Q&A: Researchers Probe How Health of California’s Kelp Forests Affects Other Systems

Fish swimming in the ocean with diverse other sea life

Kelp forests provide habitat for a diverse array of sea life, from finfish and shellfish to corals and sponges. (Photo by Ron McPeak)

The National Science Foundation has awarded a $1.2 million grant to a University of Virginia-led team of scientists for a study to better understand how changes in climate and coastal food webs are affecting kelp forests in the waters off of California. The researchers are investigating a natural phenomenon called synchrony – how changes to an ecosystem in one location are mirrored by ecosystem changes at other locations.

Giant kelp is the largest of all algae, towering 100 feet or more above the seafloor, and is among the fastest-growing organisms on Earth, lengthening over a foot per day under good conditions. Underwater forests formed by giant kelp are among the most productive ecosystems in the world and sustain many coastal fisheries. But kelp forests are undergoing stress as their environment changes due to human activities.

Max Castorani, an assistant professor of environmental sciences and lead investigator for the project, and Jonathan Walter, an environmental sciences research associate, discuss their research for readers of UVA Today.

Q. What is synchrony in nature?

Walter: Synchrony happens when things change in a simultaneous or coordinated way. Synchrony is found all over nature – the flashing patterns of certain fireflies, outbreaks of agricultural pests, and epidemics of infectious diseases.

Jonathan Walter headshot

Jonathan Walter is a research associate of environmental sciences who is studying kelp ecosystems off California’s coast. (Contributed photo)

Our work focuses on the synchrony of plant and animal populations. Remarkably, the number of organisms in different places, even across hundreds of miles, can change in the same way through time.

Q. Why is it important to understand this phenomenon?

Walter: When populations in different places tend to rise and fall together, these synchronous changes add up to create much bigger swings in the total number of organisms than when populations fluctuate independently, without synchrony. These large synchronized fluctuations can destabilize populations and reduce their capacity to recover from disturbance. In extreme cases, synchrony can increase the risk of population extinction.

Understanding spatial synchrony can improve management and conservation of valuable or threatened species. For example, just as an investor seeks a variety of stocks to stabilize the overall value of a retirement portfolio, a salmon fishery manager can stabilize the overall fishery by reducing the synchrony of different salmon populations.

In theory, the synchrony of large habitat-forming organisms, like trees in a forest or kelp in coastal seas, can shape the stability of entire ecosystems. But this prediction has not been well studied. Testing this idea is a major goal of the grant.

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Additionally, recent studies suggest that climate change is altering the strength of synchrony and which places are synchronized with one another. Understanding changes in the synchrony of pests, diseases and food resources can help us mitigate and adapt to climate change.

Q. How will you use the grant?

Castorani: Our work focuses on the synchrony of underwater kelp forests in coastal California. These kelp forests are among the largest in the world and provide great environmental and economic value. For decades, marine biologists have wondered why kelp forests hundreds of miles apart change in the same way over time. Resolving this challenge will help us anticipate the conditions that cause kelp forests to shift from stable, resilient populations to unstable, vulnerable ones.

Max Castorani headshot

Environmental sciences professor Max Castorani leads the project to understand synchrony in nature, using kelp forests as a model. (Contributed photo)

We are also curious how the synchrony of kelp forests affects the biodiversity of associated animal communities. Kelp forests are home to hundreds of species of fish and shellfish, which may be stabilized or destabilized by changes in kelp synchrony. Dead kelp that washes ashore after storms is vital to several species of shorebirds that are threatened by human activities. We will be exploring how the synchronous growth or loss of kelp affects these animals.

Studying synchrony is complex. To meet this challenge, we are bringing together an interdisciplinary team of researchers with expertise in marine biology and statistics from across four universities (UVA, University of Kansas, the University of California at Santa Barbara, and the University of California at Los Angeles). We are using new statistical tools to analyze data collected over the past four decades by a variety of coastal monitoring groups.

Because these kelp forests are so large that they are visible from space, we are also using a 36-year record gathered from satellite images to study synchrony. Through our research, we will train several students and create a Coastal-Heartland Marine Biology Exchange of students across universities.

Q. Why do you use kelp as your model, and what are the ripple effects of synchrony beyond kelp forests as climate changes?

Castorani: Kelp forests are ideal for studying synchrony because of their rapid growth, which allows us to witness a lot of change in a short period of time. If we wanted to do the same study in oak or redwood forests, we would need centuries.

Kelp forests provide tremendous value to society, and are essential to healthy fisheries. They also enhance ecotourism by supporting unique and abundant biodiversity, which attracts scuba divers and kayakers from across the world. Kelp can also be sustainably harvested for food or raw materials for industry. But recent declines of kelp in Northern California have led to the collapse of fisheries for abalone and sea urchins, costing many jobs and millions of dollars.

We hope our work will illuminate how kelp forests are changing in rapidly warming coastal seas. Marine heat waves, which are harmful to kelp and other marine life, may be causing synchronous loss of kelp forests, which could destabilize coastal ecosystems across entire regions. We suspect that climate events, like El Niño, play a big role in synchronizing kelp forests and other ecosystems. Climate change will likely affect the timing and severity of these events, with potentially dramatic implications for kelp forests. We anticipate that a better understanding of kelp forest synchrony will improve regional conservation management by identifying areas to prioritize for restoration or protection.

We anticipate that the new statistical methods that we develop through this project will be useful to ecologists studying synchrony in other ecosystems, as well to researchers in other disciplines, such as those studying medicine and infectious diseases.

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