Upwelling buffers climate change impacts on coral reefs of the eastern tropical Pacific

Abstract

Corals of the eastern tropical Pacific live in a marginal and oceanographically dynamic environment. Along the Pacific coast of Panam a, stronger seasonal upwelling in the Gulf of Panam a in the east transitions to weaker upwelling in the Gulf of Chiriqu ı in the west, resulting in complex regional oceanographic conditions that drive differential coral-reef growth. Over millennial timescales, reefs in the Gulf of Chiriqu ı recovered more quickly from climatic disturbances compared with reefs in the Gulf of Panam a. In recent decades, corals in the Gulf of Chiriqu ı have also had higher growth rates than in the Gulf of Panam a. As the ocean continues to warm, however, conditions could shift to favor the growth of corals in the Gulf of Panam a, where upwelling may confer protection from high-temperature anomalies.Here we describe the recent spatial and temporal variability in surface oceanography of nearshore environments in Pacific Panam a and compare those conditions with the dynamics of contemporary coral-reef communities during and after the 2016 coral-bleaching event. Although both gulfs have warmed significantly over the last 150 yr, the annual thermal maximum in the Gulf of Chiriqu ı is increasing faster, and ocean temperatures there are becoming more variable than in the recent past. In contrast to historical trends, we found that coral cover, coral survival, and coral growth rates were all significantly higher in the Gulf of Panam a. Corals bleached extensively in the Gulf of Chiriqu ı following the 2015-2016 El Niño event, whereas upwelling in the Gulf of Panam a moderated the high temperatures caused by El Niño, allowing the corals largely to escape thermal stress. As the climate continues to warm, upwelling zones may offer a temporary and localized refuge from the thermal impacts of climate change, while reef growth in the rest of the eastern tropical Pacific continues to decline.

Seasonal upwelling reduces herbivore control of tropical rocky intertidal algal communities

“…The interannual and seasonal water temperature patterns we describe are consistent with a contemporaneous study showing that upwelling in the Gulf of Panama acted as a thermal buffer against increases in temperature during the 2016–2017 El Niño (Randall et al 2020). Our results indicate that as ENSO conditions shifted from a warm phase to a cool phase, wet season and dry season water temperatures declined in the Gulf of Chiriqui.…”

Climate and the latitudinal limits of subtropical reef development

“…In addition, marginal reefs in the eastern tropical Pacific that experienced strong, seasonal, cold-water upwelling were more vulnerable to millennial-scale climatic perturbations during the Holocene than reefs with more stable annual temperatures (i.e., in the Gulf of Panama 8 and the Gulf of Papagayo, Costa Rica 13 ). Whereas moderate levels of thermal variability can increase the resilience of reefs to modern climatic extremes 21 , 22 , 70 , 71 , these studies of Holocene reef development suggest that in marginal habitats, where variability in the physical environment is especially high, periodic disturbances may be more likely to push reefs past critical environmental thresholds for continued survival and reef-building 9 , 11 , 22 , 71 .…”

“…In environments where thermal conditions are marginal, even minor cooling has the potential to suppress or even shut down reef-building by species that evolved in the tropics 4,9,11,14,17,18 . Whereas a number of recent studies have suggested that marginal environments-highlatitude habitats, mesophotic reefs, and locations with elevated turbidity or upwelling-could serve as refugia from warming for thermally sensitive coral taxa [19][20][21][22] , most of these ecosystems do not support reef accretion at present 20 . An important question, therefore, is whether and how the response of marginal reefs to climatic trends in the past can be used to project the future development of today's degrading reef ecosystems 6,7 in response to anthropogenic warming trends and the impact of those recent trends on both warm and cold thermal extremes.…”

Seasonal and Interannual Variability in the Sea Surface Temperature Front in the Eastern Pacific Ocean

“…Thus, fronts can modify the wind field and subsequently influence regional circulation (De Szoeke et al., 2007; Xie et al., 1998). A better knowledge of frontal variability in the eastern Pacific Ocean could improve the understanding of ecosystem variability, air‐sea coupling and their underlying dynamics at both regional and global scales (Bakun et al., 2015; Randall et al., 2019).…”