title: Assessing coral reefs on a Pacific-wide scale using the microbialization score.
abstract: The majority of the world's coral reefs are in various stages of decline. While a suite of disturbances (overfishing, eutrophication, and global climate change) have been identified, the mechanism(s) of reef system decline remain elusive. Increased microbial and viral loading with higher percentages of opportunistic and specific microbial pathogens have been identified as potentially unifying features of coral reefs in decline. Due to their relative size and high per cell activity, a small change in microbial biomass may signal a large reallocation of available energy in an ecosystem; that is the microbialization of the coral reef. Our hypothesis was that human activities alter the energy budget of the reef system, specifically by altering the allocation of metabolic energy between microbes and macrobes. To determine if this is occurring on a regional scale, we calculated the basal metabolic rates for the fish and microbial communities at 99 sites on twenty-nine coral islands throughout the Pacific Ocean using previously established scaling relationships. From these metabolic rate predictions, we derived a new metric for assessing and comparing reef health called the microbialization score. The microbialization score represents the percentage of the combined fish and microbial predicted metabolic rate that is microbial. Our results demonstrate a strong positive correlation between reef microbialization scores and human impact. In contrast, microbialization scores did not significantly correlate with ocean net primary production, local chla concentrations, or the combined metabolic rate of the fish and microbial communities. These findings support the hypothesis that human activities are shifting energy to the microbes, at the expense of the macrobes. Regardless of oceanographic context, the microbialization score is a powerful metric for assessing the level of human impact a reef system is experiencing.
authors.affiliation: Biology Department, San Diego State University, San Diego, California, United States of America. tsmcdole@yahoo.com
authors.forename: Tracey
authors.initials: T
authors.lastname: McDole
authors.forename: James
authors.initials: J
authors.lastname: Nulton
authors.forename: Katie L
authors.initials: KL
authors.lastname: Barott
authors.forename: Ben
authors.initials: B
authors.lastname: Felts
authors.forename: Carol
authors.initials: C
authors.lastname: Hand
authors.forename: Mark
authors.initials: M
authors.lastname: Hatay
authors.forename: Hochul
authors.initials: H
authors.lastname: Lee
authors.forename: Marc O
authors.initials: MO
authors.lastname: Nadon
authors.forename: Bahador
authors.initials: B
authors.lastname: Nosrat
authors.forename: Peter
authors.initials: P
authors.lastname: Salamon
authors.forename: Barbara
authors.initials: B
authors.lastname: Bailey
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Sandin
authors.forename: Bernardo
authors.initials: B
authors.lastname: Vargas-Angel
authors.forename: Merry
authors.initials: M
authors.lastname: Youle
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Zgliczynski
authors.forename: Russell E
authors.initials: RE
authors.lastname: Brainard
authors.forename: Forest
authors.initials: F
authors.lastname: Rohwer
mesh_terms: D000818:Animals; D001419:Bacteria / Q000378:metabolism*; D001481:Basal Metabolism; D057894:Coral Reefs; D004734:Energy Metabolism; D005399:Fishes / Q000378:metabolism; D006802:Human Activities; D006801:Humans; D062312:Islands; D016014:Linear Models; D010140:Pacific Ocean