Water column and sediment nitrogen and phosphorus distribution patterns in the Florida Keys, USA

摘要: Measurements of the distribution patterns nutrients (ammonium, nitrate, orthophosphate, total N and P) chlorophyll concentrations were conducted under an interdisciplinary program known as SEAKEYS, initiated because concern that anthropogenic may be impacting Florida coral reefs. Samples collected along transects extended from passes or canals to 0.5 km offshore outermost Seven either in Biscayne National Park (BNP) Key Largo (upper keys) Mile Bridge/Looe part lower areas, which have best present-day reef development; two middle keys off Long area minimal development where allow estuarine Bay water flow onto platform. Off upper keys, column chl a elevated near marinas (1 μM NO3, 1 μg/l a), but returned oligotrophic levels (e.g., ⩽ 0.25 μg/l; NO3 μM; NH4 0.10 μM) within shore. Phosphorus concentrations, however, often higher ⩾ 0.2 PO4). Sediment interstitial nutrient decreased inshore areas 100 50 offshore) comparable those some presumably pristine coastal carbonate sediments. bulk was nearshore steeply ( 60 μg-at N/gm sediment 20 sediment, respectively); P (⩽ 6 μg- at P/gm sediment) varied little exhibited reverse pattern. N:P ratios consistently (1–10 vs. 20–40 nearshore). Higher are attributed periodic upwelling shelf edge. In both than there less inshore-offshore decrease noted keys. also, did not differ. Water most similar measured Overall, present data do support contention accumulating loads land-derived via surface flow, does document moderately many developed areas. Most natural entering waters shore appear taken up by algal seagrass communities before they reach patch Further work is needed determine whether nutrient-enriched ground reefs, however these would expected cause enrichment sediments, observed.