Mytilus Chilensis Research Articles

Carbonate chemistry dynamics in shellfish farming areas along the Chilean coast: natural ranges and biological implications

AbstractThe increasing shellfish aquaculture requires knowledge about nearshore environmental variability to manage sustainably and create climate change adaptation strategies. We used data from mooring time series and in situ sampling to characterize oceanographic and carbonate system variability in three bivalve aquaculture areas located along a latitudinal gradient off the Humboldt Current System. Our results showed pHT <8 in most coastal sites and occasionally below 7.5 during austral spring–summer in the lower (−30°S) and central (−37°S) latitudes, related to upwelling. Farmed mussels were exposed to undersaturated (Ωarag < 1) and hypoxic (<2 ml l−1) waters during warm seasons at −37°S, while in the higher latitude (43°S) undersaturated waters were only detected during colder seasons, associated with freshwater runoff. We suggest that both Argopecten purpuratus farmed at −30°S and Mytilus chilensis farmed at −43°S may enhance their growth during summer due to higher temperatures, lower pCO2, and oversaturated waters. In contrast, Mytilus galloprovincialis farmed at 37°S grows better during spring–summer, following higher temperatures and high pCO2. This knowledge is relevant for aquaculture, but it must be improved using high-resolution time series and in situ experimentation with farmed species to aid their adaptation to climate change and ocean acidification.

Exploring drying kinetics and energy exergy performance of Mytilus Chilensis and Dosidicus gigas undergoing microwave treatment

Drying kinetics of food materials treated under microwave irradiation is a crucial process to predict moisture content, design, and optimize the drying characteristics. In this study, the performance energy and exergy of two products of Dosidicus gigas and Mytilus Chilensis were analyzed undergoing microwave treatment. Basically fitting of five well-known empirical models was tested for the two types of seafood. Statistical and empirical modeling of the drying curves revealed that the Page model was the most suitable to fit the drying experimental curves of Mytilus and Dosidicus gigas. Various microwave power outputs at (90,160,360, 600, and 750 W) were tested to evaluate their influence on drying kinetics and moisture diffusivity of seafood samples. Specific energy consumption varied from 1.76 to 11.42 and 5.20 to 11.34 MJ/kg for Dosidicus gigas and Mytilus Chilensis respectively. The best exergy and energy aspect appears to be at 90 W microwave power for the drying products. Also, the improvement potential increased with an increase in microwave power, and its values for both products were ranging from 0.58 to 29.70 kJ/kg water. The effective moisture diffusivity increased as well as the microwave generation increased. The activation energy was determined using Arrhenius Law with values of 9.34 and 9.36 kW/kg for Dosidicus gigas and Mytilus Chilensis respectively.

Efectos de la densidad de siembra y el desdoble sobre el crecimiento y la supervivencia en un cultivo suspendido experimental del mejillón Mytilus platensis d’Orbigny, 1842, en el Golfo San Jorge, Argentina

En los últimos años, ha habido un renovado interés en el desarrollo del cultivo de mejillones en la Argentina. Sin embargo, esta actividad todavía tiene lugar a pequeña escala o de forma experimental en la región patagónica. Conocer los efectos de las densidades iniciales y el desdoble sobre el crecimiento y la supervivencia en un cultivo experimental es información de base necesaria para el desarrollo de experiencias que permitan estudiar parámetros productivos en cultivos a mayor escala. Por estos motivos, este trabajo tuvo como objetivo analizar el efecto de las densidades iniciales y el desdoble sobre el crecimiento y la supervivencia del mejillón Mytilus platensis en un cultivo suspendido experimental en la región costera central del Golfo San Jorge, Argentina. Para ello, se estudiaron dos técnicas de cultivo, con y sin desdoble, durante un período de 9 meses, a dos densidades iniciales (400 y 700 ind. m-1). La semilla fue obtenida de un criadero artificial. Se monitorearon talla, peso y supervivencia de los mejillones. El mayor crecimiento en talla y peso, y la supervivencia más elevada se observaron en la estrategia sin desdoble con la densidad más baja. En esta estrategia, los animales alcanzaron una talla promedio mayor a 65 mm, llegando a la talla comercial en menos de un año. Estos resultados permiten concluir que, a pequeña escala, la estrategia sin desdoble es la recomendada para cultivar mejillones en la región a una densidad de 400 ind. m-1 durante un mínimo de 9 meses.

