Day 13: Biological Indicators

By Olivia Belshaw

RV Investigator has multiple sensors on board that continuously collect data – 24 hours every day at sea. The data is collected and then displayed graphically in a program called Grafana. Grafana can be accessed at any time by anyone on the ship. Much of this data is also transferred back to shore, and data sets from voyages are then publicly released by CSIRO.

One set of particularly useful data collected is called Biological Indicators.  A set of this information can be seen in the first image below – this is a screenshot of the Biological Indicators for a 24 hour period.

The biological data collected onboard includes:

• Fluorescence

  Phytoplankton (microscopic organisms) in the sea absorb specific wavelengths or colours of light, whilst reflecting other wavelengths of light. Fluorescence is a relative measure of the absorption and reflection of wavelengths of light in the water column. The higher the levels of fluorescence, the higher the proportion of phytoplankton present in the water.

• Dissolved oxygen (DO)

  This is a measure of how much oxygen is dissolved in the water. The oxygen dissolves by diffusion from the air above the sea. Different species of organisms need different levels of dissolved oxygen to survive, and the amount required also is influenced by factors such as the water temperature and pollutants present. If the DO levels are too low or too high, it can have a negative impact on aquatic life.

• Salinity

  Salinity refers to the amount of “salt” present in the water. Typical sea water has about 35% salinity. Sodium salts are the most commonly dissolved salts in sea water, but other salts include magnesium, potassium and calcium salts. If salinity levels drop too low, marine organisms can perish.

Screenshots of Grafana data sets can be used in Secondary Science classes as a learning tool for ecosystems and biological interactions – particularly in Senior years.

In Junior Science class (7 to 10), during an “Ecosystems” topic, students could learn about salinity and why the ocean is “salty”. Students could then design and conduct investigations into the effect of salinity on aquatic and terrestrial plants. During a “Chemical Reactions” unit, students could learn about the connection between salinity and corrosion and then conduct investigations into the corrosion of different metals in salty conditions, linking this to ship maintenance and vessel longevity.

In Senior Biology, students could discuss the sea as an ecosystem and explore how factors such as salinity, temperature and DO influence aquatic life and organism adaptions. Students could examine these graphs and look for matching peaks or troughs between different data sets and propose reasons for these. For example, perhaps there is a drop in salinity at the same time there is an increase in DO – this could possibly indicate that two differing currents have converged (see 8pm on the second Grafana data set below, taken below on 8th August). Students could also research the process of testing fluorescence and link this to the characteristics and behaviours of phytoplankton, and propose reasons for peaks and troughs in the fluorescence graph.

In Senior Chemistry, students could research ways in which salinity and DO could be measured in a school laboratory and then perform these tests on local water samples. The results obtained from testing the local water samples could be compared to a set of graphed Grafana data, and students could engage in a discussion to account for any observed differences. Students could also perform an investigation into solubility of sodium salts and temperature, and link this to possible changes of salinity in the oceans depending on water temperature.