Structure Of Marine Ecosystems Research Articles

Generating open-source 3D phytoplankton models by integrating photogrammetry with scanning electron microscopy.

The community structure and ecological function of marine ecosystems are critically dependent on phytoplankton. However, our understanding of phytoplankton is limited due to the lack of detailed information on their morphology. To address this gap, we developed a framework that combines scanning electron microscopy (SEM) with photogrammetry to create realistic 3D (three-dimensional) models of phytoplankton. The workflow of this framework is demonstrated using two marine algal species, one dinoflagellate Prorocentrum micans and one diatom Halamphora sp. The resulting 3D models are made openly available and allow users to interact with phytoplankton and their complex structures virtually (digitally) and tangibly (3D printing). They also allow for surface area and biovolume calculations of phytoplankton, as well as the exploration of their light scattering properties, which are both important for ecosystem modeling. Additionally, by presenting these models to the public, it bridges the gap between scientific inquiry and education, promoting broader awareness on the importance of phytoplankton.

Insights on long-term ecosystem changes from stable isotopes in historical squid beaks

BackgroundAssessing the historical dynamics of key food web components is crucial to understand how climate change impacts the structure of Arctic marine ecosystems. Most retrospective stable isotopic studies to date assessed potential ecosystem shifts in the Arctic using vertebrate top predators and filter-feeding invertebrates as proxies. However, due to long life histories and specific ecologies, ecosystem shifts are not always detectable when using these taxa. Moreover, there are currently no retrospective stable isotopic studies on various other ecological and taxonomic groups of Arctic biota. To test whether climate-driven shifts in marine ecosystems are reflected in the ecology of short-living mesopredators, ontogenetic changes in stable isotope signatures in chitinous hard body structures were analysed in two abundant squids (Gonatus fabricii and Todarodes sagittatus) from the low latitude Arctic and adjacent waters, collected between 1844 and 2023.ResultsWe detected a temporal increase in diet and habitat-use generalism (= opportunistic choice rather than specialization), trophic position and niche width in G. fabricii from the low latitude Arctic waters. These shifts in trophic ecology matched with the Atlantification of the Arctic ecosystems, which includes increased generalization of food webs and higher primary production, and the influx of boreal species from the North Atlantic as a result of climate change. The Atlantification is especially marked since the late 1990s/early 2000s. The temporal patterns we found in G. fabricii’s trophic ecology were largely unreported in previous Arctic retrospective isotopic ecology studies. Accordingly, T. sagittatus that occur nowadays in the high latitude North Atlantic have a more generalist diet than in the XIXth century.ConclusionsOur results suggest that abundant opportunistic mesopredators with short life cycles (such as squids) are good candidates for retrospective ecology studies in the marine ecosystems, and to identify ecosystem shifts driven by climate change. Enhanced generalization of Arctic food webs is reflected in increased diet generalism and niche width in squids, while increased abundance of boreal piscivorous fishes is reflected in squids’ increased trophic position. These findings support opportunism and adaptability in squids, which renders them as potential winners of short-term shifts in Arctic ecosystems.

Geobiology: Machine learning puts bioturbation on the map

Bioturbation, the mixing of sediment through the actions of organisms, is a crucial ecosystem engineering process that controls biogeochemical cycles and helps structure marine ecosystems. Machine learning is helping to develop global maps of the intensity and depth of bioturbation.

Large potential impacts of marine heatwaves on ecosystem functioning.

Ocean warming is driving significant changes in the structure and functioning of marine ecosystems, shifting species' biogeography and phenology, changing body size and biomass and altering the trophodynamics of the system. Particularly, extreme temperature events such as marine heatwaves (MHWs) have been increasing in intensity, duration and frequency. MHWs are causing large-scale impacts on marine ecosystems, such as coral bleaching, mass mortality of seagrass meadows and declines in fish stocks and other marine organisms in recent decades. In this study, we developed and applied a dynamic version of the EcoTroph trophodynamic modelling approach to study the cascading effects of individual MHW on marine ecosystem functioning. We simulated theoretical user-controlled ecosystems and explored the consequences of various assumptions of marine species mortality along the food web, associated with different MHW intensities. We show that an MHW can lead to a significant biomass reduction of all consumers, with the severity of the declines being dependent on species trophic levels (TLs) and biomes, in addition to the characteristics of MHWs. Biomass of higher TLs declines more than lower TLs under an MHW, leading to changes in ecosystem structure. While tropical ecosystems are projected to be sensitive to low-intensity MHWs, polar and temperate ecosystems are expected to be impacted by more intense MHWs. The estimated time to recover from MHW impacts is twice as long for polar ecosystems and one-third longer for temperate biomes compared with tropical biomes. This study highlights the importance of considering extreme weather events in assessing the effects of climate change on the structures and functions of marine ecosystems.

