Natural Marine Ecosystems Research Articles

The Impact Of Sea Sand Mining On The Environment And Economy In Bawean Island

This study analyzes the impact of sea sand mining on the environment and local economy in Bawean Island. Located in the Java Sea and part of Gresik Regency, East Java Province, Bawean Island is renowned for its biodiversity and natural beauty. Both legal and illegal sea sand mining have caused various problems, including increased coastal abrasion and erosion, degradation of seawater quality, damage to coral reef ecosystems and mangrove forests, and beach pollution. The economic impacts include a decline in fish catches, reduced tourism appeal, and social conflicts between pro-environment communities and mining parties. The research methodology used is qualitative descriptive, employing literature review for data collection. The findings indicate that sea sand mining results in serious ecosystem damage and adversely affects the economic well-being of local communities. To address these issues, recommended measures include reviewing local regulations, reassessing environmental permits, revoking non-compliant mining licenses, developing alternative economies, planting mangroves, promoting the benefits of mangroves, and adopting an interagency approach. This study emphasizes the importance of sustainable natural resource management and marine ecosystem protection to ensure the well-being of Bawean Island's communities.

Multistress Interplay: Time and Duration of Ocean Acidification Modulate the Toxicity of Mercury and Other Metals.

The current understanding of multistress interplay assumes stresses occur in perfect synchrony, but this assumption is rarely met in the natural marine ecosystem. To understand the interplay between nonperfectly overlapped stresses in the ocean, we manipulated a multigenerational experiment (F0-F3) to explore how different temporal scenarios of ocean acidification will affect mercury toxicity in a marine copepod Pseudodiaptomus annandalei. We found that the scenario of past acidification aggravated mercury toxicity but current and persistent acidification mitigated its toxicity. We specifically performed a proteomics analysis for the copepods of F3. The results indicated that current and persistent acidification initiated the energy compensation for development and mercury efflux, whereas past acidification lacked the barrier of H+ and had dysfunction in the detoxification and efflux system, providing a mechanistic understanding of mercury toxicity under different acidification scenarios. Furthermore, we conducted a meta-analysis on marine animals, demonstrating that different acidification scenarios could alter the toxicity of several other metals, despite evidence from nonsynchronous scenarios remaining limited. Our study thus demonstrates that time and duration of ocean acidification modulate mercury toxicity in marine copepods and suggests that future studies should move beyond the oversimplified scenario of perfect synchrony in understanding multistress interaction.

Dinoflagellate Proton-Pump Rhodopsin Genes in Long Island Sound: Diversity and Spatiotemporal Distribution.

Microbial proton-pump rhodopsin (PPR)-based phototrophy, a light-harvesting mechanism different from chlorophyll-based photosystems, may contribute significantly to solar energy entry into the marine ecosystem. PPR transforms solar energy into cellular energy that is used for various metabolic processes in the cells or flagellar movement. Although rhodopsins or their encoding genes have been documented in a wide phylogenetic range of cultured dinoflagellates, information is limited about how widespread and how spatiotemporally dynamical dinoflagellate PPR (DiPPR) are in natural marine ecosystems. In this study, we investigated DiPPR in Long Island Sound (LIS), a temperate estuary of the Atlantic Ocean between Connecticut and Long Island, New York, USA. We isolated six novel full-length dinoflagellate proton-pump rhodopsin cDNAs, expanding the DiPPR database that is crucial to PPR research. Based on these new sequences and existing sequences of DiPPR, we designed primers and conducted quantitative PCR and sequencing to determine the abundance and diversity of DiPPR genes spatially and temporally throughout a year in the water samples collected from LIS. DiPPR genes were found year-round and throughout LIS but with higher abundances in the eutrophic Western Sound and in April and July. The gene diversity data suggest that there are at least five distinct rhodopsin-harboring groups of dinoflagellates throughout the year. The abundance of DiPPR genes, measured as copy number per mL of seawater, appeared not to be influenced by water temperature or nitrogen nutrient concentration but exhibited weak negative correlations with orthophosphate concentration and salinity and a positive correlation with the abundance of DiPPR-harboring dinoflagellates. This first quantitative profiling of PPR in natural plankton reveals the prevalence and dynamics of this plastid-independent photoenergy harvesting mechanism in a temperate estuary and provides efficient DiPPR primers potentially useful for future research. Furthermore, this study shed light on the potential role of DiPPR in phosphor nutrition and dinoflagellate population, which warrants further studies.

