Levels of mercury in alligators (Alligator mississippiensis) collected along a transect through the Florida Everglades

Rumbold, Darren G.; Fink, Larry; Laine, Krysten; Niemczyk, Sharon; Chandrasekhar, T.; Wankel, Scott D.; Kendall, C.

doi:10.1016/s0048-9697(02)00132-8

Cited by 49 publications

(26 citation statements)

References 12 publications

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“…Symptoms of physiological or nutritional stress may be exacerbated by ingested Pb in animals with lesser degrees of tolerance, and drought conditions have been shown to enhance the negative effects of heavy metals on wildlife (Rumbold et al 2002). Future Nile crocodile research efforts in Africa would benefit from including BPb monitoring as part of standard protocol, especially in habitats where recreational fishing occurs.…”

Section: Discussionmentioning

confidence: 99%

Blood lead concentrations in free-ranging Nile crocodiles (Crocodylus niloticus) from South Africa

et al. 2016

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Generally crocodilians have received little attention with regard to the effects of lead toxicity despite their trophic status as apex, generalist predators that utilize both aquatic and terrestrial habitats, thereby exposing them to a potentially wide range of environmental contaminants. During July-October 2010 we collected whole blood from 34 sub-adult and adult free-ranging Nile crocodiles (Crocodylus niloticus) from three separate populations in northeastern South Africa in order to analyze their blood lead concentrations (BPb). Concentrations ranged from below detectability (<3 μg/dL, n = 8) to 960 μg/dL for an adult male at the Lake St Lucia Estuary. Blood lead concentrations averaged 8.15 μg/dL (SD = 7.47) for females and 98.10 μg/dL (SD = 217.42) for males. Eighteen individuals (53 %) had elevated BPbs (≥10 μg/dL). We assessed 12 general linear models using Akaike's Information Criterion (AIC) and found no significant statistical effects among the parameters of sex, crocodile size and population sampled. On average, crocodiles had higher BPbs at Lake St Lucia than at Ndumo Game Reserve or Kosi Bay, which we attribute to lead sinker ingestion during normal gastrolith acquisition. No clinical effects of lead toxicosis were observed in these crocodiles, even though the highest concentration (960 μg/dL) we report represents the most elevated BPb recorded to date for a free-ranging vertebrate. Although we suggest adult Nile crocodiles are likely tolerant of elevated Pb body burdens, experimental studies on other crocodilian species suggest the BPb levels reported here may have harmful or fatal effects to egg development and hatchling health. In light of recent Nile crocodile nesting declines in South Africa we urge further BPb monitoring and ecotoxicology research on reproductive females and embryos.

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Section: Discussionmentioning

confidence: 99%

Blood lead concentrations in free-ranging Nile crocodiles (Crocodylus niloticus) from South Africa

et al. 2016

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“…For example, largemouth bass and spotted gar were found to feed as tertiary consumers in a previous study at Caddo Lake [24]. However, the relatively low trophic position of alligators (<2.5) was surprising, because these reptiles are generally assumed to be the top predators in the ecosystems that they inhabit [52]. This low trophic position suggests that the diet of the individuals sampled in the present study (one juvenile, one subadult) consisted largely of organisms that occupy lower trophic positions.…”

Section: Trophic Position Of Caddo Lake Biotamentioning

confidence: 96%

Mercury speciation and biomagnification in the food web of Caddo Lake, Texas and Louisiana, USA, a subtropical freshwater ecosystem

