Search

In 2007, Chile reported its first case of infectious salmon anemia (ISA), caused by ISA virus (ISAV), in sea-cage reared Atlantic salmon. By 2010, the ISA disease outbreak was under control, but similarly to other countries, Chile continues to occasionally detect the non-pathogenic variant of ISAV (HPR0 ISAV). The Chilean salmon industry has been including gill samples in their routine ISAV monitoring program to improve the detection of HRP0 ISAV, which provides an opportunity to better assess the distribution of HPR0 ISAV and describe its occurrence in the Chilean marine aquaculture industry. A risk and a relative risk surface map were generated for the predominant regions of the Chilean aquaculture industry, and demonstrated areas of increased risk to HPR0 ISAV for the entire surveillance period. The observed occurrence and seasonal patterns of HPR0 ISAV were similar to those previously reported in Chile and in other countries. Further, spatiotemporal cluster analysis showed that the areas with a high-risk of HPR0 ISAV changed during the surveillance period (highly prevalent and causing non-clinical transient infections), and cases in clusters were initially observed within companies, followed by neighboring farms affecting other companies. Monitoring HPR0 ISAV in marine phase salmon production highlighted possible transmission patterns within the Chilean aquaculture industry and identified higher-risk areas associated with circulating orthomyxoviruses.

Effects induced on wild populations by recurrent environmental contamination may difficult the ecological risk assessment of punctual pollution events such as oil spills. Here, the issue was addressed by comparing the health status of Pomatoschistus microps populations from four NW Iberian estuaries, using an integrated chemical-biological monitoring. Despite high seasonal variability, the parameters measured discriminated estuaries with different contamination levels and associated biological effects with chemical and abiotic stress. The decreased health status of fish from polluted sites strengthens the need of considering pollution-induced background effects and seasonal variability when assessing impacts and risks of oil and other chemical spills.

The study presented here searched for the level of taxonomic resolution required to detect the effects of low-level chronic pollution on estuarine meiobenthic communities. Meiofauna from two sites, with special attention to harpacticoid copepods, was analysed at different taxonomic levels of aggregation using uni- and multivariate methods. Adaptation processes that could buffer biodiversity disruptions were also considered through the analysis of fitness-related and tolerance traits in the harpacticoid copepod Paronychocamptus nanus. Results showed that uni- and multivariate analyses could be inadequate when assessing subtle anthropogenic contamination. Instead, the assessment of inter-population differences in tolerance to the main source of stress rises as a required procedure if potential effects of this type of contamination are being investigated. Specifically, a 96 h acute toxicity test performed with populations from the affected site appears as a faster and reliable general tool to assess impacts of low-level chronic pollution in estuaries.

Potential for addressing ecological and physiological issues becomes severely limited when the organisms required to experimentally test specific hypotheses are absent from the study areas. This report describes a simple and inexpensive device for re-planting kelps into the lower intertidal zone of wave-swept rocky habitats, using Lessonia nigrescens Bory as a model organism. The device allows a wide range of plant sizes to be anchored by the holdfast. Transplanted kelps regenerated, re-attached to the substratum and overgrew the transplanting device. These results confirm the feasibility of using this technique to tackle a variety of highly relevant questions involving ecological, physiological, conservation, restoration and management issues.

The calanoid copepod Acartia tonsa has been recommended for standard toxicity tests due to its wide distribution, short life cycle and high reproductive potential. However, relatively high requirements of suitable animals (from 270 to 360 adults) need the development of cost-effective culture systems. In this study we evaluate the efficiency of a static-renewal culture for the calanoid copepod A. tonsa. Density-dependent survival, development and reproduction responses were assessed across three different stocking densities including: 500, 1000 and 2000 individuals l −1 . This culture system was developed in order to satisfy the needs for ecotoxicological testing, and thus it differs from large culture programs aimed to fulfil food requirements for fish larval aquaculture. Results showed that culture density had significant effects on copepod development and egg production but not on survival or egg viability. At the highest culture density tested, copepod development was delayed and egg production was low compared to lower culture densities. Relatively low reproduction rates at high stocking densities denoted suboptimal resource availability in terms of quantity and quality of food. Nevertheless, the proposed starting culture system of 1000 individuals l −1 ensured enough animals to carry out single-species toxicity tests and yielded enough eggs to ensure periodical restocking of new cultures

