PERIPHYTON-BASED RESTORATION SUCCESS CRITERIA March 26, 1996
Team members are as follows: Joan Browder, NOAA/NMFS; Pat Gleason, Camp Dresser & McKee; Jim Grimshaw, SFWMD; Paul McCormick, SFWMD; Jack Meeder, Florida International University; Laurie Richardson, Florida International University; Barry Rosen, SFWMD; Dave Swift, SFWMD; Al Steinman, SFWMD. Two meetings were held, recent projects concerning periphyton were discussed, and various potential indicators were evaluated.
Periphyton is influenced by both water quality and hydrologic conditions (i.e., hydroperiod and water depth). The relationship with water quality is reciprocal because periphyton strongly influences water quality through oxygen production, carbon dioxide uptake, calcite precipitation, and coprecipitation of phosphorus, the key nutrient involved in eutrophication in the Everglades. Periphyton is an important base of the food chain, and the food quality of periphyton, which is determined by composition of the major algal groups (i.e., the relative biovolume of diatoms, green, and bluegreen algae), likely influences aquatic secondary production and the flow of energy to higher consumers.
Periphyton taxonomic composition is influenced by water quality (both nutrients and minerals) and demonstrates a rapid response. The proportion of major algal groups in periphyton is influenced by hydroperiod. Percent biovolume as bluegreens increases with decreasing hydroperiod (Browder et al. 1981), whereas percent biovolume as diatoms and greens increases with increasing hydroperiod.
Periphyton-based indices would be useful throughout the Everglades to test the effectiveness of management actions to restore natural hydroperiods or reduce phosphorus loads. Specific areas where periphyton-based indicators should be used are as follows:
|Taylor Slough: To test the effect of Canal 111 operation changes in Experiment 7.|
|C-111 Area: To test the effect of Experiment 7 operation changes on the C-111 area. (Some of the flow that has been going to the C-111 area will be pumped into Taylor Slough).|
|Central Shark Slough: To test for effect of possible increases in nutrient loading with increased discharges.|
|Northeast Shark Slough: To test for effect of possible increases in nutrient loading due to restoration of flow from upstream (through WCA2B, which may receive water from backpumping and from Canal 67N).|
|WCA1: To examine the effect of altering the minimum regulation level from 11 ft to 14 ft. To determine whether canal water is entering interior wetlands, which presently are isolated from the hard, nutrient rich water discharged into the WCA1 canals.|
|WCA2A: To examine the effect of EAA discharge through the S 10 structure into WCA2A.|
|WCA3A: To examine the effect of increased routing of Lake Okeechobee regulation releases to WCA3A.|
|WCA3B: To examine effects of opening a gap in L67N between WCA3A and WCA3B, which allows canal water to enter WCA3B.|
|Lake Okeechobee: To examine the effect of water level fluctuations caused by changes in regulation stages and releases from the Lake to help meet water needs of the Everglades.|
Most of the periphyton in the Everglades is calcareous periphyton, however a desmid-rich periphyton that is low in calcite (i.e., < 10% of dry weight) currently is found in WCA 1 (the Loxahatchee Wildlife Refuge). Desmid rich periphyton may once have covered much of the northern and central Everglades before canals cut through the limestone substrate became a major water source. Separate success criteria were defined for the calcareous periphyton and desmid-rich periphyton.
Tentatively, the recommended target for calcareous periphyton is less than 50% bluegreen algae (measured in the same month each year because of seasonal differences. October is recommended because it provides the maximum length of time for a site to recover from the previous dry season and is too early for a new dry down. This criterion will be useful for monitoring the effectiveness of management actions that are directed at restoring predrainage hydroperiods. It should be applied to the Northeast Shark Slough and Taylor Slough areas. The scoring system for this criterion is as follows:
If X <= 50 then I = X/50 If X > 50 then I=1
where X is the combined percentage biovolume of diatoms and green algae in periphyton and I is the site score, a number between 0 and 1.
The site score is calculated for each site on a transect, then an average is calculated for the transect. The score for each area is the average score for all transects in the area. It is important to maintain the same sampling sites over the years, because addition or deletion of a site would affect the average.
The recommended target is based on a qualitative examination of data in Browder et al. (1981) and Trexler (1995). Browder et al. (1981) found combined proportions of green algae and diatoms ranging from 3% to 64% at 17 southern Everglades sites, including some in Taylor Slough.