In vitro biotransformation of OA-group and PTX-group toxins in visceral and non-visceral tissues of Mytilus chilensis and Ameghinomya antiqua

ABSTRACT Lipophilic marine toxins (LMTs) are made up of multiple groups of toxic analogues, which are characterised by different levels of cellular and toxic action. The most prevalent groups in the southern Pacific zone are: a) okadaic acid group (OA-group) which consists of okadaic acid (OA) and dinophysistoxin-1 (DTX-1); and, b) pectenotoxin-2 (PTX2) group which consists of pectenotoxin-2 (PTX-2). The main objective of our study was to examine in vitro biotransformation of OA-group and PTX-group in the tissues of two endemic species of bivalves from southern Chile; blue mussels (Mytilus chilensis) and clams (Ameghinomya antiqua). The biotransformation processes of both groups were only detected in the digestive glands of both species using LC-MS/MS. The most frequently detected analogues were acyl derivatives (≈2.0 ± 0.1 μg ml−1) for OA-group and PTX-2SA (≈1.4 ± 0.1 μg ml−1) for PTX-group, with a higher percentage of biotransformation for OA-group (p < .001). In addition, simultaneous incubations of the different analogues (OA/PTX-2; DTX-1/PTX-2 and OA/DTX-1/PTX-2) did not show any interaction between the biotransformation processes. These results show that the toxicological variability of endemic species leads to biotransformation of the profile of toxins, so that these new analogues may affect people’s health.

Simultaneous determination of oxo- and thio-arsenic species using HPLC-ICP-MS

A method for simultaneous analysis of common oxo-arsenic species and their thio-analogues by coupling ion-pair liquid chromatography to inductively coupled plasma mass spectrometry was developed and validated. The chromatographic separation was performed using a C8 stationary phase and a mobile phase containing 1.2 mmol/L tetramethylammonium hydroxide, 4 mmol/L malonic acid, 6.2 mmol/L sodium butane-1-sulfonate, and 0.05 % (v/v) methanol. Under these conditions, the 11 arsenic species (arsenite, arsenate, dimethylarsinic acid, monomethylarsonic acid, arsenobetaine, arsenocholine, tetramethylarsonium cation, trimethylarsine oxide, dimethyldithioarsinic acid, monomethylmonothioarsinic acid, and trimethyarsine sulfide) were separated. The detection limits for these species ranged from 1.4 to 4.0 ng/g As. The method was applied to the analysis of fish, crustacean, mussel, cephalopod and mushroom samples. Thio-arsenic species DMDTAV were found in mussel Mytilus chilensis and cuttlefish Sepis pharaonis samples in very low contents of 23 and 21 ng/g As, respectively. All seafood samples contained predominantly arsenobetaine (330–8570 ng/g As); other As species were present at various contents from 7 to 325 ng/g As.

Mussels (Mytilus spp.) products authentication: A case study on the Italian market confirms issues in species identification and arises concern on commercial names attribution

In November 2019, the FishLab was consulted by a wholesaler for solving an authentication issue concerning a batch of products labelled as “Chilean mussels” (Mytilus chilensis). Samples of the batch had been molecularly identified first as M. chilensis by an external private lab and, subsequently, as Choromytilus chorus through a second analysis entrusted to another external lab by the customer company. The analysis carried out at the FishLab only allowed to identify the samples to genus level (Mytilus spp.) by sequencing the mitochondrial COI gene. The amplification of the Polyphenolic Adhesive Protein (PAP) gene, a nuclear marker reported as informative for mussel, allowed to suppose the presence of M. chilensis and M. galloprovincialis based on the length of the obtained fragment. In parallel, an in silico analysis of the PAP sequences currently available on GenBank highlighted the lack of the typical mutation point in some sequences of M. galloprovincialis that were identical to those of M. chilensis. Based on a case study investigating mussel products suspected to be mislabelled, this work wants to confirm issues in molecular species identification of Mytilus spp. and highlight concerns on commercial names attribution. Results first confirmed previous scientific community opinion discouraging the use of mtDNA for Mytilus spp. identification due to both its unusual inheritance mechanism and introgression phenomena. The outcomes of the in silico analysis of the PAP sequences called into question the reliability of this marker in discriminating among M. chilensis and M. galloprovincialis. Therefore, also considering the uncertainties of the taxonomic status of these species, a proper re-evaluation process of this marker is needed. However, also the approach one species-one name, currently adopted by the Italian legislator, should be revised for solving labelling issues affecting the market.

