Sediment Profile Imaging (SPI) Overview
Without a doubt, one of the camera's most powerful attributes is its ability to convey ecological information in a format that most people can understand quite easily:SPI technology has been used extensively throughout the United States for the past 20 years to monitor the environmental impacts of dredged material disposal, characterize sediment quality, and look for pollution "hot spots". This optical coring device works like an upside-down periscope and takes cross-sectional images of the upper 20 cm of the seafloor. As one of the developers of the technology, I had the privilege of introducing it to the government of Hong Kong in 1993, and it became a key component of the 4-year, territory-wide monitoring program associated with the massive dredging/land reclamation that was a key part of the new Chep Lap Kok airport construction. We have also introduced the technology in many areas outside the United States (Canada, Ireland, Italy, New Zealand, China, Azerbaijan); SPI is a powerful "technology hook" that can provide an innovative and cost-effective solution to many marine environmental monitoring programs.
a picture.
SPI allows rapid data acquisition during field sampling (the camera is literally "pogo-sticked" across the seafloor). A wide variety of physical and biological parameters can be measured from each image, including:
Grain-size major mode and range (gravel, sand, silt, clay)
- Small scale surface boundary roughness
- Evidence of erosional or depositional environments, allowing identification of high and low kinetic energy areas
- Subsurface ane gas pockets (evidence of high Sediment Oxygen Demand)
- Depth of the apparent RPD (Redox Potential Discontinuity)
- Calculation of the Organism-Sediment Index, allowing rapid identification and mapping of disturbance gradients in surveyed areas
- Presence of epifauna
- Surface microbial aggregations
- Infaunal Successional Stage
- Evidence of excess organic loading and high sediment oxygen demand
Benefits of using Sediment Profile Imaging technology includes:
Parsimonious design of the most efficient sampling station strategy for future surveys; because traditional seafloor sampling techniques are expensive and time-consuming, SPI can be an enormous aid in determining the location of traditional sampling stations. By rapidly characterizing the variation in benthic sedimentary and community conditions, limited sampling resources can be allocated to the optimum sampling locations to accurately characterize the variance that exists in a particular area. All too often the results of monitoring programs show that a particular parameter of interest has either been over- or under-sampled as a result of "flying blind" initially and then sticking religiously with the initial station locations that were chosen arbitrarily from a nautical chart.Rapid and cost effective data collection and analysis; Not only can large areas of bottom be surveyed quickly and efficiently, but for many monitoring objectives, SPI technology can provide the necessary answers without the need to collect grab samples or repeatedly enumerate and identify individual invertebrates and assemble long species lists each time a sampling study is performed.
Gradient delineation between sampling locations accurately; Because of the camera's ability to obtain pictures rapidly and efficiently, it can supplement traditional sampling methods by "filling in the gaps" between traditional chemical and biological sampling locations. The camera can accurately delineate gradients in biological community type, organic loading, or sediment grain-size between fixed station locations.
Over the past 10 years, I have come to realize that the technology's most powerful asset is this last item; in several environmental litigation cases concerning ocean disposal impacts where unsubstantiated claims were made about environmental damage, SPI was able to provide the decisive evidence that impacts were transitory and a full ecosystem recovery had taken place.
