Periphyton Taxonomy. Periphyton community composition was classified by Xx. Xxxxx Xxxxxxxx (Laboratory of Phytoplankton Ecology, Biological Centre of the Academy of Sciences of the Czech Republic). Each sample was examined to determine dominant species by biovolume. Relative dominance within the two major groups (diatoms and cyanobacteria) was also calculated separately. The results presented in this report focus on presence/absence comparisons at the genus level within three common classes of periphyton: blue-green algae, diatoms and green algae. Community comparisons were made between water depth treatments across two dates selected to represent conditions at the end of the first deep water phase (9/16/2014) and the conditions following a period of recovery after a return to shallow conditions (1/15/2015) in the variable depth treatments. Samples from the static depth treatments were also examined for comparison to the variable-depth treatments. The above comparisons (across dates and across depth treatments) were made using periphyton collected from the midpoint of each process train, as this location showed the greatest differences in water TP concentration between depth treatments. Another taxonomic comparison was made using samples from the 9/16/2014 event, whereby midpoint samples were compared to outflow-region periphyton samples. A final comparison looked at the taxa present in mesocosm samples, as well as periphyton collected from the PSTA Cell and un-enriched areas of the natural everglades marshes in WCA2A and WCA3A.
Periphyton Taxonomy. Periphyton communities vary across the Everglades landscape, and have been previously reviewed by Xxxxxxx, Xxxxxxx and Xxxxx (1994) and more recently by Xxxxxx et al. (2011) and Xxxxxxxxx et al. (2011). In an STA setting, less is known about the species composition of periphyton. This is especially difficult to determine during short-term mesocosm studies, as diatom and bluegreen algae communities continue to mature over several months to years (Vymazal 2003). Thus, the long-term operation of the STA-3/4 PSTA Cell provides a unique opportunity to understand the periphyton community as it evolves in a constructed system. The effects of removing muck soils as an internal nutrient source may include the development of specific periphyton communities in the PSTA Cell, relative to other muck-based systems. Based on previous work with Everglades periphyton, low-P communities are dominated by diatoms and blue green algae, with P-sensitive species such as Cymbella minuta and Mastogloia smithii present (See table 3-2 in XxXxxxxxx et al., 2000). Assessment techniques using periphyton are not standardized, but artificial substrates allow for direct comparisons between different locations, or over time. A drawback to artificial substrates is that the periphyton communities are not fully represented on these substrates during short-term deployments. For this reason, periphyton samples in Porta-PSTA systems were collected from the mesocosm walls (CH2M-Hill 2003). However, there is still valuable insight to be gained by examining the diatom communities and other taxa that colonize uniform substrates (such as glass slides), during a known period of development. A combination of artificial substrates and grab samples of natural substrates is required to gain a complete representation of the communities present in the PSTA Cell. Community characteristics (species composition and relative biovolume) were determined for the PSTA Cell on several occasions to provide a basis for comparison with communities that develop in mesocosm-scale experiments, and with natural communities in low-P areas of the WCAs.
