467 30 Indicators of Ecosystem Integrity for Estuaries Stephen J. Jordan and Lisa M. Smith CONTENTS Introduction 467 Terminology and Definitions 468 Conceptual Models 469 Examples of Indicators 471 Water and Sediment Quality Indicators 471 Single-Species (Population-Level) Indicators 472 Community Indicators 472 Ecosystem Indicators 473 Discussion 475 Conclusions 478 Acknowledgments 478 References 478 Introduction Why do we need indicators of ecosystem integrity for estuaries, what are they, and how would one or more of these indicators inform and contribute to management of these diverse, complex systems? The importance of estuaries was expressed nicely by Welsh (1984, p. xiii): “Estuaries … are one of the most heavily utilized and most productive zones in our planet. Their integrative processes … weave a web of complexity far out of proportion to their occupation of less than 1% of the planet’s surface.” Citizens groups, environmental managers, and elected officials want to know the status of estuarine ecosystems, locally, regionally, nationally, and globally. Especially where there have been large public investments in pollution controls and other preventive and restorative measures, people want to know if their money has been well spent (Jordan and Vaas, 2000). Thus, there is a clear need for indicators that will provide comprehensive answers to these questions at appropriate intervals. Murawski (2000, p. 655) recom- mended “ simple, robust indices of ecosystem state that gauge … production, diversity, and variability,” and emphasized that indicators should have the capacity to predict the results of management. Although Murawski was writing in the context of fisheries and fisheries management, these principles apply more broadly to the integrity of ecosystems in general. The problem, then, is to formulate indicators that are simple in presentation and interpretation. They should be robust (i.e., not sensitive to small perturbations or irrelevant factors) and predictive, but also grounded in the complexity and variability that are essential properties of the ecosystem. In terms of time and effort, organization of data, and realism in representing the system, such indicators are intermediate between simple descriptive statistics and complex, process-oriented mathematical models. In this chapter we offer several relevant concepts and a few examples of indicators of the large-scale structure and behavior of estuarine ecosystems. We also outline principles for development and appli- cation of indicators. 2822_book.fm Page 467 Friday, November 12, 2004 3:21 PM © 2005 by CRC Press 468 Estuarine Indicators Terminology and Definitions Indicators can be constructed at various scales of organization, from single chemical, biochemical, or physiological measurements to highly integrated composites of system attributes (Figure 30.1). This chapter is concerned principally with the integrative, value-oriented indicators located in the lower right quadrant of Figure 30.1. Indicators at molecular, sub-organismal, organismal, population, and community levels of organization can be informative for various purposes, but indicators at the whole-ecosystem level are essential for managing ecosystems and answering the public’s most basic questions. The terms “integrity” and “health” have been used widely to designate desirable states of ecosystems. The goal of the U.S. Clean Water Act is to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters” (U.S. Code 33:26:1251a), but the act does not attempt to define integrity. Without further definition, neither health nor integrity is a useful or measurable descriptor of an ecosystem. A dictionary (Davies, 1976, p. 370) defines integrity as “soundness; completeness; unity” and health as “the state of an organism with respect to functioning, disease, and abnormality at any given time … optimal functioning with freedom from disease and abnormality. … flourishing condition; vitality.” Extending these definitions to an ecological context, integrity might imply that the structural properties (state variables) of a system exhibit an expected, undisturbed condition; health might be used to indicate how well the system is functioning (rate variables) with respect to expec- tations. Karr et al., (1987) defined biological integrity as “the ability to support and maintain … a balanced, integrated, adaptive community of organisms having a species composition, diversity, and functional