Portal de Periódicos da CAPES

Total and Inorganic Arsenic in Mid-Atlantic Marine Fish and Shellfish and Implications for Fish Advisories

2006; Wiley; Volume: 2; Issue: 4 Linguagem: Inglês

10.1897/1551-3793(2006)2[344

1551-3793

Richard W. Greene, E.A. Crecelius,

Heavy metals in environment

Integrated Environmental Assessment and ManagementVolume 2, Issue 4 p. 344-354 Original ResearchFree Access Total and inorganic arsenic in mid-atlantic marine fish and shellfish and implications for fish advisories Richard Greene, Corresponding Author Richard Greene [email protected] Delaware Department of Natural Resources and Environmental Control, 820 Silver Lake Boulevard, Suite 220, Dover, Delaware 19904–2464, USADelaware Department of Natural Resources and Environmental Control, 820 Silver Lake Boulevard, Suite 220, Dover, Delaware 19904–2464, USASearch for more papers by this authorEric Crecelius, Eric Crecelius Battelle Marine Sciences Laboratory, 1529 West Sequim Bay Road, Sequim, Washington 98382, USASearch for more papers by this author Richard Greene, Corresponding Author Richard Greene [email protected] Delaware Department of Natural Resources and Environmental Control, 820 Silver Lake Boulevard, Suite 220, Dover, Delaware 19904–2464, USADelaware Department of Natural Resources and Environmental Control, 820 Silver Lake Boulevard, Suite 220, Dover, Delaware 19904–2464, USASearch for more papers by this authorEric Crecelius, Eric Crecelius Battelle Marine Sciences Laboratory, 1529 West Sequim Bay Road, Sequim, Washington 98382, USASearch for more papers by this author First published: 05 November 2009 https://doi.org/10.1002/ieam.5630020406Citations: 14AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract Sampling was conducted in 2002 to determine the total concentration and chemical speciation of arsenic in several marine fish and shellfish species collected from the Delaware Inland Bays and the Delaware Estuary, both of which are important estuarine waterbodies in the US Mid-Atlantic region that support recreational and commercial fishing. Edible meats from summer flounder (Paralicthys dentatus), striped bass (Marone saxatilis), Atlantic croaker (Micropogonias undulates), and hard clam (Mercenaria mercenaria) were tested. Total arsenic was highest in summer flounder, followed by hard clam, then striped bass, and finally, Atlantic croaker. Total arsenic was higher in summer flounder collected during the spring, as these fish migrated into the Inland Bays from the continental shelf, compared with levels in summer flounder collected during the fall, after these fish had spent the summer in the Inland Bays. Similarly, striped bass collected in the early spring close to the ocean had higher total arsenic levels compared with levels detected in striped bass collected later during the year in waters with lower salinity. Speciation of arsenic revealed low concentrations (0.00048–0.02 μg/g wet wt) of toxic inorganic arsenic. Dimethylarsinic acid was more than an order of magnitude greater in hard clam meats than in the other species tested, a finding that was attributed to arsenic uptake by phytoplankton and subsequent dietary uptake by the clam. Risk assessment using the inorganic arsenic concentrations was used to conclude that a fish consumption advisory is not warranted. INTRODUCTION The Delaware Inland Bays and the nearby Delaware Estuary provide important recreational and commercial fishing opportunities for the people who reside and visit the US Mid-Atlantic region. Figure 1 shows the location of these 2 near-coastal waterways. The Delaware Estuary, which flows through the Philadelphia (PA, USA)-Camden (NJ, USA)-Wilmington (DE, USA) urban center, has several fish consumption advisories in place. In contrast, the Delaware Inland Bays, which are a series of coastal lagoons in southeastern Delaware, are far less urbanized, and no fish consumption advisories are currently in place. The Inland Bays are hydraulically connected to the Atlantic Ocean through a stabilized inlet, allowing coastal species to migrate into and out of the bays. Baseline data regarding total arsenic in summer flounder (Paralicthys