A Historical Plankton Index: Zooplankton abundance in the North Sea since 800 CE

The North Sea region boasted one of the world’s most important fisheries for many centuries. Climate directly and indirectly influences the development and survival of many important pelagic fish in the North Sea ecosystem. One indirect influence is the food availability in the form of phyto- and zooplankton abundance, which is strongly controlled by environmental factors. One of these environmental factors is local sea surface temperatures. A negative correlation between zooplankton abundance and sea surface temperature is well established for the epeiric sea on the European continental shelf. Continuous temporal observations of North Sea zooplankton production only exist since 1958. Therefore we developed a Historical Plankton Index (HPI) from 800 CE onwards to extend our record of temperature-driven zooplankton abundance in the North Sea over a multi-centennial time scale. For this we used the North Atlantic temperature reconstructions and associations between zooplankton abundance and contemporary sea surface temperatures established applying a General Additive Modelling (GAM) approach. We then examined the association between the HPI and historical landings from the Dutch commercial herring fishery in the 17th century to test the utility of our HPI. We examine the potential influence of food availability (in terms of zooplankton abundance) on the fishery, the evolution of which is often only considered in terms of human influences such as conflict, fishing gear and demand for fish as a commodity. We find that under certain conditions the HPI can explain 20% of the variability in Dutch herring landings. This highlights the importance of developing long-term and large-scale indices of natural marine ecosystem dynamics to understand the historical fortunes of the commercial fishing industry. The results are directly relevant to the United Nations’ sustainable development goal 14 – life below water.

Temperature sensitivity of the interspecific interaction strength of coastal marine fish communities

The effects of temperature on interaction strengths are important for understanding and forecasting how global climate change impacts marine ecosystems; however, tracking and quantifying interactions of marine fish species are practically difficult especially under field conditions, and thus, how temperature influences their interaction strengths under field conditions remains poorly understood. We herein performed quantitative fish environmental DNA (eDNA) metabarcoding on 550 seawater samples that were collected twice a month from 11 coastal sites for 2 years in the Boso Peninsula, Japan, and analyzed eDNA monitoring data using nonlinear time series analytical tools. We detected fish–fish interactions as information flow between eDNA time series, reconstructed interaction networks for the top 50 frequently detected species, and quantified pairwise, fluctuating interaction strengths. Although there was a large variation, water temperature influenced fish–fish interaction strengths. The impact of water temperature on interspecific interaction strengths varied among fish species, suggesting that fish species identity influences the temperature effects on interactions. For example, interaction strengths that Halichoeres tenuispinis and Microcanthus strigatus received strongly increased with water temperature, while those of Engraulis japonicus and Girella punctata decreased with water temperature. An increase in water temperature induced by global climate change may change fish interactions in a complex way, which consequently influences marine community dynamics and stability. Our research demonstrates a practical research framework to study the effects of environmental variables on interaction strengths of marine communities in nature, which would contribute to understanding and predicting natural marine ecosystem dynamics.

Temperature sensitivity of the interspecific interaction strength of coastal marine fish communities.

