Blog Post
by Ivano Aiello / Moss Landing Marine Laboratories

3D Scanning of Rocky Intertidal Ecosystems in the North Coast’s MPAs – Part 1: Spatial Imaging Technology

February 23, 2015

Location Location Location!

Before I started my current position at Moss Landing Marine Labs (MLML) I was a post-Doc at the University of California Santa Cruz (UCSC) with Professor Bob Garrison who introduced me to the local geological formations of the Monterey Bay region. While I was conducting my research along the wave-cut benches of West Cliff in Santa Cruz, I was intrigued by the variety and richness of the marine creatures covering the rocks. Before going to UCSC, I worked mainly on mountain outcrops in Europe, so observing this type of complexity of marine life on the rocks that I was studying was quite fascinating. 

Intertidal ecology on the rock
Intertidal ecology on the rock

Even to my untrained eye, it was clear that the organisms were spaced in such a way that they traced the lithologic features that I was studying . I could see how the sea urchins were growing preferentially in the cracks between the rocks and were aligned along the structural features that I was measuring with my geological compass. The limpets seemed to favor the hard siliceous beds rather than the softer mudstones and the sea anemones were growing in puddles of water locked by doughnut-shaped carbonate concretions, formed more than 6 millions of years!

 

The power of spatial imaging
One of my first long-term projects as MLML faculty was to develop a conventional way for ecologists to  quantitatively assess whether invertebrate ecology is correlated to rocky substrate type. However, one of the main problems was that traditional topographic and structural mapping techniques allowed only a small number of observations. They were also relatively low accuracy and did not take into account the large range of spatial scales over which intertidal ecological processes occurr. 

The TLS uses the "time of flight" of
the IR laser to measure distances

Due to recent advances in spatial imaging technology with the creation of instruments that are field friendly and powerful 3D data post-processing software, it is now possible to characterize rock surface characteristics with unprecedented resolution and accuracy. Using our Trimble VX terrestrial laser scanner (TLS), my graduate students and I have developed field and 3D data post-processing techniques, that  allow us to produce 3D models of the rocky intertidal at different scales relevant to ecological processes; it also allows us to test, for the very first time, the contribution of geological variation in shaping the structure of benthic marine communities. Our TLS  uses a DR 300+ pulsed laser distance unit that determines distances by precisely measuring the flight time (Delta T) of the transmitted light pulse. The distance unit generates many short laser pulses, which are transmitted through the telescope to the target. The pulses reflect off the target surface and return to the instrument where the unit determines the time difference between the transmitted pulses and the received pulses. The unit uses the time difference to calculate the distance to the target from the fore-sight which has been previously geo-located.

A) Georeferenced photomosaic
of survey area of the surveyed area.
B) Point cloud and shaded relief
model of the surveyed area

Our TLS surveys produce multi-scale geospatial models over spatial scales ranging between cm to hundreds of meters.  Due to  the TLS’s high resolution (0.01 m) and accuracy (<0.005m), along with repeated survey feasibility, we are able to collect thousands of high-resolution topographic data points. The surveyed rocky intertidal outcrops and the ecology of the intertidal organisms can be spatially linked either using geo-referenced digital photographs or by logging biodiversity data directly into the TLS’s computer.

In collaboration with Dr. Peter Raimondi (UCSC) and colleagues from other institutions, this state-of-the-art spatial imaging system and research techniques developed by my lab are being used as part of the baseline characterization of rocky intertidal ecosystems for MPA’s along the North Coast of California, 

Stay tuned for future blogs  which will include exciting findings from surveys performed during the summer of 2014 by Ashley Wheeler, one of my graduate students.

Cheers!
Ivano

 

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