Welcoming the Reefie sensor array
The beauty and success of all shallow coral reefs is entirely dependent on the intricate and dynamic relationships that exist within it. From the essential symbiosis of zooxanthellae and polyps, to the carefully farmed algae by select species of damselfish, everything on the reef has a purpose. The presence, or in fact absence, of any given species may have a distinct and cascading impact on other inhabitants of the delicately balanced ecosystem.
At MCP, we track the health of the coral reefs across Negros Oriental daily. Along with the density of invertebrate life and the composition of the reef itself, we also count the biomass of fish available inside and outside the MPAs (also known as the ‘spill-over’ effect). The aim of course, is to ensure that the productivity of the MPA provides sufficient and sustainable fishing to support the livelihoods of local fisherfolk. We recently celebrated our 10th anniversary, which indicated the point in time where MCP has accumulated ten years’ of trend data. It’s a notable milestone, but most importantly, it opens the door for deeper scientific analysis into the effectiveness of the MPAs we monitor.
Over the last decade, we have seen numerous changes in substrate composition and fish population numbers. Some of these can be attributed to seasonal changes in weather, and mating/spawning periods, but there are some that have proved a little more tricky to explain. The relationships within coral reefs are so incredibly intricate, that scientists worldwide don’t claim to have a full understanding of them all, but MCP has a new member of the team that might take us a step closer to trying…
Meet…“Reefie”! Reefie is a water quality monitor with six sensitive receptors, enabling us to accurately record; temperature, pH, conductivity, turbidity, dissolved oxygen and salinity at the flick of a switch. The bespoke technology was lovingly crafted by the enthusiastic engineer, Krasi from Bulgaria. He hand-delivered Reefie to us in December 2024, and asked only that Reefie be put to good use!
After calibration and methodology refinement, Reefie is now taken on a daily survey dive, where he collects huge amounts of data. The science team are taking particular interest in the measurements of dissolved oxygen at each site. We know that the percentage of dissolved oxygen in water can be a key indicator for a number of other reef health factors.
Zooxanthellae are photosynthetic algae (they take in oxygen and energy from the sun to make their own glucose, which provides energy to the corals for growth and respiration), so the percentage of dissolved oxygen in the water will directly impact the photosynthesis of these algae and therefore the respiration rates of corals.
These factors can affect coral morphology, biodiversity, resilience and bleaching of the corals, and have a significant impact on how the reef survives. It even has an impact on fish behaviour! So being able to detect small changes in the amount of oxygen in the water, might give us an early warning sign for bigger changes to come in an MPA, and we might be able to catch it before it becomes a larger problem.
Some of the familiar, adverse conditions of a coral reef ecosystem, such as high temperatures and eutrophication (i.e., overly-high nutrient levels) can be mitigated by reestablishing optimum levels of oxygen. These are reasonably inexpensive, easy-fixes to implement, with potentially very effective results which can positively impact the productivity of our MPAs.
So, we welcome Reefie to the team and eagerly await the new tiny insights that might make big splashes in 2025! If you need a reefie on your coral reef monitoring project, consider visiting the website detailing the development of the sensor array. Everything is open source!
