Boring sponges, an increasing threat for coral reefs affected by bleaching events

Abstract

Coral bleaching is a stress response of corals induced by a variety of factors, but these events have become more frequent and intense in response to recent climate-change-related temperature anomalies. We tested the hypothesis that coral reefs affected by bleaching events are currently heavily infested by boring sponges, which are playing a significant role in the destruction of their physical structure. Seventeen reefs that cover the entire distributional range of corals along the Mexican Pacific coast were studied between 2005/2006, and later between 2009/2010. Most of these coral reefs were previously impacted by bleaching events, which resulted in coral mortalities. Sponge abundance and species richness was used as an indicator of bioerosion, and coral cover was used to describe the present condition of coral reefs. Coral reefs are currently highly invaded (46% of the samples examined) by a very high diversity of boring sponges (20 species); being the coral reef framework the substrate most invaded (56%) followed by the rubbles (45%), and the living colonies (36%). The results also indicated that boring sponges are promoting the dislodgment of live colonies and large fragments from the framework. In summary, the eastern coral reefs affected by bleaching phenomena, mainly provoked by El Niño, present a high diversity and abundance of boring sponges, which are weakening the union of the colony with the reef framework and promoting their dislodgment. These phenomena will probably become even more intense and severe, as temperatures are projected to continue to rise under the scenarios for future climate change, which could place many eastern coral reefs beyond their survival threshold.

Post-bleaching coral community change on southern Maldivian reefs: is there potential for rapid recovery?

“…Lasagna et al 2010). Our field observations also suggest that much of this dead in situ framework is infested by endolithic sponges and that this, along with the elevated parrotfish biomass we report, is likely to speed this process up (see Carballo et al 2013). Extrapolation of these findings to the wider Maldives obviously requires caution, but it is pertinent to mention that we observed similar widespread coral mortality on reefs within and around two more northern atolls (Gooidoo and Baa) in March 2017, and that widespread mortality was reported across the region immediately after the 2016 event (IUCN 2016).…”

40 Years of benthic community change on the Caribbean reefs of Curaçao and Bonaire: the rise of slimy cyanobacterial mats

“…However, new studies describe a recent increase in sponge densities (e.g. Loh et al 2015;McMurray et al 2015), in particular coralexcavating sponges (Ward-Paige et al 2005;Carballo et al 2013). Although sponges are generally not able to rapidly colonise newly available substratum, they are strong competitors for space.…”

Pervasive genetic structure at different geographic scales in the coral-excavating sponge Cliona vermifera (Hancock, 1867) in the Mexican Pacific

“…Coral-excavating sponges are an essential component of coral reef ecosystems (Carballo et al 2008a, b), and recent studies suggest a future increase in sponge bioerosion as an outcome of coral reef decline around the world (Nava and Carballo 2008;Schönberg and Ortiz 2008;Wisshak et al 2012;Carballo et al 2013b). Despite their ecological importance, the population dynamics of coral-excavating sponges, including how populations are genetically structured and connected in space and time, remain largely unknown.…”