organization comparable to that of natural habitat of the region.” This definition is prob- lematic for estuaries given their complexity, open boundaries, and almost universal lack of “natural habitat.” “Condition” is a more general, less value-laden term used in some publications (e.g., U.S. EPA, 2001; Vølstad et al., 2003) in reference to the status of ecosystems. Condition, along with the first definition of health (“the state of an organism … at any given time”), implies a continuum, whereas the other definitions — along with the definition of integrity — are categorical: one is healthy or not; one has integrity or does not. Each of these words can have inappropriate connotations for nonspecialists. Integrity has moral implications. Health can be consciously or subconsciously associ- ated with diseases and toxicity. Condition may suggest negative status unless modified with positive adjectives (good condition, excellent condition). One of the problems with terminology is the attempt to express several properties in a single word. Chesapeake Bay Program (CBP, 1987) policy-makers wrote, “the entire system must be balanced, healthy, and productive.” This statement contains more information than the individual terms discussed above, and reaches the center of what we are trying to express with ecosystem indicators. “Balanced,” FIGURE 30.1 A hierarchy of indicators. 2822_book.fm Page 468 Friday, November 12, 2004 3:21 PM © 2005 by CRC Press Indicators of Ecosystem Integrity for Estuaries 469 “healthy,” and “productive” were specifically defined in the context of the Chesapeake restoration in a later report (Table 30.1). The phrase “the entire system” is also important, suggesting a need for indicators that apply simultaneously and comprehensively to the whole system in all its vastness and complexity. Apparently, it is a relatively new idea to capture the essence of large, complex ecosystems in a single indicator or small set of indicators. Only in recent years have monitoring programs begun to generate the necessary data, and then only for a select, few systems. We should expect that less ambiguous terminology will arise, but for now, health, integrity, and condition are used as mostly interchangeable descriptors of what we are attempting to quantify with these indicators. In this chapter, we use the term integrity, more for consistency with recent literature than by preference. Conceptual Models Conceptual models are fundamental to indicator development (Boyle et al., 2001). Conceptual models of ecosystems can have many forms, ranging from minutely detailed flow diagrams based on energy or materials, to highly aggregated box models, to qualitative descriptions of expectations or values. Typi- cally, conceptual models portray ecosystems as arrangements of interacting parts (molecules, species, trophic guilds, landscape, or seascape mosaics). These concepts lead naturally to indicators based on a suite of interactions, or relationships between inputs and outputs. There is an alternative route to stressors through intricate pathways, it is possible to integrate system responses into an indicator of ecosystem integrity. Relationships of magnitude and variation between stressors and the indicator, and its component responses can be used to make causal inferences and form testable hypotheses, if those are our concerns. A useful type of conceptual model considers the ecosystem as a unitary whole that responds predictably system components interact, but how best to represent the system as a whole. That is, what indicator or set of indicators accurately tracks changes in the integrity of the ecosystem? How does one quantify the response axis of Figure 30.3 and Figure 30.4? The response variable, an indicator of ecosystem integrity, should answer important, comprehensive questions about ecosystems: What is the status of the ecosystem with respect to one or more reference points? What is the current direction of change? How will the ecosystem change in response to external forces, especially management actions? How long will it take to reach a desired or stipulated level of integrity? TABLE 30.1 Definitions of the Terms Balanced, Healthy, and Productive, as They Apply to Estuarine Ecosystems Balanced “Having sufficient populations of prey species to support the species at the top of the food chain, and to limit overabundance at the bottom of the food chain; no major function of the ecosystem dominates the others” Healthy “Having diverse populations that fluctuate within acceptable bounds; free from serious impacts of toxic contaminants, parasites, and pathogens; having sufficient habitat to support a diversity of species” Productive “Providing sufficient production of harvestable products to serve human needs without depleting predator and grazer populations to the point where internal, functional balance is disrupted” Source: CBP (1993). 