Authentication of Frozen Chilean Blue Mussel (Mytilus chilensis) Commercialized in the Town of Osorno, Southern Chile, Using PCR-RFLP Analysis.

DNA-based technologies are reliable authentication methods for food products, enabling the detection of fraud, non-intentional substitution and control of mislabeling. The Chilean blue mussel (Mytilus chilensis) is a seafood commercialized in Chile under different formats, including packages of frozen specimens. In this format, the valves of mussels are removed during processing, thus impeding identification of the product by the consumer due to the lack of external characters. To assess the authenticity of frozen Chilean blue mussels commercialized in southern Chile, particularly in the town of Osorno. Six commercial brands of frozen Chilean blue mussel were authenticated by the Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) method, based on the analysis of an 18S rDNA fragment. Restriction patterns obtained indicate that three brands (50%) proved to be 100% authentic, given that all specimens contained in the package were Chilean blue mussels. The other three brands (50%) contained specimens of other commercial mytilids, particularly the cholga mussel (Aulacomya ater), in a variable percentage (12.5-50%). This study based on the PCR-RFLP method provides evidence that Chilean blue mussels commercialized in a town located in southern Chile lack authenticity. This finding highlights the necessity for national producers to improve the production and/or packaging processes of this seafood. The authentication of commercial mussels is a matter of consumer interest and has been described in a recent patent on this issue that proposes an alternative methodology.

Complex Spatial Genetic Connectivity of Mussels Mytilus chilensis Along the Southeastern Pacific Coast and Its Importance for Resource Management

To ensure the maintenance of natural mussel beds along the southeastern Pacific coast of Chile, it is important to understand their population dynamics. This means evaluating their genetic population structure and gene flow, and the degree of connectivity among natural beds. To do this, the spatial genetic population structure of seven natural Mytilus chilensis beds within the mussels' present distribution range along the Chilean coast was evaluated. Genetic differences were established between populations with cytochrome oxidase I (COI) gene sequences (Fst = 0.099) and microsatellites (Fst = 0.048), showing that locations that consistently presented greater differentiation were those at the extremes of the geographical distribution. An “isolation by distance” pattern was not observed in the COI and microsatellite data. We suggest that because of the high resolution of these markers, the differences between locations may be explained by high reproductive variance, which determines local changes in each reproductive cycle of the species. These changes would account for the differences between the natural beds. Furthermore, differentiated genetic types were observed in some locations, demonstrating the presence of local processes in some cases, perhaps caused by gene flow restrictions resulting from the local geomorphological and oceanographic conditions. The gene structure and connectivity of natural beds in sessile species with larval dispersion are strongly determined by local retention characteristics. For this reason, the data generated in this study can be used to improve population management. These data can also be used to support and motivate the creation of a marine protected area containing natural beds of this species with sufficient levels of genetic diversity.

The combined effects of salinity and pH on shell biomineralization of the edible mussel Mytilus chilensis

Coastal ecosystems influenced by river discharges are subjected to important environmental changes. Understanding how marine biota cope with its environment is relevant in predicting the responses to future conditions imposed by climate change. To date, a large number of studies have addressed the role of pH on shell and biomineralization properties on multiple calcifying species; however the role of salinity in combination with other stressors has been poorly studied. In particular, the edible mussel Mytilus chilensis, an important marine resource of the Chilean coasts, inhabits estuarine areas which show high natural variability in terms of pH and salinity. Here, we studied how M. chilensis shell periostracum, shell organic matrix and crystal orientation are affected by different pH (8.1 and 7.7) and salinity conditions (30, 25 and 20 psu), isolated and in combination, at different time intervals. Our results show differences in the plasticity of the different biomineralogical properties studied during the experiment under the different pH and salinity treatments. While the periostracum thickness and the total shell organic matter were not affected by pH and salinity, the periostracum organic composition did. Higher amounts of polysaccharides were observed under low pH conditions after 20 days of experiment, while after 60 days, low salinity was responsible for the decrease of the polysaccharides and proteins in the periostracum. Low salinity also produced a major disorder in crystal organization at the outer shell surface. Finally, total shell weight was only affected by low pH conditions under lower salinity conditions (20 psu). From the results, in the majority of the shell properties observed we did not observe any combined effect of pH and salinity. Also, we detected that the magnitude of the impacts of salinity and pH are variable and time-dependent. This would be suggesting some level of acclimatization of M. chilensis to lower pH and salinity conditions.