What has Changed in 20 Years? Structure and Function of Soft-sediment Macrofauna in a Subarctic Embayment, Newfoundland (Canada)

Understanding how natural and anthropogenic disturbances affect the structure and functioning of marine ecosystems is central to predicting future dynamics. Placentia Bay is an Ecologically and Biologically Significant Area (EBSA) in the North Atlantic exposed to multiple stressors (e.g., rising sea surface temperatures, tanker traffic, and aquaculture). To investigate changes in the community and functional structure of soft-sediment macrofauna as well as environmental drivers of observed variation, we compared contemporary (2019–2020) and historical (1998) samples at eight stations (n = 77) collected 21 years apart. Although community and functional structure differed between these time points, functional traits were maintained (i.e., no loss of 36 trait modalities). Overall, 37% of species/taxa were only observed in either the historical or contemporary community, and the contemporary community exhibited lower macrofaunal density but had similar richness, resulting in higher evenness and diversity. Highly tolerant subsurface deposit feeders having small body sizes (< 10 mm) and direct development dominated the historical community. The contemporary community had nearly equal proportions of surface and subsurface deposit feeders with small to medium body sizes (< 10–50 mm) with pelagic larvae, and the proportion of highly tolerant species/taxa was reduced. These changes likely reflect the reduction in polychaetes (91 vs. 58%) and increased bivalves (4 vs. 25%) relative to the historical time point. Community variation was driven by changes in the sedimentary habitat. Contemporary versus historical sediments were ~ 4.5x coarser (possibly due to storms) with higher levels of sedimentary organic matter. This work contributes to advancing the understanding of relationships between benthic macrofauna, functional traits, and the sedimentary habitat in coastal environments.

Top predator status and trends: ecological implications, monitoring and mitigation strategies to promote ecosystem-based management

The conservation and management of marine ecosystems hinge on a comprehensive understanding of the status and trends of top predators. This review delves into the ecological significance of marine top predators, examining their roles in maintaining ecosystem stability and functioning through an integrated analysis of current scientific literature. We first assess the efficacy of various monitoring methods, ranging from traditional field observations to cutting-edge technologies like satellite tracking and environmental DNA (eDNA) analysis and evaluating their strengths and limitations in terms of accuracy, spatial coverage, and cost-effectiveness, providing resource managers with essential insights for informed decision-making. Then, by synthesizing data from diverse marine ecosystems, this study offers a comprehensive overview of the trends affecting top predator populations worldwide. We explore the multifaceted impacts of human activities, climate change, and habitat degradation on the abundance and distribution of these key species. In doing so, we shed light on the broader implications of declining top predator populations, such as trophic cascades and altered community structures. Following a thorough assessment of successful strategies for reversing the decline of top predators, a compilation of recommendations is presented, encompassing effective governance interventions. A crucial aspect of effective ecosystem-based management is the implementation of robust monitoring strategies. Mitigation measures are imperative to reverse the adverse impacts on marine top predators. We present a comprehensive array of mitigation options based on successful case studies. These include the establishment of marine protected areas, the enforcement of fisheries regulations, and the promotion of sustainable fishing practices. We deepen the synergies between these strategies and their potential to mitigate human-induced stressors on top predator populations to safeguard their pivotal role in maintaining marine ecosystem structure and function. By examining marine top predators’ ecological significance, analyzing population trends, discussing monitoring techniques, and outlining effective mitigation strategies, we provide a comprehensive resource for researchers, policymakers, and stakeholders engaged in fostering ecosystem-based management approaches. We conclude that integrating these insights into current management frameworks will be essential to safeguard both top predators and the broader marine environment for future generations.

