routine maintenance of micro-device system to promote optimum coral growth

用于促进和监测珊瑚生长的组合微型器件系统

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.

作者聚焦：推进珊瑚文化 - 创建半定量控制微环境系统以应对当前限制 

用于珊瑚生长和监测的集成微型设备系统

Watch this Scientific Journal Video about Routine Maintenance of Micro-Device System to Promote Optimum Coral Growth at JoVE.com

微装置系统的日常维护，以促进珊瑚的最佳生长

首先，通过检查踢脚线、接缝和连接器是否有水渍或液滴来执行泄漏检查，以确保系统安全。系统盖壳的透明性便于目视检查漏水情况。使用注射器从活性炭和海水模块之间的三通阀中提取 10 毫升海水。将添加剂溶解在提取的海水中，并通过三通阀将溶液注入系统，为系统补充营养物质和其他试剂。为了减少培养系统中的毒性浓度和富营养化，为了安全起见，请通过关闭整个系统的电源并拔下电源线来换水。然后拆下珊瑚养殖模块，将外部废水管道连接到海水储存模块中的出口。现在旋转系统并将其正面朝下放置。打开出口，让海水从系统内部流出。排出所需量的海水并取下出口。然后，重置系统，将新制备的海水注入进水口。将珊瑚养殖模块重新安装到系统中。打开系统并等待系统恢复正常。

routine-maintenance-micro-device-system-to-promote-optimum-coral

Research

JoVE Journal

Bioengineering

Routine Maintenance of Micro-Device System to Promote Optimum Coral Growth

81 次观看. 首先，通过检查踢脚线、接缝和连接器是否有水渍或液滴来执行泄漏检查，以确保系统安全。系统盖壳的透明性便于目视检查漏水情况。使用注射器从活性炭和海水模块之间的三通阀中提取 10 毫升海水。将添加剂溶解在提取的海水中，并通过三通阀将溶液注入系统，为系统补充营养物质和其他试剂。为了减少培养系统中的毒性浓度和富营养化，为了安全起见，请通过关...

视频: 微装置系统的日常维护，以促进珊瑚的最佳生长

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 the coral culture environment is highly in demand for coral conservation and study. Here, we developed a semi-closed coral culture micro-device system as a multi-functional platform, which can provide accurate and programmable temperature control, a sterile initial environment, long-term stable water quality, an adjustable dissolved oxygen concentration, and a customized light spectrum for corals. Owing to the modular design, the coral culture system can be upgraded or modified by installing desirable new modules or removing existing ones. Currently, under appropriate conditions and with proper system maintenance, the sample corals can survive for at least 30 days in a healthy state. Furthermore, due to the controllable and sterile initial environment, this coral culture system can support research into the symbiotic relationship between corals and associated microorganisms. Therefore, this micro-device system can be applied to monitor and investigate sea corals in a relatively quantitative manner.

This protocol describes the development of a modular controllable micro-device system that can be applied for the long-term culturing and monitoring of sea corals.

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