Morphology and system of diatoms
Algae in Bacillariophyta have various forms. Bacillariophyta is a three-dimensional structure composed of single cells or groups of single cells.
Cell structure of diatom
The outer layer of diatom cell wall is siliceous and the inner layer is pectin, which is colorless and transparent. A large number of diatoms must have silicate components, and when fertilized with water, they cannot reproduce without the required nutrients. The special nutrition that diatoms need is silicate, usually sodium silicate. The cell wall of Bacillariophyta is composed of an upper shell and a lower shell, so it has two surfaces when observed. One is the shell surface (top view), which is mostly oval and round from top to bottom, with some lines, lines and edges on it. The other is faceted, rectangular or square, not a cell, but two or three cells connected together.
Diatom cytoplasm is yellow-brown pigment body, which is mainly composed of yellow pigment and chlorophyll, and it is flaky and discoid. The assimilation product is fat, and the amount of fat is related to nutritional status. Cells have no flagella, and germ cells may have flagella. Diatoms have only 1 nucleus.
Classification of diatoms
Diatoms are mainly classified according to the symmetrical points on the surface of cell shells. The Central Crustacea is symmetrical with the center, which is mainly divided into five orders: Cirsium japonicum (Cirsium japonicum, Linear Algae, Microcystis), Rhizoctonia (Rhizoctonia) and Cladosporium (Cladosporium, Chaetoceros). Pinnate crustaceans are symmetrical on both sides, which are mainly divided into fistulas (reproductive gland phylum, Phaeophyta, Chaetoceros, algae and plankton), fistulas (navicular algae, pinnate algae, Curvularia, Porphyra) and fistulas (Nitziaceae, Diptera).
Orthophyta: Cells are spherical or cylindrical, connected by shell surface into chains or beads. The shell surface is round, the cells are thick, and there are fine points or pores. Some species have a linear annular overflow on the junction zone, which is called annular groove, also called transverse groove, and the groove overflow between two cells is called pseudo-annular groove. We can often see the banded surface of this algae instead of its shell-like surface. It looks like filaments, but there are grooves between filaments, lines on the cell wall and thorns in the terminal cells.
Cirsium japonicum (Genus): A common species in seawater. The cells are mostly disc-shaped and the holes are hexagonal, which makes the holes round. The holes are in the center of the shell surface, sometimes thick and arranged like roses, which is called the central rose area. Sometimes there is a small non-grain area in the center, which is called crack, and a large one is called central non-grain area. The edge of the shell is called the periphery, and there is often a circle of small thorns between the outermost holes. Pigments are small and numerous, granular or flaky, and are on the periphery.
Microcystis: Microcystis is an algae cultured in aquaculture ponds, most of which are single cells, and a few species are connected into straight or spiral filamentous groups, with shell surfaces and spherical points, lines and edges. Cyclops can reproduce at 4~5℃. We have done experiments in Dalian sea cucumber circle, and there are cases to follow up.
Coleoptera Thalassiosira: The cells are round, connected in a string by colloidal wires or buried in colloidal blocks, and the population rarely lives alone. There are spots on the shell surface, small thorns on the edge of the shell, and obvious interspecific bands, which are ring-shaped or collar-shaped. It belongs to offshore planktonic species and is an important species in nursery. Skeletonema is a lens-shaped cylindrical cell with a diameter of 6-7 microns. The shell surface is round and drum, and the cells form long chains by fine spines. The number of spines varies greatly, from 8 to 30, and the length of intercellular space is also different. The spots on the shell surface are very small and difficult to see. It is a common species in seawater.
Rhizophyta (genus): single cell or chain group, long cylindrical cell, oval to round cross section, flat, slightly convex or extremely slender conical protrusion, with thorns at the end, piercing into adjacent cells to form a chain. There are few kinds of fresh water and many kinds of eutrophic water.
Chaetomium family of Synechocystis: the shell surface is oval or nearly round with two angles. The torus of the shell is quadrilateral (common surface) with two obvious transverse stripes. There are about 400 species of Chaetoceros, which may be the largest genus of marine planktonic diatoms. It is difficult to identify different species in Chaetoceros. Many people are classifying this huge genus into subgenus, but this work is still going on. The discovered species are mainly distributed in the northern hemisphere. Because Chaetoceros is distributed all over the country, there are species distributed in tropical areas that have not been found.
Box algae: the shell surface is oval, and the surface is like a bag of flour, almost cylindrical. There are protrusions at both ends, and there are often small holes on the protrusions that can secrete colloid, which can make cells connect into zigzag groups. It is one of the common species in seawater.
Stellate genus: usually found in large reservoirs. The cells are rod-shaped, with different lengths at both ends, and the population is star-shaped, with thin shell lines, swollen at both ends and thin in the middle.
Needle algae without shell: it occurs in large quantities in fresh water, with a needle-shaped shell and a rectangular strip-shaped surface. The cells are long, and the planktonic species are single cells or radial groups.
