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The sea walnut, Mnemiopsis leidyi, has invaded and expanded throughout the whole Mediterranean Sea basin. Large blooms were recorded also in the Venice Lagoon (Italy), an ecosystem rich with biodiversity which supports multiple services, including artisanal fishery production. To investigate M. leidyi impacts on lagoon artisanal fisheries, we combined fishers’ local ecological knowledge, fishery landing time series analysis, and field sampling. Firstly, we interviewed artisanal fishers to date the blooms of M. leidyi. Secondly, we analyzed long-term fishery landings records to detect whether changes in landings quantity and composition were related to the ctenophore invasion. Thirdly, we sampled catches of the lagoon fyke nets. This interdisciplinary approach overcame the weaknesses of single methodologies and allowed us to reconstruct the temporal phases of M. leidyi invasion in the Venice Lagoon. Moreover, our results indicate that the lagoon landings significantly declined with the blooms, paralleled by the increase of water temperature. Finally, we showed that the mechanical obstruction of the nets, caused by the massive ctenophore blooms, strongly impacts fishing activities. Our results are a first step in assessing the short and long-term impacts of this invasive species on lagoon ecosystems, including its socioeconomic consequences, whose better understanding is fundamental to inform mitigation and adaptation measures. [ABSTRACT FROM AUTHOR]

Fisheries worldwide face uncertain futures as climate change manifests in environmental effects of hitherto unseen strengths. Developing climate-ready management strategies traditionally requires a good mechanistic understanding of stock response to climate change in order to build projection models for testing different exploitation levels. Unfortunately, model-based projections of fish stocks are severely limited by large uncertainties in the recruitment process, as the required stock-recruitment relationship is usually not well represented by data. An alternative is to shift focus to improving the decision-making process, as postulated by the decision-making under deep uncertainty (DMDU) framework. Robust Decision Making (RDM), a key DMDU concept, aims at identifying management decisions that are robust to a vast range of uncertain scenarios. Here we employ RDM to investigate the capability of North Sea cod to support a sustainable and economically viable fishery under future climate change. We projected the stock under 40,000 combinations of exploitation levels, emission scenarios and stock-recruitment parameterizations and found that model uncertainties and exploitation have similar importance for model outcomes. Our study revealed that no management strategy exists that is fully robust to the uncertainty in relation to model parameterization and future climate change. We instead propose a risk assessment that accounts for the trade-offs between stock conservation and profitability under deep uncertainty., (© 2024. The Author(s).)

Ecological resilience is the capability of an ecosystem to maintain the same structure and function and avoid crossing catastrophic tipping points (i.e. undergoing irreversible regime shifts). While fundamental for management, concrete ways to estimate and interpret resilience in real ecosystems are still lacking. Here, we develop an empirical approach to estimate resilience based on the stochastic cusp model derived from catastrophe theory. The cusp model models tipping points derived from a cusp bifurcation. We extend cusp in order to identify the presence of stable and unstable states in complex natural systems. Our Cusp Resilience Assessment (CUSPRA) has three characteristics: (i) it provides estimates on how likely a system is to cross a tipping point (in the form of a cusp bifurcation) characterized by hysteresis, (ii) it assesses resilience in relation to multiple external drivers and (iii) it produces straightforward results for ecosystem-based management. We validate our approach using simulated data and demonstrate its application using empirical time series of an Atlantic cod population and marine ecosystems in the North Sea and the Mediterranean Sea. We show that Cusp Resilience Assessment is a powerful method to empirically estimate resilience in support of a sustainable management of our constantly adapting ecosystems under global climate change.

Recovery of depleted fish stocks is an important goal for fisheries management and crucial to sustain important ecosystem functions as well as global food security. Successful recovery requires adjusting fishing mortality to stock productivity but can be prevented or inhibited by additional anthropogenic impacts such as climate change. Despite management measures to recover fish stocks being in place in legislations such as the European Union´s Common Fisheries Policy (CFP), recovery can be hindered by the occurrence of regime shift dynamics. Such non-linear discontinuous dynamics imply tipping points and bear the characteristics of abrupt change, hysteresis and non-stationary functional relationships. We here used the recent reform of the CFP as a natural experiment to investigate the existence of regime shift dynamics and its potential effects on the recovery potential on six strongly fished or even depleted commercial fish stocks in the North Sea. Using a set of statistical approaches we show that regime shift dynamics exist in all six fish stocks as a response to changes in fishing pressure and temperature. Our results furthermore demonstrate the context-dependence of such dynamics and hence the ability of management measures to rebuild depleted fish stocks, leading to either failed recovery or positive tipping., (© 2023. The Author(s).)

