JP2013009601A - Method for preventing and recovering color fading of laver algae - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for effectively preventing and recovering color fading of laver algae.SOLUTION: A color of color faded laver algae in a laver farm is determined by a L*a*b* color system to determine which of the nutrient impoverishment of nutrient salts comprising nitrogen, phosphorus and metal is the cause for a color fading phenomenon. Based on the determination result, a fertilizer containing causative nutrient salts of the nutrient impoverishment is fertilized in the laver farm, which is the method for preventing or recovering the color fading of the laver algae.

Description

  The present invention identifies early on the nutrient (nitrogen, phosphorus, iron, or a combination thereof) substance causing the discoloration of the laver body in the laver farm, and implements fertilization according to the causative substance. The present invention relates to a method for preventing and recovering discoloration of laver bodies.

  In general, laver algae is cultivated by pre-establishing a spider net in a sprout net, placing the sprout net on the sea at the beginning of autumn, and raising seedlings in a low water temperature period suitable for the growth of a sprout. Collect at the period. One of the factors that determine the quality and price of the collected laver body is “color”. Since the color of the seaweed body has the greatest influence on the quality, the seaweed body that has been discolored has a markedly reduced commercial value, and must be reused or disposed of for other purposes. In recent years, discoloration of laver bodies has continuously occurred in laver farms such as Ariake Sea, which has become a major social problem.

  As an influential cause of discoloration of this laver body, the poor nutrition of laver farms has been strongly pointed out (Non-patent Document 1). Poor nutrition means that microalgae (plankton) that coexist with seaweed bodies in seawater ingest nutrient salts and grow abnormally, so that nitrogen, phosphorus, etc. in seawater necessary for growth of seaweed bodies This is a phenomenon in which the concentration of nutrients in the water drops.

Therefore, in the laver farm, as a measure for preventing discoloration of the laver body due to such poor nutrition, the following measures are taken when a sign of discoloration is seen in the laver net.
1) A method of spraying liquid fertilizer and sewage to the farming site.
2) A method of installing a moderately effective solid fertilizer near the laver net (Patent Documents 1 and 2).
3) A method in which the discolored laver body is immersed in a high nutrient solution for a certain period (Patent Documents 3 and 4).
4) A method of supplying iron in order to prevent discoloration of laver bodies (Patent Document 5).
5) Prevention of the growth of plankton competing with the laver body (Patent Documents 6 and 7).

However, the present situation is that none of these methods is a fundamental solution for discoloration of laver bodies.
In other words, although the above methods 1) to 3) point out the eutrophication of laver farms as a probable cause of discoloration of laver alga bodies, and have taken measures against them, discoloration of laver algal bodies The countermeasures are not taken after identifying the causative substances. The discoloration of the seaweed body occurs even when nitrogen, phosphorus, or iron in seawater is deficient alone. The photosynthetic pigment that governs the color of the laver body is composed of green chlorophyll a, orange carotenoid, red phycoerythrin, blue phycocyanin, and purple allophycocyanin. Even if any one of these is reduced, the color of the seaweed is lost, but it has been found that the nutrients that cause the reduction of each photosynthetic pigment are different (Non-Patent Document 2). That is, phycoerythrin, phycocyanin, and allophycocyanin decrease more than other pigments in the case of nitrogen deficiency, chlorophyll a decreases in the case of iron deficiency, and all photosynthetic pigments decrease uniformly in phosphorus deficiency. To do.

  Before taking measures against discoloration of laver bodies, it is clearly determined in a short time whether the cause of discoloration is caused by nitrogen, phosphorus, or iron, and the cause nutrient substance is identified However, it is necessary to intensively apply this nutrient substance. However, such a viewpoint is completely lacking in the conventional measures against color fading. The supply of unnecessary nutrients to the sea area raises concerns about increased processing costs and the growth of red tide plankton due to excess nutrients.

  Next, the method 4) is expected to improve the color by supplying only iron as a measure for preventing discoloration of the laver body. However, the cause of discoloration of the laver body may be due to nitrogen and phosphorus, not just iron. Therefore, unless the causative substance of the color fading of the laver body is clarified, the supply of iron alone is insufficient as a measure for the color fading of the laver body.

