The Impacts of Predation and Habitat Degradation on Coral Reef Sponge Assemblages in SE Sulawesi, Indonesia

• Main Author: Powell, Abigail
• Other Authors: Bell, James, Smith, David
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Victoria University of Wellington 2013
• Subjects: Sponge; Ecology; Coral reef; Pacific; Ocean acidification
• Online Access: http://researcharchive.vuw.ac.nz/handle/10063/2726

Coral reefs across the globe are in decline due to multiple threats including overexploitation, pollution, coastal development, climate change and ocean acidification. Much research has focused on the effects of these threats on hard corals while their impacts on other important benthic invertebrate groups have been overlooked. Sponges are a diverse and abundant component of coral reef communities in the Indo-Pacific that play important functional roles on reefs including nutrient cycling, linking primary and secondary production, reef bioerosion and spatial competition. Consequently, changes in the abundance and distribution patterns of sponges can affect overall reef ecosystem function. Understanding the factors that control sponge distribution patterns is therefore essential for the successful prediction and mitigation of the effects of current threats to reef systems. Sponge distributions are known to be affected by a number of abiotic factors such as wave action, sedimentation and water flow, but the role of biological factors such as predation and competition is less clear. The primary aim of my thesis was to determine the effects of predation on the distribution and abundance of sponge assemblages in the Wakatobi Marine National Park (WMNP), SE Sulawesi, Indonesia. My first objective (chapter 2) was to identify the major spongivores in the Wakatobi using surveys and behavioural observations of key invertebrate (nudibranchs and starfish) and vertebrate taxa (fish). I then adopted a statistical modelling approach (chapter 3) to examine associations between sponges and a suite of abiotic and biological factors, including spongivore abundance, across nine sites in the WMNP. The results of this analysis showed that although sponge assemblage composition was weakly associated with spongivore abundance, sedimentation is more likely to have a greater impact on sponge abundance and distribution patterns. I found that degraded sites were characterized by low diversity sponge assemblages dominated by a single ...