Cumulative human pressures and climate change can induce nonlinear discontinuous dynamics in ecosystems, known as regime shifts. Regime shifts typically imply hysteresis, a lacking or delayed system response when pressures are reverted, which can frustrate restoration efforts. Here, we investigate whether the northern Adriatic Sea fish and macroinvertebrate community, as depicted by commercial fishery landings, has undergone regime shifts over the last 40 years, and the reversibility of such changes. We use a stochastic cusp model to show that, under the interactive effect of fishing pressure and water warming, the community reorganized through discontinuous changes. We found that part of the community has now reached a new stable state, implying that a recovery towards previous baselines might be impossible. Interestingly, total landings remained constant across decades, masking the low resilience of the community. Our study reveals the importance of carefully assessing regime shifts and resilience in marine ecosystems under cumulative pressures and advocates for their inclusion into management., (© 2022 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.)

Understanding tipping point dynamics in harvested ecosystems is of crucial importance for sustainable resource management because ignoring their existence imperils social-ecological systems that depend on them. Fisheries collapses provide the best known examples for realizing tipping points with catastrophic ecological, economic and social consequences. However, present-day fisheries management systems still largely ignore the potential of their resources to exhibit such abrupt changes towards irreversible low productive states. Using a combination of statistical changepoint analysis and stochastic cusp modelling, here we show that Western Baltic cod is beyond such a tipping point caused by unsustainable exploitation levels that failed to account for changing environmental conditions. Furthermore, climate change stabilizes a novel and likely irreversible low productivity state of this fish stock that is not adapted to a fast warming environment. We hence argue that ignorance of non-linear resource dynamics has caused the demise of an economically and culturally important social-ecological system which calls for better adaptation of fisheries systems to climate change., (© 2021. The Author(s).)

Collapses and regime changes are pervasive in complex systems (such as marine ecosystems) governed by multiple stressors. The demise of Atlantic cod ( Gadus morhua) stocks constitutes a text book example of the consequences of overexploiting marine living resources, yet the drivers of these nearly synchronous collapses are still debated. Moreover, it is still unclear why rebuilding of collapsed fish stocks such as cod is often slow or absent. Here, we apply the stochastic cusp model, based on catastrophe theory, and show that collapse and recovery of cod stocks are potentially driven by the specific interaction between exploitation pressure and environmental drivers. Our statistical modelling study demonstrates that for most of the cod stocks, ocean warming could induce a nonlinear discontinuous relationship between fishing pressure and stock size, which would explain hysteresis in their response to reduced exploitation pressure. Our study suggests further that a continuing increase in ocean temperatures will probably limit productivity and hence future fishing opportunities for most cod stocks of the Atlantic Ocean. Moreover, our study contributes to the ongoing discussion on the importance of climate and fishing effects on commercially exploited fish stocks, highlighting the importance of considering discontinuous dynamics in holistic ecosystem-based management approaches, particularly under climate change.

[This corrects the article DOI: 10.1371/journal.pone.0188205.].