Taylor Slough already had been affected by drainage canals in South Dade County at the time of the Browder et al. (1981) study. Based on accessory pigment content, Trexler et al. (1995) estimated that periphyton in central and southern Shark Slough consistently consisted of greater than 40% diatoms during recent sampling. The recommended target is tentative and may need adjustment when more data are available. This will require recalculation of the scores.
S. hoffmannii is not found at TP > 13 ppb (P. McCormick, pers. obs.). M. smithii is a year-round indicator of oligotroprophic conditions (P. McCormick, pers. comm., Raschke, 1993). The presence of these species indicates oligotrophic conditions. Their absence indicates eutrophic conditions. Use of the two species as an index will be useful for monitoring water quality (nutrient enrichment) effects in all of the sites listed in the above (Rationale) section, with the exception of interior WCA 1. One or more transects oriented with progressive distance from the point of discharge should be established in each areas. An appropriate transect already exists in WCA 2A and is currently being sampled by SFWMD and FDEP. The score at each sampling site is 0 if either S. hoffmannii and M. smithii are absent and 1 if both are present. The location score should be computed as the average of the site scores. [Editor's Note (February 1997): The work that was the basis of P. McCormick's observations is described in two recent publications: McCormick and O'Dell (1996a) and McCormick et al. (1996b).]
Diatom species are sensitive indicators of water quality and are used throughout the world for biological assessment. Swift and Nicholas (1987) prepared lists of diatom species characteristic of various water quality conditions in the Everglades. The recommended target is no more than 10% as cells of high nutrient species, based on expert judgment. The index would be a value from 0 to 1, calculated as follows:
If X >= 1, then I = (11 - X/.1)/10 If X < 1, then I = 1
This criterion will be useful for monitoring water quality effects in all listed areas, including Taylor Slough and Northeast Shark Slough, where water quality may change with the increased discharges planned to restore hydroperiods. There presently is no quantitative basis for this specific target as this parameter has not previously been quantified. Therefore, it may be modified as further information becomes available.
Both Gleason and Spackman (1974) and Swift and Nicholas (1987) found that desmids were a prominent component of the periphyton found in the low pH interior areas of WCA 1.
Desmids are not a part of the microflora of high nutrient areas of the Everglades (P. McCormick, pers. obs.). In WCA 1, sampling sites should be located to correspond to previous sampling sites of Gleason and Spackman (1974) and Swift and Nicholas (1987) and one or both of these studies should provide the baseline. Transects should be established that include the previous sampling sites and extend from the western perimeter canal to the eastern perimeter canal. Additional sampling sites should be established at regular intervals along these transects. The site score for this criterion is 1 when desmids are present and 0 when they are not. The objective should be to at least maintain desmids at the sites where they were present in the previous studies.
The characteristic species were listed by Swift and Nicholas (1987) and restated in Browder et al. (1994). The recommended target is 90%, but the target should be adjusted by using the values for two sites on the downstream end of the transect for which the proportion does not change between sites, if such exists. For WCA 2A, data that recently has been collected by SFWMD and FDEP should be used as the baseline. The ongoing work of P. McCormick and others will provide data for use in calculating scores. Calculations should be as follows:
If X < 90 then I = X/90 If X > = 90 then I = 1
where X = proportion of cells of the characteristic species and I is the site score. The score for this criterion should be the average of all the site scores except the two sites between which values do not change (if such as this exists).
Although quantitative data on this topic are missing, observations suggest that widespread coverage by calcareous periphyton is indicative of an oligotrophic system. This criterion should be measured on a large scale using remote sensing. The recommended target is 50%. The area examined should include the transects in each area. Existing class)fied imagery prepared at the University of Florida as part of the GAP program probably can be used for making the baseline calculation. This criterion should be applied to all sampling sites except interior WCA 1.
Raw data for calculating all scores should be retained because targets may be revised as more information is accumulated in association with the monitoring.
Coprecipitation of phosphorus with calcium carbonate has been demonstrated elsewhere and concentrations of Ca-bound P are correlated with distance from a P input in the Everglades Qualls and Richardson (1995), rates and the influences of variable factors have not been quantified. This information has great relevance to the ecological implications of periphyton monitoring results.