  Furthermore, the above-mentioned method 5) is a method using a drug that inhibits the growth of microalgae (phytoplankton). However, there are a wide variety of phytoplankton in seawater. Even if they can be inhibited, the possibility of growth of other algae cannot be denied. Quantifying the impact on all types of microalgae requires enormous time and cost. According to such a method, it is considered that the nutrient salt is ingested by other microalgae resistant to the inhibitor and does not necessarily contribute to the growth of the laver body. There are also concerns about the impact of surplus inhibitors on the ecosystem.

Japanese Patent Laid-Open No. 11-169,001 JP 2002-84,904 A Japanese Patent Laid-Open No. 2-111,685 Japanese Patent Laid-Open No. 2002-300,819 JP 2010-259,450 JP Japanese Patent Laid-Open No. 2001-340,034 JP2003-265,058

"Oligotrophic seaweed and seaweed farming" Ocean and life, vol.181, 111-172, 2009 “Nutritional deficiency response in photosynthetic pigments and chloroplast microstructure of red alga Susavinori” Journal of Japanese Fisheries Society, vol.76, 375-382, 2010

By the way, as a method for determining the color loss of the laver body, a chlorophyll meter developed for the purpose of measuring the color of leaves of crops such as rice by a visual method (SPAD-502Plus). The color determination method based on the measurement value (SPAD value) measured by the above, and the color determination method based on the L ^* value of the L ^* a ^* b ^* color system have been adopted. There was a problem that proper fertilization could not be done because the causative substance of the fall could not be clarified.

  In other words, with regard to the color judgment of the laver body by visual inspection, it is highly dependent on the visual judgment of skilled workers, and since no numerical standard is provided, anyone can accurately determine the color loss. There is also a problem that it is difficult to train skilled people.

  Moreover, the SPAD value proposed recently is a numerical value indicating the content of chlorophyll a, which is a green photosynthetic pigment, and can be easily measured using a chlorophyll meter. There is knowledge showing correlation. This SPAD value is labeled with only one pigment constituting chlorophyll a, the chlorophyll a, and there is a strong correlation with the amount of chlorophyll a that the SPAD value increases as the amount of chlorophyll a increases. I know. Therefore, the SPAD value is to measure only the change in the amount of chlorophyll a, and it is possible to roughly determine whether or not there is a color fading due to chlorophyll a or the tendency, but other than chlorophyll a that Nori alga has The color fading due to the change in photosynthetic pigment cannot be judged. In addition, since the change in the photosynthetic pigment is considered to be caused by the deficiency of nitrogen, phosphorus, and iron, such SPAD value determines whether the color fading phenomenon of the laver body is due to nitrogen, phosphorus, or iron. It is difficult.

In addition, the L ^* value in the L ^* a ^* b ^* color system is an evaluation axis indicating the “saturation” of the Nori alga body. As it increases, the L ^* value increases. Therefore, it is difficult to identify the cause of eutrophication by the color fading determination based on the L ^* value of the L ^* a ^* b ^* color system.

Therefore, the inventors can quickly determine which of the nutrients of nitrogen, phosphorus, and iron is caused by the color fading phenomenon of the laver body in the laver farm, As a result of diligently investigating a method that can quickly and accurately fertilize and prevent the color loss of the laver body when it is discovered on the aquaculture of laver, Surprisingly, depending on the color determination based on the a ^* and b ^* values of the L ^* a ^* b ^* color system, the color fading phenomenon is caused by nitrogen deficiency, phosphorus deficiency, iron deficiency, or a combination thereof. In addition, it is possible to quickly and reliably prevent the discoloration of laver alga bodies by applying fertilizer to the laver farms with emphasis on the nutrients that caused this discoloration. And can also be recovered Found that were established present invention.

  Accordingly, an object of the present invention is to solve the above-mentioned problems that have been a problem in the prior art, and to provide a method for effectively preventing and recovering the color fading of a laver body.

That is, in order to solve the above-mentioned problems, the present inventors quickly and clearly determined whether the cause of discoloration of the laver body is nitrogen, phosphorus, or iron, and established an appropriate fertilization method. Is. Specifically, it is generally used for judging the color of industrial products after judging the presence or absence of color loss of a laver body by visual observation or the SPAD value used for the measurement of leaves of agricultural products such as rice. Quickly determine if the color loss of the green algal body is due to nitrogen deficiency, phosphorus deficiency, iron deficiency, or a combination thereof using the a ^* and b ^* values of the L ^* a ^* b ^* color system Fertilizer containing one or more selected from nitrogen, phosphorus, or iron that causes discoloration is fertilized on a laver farm, and the color of the laver body is recovered. A recovery method has been established.

