Benthic chambers are widely used to study sediment-water interactions and are particularly effective for measuring chemical exchanges, such as gas and nutrient fluxes, between sediments and the overlying water.
In our lab, we utilize benthic chambers to investigate gas and nutrients exchange processes in intertidal environments, which poses an additional challenge as the system undergoes changes between immersion and emersion. This require the use of different setups for water and air.
These chambers are positioned directly over sediment surfaces to create a closed system, allowing us to precisely measure gas exchange rates under natural conditions. By examining CO₂ (in emersion) and O2 levels (immersion), we can assess primary production rates (O2 generation by photosynthetic organisms) and respiration rates (CO₂ production by all organisms). This balance provides insight into whether a specific area acts as a carbon sink or source, reflecting its role in carbon cycling.
To achieve this we employ two different types of chambers.
The first one is a hemispherical chamber (designed in collaboration with Aquatic Biotechnology) that allows to measure O2 fluxes continuously under immersion and at the same time to collect water samples for nutrients and other solutes.
By exchanging the water pump to a ventilator, we can collect air samples to measure CO2 (and other gases) fluxes.
Thee second type of chamber (design thanks to Adrien Jacotot) allows to measure CO2 fluxes in real time.
Advantages of Using a Benthic Chamber
1. Accurate Flux Measurements in Sediment-Water Exchange
By isolating a section of sediment and water, benthic chambers can provide accurate measurements of specific processes such as respiration, photosynthesis, or nutrient cycling in a defined sediment area, including the effect of diffusion and advection due to anaimal activity and hydrodynamics. Therefore, it is essential to maintain turbulence within the chamber during measurements that should in theory simulate the external one. Also they have the advantage to depend on the natural temperature and light changes.
2. Useful in Low-Turbulence or Deep-Water Environments
In areas where natural water flow is minimal (such as deep-sea environments or low-energy zones), benthic chambers are ideal because they don’t rely on eddies for measurements. This advantage makes them versatile for studies in a variety of aquatic environments, including calm waters and deeper sediments where other techniques may not be effective.
3. Comparison and Calibration for Other Techniques
Benthic chambers have been the standard method to measure fluxes in situ so they are used as a reference method to compare and “calibrate” other flux-measuring techniques, such as Aquatic Eddy Covariance.
4. Low Cost and Accessibility – Compared to some high-tech measurement methods, benthic chambers are relatively low-cost and straightforward to deploy without the need for extensive training. This makes them accessible for many research applications, especially where budget or logistical constraints exist. It is also easier to have several chambers deployed simultaneously allowing statistical comparisons.
In summary, benthic chambers are valuable tools for studying sediment-water interactions in a controlled and precise manner. They are adaptable, cost-effective, and provide reliable data, especially in low-turbulence environments, making them essential for researchers studying benthic ecosystems and sediment chemistry.
