Reduced Diversity and High Sponge Abundance on a Sedimented Indo-Pacific Reef System: Implications for Future Changes in Environmental Quality

Abstract

Although coral reef health across the globe is declining as a result of anthropogenic impacts, relatively little is known of how environmental variability influences reef organisms other than corals and fish. Sponges are an important component of coral reef fauna that perform many important functional roles and changes in their abundance and diversity as a result of environmental change has the potential to affect overall reef ecosystem functioning. In this study, we examined patterns of sponge biodiversity and abundance across a range of environments to assess the potential key drivers of differences in benthic community structure. We found that sponge assemblages were significantly different across the study sites, but were dominated by one species Lamellodysidea herbacea (42% of all sponges patches recorded) and that the differential rate of sediment deposition was the most important variable driving differences in abundance patterns. Lamellodysidea herbacea abundance was positively associated with sedimentation rates, while total sponge abundance excluding Lamellodysidea herbacea was negatively associated with rates of sedimentation. Overall variation in sponge assemblage composition was correlated with a number of variables although each variable explained only a small amount of the overall variation. Although sponge abundance remained similar across environments, diversity was negatively affected by sedimentation, with the most sedimented sites being dominated by a single sponge species. Our study shows how some sponge species are able to tolerate high levels of sediment and that any transition of coral reefs to more sedimented states may result in a shift to a low diversity sponge dominated system, which is likely to have subsequent effects on ecosystem functioning.

Consumption of dissolved organic carbon by Caribbean reef sponges

“…This could provide a competitive advantage to seaweeds and sponges over corals, further reinforce coral depletion, and lead to reduced reef resilience (Pawlik et al ). The Indo‐Pacific, by contrast, is dominated by phototrophic species (e.g., Wilkinson ; Powell et al ) that are net primary producers whose nutrients are likely retained and cycled internally as opposed to expelled in the excurrent jet (Pawlik et al ). These reefs would be less susceptible to the feedback between sponges and seaweeds, and thus could exhibit higher overall resilience than those where sponge assemblages are dominated by heterotrophic species possessing the capacity to feed on dissolved organics (Pawlik et al ).…”

Spongivory in the Wakatobi Marine National Park, Southeast Sulawesi, Indonesia

“…Sites were lo cated on the fring ing reefs of Kaledupa and Hoga Islands (see Figure 1 ). These sites were selected as they en com pass a range of en vi ronmen tal and bi o log i cal con di tions (Powell et al 2014). It is im por tant to note that this study of spongivory was car ried out in a lo ca tion where fi sh as sem blages and po ten tial spongivore abun dances have likely been al tered by fi sh ing.…”

Demosponge diversity from North Sulawesi, with the description of six new species

“…A few other papers concerning sponge ecology, distribution and symbiosis (Bavestrello et al 2002, Bell and Smith 2004, Calcinai et al 2004, Cerrano et al 2006, de Voogd and Cleary 2008, de Voogd et al 2009, Powell et al 2014, Rossi et al 2015) have been published.…”