Possible role of seasonality and harmful algal blooms (HAB) on the oxidative and nitrosative metabolisms in hemocytes

Bivalves survive to biotoxin consumption but their metabolism could be affected. The objective of this work was to study the oxidative and nitrosative changes in the hemocytes of the mussel Mytilus edulis platensis in different seasons, including spring, characterized by the appearance of harmful algal blooms (HAB). Reactive species generation rate (measured as the 2′,7′dichlorofluorescein diacetate oxidation rate) was increased by 2.5- and 8.3-fold in hemocytes from spring and summer, respectively, as compared to winter samples. Neither total Fe nor labile Fe pool content was changed in the three seasons. Superoxide anion generation rate was 3-fold higher in spring as compared to winter and summer samples. Catalase content in spring cells were significantly higher as compared to winter (60%) and summer (3-fold increase) but glutathione-S-transferase activity only increased compared to summer season (125% increase). Lipid radical content in spring samples was 140 and 50% higher as compared to cells from winter and summer, respectively. Nitric oxide and nitro-tyrosine content were significantly higher in samples from spring as compared to values obtained either in winter or summer cells. Considering the aspects that influence metabolism, changes in temperature seem to mainly affect the oxidative over the nitrosative condition of the hemocytes. Nevertheless, HAB biotoxins seem as a contributing factor to affect not only reactive oxygen species generation, antioxidant activity and protein/lipid damage, but also the nitrosative metabolism. In this regard, the changes in the nitric oxide content are new and critical evidence that HAB-related toxins could affect reactive nitrogen species metabolism.

The filter-feeding bivalve Mytilus chilensis capture pelagic stages of Caligus rogercresseyi: A potential controller of the sea lice fish parasites.

The copepod Caligus rogercresseyi is an ectoparasite of several salmonid species. The pumping activity of filter-feeding molluscs could reduce the abundance of copepod dispersive larval stages in the water column. In this research, nauplius II and copepodid larvae of C. rogercresseyi were exposed to filtering mussels (Mytilus chilensis) of different sizes. These mussels were able to filter both larval stages, although they were more efficient in catching nauplius II. The fact that nauplius II were ingested more efficiently could be explained by their smaller size, lower swimming velocity (escape) and longer resting times between movements, when they were exposed to the influx of water around the inhalant area of the mussels. Larger mussels were more effective filtering C. rogercresseyi larvae due to their larger inhalant area and the related water influx. Additionally, the results suggest that larvae captured by the mussels can be incorporated into pseudofaeces or ingested and then released as part of the faeces. Thus, high concentrations of M. chilensis surrounding salmon farms may act as biological barriers, reducing the density of copepod dispersive larval stages and, thus, salmon infestations.

Experimental exposure of the mussel Mytilus platensis (d'Orbigny, 1842) to the dinoflagellate Alexandrium catenella from Argentine Patagonia.

Individuals of Mytilus platensis were exposed to Alexandrium catenella to evaluate the accumulation and metabolization of paralytic shellfish toxins (PST) over a period of 25 days. Mussels were collected from the intertidal zone of Cerro Avanzado, Argentine Patagonia. After 16 days, the toxins in the tissues of mussels were detected by the methods of mouse bioassay and high performance liquid chromatography with fluorometric detection (HPLC-FDL). The accumulation kinetics of PST toxins in M. platensis fed with A. catenella fitted to a linear function, in which the accumulation rate was 31.2 µg STX eq kg-1 day-1. After 16 days, the PST toxin level in tissues of mussels reached 1178 µg STX eq kg-1 exceeding the safety limit for human consumption (800 µg STX eq kg-1 tissue), whereas the highest PST toxin level was reached at the end of the experimentation (1613 µg STX eq kg-1) at 25 days. Differences in the toxin profile of the dinoflagellates and the tissues of the mussels confirmed biotransformation of PST in the mussel digestive system. The toxin profile of M. platensis was dominated by the gonyautoxins GTX1 and GTX4, while the toxin profile of A. catenella was dominated by the N-sulfocarbamoyl toxin C2. To our knowledge, this is the first experimentation on a laboratory scale of PST toxins accumulation in M. platensis with a native strain of A. catenella of Argentine Patagonia.