The effects of temperature on interaction strengths are important for understanding and forecasting how global climate change impacts marine ecosystems; however, tracking and quantifying interactions of marine fish species are practically difficult especially under field conditions, and thus, how temperature influences their interaction strengths under field conditions remains poorly understood. We herein performed quantitative fish environmental DNA (eDNA) metabarcoding on 550 seawater samples that were collected twice a month from 11 coastal sites for 2 years in the Boso Peninsula, Japan, and analyzed eDNA monitoring data using nonlinear time series analytical tools. We detected fish-fish interactions as information flow between eDNA time series, reconstructed interaction networks for the top 50 frequently detected species, and quantified pairwise, fluctuating interaction strengths. Although there was a large variation, water temperature influenced fish-fish interaction strengths. The impact of water temperature on interspecific interaction strengths varied among fish species, suggesting that fish species identity influences the temperature effects on interactions. For example, interaction strengths that Halichoeres tenuispinis and Microcanthus strigatus received strongly increased with water temperature, while those of Engraulis japonicus and Girella punctata decreased with water temperature. An increase in water temperature induced by global climate change may change fish interactions in a complex way, which consequently influences marine community dynamics and stability. Our research demonstrates a practical research framework to study the effects of environmental variables on interaction strengths of marine communities in nature, which would contribute to understanding and predicting natural marine ecosystem dynamics.

Eco-creative nature-based solutions to transform urban coastlines, local coastal communities and enhance biodiversity through the lens of scientific and Indigenous knowledge

Abstract Increasing anthropogenic pressure on the sea and alteration of coastscapes challenge the functioning of marine ecosystems and long-term reliance on blue economies, especially for developing southern economies. The structural hardening of shores can result in ecological disruptions, with cascading effects on the wellbeing and livelihoods of marginalised groups who depend on marine resources. Mitigation, adaptation and rehabilitation options for coastal developments should include innovative, socially responsible solutions to be used to modify shorelines and ensure long-term functionality of metropolitan coastal ecosystems. Nature-based innovations are being developed to improve surrogacy for natural marine ecosystems. The co-creation of nature-based structures, entailing partnerships between scientists and a local rural community is currently being considered in South Africa and we present this regional case study as a transdisciplinary framework for research in nature-based, ecological engineering of coastal systems. Novel transdisciplinary approaches include ecomusicological interventions, where traditional cultural expressions (TCEs) create opportunities for transgressive pedagogy. This step aims to ensure that the knowledge gathered through nature-based scientific research remains a part of community developed Indigenous knowledge systems. The merging of innovative, eco-creative approaches and TCEs has the potential to sustainably and ethically improve the functioning and diversity of coastal urban habitats. This review tackles the potential of transdisciplinary settings to transform urban coastlines using “low-tech” engineering and Indigenous eco-creative innovations to pedagogy, to benefit the people and biological communities as well as reduce social and gender inequalities.

Between the devil and the deep blue sea: Trends, drivers, and impacts of coastal reclamation in Malaysia and way forward

Cities all over the world are edging further into the ocean. Coastal reclamation is a global conservation issue with implications for ocean life, ecosystems, and human well-being. Using Malaysia as a case study, the coastal reclamation trends over three decades (1991–2021) were mapped using Landsat images and Normalized Difference Water Index (NDWI) via the Google Earth Engine platform. The changes in drivers and impacts of these coastal expansions throughout the decades were also reviewed. Twelve out of the 14 states in Malaysia had planned, active, or completed reclamations on their shorelines. Between 1991 and 2021, an absolute area of 82.64 km2 has been or will be reclaimed should all the projects be completed. The most reported driver for coastal expansion in Malaysia is for development and modernization (41 %), followed by rise in human population (20 %), monetary gains from the development of prime land (15 %), and agriculture and aquaculture activities (9 %). Drivers such as reduction of construction costs, financial advantage of prime land, oil and gas, advancement of technology, and tourism (Malaysia My Second Home (MM2H)) had only started occurring within the last decade, while others have been documented since the 1990's. Pollution is the most reported impact (24 %) followed by disruption of livelihoods, sources of income and human well-being (21 %), destruction of natural habitats (17 %), decrease in biodiversity (11 %), changes in landscapes (10 %), erosion / accretion (8 %), threat to tourism industry (6 %), and exposure to wave surges (3 %). Of these, changes in landscape, shoreline alignment, seabed contour, and coastal groundwater, as well as wave surges had only started to surface as impacts in the last two decades. Efforts to protect existing natural coastal and marine ecosystems, restore degraded ones, and fund endeavours that emphasize nature is needed to support sustainable development goals for the benefit of future generations.

