pheophytin-a and irgarol-1051

The objectives of this study were to: (1) measure water column concentrations of Irgarol 1051 and its major metabolite GS26575 annually (2004-2006) during mid-June and mid-August at 14 sites in a study area comprised of three sub-regions chosen to reflect a gradient in Irgarol exposure (Port Annapolis marina, Severn River and Severn River reference area); (2) use a probabilistic approach to determine ecological risk of Irgarol and its major metabolite in the study area by comparing the distribution of exposure data with toxicity-effects endpoints; and (3) measure both functional and structural resident phytoplankton parameters concurrently with Irgarol and metabolite concentrations to assess relationships and determine ecological risk at six selected sites in the three study areas described above. The three-year summer mean Irgarol concentrations by site clearly showed a gradient in concentrations with greater values in Back Creek (400-500ng/L range), lower values in the Severn River sites near the confluence with Back Creek (generally values less than 100ng/L) and still lower values (<10ng/L) at the Severn River reference sites at the confluence with Chesapeake Bay. A similar spatial trend, but with much lower concentrations, was also reported for GS26575. The probability of exceeding the Irgarol plant 10th centile of 193ng/L and the microcosm NOEC (323ng/L) suggested high ecological risk from Irgarol exposure at Port Annapolis marina sites but much lower risk at the other sites. There were no statistically significant differences among the three site types (marina, river and reference) with all years combined or among years within a site type for the following functional and structural phytoplankton endpoints: algal biomass, gross photosynthesis, biomass normalized photosynthesis, chlorophyll a, chlorophyll a normalized photosynthesis and taxa richness. Therefore, based on the above results, Irgarol adverse effects predicted from the plant 10th centile and the microcosm NOEC in the high Irgarol exposure area (Back Creek/Port Annapolis marina) were not confirmed with the actual field data for the receptor species (phytoplankton). These results also highlight the importance of unconfined field studies with a chemical gradient in providing valuable information regarding the responses of resident phytoplankton to herbicides.

Topics: Biomass; Chlorophyll; Chlorophyll A; Environmental Monitoring; Maryland; Photosynthesis; Phytoplankton; Risk Assessment; Rivers; Triazines

Irgarol is a highly effective biocide used in antifouling coatings to prevent the growth of periphyton. Environmental concentrations of Irgarol in marine and freshwater have often exceeded the effect concentrations of autotrophic organisms tested in the laboratory and give reason for concern that natural periphyton communities may be endangered. A 150 days freshwater mesocosm study in 8 indoor ponds was conducted at nominal concentrations between 0.04 and 5 microgL(-1) in order to investigate the effects of Irgarol on periphyton and plankton. The results demonstrated that periphyton communities were strongly affected after single applications of 1 and 5 microgL(-1) Irgarol. For these concentrations no recovery was observed in the course of the study. For chlorophytes, the EC(50) (nominal, 135 days) was 0.34 microgL(-1). Phytoplankton also decreased in abundance directly after Irgarol application but recovered after a few weeks, as Irgarol concentrations rapidly decreased in the water body and nutrient levels increased due to lack of competition with periphyton and macrophytes. Zooplankton was indirectly affected by Irgarol. Principle response curve analysis revealed a species shift from macrophyte associated zooplankton species to free-swimming species. For species of cyclopoid copepods and ostracods the EC(50) was, respectively, 0.09 and 0.11 microgL(-1). The study simulated a best-case scenario since the mesocosms were dosed only once. Under field conditions, however, permanent exposure of organisms to Irgarol is more likely due to permanent leaching from painted ship hulls. Therefore, the effects presented in this study most likely underestimate the effects under natural conditions.

Topics: Animals; Chlorophyll; Chlorophyll A; Disinfectants; Ecosystem; Fresh Water; Lethal Dose 50; Phytoplankton; Time Factors; Triazines; Water Pollutants, Chemical; Zooplankton

The innovative bioassay described here involves chlorophyll a fluorescence measurements of gametes from the macroalgae, Hormosira banksii, where gametes (eggs) were exposed to Diuron, Irgarol and Bromacil. Response was assessed as percent inhibition from control of effective quantum yield (DeltaF/Fm') of photosystem II, herein referred to as % PSII Inhibition. This was measured with the dual-channelled pulse amplitude modulated (PAM) fluorometer, ToxY-PAM. The fluorescence bioassay was run simultaneously with an established H. banksii germination bioassay to compare sensitivity, precision, and time-to-result. The fluorescence bioassay gave highly sensitive results evidenced by EC(50)s (% PSII Inhibition) for Diuron, Irgarol and Bromacil being three, four and three orders of magnitude (respectively) lower than EC50s generated from the germination bioassays. Precision of the fluorescence bioassay was demonstrated with low coefficient of variations (<30%) for all three toxicants. With regard to time, the fluorescence bioassay gave results within 6h, as opposed to more than 50h for the germination bioassay.