2822_book.fm Page 469 Friday, November 12, 2004 3:21 PM © 2005 by CRC Press indicators, as portrayed in the upper oval in Figure 30.2. Rather than tracing the effects of multiple to stress (Figure 30.3) and changes over time (Figure 30.4). In this conceptual mode, we ask not how 470 Estuarine Indicators FIGURE 30.2 The contrast between process-oriented models and holistic ecosystem analysis. Indicators of ecosystem integrity are derived from integrated system responses as depicted in the upper part of the diagram. (The flow diagram at the bottom was adapted, with permission, from an ecosystem model developed by Dan Campbell.) FIGURE 30.3 Conceptual model of the relationship between ecosystem integrity and stress on the ecosystem. On a relative scale, health is the complement of impairment. 2822_book.fm Page 470 Friday, November 12, 2004 3:21 PM © 2005 by CRC Press Indicators of Ecosystem Integrity for Estuaries 471 Examples of Indicators The following examples of indicators begin with physical and chemical measurements, and then proceed organization. At each level, we discuss some of the merits and concerns associated with the indicators. Water and Sediment Quality Indicators Water quality is the most traditional indicator of estuarine condition. The ecological and aesthetic problems associated with anoxia, turbidity, eutrophication, and bacterial pollution are obvious even to nonscientists (dead fish, brown water, excessive algal growth, human illnesses). Even though these problems have been recognized in some estuaries for many decades, the development of water quality criteria, standards, and pollutant load capacities specific to estuaries is in its infancy. The implications of using a suite of water quality indicators for the ecological integrity of estuaries is not always clear. The U.S. Environmental Protection Agency (U.S. EPA) Environmental Monitoring and Assessment Program (EMAP) developed indicators of water quality based on dissolved oxygen, chlorophyll a , nutrient concentrations, and water clarity to assess eutrophication. Although EMAP is designed to make ecological assessments over large spatial and temporal scales, the data are used to determine condition for geographic regions rather than ecosystems. Water quality measurements cannot stand alone as indicators of the integrity of an entire ecosystem, because they merely “brush the surface” of biological integrity and ecosystem value. We note that EMAP also samples fish and benthic communities, and employs indicators of biological community structure and health in its assessments. As with water quality, indicators of sediment quality offer only a piece of the puzzle. Many sediment contaminants are persistent and may be associated with degraded benthic communities, but no criteria for contaminants in estuarine sediments have been established, only guidelines (Long and Morgan, 1990). Contaminants interact with sediment constituents in ways that can greatly affect their biological avail- ability; thus, sediment concentrations may not be directly correlated with toxicity and biological effects (Bayne et al., 1985). Recent sediment research in estuaries has focused not on contaminants, but on organic constituents (e.g., pollen and diatom frustules) in benthic cores as paleological records of ecosystem responses to anthropogenic stressors (Bianchi et al., 2000; Dell’Anno et al., 2002). The National Coastal Condition Report (U.S. EPA, 2001) combined indicators of water quality, sediment quality, fish tissue contaminants, wetland loss, and benthic communities into a single index to determine the overall condition of the nation’s estuaries. This method improved multi-indicator integra- tion, but its lack of a strong biological basis limited its interpretation with respect to ecosystem integrity. FIGURE 30.4 Integrity of a stressed ecosystem in the time domain (see also Cairns et al., 1992). (From Jordan, S. J. and P. A. Vaas. 2000. Environmental Science and Policy 3:S59–S88. With permission.) 