Relative prevalence of top-down versus bottom-up control in planktonic ecosystem under eutrophication and climate change: A comparative study of typical bay and estuary

Eutrophication and climate change may affect the top-down versus bottom-up controls in aquatic ecosystems. However, the relative prevalence of the two controls in planktonic ecosystems along the eutrophication and climate gradients has rarely been addressed. Here, using the field surveys of 17 years in a typical bay and estuary, we test two opposite patterns of trophic control dominance and their response to regional temporal eutrophication and climate fluctuations. It was found that trophic control of planktonic ecosystems fluctuated between the dominance of top-down and bottom-up controls on time scales in both the bay and estuary studied. The relative prevalence of these two controls in both ecosystems was significantly driven directly by regional dissolved inorganic nitrogen but, for the estuary, also by the nonlinear effects of regional sea surface temperature. In terms of indirect pathways, community relationships (synchrony and grazing pressure) in the bay are driven by both regional dissolved inorganic nitrogen - soluble reactive phosphorus ratio and sea surface temperature, but this drive did not continue to be transmitted to the trophic control. Conversely, trophic control in estuary was directly related to grazing pressure and indirectly related to synchrony. These findings support the view that eutrophication and climate drive the relative prevalence of top-down versus bottom-up controls at ecosystem and temporal scales in planktonic ecosystems, which has important implications for predicting the potential impacts of anthropogenic and environmental perturbations on the structure and function of marine ecosystems.

Isopycnal Submesoscale Stirring Crucially Sustaining Subsurface Chlorophyll Maximum in Ocean Cyclonic Eddies

AbstractMesoscale and submesoscale processes have crucial impacts on ocean biogeochemistry, importantly enhancing the primary production in nutrient‐deficient ocean regions. Yet, the intricate biophysical interplay still holds mysteries. Using targeted high‐resolution in situ observations in the South China Sea, we reveal that isopycnal submesoscale stirring serves as the primary driver of vertical nutrient transport to sustain the dome‐shaped subsurface chlorophyll maximum (SCM) within a long‐lived cyclonic mesoscale eddy. Density surface doming at the eddy core increased light exposure for phytoplankton production, while along‐isopycnal submesoscale stirring disrupted the mesoscale coherence and drove significant vertical exchange of tracers. These physical processes play a crucial role in maintaining the elevated phytoplankton biomass in the eddy core. Our findings shed light on the universal mechanism of how mesoscale and submesoscale coupling enhances primary production in ocean cyclonic eddies, highlighting the pivotal role of submesoscale stirring in structuring marine ecosystems.

Unravelling the trophic ecology of poorly studied and threatened elasmobranchs inhabiting the Persian Gulf and Gulf of Oman

Elasmobranch population declines due to human impacts have been documented at a global scale, having impacts on the functioning and structure of marine ecosystems. This situation leads to an international focus on the conservation of their populations and a key step in the management and conservation of elasmobranch populations is to understand their trophic ecology. Here, by using stable isotopes analysis, we investigated the trophic relationships, trophic niche breadth, and trophic redundancy among 21 batoids and 12 sharks inhabiting the Persian Gulf and Gulf of Oman, two productive areas of the Arabian Sea considered global elasmobranch hotspots. Isotopic results revealed differences in the trophic niche and trophic position among the elasmobranch sampled at species and at family level. For example, the batoids of the family Torpedinidae and the sharks of the family Triakidae occupied higher trophic positions and the family Glaucostegidae showed a lower trophic niche width, whereas the batoids of the family Myliobatidae or Gymnuridae, in overall, showed lower higher trophic niche width, reflecting the trophic habits described for most of the sampled species. We also provided some insights into the ecology of poorly known species, especially relevant for those that are endangered at a global or regional scale. In conclusion, we provide new information about the trophic ecology among batoids and sharks inhabiting the Persian Gulf and Gulf of Oman. This information is highly useful to study the consequences of future changes on their feeding preferences due to natural or human-related factors.

The rise of macropredatory pliosaurids near the Early-Middle Jurassic transition

The emergence of gigantic pliosaurid plesiosaurs reshaped the trophic structure of Mesozoic marine ecosystems, and established an ~ 80 million-year (Ma) dynasty of macropredatory marine reptiles. However, the timescale of their ‘defining’ trait evolution is incompletely understood because the fossil record of gigantic pliosaurids is scarce prior to the late-Middle Jurassic (Callovian), ~ 165.3 Ma. Here, we pinpoint the appearance of large body size and robust dentitions to early-Middle Jurassic (Bajocian) pliosaurids from northeastern France and Switzerland. These specimens include a new genus that sheds light on the nascent diversification of macropredatory pliosaurids occurring shortly after the Early-Middle Jurassic transition, around ~ 171 Ma. Furthermore, our multivariate assessment of dental character states shows that the first gigantic pliosaurids occupied different morphospace from coeval large-bodied rhomaleosaurid plesiosaurs, which were dominant in the Early Jurassic but declined during the mid-Jurassic, possibly facilitating the radiation and subsequent ecomorph acme of pliosaurids. Finally, we posit that while the emergence of macropredatory pliosaurids was apparently coordinated with regional faunal turnover in the epeiric basins of Europe, it paralleled a globally protracted extinction of other higher trophic-level marine reptiles that was not completed until after the earliest-Late Jurassic, ~ 161.5 Ma.