Chaetomium: Cells are rod-shaped with different shapes at both ends. Cells are single cells or connected by gelatinous stalks, forming zigzag or star-shaped groups.
Seascenedesmus: The cells are rod-shaped, with round shell and equal ends, and one end of the cells is connected to form a sawtooth colony. Nematodes, marine species.
Platymonas: The cells are usually Z-shaped or star-shaped, the shell surface is rod-shaped or linear, the middle is swollen, and the two ends are slightly swollen.
Dictyophora: Common in fresh water, with swimming cells and no bands, it has two pigment bodies, one on the left and the other on the right.
Pinnate diatom: It is a common species in fresh water. Its shell is oval, with straight edges and round ends. Some species have slightly enlarged middle parts and long surfaces. The patterns on the shell are mainly thick ribs and two pigment bodies.
Phaeodactylum tricornutum has three different forms: oval, spindle and triangular radial, which can be transformed under different environmental conditions. For example, under normal liquid culture conditions, most of them are triangular radial cells and a few spindle cells, both of which have no siliceous cell walls. The length of triangular radial cells is about 10~ 18 microns (the vertical distance between the two arms), and there is a nucleus in the center of the cells, which contains 1~3 yellow-brown pigments. Spindle cells are 20 microns long and the ends of both arms are blunt.
Skeletonema bicuspidata: Single cell shell has obvious dorsal and ventral sides, the dorsal side is convex, the ventral middle is straight or slightly convex, and the crescent-shaped lines, points and edges are common in fresh water.
Bivalves: the shell is rod-shaped and trapezoidal, and one end is thicker than the other.
Nitzschia: cell spindle, boat, diamond, etc. The shell surface is straight or S-shaped, linear and oval, with horizontal lines or points. There are shell seams on the edge of the shell. There are generally two chromosomes. There are many species of this genus, which are widely distributed in fresh water, seawater and brackish water.
Dictyophora: Single cell with a linear, oval or ovoid shell surface and a contracted middle part. There are keel protrusions on both sides and shell seams on them. There are transverse ribs and fine lines between ribs. An elongated or wedge-shaped surface. There are many kinds, living in floating, fresh water, seawater and brackish water.
Ecological distribution of diatoms
Diatoms belong to wide-temperature type, like water with lower temperature, and grow vigorously in spring and autumn; Like silicate water, various trace elements and ions, so in diatom culture, amino acid fertilizer or organic fertilizer is not the fertilizer needed for directional culture; Like running water, clear water with high transparency, such as sea cucumber culture, needs high transparency water.
Relationship between Diatoms and Aquaculture
Diatom is one of the main producers of marine organic matter. Algae is the initial primary productivity to produce any kind of organic matter on the earth, so the primary productivity of aquaculture water comes from algae, while fish, shrimp and other species cultured in the later stage cannot achieve the maximum benefit without primary productivity to provide nutrition. Therefore, advocating directional cultivation of beneficial algae, preventing and controlling harmful algae, cultivating zooplankton and cultivating cultured varieties can provide economic benefits and maximize output value.
In the marine environment, some diatoms, such as Skeletonema, Nitzschia, Cyclospora, Chaetoceros, Rhizopus, Thalassiosphaera, etc. Overproduction leads to red tide. Too many diatoms (such as Rhizopus) will hinder or change the migration route of herring and reduce the catch. After the death of diatoms, a large number of diatoms deposited on the seabed, forming diatomite, which contains 83.2% silica. Widely used in industry, it can be used as a filler in construction, polishing, filtering agent, adsorbent, paper making, rubber, cosmetics and coatings, and also as a heat preservation agent for green algae water in Hainan ponds. Biodiversity in aquaculture water can make the water body more stable, but a single algae species is definitely not. In directional culture, it is impossible to be single in the outer pond at any time, because there are certain algae species in natural water bodies, including soil and water. In directional culture, Chlorella or Cyclotella can only be used as the dominant species in water, but can not form an absolute species. Good directional culture of beneficial algae can stabilize water quality and control the appearance of harmful algae.
Diatom water from crab pond in Jiangsu, diatom water from indoor industrialized farming in Shanxi, made in June and February this year, 65438+. At this time, the water temperature in Jiangsu and Shanxi is very low, but diatom water is made, which means that diatom water can multiply in large quantities in the low temperature season.
There was a water bloom in the pond, which lasted about 10 days in the early stage, but after 10 days, I didn't know how to solve it. Contact us at this moment and let us give a plan. Analysis: The reason of algal bloom is that there is no continuous corresponding measures, no follow-up nutrition and no follow-up decomposition products of dead algae in peak period and growth period. Algae should be properly supplemented with nutrients during the peak growth period, and at the same time, appropriate microorganisms should decompose dead algae. Algae grow periodically and die at the peak. At the same time, it is necessary to decompose and supplement nutrients to provide nutrients for newly growing algae and keep them stable. It is very important to cultivate algae in outdoor pond or indoor culture, and it is more important to stabilize algae.