Name: Coral Growth and Monitoring Using the Micro-Device System
Uploaded: 2023-07-21T14:50:00
Description: Watch this Scientific Journal Video about Coral Growth and Monitoring Using the Micro-Device System at JoVE.com

coral growth and monitoring using the micro-device system

Un système combiné de micro-dispositifs pour favoriser et surveiller la croissance des coraux

The deterioration of coral reef ecosystems has been occurring worldwide over the past 70 years. Considering all the major coral areas across Central America1, Southeast Asia2,3,4,5,6, Australia7,8, and East Africa9, the global coverage of coral reefs has halved since the 1950s10. This mass loss of coral reefs has resulted in ecological and economic problems. For example, by tracing the presence/absence and abundance of all kinds of coral-dependent fishes for 8 years, researchers concluded that the coral decline has directly caused a substantial decrease in fish biodiversity and abundance in Papua New Guinea11. This result proved that the coral decline can not only undermine coral reef-based biological systems but also reduce fishery incomes.
Over decades of field surveys, including direct monitoring, remote sensing, and data comparison, the scientific community has identified several factors causing the mass coral decline. One major reason for the mass coral decline is coral bleaching caused by high seawater temperatures12,13. By combining bleaching and meteorological records, scientists have concluded that coral bleaching is happening more frequently in El Ni&#241;o-Southern Oscillation phases14. Another reason for the coral decline is ocean acidification. Owing to the increased CO2 concentration in both the atmosphere and seawater, calcium carbonate dissolves faster than before, causing downscale net coral reef calcification15. Indeed, it has been concluded that when the CO2 concentration in the atmosphere reaches above 500 ppm, tens of millions of people will suffer, and the coral reefs will be at risk of significant deterioration and symbiodinium detachment16,17. There are other factors that can also affect coral survival, such as inshore pollutants causing or accelerating coral decline. Researchers in Hawaii measured the carbon, oxygen, and nitrogen isotopes in corals, along with the dissolved inorganic carbonate and the related nutrients (NH4+, PO43-, NO2&#8722;, and NO3&#8722;), and concluded that pollution from the land magnified the coastal acidification and bioerosion of corals18. Further to pollution, urbanization also endangers coral survival and causes relatively low architectural complexity in corals, as revealed by a study on the coral survival status in Singapore, Jakarta, Hong Kong, and Okinawa. Thus, the impact of anthropogenic stressors and the superimposed effects of climate change are leading to widespread reduced biodiversity on coral reefs and an associated decline in coral ecological function and resilience19.
It should also be noted that a large number of microorganisms participate in the physiological functions of corals, including nitrogen fixation, chitin decomposition, the synthesis of organic compounds, and immunity20, and these microorganisms should, thus, be included when considering coral reef deterioration. In natural environments, such as coral reefs, many factors cause hypoxic or anoxic conditions, including insufficient water circulation, algal exudate, and algal overgrowth. This phenomenon negatively affects the population distributions of coral and coral-related microorganisms. For example, Vietnamese scientists found that in Nha Trang, Phu Quoc, and Ujung Gelam, bacterial composition in the coral Acropora Formosa could be affected by dissolved oxygen at different locations21. Researchers in the United States explored hypoxic or anoxia conditions in corals and found that algal exudates can mediate microbial activity, leading to localized hypoxic conditions, which may cause coral mortality in the direct vicinity. They also found that corals could tolerate reduced oxygen concentrations but only above a given threshold determined by a combination of the exposure time and oxygen concentration22. Researchers in India found that when Noctiluca scintillans algae bloomed, the dissolved oxygen decreased to 2 mg/L. Below this concentration, about 70% of Acropora montiporacan died because of hypoxic conditions23.
All the abovementioned facts and factors suggest that environmental change leads to the deterioration of coral reefs. To culture and study reef corals under certain conditions, it is important to accurately and comprehensively build up a controllable microscopic environment for reef corals to inhabit. Normally, scientists focus on temperature, light, water flow, and nutrients. However, other features, such as the dissolved oxygen concentration, microorganism abundance, and microorganism diversity in the seawater, are commonly ignored. To this end, our group has explored the possibility of applying small equipment to culture coral polyps in a relatively controlled environment24,25. In this work, we designed and built up a modular micro-device system for coral culture. This modular micro-device system can provide a controllable micro-environment in terms of the temperature, light spectrum, dissolved oxygen concentration, nutrients, and microorganisms, etc., and has the capacity for expansion and upgrade.
Modules and functions of the device 
The micro-device system was inspired by the Berlin system26, but no live rocks are used in the current system. As shown in Figure 1, the current system comprises six main modules, two brushless motor pumps, one gas pump, one flow-through UV lamp, one power supply, certain electronic control components, and the related wires and screws. The six main modules include a seawater store module (with an air pump and temperature sensor), a temperature control module, an algae purification module, a microbial purification module, an activated charcoal purification module, and a coral culture module.
Device architecture 
As shown in Figure 2 and Figure 3, the overall micro-device system can horizontally be divided into two compartments with a temperature control module in between. For safety reasons, all the seawater-containing modules and parts are placed in the left compartment, named the culture compartment. The other electronic parts are placed in the right compartment, named the electronic compartment. Both compartments are sealed or packaged within shells. The temperature control module is fixed in a divider plate in between. The shell of the culture compartment includes a baseboard and three screw-fixing plates. This design ensures compartment tightness and facilitates the operation of the system. Additionally, the tightness favors accurate temperature control. The shell of the electronic compartment includes a baseboard, two screw-fixing plates, and one front control panel.
Water circulation 
An inner and outer seawater circulation loop connected to the seawater store module was pre-designed. The inner circulation loop successfully connects the seawater store module, temperature control module, flow-through UV lamp, algae purification module, and microbial purification module. This circulation loop aims to provide suitable physiochemical and physiological seawater conditions for the corals, and no frequent maintenance is needed. The algae purification module contains Chaetomorpha algae, which absorbs the extra nutrients (nitrate and phosphate) in the water. The microbial purification module contains the bacterial culture substrate, which cultivates the microbiome to transfer nitrite and ammonium into nitrate for water purification. All these modules need to be replaced only under critical circumstances.
The outer circulation loop successively connects the seawater store module, coral culture module, and activated charcoal module. This circulation loop aims to provide light, tightness, water current, and high seawater quality to the corals. The seawater can be refreshed through a water inlet and a water outlet. Additives are added through a three-way valve, and the seawater sample can also be extracted from this valve for inspection. Air can be pumped in through an air inlet and discharged from an air outlet.
Electronic design 
A 220 V AC power supply with a switch and a fuse is used for the whole system. The input power is divided into four branches. The first branch goes to a 12 V DC power supply, which directly powers the heating panel, cooling panel, and cooling fan. This branch also indirectly powers two pumps and two lighting panels through a four-channel DC transformer. The second branch goes to a PID temperature controller. The third branch goes to an air pump power supply. The last branch connects to a UV lamp power supply. A solid-state relay connects the PID temperature controller and the cooling panel in the temperature control module. A regular relay is used to connect the PID temperature controller and the heating panel. The four-channel DC transformer converts the voltage to that required.
There are two control panels on the right part of the system. There are four switches and one controller for the UV lamp on the top panel, including a main power switch, a UV lamp power switch, an air pump switch, and a temperature control switch. The main power switch controls the 12 V power supply of the system.
A PID temperature controller, a cycle timer, a four-channel DC transformer, and a three-channel timer are on the front panel. The PID temperature controller adjusts the water temperature by controlling the heating and cooling panels in the temperature control module. The temperature control module only works when the inner circulation pump is working and the water is flowing past the temperature control module. The cycle timer is connected to the air pump power line. Its purpose is to assign the working time period to the air pump. There is a three-channel timer deployed in the electronic compartment too. This timer controls the work time period for the air pump, coral light, and algae light.