dentatus), Atlantic croaker (Micropogonias undulates), and hard clam (Mercenaria mercenaria) from the Inland Bays are presented in Table 1 along with similar data concerning total arsenic for striped bass (Marone saxatilis) from the Delaware Estuary (DNREC 2005). Figure 1 shows where these samples were collected. Baseline data regarding inorganic arsenic in fish and shellfish from the 2 waterways are not available. From Table 1, total arsenic in summer flounder has historically ranged from 0.59 to 3.27 μg/g wet weight (ww) fillet, with no indication that concentration is related to fish length. Total arsenic in the single Atlantic croaker sample was 0.91 μg/g ww fillet, whereas total arsenic in the 2 hard clam samples ranged from 0.78 to 1.66 μg/g ww edible meat. Finally, total arsenic in striped bass collected from the Delaware Estuary ranged from an estimated minimum of 0.09 μg/g ww fillet to a maximum of 1.11 μg/g ww fillet. The first 5 striped bass samples listed in Table 1 were collected in the lower Delaware Estuary, close to the Atlantic Ocean. The second 5 striped bass samples listed in Table 1 were collected farther north, in the more urbanized/industrialized and less saline portion of the Delaware Estuary. Note that the striped bass collected in the more urban/industrial portion of the estuary had significantly lower total arsenic concentrations than the striped bass collected in the estuary near the ocean, despite being of comparable size and despite the perception that concentrations likely would be higher in more urbanized and industrialized waters. This interesting observation served as the seed for our hypothesis that marine species that migrate from the shelf waters into near-coastal waters of the Delaware Estuary and Delaware Inland Bays bring body burdens of total arsenic with them that are higher than the levels they leave with during their seaward migration. This may be true merely because the natural levels of arsenic in seawater are higher, on average, than the natural levels of arsenic in freshwater (Smedley and Kinniburgh 2002). Alternatively, or in addition, there could be a source of arsenic on the shelf waters adjacent to the Delaware Estuary and Delaware Inland Bays that has not been identified and characterized. In either event, where and how migratory coastal fish acquire their chemical body burden are important questions that provide a broader context for fish tissue monitoring and health advisory programs. An understanding of where coastal species acquire their body burden begins with an understanding of their migratory patterns. Figure Figure 1.Open in figure viewerPowerPoint Mid-Atlantic coastal region showing the Delaware Inland Bays and the Delaware Estuary (USA) along with the locations of baseline fish and shellfish samples. Summer flounder are demersal fish that migrate into and out of the Inland Bays on a seasonal basis. Adults migrate into the Inland Bays during the spring from their overwintering grounds on the Continental Shelf (Wang and Kernehan 1979). They remain in the bays and along the immediate coast throughout the summer, then migrate back offshore during the fall. The adults are believed to spawn during this fall migration back to the shelf. Similarly, adult Atlantic croaker migrate into and out of the Inland Bays on a seasonal basis, entering in the spring as the water warms and leaving in the late fall as the inland water cools. Spawning occurs in the adjacent Atlantic Ocean, with peak activity between October and February (Wang and Kernehan 1979). Adult hard clam, in contrast to summer flounder and Atlantic croaker, are sedentary, year-round residents of the Delaware Inland Bays. As such, their body burden is not confounded by potential contaminant exposures received hundreds of miles away. The migratory pattern of striped bass found in the Delaware Estuary is not fully understood, although a few major features are recognized. After spawning during the spring in low-salinity waters of the estuary, some striped bass migrate out to the Atlantic Ocean, whereas others remain in the estuary. The larger and older females are more likely to migrate back to the ocean, whereas