Researchers, led by Dr. Douglas Tait from Southern Cross University, employed natural indicators along Queensland's coastline to identify the origin of previously unmeasured nitrogen and phosphorus pollutants affecting the Great Barrier Reef's environment significantly.
The findings of the study, titled "Submarine groundwater discharge surpasses river contributions as a nutrient source for the Great Barrier Reef," are published in the journal of Environmental Science & Technology.
Too Much Nutrients Affect the Great Barrier Reef
A research team, including scientists from Southern Cross University, CSIRO, AIMS, and Gothenburg University in Sweden, conducted a study on submarine groundwater discharge, which involves water released to the ocean below the waterline from sources like underground aquifers and the seafloor.
They collected data across a coastal region spanning from south of Rockhampton to north of Cairns, using radium isotopes to trace nutrient transport from land and shelf sediments through hidden groundwater flows.
The study's findings revealed that groundwater discharge is a substantial and previously underestimated source of nutrients for the Great Barrier Reef.
Groundwater discharge was found to be 10-15 times greater than river inputs, contributing approximately one-third of new nitrogen and two-thirds of phosphorous inputs to the reef. This means that nearly twice as much nitrogen enters the reef from groundwater compared to river water.
The majority of conservation efforts had previously focused on managing nutrient inputs from river systems, but this research emphasizes the need for a reevaluation of conservation strategies.
Excess nutrients, while essential for the reef's biodiversity, can lead to harmful issues such as algal blooms, crown-of-thorns starfish outbreaks, and fish diseases, which have been increasing in the reef over the past decades.
Unlike river outflows, nutrients in groundwater can be stored underground for extended periods before being discharged into coastal waters, necessitating long-term research and strategies to protect the reef effectively.
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Paradigm Shift Needed To Protect the Great Barrier
Dr. Douglas Tait, the lead author, highlighted the importance of understanding and managing nutrient sources in preserving the Great Barrier Reef for future generations, emphasizing the need for a strategic shift in conservation approaches.
To address this issue, it is essential to implement improved land management practices aimed at reducing the influx of nutrients into groundwater aquifers.
Additionally, we can employ ecological approaches, such as seaweed and bivalve aquaculture, as well as enhance seagrass, oyster reefs, mangroves, and salt marshes, coupled with hydrological methods to enhance flushing in areas where groundwater discharge is a major source of excess nutrients in the water.
Furthermore, exploring the potential for reusing nutrient-rich groundwater for agricultural purposes presents an untapped and cost-effective source of nutrients. Unlike nutrient inputs from rivers, which have an immediate impact, nutrients in groundwater can remain stored underground for extended periods, even decades, before being released into coastal waters.
Consequently, this underscores the importance of adopting long-term research and strategies to protect the reef effectively, as the delayed release of stored nutrients may pose significant challenges in the future.
It is crucial to recognize that understanding and managing nutrient sources are critical components of preserving coral reef ecosystems globally. While mitigating the impact of climate change on these delicate ecosystems is essential, adjusting policies to regulate nutrient inputs is equally vital to ensure the long-term health and sustainability of the Great Barrier Reef for future generations.
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