suitabie distribution mani-
! fold 22 is provided, which leads to a plurality of spray discharge
nozzles 190 The primary input to the distribution manifold 22 may
ll be one of several incoming lines 23, 24, 25, depending upon the
¦ circumstances of location, season and the cultivar employed. For
I example, where seawater is available at the desired temperature
¦ levels, it may be introduced directly into the manifold 22 through
the inlet line 230 Where seawater is available, but at a higher
; lll t~mperature than des~red, i~. may be passecl first through a heat
Ijl exchanger 26 and then through an inlet line 25 into the distribu-
Il tion manifold~ The heat exchanger 26 may be supplied with heat
¦! exchange medium in the form of ground water from the well 17~ !
Where the ground water itself is to form the desired nutrient
1, vehicle, it may be introduced directly into the distribution mani-
' fold 22 through the inlet line 240 In some cases, it may also be
possible to use industrial waste wa~er or sewage effluents for
I nutrient enhancement. Typically, these would be filtered and then
introduced through an inlet line 27, passing through the heat
exchanger 26 and then into the distribution manifoldD
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¦l In the distribution manifold, provisions are made as
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¦lat 28-30, for the introduction of desired organic and inorganic
nutrients, as at 31. In the process of the invention, as carried
out in an installation reflected in Fi~s~ 1 and 3,~ non-rooted
l plants to be cultivated are established on the rack 16, supported
1, in the water chargecl atmosphere within the enclosed structure 107
A nutrient vehicle is furnished to the growing plant by means of
the spray nozzle 19, periodically activated to maintain a film of
Il liquid on the plant surfaces, while maintaining the relative
ilhumidity within the enclosure substantially at 100% (although it
¦¦may be desirable on occasion to permit the plants to dry out for
desease control purposes)O
During the daylight hours, the amount of sunlight reach
ing the plants advantageously is controlled as necessary, primari-
Ij ly to prevent or minimize excessive light intensity, which has
¦ been found to be inhibiting to growth, and also to maximize the
¦ light during periods of minimum intensity~ Likewise, external
cooling is provided, if necessary, to avoid exposure o~ the
~ants to te~.per~t~re significantly in excess of their opt.imal
I rangesO
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x Desired nutrients, such as nitrogen and phosphates,
¦I for example, are added into the nutrient vehicle, at the dis-
tribution manifold 22, shortly before the water is discharged
. 25 from the spray nozzles l9o Several highly significant advantages
are achieved from this method of nutrient applicationO First,
as compared to adding nutrients to a natural aqueous en~ironment,
~;- il the amounts required are less by orders of magnitude, such that
~ ll nutrient additions in accordance with the process of the in-
i:i 30 iI ven~ion are economically realistic. Secondly, the nutrients
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11~60Z8
are applied directly to the hydrophyte, so that the value of thc
nutrients is substantially realiæed. ~hen seeking to add nutrients
to the natural aqueous environment, it is often difficult to main-
,ltain the nutrients in the water in the vicinity of the cultivar
~for an adequate period of time to enable the hydrophytes to obtain
! significant benefit. In addition, in the process of the inventionj
the plant supporting rack structure 16 contains substantially only,
the harvestable plant, whereas the natural environment includes
¦Isignificant amounts of undesired "weeds"O When adding nutrient
Ito a natural body of water, the weeds as well as the desired,
¦harvestable plants are being fertilized, often with undesirable
results~
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¦ It is known that plant growth can be significantly encour-,
~` 15 laged by enrichment of the atmosphere with C020 For this purpose~
the invention contemplates controlled additions of C02 into the
atmosphere or water~ Ideally, gaseous C02 is discharged directly
into the atmosphere within the enclosing structure 10, through
¦Igas nozzles (not spe.cifica11y .shown)c In addition, nozzles 19 may'~
¦¦ be of an air-atomizing, liquid discharge type (conventional) such
¦Ithat the uniform discharge of the gaseous medium assists in atom-
,t lizing the liquid nutrient medium, forming a finer ~ist or sprayO
Typically~ the volume of gas required for this purpose may be sub-
stantially greater than the necessary requirements of C02, in
Iwhich case the gaseous discharge may constitute the desired
¦'amount of C02 diluted with ordinary air~ Further, siDce C02 is
a reactant required for pho~osynthetic activity, it may be de-
Il sirable to control the introduction of the C02 gas by means of
il a valve 32 which is responsive ~o the level of light within the
. 30 enclosure. The valve 32 can be set to terminate the flow of C02
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(but not necessarily the atomizing air itself, if utilized) when
the level of light is too low or efficient photosynthesis~ In
general, when CO2 enrichment is employed, it is controlled to
,lachieve a concentration of around 100-1500 ppm oE CO2 in the
S llcontrolled atmospheric environment.
