Today we are going to talk about a type of brown seaweed that is very useful in gastronomy. It’s about the porphyra. Often found on rocky shores around the world, this genus includes some of the species found abundantly in the tropics and at the poles. The greatest diversity of was algae is usually found in the boreal regions flies areas that have a cold climate tending to temperate. Most of the species of this genus occur annually in summer or winter.
In this article we are going to tell you all the characteristics, reproduction and cultivation of Porphyra.
Key features
It is a type of algae that supports desiccation. Thanks to withstanding this, it can be found in the highest and driest regions of the intertidal region. When we talk about algae we are not talking about stems but about thalli. These thalli appear naturally in their free state and have microscopic filaments that are responsible for digging the substrate in order to live. Porphyra sheets can be circular or linear and can measure a few centimeters or even more than a meter. It all depends on the environmental conditions in which it grows and how long it can thrive.
The color usually varies depending on the species we are treating. There are some that vary between pink, red, yellow, brown and green. These latter colors are found more frequently in intertidal zones. The life cycle of Porphyra is quite complex. It has a microscopic stage in which it is diploid and is known by the name of conchocelis. It was pale younger consists of filamentous branches. Under specified environmental conditions the filaments they have are capable of forming branches that are swollen called conchosporangia.
The way to multiply does it through meiosis. This process takes place in each conchospora and develops into new Porphyra thalluses. In some species monospores are produced on the margins of the thallus and the laminae reproduce sexually. The zygote divides to form a bundle of diploid cells known as the carposporangium. It is the diploid carpospores that are released from the carposporangias to form diploid cell bundles and conchocelis filaments to survive during the summer season.
Range and habitat of the Porphyra
In the China area, the Porphyra haitanensis variety is found in the southernmost part, while the yezoensis species is found further north. They have a stage that is known as nori and comprises the thalli of the species. These thalli usually emerge in autumn and early winter, especially on rocky shores. The seeds are released in the conchocelis stage and are filamentous.
The optimal development conditions for this type of algae usually vary. These conditions are summarized as temperature, salinity and low light intensity. The most normal thing is that the young stems can withstand higher temperatures than when they are adults. The lower temperatures usually induce a normal growth of both species, both in the north and in the sun. More or less temperatures are between -3 and 8 degrees. High light intensity is quite good for the growth of both species. Both types of stems are able to tolerate being dissected, so their ability to survive is much higher. The Porphyra haitanensis species can survive for a week despite having lost more than 70% of all its moisture.
For these algae the amount of nutrients such as nitrate or nitrogenous ammonium are essential. And it is that they are algae that require approximately about 100-200 milligrams of nitrogen for every cubic meter of surface area. This they need for normal growth. However, if nitrogen concentrations in the soil are less than 50 milligrams per cubic meter, growth will be inhibited.
Porphyra production systems
Due to its complicated life cycle, the Porphyra cultivation system is divided into 5 different phases. We started the first with the cultivation of the conchocelis. Subsequently, the conchospores are collected to see a growth in the open sea. Finally, there are two other phases which are harvesting and processing. Let’s see what are the step-by-step production systems.
First of all, start with supplying the seed. This is where the cultivation of conchocelis is summarized. This cultivation is carried out in two stages. The first is held abroad in the months of May to October. During these months, the conchocelis is cultivated and the conchospores are produced. The second stage is from October to May. This stage consists of the concentration in the cultivation of small thallus in the field.
In the middle of May the Asian clam is planted to be able to dry the conchocelis releasing the conchospores. A suspension of these is usually sprayed on the substrate. The substrate can also be immersed in the suspension. The cultivation is usually carried out in large, elongated, shallow tanks. What is necessary is to store a layer of seawater of approximately 30 cm that has previously been subjected to sedimentation. Nitrogen and phosphate nutrients are added to this seawater that has undergone sedimentation, which are necessary for Porphyra to develop well.
In this stage of formation, the temperature is not usually controlled too much and can vary depending on the temperature of the environment. However, it is known that growth or optimum occurs between 20-25 degrees of temperature. In late May and early June temperatures are usually raised to 23 degrees to facilitate vegetative growth. The following month the intensity of the light is reduced to promote the formation of the conchosporangias. These conchosporangias are responsible for releasing the conchospores. At the end of August the temperature is adjusted again to raise it to 28 degrees and the temperature is lowered again the following month.
Fattening technique
Several techniques are used to fatten the algae and have a larger surface:
- Floating system: It is used in Japan and it is about nets that join floating buoys on the surface of the sea so that the stems always remain immersed in the water.
- Semi floating system: it is a mix of a floating system with a fixed net. It has been used widely in China.
- Fixed networks: The nets are hung between poles and at low tide they are exposed to the air to dry. This type of culture is restricted to internal parts of bays that have shallow, sandy-textured bottoms.
I hope that with this information you can learn more about Porphyra and its characteristics.