A biogeography‐based management for Mytilus chilensis: The genetic hodgepodge of Los Lagos versus the pristine hybrid zone of the Magellanic ecotone

Abstract This study was intended to identify mussel species from the Magellanic ecotone, quantifying interspecific hybridization within Mytilus and depicting the genetic architecture of Mytilus chilensis in its South Pacific range. The analysis comprises the sub‐Antarctic Magallanes Province as a rich ecotone of climates, ecosystems and admixed faunas embedded among the biogeographic regions of the Pacific, the Atlantic, and Antarctica. Highly conserved molecular sequences within species were used to identify species, and polymorphic microsatellites were used to calculate the genetic architecture of M. chilensis. The absence of the invasive species Mytilus galloprovincialis from the M. chilensis range clarifies previous doubts on its expansion southward from the Arauco Gulf. The ubiquitous presence of the typical Glu‐5′‐Me‐15/16 PAP allele of Mytilus trossulus in the Northern Hemisphere might come from hull biofouling, but rather it seems to be an ancient polymorphism conserved in M. chilensis as occurs in blue mussels from other regions of the Southern Hemisphere. There is a very limited connectivity (FST = 0.167) between two latitudinal gene pools of M. chilensis that are highly divergent in composition, architecture, and ecological relevance. Fifty years of aquaculture enhancement in Los Lagos explains its high diversity and genetic heterogeneity among patches, so its mussel management should seek a balance between exploitation and environmental sustainability. The Magellanic ecotone bears a pristine M. chilensis × Mytilus edulis platensis hybrid zone around the Southern Cone, larger (450 km) than previously thought. Such a hybrid zone permeates one of the last remaining wilderness areas in the world (Cape Horn Biosphere Reserve) and is a natural laboratory for addressing introgression, hybridization, and evolution of Mytilus spp. genomes in their last southern frontier.

Exploring the adaptive capacity of the mussel mariculture industry in Chile

Societies have adapted to climate and environmental variability throughout history. However, projected climate change poses multiple risks to mariculture because of the increased frequency of environmental threats that lie outside the realm of present day experience. Adaptive capacity evaluated in this study is a characteristic that would reflect mariculture industries ability to anticipate and respond to these changes, and to minimize, cope with, and recover from the consequences and take advantage of new opportunities arising from change. Drawing on a survey to 90 mussel mariculture companies in Chiloe-Chile, we have characterized the way the industry has adapted and recovered from specific stressors in productive capacity, namely; reduced mussel growth rates and reduced larval supply. We additionally assess determinants of the mussel industry's willingness to invest in building capacity to anticipate changes through analysing mussel aquaculture companies' assets to draw upon in times of need (capital; access to credit), the flexibility to change strategies, the companies' perception of the industry's social organization to act collectively (social capital), and their response to hypothetical scenarios regarding shocks in productive capacity. Results show heterogeneity in production decisions when facing environmental stressors. Results also show that the industry adapts in heterogeneous ways and that financial assets and social capital drive willingness to invest in adaptive capacity. Understanding past adaptation strategies and the willingness of the industry to invest in anticipating stressors allows us to begin exploring the consequences of new stressors. Importantly, as Chile and other countries are developing adaptation plans to face the multiple stressors of climate change, information about stakeholders' existing adaptation strategies and their determinants is becoming a critical bottleneck to inform these processes and assure they are in line with stakeholder needs and interest. While we use the Chilean mussel industry as a working example, the approach presented can inform other countries/regions wishing to explore the adaptive capacity of their aquaculture sectors.

A single clonal lineage of transmissible cancer identified in two marine mussel species in South America and Europe.

