Nutrient Limitation on Phytoplankton Growth in the Upper Barataria Basin,Louisiana: Microcosm Bioassays |
| |
| Authors: | Ling Ren Nancy N Rabalais R Eugene Turner Wendy Morrison Warren Mendenhall |
| |
| Institution: | (1) Louisiana Universities Marine Consortium, 8124, Highway 56, Chauvin, LA 70344, USA;(2) Dept of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, USA;(3) Patrick Center for Environmental Research, Academy of Natural Sciences, 1900 Ben Franklin Parkway, Philadelphia, PA 19103, USA |
| |
| Abstract: | The Davis Pond Diversion (DPD) was constructed to divert Mississippi River (MR) water into the Barataria Basin to reduce the
salinity in support of wetland restoration on the Louisiana coast. To assess the phytoplankton nutrient limitation in adjacent
water systems and potential impacts of DPD, 12 seasonal nutrient-phytoplankton bioassay experiments were conducted from October
2003 to July 2004 using the natural phytoplankton assemblages from freshwater and brackish-water lakes, Cataouatche and Salvador,
LA (USA), which receive Mississippi River water from the DPD, and from a nearby freshwater lake, Lac des Allemands, that does
not. Dissolved inorganic nitrogen (N), phosphorus (P), and silicate (Si) were added with different combinations at Redfield
ratios in 10-l microcosms. Nitrogen was found to be the sole or primary limiting nutrient in all 12 experiments. N and P colimitations
were found in seven of 12 experiments, but N was always the stronger limiting factor. P limitation was never observed to be
the sole limiting nutrient. The results showed that a low concentration of P and a relatively high concentration of N do not
necessarily indicate only P limitation in these lakes. Lake Cataouatche and Lake Salvador were dominated by centric diatoms,
and Anabaena spp. were detected at high levels, particularly in summer. Lac des Allemands was generally dominated by N-fixing Anabaena spp. and other cyanobacteria, and their biomass responded significantly to N addition but not to P addition, indicating that
nitrogen fixation in Lac des Allemands may be inhibited by other factors such as iron. Our bioassay results demonstrate that
whether a water body is N- or P-limited is the consequence of the nutrient status and not the salinity regime. The results
suggest that the addition of nutrient-rich waters via diversions of Mississippi River water into these lakes might increase
the frequency of algal blooms, including noxious and toxic freshwater cyanobacteria. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