2822_book.fm Page 471 Friday, November 12, 2004 3:21 PM © 2005 by CRC Press according to the hierarchy depicted in Figure 30.1, ending with an example at the ecosystem-level of 472 Estuarine Indicators Nevertheless, the application of this index at regional and national scales was an improvement in integrated assessments. Single-Species (Population-Level) Indicators Abundance or life history traits (recruitment, growth, mortality) of widely distributed, abundant species, or perhaps less abundant, environmentally sensitive species, could be candidates for indicators of ecosystem health. This idea is particularly attractive when the species is well known to the public, for example, popular sport fishes or important commercial species. Bortone (2003) discussed the potential of spotted seatrout ( Cynoscion nebulosus ) as an indicator species for southeastern estuaries. Because of their popularity and depleted status, striped bass ( Morone saxatilis ) and Eastern oysters ( Crassostrea virginica ) became de facto , although scientifically unreliable, indicators of the health of Chesapeake Bay. Striped bass recruitment in the Chesapeake displayed a long-term pattern of increase, followed by a be explained by changes in fisheries and fishery management, but the pattern was also curiously similar manager once asserted that the striped bass population was the only indicator needed to track the Chesapeake restoration — if the fish recovered, the system would recover. Subsequently, the striped bass population recovered within a decade after stringent fishery management controls were initiated, but the ecosystem remained in many ways far from its desired state. For example, the extent of hypoxic and anoxic water did not decline; seagrass coverage, although increasing, was far less than stipulated by restoration goals; and the long-term decline of oyster populations continued (CBP, 2003). These few of many possible examples of single-species indicators illustrate two points. First, recovery of a “flagship” species can be encouraging, but nevertheless may occur within a system that is far out of balance or far from its desired state. Second, fisheries and fishery management are integral components of estuarine ecosystems; they should not be seen as apart from or irrelevant to concerns about water quality, habitat conditions, and diversity. Community Indicators Community-level analysis may be indicative of environmental change caused by single or multiple stressors, and predictive of consequences at the ecosystem level. According to Attrill and Depledge (1997), community-level investigations are ecologically relevant because changes in communities can be extrapolated to the health of the ecosystem through changes in food web structure. Seagrasses (submerged aquatic vegetation [SAV]) and benthic macrofauna are the most prevalent community-based FIGURE 30.5 Maryland index of juvenile striped bass relative abundance 1954–1995. (From Maryland DNR, 2003.) 2822_book.fm Page 472 Friday, November 12, 2004 3:21 PM © 2005 by CRC Press precipitous decline, followed by dramatic recovery (Figure 30.5). This entire dynamic ultimately could to the conceptual model of ecosystem stimulation, decline, and recovery shown in Figure 30.4. A senior Indicators of Ecosystem Integrity for Estuaries 473 indicators of estuarine ecosystem health. Long-term changes in seagrass coverage in several estuaries have been strongly associated with nutrient loading and its indirect effects on the availability of light to the plants. This light limitation may result in shifts from SAV-dominated production to proliferation of phytoplankton and macroalgae (McClelland and Valiela, 1998). Long-term losses and gains in seagrasses rank highly as indicators of eutrophication, but also have some drawbacks as comprehensive indicators of ecosystem integrity. They are vulnerable to physical disturbances (boating, dredging, and commercial fishing operations), diseases, major storms, and other climatic extremes; thus, interpretation of their distribution and abundance can be ambiguous. Infaunal macrobenthic communities have been attractive as indicators largely because of their lack of mobility. This trait makes them reliable indicators of exposure, and susceptible to stressors such as toxic contaminants and severe hypoxia. The structure of these communities, however, is sensitive to factors not directly related to ecosystem integrity such as sediment grain size and organic content. The patchiness of benthic