From The University of Michigan: “Study concludes: not enough – Protecting algae-eating fish insufficient to save imperiled coral reefs”

U Michigan bloc

From The University of Michigan

10.3.22 [Just today in social media]
Jim Erickson

Bright blue Chromis fish on acropora coral at a back reef on the French Polynesian island of Mo’orea. Image credit: Kelly Speare.

How can we boost the resilience of the world’s coral reefs, which are imperiled by multiple stresses including mass bleaching events linked to climate warming?

One strategy advocated by some researchers, resource managers and conservationists is to restore populations of algae-eating reef fish, such as parrotfish. Protecting the fish that keep algae in check leads to healthier corals and can promote the recovery of distressed reefs, according to this idea, which is known as fish-mediated resilience.

But a new study that analyzed long-term data from 57 coral reefs around the French Polynesian island of Mo’orea challenges this canon of coral reef ecology.

The study, published online Oct. 3 in the journal Nature Ecology & Evolution [below], provides compelling new evidence that fish don’t regulate coral over time, according to University of Michigan marine ecologist and study co-senior author Jacob Allgeier.

Jacob Allgeier

The other author is former U-M postdoctoral researcher Timothy Cline.

“This paper very well might radically change how we think about the conservation of coral reefs,” said Allgeier, assistant professor in the U-M Department of Ecology and Evolutionary Biology.

“People have been saying for years that we can protect coral through fisheries management, and our work on Mo’orea reefs shows that this is unlikely to work—there are too many other things going on. There is functionally no measurable effect of fishes on coral cover over time.”

Support for the idea of fish-mediated coral reef resilience has led to calls for moratoriums on fishing for algae-eating reef fish to prevent algae overgrowth and reef degradation. Such well-intentioned but misguided management strategies could have huge implications for the millions of people who depend on coral-reef fisheries for food and income, according to the authors of the new study.

Instead, it makes more sense to support strategies that promote the conservation of diverse habitats and coral reef types at various stages of degradation, the researchers said.

“We do need to manage fisheries in these ecosystems, but instead of things like wholesale restrictions on parrotfish, we should consider management efforts that promote sustainable harvest throughout the food web to disperse the impacts of fishing,” Allgeier said.

Shallow forereef locations off the northern shore of Mo’orea. Image credit: Kelly Speare.

Forereef locations off the northern shore of the French Polynesian island of Mo’orea. Image credit: Kelly Speare.

Turbinaria algae coat the corals, foreground, at a north shore reef on the French Polynesian island of Mo’orea. Turbinaria is a genus of brown algae found primarily in tropical marine waters. Yellow-and-black convict tangs, an algae-eating fish, are in the background. Image credit: Kelly Speare.

A relatively healthy backreef location locally on the French Polynesian island of Mo’orea. Image credit: Kelly Speare.

Coral reefs are among the most biodiverse and productive ecosystems on the planet, but they are also among the most imperiled and rapidly changing.

Threats to coral reefs include predatory species, nutrient pollution, ocean acidification, overfishing, sedimentation and coral bleaching, which is caused by sustained, warmer-than-average sea surface temperatures. As the climate warms, mass bleaching events are lasting longer, becoming more frequent, and are affecting reefs that are completely protected from all human impacts other than climate change, Allgeier said.

The new study involves a series of statistical analyses of coral reef data collected between 2006 and 2017 by two long-term monitoring projects: the Mo’orea Coral Reef Ecosystem LTER (funded by the U.S. National Science Foundation) and the Centre de Recherches Insulaires et Observatoire de l’Environnement (funded by the French government).

The Mo’orea coral reef datasets contain some of the longest continuous observations of fish populations and algae growth on coral reefs.

School of striped convict tangs on a relatively healthy backreef on the French Polynesian island of Mo’orea. Image credit: Kelly Speare.

Macroalgae, commonly known as seaweed, compete with corals for seafloor space and can smother them if they grow too dense. If corals are weakened by a bleaching event or some other disturbance, macroalgae often move in and displace them.

During the 2006-17 data-collection period analyzed in the study, Mo’orea coral reefs were significantly impacted by two major disturbances: an outbreak of the coral-eating crown-of-thorns starfish and a direct hit from Cyclone Oli in winter 2010.

The two events allowed Allgeier and Cline to study the degradation and subsequent recovery of the Mo’orea reefs and to assess the factors that contributed to the recovery. They used mathematical models to test the hypothesis that the rate at which corals recovered correlated with various attributes of the fish community, including species diversity, biomass and richness.

“We found no evidence that the substantial variation in fish community biomass and diversity had any influence on how sites recovered from disturbances,” Cline said. “Instead, we suggest additional location-specific attributes are critical in recovery, and the fish community is just one component of a suite of variables that must be considered.”

Support for the study was provided by the David and Lucile Packard Foundation and the National Science Foundation.

Science paper:
Nature Ecology & Evolution

See the full article here .


