Product Citations and Abstracts

Microcosms, consisting of estuarine sediment slurries, were examined for their utility as models for assessing effects to microbial community structure and function. Data were obtained over a two-week period to evaluate the reproducibility between individual microcosms and the variability between microcosm slurries and fresh sediment cores. Sulfate reduction rates in microcosm slurries did not differ significantly from rates for freshly collected sediment cores (p>=0.05). However, the measured rates were more variable in microcosm slurries (SE=± 0.03-0.25 nM/ml/h) than in freshly collected sediments (SE=± 0.01-0.12 nM/ml/h). Rates of dark CO2 fixation in the microcosm slurries declined but were consistent with rates in freshly collected sediments (6.51 and 9.29 nM/ml/h on day 3, respectively). Relative abundances (RAs) of 16S rRNA determined for six specific phylogenetic assemblages of sulfate-reducing bacteria (SRB) were reproducible among three microcosm replicates with Desulfovibrio spp.consistently in greatest abundance (RA= 8.61 ± 1.40, day 7). Total direct bacterial counts were not significantly different between freshly collected sediments and microcosm slurries (p>=0.05). The results indicated that microcosms were both reproducible and representative of the field, and could thus provide a potentially useful tool for studies of microbial community response to perturbation.

Kurtz, Janis C., Laura E. Jackson and William S. Fisher. 2001. Strategies for Evaluating Indicators Based on Guidelines from the Environmental Protection Agency's Office of Research and Development. EPA/600/J-01/444. Ecol. Indic. 1(1):49-60. (ERL,GB 1133).

The Environmental Protection Agency's Office of Research and Development (ORD) has prepared technical guidelines to evaluate the suitability of ecological indicators for monitoring programs. The guidelines were adopted by ORD to provide a consistent framework for indicator review, comparison and selection, and to provide direction for research on indicator development. The guidelines were organized within four evaluation phases: 1) conceptual relevance, 2) feasibility of implementation, 3) response variability, and 4) interpretation and utility. Three example indicators were analyzed to illustrate the use of the guidelines in an evaluation. The examples included a direct chemical measurement (dissolved oxygen concentration), an estuarine benthic community index, and a stream fish community index of biotic integrity. Comparison of the three examples revealed differences in approach, style and types of information used to address each guideline. The Evaluation Guidelines were intended to be flexible within a consistent framework and the various strategies used in the examples demonstrate that the process can be useful for a wide variety of indicators and program objectives.

Kurtz, Janis C., Diane F. Yates, John M. Macauley, Robert L. Quarles, Fred J. Genthner, Cynthia A. Chancy and Richard Devereux. 2003. Effects of Light Reduction on Growth of the Submerged Macrophyte Vallisneria americana and the Community of Root-Associated Heterotrophic Bacteria. EPA/600/J-03/373. J. Exp. Mar. Biol. Ecol. 291(2):199-218. (ERL,GB 1169).

A shading experiment was conducted over a growing season to measure the effects of light reduction on Vallisneria americana in Perdido Bay on the Florida-Alabama border, and to determine the response of heterotrophic bacteria in the rhizosphere. Plants subjected to 92% light reduction showed the most pronounced effects in chlorophyll a concentration, above and below ground biomass, and leaf dimensions. The results and field observations further suggested the V. americanalife cycle, as exhibited in temperate waters, was impaired. Heterotrophic bacteria were enumerated and identified (i) from the roots and sediments of fully illuminated plants and from unvegetated sediments at three intervals and (ii) from the roots of plants that had been subjected to 92% light reduction for three months. Up to two orders of magnitude greater numbers of bacteria were enumerated from root samples than sediment samples on a dry weight basis. Bacteria enumerated from the roots of plants subjected to light reduction (1.3 ± 1.1 x 108 CFU g-1) were significantly higher than numbers of bacteria enumerated from the roots of fully illuminated plants (4.8 ± 1.8 x 107 g-1 in the summer) or sediment samples (1.4 ± 0.03 x 106 g-1). This suggests the roots of seagrasses stressed by light reduction provided more nutrients for bacterial growth. Higher percentages of Gram-negative bacteria were isolated from roots (up to 85% in the fall) than sediments (0-15%). Examination of isolates for traits characteristic of rhizosphere bacteria (siderophore production, formation of the phytohormone indole-3-acetic acid, and antifungal activity) did not show a clear distinction between root-associated and sediment isolates. Taxonomic identifications of root associated bacteria based on MIDI analysis of fatty acid methyl esters were consistent with bacteria known to be associated with other plants or found at oxic-anoxic interfaces. In addition, the bacterial identifications showed most species were found only with roots or only in sediments. Relative to the sediment samples, the higher numbers of bacteria and the higher incidence of Gram-negative bacteria associated with V. americana roots, together with the bacterial identifications, suggests selection of a rhizosphere bacterial community.

Kurtz, J.C., N.D. Detenbeck, V.D. Engle, K. Ho, L.M. Smith, S.J. Jordan and D. Campbell. 2006. Classifying Coastal Waters: Current Necessity and Historical Perspective. Estuaries and Coasts. 29(1):107-123. (ERL,GB 1222).

