Respiration is defined as the exchange of oxygen (O2) and carbon dioxide (CO2) within living organisms. When O2 is the oxidant, respiration takes the general form:
The definition of respiration differs from the perspective of physiology or biochemistry but, generally, it is defined as the exchange of O2 and CO2 in an energetic process.
Respiration occurs at the cellular level with the organelle, mitochondria. This is known as “cellular respiration”. However, respiration can also be viewed as occurring at various levels of biological organisation from individuals, to communities, to ecosystems and to the entire planet. Scientists measure and study the exchange of O2 and CO2, or respiration, at these various levels to understand how organisms and ecosystems respond to stress or change.
Respiration is a relative measurement. There is no right or wrong level of respiration. Rather, a baseline measurement of respiration is established and then compared. Therefore, respiration measurements must be made in context and not in isolation for a meaningful interpretation of the data. Edaphic Scientific specialises in instrumentation for the measurement of respiration at any level of biological organisation.
Edaphic Scientific’s respiration instrumentation
particulate organic carbon (POC) respiration
Climate change is creating a Catch-22 in the world’s oceans. On the one hand, increasing atmospheric CO2 is causing an enlargement of oxygen minimum zones (OMZ), or zones of low dissolved oxygen. The OMZ can be deplete in higher organisms, such as zooplankton, fish and mammals, that require high levels of oxygen for respiration. On the other hand, a recent scientific study, published in Nature, has shown that OMZ can increase rates of carbon storage in ocean sediments thus alleviating the effects of climate change.
To understand how OMZ is increasing carbon storage, the scientists measured the respiration of particulate organic carbon (POC) and the remineralization of POC. Organic carbon particles in aqueous solutions can be classified as either dissolved organic carbon (DOC) or particulate organic carbon (POC). DOC is defined as particles that can pass through a 0.7 to 0.22 um sized filter whereas POC are particles larger than this.
Remineralization of POC, or the returning of organic carbon into CO2, is a critical component of the global carbon cycle. In oceans, remineralization of POC is performed by animals, such as zooplankton, or microbes.
In the ocean where dissolved oxygen is high, animals, such as zooplankton, remineralize POC and this often returns to the atmosphere as CO2, thus potentially contributing to climate change. However, in parts of the ocean where dissolved oxygen is extremely low, or the OMZ, there are little to no zooplankton. Remineralization of POC in these zones is performed by microbes. The research, publish in Nature, found that 70% of POC remineralization in OMZ is due to microbial respiration. The scientists were able to measure the extremely low respiration rates of POC with the Unisense MicroRespiration system.
Mitochondria are the energy drivers of multi-cellular organisms, such as plants and animals, and are the main source of respiration. Direct measurements of mitochondrial respiration, therefore, will provide critical insights into plant and animal physiology.
Shaw et al (2017) provide a comprehensive methodology outlining how to extract mitochondria from cells and then subsequently measure the respiration of that mitochondria. The density gradient centrifugation method is used as a standard procedure to isolate intact mitochondria from plant tissues. Once extracted, the mitochondria are placed inside of the micro-respiration chamber and measured with the Unisense Micro-Respiration system. Via the method outlined by Shaw et al 2017, it is possible to measure mitochondrial respiration and gain significant insights into plant and animal physiology.
The respiration rates of embryos, such as mice, rat, bovine and equine, have been measured for many years with the Unisense Nano-Respiration system.
Scientists had discovered that embryo quality could be determined by its metabolic rate. Oxygen consumption, or organism respiration, is one parameter that infers metabolic rate. Therefore, the higher the respiration rate the better the quality of an embryo.
Lopes et al (2005) deployed the Nano-Respiration system to quantify the relationship between respiration rates and embryo quality for bovines. A detailed description of the research can be found in the Edaphic Scientific case studies page. Lopes et al (2005) concluded that microsensor technology can be used to accurately and rapidly assess embryo quality. Each assessment in their experiment only took 8 minutes to complete and may possibly lead to greater efficiencies for researchers and clinicians.
tissue and organ respiration
Understanding the physiology of the reproductive organs of plants, the flowers, fruits and seeds, is critically important. Measuring the respiration rates of plant reproductive organs can improve agricultural crop yield, as well as understanding threatened or endangered species reproductive capacity. Tissue and organ respiration is a common application for the Unisense Micro-Respiration system. For example, Verboven et al (2011) measured the respiration rates of phellem and stelar tissues in the small herbaceous plant, Melilotus siculus.
An experiment by scientists at The University of Adelaide demonstrated how the Unisense MicroRespiration system can be used to measure fruit and seed respiration. The scientist studied grape berry respiration in the contest of mesocarp cell death and cellular hypoxia.
To study respiration rates of berries and seeds, the scientists harvested grape berries from their study vines and placed them inside Unisense respiration chambers. The chambers were filled with distilled water, sealed and placed within a temperature controlled water bath. Following the measurement of whole berry respiration, the seed was removed from the berry and its respiration was subsequently measured in the chambers filled with distilled water.
The research found that the seed has a high oxygen demand early in berry ripening and almost zero in late stage ripening. This dynamic can have significance for cell death in grapes. Further information on the study can be found in the Edaphic Scientific blog.
The PTM-48A Photosynthesis Meter is able to measure respiration rates of leaves. The meter can support up to 4 leaf chambers for the simultaneous, and continuous measurement of leaf respiration.
photosynthesis and respiration explained:
ecosystem respiration – eddy correlation systems
The eddy co-variance or correlation technique has been used extensively in vegetation ecosystem sciences for many decades. The technique involves measuring the turbulence above plant canopies and relating these “eddies” to the exchange of oxygen and carbon dioxide. This approach has provided tremendous insights into how land-based ecosystems exchange energy.
Recently, the eddy correlation technique has been extended to underwater communities with advanced scientific instrumentation manufactured by the Danish company, Unisense.
“Water flowing over surfaces will under most circumstances exhibit turbulence (eddies).
The eddy correlation technique for flux measurements (Berg et al 2003) is based on measurements of the vertical water velocity component in the hydrodynamic boundary layer and the oxygen concentration in the same time and location in the hydrodynamic boundary layer above the sediment surface.
The product of the vertical velocity and the oxygen concentration constitutes an oxygen transport through the horizontal plane can and by averaging this product over e.g. 10-15 minutes, the net sediment-water exchange of oxygen between sediment and water phase can be estimated and assumed to integrate the consumption over an area of many square meters of the sediment (Berg et al 2007).
The eddy correlation method overcomes the limitations of existing methods (micro profiling and benthic incubators) with regards to spatial scale, ease of use, and invasiveness. The method was pioneered by Peter Berg, University of Virginia, USA, and co-workers (Berg et al 2003, Berg et al. 2007).”
eddy co-variance explained