In the structure 40 illustrated in Fig. 2, the entire
¦Iroof panel 41 faces on an axis suitable for achievin~ maximal
solar radiationO In other respects, the structure of Figo 2 may
I correspond to that of Fig~ lo When appropriate, similar reference
I numerals are employed to designate corresponding parts~
,l In any of the various forms of enclosing structure,
auxiliary structures may be provided for controlling sunlight
1l and/or temperature conditions. Thus, in the illustration of
, Fig o 1, a wind screen 45 may be provided along one or more sides
of the structure, for minimizing convective heat loss in the cold
¦ seasonsO Likewise, as reflected in the arrangement of Figo 2,
i a ~ight-reflecting structure 46 may be provided for enhancement
1 of sunlight in the colder seasons O The reflecting structure,
¦ if desired, be adjustable to enable it to be oriented in an
¦ optimum position with respect~to the height of the sun at a given
~imeO Additionally, any of the various structures may utilize
direct heat exchange means for controlling the temperature within
,I the structure. One such arrangement may include the provision
of an appropriate heat exchange network 47 (Fig. 3), which may
be made up of finned tubing, or example, and which can carry
either heating or cooling medium as the case may beO To ad-
1~ vantage, such a heat exchange network may be furnished with
¦I ground water from the well 17, to provide both cooling in the
warmer seasons and heating in the colder seasons, as desired.
In some temperate and southerly climates, the amount of
available sun]ight during at least some seasons is far greater
` in intensity than is either necessary or desirable for optimum
cultivation of the Ereshwater and marine hydrophytes contemplated
by the inventlon. Accordingly, provisions may be made, as re-
flected in Figs. 4-6, for movable supporting the plants, enabling
`~ them to be successively and periodically brought into position to
receive sunlight, and then returned to a more shaded location.
Where adequate sunlight is available for this purpose, it is
possible to increase the density of plant growth within a struct-
ure of given size, to improve the overall economics of the process.
'`~
In some cases, supplemental light may be desired to in-
'~ crease the growth cycle in periods of low natural light, and/or
where control over day length and photo period is desired. With
reference to Fig. 2, artificial lights 48 are located under the
rack 16 (or at any other desired location). Such lights may be
controlled by a timer T and light sensor S connected in series,
whereby if the light level is below threshold during the light
c~cle period, ~he natural light is augmented by the lamps 48.
, .
- With specific reference to Figs. 4-6, a structure 50 is
illustrated, which can be constructed along the lines indicated
in Figs. 1 or 2. Within the structure, there are a series of
plant-supporting racks 51, which are generally cylindrical in
; 25 nature and are mounted for rotation about their respective axis.
By way of example only, the cylindrical racks or drums, may in-
clude end support frames 52 at each end, between which extend
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cylindrical sections 53 of nontoxic mesh or netting 53, which
provide an open structure for the support and attachment of the
plants. Pairs of rollers 54 at each end rotatably support the
end frames 52. Each of the rotary assemblies is keyed to a shaft
55 which carries a sprocket 56 at its end engaging a common drive
chain 57. The chain 57 is driven by a suitable motor drive
arrangement 58, which is speed-adjustable to enable the racks to
be rotated at a controlled speed appropriate for the level of
sunlight. In the structure of Fig. 4, additional spray heads l9a
may be mounted underneath the racks 51, directly upwardly. These
spray heads may be pulsed on a periodic basis during the photo-
cycle period to facilitate periodic reorientation of the plants
to the light source.
The rotary rack arrangements reflected in Figs. 4-6 may
tumble the unattached plants to facilitate periodic rotation of
the plants to the light source thus enabling the growth density
to be increased within a structure of given size. The racks also
facilitate periodic harvesting of the mature plants from the racks
since the harvest may be removed in "containerized" units.
