Researchers Identify Chemicals From Turf Algae as Cause for Decline in Seaweed Forests

From the Baltic Sea to South Australia and from the Atlantic to the Pacific, researchers are investigating the rapid disappearance of kelp forests, which could have enormous repercussions on ocean health and marine ecosystems. 

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To unravel who or what is responsible for these deaths, scientists are employing techniques akin to fingerprint identification to document the causal relationship leading to the loss of kelp forests. 

These losses are particularly troubling as the kelp – or seaweed – forests, located at temperate latitudes, are situated along approximately 25% of the world’s coasts and are crucial for ocean health. Their loss has implications for marine ecosystems around the globe and their resilience to continued disturbance. 

Scientists at Bigelow Laboratory for Ocean Sciences in Maine and others at the University of California, Riverside used chemical ecology to explore how turf or filamentous algae inhibited the growth of young kelp. Their research revealed that turf algae released molecules that inhibited the survival of kelp. In addition, a comparison of the chemical and biological makeup of the turf algae versus seaweed landscapes yielded a distinct difference between them.

Chemical cues are known to be important in the early, life-history stages of marine organisms like corals and kelp. Adult kelp plants exude chemical compounds that signal kelp spores they are in an area suitable for settlement and growth. 

However, warming ocean temperatures have led to a decline in kelp – and scientists are trying to understand why.

Recent research suggests that the changes in ocean temperature alter marine ecosystems by disrupting its chemical landscape. As warmer waters favor the establishment of turf algae, the algae release chemical compounds that inhibit the growth of young kelp. The chemically mediated interaction is known as allelopathy, with the end result being the collapse of kelp forests. Because kelp forests are considered to have “some of the highest rates of primary production of any natural ecosystem on Earth,” the loss of the kelp forests results in a concomitant decrease “in biodiversity, productivity and the ecosystem services they provide to humans.” 

The chemical changes brought about by the turf algae fundamentally altered the marine ecosystem due to a chemical feedback loop that favors turf algae over kelp forest. These findings are troubling as they reveal “an indirect way that climate change is reshaping ocean ecosystems.”

As a recent study suggests, the link between chemical ecology and ecosystem changes in the kelp forest provide valuable pathways that future management decisions and conservation efforts might consider.

Featured image: Nuno Vasco Rodrigues / Climate Visuals Countdown.