Evidence of Anthropogenic Nitrogen Enrichment of the Littoral Waters of East Central Florida

Abstract

Abstract Excessive human-derived nutrient availability has been implicated as a primary driver in the decline of the water quality and biota of coastal ecosystems. In 2003, seven sites along an urbanized section (∼100 km) of the Atlantic littoral coastline in east-central Florida were assessed for the bio-availability of the primary nutrients nitrogen and phosphorus. Ratios of dissolved inorganic nitrogen (DIN = nitrate + nitrite + ammonium) to soluble reactive phosphorus (SRP) in 74 beach water samples averaged 8:1, indicating strong water column nitrogen-limitation. DIN concentrations ranged from 0.69 to 8.11 µM with a grand mean of 2.10 µM, a value two-fold above the reported threshold value of ∼1 µM that saturates growth of Florida red tide, Karenia brevis and macroalgae species utilized in this study, such as Ulva lactuca. The majority (mean = 56%) of this DIN was in the form of ammonium, even during a peak upwelling event in June and August, suggesting the importance of anthropogenic land-based nitr...