Short-term in situ shading effectively mitigates linear progression of coral-killing sponge Terpios hoshinota

Abstract

The coral-killing sponge, Terpios hoshinota is a global invasive species that has conquered coral patches within a short span of time, which has led to a significant decline in living coral cover at various geographical locations. In this study, we surveyed the linear progression and impact of the Terpios invasion on live coral patches along Palk Bay, Indian Ocean, from August 2013 to August 2015. The field inventory revealed an extensive fatality rate of 76% as a result of Terpios outbreak. Experimental findings showed that symbiotic cyanobacteria act as a nutritional factory for the aggressive growth of Terpios. Shading hypothetically impairs the nutritional symbiont of the invasive species: the effect of sunlight on cyanobacterial biomass and its influence on Terpios progression over live coral patches was tested through in situ shading experiments. This study showed that artificial shading with cotton fabric could effectively mitigate sponge growth on live coral without affecting coral homeostasis.

The sponge holobiont in a changing ocean: from microbes to ecosystems

“…For example, the abundant cyanobacterial symbionts of the coral-killing sponge Terpios hoshinota [ 151 ] play a key role in enabling the Terpios holobiont to aggressively overgrow a wide range of coral species [ 152 , 153 ]. They not only provide cytotoxic secondary metabolites [ 154 ] but also photosynthates that enhance the physiological performance of the host [ 153 , 155 ]. Impairing the photosynthetic capacity of the symbionts through shading stops the growth of the sponge and prevents it overgrowing adjacent corals [ 153 ], demonstrating the importance of the symbionts in mediating these competitive interactions.…”

“…They not only provide cytotoxic secondary metabolites [ 154 ] but also photosynthates that enhance the physiological performance of the host [ 153 , 155 ]. Impairing the photosynthetic capacity of the symbionts through shading stops the growth of the sponge and prevents it overgrowing adjacent corals [ 153 ], demonstrating the importance of the symbionts in mediating these competitive interactions. Outbreaks of Terpios hoshinota have been implicated in causing widespread coral mortality [ 156 , 157 ].…”

First Report of the Coral-Killing Sponge Terpios hoshinota Rützler and Muzik, 1993 in Western Australia: A New Threat to Kimberley Coral Reefs?

“…To date, the reasons for T. hoshinota invasions are not well understood but studies continue to elucidate possible mechanisms. Some authors suggest more research on ecological interactions between the sponges, corals and their associated microbes is needed [3,44]; others have examined possible mitigation techniques such as experimental shading to reduce the nutritional outputs of the intercellular cyanobacteria [6]. Sponge dispersal mechanisms are critical [43] and data is accumulating on the impacts of local environmental conditions [45].…”

“…It is an aggressive space competitor, grows rapidly (1-2mm per day; [3]) and actively overgrows corals. Since it persists in the environment (25 years; [4]), and is difficult to remove from reefs [5], T. hoshinota is emerging as a major threat to benthic communities on coral reefs [6].…”

“…It has been reported from Micronesia and the Northern Mariana Islands, Taiwan, and Japan [7][8][9]; the Great Barrier Reef [10]; American Samoa, the Philippines, and the South China Sea [11]; Papua New Guinea [12]; and Indonesia [13][14][15][16]. It was first reported in the Indian Ocean in 2014 (the Maldives; [17]), and has since been recorded from Mauritius [18] and Palk Bay in India [6]. Terpios hoshinota has been associated with areas of high turbidity and degraded reefs [7], but also occurs in relatively pristine and low turbidity environments, including Lizard Island, Great Barrier Reef [10] and the Ryukyu Islands, Japan [9].…”