Transmissible cancers, in which cancer cells themselves act as an infectious agent, have been identified in Tasmanian devils, dogs, and four bivalves. We investigated a disseminated neoplasia affecting geographically distant populations of two species of mussels (Mytilus chilensis in South America and M. edulis in Europe). Sequencing alleles from four loci (two nuclear and two mitochondrial) provided evidence of transmissible cancer in both species. Phylogenetic analysis of cancer-associated alleles and analysis of diagnostic SNPs showed that cancers in both species likely arose in a third species of mussel (M. trossulus), but these cancer cells are independent from the previously identified transmissible cancer in M. trossulus from Canada. Unexpectedly, cancers from M. chilensis and M. edulis are nearly identical, showing that the same cancer lineage affects both. Thus, a single transmissible cancer lineage has crossed into two new host species and has been transferred across the Atlantic and Pacific Oceans and between the Northern and Southern hemispheres.

Isolation and Antimacrofouling Activity of Indole and Furoquinoline Alkaloids from 'Guatambú' Trees (Aspidosperma australe and Balfourodendron riedelianum).

In this work, the antifouling activity of five alkaloids, isolated from trees of the Atlantic rainforest, was studied. The tested alkaloids were olivacine (1), uleine (2) and N-methyltetrahydroellipticine (3) from Aspidosperma australe ('yellow guatambú') and the furoquinoline alkaloids kokusaginine (4) and flindersiamine (5) from Balfourodendron riedelianum ('white guatambú'). All these compounds can be isolated from their natural sources in high yields in a sustainable way. The five compounds were subjected to laboratory tests (attachment test of the mussel Mytilus edulis platensis) and field trials, by incorporation into soluble matrix paints, and 45 days of exposure of the painted panels in the sea. The results show that compound 3 is a very potent antifoulant, and that compounds 4 and 5 are also very active, while compounds 1 and 2 did not show any significant antifouling activity. These results open the way for the development of environmentally friendly antifouling agents, based on abundant and easy-to-purify compounds that can be obtained in a sustainable way.

Antifouling activity of peracetylated cholic acid, a natural bile acid derivative

The antifouling activity of peracetylated cholic acid (1), a bile acid derivative which was isolated in a previous work as a natural product from the Patagonian sponge Siphonochalina fortis, was evaluated in laboratory and field trials. Toxicity and settlement assays were performed with the mussel Mytilus edulis platensis, while the field trials were carried out by addition of the compound to experimental soluble-matrix paints, which were then tested in the sea. The results obtained in this work show that 1 has a good antifouling activity and low toxicity, and the paints aditivated with 0,6% Wt showed promissory performances in the field trials at the sea. These results confirm the previous hypothesis that the few acetylated and lipophilic bile acid derivatives isolated from marine invertebrates may act as natural antifoulants. Compound 1 is a natural, biodegradable product that can be easily prepared from cholic acid, which in turn can be isolated in industrial scale from cattle bile. All these facts make cholic acid a good scaffold for the preparation of derivatives, which can be natural product-like, effective and sustainable antifouling additives for marine paints and other applications.

Managing complexity of marine ecosystems: From the monitoring breakdown structure (MBS) to the baseline assessment. Trace metal concentrations in biomonitors of the Beagle Channel, Patagonia (2005–2012)

