Rodríguez-Barreras R et al. (2023), Uneven demographic consequences of the 2022 dis...

ECB-ART-52763

PeerJ 2023 Jan 01;11:e16675. doi: 10.7717/peerj.16675.

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Uneven demographic consequences of the 2022 disease outbreak for the sea urchin Diadema antillarum in Puerto Rico.

Rodríguez-Barreras R , Ruiz-Diaz CP , Quiñones-Otero MA , Toledo-Hernández C .

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Pervasive epizootic events have had a significant impact on marine invertebrates throughout the Caribbean, leading to severe population declines and consequential ecological implications. One such event was the regional collapse of herbivory, partly caused by the Diadema antillarum mortality event in 1983-84, resulting in a trophic cascade and altering the structure of reef communities. Consequently, there was a notable decrease in coral recruitment and an increase in the coverage of macroalgae. Nearly four decades later, in early 2022, the Caribbean basin experienced another widespread mass mortality event, further reducing the populations of D. antillarum. To assess the effects of this recent mortality event on the current demographics of D. antillarum, we surveyed eight populations along the eastern, northeastern, northern, and northwestern coast of Puerto Rico from May to July 2022, estimating their population density, size distribution, and disease prevalence. Additionally, the study compared these population parameters with data from four sites previously surveyed in 2012 and 2017 to understand the impact of the recent mortality event. The survey conducted in 2022 showed varying population densities at the surveyed reefs. Some populations exhibited mean densities of nearly one individual per square meter, while others had extremely low or no living individuals per square meter. The four populations with the highest density showed no evidence of disease, whereas the four populations with the lowest D. antillarum densities exhibited moderate to high disease prevalence. However, when considering all sites, the estimated disease prevalence remained below 5%. Nevertheless, the comparison with data from 2012 and 2017 indicated that the recent mortality event had a negative impact on D. antillarum demographics at multiple sites, as the densities in 2022 were reduced by 60.19% compared to those from the previous years. However, it is still too early to determine the severity of this new mortality event compared to the 1983-84 mortality event. Therefore, it is imperative to continue monitoring these populations.

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	Figure 1. Surveyed sites along the eastern and northern coasts of Puerto Rico and Culebra Islands.Punta Tamarindo (PTA) and Punta Melones (PME) in Culebra Island, Punta Bandera (PBA), El Escambrón (ESC), Cerro Gordo (CGO), Playa Sardinera (PSA), Shacks Beach (SBE), and Playa Peña Blanca (PBL). Image credit: Open Street Map. Esri World Imaginary.
	Figure 2. Boxplot showing the 2022 Diadema antillarum abundance across Cerro Gordo (CGO), El Escambrón (ESC), Punta Bandera (PBA), Playa Peña Blanca (PBL), Punta Melones (PME), Playa Sardinera (PSA), Punta Tamarindo (PTA), Shacks Beach (SBE).The red circle represents the mean, the median is represented by the bold line, the extremes of the boxplot are the 1st and 3rd quartiles, and the whiskers are the maximum and minimum. The black dots represent the outliers.
	Figure 3. Boxplot showing the Diadema antillarum density across years 2012, 2017 & 2022 at (A) Cerro Gordo (CGO), (B) Punta Bandera (PBA), (C) Punta Tamarindo (PTA), and (D) Punta Melones (PME).In the boxplot, the yellow circle represents the mean, the median is presented by the bold line, the extreme of the boxplot are the 1st and 3rd quartiles, and the whiskers are the maximum and minimum.
	Figure 4. Boxplot showing the test diameter of Diadema antillarum in 2022 across the study sites (A) and by size categories (B).Sites are Cerro Gordo (CGO), Escambrón (ESC), Punta Bandera (PBA), Playa Peña Blanca (PBL), Punta Melones (PME), Playa Sardinera (PSA), and Shacks Beach (SBE). Size class category: small (≤ 4.0 cm), medium (4.01 to 6.01 cm), and large (>6.01 cm). In the boxplot, the red circle represents the mean, the median is presented by the bold line, the extreme of the boxplot are the 1st and 3rd quartiles, and the whiskers are the maximum and minimum.
	Figure 5. Size categories distribution across years 2012, 2017 and 2022 at four sites, where (A) is Cerro Gordo (CGO), (B) is Punta Bandera (PBA), (C) Punta Melones (PME), and (D) is Punta Tamarindo (PTA).Size class category: small (≤ 4.0 cm), medium (4.01 to 6.0 cm), and large (>6.01 cm).
	Figure 6. Overall disease sea urchin size class distribution in Puerto Rico for the eight surveyed sites in 2022.Notice that no small diseased individuals were observed. In the boxplot, the red circle represents the mean, the median is presented by the bold line, the extreme of the boxplot are the 1st and 3rd quartiles, and the whiskers are the maximum and minimum.

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