The gist of the present invention is the following (1) to (13).
(1) For a laver body that has been determined to be a discolored laver body in a laver farm, the color of this discolored laver body is measured by a color determination method using the L ^* a ^* b ^* color system, and obtained. From the measurement results of the obtained a ^* value and b ^* value, it is determined whether the cause of the color fading phenomenon is due to the eutrophication among nutrient salts composed of nitrogen, phosphorus, and iron, and based on this determination result A method for preventing and recovering color loss of laver bodies comprising fertilizing fertilizer containing nutrients that cause undernutrition to a laver farm.

  (2) The method for preventing and restoring color loss of a laver body according to (1), wherein the determination as to whether or not the laver body is a discolored laver body is performed by a color determination method based on a SPAD value. .

(3) For the a ^* value and b ^* value measured by the L ^* a ^* b ^* color system color judgment method, the value when the a ^* value is 3 to 5 and the b ^* value is 10 to 13 is iron The method according to (1) or (2) above, wherein the iron content is fertilized in a laver farm, and the method for preventing and recovering color loss of laver bodies.

(4) For the a ^* value and b ^* value measured by the L ^* a ^* b ^* colorimetric color determination method, the nitrogen value is determined when the a ^* value is 0 or less and the b ^* value is 7 to 20. The method according to (1) or (2) above, wherein it is judged that it is a single deficiency, and the nitrogen content is fertilized in a laver farm.

(5) For the a ^* value and b ^* value measured by the L ^* a ^* b ^* color system color judgment method, the case where the a ^* value is 3 to 5 and the b ^* value is 7 to 9 The method according to (1) or (2) above, wherein the phosphorus content is fertilized in a laver farm.

(6) For the a ^* value and b ^* value measured by the L ^* a ^* b ^* color system color judgment method, the case where the a ^* value is 1 to 4 and the b ^* value is 4 to 7 The method for preventing and recovering color loss of laver bodies according to (1) or (2) above, wherein the iron and phosphorus contents are fertilized in a laver farm, with a complex deficiency of phosphorus and phosphorus being determined.

(7) For the a ^* value and the b ^* value measured by the L ^* a ^* b ^* color system color judgment method, when the a ^* value is 0 or less and the b ^* value is 3 to -1, And the method for preventing and recovering discoloration of the laver body according to (1) or (2) above, wherein fertilizer is fertilized with iron and nitrogen in a laver farm.

(8) For the a ^* value and b ^* value measured by the L ^* a ^* b ^* color system color determination method, nitrogen and when the a ^* value is 0 or less and the b ^* value is 3 to 7 The method according to (1) or (2) above, wherein it is judged that phosphorus is deficient in complex and fertilizes a nitrogen content and a phosphorus content in a laver farm.

(9) For the a ^* value and b ^* value measured by the L ^* a ^* b ^* color system color determination method, nitrogen is determined when the a ^* value is 0 or less and the b ^* value is −1 or more. The method for preventing and recovering discoloration of a laver body according to (1) or (2) above, wherein it is judged as a complex deficiency of phosphorus and iron, and each component is combined and applied to a laver farm. .

  (10) A modest solid fertilizer is applied to a laver farm for discoloration of a laver body caused by a single deficiency or a complex deficiency of nutrients composed of nitrogen, phosphorus, and iron. The method according to any one of (1) to (9), wherein the discoloration prevention and recovery method of the laver body.

  (11) The method for preventing discoloration and recovering laver bodies according to (1) to (10) above, wherein carbonated steel slag is used as a fertilizer for supplying iron.

  (12) The above-described (1) to (1), wherein a mild solid fertilizer in which carbonated steel slag is mixed with humic substances is fertilized against discoloration due to a complex deficiency of a plurality of nutrient salts including iron. (11) The method for preventing and recovering discoloration of laver bodies according to (11).

  (13) The mildly solid fertilizer is housed in a nylon mesh bag and placed at the bottom of the laver net, and the color of the laver body according to (1) to (12) is prevented. And recovery methods.

  According to the present invention, it is possible to quickly determine the nutrient salt that causes the discoloration of the laver body, to prevent the discoloration of the laver body, and to recover more quickly.

FIG. 1 is a flowchart for explaining a method for determining discoloration of a laver body in the present invention.

FIG. 2 shows L ^* a ^* b ^* color system a ^* values and b ^* when cultured in control, nitrogen-deficient, phosphorus-deficient, iron-deficient, nitrogen and phosphorus-deficient, nitrogen and iron-deficient, phosphorus and iron-deficient ^. It is a graph which shows the difference in a value.