Artificial Coral Reef Growth Media Model Engineering from Ceramic

The experiment on the artificial coral reef was conducted at BTIKK using ceramic body mass code BL1. This engineering was carried out in two steps, the first step was making the design of the growth media, and the second step was testing the mass of the ceramic body and making the growth media model. The hexagonal design was used beginning from the design concept that applies geometric shapes with many sides, making it easier to arrange the formation under the sea. Aesthetically, the hexagonal shape can represent a design concept. It resulted from integration in the design of coral reef planting media with natural marine ecosystems and can produce new experiences and impressions to attract people's attention to pay more attention to the preservation of coral reefs. The assessment of fired shrinkage, water absorption, and apparent porosity on body mass for making the growth medium model was tested on 15 test pieces. The average value of fired shrinkage on 900°C temperature fired test pieces is 1.3%, the average water absorption is 19.7%, and the apparent porosity is 32.9%. Their value could be used to make artificial coral reef growth media.

Ecosystem turnover in an urbanized subtropical seascape driven by climate and pollution

Natural and anthropogenic factors shape present-day benthic marine ecosystems. Understanding their combined influence on benthic communities is limited, however, by a lack of biological monitoring. Using a conservation paleobiology approach, this study establishes biological baselines and assesses the effects of natural and anthropogenic environmental change on benthic communities in an urbanized subtropical seascape. We compared subsurface (“past”, covering approximately the last 50–100 years) and surface ("present", covering approximately the last 5 years) faunal assemblages in sediment grab samples in Hong Kong, one of the busiest ports and urbanized coastal areas in the world. Results show that both natural (climate, monsoon) and anthropogenic factors (metal pollution, damming) were associated with recent faunal changes (dissimilarities between subsurface and surface faunal assemblages). Changes in freshwater and sediment discharge from the Pearl River due to monsoon rains and dams produced a strong west-east gradient in the turnover of rare species. Pollution from metals resulted in the turnover of abundant and dominant species in the central part of Hong Kong. Examining these data in the context of published results from other urbanized coastal areas around the world suggests that metal pollution may be an important and understudied factor, responsible for benthic turnover in regions where pollution levels exceed thresholds for sediment toxicity.

Monthly anomalies of sea surface chlorophyll-a concentration in the Khanh Hoa waters of Vietnam related to ENSO phenomenon

Based on the monthly averaged sea surface chlorophyll-a concentration data continuously for more than 17 years (Jul. 2002–Dec. 2019), the analyzed results show that the averaged chlorophyll-a concentration in Khanh Hoa waters was 0.58 mg/m3, and the monthly average variation was ± 0.14 mg/m3 (that is equivalent to about ± 24%). Under the impact of ENSO phenomena, in the years when the double La Niña events occurred (two consecutive years in the La Nina event occurs), the chlorophyll-a anomaly index fluctuated from -0.99 mg/m3 to 1.62 mg/m3. These are very strong fluctuation levels, corresponding to the decrease or increase in chlorophyll-a concentration from 86% to 279%. In the El Niño years, the fluctuations of chlorophyll-a concentration were little affected unless the two previous years in which the double La Niña event occurred. These fluctuations have significantly impact nutritional resources and water quality because chlorophyll-a concentration is one of the key indices in studying the health status of any natural marine ecosystem. In addition, chlorophyll-a concentration in Khanh Hoa waters often varies between seasons. The averaged chlorophyll-a concentration reaches its maximum value in the winter, then decreases gradually in the spring and usually reaches the minimum value in the summer, then rises gradually again in the autumn.

