Monday, May 12, 2008

Monitoring the Water Quality of Bermuda’s Coral Reefs and Seagrass Beds with NASA Satellites and UW Sensors:

Project context
When sand and mud get stirred up in the ocean by either ships or storms, it has a negative affect on the plants and animals that live there. The sand smother and grind into the surface of the plants and animals. Also when up in the water in thick clouds suspended sand blocks the light reaching the sea floor that the plants and animals need to grow or to see.

In order to know how the organisms living in the water and on the sea floor are being affected by the amount of sand and other material is suspended in the water, scientists usually go out in boats and measure water clarity and the amount of suspended sediments in sea water. These measures through time are similar to underwater weather reports and tell scientists how healthy the ocean is through time and from place to place.

However, new methods and instruments such as remote sensing using satellites, and aerial photography from air planes, have expanded the capacity for studying biological processes, as well as the effects of geophysical and chemical factors such as temperature and nutrient concentrations on natural environments.

Gerardo (front) checks the data uploading into
the laptop computer from an water particle sensor (see below)
that Dave (back) has suspended below the boat.

Gerardo Toro-Farmer, a graduate student at the Univesity of South California at Los Angeles is working with BREAM as well as collegues at USC-LA and NASA to develop different in-situ (in place) and remote-sensed (by satellite) light measurements. He hopes to develop a reliable, low cost, and low effort way to be able to measure water clarity and suspended particulate load across Bermuda’s harbours and out across the coral reef lagoon to the deep sea around us.

An underwater sensor which uses lasers to
count and measure the size of particles in the sea.

Objectives
Optical measurements will be compared between in-place instruments and data collected by satellites, to study the effects of sediment resuspension events on the water column optical properties on coral reefs and seagrass beds. In this research Gerardo will address two questions:

Question 1: Can in-situ optical measurements be utilized to estimate resuspension and movement of bottom sediments from navigation channels?
Question 2: Can remotely sensed data be used to identify and quantify resuspended sediment plumes that are produced by ships traveling across the Bermuda reef lagoon in shipping channels

Anticipated Results
Gerardo expects to find a simple relationship between suspended sediment load and remotely-sensed reflectance in the red and infrared channels of NASA satellite imagery.

Stereoscopic imagery from satellites should clearly reveal vessels and their wake. This information combined with satellite mapping of suspended sediments will likely provide valuable information on the contribution of ship traffic to resuspension and associated redistribution of sediments in the lagoon.

False color images created with loggers light intensity measurements will probably show a gradient from lower light level values closer to the channels during periods of high ships traffic, to higher values (higher light intensity) far from the channels and during low traffic periods. This gradient will be also observed with satellite images.

NASA's AQUA satellite, which is used to assess water quality in Bermuda
and around the globe from outer space.