FIG. 3 shows the difference in L ^* value of L ^* a ^* b ^* color system when cultured in control, nitrogen-deficient, iron-deficient, nitrogen and phosphorus-deficient, nitrogen and iron-deficient, phosphorus and iron-deficient. FIG.

FIG. 4 is a graph showing daily changes in the concentration of dissolved iron in water.

FIG. 5 is a graph showing daily changes in the concentration of inorganic nitrogen in water.

FIG. 6 is a graph showing the daily change of the phosphate phosphorus concentration in water.

In the following, a preferred embodiment of the method of the present invention will be described in detail based on the flow of the method for determining discoloration of a laver body shown in FIG.
First, in the laver farm, it is determined whether or not the laver body is discolored, but when it is determined that the color is clearly discolored visually, it is determined by the color determination method based on the SPAD value in particular. There is no need, and when the color loss of the laver body cannot be clearly determined visually, the color loss of the laver is determined by the SPAD value.

  Chlorophyll a which is a green photosynthetic pigment is also included in the chloroplasts of laver, the SPAD value indicates the content thereof, and there is a knowledge indicating the correlation with discolored laver bodies. . Specifically, the SPAD value of the laver body collected in the laver farm is measured, and, for example, the average value (n = 5 to 20) of 3 or less is determined to be discoloration.

Next, when it is visually determined that the color is fading or when the SPAD value is 3 or less, it is determined that the color is fading, and the next step is the L ^* a ^* b ^* color system. Measure the color using the color judgment method, identify the nutrients that are lacking in the laver farm, and apply fertilizer at the optimum blending ratio.

Next, a method for determining which nutrient salt is used from the color of the discolored laver body in the laver farm will be described.
The red-black color of Nori-algae is largely due to phycoerythrin (red) and phycocyanin (blue). Since the present invention evaluates colors in the L ^* a ^* b ^* color system, it can capture changes in the colors of red and blue, and can subdivide and evaluate the color loss of the laver body.

Here, the L ^* a ^* b ^* color system is one of color systems corresponding to human color vision and is used in a wide range of fields from industrial products to foods. The L ^* value is “saturation” and indicates the degree of white to black. The a ^* value indicates redness to greenishness in the “hue”. The b ^* value indicates the yellowish to blueishness in the “hue”. By representing each evaluation axis in three dimensions, the color of the object can be grasped as a position in the color space, and a plurality of colors can be easily compared. By expressing and quantifying the color fading characteristics of the deficient nutrients in the L ^* a ^* b ^* color system, the color fading from the color of the laver body, that is, the L ^* a ^* b ^* color system It becomes possible to identify the nutrients that cause this.

As a result, among the numerical values of the L ^* a ^* b ^* color system, the cases where the a ^* value is 3 to 5 and the b ^* value is 10 to 13 are judged as iron deficiency, and the iron content is focused on the Nori farm. Apply fertilizer. In addition, among the numerical values of the L ^* a ^* b ^* color system, the case where the a ^* value is 0 or less and the b ^* value is 7 to 20 is judged as a single deficiency of nitrogen, and the nitrogen content is focused on the Nori farm. Just fertilize. Furthermore, among the numerical values of the L ^* a ^* b ^* color system, when the a ^* value is 3 to 5 and the b ^* value is 7 to 9, it is judged that phosphorus is deficient alone, and the phosphorus content is focused on the Nori farm. Apply fertilizer.

Then, among the numerical values of the L ^* a ^* b ^* color system, the cases of a ^* values 1 to 4 and b ^* values 4 to 7 are judged to be complex deficiencies of iron and phosphorus, and the iron and phosphorus contents are cultured. Fertilizer should be applied to the place. Among each value of L ^* a ^* b ^* color system, a ^* value of 0 or less and b ^* value of 3 to -1 are judged as a complex deficiency of iron and nitrogen, and iron and nitrogen content are put into the laver farm Fertilizer should be applied intensively. Among the values of L ^* a ^* b ^* color system, a ^* value of 0 or less and b ^* value of 3-7 is judged as a combined deficiency of nitrogen and phosphorus, and the nitrogen content and phosphorus content are put into the Nori farm Fertilizer should be applied intensively.