a significant fraction of the mature males may stay within the Delaware Estuary system (ASMFC 2004). To test our hypothesis that fish that migrate into near-coastal waters from the ocean have higher body burdens of arsenic compared with fish that migrate back offshore, it is necessary to collect fish at different times and places during their annual migration. Our strategy was to collect summer flounder, Atlantic croaker, and striped bass as these species move inland from the coast and then again later in the season, before they move back offshore. Hard clam also was tested as a resident control for the Delaware Inland Bays. Table Table 1.. Baseline data regarding arsenic in selected marine fish and shellfish from the Delaware Inland Bays and the Delaware Estuarya Station Latitude (N) Longitude (W) Date sampled Speciesb Sample size (n) Length (mm) Weight (g) Total arsenic (μg/g wet wt) 1 38°36′03.0″ −75°07′33.0″ 17 July 1990 Hard clam 21 NA NA 0.78 2 38°39′08.0″ −75°06′19.0″ 17 July 1990 Hard clam 11 NA NA 1.66 1 38°36′03.0″ −75°07′33.0″ 24 September 1991 Summer flounder 1 360 425 0.59 1 38°36′03.0″ −75°07′33.0″ 24 September 1991 Summer flounder 1 335 350 1.06 3 38°36′30.9″ −75°05′03.9″ 10 September 1992 Summer flounder 3 335 375 3.27 4 38°36′13.3″ −75°04′46.2″ 11 August 1999 Summer flounder 3 366 450 2.40 5 38°38′07.0″ −75°05′51.9″ 10 August 1999 Atlantic croaker 5 274 297 0.91 6 39°00′02.8″ −75°10′30.3″ 28 February 1997 Striped bass 1 796 5970 1.11 6 39°00′02.8″ −75°10′30.3″ 28 February 1997 Striped bass 1 730 4460 0.73 6 39°00′02.8″ −75°10′30.3″ 4 March 1997 Striped bass 1 755 5443 0.69 6 39°00′02.8″ −75°10′30.3″ 4 March 1997 Striped bass 1 730 4536 0.55 6 39°00′02.8″ −75°10′30.3″ 14 April 1997 Striped bass 1 795 4876 0.13 J 7 39°44′30.6″ −75°29′44.7″ 28 May 1997 Striped bass 1 712 4082 0.12 J 7 39°44′30.6″ −75°29′44.7″ 28 May 1997 Striped bass 1 835 6350 <0.2 7 39°44′30.6″ −75°29′44.7″ 5 June 1997 Striped bass 1 725 4082 0.1 J 7 39°44′30.6″ −75°29′44.7″ 5 June 1997 Striped bass 1 900 7257 0.14 J 7 39°44′30.6″ −75°29′44.7″ 5 June 1997 Striped bass 1 840 9071 0.09 J a Fish samples were analyzed as skin-on fillets. Hard clam was analyzed as edible meats. NA = not available/applicable; J = analyte present (reported value is estimated; measured concentration was below the range for accurate quantitation); < = analyte not present at the indicated detection limit. b Hard clam, Mercenaria mercenaria; summer flounder, Paralicthys dentatus; Atlantic croaker, Micropogonias undulates; striped bass, Marone saxatilis. MATERIALS AND METHODS Field collection Ten summer flounder samples were collected by hook and line from Delaware's Inland Bays during 2002. Five individual flounder were collected in the spring of 2002 as these fish 1st entered the Inland Bays during their inland migration from offshore waters. Five individuals were then collected in the fall of 2002 during their outward migration from the Inland Bays back offshore. Attempts to secure additional flounder of the target size during the spring and fall sampling windows to make the study more powerful were unsuccessful. The flounder samples were supplemented with 5 individual Atlantic croaker samples collected by gill net from the Inland Bays during the summer of 2002. We were not able to catch croaker in the fall of 2002 during their outward migration from the Inland Bays. Finally, 2 hard clam samples were collected by hand rake from the Inland Bays during the summer of 2002. Each of the hard clam samples was composed of soft tissue (meats) from multiple clams, with the free liquid decanted before processing. In addition to the samples collected within the Inland Bays, 10 individual striped bass samples also were collected from the nearby Delaware Estuary. Five individual striped bass were collected by gill net in late March 2002 in the lower to mid-Delaware Bay. Five additional individual striped bass were collected by electroshocking in May 2002 farther up the Delaware Estuary in the vicinity of Cherry Island Flats, an important spawning area for striped bass. At the point of collection, all fish samples were individually wrapped in aluminum foil, labeled, placed