communities over very small spatial scales also can be a drawback in assessing ecosystem integrity over large areas. Ranking and categorical reduction of the data (methods for generalizing almost any indicator) have been applied to minimize the problem of patchiness at any scale (U.S. EPA, 2001). Indicators based on fish communities or assemblages have received less attention than seagrasses or benthos. The impracticality of complete sampling of estuarine fish communities, along with the migratory behavior of many species are universal difficulties. There have been several attempts to develop estuarine indices of biotic integrity (IBI; Karr et al., 1987) analogous to those used in freshwater systems. Examples can be found in Hughes et al. (2002) and Jordan et al. (1991). Although IBI approaches are feasible, IBIs for estuarine systems tend to be specific to particular habitats, showing less spatial generality and sensitivity to multiple stressors than might be desired. Vaas and Jordan (1990) used long-term data from seine surveys in the Maryland portion of Chesapeake Bay (Maryland DNR, 2003) to indicate changes in ecosystem integrity. They portrayed graphically 3- year means of relative abundance at intervals of decades. A simple model based on management goals ings shown in Figure 30.6, developed by Vaas and Jordan (1990) from life history information and cluster analysis of the seine data, showed an interesting and by now familiar pattern when further synthesized Community indicators are generally more robust than single-species indicators, because they integrate responses over broader sectors of the ecosystem and a wider range of environmental influences. Fish community indicators, for example, would be less sensitive to a single fishery management decision than the single-species indicators described above. Ecosystem Indicators Indicators at the ecosystem level of organization integrate data over biotic communities and trophic levels, and may include abiotic components (e.g., measures of water quality and physical habitat). Indices such as mean trophic level, system-level trophic transfer efficiency, capacity, ascendancy, and overhead have been used to characterize and compare estuarine ecosystems (e.g., Baird and Ulanowicz, 1989). These types of indices are based on flows of materials (usually carbon) or energy within and through the system. A stressed ecosystem, for example, might exhibit lower values for mean trophic level, transfer efficiency, and ascendancy, along with higher overhead, than an unstressed system. In simpler terms, a stressed system would be less organized and less efficient, while dissipating energy and materials more rapidly (relative to their supply) than an unstressed system. Such indices are valuable tools for gaining understanding about the status and relative functions of ecosystems. Their principal weakness is that they are mathematical abstractions. Multivariate analysis of ecosystem attributes has been used to organize environmental data. The spatial relationships of these attributes can then be used to develop a relative indication of ecosystem integrity. Jordan and Vaas (2000) used cluster analysis of 12 metrics (selected by screening many 2822_book.fm Page 473 Friday, November 12, 2004 3:21 PM © 2005 by CRC Press candidate metrics) in developing an index of ecosystem integrity for Chesapeake Bay tributaries (Table and covariation among species predicted future community structure (Figure 30.6). The tolerance group- for this chapter (Figure 30.7). 474 Estuarine Indicators ranging from phytoplankton and SAV to fish. The index included four water quality metrics in addition by the Chesapeake Bay Program, so that both societal and ecological values were represented. The final index was constructed by ranking six clusters of observations (spanning 9 years and 40 to 50 proportions of land cover: urban land predicted low ecosystem integrity, and forested land predicted high ecosystem integrity. The index was further collapsed into three nominal categories of ecosystem integrity by calculating the mean cluster value for each site over 9 years, and assigning “good,” “fair,” and “poor” designations to the each third of the distribution of means. This procedure produced a FIGURE 30.6 Observed and predicted changes in relative abundance of 19 species of fish from Maryland Chesapeake Bay seine surveys. Data in the top four bar graphs are 3-year averages. Note the apparent disruption of the community in the two middle graphs, and the predicted partial recovery in 2000. (Adapted from Vaas and Jordan, 1990.) 