Metal Levels in Delaware Bay Horseshoe Crab Eggs from the Surface Reflect Metals in Egg Clutches Laid beneath the Sand

The influence of tissue morphometry on tissue mercury concentration in male and female virile crayfish (Faxonius virilis)

The objective of this study was to determine the influence of tissue morphometry on tissue total mercury concentration (THg) in male and female virile crayfish (Faxonius virilis). In 2023, 10 embryonized and nine stage IV female crayfish and 29 male virile crayfish were captured from Lake Roosevelt and the Spokane River Arm, in Washington, USA. Total mercury was analyzed in the adductor muscle, gills, and hepatopancreas for all individuals and the ovaries and eggs for females with developed ovaries and embryonized females, respectively. Tissue morphometrics and tissue THg were allometrically correlated to the clawless body mass of male virile crayfish. Furthermore, it was determined that in male size-adjusted virile crayfish, gill THg was significantly associated with hepatopancreas THg but not adductor muscle THg. In embryonized and reproductive developing female virile crayfish, there was evidence of considerable adductor muscle and hepatopancreas tissue atrophy; however, no significant differences in THg occurred. In both the adductor muscle and the hepatopancreas, THg was not bioamplified despite tissue atrophy, suggesting a net loss of mercury from the tissues into the hemolymph. Although the most plausible redistribution of mercury in females with developed ovaries would be from the hepatopancreas to the developing ovary, this redistribution does not completely explain the level of maternal transfer observed. Clearly, dietary mercury contributed to the body burden of mercury within the ovaries of the females in reproductive development.

Histopathological and histochemical analysis of the digestive tract of adult horseshoe crabs under mercury stress

Mercury (Hg) contamination is a major environmental concern that continuously impacts marine organisms, including the mangrove horseshoe crab (Carcinoscorpius rotundicauda). As a vulnerable species, C. rotundicauda holds significant ecological and evolutionary value, making it particularly susceptible to Hg pollution and deserving of focused conservation efforts. This study presents the first comprehensive histopathological and histochemical analysis of mercury toxicity in the digestive tract of adult C. rotundicauda. Through both qualitative and quantitative analyses of histopathological and histochemical alterations, we evaluated the effects of acute Hg exposure (0.5 mg/L and 5 mg/L) on the esophagus, stomach, and intestines over time. The results revealed significant dose- and time-dependent tissue damage, with the stomach exhibiting the most pronounced alterations, including epithelial detachment, vacuolation caused by fibers degradation in the loose connective tissue, and muscle layer disruption, followed by the esophagus and intestines. Additionally, mucous cell density in the hindgut submucosa decreased by 30 % after 96 h of acute Hg exposure (0.5 and 5 mg/L HgCl2), indicating a weakened protective barrier. The tissue damage of the digestive tract may further have a negative impact on the health of the adult horseshoe crab, thus threatening the survival of C. rotundicauda population and reducing the biodiversity of the mangrove ecosystem. These findings underscore the critical threat posed by Hg pollution to the digestive system of C. rotundicauda and offer novel insights into the toxicological impact on marine invertebrates. Considering the tissue-damaging effects of Hg on adult horseshoe crabs, this study underscores the importance of regular monitoring of Hg contamination in natural habitats. The results offer valuable guidance for future habitat restoration and effective management of existing habitats.

Trace element contamination in three shorebird species migrating through Delaware Bay, New Jersey: arsenic, mercury and selenium are increasing

Many shorebird populations are declining, and contaminants may be partly contributing to the decline by interfering with feeding, migration, and breeding success. The goal of our study was to determine whether there was a temporal change in concentrations of trace elements of red knot (Calidris canutus rufa), sanderling (Calidris alba), and ruddy turnstone (Arenaria interpres) during spring migration in Delaware Bay, New Jersey, USA. We sampled blood to 1) determine levels of trace elements in 2019, 2) compare 2019 trace element levels with those from shorebirds in 2011-2012, and 3) examine variability in blood levels of trace elements among species. In 2019: 1) trace element levels were significantly different among species (except cadmium[Cd]), 2) Cd was lowest in all species, and arsenic (As) and selenium (Se) were highest, and 3) sanderlings had the highest levels of As and Se, and knots had the highest levels of chromium (Cr) and lead (Pb). Se was higher in these shorebirds than reported for other shorebirds from elsewhere. As, mercury (Hg), and Se increased significantly between 2011-2012 and 2019 in all three species. There were no significant temporal changes in Cd. Chromium (Cr) decreased in knots and sanderling. The temporal increases in As, Se, and Hg bear watching as they are toxic in vertebrates, and each can decrease the toxicity of the others. The data indicate that shorebirds can be bioindicators of changing trace element levels in estuaries, potentially providing early warning of increasing levels of As, Hg, and Se in the environment.

Bioaccumulation of Some Metals and Metalloids in Laughing Gulls (Leucophaeus atricilla): Increases in Mercury and Decreases in Selenium from 2019 to 2022/2023

The elements in blood normally reflect the levels in prey, indicating a recent exposure. Laughing gulls (Leucophaes atricilla) eat mainly horseshoe crab eggs (Limulus polyphemus) in the spring in Delaware Bay, New Jersey. The levels of arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and selenium (Se) in the blood of laughing gulls foraging on crab eggs were examined in Delaware Bay to provide information on a species that is normally a generalist, and to determine if the levels of these elements were similar in 2019 and 2022/2023, were intercorrelated, and were related to those in crab eggs. Hg increased from 2019 (136 ± 31 ng/g) to 2022/2023 (473 ± 75 ng/g), while Cd and Se decreased. There were some significant correlations among elements and a close relationship between the element levels in blood and those in crab eggs collected in the same month (except for As). The levels differed between laughing gulls and three species of shorebirds for As and Cd. The elements in the blood of gulls and shorebirds should be similar because they eat mainly the same eggs in the same places. A significant proportion of laughing gull blood samples had levels of Hg and Se that were above the levels associated with adverse effects, which requires further examination.

Some metals and metalloids in the blood of three species of shorebirds increase while foraging during two-week migratory stopover in Delaware Bay, New Jersey

Most migratory shorebird species are declining, some are endangered, and some may be vulnerable to contaminants on long distance travel between wintering grounds and high latitude breeding grounds. We examined whether shorebirds accumulated trace elements at the Delaware Bay (New Jersey) stopover by testing the null hypothesis that there was no difference in the levels of arsenic, cadmium, chromium, lead, mercury, and selenium in blood of three species of shorebirds collected early in their stopover compared to levels in blood collected about two weeks later near the end of the stopover, before departing for breeding grounds. There were significantly higher levels of all metals and metalloids in the blood of ruddy turnstone (Arenaria interpres) later in May than earlier. There were seasonal increases in blood levels of arsenic and selenium for all three species. Chromium and lead levels also increased in red knots (Calidris canutus). These increases occurred although the birds were only present for about two weeks. Levels of arsenic, mercury, and lead in knots and selenium in sanderlings (Calidrris alba), exceeded reported effects levels. These results have potential implications for studying the refueling physiology, energetics, and feeding behavior of migratory shorebirds. However, they also suggest cause for concern because the increased contaminant loads occur in a short period, and the high metal level bolus received all in a few days may result in adverse effects.