into a plastic zip-lock bag, and then stored in a cooler on wet ice for transport back to the laboratory. On arrival at the laboratory, the samples were logged, weighed, and measured. All finfish were prepared for analysis as skin-on fillets using precleaned cutting tools and cutting surfaces. Individual fillets were passed through a precleaned meat grinder to produce a consistent tissue homogenate. The homogenate was stored in precleaned glassware and frozen at −20°C until being shipped on dry ice to Battelle Marine Sciences Laboratory for arsenic analysis. Laboratory The ground fish tissue samples were received frozen at the Battelle Marine Sciences Laboratory. The samples were logged and inspected to determine if any breakage or thawing had occurred during shipping. The samples were reported to be in good condition on arrival. When ready for analysis, the wet tissue samples were thawed, and 0.5 g of wet tissue was digested in 10 mL of 2 M hot sodium hydroxide at 80 °C for 8 h or overnight. The digestates were stored at 4°C before being analyzed for total arsenic by inductively coupled plasma-mass spectrometry using US Environmental Protection Agency (USEPA) Method 200.8 (USEPA 1994) and by hydride atomic absorption using USEPA Method 1632A (USEPA 2001) for arsenic speciation. These same methods were used in the analysis of marine fish reported by the USEPA (USEPA 2003) and by researchers who investigated total and inorganic arsenic in a market basket survey (Schoof et al. 1999). A 1-mL aliquot of the digestate was analyzed for inorganic arsenic [sum of arsenic(III) and arsenic(V)], monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) at pH 1 by arsine generation with the reducing-agent sodium borohydride. The arsine and methyl arsines were collected on a cryogenic column before quantification by atomic absorption using a quartz tube with an air-hydrogen flame positioned in the light path. Table Table 2.. Quality-assurance results for 2002 samplesa Total arsenic (μg/g wet wt)b Inorganic arsenic (μg/g wet wt) MMA (μg/g wet wt) DMA (μg/g wet wt) Procedural blanks Procedural blank 1 0.04 U 0.03 0.01 0.04 U Procedural blank 2 0.04 U 0.03 0.01 0.04 U Matrix spike results Amount spiked 13.9 4.64 4.64 4.64 0203029–001 2.19 0.03 U 0.01 U 0.00757 J 0203029–001 MS 13.6 5.80 5.81 4.64 Amount recovered 11.4 5.80 5.81 4.64 % Recovery 82% 125% 125% 100% Amount spiked 14.6 4.87 4.87 4.87 0205053–004 0.362 0.03 U 0.01 U 0.04 U 0205053–004 MS 12.3 5.98 6.11 4.39 Amount recovered 11.9 5.98 6.11 4.39 % Recovery 82% 123% 125% 90% Standard reference material DORM-2 17.1 NA NA NA Certified value 18.0 NC NC NC Range ±1.1 % Difference 5% NA NA NA Replicate analysis results 0209047–006A 1.32 0.03 U 0.01 U 0.04 U 0209047–006A 1.27 0.03 U 0.01 U 0.04 U Relative % difference 4% NA NA NA a MMA = monomethylarsonic acid; DMA = dimethylarsinic acid; NA = not available/applicable; NC = not certified; NS = not spiked; J = detected above blank and less than the method detection limit; U = not detected. b Results for total arsenic are listed on a wet weight basis except for the standard reference material, which are expressed on a dry weight basis. Quality-control testing included procedural blanks, matrix spikes, replicate analyses, and analysis of a certified reference material (DORM-2, dogfish muscle tissue) obtained from the National Research Council of Canada (Ottawa, ON). Table 2 summarizes the quality-assurance results. The results for the procedural blanks were below the method detection limits of 0.04 μg/g ww for total arsenic, 0.03 μg/g ww for inorganic arsenic, 0.01 μg/g ww for MMA, and 0.04 μg/g ww for DMA. The mean procedural blank for inorganic arsenic was 0.006 μg/g ww. The field samples were corrected for this mean procedural blank by subtracting 0.006 μg/g ww from the inorganic arsenic concentrations in the field samples. No detectable signal was found for MMA or DMA in the procedural blanks. The arsenic speciation results that were detected above the blank and less than the method detection limit were reported with a "J" flag. If no signal was detected after blank correction, then the concentrations were reported at the detection