WATER COLOUR IN THE BELIZE COASTAL ZONE

WRIScS, Ambios Ltd.,

University of Plymouth & Plymouth Marine Laboratory - UK

Research Objective

To conduct research to investigate the practicality of remote-sensing-based methodology for low cost monitoring of water turbidity and algal blooms in the coastal zone. 

 

 

                                

 

The project is concerned with the development of low- spatial-resolution but high-frequency-access ocean colour information from the Ocean-Colour satellite programmes. The aim is to investigate the potential for the application of satellite data (eg SeaWiFS) to monitor sediment plumes and algal blooms within Belize’s coastal zone. Project tasks include the development of data-access systems and data processing algorithms for removal of the effects of seabed visibility in shallow waters. This is being investigated in collaboration with the University of Plymouth (UoP) and Plymouth Marine Laboratory (PML). Raleigh field teams are used to collect the data needed for ground-truthing. This program is laying the foundations for development of a cost-effective tool for use in water-quality monitoring programmes in Belize coastal waters.

Specific Program Tasks, 2001 programme

Development of low spatial resolution (1km), but high frequency satellite ocean colour information (primarily SeaWiFS) for the Belize coastal waters:

  • Field data collection on water-column and seabed optical properties over a six month period (March –September) in two coastal zone areas in northern and southern Belize.
  • Training courses on the application and basic interpretation of SeaWiFS imagery delivered to key marine resource managers in Belize during two training sessions (5 training days total).
  • Analysis and synthesis of in-situ optical data in relation to satellite imagery, to highlight/resolve problems due to the effects of seabed visibility in optically-shallow waters.

Field Data Collection Programme

During 2001 there were two data collection areas (north and south) each with around 20 - 25 sampling stations with depth range between 2 to 40 m. The shallower stations of less than 20 m involve both water and seabed sampling, while the deep sites only involve water sampling. Fifty-metre transects were established and mapped at each of the shallower stations.

At Cary Cay in the south, the stations lie along a W-E oriented transect running from Placentia to Gladden Entrance and running through Cary itself (transect ~25 miles). At Long Cay in the north, two transects cover the area between the drop-off and mainland shore, W-E oriented and with a N-S spacing of around 3 miles.

In-situ measurements included Secchi disk, Profiling Reflectance Radiometer (PRR, to collect information on light conditions in the water column) and sample collection for lab analysis for chlorophyll, phytoplankton, Total Suspended Solids (TSS), organic matter and Coloured Dissolved Organic Matter (CDOM). Seabed mapping was undertaken at many sites, using RoxAnn (an acoustic ground discrimination system).  Seabed SCUBA work included seabed photography, bed colour observation, quadrat observations of bottom sediments and flora/fauna, and bag-sample collection. Water sampling was weekly, lab analysis every three weeks and seabed sampling was per expedition per site. Lab samples were prepared in the lab at the CZMI and shipped courtesy of Fyffes Ltd to the UoP and PML for analysis.

Satellite Data Acquisition / Processing

Near-real time SeaWiFS satellite imagery was downloaded (courtesy of NASA) and to complement the fieldwork data.

SeaWiFS 'quick look' image of Belize processed to show chlorophyll concentrations

The 2001 SeaWiFS imagery (available over the WWW via the GDAAC archive) was downloaded and processed to level 2 (optical / biogeochemical products). This processing requires a UNIX/LINUX workstation with the SeaDAS software (available at no cost) and a sufficient amount of disk space to handle the large imagery (can be several hundred MB in size). UoP and PML have developed processing routines (that slot into the SeaDAS software) to improve the accuracy of coast definition in satellite imagery where there are high concentrations of suspended sediment.

UoP has the facilities to process this data, but the feasibility of processing the data in Belize (CZMI) was also investigated.

Visit the Plymouth University site to see more  SeaWiFS images

Output/deliverables

At the close of the WRIScS 2001 project the following two objectives were completed:

  • Research report on the feasibility of using satellite imagery for water colour monitoring in optically shallow waters. This report provides  the basis for using ocean colour satellite imagery for time-series monitoring of water quality at a series of optically shallow sites (2001 survey sites) in Belize coastal waters. (download report)
  • Provision of guidance for coastal resource managers regarding the future practicality and cost effectiveness of developing an ocean colour monitoring facility for routine water quality monitoring in Belize.

A longer-term deliverable was also defined, based on further research:

  • Use of ocean colour satellite imagery to monitor water quality optical properties everywhere within the Belizean coastal waters (ie spatially continuous data, enabling visual recognition of features such as plumes) .

exit document