Assessing the impact of imidacloprid, glyphosate, and their mixtures on multiple biomarkers in Corbicula largillierti.

Pesticide mixtures are frequently utilized in agriculture, yet their cumulative effects on aquatic organisms remain poorly understood. Aquatic animals can be effective bioindicators and invasive bivalves, owing to their widespread distribution, provide an opportunity to assess these impacts. Glyphosate and imidacloprid, among the most prevalent pesticides globally, are frequently detected in freshwater systems in South America. This study aims to understand the cumulative effects of pesticide mixtures on aquatic organisms, using invasive Corbicula largillierti clams from a natural stream in northwestern Argentina. We conducted 48-hour exposure experiments using two concentrations of imidacloprid (20 and 200 µg L-1 a.i), two concentrations of glyphosate (0.3 and 3 mg L-1 a.i), and two combinations of these pesticides (both at low and high concentrations, respectively), simulating the direct contamination of both pesticides based on their agronomic recipe and observed values in Argentine aquatic environments. Clam metabolism was assessed through the examination of multiple oxidative stress parameters and measuring oxygen consumption rate as a proxy for standard metabolic rate (SMR). Our findings revealed that imidacloprid has a more pronounced effect compared to glyphosate. Imidacloprid significantly decreased clam SMR and cellular levels of reduced glutathione (GSH). However, when both pesticides were present, also cellular glycogen and thiobarbituric acid-reactive substances (TBARS) were affected. Proteins and glutathione S-Transferase (GST) activity were unaffected by either pesticide or their mixture at the assayed concentrations, highlighting the need to test several stress parameters to detect toxicological impacts. Our results indicated additive effects of imidacloprid and glyphosate across all measured parameters. The combination of multiple physiological and cytological biomarkers in invasive bivalves offers significant potential to enhance biomonitoring sensitivity and obtain insights into the origins and cellular mechanisms of chemical impacts. These studies can improve pollution regulatory policies and pesticide management.

Resource partitioning of a Mexican clam in species-poor Baltic Sea sediments indicates the existence of a vacant trophic niche.

Invasive species are often generalists that can take advantage of formerly unexploited resources. The existence of such vacant niches is more likely in species-poor systems like the Baltic Sea. The suspension feeding wedge clam, Rangia cuneata, native to estuarine environments in the Gulf of Mexico, was sighted for the first time in the southeastern Baltic in 2010 and a few years later in the northern Baltic along the Swedish coast. To explore possible competition for food resources between R. cuneata and the three native clams inhabiting Baltic shallow soft bottoms, stable isotope and fatty acid analyses were conducted. There was no overlap between R. cuneata and any of the native species in either stable isotope or fatty acid niches. This suggests efficient partitioning of resources; multivariate analyses indicate that separation was driven mainly by δ13C and by fatty acids reflecting diatoms and cyanobacteria, respectively (e.g. 16:1ω7 and 18:3ω3). R. cuneata reflected seasonal variation in phytoplankton more than other clams reflecting higher trophic plasticity. In conclusion, the addition of R. cuneata to the Baltic shallow soft bottoms suggests the existence of a vacant trophic niche in these sediment habitats, however the long-term effects on other species and nutrient cycling requires further studies focusing on the population dynamics of R. cuneata and its impact on the Baltic Sea ecosystem.

Presence of Zonula Occludens Toxin-Coding Genes among Vibrio parahaemolyticus Isolates of Clinical and Environmental Origin.

In recent studies, emphasis has been placed on the zonula occludens toxin (Zot) from the non-toxigenic Vibrio parahaemolyticus strain PMC53.7 as an agent inducing alterations in the actin cytoskeleton of infected Caco-2 cells and which appears as a relevant virulence factor. Universal zot primers were designed by the alignment of different types of zot gene and identification of conserved sequences to investigate the presence in diverse environmental and clinical V. parahaemolyticus isolates, in co-occurrence with virulence factors, such a hemolysins and secretion systems. The study screened a total of 390 isolates from environmental sources from Chile and Italy and 95 Chilean clinical isolates. The results revealed that around 37.2% of Chilean environmental strains and 25.9% of Italian strains, and 24.2% of clinical isolates carried the zot gene. The Zot-C2 cluster was present in 71.4% of Chilean environmental strains but absent in clinical isolates, while the Zot-C4 cluster was identified in 28.6% of environmental and 100% of clinical isolates. Understanding the role of zot in V. parahaemolyticus virulence is crucial, especially considering the risk associated with consuming diverse isolates from bivalves and the co-occurrence with virulence factors such as TDH, TRH or T3SS2.

