Mercury biomagnification and the trophic structure of the ichthyofauna from a remote lake in the Brazilian Amazon.

The present study assesses mercury biomagnification and the trophic structure of the ichthyofauna from the Puruzinho Lake, Brazilian Amazon. In addition to mercury determination, the investigation comprised the calculation of Trophic Magnification Factor (TMF) and Trophic Magnification Slope (TMS), through the measurements of stable isotopes of carbon (δ13C) and nitrogen (δ15N) in fish samples. These assessments were executed in two different scenarios, i.e., considering (1) all fish species or (2) only the resident fish (excluding the migratory species). Bottom litter, superficial sediment and seston were the sources used for generating the trophic position (TP) data used in the calculation of the TMF. Samples from 84 fish were analysed, comprising 13 species, which were categorized into four trophic guilds: iliophagous, planktivorous, omnivorous and piscivorous fish. The δ13C values pointed to the separation of the ichthyofauna into two groups. One group comprised iliophagous and planktivorous species, which are linked to the food chains of phytoplankton and detritus. The other group was composed by omnivorous and piscivorous fish, which are associated to the trophic webs of phytoplankton, bottom litter, detritus, periphyton, as well as to food chains of igapó (blackwater-flooded Amazonian forests). The TP values suggest that the ichthyofauna from the Puruzinho Lake is part of a short food web, with three well-characterized trophic levels. Mercury concentrations and δ13C values point to multiple sources for Hg input and transfer. The similarity in Hg levels and TP values between piscivorous and planktivorous fish suggests a comparable efficiency for the transfer of this metal through pelagic and littoral food chains. Regarding the two abovementioned scenarios, i.e., considering (1) the entire ichthyofauna and (2) only the resident species, the TMF values were 5.25 and 4.49, as well as the TMS values were 0.21 and 0.19, respectively. These findings confirm that Hg biomagnifies through the food web of Puruzinho Lake ichthyofauna. The migratory species did not significantly change mercury biomagnification rate in Puruzinho Lake; however, they may play a relevant role in Hg transport. The biomagnification rate (TMS value) in Puruzinho Lake was higher than the average values for its latitude, being comparable to TMS values of temperate and polar systems (marine and freshwater environments).

Organochlorine concentrations (PCBs, DDTs, HCHs, HCB and MIREX) in delphinids stranded at the northeastern Brazil.

Organochlorine compounds are highly persistent in the environment, causing bioaccumulation and biomagnification through the marine food chain. To verify the bioaccumulation pattern of DDT and its metabolites, as well as PCBs, Mirex, HCHs and HCB, samples of subcutaneous adipose tissue from 25 Guiana dolphins (Sotalia guianensis), two Fraser's dolphins (Lagenodelphis hosei), two spinner dolphins (Stenella longirostris), one spotted dolphin (Stenella frontalis), and one striped dolphin (Stenella coeruleoalba) were analyzed. The collected specimens were found stranded in northeastern Brazil between 2005 and 2011. The concentrations were reported in µg·g(-1) lip, varying from 0.02 to 17.3 for ΣPCB, from 0.003 to 5.19 for ΣDDT, from 0.005 to 0.16 for ΣHCH, from 0.002 to 0.16 for HCB, and from 0.02 to 2.38 for Mirex. The PCBs dominated the bioaccumulation pattern for both the Guiana and spinner dolphins; for the other species, DDT was the major compound. A discriminant function analysis revealed the differences in the organochlorine accumulation patterns between the Guiana dolphin (S. guianensis) and the continental shelf/oceanic dolphins (S. frontalis and S. longirostris). The results also show that the concentrations of organochlorine compounds found in the delphinids in northeastern Brazil were lower than the delphinids found in other regions of Brazil, as well as other locations worldwide with intense agroindustrial development and/or a larger population.

Organochlorine concentrations in franciscana dolphins, Pontoporia blainvillei, from Brazilian waters.

Blubber samples were collected from ten franciscana dolphins either incidentally captured in fishing operations or stranded on São Paulo (SP) and Paraná (PR) states littoral, Southeastern and Southern Brazilian coast, respectively. Determination of PCB, DDT and HCB concentrations were performed by capillary gas chromatograph coupled to electron capture detector (ECD). ΣDDT, ΣPCB and HCB concentrations ranged from 264 ng g(-1) to 5811 ng g(-1) lipid, from 909 ng g(-1) to 5849 ng g(-1) lipid and from 10 ng g(-1) to 61 ng g(-1) lipid, respectively. Regarding DDTs, the distribution of the mean percentages decreased in the following order: p,p'-DDE>p,p'-DDD>p,p'-DDT. The ΣDDT/ΣPCB ratio varied between 0.27 and 0.42 in Northern and Central SP coast, while in Southern SP and PR coast the values were 1.6 and 1.9, respectively. Dissimilarities in ΣDDT/ΣPCB ratios point to different sources of organochlorine compounds to franciscana dolphins in the study area. Considering the endocrine disruptive action of organochlorine compounds, the concentrations found in franciscana dolphins from Brazilian waters may represent an additional obstacle to the conservation of this endangered cetacean species.