Thermal stress and tropical reefs: mass coral bleaching in a stable temperature environment?

Abstract

This study reports on the deepest records (~24 m depth) of coral bleaching in a naturally temperature-stable environment (> 26 °C with an intra-annual variability of ~2 °C), which was recorded during a mass bleaching event in the locally dominant, massive scleractinian coral Siderastrea stellata in equatorial waters of Brazil (SW Atlantic). An inter-annual analysis (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017) indicated that this bleaching event was related to anomalies in sea surface temperature (SST) that led to the warmest year (2010) in this century (1 to 1.7 °C above average). Such anomalies caused heat stress (28.5-29.5 °C) in this equatorial environment that resulted in a bleaching event. Our results suggest that the increase in SST, low turbidity, and weak winds may have acted together to affect these stress-tolerant corals in marginal reefs. The equatorial coastline of Brazil is characterized by low intra-annual and inter-annual variations in SST, which suggests that the S. stellata corals here may be acclimatized to these stable conditions and, consequently, have a lower bleaching threshold because of lower historical heat stress.

A GEE toolkit for water quality monitoring from 2002 to 2022 in support of SDG 14 and coral health in marine protected areas in Belize

“…Images included in the study are Level-3 daily data with a 4 km resolution spanning from 4 July 2002 to 28 February 2022. These images were used to calculate water clarity and sea surface temperature (SST), a combination of water quality parameters used to assess coral health (de Oliveira Soares et al, 2019).…”

“…The NASA operational algorithm was Frontiers in Remote Sensing frontiersin.org used to calculate Kd (490) (Werdell and Bailey, 2005), as we used in our previous study of water clarity in Belizean coastal waters (Callejas et al, 2021). This Kd (490) product has been used for coral health in Brazil (Zoffoli et al, 2013;de Oliveira Soares et al, 2019;Freitas et al, 2019), for an analysis of global corals (Sully and van Woesik, 2020), and corals in the Colombian Caribbean (Vega Sequeda et al, 2017). Daily SST averages for each MPA were calculated using Aqua MODIS imagery.…”

“…SST is important to measure since anomalous warm temperatures can lead to coral bleaching, coral disease, coral death, loss of coral cover, and shifts in biodiversity (Eakin et al, 2010;Hoegh-Guldberg et al, 2017;Obura et al, 2019;Helmuth et al, 2020). Aqua MODIS SST imagery has been used for coral reefs monitoring (de Oliveira Soares et al, 2019;Putra et al, 2019). Daily SST remote sensing products are used in nowcast prediction methods such as calculating HotSpot, Degree Heating Weeks, and ReefTemp (Mason et al, 2020).…”

“…The use of water clarity is important to use in addition to thermal stress data, especially in places such as Belize, where thermally induced bleaching events may play a lesser role compared to anthropogenic causes (Baumann et al, 2019). The Aqua MODIS Kd (490) product using the NASA operational algorithm has been used in global reefs (Sully and van Woesik, 2020;Johnson et al, 2022), Brazil (Zoffoli et al, 2013;de Oliveira Soares et al, 2019;Freitas et al, 2019), andColombian Caribbean (Vega Sequeda et al, 2017). DWH and Kd (490) have been used in combination for coral health (de Oliveira Soares et al, 2019;Muñiz-castillo and Mcfield, 2022).…”

“…The Aqua MODIS Kd (490) product using the NASA operational algorithm has been used in global reefs (Sully and van Woesik, 2020;Johnson et al, 2022), Brazil (Zoffoli et al, 2013;de Oliveira Soares et al, 2019;Freitas et al, 2019), andColombian Caribbean (Vega Sequeda et al, 2017). DWH and Kd (490) have been used in combination for coral health (de Oliveira Soares et al, 2019;Muñiz-castillo and Mcfield, 2022).…”