Water quality biological assessment

A brown tide bloom of the pelagophyte Aureoumbra lagunensis caused significant impacts to north Indian River Lagoon (IRL) in 2012-2013, including seagrass die-offs, fish kills, and reduced growth and grazing of ecologically important bivalves. There is potential for another pelagophyte, Aureococcus anophagefferens, to expand into this system. Filtration rates (FR) of the pleated tunicate Styela plicata exposed to Aureoumbra lagunensis and Aureococcus anophagefferens were measured against exposure to a control alga (Tisochrysis lutea) in order to determine its potential use as a bioremediator against these harmful algal blooms (HABs). In addition, whether S. plicata might serve as a vector of HABs was studied by culturing fecal deposits. Short-term exposure to HABs significantly reduced FR, whereas long-term exposure indicates comparable cell removal compared to the control. Vector potential of S. plicata was inconclusive. Results warrant further research to determine whether S. plicata can acclimate or respond to HAB conditions over time.

Pigment-based chemotaxonomy uses relative amounts of photosynthetic pigments (biomarkers) within algae samples to determine the algal class composition of each sample. Chemotaxonomy has been applied successfully to phytoplankton communities, but its efficacy for periphyton has not yet been established. This study examined the ability of simultaneous linear equations (SLE), CHEMTAX, and the Bayesian Compositional Estimator (BCE) to determine algal class composition in Florida Everglades periphyton. The methods were applied to artificial datasets, mixed lab cultures of known composition, and Everglades periphyton samples for which microscopic biovolume data was available. All methods were able to return accurate sample compositions for artificial data and mixed lab cultures. Correlation between pigment methods and microscopic results for natural periphyton samples was poor. SLE and CHEMTAX returned similar results for all samples while BCE performed less well.

The tunicate Styela plicata (Ascidiacea) was investigated for its potential use in bioremediation of bacteria and microalgae blooms from estuarine waters. Salinity tolerances, filtration rate, substrate selection, and effects on digested bacteria and ichthyofaunal communities were examined. If acclimated slowly, Styela can be placed in salinities as low as 24 parts per thousand (ppt) before increased fatalities result. An immediate decrease in salinity from 32 ppt to 20 ppt was not detrimental at short term exposure (four days). One average-sized (~40g) Styela, exposed to 105 and 106 bacteria or microalgae mL-1, can filter as much as 4.7 L hr-1 and 3.3 L hr-1, respectively. Individual tunicate filtration rates varied from hour to hour, independent of organism size, indicating that filtration rates for this species would be better reported on a population basis rather than on an individual weight or size basis. Bacterial viability in tunicate feces was assessed by ATP analysis. Bacteria were found to be non-viable after passage through the tunicate digestive tract. Filtration of eggs or larvae of recreationally or commercially important fish is of concern. The smallest eggs (~0.6mm) reported in the Indian River Lagoon belong to Cynoscion nebulosus (spotted seatrout) and Bairdiella chrysoura (silver perch). Over the course of two hours, 72.5% of 0.5 mm glass beads (simulated fish eggs) were initially retained, but many were later expelled by the tunicates. For 1.0 mm beads, 49.4% were initially retained and for 2.0 mm beads, 43.5% were initially retained. Neither the size of the oral siphon nor the size of the overall animal was correlated to bead retention. Substrate selection was investigated using the tunicate Phallusia nigra.

Coral reefs worldwide are threatened by many environmental disturbances including harmful algal blooms (HABs) which have been increasing on Florida coasts over the past decade. Research has mainly focused on HAB identification, percent cover and other effects on the benthos but the relationship of HABs with upper trophic levels has received less attention. To study this relationship, a two-year investigation on a 10-m deep reef off of Hallandale Beach, was conducted. Stationary fish census coupled with benthic transect videos were conducted quarterly between April 2005-July 2007. A significant correlation between Lyngbya sp. blooms and alterations in fish assemblages was observed. Lyngbya had a negative interaction with fish species and abundance; additionally, HAB sample periods were significantly different from low algal abundance periods. Blooms of Dictyota sp. had no measurable relationship with the fish assemblage indicating HABs may have variable impacts on fishes depending on family, species and chemistry of the algae.