Further, among the numerical values of the L ^* a ^* b ^* color system, the cases where the a ^* value is 0 or less and the b ^* value is −1 or more other than those described above are determined to be a composite deficiency of nitrogen, phosphorus and iron, and each of these components It is sufficient to fertilize the laver farm with a combination of

Next, a specific fertilizing method will be described.
The fertilizer to be fertilized against discoloration caused by deficiency (oligotrophic) of any of the nutrients consisting of nitrogen, phosphorus, and iron is not particularly limited, but is not liquid fertilizer Preferably, it is desirable to apply a mild (slow) solid fertilizer. This is because in the case of liquid fertilizer, depending on the weather and sea conditions, the fertilizer spreads into the sea immediately after fertilization, and there is a possibility that the laver body cannot be ingested. On the other hand, if it is a mild solid fertilizer, nitrogen, phosphorus, and iron are eluted over time, so the concentration of nutrients in the target laver farm can be kept constant over a relatively long period of time. It becomes.

The fertilization method of the solid fertilizer with respect to the nutrient salt which lacks is demonstrated using Table 1. FIG.
The mild solid fertilizer that supplies iron is not particularly limited as long as it is mild, but it is particularly desirable to use steelmaking slag that has been carbonized. Steelmaking slag generated from steelworks contains about 20% by mass of iron, and can be used as an inexpensive iron supply material. However, steelmaking slag contains about 1 to 2% by mass of f-CaO (soluble lime), and therefore has the property of easily raising the pH in water temporarily. For this reason, it is desirable to perform a “carbonation treatment” to obtain a “carbonated steelmaking slag” in which f-CaO is CaCO ₃ and to suppress the degree of pH increase of the elution water. Carbonation treatment of steelmaking slag can be carried out by bringing the steelmaking slag into contact with carbon dioxide or carbonic acid-containing water. By this operation, CaO becomes CaCO ₃ , and since CaCO ₃ is formed on the surface of the steelmaking slag, rapid elution of the remaining CaO can be suppressed. By applying such carbonation treatment to the steelmaking slag, a temporary increase in pH in the water area can be prevented.

  Furthermore, for color fading due to the complex deficiency of multiple nutrients containing iron, as a combined supply of nitrogen, phosphorus, and iron, we produced a mild solid fertilizer that mixed humic substances with carbonated slag, It is desirable to fertilize. The humic substances used here are preferably those obtained by converting thinned wood into humus, but in addition to this, it is obtained by fermenting organic matter, food residues, etc., and it is a fish meal rich in inorganic nitrogen and phosphorus. Etc. In the process of fermentation, organic matter is decomposed by bacteria to become inorganic matter. In the obtained humic substances, inorganic nitrogen (nitrate nitrogen, ammonia nitrogen) and phosphorus that can be easily ingested as nutrient salts by the sorghum body. Contains a large amount of acid phosphorus. These nutrients elute into the seawater of the laver farm and become a source of nitrogen and phosphorus. Humic acid, a kind of organic acid produced in the decomposition process, has the ability to form a complex with metal ions, forms a complex with iron ions eluted from carbonated steelmaking slag, and remains in seawater for a long time. Since it can exist as a dissolved state, the laver body can be ingested as iron.

  When the elution experiment was conducted by changing the blending ratio of carbonated steelmaking slag and humic substances, iron was eluted most efficiently when the mass ratio of carbonized steelmaking slag and humic substances was 2: 1. Even if the blending ratio of carbonated steelmaking slag is increased, there is no change in the elution amount of iron. From this, when mainly supplying iron, the compounding ratio (mass ratio) of carbonated steelmaking slag and humic substances and / or fish meal is carbonated steelmaking slag: humic substance (fish meal) = 2: What is necessary is just to mix so that it may become one. Of course, the mixing ratio of humic substances (fish meal) and carbonated steel slag can be freely changed depending on what nutrient nutrients are under-nutrition. When not only iron but also nitrogen and phosphorus are deficient, in addition to the basic composition (steel slag: humic substance = 2: 1), depending on the situation of eutrophication at the fertilizer farm Then, humic substances or fish meals may be added so that the concentration of nitrogen and phosphorus is sufficient to grow the paste (nitrogen: 0.1 mg / L, phosphorus: 0.01 mg / L). In the case of a single deficiency of nitrogen and phosphorus, humic substances or fish meal may be fertilized alone.

