Nyssa J Silbiger, Ph.D.
Quantitative Marine Ecologist
“For most of history, man has had to fight nature to survive; in this century he is beginning to realize that, in order to survive, he must protect it.” 
― Jacques-Yves Cousteau
RESEARCH
My data are acquired from intensive field sampling efforts as well as a diverse set of pre-existing sources; thus, I apply an array of quantitative techniques to data analysis. I often utilize multivariate statistics and model selection using a likelihood framework, and I am beginning to use hierarchical Bayesian modeling. I am always interested in learning new data analysis approaches.  
  

Quantitative Ecology

Management efforts to sustain coral reefs often focus on coral health and percent cover, but reef ecosystem resilience also depends on bioerosion rates and their response to local and global human stressors. A persistent challenge is to distinguish the effects of climate change from other forms of environmental variation, and to understand how environmental variation impacts accretion-erosion processes across different spatial scales. In this study, I used existing data from long-term monitoring efforts to test how accretion rates by secondary calcifiers, bioerosion rates by borers and grazers, and net change rates respond to natural environmental variability across a range of spatial scales in the Hawaiian Archipelago. This analysis highlights the significance of location and spatial scale in understanding reef dynamics and, further, the need to recognize both reef secondary accretion and bioerosion processes in order to predict net coral reef responses to future environmental changes.   

Coral Reef Accretion-Erosion Balance

Coral reefs, arguably one of the most diverse ecosystems in the world, are greatly important ecologically, culturally, and economically. Unfortunately, coral reefs are particularly vulnerable to ocean acidification, in addition to many other local and global stressors. I addressed, and continue to address, several questions focusing on coral reef response to ocean acidification: 1) how does rising ocean acidity and warming influence secondary calcification and reef dissolution, 2) how does ocean acidification and warming influence sponge biomineralization of an invasive Hawaiian sponge, and 3) how does ocean acidification influence reef accretion and erosion in the context of natural environmental variability?  

Ocean Acidification on Coral Reefs

Prior studies have individually examined primary calcification, secondary calcification, and erosion processes and found varying responses to climate stressors, challenging our ability to predict the net response of coral reefs to global climate change. This complexity warrants an integrative approach that examines the impact of climate stressors on synchronous measurements of accretion and erosion. Current methods are unable to individually and simultaneously quantify accretion and erosion rates on similar time scales. Thus, I developed a novel high resolution method that uses µCT technology to separate reef accretion and erosion from the same experimental substrate exposed to the same environmental variation for the same time period. This method has already been used at several sites throughout Hawaii and is currently being used by NOAA at sites throughout the Pacific.  

µCT as a monitoring tool

Temperate ecosystems along the California Current System (CCS) are simultaneously threatened by rapid ocean acidification, rising sea-surface temperatures, and recent increases in climate-driven hypoxic events. Ecosystems within the CCS region provide many ecological and economic benefits to local stake-holders, and global stressors are threatening the value of these ecosystem services. Short of greatly reducing carbon emissions globally, locally alleviating stress on coastal ecosystems is our best strategy for maintaining ecosystem function. My current research aims at testing the idea that intertidal seaweeds can act as an ecological buffer, because of its strong influence on local pH and oxygen variation.

Climate Change feedbacks in the CCS