Modelling the Spatial and Temporal Dynamics of Paralytic Shellfish Toxins (PST) at Different Scales: Implications for Research and Management

Harmful algal blooms, in particular recurrent blooms of the dinoflagellate Alexandrium catenella, associated with paralytic shellfish poisoning (PSP), frequently limit commercial shellfish harvests, resulting in serious socio-economic consequences. Although the PSP-inducing species that threaten the most vulnerable commercial species of shellfish are very patchy and spatially heterogeneous in their distribution, the spatial and temporal scales of their effects have largely been ignored in monitoring programs and by researchers. In this study, we examined the spatial and temporal dynamics of PSP toxicity in the clam (Ameghinomya antiqua) in two fishing grounds in southern Chile (Ovalada Island and Low Bay). During the summer of 2009, both were affected by an intense toxic bloom of A. catenella (up to 1.1 × 10⁶ cells L^-1). Generalized linear models were used to assess the potential influence of different environmental variables on the field detoxification rates of PSP toxins over a period of 12 months. This was achieved using a four parameter exponential decay model to fit and compare field detoxification rates per sampling site. The results show differences in the spatial variability and temporal dynamics of PSP toxicity, given that greater toxicities (+10-fold) and faster detoxification (20% faster) are observed at the Ovalada Island site, the less oceanic zone, and where higher amounts of clam are annually produced. Our observations support the relevance of considering different spatial and temporal scales to obtain more accurate assessments of PSP accumulation and detoxification dynamics and to improve the efficacy of fisheries management after toxic events.

Continental shelf off northern Chilean Patagonia: A potential risk zone for the onset of Alexandrium catenella toxic bloom?

Harmful Algal Blooms (HAB) pose a severe socio-economic problem worldwide. The dinoflagellate species Alexandrium catenella produces potent neurotoxins called saxitoxins (STXs) and its blooms are associated with the human intoxication named Paralytic Shellfish Poisoning (PSP). Knowing where and how these blooms originate is crucial to predict blooms. Most studies in the Chilean Patagonia, were focused on coastal areas, considering that blooms from the adjacent oceanic region are almost non-existent. Using a combination of field studies and modelling approaches, we first evaluated the role of the continental shelf off northern Chilean Patagonia as a source of A. catenella resting cysts, which may act as inoculum for their toxic coastal blooms. This area is characterized by a seasonal upwelling system with positive Ekman pumping during spring-summer, and by the presence of six major submarine canyons. We found out that these submarine canyons increase the vertical advection of bottom waters, and thus, significantly enhance the process of coastal upwelling. This is a previously unreported factor, among those involved in bloom initiation. This finding put this offshore area at high risk of resuspension of resting cysts of A. catenella. Here, we discuss in detail the physical processes promoting this resuspension.

Interannual variability in mesoscale distribution of Dinophysis acuminata and D. acuta in Northwestern Patagonian fjords

Dinophysis acuminata and D. acuta, which produce diarrheogenic toxins and pectenotoxins in southern Chile, display site-specific differences in interannual variability (2006 - 2018) in Reloncaví, Pitipalena and Puyuhuapi fjords (41 - 46 °S), Chilean Patagonia. Linear Models show decreasing trends in rainfall and river discharge. Latitudinal decreasing gradients in SST temperature and vertical salinity gradients were observed. A brackish water layer (FW salinity <11 psu), permanently present in Reloncaví, decreased in thickness with time in Pitipalena and was usually absent in Puyuhuapi, the only fjord where D. acuta reached bloom (>10³ cells L^‒1) densities every season. Dinophysis acuminata, associated with toxin profiles in shellfish that include only pectenotoxins, bloomed everywhere with a poleward increasing gradient. Absence of the FW layer provides a possible index of risk for D. acuta blooms. An apparent poleward shift of D. acuta populations, responsible for DSP outbreaks in Reloncaví in the 1970s, and the recent EU deregulation of pectenotoxins will have a positive impact on the mussel industry in Los Lagos Region. Changes to ongoing monitoring protocols to improve risk assessment capabilities are suggested.

Interactive effects of temperature and salinity on the growth and cytotoxicity of the fish-killing microalgal species Heterosigma akashiwo and Pseudochattonella verruculosa

Fish-killing blooms of Heterosigma akashiwo and Pseudochattonella verruculosa have been devastating for the farmed salmon industry, but in Southern Chile the conditions that promote the growth and toxicity of these microalgae are poorly understood. This study examined the effects of different combinations of temperature (12, 15, 18 °C) and salinity (10, 20, 30 psu) on the growth of Chilean strains of these two species. The results showed that the optimal growth conditions for H. akashiwo and P. verruculosa differed, with a maximum rate of 0.99 day^-1 obtained at 15 °C and a salinity of 20 psu for H. akashiwo, and a maximum rate of 1.06 day^-1 obtained at 18 °C and a salinity of 30 psu for P. verruculosa. Cytotoxic assays (2 × 10¹ - 2 × 10⁵ cell mL^-1; cells, filtrates, and cell lysates) performed at salinities of 20 and 30 psu showed a 100% reduction in the viability of embryonic fish cells exposed to intact cells of H. akashiwo and a 39% reduction following exposure to culture filtrates of P. verruculosa. Differences in the fish-killing mechanisms (direct cell contact vs. extracellular substances) and physiological traits of H. akashiwo and P. verruculosa explain the recent occurrence of very large blooms under contrasting (cold-brackish vs. hot-salty) extreme climate conditions in Chile.

