Researchers found that hypoxia at the sediment level in the Banana River triggers the release of buried nutrients, fueling harmful algal blooms.
Key facts
- •The study analyzed oxygen levels at 80 test locations across the Banana River.
- •Oxygen levels at the sediment-water interface were 10%–15% lower than at the surface or mid-depth.
- •Muck deposits contribute to hypoxia up to 500 meters (1,640 feet) from their physical location.
- •Sensors recorded hypoxic conditions in the lagoon 90% of the time.
- •The process of internal nutrient loading causes phosphorus to be rereleased into the water, fueling algal blooms.
A study led by Florida Tech assistant professor Austin Fox has identified that low oxygen levels, or hypoxia, at the floor of the Banana River are causing the rerelease of nutrients trapped in sediment. Published in the journal Frontiers in Marine Science, the research highlights how these nutrients feed harmful algal blooms within the Indian River Lagoon system.
By the numbers
Measuring Hypoxia at the Sediment-Water Interface
The research team analyzed oxygen levels at 80 locations across the Banana River to map areas of severe hypoxia. Findings revealed that oxygen levels at the sediment-water interface were 10% to 15% lower than those measured near the surface or at mid-depth. While fish swimming in higher water layers may not experience these conditions, the low oxygen levels directly impact organisms that inhabit the sediment, such as clams, shrimp, and worms.
The Role of Muck in Nutrient Cycling
The study highlights the role of 'muck,' a fine-grained, organic-rich sediment found on the floor of the Indian River Lagoon, in driving hypoxia. The team discovered that these muck deposits contribute to oxygen depletion up to 500 meters away from their physical footprint. This process disrupts the healthy organisms and bacteria that typically maintain oxygenated sediment, which acts as a barrier against phosphorus trapped underneath. When these organisms die, the phosphorus is released back into the water, initiating a cycle that promotes further algal blooms.
Frequency and Future Research
Although hypoxic events in the estuary can be brief, they occur frequently. Data collected by the researchers showed that sensors recorded hypoxic conditions somewhere in the lagoon 90% of the time. This paper marks the first time internal nutrient loading has been documented in this estuary. Future research will aim to quantify the effects of this hypoxia to help develop potential solutions for managing internal nutrient loading.
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This article was independently rewritten by ManyPress editorial AI from reporting originally published by Phys.org.
