Evgueni Shumilin

Spatial and vertical distributions of elements in sediments of the Colorado River delta and upper Gulf of California

The abundance of major components (Fe, Ca, K, and organic carbon) and trace elements was analyzed in surface sediments and core samples from the Colorado River delta (CRD) and the Upper Gulf of California (UGC) using instrumental neutron activation analysis. The spatial distribution patterns of the elements studied are consistent with the model of sedimentary dynamics proposed for this area [Mar. Geol. 158 (1999) 125]: intense tidal resuspension of sediments in the delta with subsequent transport of suspended particulate matter in a southerly direction, followed by sedimentation of fine-grained material in a depocenter near the southwestern margin of the UGC. Concentrations of most of the elements are higher in the surface sediments of this depocenter. The gradual mixing of terrigenous and marine biogenic materials, normally expected for the estuarine sediments, was not detected in the CRD–UGC system because of homogenization of the sediments by tides and wind. Vertical profiles of element contents in samples of the sediment core collected in the depocenter area revealed (i) almost no anthropogenic contamination of the area by environmentally important trace elements such as Cr, Co, Sb, and As; (ii) a twofold decrease of Fe, Sc, Cr, and Co in upper core sediments; and (iii) the enrichment of the sediments at 60–62 cm depth in the core, in calcium carbonate, Ca, Sr, and the Eun/Smn shale-normalized ratio along with a depletion in this layer of Fe, Sc, Cr, Co, light rare-earth elements (REEs), and some other elements of terrigenous origin, presumably caused by the dilution of fluvial terrigenous material by biogenic carbonates, which were probably introduced at this level in the sediments by the action of a strong episodic winter storm, followed by the advective transport of shell fragments from the coastal clam banks or as a result of strong planktonic bloom. D 2002 Elsevier Science B.V. All rights reserved.

Element Concentrations in Some Species of Seaweeds from La Paz Bay and La Paz Lagoon, South-Western Baja California, Mexico

La Paz Bay and La Paz Lagoon are water bodies of the Gulf of California that are influenced by waste water discharges from the City of La Paz and from activities of the phosphorite mining company “Rofomex”. Because seaweeds concentrate elements from the water and are used as effective indicators of contamination by metals, we investigated their usefulness in this region. Concentrations of certain major elements (Ca, Fe, K and Na) and trace elements (As, Ba, Co, Cr, Cs, Hf, Rb, Sb, Sc, Se, Sr, Ta, Th, U, Zn and Zr) were determined in 12 species of seaweeds from La Paz Bay and La Paz Lagoon using instrumental neutron activation analysis. The contents of trace elements of environmental importance (As, Co, Cr, Fe, Sb, Se and Zn) in all studied samples are within the range of typical levels for a pristine environment not subjected to anthropogenic impact. Somewhat higher concentrations of Cr (81mg kg−1), Hf (4mg kg−1), Rb (48mg kg−1), Sc (6.3mg kg−1), Ta (0.95mg kg−1), Th (6.8mg kg−1), U (33mg kg−1) and Zn (90mg kg−1) were found in the green seaweed species Ulva (formerly Enteromorpha) intestinalis, whereas such elements as As (77mg kg−1), Sb (1.4mg kg−1) and Se (1.8mg kg−1) were mainly concentrated in the species Sargassum sinicola, Codium cuneatum and Padina mexicana respectively. Because of their higher abundance and heterogeneity in elemental composition the seaweeds species Ulva intestinalis and Caulerpa sertularioides seem to be more suitable for further biomonitoring of heavy metal pollution of the coastal waters in this zone.

Observations on trace element hypersaline geochemistry in surficial deposits of evaporation ponds of Exportadora de Sal, Guerrero Negro, Baja California Sur, México

Trace element concentrations were determined for 28 samples of surficial deposits collected over a salinity gradient of 39x to approximately 250xin evaporation ponds of a large industrial NaCl production facility located near Guerrero Negro (Peninsula of Baja California, Mexico). Grain size and lithology are used to describe the mixed chemical–detrital material. Major earth and trace elements in the sediments were measured by a combination of an inductively coupled plasma mass spectrometry (ICPMS) for As, Ba, Cd, Cu, Mg, Ni, Pb, U, and Zn, flame atomic absorption spectrophotometry for Al, Fe, and Mn, isotope dilution ICPMS for Hg, and instrumental neutron activation analysis (INAA) for Cs, Ca, Sr, Cr, Sb, and Sc. Changes in grain-size, mineralogy, and chemical composition suggest that suspended particulate matter supplied to the system, mainly by seawater pumped in from the adjacent Ojo de Liebre Lagoon, and to a smaller extent, carried into the ponds by wind from adjacent dunes and by wave-induced erosion of retaining dikes, dominates the sediment in the first two concentration ponds. Freshly deposited fine sediments in these ponds are enriched in organic matter, biogenic carbonates, Al, Fe, Mn, and most of the trace elements, and are similar to surface sediments of the adjacent lagoon. In ponds 3 and 4, intensive evaporationinduced precipitation of calcium and magnesium carbonates occurs causing scavenging of Al, Fe, Mn carried by colloidal particles. The sediment in ponds 4 and 5 includes a thick microbial mat layer, which is enriched in organic carbon, and the accumulation of As and Cd is observed there. In ponds 7 through 11, the deposits generally are low in organic matter and trace elements (except for Sb) and are formed by intensive gypsum and anhydrite precipitation, with an admixture of terrigeneous material in ponds 8–10 supplied by a dyke erosion or carried in with wind from adjacent sand dunes. D 2002 Elsevier Science B.V. All rights reserved.

