2008 PILOT PROJECTS AWARDEES

Exploring the Role of Remote Forcing of WFS Algal Blooms with Satellite Imagery
Dr. Mariana Framinan

Abstract:

Blooms of the toxic dinoflagellate, Karenia brevis, are a recurrent problem along the central West Florida Shelf and occur nearly annually, with highest frequency on the inner shelf between Tampa Bay and Sanibel Island from August to March. Several mechanisms have been proposed to play a role in harmful algal bloom (HAB) development: coastal upwelling, local coastal runoff, submarine groundwater discharge, along-shelf advection, deposition of iron-rich Saharan dust and freshwater discharge from eastward dispersal of Mississippi River plume (MRP). However, to date, the mechanisms that drive the HAB still remain unclear.

Recent studies have invoked another mechanism for which nutrients exported from the northern Gulf of Mexico by the plume results in a subsurface accumulation that is subsequently transported onshore by upwelling circulation. However this same cross-shelf mechanism may also be responsible for the transport of allochthonous water brought to the Florida region by mesoscale features on the (left) edge of the Loop Current (LC). This process may be particularly important in the northeast shelf close to the De Soto Canyon.

The purpose of this study is to evaluate the role of the freshwater outflow from the MRP and mesoscale features from the LC on the WFS using satellite-derived products. We will focus on the physical processes prior to, and during HAB occurrence, rather than on detecting the red-tide bloom. The spatio-temporal variability of these two mechanisms will be addressed to investigate the following questions: How often does the MRP extend eastward? Where is the easternmost location of the frontal plume? How often does the MR water reach the southwestern shelf and the Florida Keys? When does the LC /shelf boundary show highest variability? How far onshore do these shelfbreak instabilities penetrate? How often?

The long-term goal of this research is to fully describe the environment where the red-tide blooms develop.

In this pilot project we will focus on the period 2004-2005 when persistent blooms with large spatial coverage were observed. The advantage of this remote sensing approach is that it provides the needed synoptic view of the Gulf of Mexico and allows us to properly identify source regions and export pathways. The proposed analysis of the role of the river plume and mesoscale features on the WFS will contribute to a better understanding of the driving mechanisms that result in harmful algal blooms. It is expected that this study will provide valuable information to improve forecasting capabilities, contributing to the development of an increasingly useful suite of decision support tools for ocean and human health management.

Circulation constraints on Karenia Brevis blooms on the West Florida Shelf
Dr. Josephina Olascoaga