Reverse the declining course: A risk assessment for marine and fisheries policy strategies in Europe from current knowledge synthesis

An ecosystem approach to fisheries management is being developed around the world in an attempt to consider components of marine ecosystems other than just the exploited stocks. While numerous scientific studies on the consequences of fishing on marine ecosystems exist, most of their findings are too uncertain and fail to quantify the magnitude of the effects they describe to be used reliably in an environmental management and marine policy-making realm. To circumvent such a knowledge gap, we built and fitted a Bayesian network (BN), informed by a review of past studies, which integrates the links and direction of effects between socio-ecosystem components. These effects are represented as conditional probabilities, so that missing magnitudes of some ecosystem effects emerge from the numerous past cases that were reviewed. The Bayesian network is informed by a collection of cases extracted from 246 published scientific studies investigating relationships in marine ecosystems. We find that marine ecosystems are likely to be on a declining course under conjugated pressures of both fishing and changes to environmental conditions, e.g. due to ongoing climate change. By querying the fitted BN to obtain posterior probabilities under different scenarios, we showed that increasing fisheries regulation and environmental governance could partly mitigate these effects and decrease the risk of biodiversity loss, decreased profit and social inequity; the three pillars of the EU Common Fishery Policy (CFP). We discuss these findings with regard to particular fisheries across EU Waters, specifically: the North Sea, the Baltic Sea, the North Western and the South Western Waters. Furthermore, we discuss how fishing impacts interact with other ecosystem effects and pressures, caused by, or causing possible far-reaching consequences in marine ecosystem dynamics. The Bayesian network has some limitations regarding the ability to handle feedback loops that can occur in natural marine ecosystems. Nevertheless, such an approach helps to take a holistic view and integrate existing knowledge and new findings from future work, in a coherent, probabilistic risk assessment framework, while identifying what leverage and management actions may help nudge the system toward desired states.

Aggregates in aquatic ecosystems and implications for aquacultures

Agglomerations of suspended particulate matter serve various roles in aquatic ecosystems. They participate in nutrient and energy fluxes and are involved in important food web processes. While comprehensive studies on aggregates are available from natural freshwater and marine ecosystems, little is known about the roles of aggregates in aquacultures, particularly in shrimp pond farming. As particle-rich systems, shrimp ponds and marine aquaculture (mariculture) areas constitute interesting objects for aggregate studies, particularly as a source of natural feed, particle fluxes, microbial communities, including pathogenic bacteria, and possible vector of disease widespread. The aims of this review are i) to compile the current knowledge on the role of aggregates in aquatic ecosystems, particularly in aquaculture areas covering advantages and negative side effects of aggregates in aquacultures, ii) to explore the role of aggregates in disease ecology, and iii) perspective of aquaculture management in the context of aggregate utilization and management. Since Southeast Asia, especially Indonesia, is among the most important regions for aquaculture activities, this review focuses on Indonesian aquacultures. Although aquacultures produce important amounts of aggregates, including its associated microbial communities, they are rarely investigated in Indonesian aquacultures, particularly in shrimp pond farming. In contrast, most of the studies focused on bacterial cultivation and utilization of isolates for aquacultures. Thus, understanding the ecological roles of aggregates in aquacultures may support the improvement of aquaculture management and yields.

Research on Three-Dimensional Ocean Temperature Field Variation Model Based on Assimilation and Reconstruction of Regression Equation

Qin, F.; Zeng, W.; Zou, C., and Yang, J., 2020. Research on three-dimensional ocean temperature field variation model based on assimilation and reconstruction of regression equation. In: Yang, D.F. and Wang, H. (eds.), Recent Advances in Marine Geology and Environmental Oceanography. Journal of Coastal Research, Special Issue No. 108, pp. 37–41. Coconut Creek (Florida), ISSN 0749-0208.For a long time, natural marine ecosystems have been subject to strong human intervention and global environmental changes. Therefore, it is a meaningful challenge to objectively evaluate the constituent elements of marine material transport, energy flow, and system functions. Besides, the calculation method of three-dimensional (3D) ocean temperature fields is improved in the paper by establishing regression model assimilation and reconstruction of 3D ocean temperature fields. Moreover, according to Guinethut's method, the model is reconstructed with the help of 3D monthly average temperatures and the salinity field of the Copernicus Marine Environment Monitoring Service. Then, monthly average sea surface data sea level anomaly and sea surface temperature from the satellite observations of the next year are used to derive 3D monthly average temperatures of the next year field. Additionally, the data sets of adjacent or similar years are applied to obtain linear regression relationships between sea surface and underwater features, which can improve the accuracy of reconstruction. The most optimal interpolation method is used to assimilate the measured data of Argo to increase accuracy. Finally, after data analysis and comparison, it is proved that compared with other methods, the observation value of the data model established in research content of the paper is further improved, which provides important reference for marine ecological protection work.

