Biology, Ecology

Net uptake rates of soluble reactive phosphate (SRP) of Ceratophyllum demersum and the dense periphyton mat associated with the macrophyte were calculated by measuring the disappearance of stable phosphorus (30, 50, 100, or 200 μg P/L) from the water column over a one-hour period each month for one year. Two seasonal periods were established based on average photosynthetically active radiation (PAR) and length of daylight through the year. ANOVA showed that the uptake rates were significantly affected (P < 0.05) by the amount of SRP added and were greater during the period of increased irradiance. Uptake rates continued to increase, even at spike concentrations equal to 10,000 μg P/L, indicating that maximum uptake was not achieved and that this plant complex is able to sequester even greater amounts of SRP. Estimates of the yearly uptake capabilities of the plant complex for a 525 ha wetland for the 30, 50, 100, 200 μg P/L spike treatments were 27, 55, 103, and 182 kg P/yr, respectively.

Biomass, net production, turnover, and decomposition of the seagrass Halophila johnsonii were studied in the Lake Worth Lagoon, Palm Beach County, Florida, USA. Biomass and apical meristem density averaged 8.0 g dry wt/m^2 and 1122/m^2, respectively. Mean net productivity was 0.00154 g dry wt/shoot/day or 0.45cm/shoot/day with one new leaf pair for every 0.97 cm of shoot growth. Estimated turnover time was 4.6 days. Mean weight loss in plant material was 72% after three days and 88% after seven days. No evidence was found of sexual reproduction. Halophila johnsonii's growth dynamics in the intertidal and shallow subtidal zones are characterized by low biomass, substantial apical meristem density, regular leaf pair production, rapid turnover, and rapid decomposition. Halophila johnsonii's growth in these zones provides an additional level of biomass and detritus to the shallow lagoon system.

A recent surge in the consumption of shrimps has compelled the aquaculture industry to expand greatly. Bacteriosis poses a major challenge to shrimp cultivation. Probiotic control of disease in larvicultures has been on the rise for the past decade; however, there has been little research to provide required frameworks for this promising technology. In this study, the normal gut flora of the commercially important shrimp, Penaeus vannamei, and its relative, P. duorarum was extensively analyzed to provide a basis for selection of putative probiotic strains. Heterotorphic members of the gut and ambient water were isolated and characterized by culture techniques, microscopy, Biolog biochemical fingerprinting, whole cell crude protein fingerprinting, and 16S rDNA sequence analysis. Non-pathogenic Vibrio harveyi-like strains were prevalent in the gut of both penaied shrimps, regardless of age and source. Community level physiological profiling by principal component analysis showed the gut community was fairly stable throughout shrimp life stages.

This study is to further understand the effects of fire on the invasive Asian grass, Neyraudia reynaudiana in the south Florida pine rocklands, at Larry and Penny Thompson Park in Miami-Dade County. Urban surroundings, fire suppression, and Hurricane Andrew in 1992 required prescribed fire in the pine rocklands to prevent wildfires and succession into hardwood habitat. Neyraudia reynaudiana's rapid spread caused concern due to its resistance to herbicide. A main concern was that fire, which is a natural component of the pine rockland community, could enhance Neyraudia reynaudiana's spread. This study observed and measured Neyraudia reynaudiana regrowth in two plant communities at five times over one year after one treatment of prescribed fire. Two herbaceous plant inventories were taken one year apart. The study's results show that Neyraudia reynaudiana was enhanced by fire.