Proportion of dead cells in phytoplankton modulates community structure

The growth and death of phytoplankton are two key processes that affect structure and function of marine ecosystem. However, current understanding is elaborated from the perspective of growth, and relatively little is known about the environment-driven death of phytoplankton. Our study is aimed to elucidate the differences in group-specific proportion of dead cells and their effects on community structure. Based on flow cytometry analysis, the proportion of dead cells among eukaryotic phytoplankton groups was analyzed in the oligotrophic South China Sea. The eukaryotic phytoplankton were divided into five groups (eukaryotic group 1, eukaryotic group 2, eukaryotic group 3, cryptophytes, and eukaryotic group 4) with successively larger cell size from pico to micro. The larger cells (from nano to micro size) had a higher proportion of dead cells and a lower relative abundance. Only the group of large cells showed a complete correspondence between the proportion of dead cells and abundance in the vertical profile. Above the deep chlorophyll maximum layer, death induced by nutrient limitation was apparent in most groups, and the larger the cell size, the greater the limitation. Below the deep chlorophyll maximum layer, all groups were light-limited, but differences in the degree of light limitation among groups were not significant. These results suggested that differences in cell size contribute to some extent to differences in the proportion of dead cells among groups, making the proportion of dead cells important in regulating community structure and thus further influencing the structure and function of pelagic marine ecosystems.

Toward efficient deep learning system for in-situ plankton image recognition

Plankton is critical for the structure and function of marine ecosystems. In the past three decades, various underwater imaging systems have been developed to collect in-situ plankton images and image processing has been a major bottleneck that hinders the deployment of plankton imaging systems. In recent years, deep learning methods have greatly enhanced our ability of processing in-situ plankton images, but high-computational demands and longtime consumption still remain problematic. In this study, we used knowledge distillation as a framework for model compression and improved computing efficiency while maintaining original high accuracy. A novel inter-class similarity distillation algorithm based on feature prototypes was proposed and enabled the student network (small scale) to acquire excellent ability for plankton recognition after being guided by the teacher network (large scale). To identify the suitable teacher network, we compared emerging Transformer neural networks and convolution neural networks (CNNs), and the best performing deep learning model, Swin-B, was selected. Utilizing the proposed knowledge distillation algorithm, the feature extraction ability of Swin-B was transferred to five more lightweight networks, and the results had been evaluated in taxonomic dataset of in-situ plankton images. Subsequently, the chosen lightweight model and the Bilateral–Sobel edge enhancement were tested to process in-situ images with high level of noises captured from coastal waters of Guangdong, China and achieved an overall recall rate of 91.73%. Our work contributes to effective deep learning models and facilitates the deployment of underwater plankton imaging systems by promoting both accuracy and speed in recognition of plankton targets.

Identifying suitable indicators to measure ecological condition of rocky reef ecosystems in South Africa

Baseline data for reference conditions are needed to determine the impacts of human pressures on the structure and functioning of marine ecosystems. However, baseline data are seldom available, and a comprehensive understanding of what good ecological condition is or how to measure it is often lacking. In the absence of true baselines, well established and effective marine protected areas (MPAs) can be used to approximate reference conditions. Thus, the aim of this study was to use effective no-take MPAs to identify suitable indicators that can be used for condition assessments of rocky reefs in South Africa. To achieve this, we tested the response of two types of metrics (compositional and size-based), using in situ fish and benthic community data, to three levels of human pressures in two ecoregions in South Africa. Results showed that traditionally-used structural metrics, such as total abundance or species richness, were less responsive than size-based metrics, including total biomass, average length and proportion of mature fish. Rocky reef ecosystems exposed to low anthropogenic pressure were characterised by a higher biomass, average length and proportion of mature and large (>30 cm) fish than reefs with moderate and high pressures. Benthic communities appeared more resilient than fish communities to the typical human pressures in the study region. Overall, the greatest effect of pressure was observed in the heavily impacted sub-tropical Natal Shelf Ecoregion, while rocky reefs in the warm-temperate Agulhas Shelf Ecoregion appeared to be in better condition than expected. This study identified assemblage patterns and indicators that appeared responsive and sensitive to different levels of human pressure, which can be used to infer good and poor ecological condition of rocky reef ecosystems. These results indicate which species (e.g., target species) and traits (e.g., size) are most vulnerable to local human pressures and will be suitable for condition assessments.