Spatial-temporal variations of metals and arsenic in sediments from the Doce River after the Fundão Dam rupture and their bioaccumulation in Corbicula fluminea.

The rupture of the Fundão dam in Brazil released tons of mining tailings into the Doce River Basin (DRB). This investigation aimed to determine the bioaccumulation of metals in soft tissues of the bivalve Corbicula fluminea exposed to sediments collected in the DRB in four periods (just after, 1, 3, and 3.5 years after the dam rupture). In the exposure bioassays, the concentrations of Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in sediments and bivalve soft tissues were quantified. The concentration of some elements (As, Cd, Mn, and Al) in sediments exceeded the federal limits or regional backgrounds at some sampling sites, but their concentrations tended to decrease over time. However, higher concentrations of many elements were detected in the winter of 2019. Several elements were detected in C. fluminea soft tissues, but the bioaccumulation factors were generally low or not related to those elements associated with the ore tailings, evidencing that the bioavailability of metals to bivalves, in laboratory conditions, was limited. Integr Environ Assess Manag 2024;20:87-98. © 2023 SETAC.

Combined effects of diesel and air exposure on oxidative stress parameters of mussels Perna perna (Mytilidae, Bivalvia).

This study aimed to assess the combined effect of hypoxia and exposure to diesel on biochemical parameters of Perna perna mussels. Mussels previously kept for 48 h in clean seawater were submitted to hypoxia for 24 h followed by reoxygenation in clean seawater for 48 h. The same procedure was done but using seawater containing 0.01 mL/L of diesel, before and after hypoxia. Antioxidant enzymes as well as levels of glutathione and lipid peroxidation were measured in gills and digestive glands. The neutral red retention time assay was also evaluated in hemocytes. Results showed that cycles of air exposure and reoxygenation caused oxidative stress and antioxidant modulation in both the gills and digestive glands. The presence of diesel in water triggered additional modulation of antioxidants under hypoxia and reoxygenation stress, apparently enhancing the capacity of mussels to avoid lipid peroxidation.

Mercury and selenium in oysters Saccostrea palmula and Crassostrea corteziensis from coastal lagoons of the southeastern Gulf of California: molar ratio and risk assessment on human health.

Total mercury (Hg) and selenium (Se) contents were determined in oysters Saccostrea palmula and Crassostrea corteziensis soft tissues from four coastal lagoons of the southeastern Gulf of California. The annual Hg mean concentrations for S. palmula (0.09 ± 0.04 µg g- 1, wet weight) and C. corteziensis (0.08 ± 0.04 µg g- 1) were similar (p ˃ 0.05) among the lagoons and did not exceed the limit established by the Norma Oficial Mexicana and World Health Organization (< 1.0 µg g- 1 Hg). On the other hand, the annual mean concentrations of Se for S. palmula (3.34 ± 0.96 µg g- 1) and C. corteziensis (2.79 ± 0.89 µg g- 1) were higher (p < 0.05) in El Colorado lagoon. The Se/Hg molar ratios were above 1; the positive selenium health benefit value index suggested that Se load in oysters could reduce the Hg potential toxic effect. The hazard quotient for Hg in both species was below 1. Therefore, the consumption of oysters does not represent a risk due to Hg ingestion.

Shape, Microstructure, and Chemical Composition of Pearls from the Freshwater Clam Diplodon chilensis Native to South America.

