RotoBODQuantifying Oxygen Consumption by Suspended Particles and Organisms

Sinking or floating is the natural state of planktonic
organisms
and particles in the ocean. Simulating these conditions is critical
when making measurements, such as respirometry, because they allow
the natural exchange of substrates and products between sinking particles
and water flowing around them and prevent organisms that are accustomed
to motion from changing their metabolism. We developed a rotating
incubator, the RotoBOD (named after its capability to rotate and determine
biological oxygen demand, BOD), that uniquely enables automated oxygen
measurements in small volumes while keeping the samples in their natural
state of suspension. This allows highly sensitive rate measurements
of oxygen utilization and subsequent characterization of single particles
or small planktonic organisms, such as copepods, jellyfish, or protists.
As this approach is nondestructive, it can be combined with several
further measurements during and after the incubation, such as stable
isotope additions and molecular analyses. This makes the instrument
useful for ecologists, biogeochemists, and potentially other user
groups such as aquaculture facilities. Here, we present the technical
background of our newly developed apparatus and provide examples of
how it can be utilized to determine oxygen production and consumption
in small organisms and particles.