Monitoring of Irgarol 1051 concentrations with concurrent phytoplankton evaluations in East Coast areas of the United States

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.     

Occurrence and transport of Irgarol 1051 and its major metabolite in coastal waters from South Florida

Irgarol 1051, a boosting antifouling agent often used to supplement copper based paints was found in surface waters from South Florida at stations collected from the Miami River, Biscayne Bay and selected areas of the Florida Keys. Concentrations of the herbicide ranged from below the method detection limit (1 ng/L) to as high as 182 ng/L in a canal system in Key Largo. The herbicide was present at 93% of the stations and often found in conjunction with its descyclopropyl metabolite (M1) previously reported to be the major degradation product of Irgarol under natural environmental conditions. The 90th percentile concentration calculated for all South Florida samples was 57.6 ng/L. Based on available data on the toxicity of Irgarol to algae and coral, only two stations (approximately 3%) ranked above the LC50 of 136 ng/L reported for the marine algae Naviculla pelliculosa and above the 100 ng/L level reported to reversibly inhibit photosynthesis of intact corals. However, a basic dissipation model for Irgarol using the Key Largo Harbor station as a point source indicated that concentrations of the herbicide decreased rapidly and concentrations below the MDL are observed within 2000 m of the source. No major coral based benthic habitats are documented for all the stations surveyed at distances that Irgarol may pose a substantial risk. However, other types of submerged vegetation like seagrasses are common around the marinas and the effects of Irgarol to such endpoints should be investigated further.     

Toxicities of antifouling biocide Irgarol 1051 and its major degraded product to marine primary producers

Irgarol 1051 (2-methythiol-4-tert-butylamino-6-cyclopropylamino-s-triazine) is an algaecide commonly used in antifouling paints. It undergoes photodegradation which yields M1 (2-methylthio-4-tert-butylamino-6-amino-s-triazine) as its major and most stable degradant. Elevated levels of both Irgarol and M1 have been detected in coastal waters worldwide; however, ecotoxicity effects of M1 to various marine autotrophs such as cyanobacteria are still largely unknown. This study firstly examined and compared the 96 h toxicities of Irgarol and M1 to the cyanobacterium Chroococcus minor and two marine diatom species, Skeletonema costatum and Thalassiosira pseudonana. Our results suggested that Irgarol was consistently more toxic to all of the three species than M1 (96 h EC50 values: C. minor, 7.71 microug L(-1) Irgarol vs. > 200 microg L(-1) M1; S. costatum, 0.29 microg L(-1) Irgarol vs. 11.32 microg L(-1)M1; and T. pseudonana, 0.41 microg L(-1) Irgarol vs. 16.50 microg L(-1)M1). Secondly, we conducted a meta-analysis of currently available data on toxicities of Irgarol and M1 to both freshwater and marine primary producers based on species sensitivity distributions (SSDs). Interestingly, freshwater autotrophs are more sensitive to Irgarol than their marine counterparts. For marine autotrophs, microalgae are generally more sensitive to Irgarol than macroalgae and cyanobacteria. With very limited available data on M1 (i.e. five species), M1 might be less toxic than Irgarol; nonetheless this finding warrants further confirmation with additional data on other autotrophic species.     

Toxicities of antifouling biocide Irgarol 1051 and its major degraded product to marine primary producers

Irgarol 1051 (2-methythiol-4-tert-butylamino-6-cyclopropylamino-s-triazine) is an algaecide commonly used in antifouling paints. It undergoes photodegradation which yields M1 (2-methylthio-4-tert-butylamino-6-amino-s-triazine) as its major and most stable degradant. Elevated levels of both Irgarol and M1 have been detected in coastal waters worldwide; however, ecotoxicity effects of M1 to various marine autotrophs such as cyanobacteria are still largely unknown. This study firstly examined and compared the 96 h toxicities of Irgarol and M1 to the cyanobacterium Chroococcus minor and two marine diatom species, Skeletonema costatum and Thalassiosira pseudonana. Our results suggested that Irgarol was consistently more toxic to all of the three species than M1 (96 h EC50 values: C. minor, 7.71 μg L⁻¹ Irgarol vs. >200 μg L⁻¹ M1; S. costatum, 0.29 μg L⁻¹ Irgarol vs. 11.32 μg L⁻¹ M1; and T. pseudonana, 0.41 μg L⁻¹ Irgarol vs. 16.50 μg L⁻¹ M1). Secondly, we conducted a meta-analysis of currently available data on toxicities of Irgarol and M1 to both freshwater and marine primary producers based on species sensitivity distributions (SSDs). Interestingly, freshwater autotrophs are more sensitive to Irgarol than their marine counterparts. For marine autotrophs, microalgae are generally more sensitive to Irgarol than macroalgae and cyanobacteria. With very limited available data on M1 (i.e. five species), M1 might be less toxic than Irgarol; nonetheless this finding warrants further confirmation with additional data on other autotrophic species.     