Pleins feux sur l’auteur : Faire progresser la culture des coraux - Créer un système de microenvironnement semi-contrôlé quantitativement pour contrer les limites actuelles 

Un système de micro-dispositifs intégré pour la croissance et la surveillance des coraux

The aim of our research is to develop an artificial microenvironment system for coral culture and study. The microenvironment in the micro-device system can at least be semi-quantitatively controlled. At the present, the existing equipment and the system used for coral culture lack precise control over temperature and other environmental factors.Additionally, these system are open, making them susceptible to contamination from an airborne substance. Our indoor coral culture system boasts a superior control accuracy, and the microbial tightness compared to other similar system or tanks. Additionally, our system is commercially cost-effective.Using this micro-device system, we can somehow customize the environmental parameters like temperature, strength, or metabolite concentration, which will make the coral study more quantitative and might promote the current coral research. We would like to know about longevity of corals in this artificial micro-device. Another important question that we want to address is how the artificially built-up system affects the growth process of corals in comparison to the nature environment.

Watch this Scientific Journal Video about Coral Growth and Monitoring Using the Micro-Device System at JoVE.com

Coral Growth and Monitoring Using the Micro-Device System  

Croissance et surveillance des coraux à l’aide du système de micro-dispositifs

Après avoir réglé le système de micro-entraînement, ajoutez un millilitre de la solution de source de microbiome commerciale dans 500 millilitres d’eau de mer tout en remuant. Ensuite, injectez 50 millilitres de la solution diluée et 10 microlitres de la solution commerciale de nutrition des coraux dans le système de circulation. Allumez la pompe de circulation interne et allumez la pompe à air pour cultiver le microbiome pendant 21 jours.Coupez les branches de corail de roche en une longueur de trois à cinq centimètres. Collez ces branches de corail sur des bases de support de corail imprimées en 3D. Replacez les échantillons de branches de corail dans le réservoir d’eau de mer d’origine pendant au moins sept jours pour les récupérer.Fixez la base de support corail sur l’unité de rotation à l’aide de colle. Assemblez le module de culture de coraux et connectez-le à la boucle de circulation extérieure. Placez l’appareil photo sur le dessus du studio et capturez les images à partir d’une vue verticale.Ensuite, placez le module de culture de corail dans le mini studio photo avec le corail positionné au centre et en bas. Capturez des images de corail en faisant pivoter la poignée extérieure. Le module de culture de coraux a permis de contrôler efficacement la température de l’eau de mer et d’éviter les fluctuations de température, ce qui peut fortement affecter la survie des coraux.Les tentacules des coraux échantillons se sont étendus sur une période d’un mois, ce qui indique que le système a fourni un environnement de survie approprié pour le corail.

Research

JoVE Journal

Bioengineering

Coral Growth and Monitoring Using the Micro-Device System

An Integrated Micro-Device System for Coral Growth and Monitoring

Corals are fundamental organisms in marine and coastal ecosystems. With the advancement of coral protection research in recent years, precise control of ...