How an extreme El Niño sea surface temperature spike starved Bali's ocean
Source PublicationScientific Publication
Primary AuthorsWicaksono, Mulsandi
"Imagine a cold, nutritious soup sitting at the bottom of a bowl, covered by a thick layer of warm oil. No matter how hungry you are, the oil acts as a lid, keeping the good stuff trapped at the bottom while the surface remains empty."
Is there a hidden elegance in biological chaos?
When environmental systems go haywire, life responds in highly structured, almost programmed ways. We often think of biology at the microscopic level, but an entire ocean operates much like a giant, macro-level genome. When a thermal fever hits, the whole system adapts, shuts down, or alters its behaviour to survive the stress.
Tracking the El Niño sea surface temperature
In 2015 and 2016, the Pacific Ocean experienced a massive thermal shock. Researchers wanted to know exactly how this event affected the waters around southern Bali. They used satellite data to measure two things: the heat of the water and the amount of chlorophyll-a. Chlorophyll acts as a proxy for phytoplankton, the microscopic plants that feed everything from tiny fish to massive whales.
The results were clear. The data showed that as the water grew hotter, the phytoplankton vanished. Temperatures rose by nearly 2 degrees Celsius above normal, peaking past 30 degrees. At the same time, chlorophyll levels plummeted by 54 per cent.
The physical lid on marine life
Why does warm water kill off these resilient little plants? It comes down to physics and ocean layering.
Normally, cold, nutrient-rich water from the deep ocean rises to the surface. This process feeds the phytoplankton. However, the extreme heat created a thick, warm layer of water on top. This warm layer was highly saline and acted like a heavy blanket. It intensified what scientists call vertical stratification. In plain English, the ocean separated into distinct layers that refused to mix. The nutrients stayed trapped in the dark depths, while the sunlit surface turned into a barren desert.
What this suggests for the future
We must separate what the satellites measured from what this means for tomorrow. The sensors directly recorded a spike in heat and a drop in green pigment. However, this suggests that future warming events could severely disrupt the marine food chain. If the base of the web collapses, the effects ripple upwards to fish, marine mammals, and human fisheries. By mapping this temporary biological collapse, scientists now have a clear template to monitor ocean health across the Indo-Pacific. It is a stark reminder of how quickly a system can reorganise itself when the temperature rises.