Understanding spatio-temporal dynamics of biotic communities containing large numbers of species is crucial to guide ecosystem management and conservation efforts. However, traditional approaches usually focus on studying community dynamics either in space or in time, often failing to fully account for interlinked spatio-temporal changes. In this study, we demonstrate and promote the use of tensor decomposition for disentangling spatio-temporal community dynamics in long-term monitoring data. Tensor decomposition builds on traditional multivariate statistics (e.g. Principal Component Analysis) but extends it to multiple dimensions. This extension allows for the synchronized study of multiple ecological variables measured repeatedly in time and space. We applied this comprehensive approach to explore the spatio-temporal dynamics of 65 demersal fish species in the North Sea, a marine ecosystem strongly altered by human activities and climate change. Our case study demonstrates how tensor decomposition can successfully (i) characterize the main spatio-temporal patterns and trends in species abundances, (ii) identify sub-communities of species that share similar spatial distribution and temporal dynamics, and (iii) reveal external drivers of change. Our results revealed a strong spatial structure in fish assemblages persistent over time and linked to differences in depth, primary production and seasonality. Furthermore, we simultaneously characterized important temporal distribution changes related to the low frequency temperature variability inherent in the Atlantic Multidecadal Oscillation. Finally, we identified six major sub-communities composed of species sharing similar spatial distribution patterns and temporal dynamics. Our case study demonstrates the application and benefits of using tensor decomposition for studying complex community data sets usually derived from large-scale monitoring programs.

How have North Sea skate and shark assemblages changed since the early 20th century when bottom trawling became widespread, whilst their environment became increasingly impacted by fishing, climate change, habitat degradation and other anthropogenic pressures? This article examines long-term changes in the distribution and occurrence of the elasmobranch assemblage of the southern North Sea, based on extensive historical time series (1902-2013) of fishery-independent survey data. In general, larger species (thornback ray, tope, spurdog) exhibited long-term declines, and the largest (common skate complex) became locally extirpated (as did angelshark). Smaller species increased (spotted and starry ray, lesser-spotted dogfish) as did smooth-hound, likely benefiting from greater resilience to fishing and/or climate change. This indicates a fundamental shift from historical dominance of larger, commercially valuable species to current prevalence of smaller, more productive species often of low commercial value. In recent years, however, some trends have reversed, with the (cold-water associated) starry ray now declining and thornback ray increasing. This shift may be attributed to (i) fishing, including mechanised beam trawling introduced in the 1960s-1970s, and historical target fisheries for elasmobranchs; (ii) climate change, currently favouring warm-water above cold-water species; and (iii) habitat loss, including potential degradation of coastal and outer estuarine nursery habitats. The same anthropogenic pressures, here documented to have impacted North Sea elasmobranchs over the past century, are likewise impacting shelf seas worldwide and may increase in the future; therefore, parallel changes in elasmobranch communities in other regions are to be expected., (© 2016 Crown Copyright. Global Change Biology published by John Wiley & Sons Ltd.)

The results of a randomized, multicenter clinical trial of immunoprophylaxis of post-operative infections with intravenous Immunoglobulins (IVIG) (Sandoglobulin) in "septic-risk" patients undergoing surgery for gastrointestinal cancer are presented. "Septic-risk" patients were selected by an original multiparametric test based on delayed hypersensitivity skin testing and serum protein electrophoretic sub-fractions. This screening test had shown 76% positive predictivity in a previous validation assessment. In the present study, 159 "septic-risk" patients were selected prospectively from 369 patients undergoing colo-rectal (colon) and other kinds of gastrointestinal (non-colon) oncologic surgery: 80 "septic-risk" patients were included in the colon and 79 in the non-colon group. Immunoprophylaxis with IVIG (15 g on the day prior to operation, on the 1st and 5th postoperative days) was randomly associated with antibiotic prophylaxis (cefoxitin: 2 g one hour prior to, followed by 2 g at the end of operation plus 2 g every six hours for 24 hours) in colon surgery while the prophylactic schedule in non-colon surgery was only based on random administration of IVIG, at the same dosage as in the colon group. There was a clear-cut reduction of post-operative infections both in colon and non-colon "septic-risk" patients who had IVIG prophylaxis; in the colon group, 37 and 21 infections (P < 0.004) in antibiotic (A) versus IVIG plus antibiotic (IVIG + A) subset, respectively; in the non-colon group, 33 and 19 infections (P < 0.01) in control (C) versus (IVIG) subset, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Sixty-two consecutive septic surgical patients receiving standard multimodal intensive care unit treatment who developed a sepsis score of 20 or greater (day 0) were randomized to receive 0.4 g/kg of either intravenous IgG (29 patients) or human albumin (controls; 33 patients), repeated on days +1 and +5, in a prospective, double-blind, multicenter study. The two groups were similar in age, initial sepsis scores, and acute physiology and chronic health evaluation II score. A significantly lower mortality was recorded in the IgG-treated group (38%) than in controls (67%). Septic shock was the cause of death in 7% of IgG-treated patients and in 33% of controls. The results of this study indicate that high-dose IgG improves survival and decreases death from septic shock in surgical patients with a sepsis score of 20 or greater.