Abstract In this study we propose a conceptual framework, i.e. the Monitoring Breakdown Structure (MBS) as a tool for the management of marine ecosystems. The conceptual framework thinks through the complexity of marine ecosystems keeping into account the variety (space) and variability (time) dimensions. Consistently with the MBS we have built the control charts of trace metal concentrations of two selected biomonitors in the Beagle Channel (south Patagonia) (case study). Thus, we have tested the aptitude of two species of mollusks as biomonitors of heavy metal (HMs) pollution. The selected species were the limpet Nacella (P) magellanica and the bivalve Mytilus chilensis. Seven hundred eighty-five samples were collected along 170 km of the coastal area of the Beagle Channel (BC), (Tierra del Fuego, Argentina) in seven selected georeferenced locations and four sampling campaigns (2005, 2007, 2011, 2012). Cd, Cr, Cu, Ni, Pb and Zn determinations in seawater and mollusks by atomic absorption spectrometry (AAS) were carried out. The calculation of the respective concentration factors (CFs), i.e. their capacity as strong bioaccumulators, was also conducted. This is of relevance because it aims to use these data as a baseline reference for other geographical areas. Second, we have compared metal bioaccumulation differences among sites and the contamination trend by building, for the first time, the control charts of the baseline metal concentrations in the biomonitors. For these purposes, we applied probabilistic Johnson's method. Furthermore, the control charts (based on four years baseline data) allowed us to test the contamination trend by plotting data from 2012 vs 2011. Our results confirm N. magellanica as an extremely strong accumulator of Cd, and M chilensis strong bioaccumulator of Cd and Zn. Zn was the most abundant metal followed by Cu. Overall, regarding the contamination trend, based on thousands of determinations we observed that the six mean metal levels were quite constant over time. Moreover, metal distribution among sites turned out to be not univocal (no one site is more contaminated than the other sites). Thus, the expected hypothesis of Ushuaia Harbour as being the most contaminated site should be reconsidered. This reinforces the hypothesis of our data as baseline data (except for cadmium), that should be considered in management decisions about future environmental monitoring programs, i.e. preventing/managing marine accidents.

Comparative growth of Mytilus chilensis (Hupé 1854) and Mytilus galloprovincialis (Lamarck 1819) in aquaculture longline system in Chile

Choosing an alternative species of mussel for the aquaculture industries, will be possible if it has equal or greater yield than the mussel cultivated. This study compares the growth of the chilean native mussel Mytilus chilensis with the non-native Mediterranean mussel Mytilus galloprovincialis and evaluate if environmental variables and cultivation depth affects mussels growth. Mussel were seeded in summer, with the same mean total weight and shell length for both species. At the end of the experiment, shell length (SL), condition index and gonadosomatic index were compared over month, depth and species. Highly significant differences were found in shell length between month and depth and between month and species (p < 0.05). The linear relationship between the gonad weight and wet meat weight in M. chilensis present a higher gonad weight for the same wet meat weight than M. galloprovincialis. It can be concluded that at the end of the harvest size cultivation M. chilensis presents a greater gonad weight, condition index and gonadosomatic index.

Greenhouse gases, nutrients and the carbonate system in the Reloncaví Fjord (Northern Chilean Patagonia): Implications on aquaculture of the mussel, Mytilus chilensis, during an episodic volcanic eruption

This study investigates the immediate and mid-term effects of the biogeochemical variables input into the Reloncaví fjord (41°40′S; 72°23′O) as a result of the eruption of Calbuco volcano. Reloncaví is an estuarine system supporting one of the largest mussels farming production within Northern Chilean-Patagonia. Field-surveys were conducted immediately after the volcanic eruption (23–30 April 2015), one month (May 2015), and five months posterior to the event (September 2015). Water samples were collected from three stations along the fjord to determine greenhouse gases [GHG: methane (CH4), nitrous oxide (N2O)], nutrients [NO3−, NO2−, PO43−, Si(OH)4, sulphate (SO42−)], and carbonate systems parameters [total pH (pHT), temperature, salinity, dissolved oxygen (O2), and total alkalinity (AT)]. Additionally, the impact of physicochemical changes in the water column on juveniles of the produced Chilean blue mussel, Mytilus chilensis, was also studied. Following the eruption, a large phytoplankton bloom led to an increase in pHT, due to the uptake of dissolved-inorganic carbon in photic waters, potentially associated with the runoff of continental soil covered in volcanic ash. Indeed, high surface SO42− and GHG were observed to be associated with river discharges. No direct evidence of the eruption was observed within the carbonate system. Notwithstanding, a vertical pattern was observed, with an undersaturation of aragonite (ΩAr < 1) both in brackish surface (<3 m) and deep waters (>10 m), and saturated values in subsurface waters (3 to 7 m). Simultaneously, juvenile mussel shells showed maximized length and weight at 4 m depth. Results suggest a localized impact of the volcanic eruption on surface GHG, nutrients and short-term effects on the carbonate system. Optimal conditions for mussel calcification were identified within a subsurface refuge in the fjord. These specific attributes can be integrated into adaptation strategies by the mussel aquaculture industry to confront ocean acidification and changing runoff conditions.