Nutrient Distribution Effects from Freshwater Discharge at Franklin Lock and Dam (S-79) in 2005 and 2006 on the Caloosahatchee Estuary and San Carlos Bay, Fort Myers, Florida

• Main Author: Uhlenbrock, Kristan M
• Format: Others
• Published: Scholar Commons 2009
• Subjects: Water flow; Karenia brevis; Water quality; River; Nitrate; American Studies; Arts and Humanities
• Online Access: https://scholarcommons.usf.edu/etd/60; https://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1059&context=etd

Nutrient distribution correlates with discharge of freshwater from Franklin Lock and Dam structure (S-79) by delivery into the Caloosahatchee Estuary (CE) and out of this area, including the surrounding San Carlos Bay (SCB) and adjacent West Florida Shelf. This study analyzed the temporal and spatial distribution of nutrients along the CE waterway and illustrates the effects high freshwater discharge from S-79 has on the coastal and offshore environments, providing a potential source of nutrient input. This study consisted of a 7-station transect monitored biweekly from April 2005 thru August 2006 for nutrients, dissolved oxygen, chlorophyll a, and salinity, along with the corresponding freshwater discharge from S-79. High flow rates correlated (r²=0.7488) with decreased salinity downstream from S-79. At high discharge, over 140 m³ s-¹, nutrients were noticeably transported downstream to SCB; during extreme high flow rates of 285 m³ s-¹, it takes a little less than 4 days for a particle of water to travel from S-79 to the mouth of the estuary. There is evidence from the SATlantic ISUS deployment that pulses of water from S-79 correlated with downstream increased concentrations of nitrate on a daily temporal scale. The assumption that upstream estuarine waters are potentially carrying nutrients downstream can only be conjectured for high flow rates. Low flow rates (less than approximately 28 m³ s-¹) corresponded to hypoxia during the summer months of 2006. The highest chlorophyll a concentrations were found either during decreased flow rates or summer months. Chl a (>3.0 µm) in SCB and the mouth of the CE was above 4 µg l-¹ in July through October 2005 and ranged from 1.24 to 9.62 µg l-¹ in June through August 2006. Karenia brevis blooms were also present during this time. Nutrient loading rates into SCB provided enough DIN and DON to support the maintenance of K. brevis. Therefore monitoring and studying the amount of nutrient loading into coastal and offshore water can elucidate their importance on the surrounding ecology.