,
In Figs. 7-8, there is illustrated a particularly ad-
vantageous arrangement for controlling temperature within a trans-
parent solar shelter utilized in the process of the invention.
Thus, in Fig. 7, the reference numera:L 60 designates generally a
panel unit utilized in forming a roof panel of the enclosing
structures 10, 40 of Figs. 1 and 2. The panel 60 advantageously
is of a double skinned, ribbed construction, having an outer wall
61 (Fig. 8), an inner wall 62, and a series of relatively closely
spaced ribs 63 extending between and supporting the inner and
outer walls in the desired spaced relation. Adjacent pairs of
the ribs 63 also form extended, longitudinal channels through the
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panel, and these are, in accordance with the invention, connected
a~ the end oE the panel, such that adjacent longitudinal channels
64 are connected in series. A suitable commercially available
material for this purpose is Cyro double skinned acrylic panel,
~ 5 sold under the trade designation ~crylic SDP. The material of
the panel is, in accordance with the invention, formulated to ab-
sorb a percentage of the infra red energy of the sunlight. In
doing so, a portion of the heat energy of the sunlight is convert-
ed to heating of the roof panel 60. The panel itself is then
; 10 cooled by directing through the series-connected channels 64 a
flow of cooling medium, advantageously water taken from the under-
` ground well 17. To advantage, the flow of cooling medium through
::,
; the roof panel 60 may be controlled by one or more temperature
probes 65, 66, which regulate water flow from a pressure tank 67,
` 15 by means of a servo valve 68.
,
~ For operation in the cold seasons, when low outside
'~ temperatures prevail, rather than excessive light and heat, the
roof panel 60 may be emptied of the heat exchange medium during
the daylight hours, for maximum transmission of sunlight, and
then filled with the flowing medium during the dark hours, toserve as a heating medium at those times.
In many instances, it may be desirable and advantageous
,.., ~ .
to provide for the circulation of cooling or heating medium
through the series-connected channels of the roof panel 60 in a
:~ 25 closed loop system, including a groundwater heat exchanger 70.
When utilizing a closed loop system, the cooling or heating medium
'.:
m~y include appropriate additives, such as light-absorbing chemicals,
algacides or dyes, for reduction o~ light intensity and/or
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selective absorption of undesirable wavelengths. When using the
closed loop system, the groundwater serves only in a heat exchange
function and does not itself enter the panel 60.
We have observed plastic pipes, fiberglass, plastic net-
ting and various types of rope can be used as an effective sub-
strate for cultivating macroalgae propagates provided the substrate
is properly cleanedof oil, grease and dirt. It is necessary with
nylon rope to expose it for extended periods of time in the water
and then to repeatedly autoclave it. Once the substrate has been
prepared for our application we insert the substrate as a core
inside an expandable netting. We have found DuPont material "Vexar"
ideal for this application. Mature reproductive macroalgae are
then loosely packed in the netting around the core substrate and
placed in a conducive environment for growth. Af~er the propagates
become established and attached on the substrate core we remove
the adult plants and expandable surrounding netting and then place
the substrate core with the propagates in the transparent solar
shelter or the natural environment where they are cultivated
under the previously described growth regimen.
A polysaccharide complex known as carrageenin is a wide-
ly used hydrocolloid, which is now commercially derived from Irish
moss and other macroalgae. It is used as a food additive, for
example, and also has wide industrial uses. In accordance with
one aspect of the invention, the growth cycle of the plants may
be so controlled as to enhance the relative proportion of carra-
geenin in the harvested product. Thus, while plant growth is
greatly encouraged by nitrogen enrichment of the nutrient medium,
carrageenin levels in the plant are relatively low during this
active growth period. ~owever, after the plant has achleved a
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¦desired growth stage, the aqueous nutrient medium supplied to the
plant by the spray nozzles 19 is caused to be relatively depleted
of nitrogen content, resulting in a significant increase in the
~relative proportion of carrageenin in the plantO By way of ex- !
