The ability of invasive seaweed to adapt to ocean changes could be one reason why they outcompete native species, according to a new study by University of Hawaiʻi at Mānoa researchers.
Botanists who recently published a study in the journal Scientific Reports found that gorilla ogo, spiny seaweed and other invasive seaweed dominate native limu in Hawaiʻi’s coastal waters.
Those invasive species are common in areas such as Oʻahu’s south and east shores, and in parts of Hilo and Maui.
The scientists wanted to learn how the invasive species can outcompete native species, particularly in areas where fresh groundwater seeps into the ocean and causes extreme fluctuations in salinity, which can drive water in or out of a plant’s cells and cause them to shrivel or burst.
Invasive seaweed species were found to live in areas where freshwater and seawater mix, but native species cannot.
“Understanding how invasive seaweed outcompetes native limu is crucial to furthering our knowledge about reefs and ocean environments,” Veronica Gibson, a researcher at the UH Mānoa’s Hawaiʻi Institute of Marine Biology and Heʻeia National Estuarine Research Reserve, said in a statement.
The researchers found that the invasive species can thrive in those areas because their cells can handle the changes in the ocean water when mixed with freshwater.
Gibson said studying the invasive and native seaweeds helps us understand and protect coastal ecosystems, which are important to humans.
“These spring-fed coastal areas are unique ecosystems that connect our land use practices directly to ocean health, and what happens to limu — which forms the base of our marine food web — affects everything from the fish we catch to the overall health of our coral reefs,” she said.
Human activity can also play a role in the discharge of underground water into the oceans, affecting those nearshore areas.