limit and with a "U" flag. The results for matrix spikes and laboratory replicates were within the method performance criteria. The result for total arsenic in DORM-2 was within 5% of the certified value of 18.0 μg/g dry weight. DORM-2 is not certified for the arsenic species. The concentration of DMA in DORM-2 was 0.36 μg/g dry weight, which compares well with a concentration of 0.28 μg/g dry weight reported by Goessler et al. (1997). Based on the quality-assurance results, the data were judged to be suitable for subsequent use and analysis. Table Table 3.. Arsenic speciation of marine fish and shellfish from the Mid-Atlantic region, USAa Sample Waterbody Latitude (N) Longitude (W) Date sampled Speciesb Sample size (n) Length (mm) Weight (g) Total arsenic (μg/g wet wt) Inorganic arsenic (μg/g wet wt) MMA (μg/g wet wt) DMA (μg/g wet wt) 0205072–001 DE Inland Bays 38°36′13.3″ −75°04′46.2″ 29 May 2002 Summer flounder 1 520 1500 3.33 0.03 U 0.00342 J 0.0119 J 0205072–002 DE Inland Bays 38°36′13.3″ −75°04′46.2″ 29 May 2002 Summer flounder 1 445 840 2.58 0.03 U 0.00115 J 0.00503 J 0205072–003 DE Inland Bays 38°36′13.3″ −75°04′46.2″ 29 May 2002 Summer flounder 1 410 720 3.08 0.03 U 0.01 U 0.0117 J 0205072–004 DE Inland Bays 38°36′13.3″ −75°04′46.2″ 4 June 2002 Summer flounder 1 500 1200 2.25 0.03 U 0.01 U 0.00559 J 0205072–005 DE Inland Bays 38°36′13.3″ −75°04′46.2″ 11 June 2002 Summer flounder 1 475 1050 1.80 0.03 U 0.00198 J 0.00790 J 0209047–002 DE Inland Bays 38°36′13.3″ −75°04′46.2″ 17 September 2002 Summer flounder 1 390 585 1.49 0.00048 J 0.01 U 0.00839 J 0209047–003 DE Inland Bays 38°36′13.3″ −75°04′46.2″ 18 September 2002 Summer flounder 1 425 740 2.13 0.03 U 0.01 U 0.00729 J 0209047–004 DE Inland Bays 38°36′13.3″ −75°04′46.2″ 23 September 2002 Summer flounder 1 445 950 2.08 0.03 U 0.00183 J 0.00562 J 0209047–005 DE Inland Bays 38°36′13.3″ −75°04′46.2″ 30 September 2002 Summer flounder 1 452 1100 0.95 0.03 U 0.00268 J 0.00603 J 0209047–006 DE Inland Bays 38°36′13.3″ −75°04′46.2″ 30 September 2002 Summer flounder 1 490 1375 1.32 0.03 U 0.00247 J 0.00662 J 0207096–001 DE Inland Bays 38°40′09.6″ −75°07′26.3″ 30 July 2002 Atlantic croaker 1 333 535 0.80 0.03 U 0.00344 J 0.0570 J 0207096–002 DE Inland Bays 38°40′09.6″ −75°07′26.3″ 30 July 2002 Atlantic croaker 1 346 450 0.48 0.00057 J 0.01 U 0.0286 J 0207096–003 DE Inland Bays 38°40′09.6″ −75°07′26.3″ 30 July 2002 Atlantic croaker 1 337 600 0.79 0.03 U 0.00289 J 0.0412 0207096–004 DE Inland Bays 38°40′09.6″ −75°07′26.3″ 30 July 2002 Atlantic croaker 1 315 640 0.80 0.03 U 0.01 U 0.0643 0207096–005 DE Inland Bays 38°40′09.6″ −75°07′26.3″ 30 July 2002 Atlantic croaker 1 328 550 0.03 U 0.01 U 0.0573 0207064–001 DE Inland Bays 38°38′10.3″ −75°06′03.5″ 15 July 2002 Hard clam 35 69 28 0.93 0.00898 0.01 U 0.268 0207092–001 DE Inland Bays 38°36′03.0″ −75°07′33.0″ 29 July 2002 Hard clam 20 65 18 1.53 0.02009 0.00294 J 0.528 0203029–001 DE Estuary 38°59′57.4″ −75°18′57.6″ 21 March 2002 Striped bass 1 665 2850 2.19 0.03 U 0.01 U 0.00757 J 0203029–002 DE Estuary 38°59′57.4″ −75°18′57.6″ 21 March 2002 Striped bass 1 684 3000 1.23 0.03 U 0.00323 J 0.0182 J 0203029–003 DE Estuary 38°59′57.4″ −75°18′57.6″ 21 March 2002 Striped bass 1 662 2900 1.07 0.03 U 0.00276 J 0.0111 J 0203029–004 DE Estuary 38°59′57.4″ −75°18′57.6″ 21 March 2002 Striped bass 1 671 2750 1.17 0.03 U 0.00342 J 0.0243 J 0203029–005 DE Estuary 38°59′57.4″ −75°18′57.6″ 21 March 2002 Striped bass 1 626 2550 1.10 0.03 U 0.00352 J 0.0249 J 0205026–001 DE Estuary 39°44′30.6″ −75°29′44.7″ 8 May 2002 Striped bass 1 666 3390 0.88 0.03 U 0.00432 J 0.0243 J 0205053–001 DE Estuary 39°44′30.6″ −75°29′44.7″ 22 May 2002 Striped bass 1 666 2722 0.92 0.00168 J 0.01 U 0.0146 J 0205053–002 DE Estuary 39°44′30.6″ −75°29′44.7″ 22 May 2002 Striped bass 1 615 2268 1.58 0.03 U 0.00228 J 0.0310 J 0205053–003 DE Estuary 39°44′30.6″ −75°29′44.7″ 22 May 2002 Striped bass 1 605 2313 0.66 0.03 U 0.00255 J 0.04 U 0205053–004 DE Estuary 39°44′30.6″ −75°29′44.7″ 22 May 2002 Striped bass 1 657 2631 0.36 0.03 U 0.00245 J 0.0129 J Detection limit 0.04 0.03 0.01 0.04 a Inorganic arsenic data are blank corrected. Fish samples were analyzed as skin-on