Parameters: In Vivo Chlorophyll
CENS, a NSF Science & Technology Center, is developing Embedded Networked Sensing Systems and applying this revolutionary technology to critical scientific and social applications. Like the Internet, these large-scale, distributed, systems, composed of smart sensors and actuators embedded in the physical world, will eventually infuse the entire world, but at a physical level instead of virtual.
A specific area in which CENS technology is being applied is the monitoring of harmful algal blooms (HABs). A variety of naturally-occurring and introduced microorganisms adversely impact marine ecosystems and uses of marine resources. They can affect human health, fisheries and even tourism. However, conditions under which HABs develop are not well understood, and methods for detecting microorganisms are too slow and complex for timely intervention. With the development of technology, sensor networks provide a method to monitor the microorganisms in real time and solve the problem. The goal of this project is to deploy large numbers of sensors and robots operating in a semi-autonomous but coordinated fashion in the marine environment (Figure 1). The system should be able to follow, identify and investigate the behavior of microorganisms in situ and in real time.
Figure 1: (center) Schematic of autonomous, coordinated network of mobile sensors. (upper left) Testing of wireless communication between nodes in tank testbed. (upper right) Autonomous, mobile node equipped with computer-controlled mobility, communicatio
We are studying the dynamics of blooms of the alga Aureococcus anophagefferens in the waters off Long Island, NY. Existing monitoring efforts are time-consuming and involve manual sampling and analysis. We are constructing a network of sensors and samplers, consisting of both stationary and mobile “nodes,” to allow for spatially- and temporally-rigorous monitoring and adaptive sampling. For example, changes in temperature or chlorophyll fluorescence can serve as triggers for sampling (Figure 2).
Figure 2: Concentration of Aureococcus anophagefferens (BT) and temperature with depth in a column testbed. Note the decrease in BT concentration (black profile) around the point of the thermocline (gray profile).
The stationary nodes consist of temperature and salinity sensors, Turner Designs Cyclops chlorophyll a fluorometers, and associated processors and communications equipment (Figure 3).
Figure 4: Mobile node equipped with wireless communication, computer-controlled mobility and navigation, sampling system, and Turner Designs Cyclops fluorometer.
The Turner Designs Cyclops chlorophyll fluorometer is an integral part of the network of sensors. As a proxy for photosynthetic biomass, chlorophyll measurement is one of the most biologically-significant parameters to measure in marine systems. Previous blooms of A. anophagefferens have shown chlorophyll a levels between 5 and 50 ìg/L, although higher values are possible. We chose to use the Turner Designs Cyclops fluorometer because of its flexible sensitivity ranges, low power requirements and small size.
Author: Carl Oberg
Institution: University of Southern California, Los Angeles, California, USA