Allan D. Cembella1 , Diego A. Ibarra2, John J. Cullen2, and Richard F. Davis2 1
Abstract
Recent advances in the development of in situ optical sensing technology and rapid diagnostic assays for plankton components provide new opportunities for autonomous environmental monitoring and assessment in coastal waters. Moored optical sensors can provide continuous measures of water properties for documenting long-term trends in water quality in the coastal zone, such as eutrophication, run-off of coloured dissolved organic matter (CDOM), changes in seston abundance, and environmental effects of aquaculture. Such real-time optical systems are also well suited for detecting transient plankton events, such as harmful algal blooms. In areas affected by seasonal blooms of harmful algae many countries have instituted plankton surveillance programs as an early warning of impending toxicity or fish mortalities. The objectives of the current case study were to validate the application of moored optical sensors in the water column for monitoring changes in seston abundance, coloured dissolved organic matter (CDOM) and phytoplankton signatures within and adjacent to a mussel aquaculture site in Ship Harbour, Nova Scotia, Canada, an estuarine fjord with significant tidal flux and where harmful algal events occur annually.
Passive optical sensing systems are a valuable tool for continuous monitoring of the optical properties associated with plankton blooms and seston quantity in the coastal zone because the principal data products, ocean colour and depth-resolved attenuation coefficient (Kd), are well defined measurements that can be compared between sites over many years. Particularly when combined with rapid diagnostic assays, such methods offer sophisticated monitoring of harmful algal blooms and other water quality parameters.