Nori-algae can be harvested within 30 days after the Nori nets on which Nori spores have grown are put on the Nori farm, but to maintain the iron concentration in the surrounding sea area at least 15 μg / L throughout the cultivation period. Contains a mild solid fertilizer in a nylon mesh bag and 1m ^It may be installed at a rate of 100 kg or less per ² . By storing the mild solid fertilizer in a nylon mesh bag and installing it in the lower part of the laver net in this way, the solid fertilizer can be easily removed by lifting the mesh bag after the laver culture is finished. In addition, it is possible to prevent deterioration of the water quality of the laver farm.

[Example 1: Identification of causative substance causing discoloration of laver body]
By removing any one or more of nitrogen, phosphorus and iron nutrients from the control medium (PES) used for cultivation of Nori-algae, the nutrients of these nitrogen, phosphorus and iron are removed. A single-deficient or complex-deficient medium in which one of them is deficient is prepared, the discolored laver alga body is cultivated using this prepared medium, and the decrease pattern of the photosynthetic pigment by the deficient nutrients is expressed as L ^* a ^*. It was examined whether it can be confirmed by a color determination method using a b ^* color system.

  The seaweed was cultured in a PES medium (control) obtained by adding a nutrient-enriched medium to filter-sterilized seawater for about one week in order to make the conditions uniform. Then, it moved to the culture medium except each nutrient salt, and prepared a laver body with a different discoloration pattern. In addition, as a medium, a PES medium having a composition shown in Table 2 containing abundant nutrients as a control was used, and a nitrogen-only deficient medium, phosphorus source (excluding only sodium nitrate as a nitrogen source from this PES medium) Phosphorus single deficient medium excluding only sodium glycerophosphate) Iron deficient medium excluding only ferrous ammonium sulfate, which is the iron source, and nitrogen and iron complex deficient medium excluding the above nitrogen source and iron source A nitrogen- and phosphorus complex-deficient medium excluding the nitrogen source and the phosphorus source, and a phosphorus- and iron-complex-deficient medium excluding the phosphorus source and the iron source, respectively, and nitrogen in only filter-sterilized seawater without the addition of the PES medium, A phosphorus- and iron-complex deficient medium was prepared, and a total of eight types of mediums were prepared for experiments.

Using each of the above-mentioned single deficient medium and complex deficient medium, the color of each discolored laver body cultured for 10 days was measured with a colorimeter (colorimeter CM-700d manufactured by Konica Minolta). In order to make clear and clear the color of the green algae body when measuring, we spread two sheets of the green algae body on the slide glass and sandwiched it between the other glass slides so as not to slip. . The measurement site was placed in the sample surface opening (diameter φ3 mm). The measurement conditions were a viewing angle of 10 °, a light source D65 (similar to sunlight), and a diffuse illumination method SCE (a condition that received only diffused light and was closer to visual observation). Measurement was performed at 5 to 20 locations per condition, and the average value and standard deviation value of each L ^* value, a ^* value, and b ^* value were determined.
The results are shown in Table 3.

Further, in the L ^* a ^* b ^* color system when cultured for 10 days using a medium of control, nitrogen deficiency, phosphorus deficiency, iron deficiency, nitrogen and phosphorus deficiency, nitrogen and iron deficiency, or phosphorus and iron deficiency a ^* value, b ^* difference values shown in FIG. 2, also shows the difference in L ^* value in the L ^* a ^* b ^* color system in FIG.

The results of a single deficient medium or a ^* and b ^* values of each color fading glue algal at 10 days after initiation of culture using the composite deficient medium, a ^* and b ^* values of discoloration glue algal deficient It can be seen that it is characterized by nutrients (see Figure 2). Compared to the control, it can be seen that the b ^* value does not change significantly with nitrogen deficiency, while the a ^* value decreases by about 7 and the redness is reduced. In phosphorus deficiency, both a ^* value and b ^* value decreased by about 2 or 3, green content increased and redness decreased. Iron deficiency decreased the a ^* value by about 1, and the b ^* value remained almost unchanged, resulting in an increase in green content. In phosphorus and iron deficiency, the a ^* value was reduced by about 8 and the b ^* value was reduced by about 4 compared to the control, and the color faded more than the iron and phosphorus deficiency alone. The a ^* value in nitrogen and phosphorus deficiency is 0 or less as in the case of nitrogen deficiency, but the b ^* value is smaller than in nitrogen deficiency and the yellowness is decreased. In the compound deficiency, both the a ^* value and the b ^* value were greatly reduced to about 13 and about 8.

Similarly, from the L ^* value of each discolored laver alga body on the 10th day from the start of culture using a single deficient medium or a complex deficient medium, it was found that the saturation increased in all experimental plots compared to the control, There was almost no difference due to the lack of nutrients (see FIG. 3).