¦!ample, carrageenin content has been known to increase by as much
¦las a third when the plant is transEerred from a nitrogen rich
;medium to a nitrogen depleted mediumO
¦ An important advantage of the present invention results
Ifrom the ability to minimize effects of extracellular excretions
by hydrophytes. In nature, a variety of extracellular products,
l¦derived from photo assimilated carbon, are excreted into the
!j aquatic environmentO While these substances are not fully
lunderstood, it is known that at least some of them tend to inhibiti~
¦the growth of the plant. In the process of the present invention,
¦the effects of such extracellular products are minimized. More-
I lover, the production of such products may also be reduced by
proper control of the growing environment, in the first instance
~e~ause ~he pr~cess of the pres~nt invention furnishes aqueous
i nutrient medium in the form of a mist, fog or spray, the extra-
cellular release does not remain in the locality of the cultivar
¦ long enough to have as great an inhibitory effect upon growth as
when released into the surrounding aqueous body of a natural
habitatO Particularly where the water is delivered in relatively
25 ¦1 larger particle sizes, the extracellular products are rather
effectively dispersedO
¦ Three factors are known to control the distribution of
1 oxygen in wa~er. They are: (1) temperature and salinity, (2)
~I biological activity, and (3) currents and mixing processesO In
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the natural habitat many hydrophytes may be subjected to periodic
. ¦loxygen deficits if there is rigorous growth or assocîated biolo~i-
~` ¦jcal activity taking place in the waterO An important practical. lladvantage of the process of the invention resides in the fact,Ithat under atmospheric cultivation periodic oxygen deficits can be
~, Icontrolled easier because the rate of supply is not withheld by. Ithe delay oE di:Efusion of the oxygen into the waterO .We believe
jit is easier to supply large volumes of plant biomass with oxygen
; Ivia the atmosphere than by pumping air or oxygen into water~
~i~ 10 ¦jMoreover, under conventional underwater cultivation techniques in
¦tanks and pools, a misjudgment about o~ygen requirements can re^
sult in poisonous and unpleasant hydrogen sulphide fumes which a~e
ireleased into the atTnosphere and water `and ~7hich are both danger
¦ ous and extremely unpleasant to the cultivatorsO
'' 15 I . :
. Perhaps one of the most significant advantages of the
. ¦ invention is the ability to deliver nutrients or fertilizers to
. I the plants on an economical basisO Thus, when plants are.grown
. lintensively as an aquacultural crop they typically will rapidly
¦ deplete the water of essential nutrients, especially nltrogen and -
~ IphosphorusO In general, it is impracticable to deliver fertilizers
: I to plants being grown in a natural environment. In part, this is
because of the difficulty of maintaining the nutrient in the area
of interest, which is virtually impossible if there is any
¦~appreciable current flow or wave actionO Likewise, since the
.nutrient is dispersed in a large body of water, the amounts re-
quired to achieve effective results are excessiveO Apart from
ithe foregoing, it is difficult to maintain the fertilizer in
solution or suspension in the aqueous medium long enough to be
¦Iully effective. All of these shortcomings are overcome in the
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process of the present invention, wherein plants, naturally occur-
ring in aqueous media, are grown in the atmosphere and are supplied
with nutrients by a fine mist or sprav of the nutrient medium.
Where nutrient additions are desired, they may be added to the
basic water medium shortly before being sprayed on the plants, so
that the nutrients are not only utilized in a timely manner, but
they are efficiently directed to the plant. In addition, nutrients
; may be added in a controlled manner around app]ications of growth
regulators, hormones, herbicides, growth substances and disease
controlling agents.
Among the other significant advantages of the new pro-
cess, in providing for the cultivation of aquatic and marine plants
in a water charged atmospheric environment, are a high degree of
control over the growth characteristics of the plant. For example,
~ 15 light intensity may be carefully controlled, so as to be screened
during periods of excessive intensity and enhanced during periods
of lower intensity, achieving not only a longer growth period than
in the natural habitat, but providing for sustained optimal growth
rates throughout the period of photosynthetic activity. Tempera-
ture may be effectively controlled by employing a water charged
~,
atmospheric environment to maintain a uniform level of temperature
for optimum growth without quick changes about the uniform optimum.
When necessary or desirable, artificial light may be provided
and/or external heat, so that the normal growth season may be
significantly extended in many instances.
It should be understood, of course, that the specific
forms of the invention herein illustrated and described are in- ;
tended to be representative only, as many changes may be made
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therein withou~ departing from the clear teachings of the dis-
' closure~ Accordingly, reference should be made to the following
appended claims in determining the full scope o the invention.
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