Existing evidence on the impact of changes in marine ecosystem structure and functioning on ecosystem service delivery: a systematic map

BackgroundThe current biodiversity crisis underscores the urgent need for sustainable management of the human uses of nature. In the context of sustainability management, adopting the ecosystem service (ES) concept, i.e., the benefits humans obtain from nature, can support decisions aimed at benefiting both nature and people. However, marine ecosystems in particular endure numerous direct drivers of change (i.e., habitat loss and degradation, overexploitation, pollution, climate change, and introduction of non-indigenous species) all of which threaten ecosystem structure, functioning, and the provision of ES. Marine ecosystems have received less attention than terrestrial ecosystems in ES literature, and knowledge on marine ES is hindered by the highly heterogeneous scientific literature with regard to the different types of marine ecosystem, ES, and their correlates. Here, we constructed a systematic map of the existing literature to highlight knowledge clusters and knowledge gaps on how changes in marine ecosystems influence the provision of marine ES.MethodWe searched for all evidence documenting how changes in structure and functioning of marine ecosystems affect the delivery of ES in academic and grey literature sources. In addition to Scopus, Web of Science, and Google Scholar, we searched 6 online databases from intergovernmental agencies, supranational or national organizations, and NGOs. We screened English-language documents using predefined inclusion criteria on titles, abstracts, and then full texts, without any geographic or temporal limitations. All qualifying literature was coded and metadata were extracted. No formal validity appraisal was undertaken. We identified knowledge clusters and gaps in terms of which ecosystem types, biodiversity components, or ES types have been studied and how these categories are linked.Review findingsOur searches identified 41 884 articles published since 1968 of which 12 140 were duplicates; 25 747 articles were excluded at the title-screening stage, then 2774 at the abstract stage. After full-text screening, a total of 653 articles—having met the eligibility criteria—were included in the final database, spanning from 1977 to July 2021. The number of studies was unevenly distributed across geographic boundaries, ecosystem types, ES, and types of pressure.The most studied ecosystems were pelagic ecosystems on continental shelves and intertidal ecosystems, and deep-sea habitats and ice-associated ecosystems were the least studied. Food provision was the major focus of ES articles across all types of marine ecosystem (67%), followed by climate regulation (28%), and recreation (14%). Biophysical values were assessed in 91% of the analysed articles, 30% assessed economic values, but only 3% assessed socio-cultural values. Regarding the type of impact on ecosystems, management effects were the most studied, followed by overexploitation and climate change (with increase in seawater temperature being the most commonly assessed climate change pressure). Lastly, the introduction of non-indigenous species and deoxygenation were the least studied.ConclusionsThis systematic map provides, in addition to a database, knowledge gaps and clusters on how marine ecosystem changes impact ES provision. The current lack of knowledge is a threat to the sustainability of human actions and knowledge-based nature conservation. The knowledge gaps and clusters highlighted here could guide future research and impact the beneficial development of policy and management practices.

Warming and parasitism impair the performance of Baltic native and invasive macroalgae and their associated fauna

AbstractGlobal warming, bioinvasions, and parasitism affect single‐species performances and species interactions, substantially impacting the structure and stability of marine ecosystems. In light of accelerated global change, the information derived from studies focusing on single species and single drivers is insufficient, calling for a multi‐stressor approach under near‐natural conditions. We investigated the effects of warming (+3°C) on the performance of a benthic community composed of native and invasive macroalgae, consumers and a trematode parasite in a mesocosm setting. We also assessed the effects of warming and parasitism on the survival and growth of gastropods and mussels and the thermal dependency of trematode performance. Our findings show that warming and grazing by infected gastropods had a large detrimental effect on the invasive macroalga growth. Furthermore, the single and interactive effects of parasitism and warming were detrimental to intermediate host survival and growth, especially to large mussels. Finally, cercarial emergence positively correlated to the natural peaks of summer temperatures, while infection intensity in mussels was higher in larger individuals. Our findings suggest that grazing and warming will be detrimental to the invasive macroalga, favoring the native alga. Moreover, parasitism will enhance grazing, especially in summer, when higher temperatures trigger parasite development. However, parasite‐enhanced grazing may be buffered by higher mortality or a shift in the size of infected intermediate hosts under warming. Our findings demonstrate how complex effects of ocean warming can be on food webs and how they can be mediated by parasitism and, as a result, influence native and invasive macroalgae differently.