Because of the luxury uptake of phosphorus by algal cells and the possible coprecipitation of phosphorus with calcite, the phosphorus per unit area in algal biomass may provide a better representation of the phosphorus in the environment than is provided by water column concentrations. Phosphorus per unit area greater than a determined maximum might provide a warning that eutrophic conditions are becoming established at a site even before increases can be observed in the water column. Computation of this parameter would entail measurement of periphyton dry weight per unit area and ash free to dry weight ratios. This parameter might provide a useful success criteria if a maximum threshold for a healthy Everglades system could be determined through analyses of monitoring data.
These ratios would compliment the periphyton success measures and provide greater information about the system.
It is found in highest concentrations in oligotrophic waters and in lowest concentrations where the amount of available phosphorus is high.
This parameter should be explored for its usefulness in reflecting response to changes in water management. Past information (separated into organic and total ash components only) is available for southern Everglades periphyton from Browder et al. (1981) and Wood and Maynard (1974) and for WCA1 periphyton from Gleason and Spackman (1974). Previous comparison of the Wood and Maynard data to Browder et al. data (Browder et al. 1994) indicated much higher biomasses in both Shark Slough and Taylor Slough in the earlier study.
This parameter would be useful to follow in a monitoring program, although previous studies indicate that controlling influences are complex (Gleason and Spackman 1974, Browder et al. 1994). A better understanding of the environmental factors influencing this parameter would expanding the knowledge gained from monitoring periphyton.
It may be possible to distinguish the benthic mat from the floating mat using spectral information. The ratio of blue to red reflectance peaks might be useful in this context, because the red peak of chlorophyll a is attenuated by water more than the blue peak (Richardson, in press). On the other hand, if floating periphyton is more senescent, as suggested by Vzmazal and Richardson (1995), other aspects of the spectral signature of floating and benthic mats may be very different.
According to Paul McCormick (pers. comm.), one could simultaneously monitor effects of nutrient enrichment and changes in mineral content (e.g., calcium and chloride) using discrimination function techniques. McCormick is currently applying DFA to data from WCA 2A.
Monitoring to support success criteria should be established first in the areas where management changes are already taking place. Data for computing the indices should be collected at sites located along a series of transects in each area. The transects should be perpendicular to the main pathway of water flow in the area monitored and downstream from water inflow points. Periphyton monitoring should be conducted in conjunction with water quality monitoring and monitoring of fish and aquatic invertebrates.
A transect already is established in WCA 2, and monitoring and analysis are currently ongoing by SFWMD and the Florida Department of Environmental Protection. Comparisons of results along the transect will reveal the effect of reductions in loading rates due to institution of best management practices in the EAA. The Taylor Slough and C-111 areas and WCA 1 are the next sites needing monitoring. Northeast Shark Slough and WCA 3B should be the next areas where transects are established. Following are area-specific suggestions regarding transects.
Taylor Slough: Four east-west transects spaced several miles apart, from north to south, are already part of the monitoring plan for the Experimental Program. We recommend a fifth transect placed immediately north of the mangrove ecotone and extended west to Flamingo Road in Everglades National Park. At least seven sampling sites should be spaced at regular intervals along each transect with a spacing that ensures sampling the complete length of the transect and placement of the fourth site in the center of the slough.
Northeast Shark Slough: Three east-west transects should be established in Northeast Shark Slough, spaced about 5 km apart from north to south, beginning about 1 kilometer south of the Tamiami Trail. At least seven sampling sites should be spaced as regular intervals along each transect, as recommended above.
WCA 1: Transects should be established from the perimeter to the interior and incorporate the study sites of Gleason and Spackman (1974) and Swift and Nicholas (1987).
WCA 2A: An established transect exists in WCA 2A in relation to distance from the S10 structure, a source of water and nutrients from the EAA.
WCA 3A: Several north-south transects should be established to detect variation along the distance gradient in relation to inflow of water released from the EAA or the STAB.
WCA 3B: Transects already exist in WCA 3B in relation to the inflow points through the L67 levee. Periphyton should be added as a parameter to monitor along these transects.
A study of phosphorus cycling, including storages and sinks, in periphyton-rich environments of the Everglades should be conducted in conjunction with periphyton monitoring. The study should examine inorganic and organic forms of phosphorus and their transformations. Information should be obtained on a unit area basis and in relation to periphyton biomass and the calcite component of periphyton. The study should include determinations of periphyton biomass, both organic and inorganic, and should also determine the concentration of alkaline phosphatase. This study should obtain all of the information listed (A through G) in the above Supporting Information section. The approach and methods of Steinman and Louda in Lake Okeechobee and those of Qualls and Richardson (1995) in WCA 2A would provide a starting point for designing this study.