The effect of thymopentin treatment on the immune defects in drug addicts with persistent generalized lymphadenopathy and HTLV-III infection was investigated. Thymopentin was administered subcutaneously at two different dose schedules: 50 mg three times a week for 3 weeks (first cycle) and 50 mg/week for 3 months (second cycle). After the first cycle an increased number of OKT4+ lymphocytes and an improvement of PWM-induced blastogenesis and IgG synthesis in vitro was observed. The second cycle was unable to modify the same immune parameters in vitro. The treatment had no effect on the PHA responsiveness and on PHA-induced interleukin 2 production. The significance and the prognostic value of these findings are discussed in terms of the clinical evolution of the syndrome.

The effect of thymopentin (TP-5) treatment on lymphocyte immune functions has been investigated in immunocompromised aged subjects. TP-5 was able to improve the cutaneous delayed hypersensitivity (CDH) to recall antigens and the proliferative response to phytohemagglutinin (PHA), concanavalin A, and Pokeweed (PWM) as well as the PHA-induced interleukin-2 (Il-2) production. On the other hand, no detectable changes were induced by TP-5 treatment either on PWM-induced immunoglobulin synthesis or on lymphocyte subsets identified by monoclonal antibodies. Our results suggest that the enhancement of Il-2 synthesis might be a crucial mechanism of the immunopharmacological action of TP-5 in aging humans.

We studied a group of healthy elderly subjects (satisfying the SENIEUR Protocol admission criteria), chosen as a model of age-associated immune deficiency on the basis of their reduced skin reactivity to recall antigens. Results show that aged subjects, taken as a whole, display impaired T-cell functions: reduced blastogenetic responses to mitogens, IL-2 production, responsiveness to exogenous IL-2, and percentage of Tac positive blasts. However, the age-associated immune defect shows a wide range of impairment, even in a relatively homogeneous group of anergic/hypoergic subjects. In fact, a considerable proportion of our elderly subjects displays responses comparable with those of adult controls. These observations suggest that (a) immune deficiency is not a characteristic of aging per se; (b) cutaneous delayed hypersensitivity is not a criterion sensitive enough to identify people with age-associated immune deficit; and (c) more than one test is required to evaluate T-cell impairment in aging.

Peripheral blood mononuclear cells (PBMC) from patients with Essential Mixed Cryoglobulinemia (EMC) were studied for their ability to synthesize polyclonal IgM and rheumatoid factor (RF) IgM in vitro. Our results indicate: that EMC-PBMC produce smaller amounts of polyclonal IgM but higher quantities of IgM-RF than normal PBMC after pokeweed mitogen (PWM) or Staphylococcus aureus activation, so that the IgM-RF to total IgM ratio is significantly greater in EMC than in normal cultures; that enriched EMC-B lymphocytes display a significantly higher spontaneous synthesis of IgM-RF than normal B lymphocytes and that the IgM-RF B cell clones are receptive to T cell regulation. Taken together these findings suggest an expansion of B cell clones committed to IgM RF production and the presence in peripheral blood of differentiated B lymphocytes capable of secreting IgM-RF in EMC.

The T-cell requirement for the B-lymphocyte immunoglobulin synthesis induced by Pokeweed mitogen (PWM) and by Staphylococcus aureus Cowan I (SAC) was investigated. We found that the PWM induced B-cell activation was controlled by an absolute Mitomycin-C resistant T-cell helper activity and by a Mitomycin-C sensible T-cell suppressor activity. On the other hand the SAC induced B-cell activation was less thymus dependent and was not influenced by Mitomycin-C treated or irradiated T cells. The different T-cell requirement could be an expression of different responding B-cell subpopulations.