Topics: Biological Assay; Bromouracil; Chlorophyll; Chlorophyll A; Diuron; Fluorescence; Germ Cells; Herbicides; Phaeophyceae; Photosynthesis; Photosystem II Protein Complex; Toxicity Tests; Triazines; Water Pollutants, Chemical

Measurements of the stress imposed by a PSII inhibiting herbicide (Irgarol 1051) on the composition of a phytoplankton community was investigated by comparing chemotaxonomy, as determined by high performance liquid chromatography (HPLC), optical microscopy and analytical flow cytometry (AFC). Changes in community structure were induced in microcosms containing a natural marine phytoplankton community exposed to different concentrations of Irgarol 1051 (0.5 and 1.0 microgl-1). Microcosms were maintained under controlled laboratory conditions in semi-continuous culture over 120 h. Class-specific phytoplankton biomass (chlorophyll a) was estimated using CHEMTAX analyses of pigment concentrations. Microscopic identification and carbon content estimates were cross-correlated with CHEMTAX and also with AFC enumeration/size classifications of major phytoplankton groups. CHEMTAX-HPLC analyses and microscopy results demonstrated that prasinophytes and prymnesiophytes were the most affected groups following exposure to Irgarol 1051. The selective reductions in both classes as estimated by both techniques revealed similar trends. Results for chlorophytes and dinoflagellates showed these groups to be most tolerant to Irgarol 1051. Indeed, class-specific biomass for chlorophytes as determined by CHEMTAX and microscopy were correlated (R2=0.53) which demonstrated an increase in both abundance and carbon content following exposures to Irgarol 1051. Abundances of nanoeukaryotes as determined by microscopy afforded good agreement with results from AFC (R2=0.8), although for picoeukaryotes, abundances were underestimated by microscopy (R2=0.43). The relative performance of the selected techniques is discussed.

Topics: Biomass; Chlorophyll; Chlorophyll A; Chromatography, High Pressure Liquid; Flow Cytometry; Herbicides; Light; Microscopy, Fluorescence; Photosystem II Protein Complex; Phytoplankton; Regression Analysis; Seawater; Triazines; Water Microbiology; Water Pollutants, Chemical

The objectives of this study were to measure: (1) Irgarol and GS26575 (major metabolite) during the peak 2004 boating season at selected marinas and reference areas in the Carolinian Zoogeographic Province of the Eastern United States; (2) Irgarol and GS26575 at selected stations during the summer months in the Back Creek/Severn River area in Maryland in 2003 and 2004; and (3) structural and functional characteristics of resident phytoplankton communities concurrently with Irgarol and GS26575 monitoring in Back Creek/Severn River area. Irgarol concentrations from 14 marinas in the Carolinian Province ranged from non-detectable (<1 ng/L) to 85 ng/L; concentrations were less than 16 ng/L at all reference sites. The probability of exceeding the plant 10th centile for Irgarol (251 ng/L) was less than 0.6% for all marinas and 0.01% for all reference areas. These data suggest low ecological risk from Irgarol exposure for both marina and reference areas in the Carolinian Province. Irgarol concentrations ranged from 5 ng/L at the Severn River reference site to 1,816 ng/L in Port Annapolis marina during the two year study. Ecological risk from Irgarol exposure was high for the Port Annapolis marina sites based on a probability of exceeding the plant 10th centile. However, risk was low for Severn River and Severn River reference sites. Functional and structural measures of resident phytoplankton communities in the Back Creek and Severn River did not suggest that these target species are impaired in the Port Annapolis marina area where probabilistic analysis predicted adverse effects from Irgarol exposure.

Topics: Analysis of Variance; Atlantic Ocean; Chlorophyll; Chlorophyll A; Environmental Monitoring; Gas Chromatography-Mass Spectrometry; Geography; Oxygen; Phytoplankton; Southeastern United States; Triazines; Water Pollutants, Chemical