The importance of periphyton in the aquatic food web and relative values of the major algal groups are other topics needing study to confirm and expand beyond previous limited work.
Discriminant function analysis (DFA) should be applied to the species data obtained from monitoring the recommended transects. Useful comparisons can be made with the DFA results obtained by McCormick (pers. comm.). This not only will help interpret monitoring results but could lead to the development of DFA-based success criteria regarding water quality with respect to nutrients, alkalinity, and salinity.
Several techniques are available for monitoring periphyton to obtain success measures. Microscopy is the established technique for obtaining species identifications, cell counts, shapes, and measurements for determining presence or absence of indicator species, relative abundance, and proportions, by taxa (Swift and Nicholas 1987, Browder et al. 1981). This methodology can provide information for Success Criteria A through E above. Accessory pigment analysis using HPLC and scanning spectrophotometry has recently been applied to Everglades periphyton for estimating the proportions of major algal groups, degree of senescence, and other information (Trexler et al. 1995). This approach might be applicable to Success Criteria A above. Accessory pigment analysis can help build a basis for obtaining a large-scale view of periphyton using remote sensing. It may be possible, through remote sensing, to map the areal coverage of periphyton mats (Success Criteria F above) using current sensors and techniques. New techniques based on spectral radiometers and new hyperspectral remote sensing imagers might allow mapping of periphyton by proportions of major algal groups (Success Criter A above). The new hyperspectral remote sensing imagers, because of their many narrow spectral band widths, provide a resolution that may make it possible to distinguish many algal pigments (Richardson, in press). A pilot study would be required to adapt and test this new methodology to the Everglades.
Because there has been so little work with Everglades periphyton and much of it is current, a brief review of recent and ongoing work follows. Three institutions currently are involved in periphyton research relevant to the development of success criteria: SFWMD, Florida International University, and the Duke Wetland Research Center.
SFWMD is conducting both monitoring and experimental studies concerning periphyton. The focus is on determining the effect of nutrient enrichment. Paul McCormick is cooperating with FDEP in sampling periphyton along the established transect in WCA2A downstream from the S-10 structure, where agricultural drainage water is released into WCA2A. Taxonomic composition is being quantified in terms of species and number. In addition, McCormick has been conducting a nutrient dosing study in WCA 2 using semi-permeable enclosures. He recently has initiated a periphyton dosing study in WCA 1. He also is studying the periphyton in the Everglades Nutrient Removal site (ENR).
Jim Grimshaw and David Swift of SFWMD collaborated on further analysis of Dave's 1980s data on periphyton in WCA2A and WCA3A, much of which was published in Swift (1984) and Swift and Nicholas (1987). A major emphasis of Grimshaw et al. (1993) is phosphorus content of periphyton. Grimshaw recently has completed a study on the effect of shading by macrophytes on photosynthesis in the algal mat in WCA2A. Grimshaw has initiated a new study concerning the floating periphyton mat in WCA 2A.
Al Steinman of SFWMD is working with William Louda at FIU on periphyton in Lake Okeechobee. They are studying phosphorus cycling in the microalgae (phytoplankton, epiphyton, and epipelon) of the Lake littoral zone. They are measuring content, uptake, and release of inorganic and organic forms of phosphorus using radioisotope techniques.
Laurie Richardson and Joel Trexler of Florida International University conducting field experiments in Shark Slough of Everglades National Park to determine the effect of Hurricane Andrew-like events on periphyton and the aquatic animal community. Richardson is characterizing periphyton in terms of a suite of accessory pigments and is also measuring biovolume in order to determine the relationship of the pigment signature, determined by scanning spectrophotometry after separation with HPLC (high performance liquid chromatography), to the proportion of major algal groups.
Periphyton is a component of ongoing studies by Jack Meeder and Mike Ross in the C-111 area and the C3 1E area. They have several north-south transects extending from southern Joe Bay toward the C-111 canal. They are measuring periphyton biomass and identifying the species of diatoms at sites along the transect and looking for effects of sea level rise and freshwater inflow changes. Work in the C31E area relates to a planned project to restore sheet flow to the coastal area east of the canal.
Trophic studies pertaining to periphyton are planned in the experimental flumes being established at FIU/Southeast Environmental Research Program (SERP) as part of nutrient dosing studies soon to be initiated.
The Duke Wetlands Research Center has ongoing research in WCA 2A with a periphyton component.
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