Dynamics of Caligus rogercresseyi (Boxshall & Bravo, 2000) in farmed Atlantic salmon (Salmo salar) in southern Chile: Are we controlling sea lice?

Caligus rogercresseyi generates the greatest losses in the salmon industry in Chile. The relationship between salmon farming and sea lice is made up of various components: the parasite, host, environment and farming practices, which make it difficult to identify patterns in parasite population dynamics to define prevention and control strategies. The objectives of this study were to analyse and compare the effect of farming, sanitary practices and environmental variables on the abundance of gravid females (GF) and juveniles (JUV) of C. rogercresseyi on Salmo salar in three Salmon Neighborhood Areas (SNAs) in Region 10, south of Chile. Linear mixed-effects models of the negative binomial distribution were used to evaluate the effect of the different explanatory variables on GF and JUV. Productive variables were the key drivers explaining the abundance of GF and JUV. Results suggest that C. rogercresseyi is not controlled and JUV are persistent in the three SNAs, and sanitary practices do not control the dissemination of the parasite among sites. Environmental variables had a low impact on sea lice abundance. There is a need to perform analysis for modelling of parasite population dynamics to improve Integrated Pest Management, including changes in the governance to achieve an effective prevention and control.

Genetic risk assessment of thrombophilia in patients with adverse obstetric outcomes

OBJECTIVES

To investigate the incidence of inherited thrombophilias in patients with adverse obstetric outcomes and to compare detection rates of thrombophilias between standard blood tests and a novel genetic test.

METHODS

This is a case-control prospective study performed in Hospital Sant Joan de Déu in Barcelona, Spain. Cases had a history of intrauterine growth restriction requiring delivery before 34 weeks gestation, placental abruption before 34 weeks gestation, or severe preeclampsia. Controls had at least two normal, spontaneously conceived pregnancies at term, without complications or no underlying medical disease. At least 3 months after delivery, all case and control women underwent blood collection for standard blood tests for thrombophilias and saliva collection for the genetic test, which enables the diagnosis of 12 hereditary thrombophilias by analyzing genetic variants affecting different points of the blood coagulation cascade.

RESULTS

The study included 33 cases and 41 controls. There were no statistically significant differences between cases and controls in the standard blood tests for thrombophilias in plasma or the TiC test for genetic variables. One clinical-genetic model was generated using variables with the lowest P values: ABO, body mass index, C_rs5985, C_rs6025, and protein S. This model exhibited good prediction capacity, with an area under the curve of almost 0.7 (P <0.05), sensitivity of almost 67%, and specificity of 70%.

CONCLUSION

Although some association may exist between hypercoagulability and pregnancy outcomes, no significant direct correlation was observed between adverse obstetric outcomes and inherited thrombophilias when analyzed using either standard blood tests or the genetic test. Future studies with a larger sample size are required to create a clinical-genetic model that better discriminates women with a history of adverse pregnancy outcomes and an increased risk of poor outcomes in subsequent pregnancies.

Drastic difference in cadmium concentration in mussels (Mytilus chilensis) observed between seasons in natural bed and aquaculture systems in Chile

Globally, Chile is the second largest producer of mussels, with 99% of production concentrated in the inland sea of the Los Lagos Region, Southern Chile. This study reveals that seasons produce a drastic difference in the cadmium concentration (Cd) in marine mussels in bay, channel, and fjord ecosystems in this area. As the global mussel industry continues its rapid expansion, a complete understanding of cadmium pathways is critical in order to minimize the cadmium content in harvests. In this study, biweekly sampling was conducted in Chiloé (Southern Chile), during five consecutive seasons from June 2014 to November 2015. Cadmium in the soft tissues (ST) and in the content of the digestive gland (CDG) of Mytilus chilensis were investigated, in addition to resuspensions and seston to determine the effect of the seasons on metal bioassimilation capacity. In spring, the (Cd) between CDG and ST varied by approximately 2 mg Cd kg^-1 dry mass (DM). In summer and autumn, the (Cd) in CDG increased from 3 to 6 mg Cd kg^-1 while the (Cd) in ST decreased from 2.5 to 1.5 mg Cd kg^-1 DM. The three ecosystems showed the same cadmium bioconcentration trends in all seasons, revealing coherent global trends. These findings should caution the industry and coastal populations about the seasonal variability and intensity of cadmium metal transfer to biofilters, especially because of the adverse effects of cadmium consumption on human health. Additionally, this study found that mussels in natural beds concentrate more Cd (> 1 mg Cd kg^-1 DM) than in industrial facilities. Multiregression analysis showed and explained the cadmium in CDG for three ecosystems: channel (R² 0.9537), bay (R² 0.5962), and fjord (R² 0.4009). The independent variable nocturnal seston was able to explain the increase in cadmium.

Cadmium determination in Chilean blue mussels Mytilus chilensis: Implications for environmental and agronomic interest

Cadmium is present in agricultural soil composition and is assimilated by plants. The mussel industry generates large volumes of calcareous valves as a byproduct of processing in factories. This solid waste is ground, stored and disposed of in the form of agricultural supplies near production areas in almost all regions of the world. Cd content was recorded in these calcareous substrate by-products of industrial processes. In this study, mussel shells were investigated in three areas in the sea of Chile; two areas with high aquaculture activity and one in a non-production area. Mass Spectrometry was used for [Cd] readings. There are no significant differences (p=0.92) in [Cd] between the studied areas. Additionally, the [Cd] observed in valves was also similar relative to different depths. The low [Cd] observed in valves (~0.014±0.0049mgCdkg^-1 dry) suggests the potential use of this industrial byproduct in agricultural applications.