Structure and Dynamics of Waters in the Region of the Shantar Islands National Park (Sea of Okhotsk) Based on the Data of Satellite Observations

The Shantar Islands National Park (northwestern shelf of the Sea of Okhotsk) was established to preserve the biological diversity of unique natural marine and terrestrial ecosystems. The water structure and dynamics in the basin of the Shantar Islands has been studied based on the analysis of multisensor satellite images (Terra/Aqua MODIS, Landsat-7 ETM+, Landsat-8 OLI/TIRS, Sentinel-2A MSI) and field oceanographic observations. The circulation over the shelf in the Shantar Islands region is strongly determined by strong tidal currents and freshwater discharge. The water structure is formed under the influence of intense local tidal mixing and the propagation of low-saline river plumes in the shallow parts of the main bays of the Shantar archipelago. The interaction of tidal currents with the complex topography and bathymetry (peninsulas, capes, islands, straits, and shallow-water regions of the shelf) leads to a high level of submesoscale activity and the generation of various types of submesoscale structures, including jet currents and eddies.

Predators Shape Sedimentary Organic Carbon Storage in a Coral Reef Ecosystem

Trophic cascade theory predicts that predator effects should extend to influence carbon cycling in ecosystems. Yet, there has been little empirical evidence in natural ecosystems to support this hypothesis. Here, we use a naturally-occurring trophic cascade to provide evidence that predators help protect sedimentary organic carbon stocks in coral reef ecosystems. Our results show that predation risk altered the behavior of herbivorous fish, whereby it constrained grazing to areas close to the refuge of the patch reefs. Macroalgae growing in riskier areas further away from the reef were released from grazing pressure, which subsequently promoted carbon accumulation in the sediments underlying the macroalgal beds. Here we found that carbon stocks furthest away from the reef edge were similar to 24% higher than stocks closest to the reef. Our results indicate that predators and herbivores play an important role in structuring carbon dynamics in a natural marine ecosystem, highlighting the need to conserve natural predator-prey dynamics to help maintain the crucial role of marine sediments in sequestering carbon.

Predictive functional profiles using metagenomic 16S rRNA data: a novel approach to understanding the microbial ecology of aquaculture systems

AbstractMicro‐organisms are an essential component of natural marine ecosystems, but also play important roles in anthropogenically modified ecosystems, including aquaculture. Although metagenomics is currently used to explore microbial communities, its application has not been as extensive in aquaculture. Although some taxonomic profiles and phylogenetic studies have been deciphered using biomarker genes, the functional potential of microbial communities associated with aquaculture systems is still unknown in most cases. Predicting functional profiles through 16S rRNA gene‐based metagenomics analysis is perhaps the most promising tool to elucidate the metabolic capabilities of microbial communities because there is no need to perform shotgun sequencing to have an idea of these capabilities. Moreover, robust bioinformatics background is not required to assess this information, and so the same data (16S rRNA sequences) are used to estimate both taxonomic and functional profiles, therefore providing deeper insights into these kinds of communities. In this review, we suggest the need to major use of novel bioinformatics tools that construct functional profiles from metagenomic 16S rRNA data, as strategy to obtain a preliminary approach about metabolic capacities of microbes that coexist in aquaculture systems.