Drivers of Physical and Biological Frontal Variability in the Northern California Current System

AbstractOceanic fronts mark the boundary between two water masses and are often sites of complex bio‐physical processes and multi‐trophic level interactions, making them particularly important features in marine ecosystems. As global climate change induces multi‐scale shifts in the driving physical mechanisms of fronts, spatiotemporal tracking of frontal variability can aid in efforts to understand the downstream effects on marine biodiversity and ecosystem structure. Here we focus on fronts within the dynamic northern extent of the California Current System (NCC). We derived mesoscale sea surface temperature (SST) and chlorophyll‐a (chl‐a) fronts across the NCC region from 4‐km MODIS‐Aqua L3 daily fields over 2003–2019. Mesoscale physical (SST) and biological (chl‐a) fronts were often adjacent and coherent in their seasonal and interannual occurrence frequencies, but were spatially decoupled. SST fronts were most frequent and broadly distributed offshore while chl‐a fronts mostly occurred along the continental shelf break, particularly from Vancouver Island to central Oregon. Additionally, we employed a standardized multiple linear regression analysis to quantify the relative influence of local‐ and basin‐scale processes on frontal variability in the NCC. Local wind stress and wind stress curl variability were the most influential drivers of fronts over the shelf, while basin‐scale climate variability (i.e., climate oscillations) significantly drove frontal occurrences along the shelf break and offshore. Given predictions in the intensification of coastal upwelling in systems such as the NCC, our results indicate that oceanic response to climate change driven atmospheric variability will significantly impact the NCC marine ecosystem on the mesoscale.

Ecotrophic perspective in fisheries management: a review of Ecopath with Ecosim models in European marine ecosystems

The aim of this work is to present the food web models developed using the Ecopath with Ecosim (EwE) software tool to describe structure and functioning of various European marine ecosystems (eastern, central and western Mediterranean Sea; Black Sea; Bay of Biscay, Celtic Sea and Iberian coast; Baltic Sea; North Sea; English Channel, Irish Sea and west Scottish Sea; and Norwegian and Barents Seas). A total of 195 Ecopath models based on 168 scientific publications, which report original, updated and modified versions, were reviewed. Seventy models included Ecosim temporal simulations while 28 implemented Ecospace spatiotemporal dynamics. Most of the models and publications referred to the western Mediterranean Sea followed by the English Channel, Irish Sea and west Scottish Sea sub-regions. In the Mediterranean Sea, the western region had the largest number of models and publications, followed by the central and eastern regions; similar trends were observed in previous literature reviews. Most models addressed ecosystem functioning and fisheries-related hypotheses while several investigated the impact of climate change, the presence of alien species, aquaculture, chemical pollution, infrastructure, and energy production. Model complexity (i.e., number of functional groups) increased over time. Main forcing factors considered to run spatial and temporal simulations were trophic interactions, fishery, and primary production. Average scores of ecosystem indicators derived from the Ecopath summary statistics were compared. Uncertainty was also investigated based on the use of the Ecosampler plug-in and the Monte Carlo routine; only one third of the reviewed publications incorporated uncertainty analysis. Only a limited number of the models included the use of the ECOIND plug-in which provides the user with quantitative output of ecological indicators. We assert that the EwE modelling approach is a successful tool which provides a quantitative framework to analyse the structure and dynamics of ecosystems, and to evaluate the potential impacts of different management scenarios.