From the above, it was found that the deficient nutrients that cause discoloration of the laver body can be determined from the a ^* value and b ^* value in the L ^* a ^* b ^* color system. Further, from the results shown in Table 3 and FIG. 2, in the L ^* a ^* b ^* color system, when the a ^* value is 3 to 5 and the b ^* value is 10 to 13, it is determined that iron is deficient alone, and the a ^* value 0 is less and b ^* determined that nitrogen alone deficiency when the value 7-20, it is determined that phosphorus alone deficiency when the a ^* value 3-5 and b ^* values 7-9, also, a ^* value 1 -4 and b ^* values of 4 to 7 are judged to be a composite deficiency of iron and phosphorus, and a ^* values of 0 or less and b ^* values of 3 to -1 are judged to be a composite deficiency of iron and nitrogen, and a ^* the value 0 is less and b ^* determined in the case of the value 3-7 composite lack of nitrogen and phosphorus, further, nitrogen in the case of a ^* value less than 0 and b ^* values -1 or more than the above, phosphorus, complex iron It was found to be deficient.

[Example 2: Prevention and recovery of discoloration of laver body by solid fertilizer installation]
Ten thousand liters of Tokyo Bay seawater is drawn into the two pilot plant experimental water tanks shown in Table 4 below, and the closed circulation between the experimental water tank and the water tank is conducted for one month, and nutrients (nitrogen) are added by phytoplankton contained in the initial seawater. , Phosphorus and iron) and prepared oligotrophic seawater. Thereafter, 60 kg of a mixed material of carbonated steel slag and humic substances (hereinafter referred to as “fertilizer”) was placed on one side. As a fertilizer, carbonated slag and humic substances were mixed at a mass ratio of 2: 1, and each 12 kg was put in a nylon mesh bag. The glue nets installed in the two water tanks were prepared by allowing shell spores to grow on a 0.7 m × 2 m net and storing them frozen. The Nori net was installed about 20cm higher than the low tide level so that it would dry out for about 2 hours a day. Drying was performed to remove phytoplankton and other algae attached to the net, as in the actual laver farm. Other than that, I fixed the four sides of the ladle net with PVC pipes, attached floats, and floated on the surface of the water. The water temperature and pH of each water tank were continuously measured. During the experiment, the seawater temperature remained the same as that off Futtsu, Tokyo Bay, where the laver farm is located. The pH was 8.0 to 8.3 as in the case of real seawater and was almost constant. In addition, seawater of each series was collected three times a week and analyzed for water quality (nitrogen, phosphorus, iron).

  The result of comparing the iron concentration in seawater with and without fertilizer over time is shown in FIG. A concentration increase of 9 μg / L was confirmed in 10 days immediately after installation. Thereafter, elution from the fertilizer continued and reached 15 μg / L on the 35th day.

  FIG. 5 shows the result of comparison of the inorganic nitrogen concentration in seawater with and without fertilizer over time. A concentration increase of about 0.18 mg / L was observed from the installation to the 10th day. Subsequently, the concentration in the aquarium decreased with the growth of the laver body and the proliferation of phytoplankton in the aquarium.

  FIG. 6 shows the results of comparison of the phosphate phosphorus concentration in seawater with and without fertilizer over time. Phosphorus was confirmed to increase in concentration by 0.06 mg / L by the 20th day. Thereafter, the high concentration was maintained with almost no decrease. Since the intake amount of phosphorus for both Nori alga and phytoplankton was 1/10 or less of nitrogen, the change in concentration was smaller than that of nitrogen.

  Nori spore germination was confirmed in two lines on the 16th day from the start of the experiment. However, on the 34th day, almost no algae bodies could be confirmed in the water tank without fertilizer. On the other hand, in the presence of fertilizer, it continued to grow steadily, and the leaf length reached about 1 cm on the 48th day.

  On the 50th day, the iron concentration in the water tank with fertilizer was less than 15 μg / L, and 10 kg of fertilizer was added to the basic composition (2: 1) of steelmaking slag and humic substances to supply iron. On day 58, the iron concentration reached 20 μg / L, and iron deficiency was resolved.