Parasite infection and immune and health-state in wild fish exposed to marine pollution

Association between parasitism and immunity and health-state was investigated in wild Sebastes oculatus after having determined that pollution exposure is associated with altered immune and health-state parameters. Given the importance of the immune system in antiparasite defense we predicted: (i) parasite infection would be higher in pollution-exposed than in control fish and (ii) fish with lower immune and health-state parameters would show higher parasitism than fish in better condition. Metazoan parasite fauna was compared between pollution-exposed and non-exposed fish and parasitic indices were correlated with integrated measures of immunity and health-state. Results provided little support for the predictions; some parasite taxa increased, some decreased, and some were not affected in pollution-exposed fish despite their altered health and immunity. Furthermore, there was no link between individual immune and health-state parameters and parasitism. These findings highlight the complexity of host-parasite-environment interactions in relation to pollution in natural marine ecosystems.

Prey size diversity hinders biomass trophic transfer and predator size diversity promotes it in planktonic communities

Body size exerts multiple effects on plankton food-web interactions. However, the influence of size structure on trophic transfer remains poorly quantified in the field. Here, we examine how the size diversity of prey (nano-microplankton) and predators (mesozooplankton) influence trophic transfer efficiency (using biomass ratio as a proxy) in natural marine ecosystems. Our results support previous studies on single trophic levels: transfer efficiency decreases with increasing prey size diversity and is enhanced with greater predator size diversity. We further show that communities with low nano-microplankton size diversity and high mesozooplankton size diversity tend to occur in warmer environments with low nutrient concentrations, thus promoting trophic transfer to higher trophic levels in those conditions. Moreover, we reveal an interactive effect of predator and prey size diversities: the positive effect of predator size diversity becomes influential when prey size diversity is high. Mechanistically, the negative effect of prey size diversity on trophic transfer may be explained by unicellular size-based metabolic constraints as well as trade-offs between growth and predation avoidance with size, whereas increasing predator size diversity may enhance diet niche partitioning and thus promote trophic transfer. These findings provide insights into size-based theories of ecosystem functioning, with implications for ecosystem predictive models.

Temporal stability of parasite distribution and genetic variability values of Contracaecum osculatum sp. D and C.osculatum sp. E (Nematoda: Anisakidae) from fish of the Ross Sea (Antarctica).

The Ross Sea, Eastern Antarctica, is considered a “pristine ecosystem” and a biodiversity “hotspot” scarcely impacted by humans. The sibling species Contracaecum osculatum sp. D and C. osculatum sp. E are anisakid parasites embedded in the natural Antarctic marine ecosystem. Aims of this study were to: identify the larvae of C. osculatum (s.l.) recovered in fish hosts during the XXVII Italian Expedition to Antarctica (2011–2012); perform a comparative analysis of the contemporary parasitic load and genetic variability estimates of C. osculatum sp. D and C. osculatum sp. E with respect to samples collected during the expedition of 1993–1994; to provide ecological data on these parasites. 200 fish specimens (Chionodraco hamatus, Trematomus bernacchii, Trematomus hansoni, Trematomus newnesi) were analysed for Contracaecum sp. larvae, identified at species level by allozyme diagnostic markers and sequences analysis of the mtDNA cox2 gene.Statistically significant differences were found between the occurrence of C. osculatum sp. D and C. osculatum sp. E in different fish species. C. osculatum sp. E was more prevalent in T. bernacchii; while, a higher percentage of C. osculatum sp. D occurred in Ch. hamatus and T. hansoni. The two species also showed differences in the host infection site: C. osculatum sp. D showed higher percentage of infection in the fish liver. High genetic variability values at both nuclear and mitochondrial level were found in the two species in both sampling periods. The parasitic infection levels by C. osculatum sp. D and sp. E and their estimates of genetic variability showed no statistically significant variation over a temporal scale (2012 versus 1994). This suggests that the low habitat disturbance of the Antarctic region permits the maintenance of stable ecosystem trophic webs, which contributes to the maintenance of a large populations of anisakid nematodes with high genetic variability.