Intertidal simulation chamber

---

This is a self-contained, automatic experimental system that simulates the intertidal environment. It’s like a PCR machine for the intertidal, with the added advantage of being accessible online! Multiple machines can create “virtual common garden experiments” across large geographic spans. The system plugs into a regular power outlet and controls 220 V devices (such as pumps and heaters) and 12 V (such as fans and lights).

This system pairs well with our autonomous temperature sensors (Envloggers) as it can replicate whatever temperature profiles they collected in the field. It also pairs well with our cardiac performance logger (PULSE V2), which can monitor the thermal stress of animals inside the experimental unit. 

• Capable of simulating the complex thermal conditions characteristic of the intertidal environment.
• Configurable tide timings, which can be regular or change from one tide to the next.
• The unit has two chambers: a top experimental chamber where organisms live and a bottom chamber which holds seawater during low tide.
• During low tide, heating is provided by six 50 W infra-red lamps, which simulate natural solar heating. These lamps do not produce visible light, only heat.
• Wired EnvLoggers inside the chamber provide temperature feedback during low tide. IR is continuously and automatically adjusted to follow even the most complex thermal profiles.
• Computer-controlled fans provide cooling,  swapping inner hot air with colder exterior air.
• Inside the chamber, air-circulating fans contribute to temperature homogenisation during low tide.
• During low tide, seawater moves to the lower chamber and is pre-heated or cooled to the exact temperature required at the start of the next high tide.
• During high tide, water temperature is continuously monitored and adjusted.
• Regular seawater changes can be programmed and done in an automated way.
• Visible light is independently provided by LED strips, producing 1130 lumens each. LED strips are easily swapped if needed. The number of stripes is also configurable to keep algae happy. 
• Intertidal chambers can be connected to WiFi, and experimental conditions can be remotely monitored and changed at any moment through a dedicated webpage. The web interface is being continuously improved and will receive new features. 
• It is possible to coordinate simultaneous experiments running in geographically-separated labs anywhere in the world.
• The machine also stores programmed profiles (i.e., what it should do) and sensor data (i.e., what it actually did) in an SD card for offline data transfer if WiFi is unavailable.
• The unit's footprint is 80 x 60 x 100 cm for the tank, 30 x 20 x 40 cm for the controlling unit, and 60 x 40 x 60 cm for the chiller. Reserving some extra room is advisable.

• The control unit has a colour LED screen which shows the system's current status (e.g., which pumps or heaters are working and at which rate) as well as all temperatures currently being measured.
• The screen also shows the history of the set points (i.e., what should have happened) and the actual logged data (i.e., what really happened). 
• The screen also shows (and allows to change) the next experimental set-points.
• The control panel has a series of switches to manually override the current experimental settings at any given moment. They allow, for example, to force a quick low tide so as to manipulate a sensor or an animal. The automatic control can be resumed as easily as it was interrupted.
• The physical control system is mirrored in a remote server. The entire unit can be monitored online, and the experimental conditions can be updated or changed remotely on the fly.
• Data from sensors is stored in an SD card and can always be used as a "black box" if something goes wrong.
• The remote server also works as a "black box", storing all logged data.

• Electric circuits are protected by a circuit breaker. 
• Power cables that run near the heat lamps are heat-resistant. 
• Fans are IP69K rated (i.e., withstand high water pressure and high temperature). 
• The system has redundant sensors to monitor water in the upper and bottom chambers. In the unlikely event of a pump failure, they warn the controller, which notifies the user while protecting organisms from over-stressing.
• Temperature feedback is provided by three redundant waterproof/shockproof sensors in the experimental chamber (on top) and two redundant waterproof/shockproof sensors in the water reservoir (low chamber). In the unlikely event one fails, the controller notifies the user while protecting organisms from over-stressing.

The chamber is assembled in Portugal by specialised engineers in total accordance with environmental and labour laws and best practices. The cost of the entire system is €6,000. That includes two water tanks (one that simulates the intertidal and another that holds and conditions water), sensors, pumps, valves, lamps, LED strips, fans, heaters, an Aqua Medic Titan 200 chiller, a powerful electronics unit with WiFi connectivity, a LED screen, and manual control switches. 

This is an open-source project. Hardware and software will soon be openly available in Methods in Ecology and Evolution and in GitHub.