Effects of water temperature and pH on growth and metabolite biosynthesis of coral reef sponges

Abstract

Warmer, more acidic water resulting from increased emissions of greenhouse gases will impact coral reef organisms, but the effects remain unknown for many dominant groups such as sponges. To test for possible effects, adult sponges of 6 common Caribbean coral reef speciesAiolochroia crassa, Aplysina cauliformis, Aplysina fistularis, Ectyoplasia ferox, Iotrochota birotulata and Smenospongia conulosa -were grown for 24 d in seawater ranging from values experienced at present-day summer-maxima (temperature = 28°C; pH = 8.1) to those predicted for the year 2100 (temperature = 31°C; pH = 7.8). For each species, growth and survival were similar among temperature and pH levels. Sponge attachment rates, which are important for reef consolidation, were similar between pH values for all species, and highest at 31°C for E. ferox, I. birotulata and A. cauliformis. Secondary metabolites, responsible for deterring predation and fouling, were examined for A. crassa, A. cauliformis, E. ferox and I. birotulata, with 1 to 3 major metabolites quantified from each species. Final metabolite concentrations varied significantly among treatments only for zooanemonin from E. ferox and N-tele-methylhistamine from I. birotulata, but these concentrations were similar to those found in wild conspecifics. Considering adult sponges only, these findings suggest that the ecological roles and physiological processes of the 6 coral reef species will be little affected by the mean values of water temperature and pH predicted for the end of the century. KEY WORDS: Sponges · Water temperature · pH · Climate change · Growth · Metabolite biosynthesis Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 462: [67][68][69][70][71][72][73][74][75][76][77] 2012 els negatively affect coral reef sponges, these ecological processes and community interactions could be impacted.The combined effects of warmer and more acidic waters on marine sponges are largely unknown. Millions of years ago, mass extinctions of calcifying sponges occurred during periods of ocean acidification and global warming (Kiessling & Simpson 2011). However, most coral reef sponges today are not calcifying species; instead they have a skeleton composed of silica spicules and/or spongin fibers (i.e. demosponges), so the effects today may differ from those of archaic times. Numerous studies have also found a relationship between water temperature and sponge growth and survival. Seasonal patterns of water temperature, for example, are positively correlated with sponge growth for some tropical species (e.g. McMurray et al. 2008, Leong & Pawlik 2010, Duckworth & Wolff 2011. In contrast, high water temperatures can exclude coral reef sponges from neighboring habitats (Pawlik et al. 2007), disrupt their symbiotic relationship with microbes, causing death (Webster et al. 2008), and promote disease outbreaks that decimate sponge populations (Smith 1941). The pH level can also influence sponge abundances, with low pH seawater caused by sulphur...

Effects of pCO2 on the interaction between an excavating sponge, Cliona varians, and a hermatypic coral, Porites furcata

“…In a similar species, Cliona celata, attachment to bivalve shells was slower in reduced pH treatments, and survival slightly depressed (Duckworth and Peterson 2012); however, this study lowered pH using hydrochloric acid, not by injecting CO 2 . It is possible that the reduced pH might have had a negative physiological effect on the sponges themselves, although there was no observed sponge mortality in this study, and others have reported limited impacts of pCO 2 on sponge physiology (Duckworth et al 2012;Wisshak et al 2012;Fang et al 2013). Despite no significant differences in attachment rates among treatments, sponge bioerosion was significantly increased in the high pCO 2 treatments.…”

“…Target pH values for this system were 8.0 (ambient pCO 2 ), 7.8 (moderate pCO 2 ) and 7.6 (high pCO 2 ). In each reservoir, pH was monitored continuously using a pH controller (reef Fanatic) connected to a CO 2 regulator (Milwaukee Ma957); whenever pH levels exceeded the target values of 7.8 and 7.6 for the moderate and high pCO 2 treatments, respectively (anthony et al 2008;Duckworth et al 2012), the controller opened a valve that delivered CO 2 gas to the reservoir until target values were achieved again. no direct CO 2 manipulations occurred in the ambient pCO 2 reservoir.…”

“…response variables Survival was monitored weekly for both P. furcata and C. varians individuals. To understand whether the competitive interaction between C. varians and P. furcata was affected by pCO 2 , C. varians attachment to corals was assessed weekly for each coral-sponge pair by visually inspecting and gently prodding the sponge explant (Duckworth et al 2012). Calcification was quantified using the percent change in skeletal weight of individual corals, obtained from the initial and final buoyant weights (Jokiel et al 1978;Davies 1989) and hereafter referred to as percent net calcification.…”

“…While few studies have considered the influence of pCO 2 on the competitive outcomes of interactions between corals and other reef organisms, our study suggests that assessing the impacts therefore, directly impact the net growth, stabilization and carbonate accretion processes on reefs. Increasing pCO 2 also intensifies the rate of erosional processes by physically and chemically weakening existing CaCO 3 structures (Kleypas 1999), thereby facilitating the biologically mediated erosion of carbonate substrates (Tribollet et al 2009;Duckworth and Peterson 2012;Wisshak et al 2012;Fang et al 2013;reyes-nivia et al 2013). …”

“…Members of the 'Cliona viridis species complex' are known to be particularly efficient bioeroders, as this group of sponges harbor symbiotic zooxanthellae that both accelerate boring rates and necessitate direct spatial competition with corals for light (Hill 1996). Studies demonstrating that erosional processes are affected by decreasing pH (Duckworth and Peterson 2012) and increasing pCO 2 (Wisshak et al 2012;Fang et al 2013, Wisshak et al 2014) are important for understanding how future changes will affect substrate erosion; however, a direct evaluation of the spatial interactions and competitive outcomes occurring between these ecologically important species must also be undertaken.…”