fillets. Hard clam was analyzed as edible meats. DE = Delaware; MMA = monomethylarsonic acid; DMA = dimethylarsinic acid; J = detected above blank and less than the method detection limit; U = not detected. b Summer flounder, Paralicthys dentatus; Atlantic croaker, Micropogonias undulates; hard clam, Mercenaria mercenaria; striped bass, Marone saxatilis. RESULTS AND DISCUSSION Table 3 provides a description of the 2002 field samples along with the total and speciated arsenic results. Total arsenic was measured above a detection limit of 0.04 μg/g in all 27 field samples. Overall, the concentrations of total arsenic found in the present study were similar to the baseline data appearing in Table 1. The nominal ordering of total arsenic concentrations among the species tested in the present study was as follows: Summer flounder (incoming), summer flounder (outgoing), hard clam, striped bass (bay), striped bass (flats), and Atlantic croaker. This ordering, along with the center and spread in the total arsenic data, is shown in Figure 2. To our knowledge, the arsenic speciation results shown in Table 3 are the 1st such data to appear in the literature for marine fish and shellfish collected from Mid-Atlantic coastal waters. Table 4 presents the detection frequencies for the various forms of arsenic in the field samples, and Table 5 presents summary statistics for total arsenic and DMA in the field samples. Table 5 also presents summary statistics for inorganic arsenic in hard clam and MMA in striped bass. Summary statistics are not presented for inorganic arsenic in species other than hard clam or for MMA in species other than striped bass because of the low frequency of detection for such cases. For the purposes of Table 5, in the few cases when nondetections were involved, true values were assumed to be present at one-half the detection limit. Total arsenic in summer flounder Total arsenic in the incoming flounder spanned from a minimum of 1.8 μg/g ww to a maximum of 3.33 μg/g ww. In the outgoing flounder, total arsenic ranged from a minimum of 0.95 μg/g ww to a maximum of 2.13 μg/g ww. The median total arsenic concentration in the incoming flounder, 2.58 μg/g ww, is statistically greater than the median concentration in the outgoing flounder, 1.49 μg/g ww (Mann-Whitney, p = 0.0367). This difference was not related to differences in length between the incoming and outgoing fish. Although the incoming flounder as a group were slightly longer than the outgoing flounder (median total length: incoming flounder, 475 mm; outgoing flounder, 445 mm), this difference was not statistically significant (Mann-Whitney, p = 0.3457). Furthermore, no underlying statistically significant relationship was found between individual lengths of flounder and individual total arsenic concentrations (ANOVA, p = 0.6315). We therefore conclude that the arsenic concentration in the incoming flounder is, indeed, greater than that in the outgoing flounder and that this difference is not explained by differences in length. To provide broader regional context for the summer flounder data collected in the present study, we compared our results to summer flounder data collected approximately 200 km to the north in the New York Bight Apex. Scientists from the National Oceanic and Atmospheric Administration reported an average total arsenic concentration of 1.72 μg/g ww in 14 summer flounder fillet samples collected in September 1993 (Deshpande et al. 2000). The raw data of those authors indicate a minimum, maximum, and median of 1.22, 2.34, and 1.61 μg/g ww, respectively, for total arsenic. These values are similar to the results of the summer flounder samples collected from the Delaware Inland Bays in the fall of 2002 (outbound fish). However, the concentrations in the 1993 New York Bight samples are nominally lower than those in the summer flounder samples collected from the Delaware Inland Bays in the spring of 2002 (inbound fish). Total arsenic in striped bass, Atlantic croaker, and hard clam For striped bass, the total arsenic concentration in the fish collected from the Delaware Bay ranged from 1.07 to 2.19 μg/g ww, with a median of 1.17 μg/g