The capability to produce pearls is widespread in the phylum Mollusca, including bivalves of the superfamily Unionoidea. Here, we identified and characterized natural pearls formed by Diplodon chilensis, a freshwater clam native to southern South America, using samples obtained from two lakes located in the Chilean Patagonia. Pearls were studied using light and scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Naturally formed pearls were found in both male and female D. chilensis specimens. Pearls are produced in different shapes, including spherical, ellipsoidal, buttoned, and bumpy, ranging in size from 200 µm to 1.9 mm. The internal microstructure is composed of irregular polygonal tablets, about 0.40 to 0.55 µm in thickness. EDX analysis showed that pearls are composed of calcium carbonate. FTIR and Raman spectra recorded several peaks attributable to the aragonite in pearls of this species, as has been shown in other mollusks. In addition to these results, pearls of different colors are illustrated.

Oysters and mussels as equivalent sentinels of microplastics and natural particles in coastal environments.

Filter-feeder organisms such as oyster and mussels are exposed to particles like microplastics (MPs). Although widely used to monitor MPs contamination, little is known about their performance as sentinels, which are biological monitors accumulating contaminants without significant adverse effects. This study comparatively evaluated the quantitative and qualitative accumulation of MPs by oysters (Crassostrea brasiliana) and mussels (Perna perna) along a gradient of contamination in a highly urbanized estuarine system of Brazil. In the most contaminated site, both species presented the worst status of nutrition and health, and also one of the highest MPs levels reported for molluscs to date (up to 44.1 particles·g-1). Despite some inter-specific differences, oysters and mussels were suitable and showed an equivalent performance as sentinels, reflecting the gradient condition demonstrated for other contaminants in the region. The similarity in MPs accumulation was also observed for qualitative aspects (polymer composition, sizes, shapes and colors). Particles were mostly <1000 µm, fibrous, colorless and composed by cellulose and polymethyl methacrylate (PMMA). Thus, despite small variations, the usage of C. brasiliana and P. perna is recommended and provides reliable information for environmental levels of microplastics.

Effects of Carbon Nanoparticles and Chromium Combined Exposure in Native (Ruditapes decussatus) and Invasive (Ruditapes philippinarum) Clams.

Studies have described the occurrence of nanoparticles (NPs) in aquatic ecosystems, with particular attention to the widely commercialized carbon nanotubes (CNTs). Their presence in the environment raises concerns, especially regarding their toxicity when co-occurring with other pollutants such as metals. In the present study, changes to the metabolic capacity, oxidative, and neurologic status were evaluated in the presence of carboxylated multi-walled CNTs and chromium (Cr(III)) using two of the most ecologically and economically relevant filter feeder organisms: the clam species Ruditapes decussatus and R. philippinarum. Results indicated that although Cr, either alone or in combination with CNTs, was found in a similar concentration level in both species, a species-specific Cr accumulation was observed, with higher values in R. decussatus in comparison with R. philippinarum. Inhibition of antioxidant defenses and neurotoxic effects were detected only in R. philippinarum. The interaction between contaminants seems to have no effect in terms of antioxidant enzyme activities and neuro status. Nevertheless, synergistic activation of responses to both contaminants may have altered the metabolic capacity of bivalves, particularly evident in R. decussatus. While both clams are tolerant to both contaminants (alone and together), they showed a relevant accumulation capacity, which may represent a possible contaminant transfer to humans.

Biomonitoring of potentially toxic elements through oysters (Saccostrea palmula and Crassostrea corteziensis) from coastal lagoons of Southeast Gulf of California, Mexico: health risk assessment.

