Cyclone Impacts on Coral Reef Communities in Southwest Madagascar

Abstract

Tropical cyclones can cause severe destruction of coral reefs with ecological consequences for reef fish communities. Ocean warming is predicted to shorten the return interval for strong tropical cyclones. Understanding the consequences of cyclone impacts on coral reefs is critical to inform local-scale management to support reef resilience and the livelihood security of small-scale fishing communities. Here, we present the first analysis of a tropical cyclone disturbance on coral reefs in Madagascar. We investigate the impact of Cyclone Haruna (category 3 Saffir-Simpson scale) in February 2013 on coral communities, both adults and recruits, and explore the relationship between the severity of cyclone impact with cyclone parameters (wind speed, duration of storm impact and distance from cyclone track) and environmental variables (reef type and reef depth). We use survey data collected as part of a long-term citizen science monitoring programme at 21 coral reef sites between 2012 and 2015 in the Velondriake Locally Managed Marine Area along Madagascar’s southwest coast. Coral cover declined at 19 sites, however damage was spatially heterogeneous ranging from a decrease in coral cover of 1.4% to 45.8%. We found the severity of cyclone damage related to: distance from the cyclone track, duration of cyclone impact and reef depth. The taxonomic and morphological composition of coral communities was significantly different after the cyclone. Notably, there was a decrease in the dominance of branching morphologies, and an increase in the relative abundance of encrusting and massive morphologies. Two years after Cyclone Haruna, mean coral cover had increased and the density of coral recruits increased to above pre-cyclone levels indicating the potential recovery of coral populations. However, recovery to pre-disturbance community composition will likely be hindered by the increasing occurrence of acute and chronic disturbance events.

Coral recruitment in the Toliara region of southwest Madagascar: Spatio‐temporal variability and implications for reef conservation

“…Thermal stress in 2001, 2006, 2009, and 2021 (Figure S1) has likely caused mild effects on coral assemblages of the GRT, but no mass bleaching events were reported. Cyclones are less frequent in the southwest coast of Madagascar compared to the eastern coast or to other regions in the SWIO, and though Cyclone Haruna passed 120 km north of Toliara in February 2013 (Carter et al., 2022), no significant impacts on the GRT were reported. Similarly, outbreaks of the coral predator Acanthaster spp.…”

“…Cyclones are less frequent in the southwest coast of Madagascar compared to the eastern coast or to other regions in the SWIO, and though Cyclone Haruna passed 120 km north of Toliara in February 2013 (Carter et al, 2022), no significant impacts on the GRT were reported. Similarly, outbreaks of the coral predator Acanthaster spp.…”

“…While spatial patterns and the community structure of coral assemblages around Madagascar have been documented, with recent progress on the effects of environmental factors and MPAs at local (Botosoamananto et al, 2021;Carter et al, 2022) and regional (Randrianarivo et al, 2022) scales, studies have not examined coral recruitment processes, with the exception of a preliminary study by Todinanahary et al (2021). This lack of knowledge on coral recruitment at Madagascar contrasts with several studies conducted in the South Western Indian Ocean (SWIO) region and investigations in Kenya (Mangubhai et al, 2007), Seychelles (Chong-Seng et al, 2014), Mozambique (Sola et al, 2015), Mascarene Islands (Jouval et al, 2019), and South Africa (Glassom et al, 2006).…”

“…While spatial patterns and the community structure of coral assemblages around Madagascar have been documented, with recent progress on the effects of environmental factors and MPAs at local (Botosoamananto et al., 2021; Carter et al., 2022) and regional (Randrianarivo et al., 2022) scales, studies have not examined coral recruitment processes, with the exception of a preliminary study by Todinanahary et al. (2021).…”

A contemporary baseline of Madagascar’s coral assemblages: Reefs with high coral diversity, abundance, and function associated with marine protected areas

“…In recent decades, these reefs have been impacted by the bleaching event of 1998 [ 70 , 76 ], and 2016 [ 77 ] ( S1 Table ). The major cyclones that had a potential impact on coral assemblages are Haruna at Salary Nord in 2013, Enawo 2017 at Masoala and Nosy-Be in 2017, and Belan at Nosy-Be in 2019 [ 78 ]. However, the impact of these disturbances on coral assemblages in our three regions has not been quantified.…”