2822_book.fm Page 474 Friday, November 12, 2004 3:21 PM © 2005 by CRC Press 30.2). The analysis included a broad array of metrics representing communities and trophic levels to the biotic variables. Six of the metrics were normalized to restoration goals previously established sites) into an ordinal scale of ecosystem integrity (Figure 30.8). The index was sensitive to watershed simple display of long-term, large-scale geographic patterns (Figure 30.9). Indicators of Ecosystem Integrity for Estuaries 475 Discussion Ecosystem integrity is a human construct that defies rigorous scientific definition. To assess the integrity of an ecosystem requires reference points defined by humans, who lack perfect knowledge of the system’s structure and functions. Because we cannot determine from first principles “what is a good or bad ecosystem,” we ask reasonable people what they want from the system. For Chesapeake Bay, the desired FIGURE 30.7 Mean rank abundance of tolerant species in Maryland Chesapeake Bay seine surveys, 1960–2000. Lower values indicate higher abundance of tolerant species and lower ecosystem integrity. TABLE 30.2 Metrics Used to Construct an Index of Ecosystem Integrity for Chesapeake Bay Metric Ref. Submersed Aquatic Vegetation Success Percentage of potential habitat vegetated (+) Batiuk et al., 1992 Deviations from Water Quality Goals Dissolved inorganic nitrogen (NO 2 + NO 3 + NH 4 ) (–) Batiuk et al., 1992 Dissolved inorganic phosphorus (–) Batiuk et al., 1992 Secchi depth (+) Batiuk et al., 1992 Chlorophyll a (–) Batiuk et al., 1992 Plankton Biomass of nuisance algal species (cyanophytes and dinoflagellates) (–) Jordan and Vaas, 2000 Ratio of mesozooplankton to microzooplankton abundance (+) Buchanan et al., 1993 Biomass of microzooplankton (–) Buchanan et al., 1993 Fish Trophic index (+) Jordan and Vaas, 2000 Number of fish species in bottom trawl (+) Carmichael et al., 1992 Benthos Benthic Restoration Goal Index (+) Ranasinghe et al., 1993 Dissolved Oxygen Percentage of observations < 1 mg/L in bottom waters or < 5 mg/L in above pycnocline waters (–) Waters-Jordan et al., 1992 Note: Plus (+) and minus (–) signs indicate positive or negative relationship to ecosystem integrity. Source: Adapted from Jordan and Vaas (2000). 2822_book.fm Page 475 Friday, November 12, 2004 3:21 PM © 2005 by CRC Press 476 Estuarine Indicators states are health, balance, and productivity (CBP, 1987), as defined in the introduction to this chapter. A more recent document (CBP, 2000) explicitly acknowledged the human and conceptual elements in calling for “a shared vision — a system with abundant, diverse populations of living resources,” and reiterated the need for the entire system to be healthy and productive. The examples of indicators presented here all reflect one or more elements of balance, health, or productivity. The striped bass index is a strong indicator of productivity, but tells little about health or balance. In fact, as the Chesapeake striped bass population recovered and became very abundant in the late 1990s and early 2000s, it became less healthy, displaying consistent, abnormally high prevalence of starvation and disease (Jacobs et al., 2002). Perhaps in addition to the obvious health implications, these problems were symptomatic of an unbalanced condition, with overproduction of an important predator. The Chesapeake Bay fish community indicators include elements of balance (species dominance), productivity (abundance), and, less directly, health (tolerance groups). They lack reference to values or reasoned expectations, however. Instead, they depend on an internal historical reference (the structure of the community ca. 1960). The pristine condition could not be used as a reference because it was FIGURE 30.8 higher ecosystem integrity. The year 1991 is shown as an example; the analysis spanned 1986–1994. (From Jordan, S. J. and P. A. Vaas. 2000. Environmental Science and Policy 3:S59–S88. With permission.) 2822_book.fm Page 476 Friday, November 12, 2004 3:21 PM © 2005 by CRC Press An index of ecosystem integrity based on cluster analysis of 12 metrics (Table 30.2). Higher values represent [...]... 