The coastal lagoons of the Gulf of California support important traditional fisheries and mollusc cultures (generally oysters) and receive important volumes of agricultural, industrial and urban effluents, consumption of the oysters could pose risk to human health. The concentrations of arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), and zinc (Zn) in the oysters Saccostrea palmula and Crassostrea corteziensis, from four coastal lagoons (Altata, AL; Macapule, ML; Navachiste, NL; El Colorado, ECL) in the Southeast Gulf of California, were seasonally evaluated (summer 2019-spring 2020). The order of magnitude of potentially toxic elements concentrations in the soft tissue in both oyster species and at all sites was Zn > Fe > Cu > As > Cd > Pb. Cadmium, Cu, Pb, and Zn exceeded the maximum permissible limits in more than one sampling site. The highest concentrations (mg kg-1, wet weight) of As (4.2 ± 1.1, spring) and Cd (3.3 ± 0.7, autumn) were registered in S. palmula et al. and NL sampling sites, respectively. Crassostrea corteziensis presented higher levels of Cu (40.5 ± 6.7, spring), Pb (2.0 ± 0.4, spring), and Zn (96.9 ± 20.4, spring) in ECL and Fe (62.2 ± 25.4, autumn) in ML. The hazard quotient (HQ) values exceeded the safe level of 1 for Cd in S. palmula and C. corteziensis in NL for children (~ 16 kg weight). In addition, in children, the hazard index (HI) values in both species of oysters ranged from 0.7 to 2.1 and 0.6 to 1.9, respectively. On the other hand, the intake of the studied elements through the consumption of oysters would not induce adverse effects to human health (men and women weighing 70 and 60 kg, respectively); HQ and HI values were < 1.

First Record of Microplastic Contamination in the Non-Native Dark False Mussel Mytilopsis leucophaeata (Bivalvia: Dreissenidae) in a Coastal Urban Lagoon.

Microplastic contamination is a global concern due to its conspicuous presence in aquatic ecosystems and its toxic nature to environmental and human health. False mussels are among the most notable fresh- and brackish water invaders. The invasive Mytilopsis leucophaeata in Rodrigo de Freitas Lagoon-RFL (Rio de Janeiro, Brazil) is the most abundant macrofaunal invertebrate, widely established and distributed throughout the lagoon. This study aimed to assess microplastic contamination in this invasive filter feeder and evaluate its potential use as a bioindicator. Agglomerates (~100 mussels) were manually collected using a stainless-steel spatula in ten sampling areas distributed throughout the whole lagoon and kept frozen. In the laboratory, 60 individuals were sorted by area for soft-tissue digestion. Each pool of 10 soft-tissue mussels (n = 6 by area) was wet-weighted and then placed in a 150-mL decontaminated glass beaker with 50 mL of 10% KOH. Samples were heated (40 °C) for 48 h, and digested samples were filtered in glass-fiber membranes. Microplastics were found in all samples of mussels (n = 60) from RFL; the particles were mostly lower than 100 µm with a mean concentration (±SD) of 35.96 ± 47.64 MPs g wet-weight-1. Microplastics were distinguished in seven shapes with different occurrences in samples (%): fiber (43.3%); fragment (34.3%); film (16.3%); sponge/foam (4.9%); pellet (0.57%), rope/filaments (0.17%); and undefined (0.4%). Thirteen colors of microplastics were found, but transparent (54.94%), black (10.77%), and white (9.36%) were the most common. Mytilopsis leucophaeata were useful to assess microplastic contamination in RFL and might be preferentially used in other invaded brackish systems instead of native and often threatened bivalves. Our results confirm the effective application of bivalves as an indicator of coastal microplastic pollution.

Microplastics and linear alkylbenzene levels in oysters Crassostrea gigas driven by sewage contamination at an important aquaculture area of Brazil.

The levels of linear alkylbenzenes (LABs) and the occurrence of microplastics (MPs) in the oysters Crassostrea gigas were evaluated in six farming areas in southern Brazil. The results revealed higher concentrations of LABs in oyster tissue from the Serraria (1977 ± 497.7 ng g-1) and Imaruim (1038 ± 409.9 ng g-1) sites. Plastic microfibers were found in oysters from all locations with values from 0.33 to 0.75 MPs per oyster (0.27-0.64 MPs per gram) showing the ubiquitous presence of this contaminant in the marine environment, which could be considered a threat to farming organisms. In addition, elements such as Ti, Al, Ba, V, Rb, Cr, and Cu were found in the chemical composition of the microfibers, suggesting MPs as vectors of inorganic compounds. A positive correlation between LABs and thermotolerant coliforms suggests that sewage discharges are the main source of contamination in these oysters cultured for human consumption. The present study highlights the need for efficient wastewater treatment plants and the implementation of depuration techniques in oysters from farming areas.