Thereafter, on the 64th day, the color fading of the laver alga in the water layer with fertilizer was visually determined and measured in the L ^* a ^* b ^* color system. The a ^* value was −0.71 and The b ^* value was 7.28, and it was judged that color fading was caused by nitrogen deficiency. Based on this result, when 2 kg of fish meal fertilizer containing inorganic nitrogen, especially ammonia nitrogen, was added, the color immediately recovered and on the 70th day, the a ^* value was 5 or more and the b ^* value was 13 or more. Recovered to the desired standard.

  As a result of collecting laver algae from a part of the laver net in the latter half of the experiment, in the aquarium with fertilizer, weighed 936 g (dry mass 93.6 g) from the entire 0.7 m x 2 m net, about 30 min in dry seaweed It turned out that it was able to cultivate to the quantity equivalent to the sheet.

Claims (13)

About the laver alga body determined to be a faint laver body in the laver farm, the color of this discolored laver body was measured by a color judgment method using the L ^* a ^* b ^* color system, and a obtained ^From the measurement results of the ^* and b ^* values, determine whether the cause of the color fading phenomenon is due to the eutrophication of nutrient salts consisting of nitrogen, phosphorus, and iron, and based on the results of this determination A method for preventing and recovering discoloration of Nori alga bodies, characterized by fertilizing fertilizers containing nutrients causing causative to a Nori farm.   The method for preventing and restoring color loss of a laver body according to claim 1, wherein the determination of whether the laver body is a discolored laver body is performed by a color determination method based on a SPAD value. About a ^* value and b ^* value measured by L ^* a ^* b ^* color system color judgment method, when a ^* value is 3 to 5 and b ^* value is 10 to 13, single deficiency of iron The method according to claim 1 or 2, wherein the iron content is fertilized in a laver farm. Regarding the a ^* value and b ^* value measured by the L ^* a ^* b ^* colorimetric color judgment method, when the a ^* value is 0 or less and the b ^* value is 7 to 20, the nitrogen deficiency is 3. The method for preventing and restoring color loss of laver bodies according to claim 1 or 2, wherein the nitrogen content is fertilized in a laver farm. For a ^* value and b ^* value measured by L ^* a ^* b ^* color system color judgment method, when a ^* value is 3 to 5 and b ^* value is 7 to 9, single deficiency of phosphorus The method according to claim 1 or 2, wherein the phosphorus content is fertilized in a laver farm. For the a ^* value and b ^* value measured by the L ^* a ^* b ^* color system color judgment method, when the a ^* value is 1 to 4 and the b ^* value is 4 to 7, The method for preventing and recovering color loss of laver bodies according to claim 1 or 2, characterized in that it is judged to be complex deficiency and fertilized with iron and phosphorus in a laver farm. Regarding the a ^* value and b ^* value measured by the L ^* a ^* b ^* colorimetric color judgment method, when the a ^* value is 0 or less and the b ^* value is 3 to -1, The method for preventing and recovering color loss of laver bodies according to claim 1 or 2, characterized in that it is judged as a complex deficiency and fertilized with iron and nitrogen in a laver farm. Regarding the a ^* value and b ^* value measured by the L ^* a ^* b ^* colorimetric color judgment method, the combination of nitrogen and phosphorus when the a ^* value is 0 or less and the b ^* value is 3 to 7 3. The method for preventing and recovering color loss of laver bodies according to claim 1 or 2, characterized in that it is determined to be deficient and nitrogen and phosphorus are fertilized in a laver farm. For the a ^* value and b ^* value measured by the L ^* a ^* b ^* color system color determination method, when the a ^* value is 0 or less and the b ^* value is −1 or more, nitrogen, phosphorus, and 3. The method for preventing and recovering color loss of laver bodies according to claim 1 or 2, characterized in that it is judged as a complex deficiency of iron, and each component is combined and applied to a laver farm.   A mild solid fertilizer is applied to a laver farm for discoloration of a laver body due to a single deficiency or a complex deficiency of nutrients composed of nitrogen, phosphorus, and iron. The discoloration prevention and recovery method of a laver body of any one of 1-9. As a fertilizer supplying iron content, discoloration prevention and recovery method of laver alga body according to any one of claims 1 to 10, wherein the use of carbonation steelmaking slag.   A mild solid fertilizer in which carbonated steel slag is mixed with humic substances is fertilized against discoloration due to a composite deficiency of a plurality of nutrient salts containing iron. The discoloration prevention and recovery method of a laver body as described in 2.   The mild solid fertilizer is housed in a nylon mesh bag and installed in the lower part of the laver net, preventing discoloration of the laver body according to any one of claims 1 to 12, and Recovery method.

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