Short-term lethal and sublethal responses of the calanoid copepod Acartia tonsa to cypermethrin were compared with life-table responses to assess whether or not it is necessary to use exposure periods longer than 5 days to estimate demographic responses to stress. More specifically, by limiting exposure periods to sensitive age classes (eggs, nauplii, copepodids, and adults) and including measurements on survival, egg production, and feeding rates, it was possible to derive a short test design of similar sensitivity and ecological relevance as full life-table tests. Short-term exposures to cypermethrin reduced copepodid's feeding rates at concentrations well below those affecting egg production rates and survival of eggs and adult stages. Lethal effects on naupliar stages occurred at lower concentrations than any other effect observed on eggs and adults. Life-table sensitivities of the intrinsic rate of increase ( r(m)) to cypermethrin were similar to those observed in short-term exposures. More specifically, exposure to cypermethrin impaired r(m) responses at concentrations (7.4 ng x L(-1)) that also affected feeding and naupliar responses. Our results show that by quantifying and separating combined toxic effects on ecologically relevant individual life-history traits, it is possible to develop toxicity test designs of similar ecological relevance yet that are less labor-intensive and costly than existing demographic tests.

Acute effects of cypermethrin, a pesticide used to treat ectoparasite infestations of salmon, were assessed using the calanoid copepod Acartia tonsa. A. tonsa has been widely used for hazard assessment of chemicals in the marine environment using acute toxicity tests, but only with randomly selected adults, assuming a sex ratio of 1:1. The present study assesses the environmental hazard of cypermethrin by exposing nauplii and adult males and females, separately. Our results showed that the naupliar stages were 28 times more sensitive to cypermethrin than adults after 96 h of exposure, with LC50s of 0.005 microg x L(-1) and 0.142 microg x L(-1), respectively. Significant differences in sensitivity between sexes were only found during the first 24 h of exposure, with males being approximately twice as sensitive as females. The results of age-related variation in sensitivity are supported by studies with other species of copepods and toxicants, where the increased capacity of the adults for detoxification, the allometric differences in weight and size, and the molting process are given as explanations. Variation in sensitivity between sexes is discussed in terms of faster depuration rates in females through egg production and implications of feeding rate changes after 24 h of exposure. Our results suggested that standard toxicity test methods using A. tonsa are unsatisfactory because the most sensitive life stage is not included and sex-related differences in tolerance are not taken into account. We also found that cypermethrin caused significant mortality in Acartia at exposures concentrations from one to three orders of magnitudes lower than the recommended field treatment concentration for copepodic infestations.

Piscirickettsiosis (SRS) is an endemic bacterial disease of high economic importance and is the primary reason for antibiotic usage in the aquaculture industry in Chile. Understanding the epidemiology of this disease is important in order to develop better control strategies for the Chilean aquaculture industry. The objectives of this project were to 1) describe the epidemiology of SRS on Atlantic salmon and rainbow trout farms, and 2) to identify factors that impact the severity of SRS outbreaks. Special attention was given to vaccine strategies currently used by the industry. Production data from 14 Atlantic salmon farms (252 cages) and 11 rainbow trout farms (216 cages) that had completed their production cycles between 2010 and 2012 were investigated. Regression models were used to evaluate time-to-first outbreak of SRS and total mortality attributed to SRS mortality. The factors evaluated in our models were: vaccine type (control and 5 vaccines), smolt weight and cumulative mortality within the first 4 weeks in saltwater, season of smolt introduction, infection with other pathogens during the production cycle, SRS treatments, and total number of sea lice treatments. The prevalence of SRS-affected cages on infected farms was high for both species; however, outbreaks appeared more severe (i.e. higher mortalities) on rainbow trout farms. Onset of SRS outbreaks was, on average, for fish in different vaccine groups, between 2480 degree-days (dd) and 3829 dd for Atlantic salmon, and between 1696 dd and 2241 dd for rainbow trout. For both species, none of the vaccines evaluated completely prevented SRS, although there were significant variations in the time-to-first outbreak and the severity of SRS outbreaks associated with vaccines after controlling for farm effect and other predictors. Specifically, a booster vaccine strategy in Atlantic salmon had significantly lower mortalities associated with SRS and a delay in the onset of disease compared to several of the other vaccines evaluated. Whether the differences observed between vaccines are economically significant is unknown. In rainbow trout, time-to-first outbreak was significantly delayed for vaccinated fish compared to the unvaccinated fish after we controlled for other factors in our model; however, total SRS mortality of vaccinated rainbow trout was not significantly different than unvaccinated rainbow trout. Consistent for both species was that mortality during the first 4 weeks post-salt water entry was associated with time-to-outbreak of SRS, and this effect was dependent on the vaccine used.

