SeaSim Measurement Capabilities

SeaSim users have access to a range of bio-optical tools commonly used to evaluate photosynthetic functioning in marine research:

Respirometry

SeaSim has a range of gas-tight incubation chambers and optical oxygen sensors to evaluate the metabolic performance of marine organisms (e.g., microalgae, fish, corals, seagrass) under a range of environmental conditions in the SeaSim.

Routine descriptors of metabolic performance that can be estimated via closed-system respirometry include:

net primary productivity (NPP),

gross primary productivity (GPP),

photosynthesis to respiration (P:R) ratio,

light R:P ratio, and

critical oxygen tension (Pcrit).

SeaSim has equipment to estimate organism surface area and buoyant weight to facilitate normalisation of metabolic rates where required.

Active Flourometry

Active fluorometry is a technique that allows for rapid and non-invasive evaluation of the photosynthetic performance of marine organisms (e.g., corals, seagrass and macroalgae) by measuring fluorescence emanating from Photosystem II (PSII).

Use of active fluorometry in marine ecophysiology has played a significant role in understanding the responses of benthic autotrophs to environmental change. A range of portable fluorometers exist that are broadly categorised into two methods according to how they manipulate the PSII redox state: Fast Repetition Rate (FRR) and Pulse Amplitude Modulated (PAM) fluorometry.

PAM Fluorometers at SeaSim

SeaSim can provide researchers with access to several variants of PAM fluorometers including:

Diving-PAM,
Imaging-PAM, and
Microscope-PAM for use with various organism sizes/types (e.g., from single-cell Symbiodiniaceae to full-sized adult coral colonies).

Incorporation of fluorescence measurements allows researchers to monitor organism physiology over the course of an experiment – either as a baseline measurement to satisfy reviewer expectations, or as a key response variable.

Click here to learn more about active flourometry and using it for your experiment.

Dissolved Oxygen

SeaSim has a selection of oxygen-sensing equipment that can be used by researchers wishing to measure dissolved oxygen (DO) in their experiments including:

several FireSting-O2 units (manufactured by PyroScience) which allow for optical determination of DO across four individual channels. The FireSting-O2 units can be flexibly paired with needle-type probes, robust probes and sensor spots depending on the specific application, and the proprietary software allows for automatic temperature correction of O₂-solubility as needed.

FireSting-O2 units can acquire DO data at high temporal resolution (seconds) without consumption of ambient oxygen – making them ideal for capturing dynamic changes in DO during e.g., incubation approaches targeted at examining oxygen-consumption patterns in marine organisms.
a portable, hand-held multiprobe meter (YSI ProDSS) capable of measuring dissolved oxygen, temperature, and conductivity simultaneously for “point-source” measurements of dissolved oxygen.

Click here to learn more about dissolved oxygen.

Buoyant Weight

SeaSim has a dedicated station where researchers can undertake buoyant weight measurements (with accuracy to 0.01 g) and where seawater temperature is controlled to minimise organism physiological stress.

Click here to see an example of where this setup has been used to measure buoyant weight in an experiment at SeaSim.

Click here to learn more about using the buoyant weight method.

Light

To ensure that the light conditions match your experiment requirements, SeaSim has a range of instruments to characterize both light intensity and quality (spectrum).

Light Intensity
For most aquarium experiments – and especially those involving photosynthetic organisms such as corals and seagrasses - it is necessary to provide a specific amount of photosynthetically active radiation (PAR, in units of: µmol photons m^-2 s^-1). PAR comprises all photons of light with wavelengths ranging from 400 – 700 nm, which are equally capable of driving photosynthesis. Experimental PAR requirements may vary depending on the organism type, an organism’s environmental history and whether light is an independent variable within the experimental design itself.

SeaSim has several Li-Cor (LI-250A) light meters that our technical team used to measure and map PAR levels when setting up experiments. These portable light meters are the gold-standard across many research fields and are also available to researchers working in our facility. Our light meters can be equipped with either planar (flat collection surface) or scalar (spherical or hemi-spherical collection surface) quantum sensors to offer flexibility in light field measurements in air and seawater. Our technical team can advise on the appropriate sensor type for your experiment. In addition to portable light meters, many of our experimental rooms are equipped with scalar PAR sensors that allow continuous monitoring of PAR levels in designated aquaria. Such PAR data is available to view in real-time via our facility’s SCADA control system – accessible by touch-screen interfaces outside most experimental rooms.

Light Quality (spectrum)
While all wavelengths of light between 400 -700 nm (i.e., PAR) can drive photosynthesis, different marine photosynthetic organisms absorb some wavelengths better than others depending on diversity in pigment composition. For example, corals typically absorb blue light (~400 – 480 nm) particularly well but absorb relatively little light in the green region (500 – 570nm). Spectral quality is therefore an important experimental consideration to ensure provision of sufficient photosynthetically usable radiation (PUR) – essentially, the part of PAR that can be absorbed by a given organism.

SeaSim technical staff have access to portable spectrometers such as the Jaz and USB2000 by Ocean Optics allowing them to measure spectral quality in any experimental setting. This measurement capability also extends to non-visible light in the ultraviolet (UV) region for experiments examining impacts of UV exposure in the marine environment.

Importantly, the ability to measure spectral light intensity and quality, together with the flexibility of our adjustable LED lighting units allow SeaSim technical staff to fine-tune light conditions to meet the exact needs of your experiment.