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The University of Michigan is a public research university located in Ann Arbor, Michigan, United States. Originally, founded in 1817 in Detroit as the Catholepistemiad, or University of Michigania, 20 years before the Michigan Territory officially became a state, the University of Michigan is the state’s oldest university. The university moved to Ann Arbor in 1837 onto 40 acres (16 ha) of what is now known as Central Campus. Since its establishment in Ann Arbor, the university campus has expanded to include more than 584 major buildings with a combined area of more than 34 million gross square feet (781 acres or 3.16 km²), and has two satellite campuses located in Flint and Dearborn. The University was one of the founding members of the Association of American Universities.

Considered one of the foremost research universities in the United States, the university has very high research activity and its comprehensive graduate program offers doctoral degrees in the humanities, social sciences, and STEM fields (Science, Technology, Engineering and Mathematics) as well as professional degrees in business, medicine, law, pharmacy, nursing, social work and dentistry. Michigan’s body of living alumni (as of 2012) comprises more than 500,000. Besides academic life, Michigan’s athletic teams compete in Division I of the NCAA and are collectively known as the Wolverines. They are members of the Big Ten Conference.

At over $12.4 billion in 2019, Michigan’s endowment is among the largest of any university. As of October 2019, 53 MacArthur “genius award” winners (29 alumni winners and 24 faculty winners), 26 Nobel Prize winners, six Turing Award winners, one Fields Medalist and one Mitchell Scholar have been affiliated with the university. Its alumni include eight heads of state or government, including President of the United States Gerald Ford; 38 cabinet-level officials; and 26 living billionaires. It also has many alumni who are Fulbright Scholars and MacArthur Fellows.


Michigan is one of the founding members (in the year 1900) of the Association of American Universities. With over 6,200 faculty members, 73 of whom are members of the National Academy and 471 of whom hold an endowed chair in their discipline, the university manages one of the largest annual collegiate research budgets of any university in the United States. According to the National Science Foundation, Michigan spent $1.6 billion on research and development in 2018, ranking it 2nd in the nation. This figure totaled over $1 billion in 2009. The Medical School spent the most at over $445 million, while the College of Engineering was second at more than $160 million. U-M also has a technology transfer office, which is the university conduit between laboratory research and corporate commercialization interests.

In 2009, the university signed an agreement to purchase a facility formerly owned by Pfizer. The acquisition includes over 170 acres (0.69 km^2) of property, and 30 major buildings comprising roughly 1,600,000 square feet (150,000 m^2) of wet laboratory space, and 400,000 square feet (37,000 m^2) of administrative space. At the time of the agreement, the university’s intentions for the space were not set, but the expectation was that the new space would allow the university to ramp up its research and ultimately employ in excess of 2,000 people.

The university is also a major contributor to the medical field with the EKG and the gastroscope. The university’s 13,000-acre (53 km^2) biological station in the Northern Lower Peninsula of Michigan is one of only 47 Biosphere Reserves in the United States.

In the mid-1960s U-M researchers worked with IBM to develop a new virtual memory architectural model that became part of IBM’s Model 360/67 mainframe computer (the 360/67 was initially dubbed the 360/65M where the “M” stood for Michigan). The Michigan Terminal System (MTS), an early time-sharing computer operating system developed at U-M, was the first system outside of IBM to use the 360/67’s virtual memory features.

U-M is home to the National Election Studies and the University of Michigan Consumer Sentiment Index. The Correlates of War project, also located at U-M, is an accumulation of scientific knowledge about war. The university is also home to major research centers in optics, reconfigurable manufacturing systems, wireless integrated microsystems, and social sciences. The University of Michigan Transportation Research Institute and the Life Sciences Institute are located at the university. The Institute for Social Research (ISR), the nation’s longest-standing laboratory for interdisciplinary research in the social sciences, is home to the Survey Research Center, Research Center for Group Dynamics, Center for Political Studies, Population Studies Center, and Inter-Consortium for Political and Social Research. Undergraduate students are able to participate in various research projects through the Undergraduate Research Opportunity Program (UROP) as well as the UROP/Creative-Programs.

The U-M library system comprises nineteen individual libraries with twenty-four separate collections—roughly 13.3 million volumes. U-M was the original home of the JSTOR database, which contains about 750,000 digitized pages from the entire pre-1990 backfile of ten journals of history and economics, and has initiated a book digitization program in collaboration with Google. The University of Michigan Press is also a part of the U-M library system.

In the late 1960s U-M, together with Michigan State University and Wayne State University, founded the Merit Network, one of the first university computer networks. The Merit Network was then and remains today administratively hosted by U-M. Another major contribution took place in 1987 when a proposal submitted by the Merit Network together with its partners IBM, MCI, and the State of Michigan won a national competition to upgrade and expand the National Science Foundation Network (NSFNET) backbone from 56,000 to 1.5 million, and later to 45 million bits per second. In 2006, U-M joined with Michigan State University and Wayne State University to create the the University Research Corridor. This effort was undertaken to highlight the capabilities of the state’s three leading research institutions and drive the transformation of Michigan’s economy. The three universities are electronically interconnected via the Michigan LambdaRail (MiLR, pronounced ‘MY-lar’), a high-speed data network providing 10 Gbit/s connections between the three university campuses and other national and international network connection points in Chicago.