Inhibition of coral photosynthesis by the antifouling herbicide Irgarol 1051

International regulation of organotin compounds for use in antifouling paints has led to the development and increased use of replacement compounds, notably the s-triazine herbicide Irgarol 1051. Little is known about the distribution of Irgarol 1051 in tropical waters. Nor has the potential impact of this triazine upon photosynthesis of endosymbiotic microalgae (zooxanthellae) in corals been assessed. In this study Irgarol 1051 was detected in marinas, harbours and coastal waters of the Florida Keys, Bermuda and St. Croix, with concentrations ranging between 3 and 294 ng 1(-1). 14C incubation experiments with isolated zooxanthellae from the common inshore coral Madracis mirabilis showed no incorporation of H14CO3- from the sea water medium after 4-8 h exposure to Irgarol 1051 concentrations as low as 63 ng 1(-1). Reduction in net photosynthesis of intact corals was found at concentrations of l00 ng 1(-1) with little or no photosynthesis at concentrations exceeding 1000 ng 1(-1) after 2-8 h exposure at all irradiances. The data suggest Irgarol 1051 to be both prevalent in tropical marine ecosystems and a potent inhibitor of coral photosynthesis at environmentally relevant concentrations.     

Contamination of Caribbean coastal waters by the antifouling herbicide Irgarol 1051

Irgarol 1051 is a s-triazine herbicide used in popular slime-resistant antifouling paints. It has been shown to be acutely toxic to corals, mangroves and sea grasses, inhibiting photosynthesis at low concentrations (>50 ng l(-1)). We present the first data describing the occurrence of Irgarol 1051 in coastal waters of the Northeastern Caribbean (Puerto Rico (PR) and the US Virgin Islands (USVI)). Low level contamination of coastal waters by Irgarol 1051 is reported, the herbicide being present in 85% of the 31 sites sampled. It was not detected in water from two oceanic reference sites. In general, Irgarol 1051was present at concentrations below 100 ng l(-1), although far higher concentrations were reported at three locations within Benner Bay, USVI (223-1,300 ng l(-1)). The known toxicity of Irgarol 1051 to corals and sea grasses and our findings of significant contamination of the Northeastern Caribbean marine environment by this herbicide underscore the importance of understanding, more fully, local and regional exposure of reef and sea grass habitats to Irgarol 1051 and, where necessary, implementing actions to ensure adequate protection of these important ecosystems.     

Occurrence of Irgarol 1051 and its major metabolite in Maryland waters of Chesapeake Bay

Irgarol and its major metabolite (GS26575) were measured in Maryland waters of Chesapeake Bay: (1) in and near 10 marinas, a mainstem Bay site and two Severn River locations during a general survey in July and December of 2002; (2) at various sites in the Port Annapolis Marina and the Severn River area during March of 2002 before the boating season began; and (3) during July (peak boating season) in the same Port Annapolis Marina and Severn River sites area during both an ebb and flood tide. Irgarol concentrations ranged from 1.82 ng/l at the mid-Bay site to 585 ng/l in Port Annapolis marina during the July and December general survey. An Irgarol 90th centile of 239 ng/l was reported for the 10 marina sites, two Severn River sites and one mainstem site sampled during the general survey conducted in July and December. Temporal analysis of all pooled data showed that 90th centiles were over seven times higher in July when compared to December. A comparison of Irgarol concentrations at 12 sites in the Port Annapolis marina and Severn River area during both an ebb and flood tide in July showed no consistent trend with tidal cycle by site although significant reductions in concentrations were reported with distance from the three Port Annapolis marina sites. Ecological risk from Irgarol exposure was judged to be low for most Chesapeake Bay sites sampled. Possible exceptions were Port Annapolis marina, Severn River sites in close proximity to this marina and Chesapeake Harbor marina where Irgarol concentrations exceeded a conservative effects threshold during the peak boating season in July. Ecological risk from GS26575 exposure was low for all sites.     