Presence of microplastics in six bivalve species (Mollusca, Bivalvia) commercially exploited at the Pacific coast of Costa Rica, Central America.

Microplastic pollution represents a serious threat to coastal marine systems. We evaluated the presence of microplastics (MPs) in 168 specimens of six commercially exploited bivalve species in the Golfo de Nicoya, Costa Rica. MPs were present in 100 % of the specimens of Leukoma asperrima and L. ecuadoriana, 74 % of Mytella strigata, 82 % of M. guyanensis, 84 % of Asthenometis asthenodon, and 82 % of Tagelus affinis. When considering all specimens, we found on average 4.8 ±â€¯8.0 pieces per individual and 2.1 ±â€¯3.3 items g-1 of wet tissue. There were significant differences between species with L. asperrima and L. ecuadoriana containing the highest number of pieces. Fibers and particles comprised 92 % and 8 %, respectively. This is the first study from the Central America's Pacific region showing the presence of MPs in bivalve species.

A checklist of larval Digenea (Platyhelminthes: Trematoda) in molluscs from inland waters of Argentina: one hundred years of research.

A checklist of larval digeneans parasitising molluscs from inland waters of Argentina is presented here. Based on the bibliographical survey of 113 scientific articles and nine theses published between 1930 and 2021, 213 digeneans were found, which were distributed within 13 superfamilies and 35 families. The parasites were identified in 102 locations, encompassing eight of the sixteen biogeographical provinces in Argentina. Digeneans were found in 34 mollusc species (31 gastropods and three bivalves) belonging to 17 genera. The available data are presented for each digenean species, and included host information, localities, prevalence values, type of habitat, life cycle information (natural or experimental host), and information on material and genetic sequences deposited in repositories. Only 21.1% of individuals were identified to species level, and 8.5% to genus level. In addition, the genetic sequences of only 10 species (4.7%) were available at GenBank. This survey constitutes the first checklist of parasitic helminths in molluscs from inland waters of Argentina.

Parasitism by metacercariae modulates the morphological, organic and mechanical responses of the shell of an intertidal bivalve to environmental drivers.

Environmental variation alters biological interactions and their ecological and evolutionary consequences. In coastal systems, trematode parasites affect their hosts by disrupting their life-history traits. However, the effects of parasitism could be variable and dependent on the prevailing environmental conditions where the host-parasite interaction occurs. This study compared the effect of a trematode parasite in the family Renicolidae (metacercariae) on the body size and the shell organic and mechanical characteristics of the intertidal mussels Perumytilus purpuratus, inhabiting two environmentally contrasting localities in northern and central Chile (ca. 1600 km apart). Congruent with the environmental gradient along the Chilean coast, higher levels of temperature, salinity and pCO2, and a lower pH characterise the northern locality compared to that of central Chile. In the north, parasitised individuals showed lower body size and shell resistance than non-parasitised individuals, while in central Chile, the opposite pattern was observed. Protein level in the organic matter of the shell was lower in the parasitised hosts than in the non-parasitised ones regardless of the locality. However, an increase in polysaccharide levels was observed in the parasitised individuals from central Chile. These results evidence that body size and shell properties of P. purpuratus vary between local populations and that they respond differently when confronting the parasitism impacts. Considering that the parasite prevalence reaches around 50% in both populations, if parasitism is not included in the analysis, the true response of the host species would be masked by the effects of the parasite, skewing our understanding of how environmental variables will affect marine species. Considering parasitism and identifying its effects on host species faced with environmental drivers is essential to understand and accurately predict the ecological consequences of climate change.

Saxitoxin Group Toxins Accumulation Induces Antioxidant Responses in Tissues of Mytilus chilensis, Ameghinomya antiqua, and Concholepas concholepas during a Bloom of Alexandrium pacificum.

