Michael Zuykov

Bivalve mollusks in metal pollution studies: from bioaccumulation to biomonitoring.

Contemporary environmental challenges have emphasized the need to critically assess the use of bivalve mollusks in chemical monitoring (identification and quantification of pollutants) and biomonitoring (estimation of environmental quality). Many authors, however, have considered these approaches within a single context, i.e., as a means of chemical (e.g. metal) monitoring. Bivalves are able to accumulate substantial amounts of metals from ambient water, but evidence for the drastic effects of accumulated metals (e.g. as a TBT-induced shell deformation and imposex) on the health of bivalves has not been documented. Metal bioaccumulation is a key tool in biomonitoring; bioavailability, bioaccumulation, and toxicity of various metals in relation to bivalves are described in some detail including the development of biodynamic metal bioaccumulation model. Measuring metal in the whole-body or the tissue of bivalves themselves does not accurately represent true contamination levels in the environment; these data are critical for our understanding of contaminant trends at sampling sites. Only rarely has metal bioaccumulation been considered in combination with data on metal concentrations in parts of the ecosystem, observation of biomarkers and environmental parameters. Sclerochemistry is in its infancy and cannot be reliably used to provide insights into the pollution history recorded in shells. Alteration processes and mineral crystallization on the inner shell surface are presented here as a perspective tool for environmental studies.

Alteration of shell nacre micromorphology in blue mussel Mytilus edulis after exposure to free-ionic silver and silver nanoparticles

This study describes the morphology of inner shell surface (ISS) of the blue mussel Mytilus edulis Linnaeus after short-term exposures to radiolabeled silver in free-ionic ((110m)Ag(+)) and engineered nanoparticulate ((110m)AgNPs, <40 nm) phases. Radiolabeled silver in starting solutions was used in a similar low concentration (∼15 Bq mL(-1)) for both treatments. After exposure experiments radiolabeled silver was leached from the ISS using HCl. It concentration for shells from both treatments was ∼0.5 Bq mL(-1). Whole ISS of young individuals and prismatic layer of adults showed no evidence of any major alteration process after silver uptake. However, the nacre portion of adult mussels exposed to both treatments revealed distinct doughnut shape structures (DSS) formed by calcium carbonate micrograins that covered the surface of aragonite tablets. Scanning electron microscope (SEM) imaging revealed the existence of only minor differences in DSS morphology between mussels exposed to Ag(+) and AgNPs. From literature survey, DSS were also found in bivalves exposed to Cd(2+). The DSS occurring in a specimen of a field-collected bivalve is also shown. Formation of distinctive DSS can be explained by a disturbance of the shell calcification mechanism. Although the occurrence of DSS is not exclusively associated with metal bioavailability to the mussels, the morphology of DSS seems to be linked to the speciation of the metal used in the uptake experiments.

First record of the green microalgae Coccomyxa sp. in blue mussel Mytilus edulis (L.) from the Lower St. Lawrence Estuary (Québec, Canada)

During autumn 2012 and spring 2013, blue mussels Mytilus edulis (L.) with strongly deformed (L-shaped) posterior shell margins and green spots in soft tissue (microalgae) were collected from intertidal zone along the south shore of the Lower St. Lawrence Estuary near Rimouski (Québec, Canada). Identification of algal cells infesting mussels as Coccomyxa sp. was confirmed by rRNA sequencing and HPLC pigment analysis. Flow cytometric analysis revealed the presence of algal cells in the hemolymph and extrapallial fluid in mussels with deformed and non-deformed shells; concentrations of algal cells were ranged from about 200mL(-1) in mussels with actually non-deformed shells to concentrations reaching up to 3.8×10(7)mL(-1) in mussels with heavily deformed ones. Chemical analyses of soft tissues led us to conclude that butyltin compounds and trace metals cannot be considered among factors responsible for the shell deformity observed. Using scanning electron microscopy, the biogenic nature of the erosion on the external shell surface and aragonitic lenses of prisms in the curvature zone of deformed shells (in sections) were recorded. The sequence of the green algae from M. edulis of the Lower St. Lawrence Estuary was closely related to Coccomyxa sp. infecting M. edulis from the Flensburg Fjord (North Sea) and Modiolus modiolus (L.) from the Vityaz Bay (Sea of Japan).