Seasonal variability in the concentrations of Irgarol 1051 in Brighton Marina,UK; including the impact of dredging

Variations in Irgarol 1051 concentrations in the UK's largest marina at Brighton were determined regularly over a period of one year. Aqueous concentrations ranged from <1 to 960 ngl(-1) with highest mean concentrations generally associated with berths for larger vessels and with the main channels. Temporally, highest concentrations were recorded in November through to January and were probably associated with maintenance of vessels in an adjacent boatyard. Elevated levels were also encountered at the beginning of the season, coinciding with the introduction of newly antifouled vessels. Increased concentrations also followed dredging, possibly through re-mobilisation of Irgarol 1051. No correlations were found between dissolved Irgarol 1051 concentrations and pH, temperature or salinity. With the exception of sporadically high concentrations recorded for water samples (probably taken in close proximity to recently antifouled vessels), concentrations rarely exceeded the no observed effect concentration for marine periphyton of 63 ngl(-1). Concentrations of Irgarol 1051 in sediments sampled from the marina ranged from <1 to 77 ngg(-1). Apparent distribution coefficients (K(d)) calculated from sedimentary and aqueous samples (collected simultaneously) are generally within the range of K(d)'s reported from laboratory experiments.     

The impact of legislation on the usage and environmental concentrations of Irgarol 1051 in UK coastal waters

In 2001, legislative measures were introduced in the UK to restrict usage of antifouling agents in small (<25 m) vessel paints to dichlofluanid, zinc pyrithione and zineb. This removed the previously popular booster biocides diuron and Irgarol 1051 from the market. To investigate the impact of this legislation, water samples were taken from locations where previous biocide levels were well documented. Results from analyses demonstrate a clear reduction in water concentrations of Irgarol 1051 (between 10% and 55% of that found during pre-restriction studies), indicating that legislation appears to have been effective. Although other booster biocides were screened for (chlorothalonil, dichlofluanid and Sea-Nine 211), they were below the limits of detection (<1 ng/l) in all samples. A survey of chandlers and discussions with legislative authorities supports these results and concurs the removal of Irgarol 1051 based paints from the market using simple regulations at a manufacturer level with little regulation at a retailer level.     

Contamination of the coastal waters of Bermuda by organotins and the triazine herbicide Irgarol 1051.

A study of the distribution of the 'booster' biocide 2-methylthio-4-tert-butylamino-6-cyclopropyl amino-s-triazine (Irgarol 1051) was carried out in the coastal waters of Bermuda. Irgarol 1051 concentrations (as determined by GC/MS) up to 590 ng l-1 have been measured within Hamilton Harbour. The data presented herein unequivocally demonstrate contamination of the coastal system of Bermuda by Irgarol 1051. Concurrently, TBT concentrations were measured and results indicate that levels are falling through legislated changes in antifouling treatments, from 220 ng l-1 in 1990 to < 20 ng l-1 (as Sn) by 1995, in the open water area of Hamilton Harbour. Concentrations of TBT immediately offshore from a boatyard were found to be > 600 ng l-1 (Sn), indicating continuing release due to painting operations and sediments in the area.     

Occurrence of IRGAROL 1051 in coastal waters from Biscayne Bay,Florida, USA

Surface water samples from marinas, commercial ports and open bay areas collected from Biscayne Bay and the Miami River, Florida, USA, were analyzed for the occurrence of IRGAROL 1051 by GC/MS. The anifouling boosting herbicide was found in 80% (46/57) of the samples collected between March 1999 and September 2000. Concentrations within the bay range between non-detected (<1 ppt) and 61 ppt (ng/L) and were generally low compared with levels reported in European or Japanese waters. Aside from the elevated concentrations observed along the Miami River South Fork (61 ppt), the highest concentrations observed in the bay corresponded to marinas with high density of pleasure craft and restricted water circulation. In contrast, occurrence of IRGAROL 1051 along the commercial port or the cruise line terminal was generally lower (<1-2.2 ppt). Concentrations around Coconut Grove Marina were consistently higher (5-12 ppt) than the rest of the bay waters during the whole period of time surveyed.     