High heat flow and ocean acidification at a nascent rift in the northern Gulf of California

The prevailing tectonic setting in the Gulf California suggests the presence of an undetermined number of short spreading centres with associated hydrothermal systems. However, to date, active seafloor spreading phenomena have been documented in only three of the eight tectonically active basins. Here we report heat flow values as high as 15,436 mW m−2 in two of the northernmost basins of the Gulf of California, providing evidence of intense hydrothermal activity associated with the transition from continental rifting to seafloor spreading. The mean heat flow for the Wagner and Consag basins area is 1,875 mW m−2, more than 15 times higher than the mean value for oceanic crust (105.4 mW m−2). Additional evidence for vigorous hydrothermal circulation and a shallow heat source includes intense gas discharge (CO2 and CH4), widespread low pH (average 7.7), locally high 222Rn concentrations in the bottom water and a high extent of organic matter maturation in the sediments.

Urban activity and mercury contamination in estuarine and marine sediments (Southern Brazil)

The distribution of mercury in sediments of the Patos Lagoon estuary and nearby coastal marine deposits has been investigated for the period 1998–2008. Polluted urban soils and coastal reclamation fills are the principal sources of high mercury concentrations for shallow estuarine sediments. The shallow sediments that form near the urban area enter the navigation canal and are transported into the ocean. The mercury concentration in sediments of the navigation canal has considerably increased since 2004, due to intense reconstruction activity in the urban area. Periodic dredging of the canal strengthens the preconditions for coastal marine sediment contamination by mercury. However, this does not occur because the resuspended dredged sediments are significantly diluted by natural suspended particulate matter.

Bioaccumulation and biomagnification of potentially toxic elements in the octopus Octopus hubbsorum from the Gulf of California

The concentrations of 21 potentially toxic elements (PTEs) were determined in the tissues of Octopus hubbsorum from three locations along the Gulf of California coast: two near Santa Rosalia (SR), a site with historical metal contamination, and one in La Paz Bay, a reference site. Concentrations of Cd, Co, Cr, Mn, Ni, Pb, and Zn in octopus from the two SR sites were higher than those from the reference site, reflecting the higher sediment concentrations at the mining-impacted locations. The highest bioaccumulation and biomagnification of elements was found in digestive gland and branchial hearts, while the lowest was observed in the mantle, where the mean concentration of PTEs did not exceed international standards for human consumption of octopus. This study found elevated PTEs in octopus from sites with high metal contamination, and presents the first data on these elements in octopus from the Gulf of California.

Intertidal geothermal hot springs as a source of trace elements to the coastal zone: A case study from Bahía Concepción, Gulf of California

We investigated the influence of the intertidal geothermal hot spring (GHS) on the biogeochemistry of trace elements in Santispac Bight, Bahía Concepción (Gulf of California). The geothermal fluids were enriched in As and Hg mainly in ionic form. The suspended particulate matter of the GHS had elevated enrichment factor (EF) >1 of As, Bi, Cd, Co, Cu, Mn, Mo, Sb, Sn, Sr, Ti, U and Zn. The sediment core from GHS1 had high concentration of As, Hg, Corg, S, V, Mo, and U and the extremely high EF of these elements at 8cm of the core. The maximum bioaccumulation of As and Hg was in seaweeds Sargassum sinicola collected near the GHS2. The results confirm the input of trace elements to the coastal zone in Bahía Concepción from geothermal fluids and the evident modification of the chemical composition of the adjacent marine environment.

Abundance and distribution of benthic foraminifera as indicators of the quality of the sedimentary environment in a subtropical lagoon, Gulf of California

Abundance and spatial distribution of benthic foraminifera were used to evaluate the impacts of anthropogenic activities on sediment quality in a coastal lagoon in the Gulf of California. In 1985 and 2013, 27 samples of superficial sediments were collected. The foraminifera genera Ammonia, Cribroelphidium, Quinqueloculina and Peneroplis were dominant in both years. The abundance of Ammonia increased from 41% to 60%, while Peneroplis abundance decreased from a maximum of 50% in 1985 to 7% in 2013. The greater abundance of Ammonia and the greater spatial coverage of Ammonia and Cribroelphidium suggest a marked environmental deterioration in the quality of the sedimentary environment, which contrasts with studies of trace elements in the sediment of this lagoon. The Foram Stress Index indicates that sediment quality has deteriorated over time, likely due to the effects of anthropogenic activities around the lagoon.

Parasitic Castration of Chocolate Clam Megapitaria squalida (Sowerby, 1835) Caused by Trematode Larvae

ABSTRACT The prevalence of parasites in gonads of the clam Megapitaria squalida (Sowerby, 1835) was investigated at Santa Rosalía mining port in the Gulf of California. A total of 696 gonads were histologically analyzed, observing an unusual parasitic castration caused by the development of trematode larvae within follicles. Trematode sporocysts within follicles containing germinal balls and developing cercariae were observed and associated with an inflammatory response, as evidenced by a heavy hemocytic infiltration and the formation of granulocytomas surrounding the parasite structures. Some metacercariae were observed within ovarian connective tissues suggesting that M. squalida could also act as a second intermediate host for digenean trematodes. Infection was age specific as juvenile clams (1-4-cm shell length) did not contain parasites and prevalence in the adult clams increased with size. Unlike males, which presented four levels of infection density, all the parasitized ovaries of females showed very high infection densities. The prevalence was significantly (χ2 = 6.99; df = 1; P = 0.001) higher in females (30.2%) than in males (17%). The highest prevalence of parasitized clams was in the ripe stage during the summer (43.7%) when seawater temperatures were highest, whereas the lowest prevalences were observed in winter. It is possible that the polluted environment of Santa Rosalía could increase the occurrence and high infection density by trematode larvae in M. squalida.