Saxitoxin (STX) group toxins consist of a set of analogues which are produced by harmful algal blooms (HABs). During a HAB, filter-feeding marine organisms accumulate the dinoflagellates and concentrate the toxins in the tissues. In this study, we analyze the changes in antioxidant enzymes and oxidative damage in the bivalves Mytilus chilensis and Ameghinomya antiqua, and the gastropod Concholepas concholepas during a bloom of Alexandrium pacificum. The results show that during the exponential phase of the bloom bivalves show an increase in toxicity and activity of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, and glutathinoe reductase, p < 0.05), while in the gastropods, increased activity of antioxidant enzymes was associated with the bioaccumulation of toxins through the diet. At the end of the bloom, decreased activity of antioxidant enzymes in the visceral and non-visceral tissues was detected in the bivalves, with an increase in oxidative damage (p < 0.05), in which the latter is correlated with the detection of the most toxic analogues of the STX-group (r = 0.988). In conclusion, in areas with high incidence of blooms, shellfish show a high activity of antioxidants, however, during the stages involving the distribution and bioconversion of toxins, there is decreased activity of antioxidant enzymes resulting in oxidative damage.

Environmentally realistic concentrations of cocaine in seawater disturbed neuroendrocrine parameters and energy status in the marine mussel Perna perna.

Cocaine (COC) is a powerful illicit drug frequently detected in the aquatic environment. COC acts by inhibiting the reuptake of dopamine (DOPA) and 5-hydroxytryptamine (5-HT - serotonin) and causes endocrine disturbances in mammals. This study investigated similar effects from cocaine exposure in the marine mussel Perna perna, as well as neurotoxicity and energy imbalances. Mussels were exposed to COC (0.2 µg.L-1 and 2 µg.L-1) for periods of 48, 96, and 168 h. Acetylcholinesterase (AChE) was measured in adductor muscle tissue to determine neurotoxicity, and neurotransmitter levels (DOPA and 5-HT), monoamine oxidase (MAO) and cyclooxygenase (COX) activity, and energy status (mitrochondrial electron transport, MET, and total lipids, TLP) were evaluated in the mussels' gonads. COC decreased AChE activity in the mussels exposed to 0.2 µg.L-1 and 2 µg.L -1 after 168 h, and all concentrations of COC increased neurotransmitter levels. Increases in MET (0.2 µg.L -1, for all exposure periods) and TLP (0.2 µg.L 1 after 48 h, and 2 µg.L -1 after 96 h and 168 h) were also observed. No significant change was detected in MAO activity. COC also decreased COX activity in the mussels exposed to 0.2 µg.L -1 (48 h and 96 h) and 2 µg.L -1 (96 h). These results suggest that COC may compromise neurotransmitter levels and COX activity. Furthermore, the changes in MET and LPT suggest that COC affects the energy balance of the mussels, and could negatively affect physiological processes such as metabolism, hormone production, and embryonic development.

Elemental Contamination in Brown Mussels (Perna perna) Marketed in Southeastern Brazil.

Perna perna mussels, abundant throughout the Brazilian coast, are routinely applied as bioindicators in environmental monitoring actions due to their sessile and filter-feeding characteristics. In addition, they are noteworthy for their food importance, especially for coastal populations. In this context, the aim of this study was to investigate elemental contamination in commercially marketed and highly consumed P. perna samples from the highly impacted Guanabara Bay, Rio de Janeiro, Brazil. A total of 30 mussels were sampled, and elemental concentrations (As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn) were determined in adductor muscle samples by inductively coupled plasma mass spectrometry (ICP-MS). Human consumption risks were assessed by comparisons to Brazilian and international legislations. No significant differences between sex were observed for all analyzed elements. Even when analyzing only the adductor muscle, all mussel samples exceeded the Brazilian limit for Cr, while 12 samples exceeded the limit for Se. When compared to other regulatory agencies, As and Zn levels were higher than the limits set by China, New Zealand, and the USA. Estimated daily dietary intake values were not above limits imposed by the Food and Agriculture Organization of the United Nations/World Health Organization for any of the assessed elements, although it is important to note that only the adductor muscle was assessed. Therefore, continuous metal and metalloid monitoring in bivalves in the study region is suggested, as metal transport and bioavailability, especially in coastal estuaries such as Guanabara Bay, which are currently undergoing significant changes due to anthropogenic activities.