Ecological risk of Irgarol 1051 and its major metabolite in coastal California marinas and reference areas

The objective of this study was to use a probabilistic approach to determine the ecological risk of Irgarol and its major metabolite (GS26575) in coastal California marinas and reference areas by using monitoring data collected during the summer of 2006. Distributions of environmental exposure data were compared with the distribution of plant species response data from laboratory toxicity studies and the no observed effect concentration (NOEC) from a microcosm study to quantify the likelihood and significance of ecological risk. Toxicity testing indicates plants are much more sensitive to Irgarol than animals; therefore, the conservative effects benchmark used to characterize risk was the plant 10th centile for both Irgarol (193 ng/L) and GS26575 (5622 ng/L). In addition, the microcosm NOEC of 323 ng/L was also used to characterize risk. Irgarol concentrations from 15 California marinas ranged from 1.45 to 339 ng/L while GS26575 concentrations ranged from non-detected to 74 ng/L. The probability of exceeding the Irgarol plant 10th centile of 193 ng/L for 15 marinas sampled in coastal California in 2006 was 7.3% while the probability of exceeding the microcosm NOEC of 323 ng/L was even lower (5.5%). In general, this probability of exceedence for either effects benchmark and subsequent ecological risk is considered to be low for these marinas as only one marina (Kings Harbor marina in Redondo Beach) had measured concentrations of Irgarol exceeding 193 ng/L. Irgarol exposure is concentrated within marinas and ecological risk from Irgarol exposure in adjoining reference areas was judged to be very low. Ecological risk from GS26575 exposure was also low in both marina and reference areas in California.     

The relationship of Irgarol and its major metabolite to resident phytoplankton communities in a Maryland marina, river and reference area

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 (400-500 ng/L range), lower values in the Severn River sites near the confluence with Back Creek (generally values less than 100 ng/L) and still lower values (<10 ng/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 193 ng/L and the microcosm NOEC (323 ng/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.     

The effects of prolonged darkness on temperate and tropical marine phytoplankton, and their implications for ballast water risk management

Phytoplankton assemblages from tropical (Goa) and temperate (UK) locations were exposed to a 28 day dark period, followed by a period of re-exposure to light. During this time phytoplankton survival and changes in nutrient concentrations were mapped. The tropical plankton water samples showed high nutrient levels after the dark period which were utilised by cells during the re-exposure period. UK experiments looked at the effect of three different water types on population recovery after the 28 day dark period, and differences due to seasonal effects.The population growth observed during the re-exposure period in the tropical population was comparable to that of the temperate population. Water type affected recovery and of the three tested media fresh seawater promoted the highest levels of growth. Seasonality had a significant influence on species survival. Understanding the effects of all these factors can aid the development of effective risk assessments in ballast water management.     

Assessing underwater noise levels during pile-driving at an offshore windfarm and its potential effects on marine mammals

Marine renewable developments have raised concerns over impacts of underwater noise on marine species, particularly from pile-driving for wind turbines. Environmental assessments typically use generic sound propagation models, but empirical tests of these models are lacking. In 2006, two 5 MW wind turbines were installed off NE Scotland. The turbines were in deep (>40 m) water, 25 km from the Moray Firth Special Area of Conservation (SAC), potentially affecting a protected population of bottlenose dolphins. We measured pile-driving noise at distances of 0.1 (maximum broadband peak to peak sound level 205 dB re 1 μPa) to 80 km (no longer distinguishable above background noise). These sound levels were related to noise exposure criteria for marine mammals to assess possible effects. For bottlenose dolphins, auditory injury would only have occurred within 100 m of the pile-driving and behavioural disturbance, defined as modifications in behaviour, could have occurred up to 50 km away.     

Application of a barrier island translation model to the millennial-scale evolution of Sand Key,Florida

The evolution of a barrier island and its stratigraphic architecture is investigated with the numerical model BIT (barrier island translation). The model simulates, with simplified equations, the effects of various processes (wind waves, storm surges, sea-level oscillations) on sediment location and characteristics. The presented formulation is able to reproduce both the cross-shore profile and the distribution of sediment facies in time.