ww. In comparison, the total arsenic concentration in the striped bass collected upstream at the Cherry Island Flats ranged from 0.36 to 1.58 μg/g ww, with a median of 0.88 μg/g ww. The median concentration in the Delaware Bay fish was greater than the median concentration in the fish from the Cherry Island Flats when viewed at the 90% confidence level but not when viewed at the 95% confidence level (Mann-Whitney, p = 0.0947). Median lengths between the 2 striped bass groups were not different (Mann-Whitney, p = 0.2948), and no underlying statistically significant relationship was found between total arsenic and length among individual striped bass (ANOVA, p = 0.7623). Total arsenic in the 5 Atlantic croaker samples ranged from 0.48 to 0.8 μg/g ww, with a median of 0.79 μg/g ww. No statistically significant relationship was found between length and total arsenic for croaker (ANOVA, p = 0.3554). The range of total arsenic in the 5 croaker samples from the Inland Bays was within the range of 0 to 2.1 μg/g ww reported by the USEPA for Atlantic croaker samples collected from the Louisianian Province (Summers et al. 1992). Finally, total arsenic in the 2 hard clam samples collected from the Inland Bays was 0.93 and 1.53 μg/g ww, with a median of 1.23 μg/g ww. MMA and DMA Monomethylarsonic acid was detected in 17 of the 27 samples, for an overall detection frequency of 63%. All 17 detections were "J" qualified. The minimum detected MMA concentration was 0.00115 μg/g ww, and the maximum was 0.00432 μg/g ww. The trimmed mean MMA concentration in the incoming flounder was 0.00229 μg/g ww, whereas that for the outgoing flounder was nearly equal at 0.00233 μg/g ww. The trimmed means for the striped bass samples were 0.00323 μg/g ww for the samples collected from the Delaware Bay and 0.0029 μg/g ww for the striped bass collected farther up estuary near the Cherry Island Flats. No significant relationship was found between MMA and fish length. Dimethylarsinic acid was detected in 26 of the 27 samples, for an overall detection frequency of 96%. All 10 detections in summer flounder and all 9 detections in striped bass were "J" qualified. In contrast, only 1 of the 5 croaker detections was "J" qualified, and neither of the detections in clam were "J" qualified. The peak DMA concentration, 0.528 μg/g ww, was found in 1 of the hard clam samples. The median for the 2 clam samples, 0.398 μg/g ww, was much greater than any of the other species tested. Croaker had the 2nd highest median DMA concentration at 0.057 μg/g ww. The median DMA concentration in the incoming flounder, 0.0079 μg/g ww, was not statistically different than the median in the outgoing flounder at 0.0066 μg/g ww (Mann-Whitney, p — 0.83). Similarly, the median DMA concentration in the striped bass collected from Delaware Bay, 0.018 μg/g ww, was not significantly different from the median in the striped bass collected near the Cherry Island Flats at 20 μg/kg (Mann-Whitney, p = 0.60). Dimethylarsinic acid was not related to length for flounder or striped bass; however, DMA did show a strong inverse relationship to length for croaker (ANOVA, p = 0.0294, R2 = 83.7%). Figure Figure 2.Open in figure viewerPowerPoint Variation in total arsenic concentration in selected marine fish and shellfish species from the Mid-Atlantic region, USA. With regard to the DMA levels in the hard clam and croaker samples, it is important to note that samples for both species were collected within 2 weeks of each other in the middle of the summer (15 July 2002 to 30 July 2002). It is postulated that the appearance of DMA in these species is related to arsenic transformations that occur in phytoplankton during this time period, coupled with attendant food-chain exposure. It is recognized that phytoplankton take up arsenate from aqueous solution, reduce the arsenate to arsenite, and methylate the arsenite to produce MMA and DMA, which are then excreted (Phillips 1990; Neff 1997). Recently, Hellweger and Lall (2004) successfully modeled the time course of this transformation by showing the gradual appearance of DMA during the summer period, when algal growth rates slow under phosphorus-limiting conditi