Rainfall effects on Anomalocardia flexuosa densities on the northeastern Brazilian coast using distributed lag models / Efeitos da chuva na densidade de Anomalocardia flexuosa na costa nordeste do Brasil usando modelos de defasagem distribuída

In this study, the effects of precipitation on Anomalocardia flexuosa densities were analyzed from the perspective of temporal delays between the variables. The collections occurred bi-monthly between April 2016 and February 2018 at Mangue Seco beach, Pernambuco, Brazil. Total densities and densities according to the category of size (small, medium and large), and precipitation were analyzed with autocorrelation and cross-correlation functions, with a retrospective analysis of up to 12 months. Distributed lag models were used among the variables. The maximum density was found in June 2017 (378 ind.m2) for the medium-size category of individuals. Significant autocorrelations occurred for densities (total and average size) and precipitation. In cross-correlation functions, high precipitation for a given month was followed by high densities of total and average individuals for up to two months. Distributed lag models also showed significant values between densities (total and medium-sized) and precipitation, which explained more than 50% of the variability of these two groups. The effect of precipitation was responsible for the increase in the density of A. flexuosa for up to two months, mainly by increasing individuals with medium shell lengths.

Neste estudo, foram analisados os efeitos da precipitação nas densidades de Anomalocardia flexuosa sob a perspectiva de atrasos temporais entre as variáveis. As coletas foram bimensais, entre abril de 2016 e fevereiro de 2018, na praia de Mangue Seco, Pernambuco, Brasil. As densidades totais e por categoria de tamanho (pequeno, médio e grande) e a precipitação foram analisadas com as funções de autocorrelação e correlação cruzada, com análise retrospectiva de até 12 meses. Modelos de defasagem distribuída foram empregados entre as variáveis. A densidade máxima foi encontrada em junho de 2017 (378 ind.m²) na categoria de tamanho médio dos indivíduos. Autocorrelações significativas ocorreram nas densidades (total e tamanho médio) e precipitação. Nas funções de correlação cruzada, a alta precipitação de determinado mês foi seguida por alta nas densidades total e de indivíduos médios por até dois meses. Os Modelos de defasagem distribuída também apresentaram valores significativos entre as densidades (total e tamanho médio) e a precipitação, explicando mais de 50% da variabilidade desses dois grupos. O efeito da precipitação foi responsável pelo aumento da densidade de A. flexuosa por até dois meses, principalmente pelo incremento de indivíduos com comprimentos de concha medianos.

Concentration of microplastics in bivalves of the environment: a systematic review.

The aim of this review was to identify the current knowledge regarding the concentration of microplastics in bivalves in the marine, estuarine, and freshwater environments. For this purpose, researches were conducted from September 2020 to February 2021 in the Scopus, Web of Science, and Google scholar databases, following a meticulous selection of articles. To comprehensively understand the selected articles, an extensive review was carried out in order to identify the methodologies employed, sampling sites, species evaluated, characteristics of the microplastics (concentrations, shapes, sizes, and polymers) and their relationship with the concentration of this particles in the environment. A total of 93 articles were selected, with an exponential growth in the number of articles from April 2014 to February 2021. Worldwide, 80 articles were realized in the Northern Hemisphere and thirteen in the Southern Hemisphere. The samplings of organisms were carried out in 36 countries, besides one in Antarctica. The concentration of microplastics were studied in 70 species, with mussels Mytilus spp. and the oysters Crassostrea spp. being the main genus studied. Due to the different methodologies used to digest the tissues of organisms and identify microplastics and species, it is difficult to make comparisons between the results of different studies. In addition, data on the concentrations of microplastics in the environment, as well as their composition and characteristics, are needed, enabling the verification of relationships with the concentrations identified in organisms, which does not occur in most studies. Thus, we suggest an increase in the number of studies to be realized in the southern hemisphere, future studies use the same methodology of digestion, the polymer identification of microplastics and samplings of the surrounding environment, enabling a greater comparison between studies.