65f 483 65g 65h 75 e 75 f 75 a 75 c 65f – Southern Pine Plains and Hills 75 d 65g – Dougherty/Marianna Plains 65h – Titon Upland/Tallahassee Hills 75 a – Gulf Coast Flatwoods 75 b – Southwestern Florida Flatwoods 75 b 75 c – Central Florida Ridges and Uplands 75 d – Eastern Florida Flatwoods 75 e – Okefenokee Swampls and Plains 75 f – Sea Island Flatwoods 76 a – Everglades 76 b 76 b – Big Cypress 76 c 76 c – Miami Ridge/Atomic... Page 478 Friday, November 12, 2004 3:21 PM 478 Estuarine Indicators strongly related to the potential for robust indicators and predictive models Taken together, Figure 30.5 through Figure 30 .7 illustrate the relationships between short-term interannual variability, which could only be interpreted as noise, and long-term patterns that contain useful information Conclusions • • • • • • Whole-system indicators. .. Environment 274 :213–253 Heemskerk, M., K Wilson, and M Pavao-Zuckerman 2003 Conceptual models as tools for communication across disciplines Conservation Ecology 7( 3):8 Available at http://www.consecol.org/vol7/iss3/art8 Lambeck, R J 19 97 Focal species: a multi-species umbrella for nature conservation Conservation Biology 11:849–856 Merriam-Webster’s Collegiate Dictionary, 10th ed 1994 Merriam-Webster,... Assessment Guidelines for Florida Inland Waters Florida Department of Environmental Protection Technical Report, Tallahassee, 150 pp McCarron, E and R Frydenborg 19 97 The Florida Bioassessment Program: an agent of change Human and Ecological Risk Assessment 3(6):9 67 977 © 2005 by CRC Press 2822_book.fm Page 492 Friday, November 12, 2004 3:21 PM 492 Estuarine Indicators Plafkin, J.L., M T Barbour, K D Porter,... Resources Publication EPA 60 0-3 -8 9-0 60 U.W EPA, Washington, D.C U.S Environmental Protection Agency 1994 Unpublished Florida Regionalization Project Technical Report, 84 pp U.S Environmental Protection Agency 1999 Rapid Bioassessment Protocols for Use in Wadable Streams and Rivers Publication EPA 841-B-9 9-0 02 U.S EPA, Washington, D.C Wolfe, S 2002 Personal communication Florida Department of Environmental... Peninsula Total taxa Ephemeroptera taxa Trichoptera taxa % Filterer Long-lived taxa Clinger taxa % Dominance % Tanytarsini Sensitive taxa % Very tolerant 16–42 0–3.5 0–6.5 1–42 0–3 0–9 54–10 0–26 0–11 78 –0 16–49 0–6 0 7 1–45 0–5 0–15.5 43–10 0–26 0–19 36–0 16–41 0–5 0 7 1–40 0–4 0–8 54–10 0–26 0–9 59–0 Source: Fore (2003) 100 Median 25 % -7 5% Non-Outlier Range Outliers 80 SCI 60 40 20 0 0.8 1.2 1.6 2.0 2.4 2.8... Included in this group are chapters focused primarily on such structurally-based indicators of estuarine health as microbes, benthic diatoms, parasites, macrobenthos, fishes, birds, dolphins, seagrasses, and mangroves Some of the ongoing research on estuarine indicators can be grouped into a category related to functional-level indicators and processes These studies focus on understanding the functional... conditions Floral- or faunal-based marine communities such as seagrass beds, coral reefs, mollusk/worm reefs, sponge beds, and octocoral beds are more characteristic of fairly transparent waters (e.g., greater than 3-m Secchi depth) Floral-based tidal marsh and tidal swamp communities are usually distributed in shallow, lower wave-energy areas Finally, the salinity regime is extremely important in estuarine. .. Management Partnership Proceedings of a Conference Chesapeake Research Consortium Publication 1 37 © 2005 by CRC Press 2822_book.fm Page 480 Friday, November 12, 2004 3:21 PM 480 Estuarine Indicators Vølstad, J H., N K Neerchal, N E Roth, and M T Southerland 2003 Combining biological indicators of watershed condition from multiple sampling programs — a case study from Maryland, USA Ecological Indicators. ..2822_book.fm Page 477 Friday, November 12, 2004 3:21 PM Indicators of Ecosystem Integrity for Estuaries 477 FIGURE 30.9 Long-term ecosystem integrity of northern Chesapeake Bay Mean cluster values (1–6; see Figure 30.8) for each site over 9 years (1986–1994) were collapsed . Indicators 471 Water and Sediment Quality Indicators 471 Single-Species (Population-Level) Indicators 472 Community Indicators 472 Ecosystem Indicators 473 Discussion 475 Conclusions 478 Acknowledgments. Sea Island Flatwoods 76 a – Everglades 76 b – Big Cypress 76 c – Miami Ridge/Atomic Coastal Strip 76 d – Southern Coast and Islands 65f 65g 65h 75 a 75 e 75 f 75 c 75 b 75 d 76 c 76 b 76 d Panhandle Peninsula Northeas t . Upland/Tallahassee Hills 75 a – Gulf Coast Flatwoods 75 b – Southwestern Florida Flatwoods 75 c – Central Florida Ridges and Uplands 75 d – Eastern Florida Flatwoods 75 e – Okefenokee Swampls and Plains 75 f – Sea