Chumchal

Rainwater

Osborn

et al. 2011

Enviro Toxic and Chemistry

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We studied the biomagnification of total mercury and methylmercury in a subtropical freshwater lake, Caddo Lake, Texas and Louisiana, USA. The present study is unique in that it not only included invertebrates (seven species) and fish (six species) but also an amphibian (one species), reptiles (three species), and mammals (three species). Nonfish vertebrates such as those included in the present study are often not included in assessments of trophic transfer of Hg. Mean trophic position (determined using stable isotopes of nitrogen) ranged from 2.0 (indicative of a primary consumer) to 3.8 (indicative of a tertiary consumer). Mean total Hg concentrations ranged from 36 to 3,292 ng/g dry weight in muscle and whole body and from 150 to 30,171 ng/g dry weight in liver. Most of the Hg in muscle and whole-body tissue was found as methylmercury, and at least 50% of the Hg found in liver was in the inorganic form (with the exception of largemouth bass, Micropterus salmoides). Mercury concentrations were positively correlated with trophic position, indicating that biomagnification occurs in the food web of Caddo Lake. The food web magnification factors (FWMFs; slope of the relationship between mean Hg concentration and trophic position) for both total Hg and methylmercury were similar to those observed in other studies. Because most of the total Hg in consumers was methylmercury, the FWMF for methylmercury was not significantly different from the FWMF for total Hg. Some vertebrates examined in the present study had low Hg concentrations in their tissues similar to those observed in invertebrates, whereas others had concentrations of Hg in their tissues that in previous studies have been associated with negative health consequences in fish.

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“…The feeding activity of this species in the Pantanal region is governed by its habitat instead of its size (Santos 1997). Studies found a positive correlation between Hg concentration and size in Alligator mississippiensis (Burger et al 2000;Rumbold et al 2002), but other studies found no relationship between these two variables (Elsey et al 1999;Jagoe et al 1998;Ruckel 1993). Yanochko et al (1997) found a positive correlation in A. mississippiensis from Florida but no correlations in the ones from Par Pond, South Carolina.…”

Section: Hg Concentration Versus Caiman Size and Sexmentioning

confidence: 97%

“…Heaton-Jones et al (1997) evaluated histopathological material from farm-raised and wild-caught alligators from the Florida Everglades, which included some of the highest Hg levels reported to date (Rumbold et al 2002). However, no evidence of nerurologic, hepatic, or renal toxicosis was observed.…”

Section: Health Risk To Caimans Themselvesmentioning

confidence: 99%

Mercury Concentration in the Spectacled Caiman and Black Caiman (Alligatoridae) of the Amazon: Implications for Human Health

Schneider

Peleja

Junior

et al. 2012

Arch Environ Contam Toxicol

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Mercury (Hg) concentrations in the Amazon are generally high, but no studies have been published on Hg concentrations in caimans (Alligatoridae) from the region. Aiming for sizes representative of caimans traded for food in the Amazon, we measured Hg concentration in tail muscle of spectacled caiman (Caiman crocodilus crocodilus) and black caiman (Melanosuchus niger) from the Purus River basin. The information on Hg concentration in caimans from this area is important because of the potential health risk to humans and other animals that eat them as well as the potential use of these top-level predators as bioindicators. There were no significant interspecific or sex differences in Hg concentrations. The mean Hg concentration was 291.2 μg/kg in C. c. crocodilus and 193.9 μg/kg in M. niger. A significant positive correlation between Hg concentration and size was found for M. niger (p = 0.005) but not for C. c. crocodilus. Our Hg sample from M. niger corresponded to the size of M. niger collected for commercial trade, but our Hg sample from C. c. crocodilus turned out to be significantly smaller than the trade samples (p = 0.004), but this difference is not pertinent in the absence of a correlation between size and Hg concentration for this species. Although there are no standards for reptile meat, both species had mean Hg concentrations lower than the maximum allowable level of 500 μg/kg Hg recommended by the World Health Organization and by the Brazilian Health Ministry for fish. However, by calculating daily consumptions limits and number of meals per month that can be safely consumed, we found that consumers who eat caimans frequently may be at risk for Hg-related health problems.

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Levels of mercury in alligators (Alligator mississippiensis) collected along a transect through the Florida Everglades

Cited by 49 publications

References 12 publications

Blood lead concentrations in free-ranging Nile crocodiles (Crocodylus niloticus) from South Africa

Blood lead concentrations in free-ranging Nile crocodiles (Crocodylus niloticus) from South Africa

Mercury speciation and biomagnification in the food web of Caddo Lake, Texas and Louisiana, USA, a subtropical freshwater ecosystem

Mercury Concentration in the Spectacled Caiman and Black Caiman (Alligatoridae) of the Amazon: Implications for Human Health

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