Glyptorthis (Foerste, 1914) and Bassettella New Genus (Brachiopoda: Orthida) from the Late Ordovician of the East Baltic

The genus Glyptorthis Foerste, 1914 is a rare component of the Late Ordovician to early Silurian brachiopod faunas of the East Baltic. Hints and Roomusoks (1997) reported on the occurrence of Glyptorthis in seven stratigraphic levels within the Upper Caradoc, Ashgill and Llandovery, in a paper summarizing the stratigraphy of Estonia. To date, however, very few of these brachiopods have been studied in detail. Three species from the Ashgill and Llandovery were established by Rubel (1962) and Roomusoks (1970), whereas some unnamed Caradoc taxa were listed only in the latter paper. Collections made since 1987 by S. S. Terentiev and M. A. Zuykov revealed that rare specimens of Glyptorthis -like brachiopods occur in fossiliferous lower Caradocian (Idavere Regional Stage) strata in the western part of the St. Petersburg region, northwestern Russia. These specimens, assigned herein to a new glyptorthid genus and species Bassettella gracilis , comprise the core of this paper. Moreover, generic affinities of Estonian species from the Ashgill currently assigned to Glyptorthis are discussed. The type specimen of J. Hall (1847) in the American Museum of Natural History (New York) and specimens from the type area in the Schuchert Brachiopod Collection in the Peabody Museum of Natural History, Yale University (New Haven), have been investigated for comparative purposes. The brachiopods described here were collected from localities in NW Russia, Estonia, and North America (Fig. 1). The Bassettella gracilis n. gen. and sp. fossil localities from the St. Petersburg region (NW Russia) are given in Figure 1, as is a correlation chart with the Estonian stratigraphic position of B. gracilis .  Figure 1 —Locality map and stratigraphic ranges of Glyptorthis Foerste, 1914 and Bassettella new genus in the Upper Ordovician rocks of North Estonia and northwestern Russia (St. Petersburg region). 1, Korgessaare village in the Hiiumaa …

Biosorption of thorium on the external shell surface of bivalve mollusks: The role of shell surface microtopography

External shell surface (ESS) of bivalve mollusks is known to adsorb various metals dissolved in ambient water in high concentration. It is hypothesized here that the surface microtopography of the thin organic coating layer, periostracum, or calcareous shell (if periostracum was destroyed) plays a major role in the adsorption of actinides on ESS. Thorium (natural alpha-emitter) was used in short-term biosorption experiment with shell fragments of five bivalve mollusks. After a 72 h exposure to Th (~6 kBq L(-1)), thorium concentration was measured on ESS using laser ablation inductively coupled plasma mass spectrometry; the distribution and density of alpha tracks were subsequently visualized by α-track autoradiography. A trend in reduced Th concentrations on the ESS was observed depending upon the species tested: (group 1 ~4000 μg g(-1)) Chlamys islandica (M.), Mercenaria mercenaria (L.), Dreissena polymorpha (P.)>(group 2 ~1200 μg g(-1)) Crassostrea virginica (G.)≫(group 3 ~150 μg g(-1)) Mytilus edulis L. The microtopography of ESS was characterized by scanning electron microscopy revealing the high porosity of the calcareous surface of C. islandica and M. mercenaria, lamellate surface of periostracum in D. polymorpha, uneven but a weakly porous surface of periostracum of C. virginica, and a nearly smooth surface of the periostracum of M. edulis. This work has demonstrated, for the first time, the presence of a strong correlation between concentration of adsorbed Th and ESS microtopography, and the role of the periostracum in this process is discussed.

New endemic brachiopod and echinoderm genera from the Upper Ordovician of the St. Petersburg region, northwestern Russia

Abstract A new brachiopod and a rhombiferan cystoid are described from the Gryazno and Schundorovo formations (Upper Ordovician; middle Sandbian), Idavere Regional Stage, of the St. Petersburg Region (northwestern Russia). The fossils are part of an abundant, well-preserved benthic fauna. The rhynchonelliformean brachiopod Madiorthis alsami gen. et sp. nov. belongs to the family Plaesiomyidae (subfamily Plaesiomyinae); the dichoporite echinoderm Fusicystis magnificus gen. et sp. nov. is assigned to the family Echinoencrinitidae (subfamily Scoliocystinae). These new taxa have not been found outside the type locality.

Mytilus trossulus and hybrid (M. edulis-M. trossulus) - new hosts organisms for pathogenic microalgae Coccomyxa sp. from the Estuary and the northwestern Gulf of St. Lawrence, Canada

During summer 2014-2017, wild mytilid mussels, highly infested with the pathogenic Coccomyxa-like microalgae, were collected along the Estuary and northwestern part of Gulf of St. Lawrence (Québec, Canada). Molecular identification showed that algae can be assigned to a single taxon, Coccomyxa sp. (KJ372210), whereas hosts are represented by Mytilus edulis, M. trossulus and hybrid between these two species. This is the first record of M. trossulus and hybrid among hosts of this pathogenic alga. Our results are indicative of a possible widespread distribution of Coccomyxa sp. in the Lower St. Lawrence Estuary and along coastal waters of Canadian Maritime provinces.

Revision of the Ordovician Brachiopod Genus Noetlingia Hall and Clarke, 1893

Abstract The enigmatic pentameride brachiopod Noetlingia Hall and Clarke, 1893 is revised and its stratigraphic range corrected. The type species Noetlingia tscheffkini occurs only within the upper Darriwilian (Ordovician) of the East Baltic and not in the Silurian as previously assumed. Thus, presently defined, the superfamily Porambonitoidea does not cross the boundary between the Ordovician and Silurian systems. Two other species occurring in the Lower to Middle Ordovician of South China and North America are assigned to Noetlingia.