Coastal ecosystems are ecologically and commercially valuable, productive habitats that are experiencing escalating compromises of their structural and functional integrity. The Clean Water Act of 1972 (CWA) requires identification of impaired water bodies and determination of the causes of impairment. Classification simplifies these determinations, because estuaries within a class are to be more likely to respond similarly to particular stressors. We reviewed existing classification systems for their applicability to grouping coastal marine and Great Lakes water bodies based on their responses to aquatic stressors, including nutrients, toxic substances, suspended sediments, habitat alteration, and combinations of stressors. Classification research historically addressed terrestrial and freshwater habitats rather than coastal habitats. Few efforts focused on stressor response, although many well-researched classification frameworks provide information pertinent to stressor response. Early coastal classifications relied on physical and hydrological properties, including geomorphology, general circulation patterns, and salinity. More recent classifications sort ecosystems into a few broad types, and may integrate physical and biological factors. Among current efforts are those designed for conservation of sensitive habitats based on ecological processes that support patterns of biological diversity. Physical factors, including freshwater inflow, residence time, and flushing rates affect sensitivity to stressors. Biological factors such as primary production, grazing rates, and mineral cycling also need to be considered in classification. We evaluate each existing classification system with respect to objectives, defining factors, extent of spatial and temporal applicability, existing sources of data, and relevance to aquatic stressors. We also consider classification methods in a generic sense, and discuss their strengths and weaknesses for our purposes. Although few existing classifications are based on responses to stressors, many well-researched paradigms provide important information for improving our capabilities for classification as an investigative and predictive management tool.

EPA's Office of Research and Development (ORD) has prepared fifteen technical guidelines to evaluate the suitability of an ecological indicator in a monitoring program. The guidelines were fashioned to provide a consistent framework for indicator review and to provide direction for research on indicator development. They are proposed for use in characterizing the strengths and weaknesses of indicators within the context of their intended application and may be used to compare different indicators proposed for a similar purpose. The guidelines are not intended to serve as 'indicator criteria' since different programs vary in their objectives and may be willing to overlook some deficiencies in order to capture a critical strength. The fifteen guidelines are organized within four evaluation phases, originally described for indicator development in the Environmental Monitoring and Assessment Program (EMAP): (1) conceptual relevance, (2) feasibility of implementation, (3) response variability, and (4) interpretation and utility. In the EPA document that describes the guidelines, Evaluation Guidelines fo Ecological Indicators, examples of three different EMAP indicators are presented to demonstrate the types of information considered relevant to each guideline. The examples include a direct chemical measurement (dissolved oxygen), an estuarine benthic community index and a fish community index of biotic integrity.

Lewis, Michael A., Darrin D. Dantin, Calvin C. Walker, Janis C. Kurtz and Richard M. Greene. 2003. Toxicity of Clay Flocculation of the Toxic Dinoflagellate, Karenia brevis, to Estuarine Invertebrates and Fish. Harmful Algae. 2(4):235-246. (ERL,GB 1175).

The benthic environmental effects of proposed control procedures for red tide events are relatively unknown but important to understand. The objective of this study was to determine the laboratory-derived toxicities of a clay flocculation technique proposed for the Florida red tide dinoflagellate, Karenia brevis using four estuarine test species. Phosphatic clay in mixture with three concentrations (0.5, 5.0 and 50.0 mg/l of a chemical coagulant (polyaluminum hydroxy chloride) was not acutely or chronically toxic in most cases to benthic infaunal and epibenthic macroinvertebrates (Leptocheirus plumulosus, Amplesica abidita, Palemonetes pugio) and larval fish (Cyprinodon variegatus). K. brevis alone (density range = 3880 to 5060 cells/ml; brevetoxin range = 19.8 to 140.7 µg/l was very toxic to juvenile C. variegatus and, to a lesser extent, L. plumulosus. The addition of clay and coagulant did not usually mitigate this toxicity. The aggregates of clay, coagulant and K. brevis cells when settled over a natural sediment, with few exceptions, were as toxic as the red tide organism alone. This suggests that the use of this control procedure will not increase nor decrease toxicity to benthic organisms attributable to an untreated Florida red tide. Validation of this conclusion, however, is needed since it is based on laboratory-derived, single species toxicity data using media collected from a simulated red tide event. The determination of the environmental effects on indigenous biota in near-coastal areas during a natural red tide event, prior to and after treatment with clay flocculation, would provide needed perspective for a more realistic hazard assessment.

Hagy III, James D., Janis C. Kurtz and Richard M. Greene. 2008. An Approach for Developing Nutrient Criteria for a Gulf Coast Estuary. EPA/600/R-08/004. Office of Research and Development, Washington, DC. 35p. (ERL,GB 1322).

This research describes and demonstrates a manageable, science-based approach for developing water quality criteria for nutrients (nitrogen and phosphorus), chlorophyll-a, dissolved oxygen (DO), and water clarity for a single estuary, Pensacola Bay, FL. As a component of the approach, we modified the U.S. Environmental Protection Agency’s (EPA’s) percentile approach to compare water quality indicators in three salinity zones of Pensacola Bay with comparable values from other estuaries. We also conducted a broad-based quantitative assessment of both nutrient-related conditions and processes in the bay and nutrient inputs to the bay, which contribute to a logical process leading to determination of nutrient criteria. Our analysis of major nutrient-related water quality concerns in Pensacola Bay found that seasonal hypoxia and seagrass loss were the major issues. Seasonal hypoxia affected an average of 25% of the bottom area in recent studies. Seagrass loss is extensive in the system. About 95% of seagrass habitat was lost between 1950 and 1980. Almost no recovery was observed in surveys in 1992 and 2003. Yet, other indicators of ecosystem function point to lower nutrient-related impacts. Nitrogen and phosphorus loading rates to the system are moderate. Phytoplankton productivity was moderate (320 g carbon m-2 year-1) as was plankton and benthic metabolism. Nutrient concentrations were generally low, and phytoplankton were nutrient limited. Studies indicate that hypoxia may result significantly from a natural propensity toward oxygen depletion, whereas the extent of seagrass loss may be a legacy of formerly more degraded water quality conditions.We conclude that water quality criteria for nutrients and nutrient-related water quality measures could be based reasonably on currently observed conditions because evidence that more stringent criteria are scientifically defensible, necessary, or even achievable, is lacking. Hypothetical criteria resulting from application of this approach are presented.