I first learned about photogrammetry in 2015 while a masters student at the University of the Virgin Islands. While designing my first experiment, I realized I had an issue. I wanted to study competition and growth of Caribbean reef corals and sponges, but these animals are so amorphously shaped that it was difficult to accurately measure how much surface area of one is covered by another. While looking for solutions, I found a study that used photogrammetry to make 3D models of living corals. I had always assumed that 3D modeling required extravagant hardware and expertise, and so was excited to learn about how structure-from-motion photogrammetry could be used to model almost anything – even parts of a living coral reef – using only a camera.
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I received a small grant to purchase Agisoft MetaShape (back when it was called PhotoScan), and was able to use photogrammetry for my masters research experiment (Olinger et al. In Press). For this, we attached combinations of sponges and algae to corals, in order to simulate competition among the three groups. We then measured how fast each competitor (sponge or algae) overgrew the corals using photogrammetry. The results of this experiment were quite interesting: we found that some sponges overgrew corals much faster when the sponge was also in contact with algae. On Caribbean coral reefs, corals are continuing to decline, while algae and sponges grow like weeds and are more abundant than ever. Our findings have some important implications for reefs where both algae and sponges are proliferating, as this could mean even faster loss of corals.
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In 2018, I joined Dr. Joseph Pawlik’s lab at the University of North Carolina Wilmington, where my focus has shifted more towards sponges. Sponges, animals belonging to the phylum Porifera, are poorly understood and less popular research subjects compared to corals and other reef organisms. Sponge research is on the rise, however, because of growing awareness of the important ecological role that sponges play, and also because this group is more and more abundant in the Caribbean, especially on degraded reefs where the space once occupied by corals is now vacant. The field of sponge ecology – much like photogrammetry – is in its heyday, and I am fortunate to be able to bridge these two disciplines.
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I use photogrammetric techniques as part of my doctoral research to gather some basic but essential information about sponges, including the growth rates for 16 common Caribbean species (Olinger et al. 2019). This important information has alluded scientists, in large part because of the numerous sponge species and morphologies, and absence of fossil records and annual growth indicators. The diversity of sponge shapes alone have made it very difficult to measure sponge volume, especially for the more structurally complex, branching species. Traditionally, the fastest way to do this has been to collect whole specimens and measure how much water they displace. This requires a lot of work, and more importantly, kills anything that is collected. With photogrammetry, we can circumvent this destructive process entirely and take more accurate measurements for many more individuals and over many time points.
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Along with easier measurements of sponge size come better estimates of sponge growth. Basic demographic parameters such as growth rate are important, for example if we want to predict how fast sponges may colonize following a coral die-off. We used photogrammetry to measure the volumes of sponges growing on a shipwreck, where we knew (from the date of sinking) their maximum age. This creative approach allowed us to rapidly estimate growth rates for an unprecedented 16 species of Caribbean sponges and make interesting new comparisons across species.
Copied from the "women on Sketchfab" blog series (link)
last updated summer 2019