Vertical, spatial, size, and taxonomic variations in stable isotopes (δ13C and δ15N) of zooplankton and other pelagic organisms in the western North Pacific

Stable isotopes (δ13C and δ15N) of zooplankton and other marine organisms are useful for evaluating trophic levels and the food web structure of marine ecosystems. Further, taxonomic variations and regressions between δ15N and δ13C can provide details of regional differences in the food web structure. Despite their ecological importance, information on the taxonomic differences in the stable isotopes of various pelagic biota and vertical, latitudinal, and size variations in the stable isotopes of the mesozooplankton are scarce in the western North Pacific. In this study, we compared regional differences in the taxonomic variations of the stable isotopes of the all pelagic organisms collected by gillnets and various plankton nets in the subarctic and transitional domains (37–44°N) of the western North Pacific during spring. Additionally, we evaluated the vertical, size, and latitudinal variations in the stable isotopes of mesozooplankton in the western North Pacific. Regressions between δ15N and δ13C were highly significant for the subarctic and transitional domains, while they varied significantly between the two regions (P < 0.0001, ANCOVA). These regional differences in the stable isotopes were characterised by the high δ15N and low δ13C values in the subarctic region, whereas the opposites trend was observed in the transitional domains. Vertical observations from the sea surface to a depth of 3000 m at five stations (29°, 31°, 33°, 37°, and 41°N) showed that there were no significant changes in the δ13C stable isotope of mesozooplankton with depth across the stations. However, for δ15N, the significance of regressions increased with increasing depths at the subtropical stations (29°, 31°, and 33°N), while no significant trends with depth were observed for the subarctic and transitional domain stations (37°, 41°N). The dominance of interzonal copepods (e.g., Neocalanus spp.) in the mesozooplankton biomass in the subarctic and transitional region may mask the vertical changes in δ15N values in that region. Further, δ13C varied neither with size nor latitude. In contrast, δ15N showed clear size and latitudinal patterns. Thus, δ15N values increased with increasing zooplankton size (112 μm < 407 μm < 925 μm), and significant regressions increased with increasing latitude for all three size classes (P < 0.001). Subsequent ANCOVA revealed that the regression did not vary with organism size. Thus, the changing latitudinal patterns in δ15N values (higher for high latitude) had much greater effects than the size differences for mesozooplankton.

Structural control of Cambrian paleotopography and patterns of transgression in western Laurentia

Abstract The Cambrian transgression across the Great Unconformity produced one of the largest expansions of shallow marine habitats and associated diversification of marine invertebrate faunas in Earth history. However, identification of the underlying controls on the pattern of transgression of Cambrian seas has been hampered by imprecise or inaccurate age assignments for many formations. Recovery of an Ehmaniella Zone trilobite fauna from the Lodore Formation in northwestern Colorado (United States) revises the age of this unit to be significantly older, specifically middle Miaolingian (upper Wuliuan). This expands the established distribution of thick Miaolingian deposits of the northern Rocky Mountains to within 90 km of a broad region of central Colorado where Miaolingian strata are missing and Furongian successions rest directly on basement. The boundary between these two regions marks the position of an ~200 km east-west offset within the generally north-south–trending Cambrian paleoshoreline of western North America. The offset is co-located with a Precambrian continental suture zone (Cheyenne belt) at the northern Yavapai terrane margin and is directly east of an offset of similar magnitude and latitude in the early to middle Paleozoic shelf edge in Nevada. We thus posit that Precambrian deep-seated crustal-scale features controlled the Cambrian paleotopography of western Laurentia, strongly influencing the patterns of Cambrian transgression and structure of the shallow marine ecosystem established during continental submergence. These continental-scale structural elements remained a major control on marine paleogeography for &amp;gt;200 m.y. into the late Paleozoic.

Sedimentary Records of Phytoplankton Communities in Sanmen Bay in China: The Impacts of ENSO Events over the Past Two Centuries

Phytoplankton communities, showing significant spatiotemporal variation within bay areas, play an important role in the structure and function of nearshore marine ecosystems. However, the absence of long-term high-resolution datasets has hindered our understanding of the effect of ENSO-driven environmental changes on phytoplankton communities in coastal ecosystems. Herein, by performing biomarker inversion analyses on two centuries’ worth of sedimentary organisms in the Sanmen Bay area, we observed a marked El Niño/La Niña-related succession; specifically, that El Niño-induced warming had increased the biomass of phytoplankton by 57.89%, while also increasing the proportion of diatoms by 76.40%. In contrast, La Niña years exhibited a decrease in the biomass of phytoplankton by 54.23%. Further, over three decades of observational data from the Sanmen Bay suggest that La Niña years can promote occasional blooms through monsoonal mixing and land-based inputs. Consequently, the nearshore marine ecosystem of the bay area, being subject to intense anthropogenic activity and land–sea interactions, can be said to be influenced by global-scale ocean–atmosphere processes. Going forward, the connection between short-term extreme events and long-term changes in the nearshore marine ecosystem should receive greater attention.