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Home / Science / How Submarine Groundwater Affects Coral Reef Growth – University of Hawai'i System News

How Submarine Groundwater Affects Coral Reef Growth – University of Hawai'i System News



Maunalua Bay. (Photo: Florybeth La Valle, HIMB / SOEST )

Groundwater entering the coastal zone below the surface of the sea ̵

1; referred to as submarine groundwater runoff ( SGD ) – is an important source of fresh water and nutrients to nearshore coral reefs around the world. Although submarine groundwater is natural, it can serve as a channel for heavily polluted water to shorelines.

A recent study, led by researchers at the University of Hawai & # 39; i at Mānoa School of Ocean and Earth Science and Technology ( SOEST ), illuminates the type and How SGD affects the growth of coral reefs.

"SGD is widespread on nearshore coral reefs, especially in Hawai & # 39; i and so we began to test how SGD affected coral reef growth in Maunalua Bay O'Ahu said Megan Donahue Deputy Researcher at Hawai'i Institute of Marine Biology in SOEST and senior author of Study

Too much groundwater pollutes corals

Coral pieces show growth after six months of use at the reef. (Photo: K Lubarsky, HIMB / SOEST )

Two processes contribute to Coral reefs' overall growth in: Coral growth and bioerosion, the natural degradation of coral reefs by reef organisms In order to determine how SGD affects these processes, the research team has small pieces of lobed coral on the reef surface in areas planted with a range of SGD and the changes over a six-month period. They also exhibited blocks of dead coral skeletons over the same SGD gradients for one year to measure bioerosion rates.

The blocks were scanned before and after use with a microcomputer tomography ( CT ) scanner, similar to a hospital CT scanner, to determine the amount of coral skeleton produced by bioerodating Organisms in three dimensions has been removed. In areas with high SGD it was a double strike for coral reefs. Corals seeping right next to SGD showed poor performance, probably due to exposure to too much fresh water.

"In addition, we found that marine organisms responsible for bioerosion quickly broke the skeletal trapping when exposed to high levels of SGD ," said lead author Katie Lubarsky Research completed as part of her degree in marine biology at UH Mānoa. "Many bioerodiferous organisms are filter-eaters that work better in high-nutrient environments, so high-nutrient groundwater is likely to increase bio-eradic activity, suggesting that high levels of nutrient pollution SGD [189] However, to the surprise of the researchers [1949011]SGD promoted coral growth nutrient enrichment and fresh water from the groundwater was low.

Possibility of Coral Extraction in Maunalua Bay

"Our results suggest that corals can thrive on fertilized reefs when attacked by secondary stressors, such as competition from algae and sedimentation," Donahue said. "Maunalua Bay is in a highly urbanized area, and the coral reefs in the bay have deteriorated as populations have boomed in the last 50 years." Active management to reduce invasive algae and limit fine sediment could increase coral recharge Maunalua Bay. "

" While the current study showed that corals grow faster when exposed to low levels of nutrient enrichment, the coral cover remains extremely low on the Maunalua Bay Reef Flats, "said Nyssa Silbiger, study co-author Assistant Professor at California State University, Northridge. "Our next studies will focus on how SGD and herbivory of fish affect coral-algae competition, coral recruitment rates and bioerosion rates."

The research was supported by the UH Sea Grant College program.


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