Cadmium and copper accumulation by macroalgae was studied in a coastal area exposed to upwelling events and high levels of Cu, the latter resulting from mine disposals. Eight species were studied, and all had very high concentrations of Cd outside of the Cu-contaminated area. Cu in algal tissues was much higher in contaminated than in reference sites. High Cu appeared to suppress Cd bioaccumulation; Cd in algal tissues was much lower in the Cu-contaminated area than in the reference sites. Transplant experiments with Lessonia nigrescens revealed a depuration of Cd in individuals transplanted to areas with high Cu. However, Cd depuration occurs more slowly than Cu uptake. These differences suggest that while Cd and Cu are linked mechanistically, itis nota simple substitution. Overall, the work confirms that macroalgae are useful indicators of metal contamination and may be used as in situ biomonitors for labile forms of metals, like free Cu2+. However, antagonistic relationships between metals must be clearly understood in order to properly interpret their concentrations in macroalgae.

Copper effects on the early developmental gametophytic and sporophytic stages of the kelp Lessonia nigrescens were tested in gradients of increasing concentrations of ASV-labile copper. The results demonstrated a high sensitivity to copper of all life-history stages of the alga, where even the lowest tested concentration affected spore release as well as their subsequent settlement. More significant, concentrations higher than 7.87 μg L −1 totally interrupted the development of the spores after they settle. This effect led to a failure in the formation of male and female gametophytes and, as a consequence, to a complete disruption of the normal life cycle of the kelp. Thus, we suggest that the absence of L. nigrescens from copper-enriched environments results from the high sensitivity of its early life cycle stages, which limits growth and maturation of the gametophytic microscopic phase and, as a consequence, prevents development of the macroscopic sporophytic phase.

In earlier single-species toxicity tests we showed the negative effects on the calanoid copepod Acartia tonsa upon exposure to cypermethrin, a pesticide used in treatment for sea lice in salmon farming. In the present study we assessed effects at a higher level of biological organization and under a more realistic exposure scenario using mesocosms. The results showed that simulated field studies (SFSs) could be conducted with the mesocosms designed here. When cypermethrin was applied inside these mesocosms, its concentration decreased exponentially following a first-order kinetics model. The pesticide immediately reduced zooplankton density and biodiversity not only directly, by killing copepods, but also indirectly, by increasing the numbers of rotifers. Zooplankton density recovered after treatment, but zooplankton biodiversity remained altered. In an open environment, however, the rapid dissipation of the pesticide, coupled with population processes of compensation, migration, and immigration, may lead to recovery of the affected zooplankton communities.

Survival responses of adult stages of the calanoid copepod A. tonsa during and after pulse exposures to cypermethrin were used to evaluate the environmental risks of cypermethrin treatments in the marine environment. To control sea lice, whole cages of salmon are exposed to cypermethrin over 1 h, after which the effluent is released into the environment and subsequently dissipates. Here we simulate this short presence of the chemical in the water column. The present study revealed that delayed toxicity in A. tonsa adults, here expressed as decreased survival, occurred following short term pulse exposures to cypermethrin. Persistent, sensitive responses to cypermethrin during and after pulse exposures of 24 h were similar to those reported in conventional acute tests, suggesting that damage caused by accumulated levels of cypermethrin during the first 24 h of exposure could explain long-term toxicity responses in A. tonsa. Delayed toxicity following 1 h pulse exposures to cypermethrin impaired male survival and therefore changed copepod sex ratios. The proposed delayed toxicity tests were considered sensitive and suggest potentially detrimental effects of cypermethrin on copepod populations within the vicinity of the cages. By monitoring toxic responses following pulsed exposures, delayed toxicity tests are especially suitable to assess environmental risks of poorly water-soluble substances that dissipate rapidly within the water column.