Lower Trophic Level Species Research Articles

What is happening to the European Union aquaculture production? Investigating its stagnation and sustainability

While global aquaculture production has been highly successful in terms of production growth in recent decades, most developed countries including the European Union (EU) have not participated in this development to a significant extent. As recently as the 1970s, several EU countries were global leaders in aquaculture production, primarily focusing on filter feeders such as mussels and oysters. However, aquaculture production in the EU has largely stagnated over the past few decades. Despite political support, investment and research efforts over the last three decades, environmental regulations and competition with other activities have slowed down or even halted production growth in many cases. Recent EU legislation aimed at boosting food security and sustainable food systems, recognise aquaculture as a major potential contributor, focusing for example on sustainable or low environmental impact aquaculture, e.g. the production of low trophic level species. In this context, this article aims to contribute to the understanding of the EU aquaculture sector by examining the stagnation in production and its causes. We investigate the evolution of the EU aquaculture production in weight and value, as well as its average trophic level, length and diversity of the species produced. Results indicate an increase in the diversity of species produced, but a decline in the production of low trophic level species over the last two decades, and an increase in more challenging high trophic levels species, raising the overall average trophic level of the production. The decline in mussel and oyster production is mainly due to environmental and, to a lesser degree, economic factors. The rapid growth of carnivorous fish, such as seabream, seabass and salmon has slowed down since 2000, mainly due to regulations aiming at limiting environmental impacts.

Quantification of finfish assemblages associated with mussel and seaweed farms in southwest UK provides evidence of potential benefits to fisheries

Low trophic aquaculture, including shellfish and seaweed farming, offers a potentially sustainable food source and may provide additional environmental benefits, including the creation of new feeding, breeding and nursery areas for fish of commercial and ecological importance. However, quantitative assessments of fish assemblages associated with aquaculture sites are lacking. We used pelagic baited remote underwater videos (BRUVs) and hook and line catches to survey summer fish assemblages at 2 integrated blue mussel Mytilus edulis and kelp (predominantly Saccharina latissima) farms in southwest UK. We recorded at least 11 finfish species across the surveys, including several of commercial importance, with farmed mussels and/or kelps supporting significantly higher levels of abundance and richness than reference areas outside farm infrastructure. Farmed kelp provided temporary habitat due to seasonal harvesting schedules, whereas farmed mussels provided greater habitat stability due to overlapping interannual growth cycles. Stomach content analysis of fish caught at the farms revealed that some low trophic level species had high proportions of amphipods in their stomachs, which also dominated epibiont assemblages at the farms. Higher trophic level fish stomachs contained several lower trophic level fish species, suggesting that farms provide new foraging grounds and support secondary and tertiary production. Although not identified to species level, juvenile fish were abundant at both farms, suggesting potential provisioning of nursery or breeding grounds; however, this needs further verification. Overall, this study provides evidence that shellfish and seaweed aquaculture can support and enhance populations of commercially and ecologically important fish species through habitat provisioning.

A diagnosis of the artisanal fishery landings in the Colombian Caribbean coast by means of indicators

Landings of the artisanal fishery in the Colombian Caribbean from 2013 to 2021 were characterized by means of two indicators: the trophic level and the vulnerability to fishery landings. Indicators showed a statistically significant decreasing trend in vulnerability and trophic level, suggesting that the fishery is increasingly targeting species of low vulnerability and trophic level, thus moving down the food web. The overall pattern of indicators was not uniform in space. Incidence interaction of gears and species landed explained the trajectory of indicators at the scale of Departments. Fishing gears targeted different levels in the food web, with gillnets responsible for the bulk of landings. Compared to a previous study, the group of fish species supporting most of landings has changed towards species with lower vulnerability, i.e. resistant to fishing mortality due to their evolved life-history but still of predatory habits in general. A notable exception is Mugil incilis, a species with a low trophic level that has become third in importance of landings in the database.

Trophic distribution of nutrient production in coral reef fisheries.

Coral reef fisheries supply nutritious catch to tropical coastal communities, where the quality of reef seafood is determined by both the rate of biomass production and nutritional value of reef fishes. Yet our understanding of reef fisheries typically uses targets of total reef fish biomass rather than individual growth (i.e. biomass production) and nutrient content (i.e. nutritional value of reef fish), limiting the ability of management to sustain the productivity of nutritious catches. Here, we use modelled growth coefficients and nutrient concentrations to develop a new metric of nutrient productivity of coral reef fishes. We then evaluate this metric with underwater visual surveys of reef fish assemblages from four tropical countries to examine nutrient productivity of reef fish food webs. Species' growth coefficients were associated with nutrients that vary with body size (calcium, iron, selenium and zinc), but not total nutrient density. When integrated with fish abundance data, we find that herbivorous species typically dominate standing biomass, biomass turnover and nutrient production on coral reefs. Such bottom-heavy trophic distributions of nutrients were consistent across gradients of fishing pressure and benthic composition. We conclude that management restrictions that promote sustainability of herbivores and other low trophic-level species can sustain biomass and nutrient production from reef fisheries that is critical to the food security of over 500 million people in the tropics.

Fishery catch is affected by geographic expansion, fishing down food webs and climate change in Aotearoa, New Zealand.

Historical fishing effort has resulted, in many parts of the ocean, in increasing catches of smaller, lower trophic level species once larger higher trophic level species have been depleted. Concurrently, changes in the geographic distribution of marine species have been observed as species track their thermal affinity in line with ocean warming. However, geographic shifts in fisheries, including to deeper waters, may conceal the phenomenon of fishing down the food web and effects of climate warming on fish stocks. Fisheries-catch weighted metrics such as the Mean Trophic Level (MTL) and Mean Temperature of the Catch (MTC) are used to investigate these phenomena, although apparent trends of these metrics can be masked by the aforementioned geographic expansion and deepening of fisheries catch across large areas and time periods. We investigated instances of both fishing down trophic levels and climate-driven changes in the geographic distribution of fished species in New Zealand waters from 1950-2019, using the MTL and MTC. Thereafter, we corrected for the masking effect of the geographic expansion of fisheries within these indices by using the Fishing-in-Balance (FiB) index and the adapted Mean Trophic Level (aMTL) index. Our results document the offshore expansion of fisheries across the New Zealand Exclusive Economic Zone (EEZ) from 1950-2019, as well as the pervasiveness of fishing down within nearshore fishing stock assemblages. We also revealed the warming of the MTC for pelagic-associated fisheries, trends that were otherwise masked by the depth- and geographic expansion of New Zealand fisheries across the study period.

Three decades of research on Iberian wild Carnivora: trends, highlights, and future directions

ABSTRACT Mammalian carnivores (Carnivora) are crucial components of landscapes, because of both their top‐down effects on lower trophic level species and their sensitivity to bottom‐up processes, such as limited food resources (e.g. due to climate instability). To understand their functional role in Iberian ecosystems more clearly, and to define effective plans for their management and conservation, it is crucial to sum up the available regional knowledge that can inform decision‐making processes. We review bio‐ecological research on wild Iberian carnivores over 30 years (1990–2020) and identify key knowledge gaps and priority avenues for future research. Based on a systematic review of the scientific literature, we aimed to: 1) summarise current knowledge; 2) assess species and ecoregion representativeness; 3) identify key research topics addressed and those lacking investment and 4) suggest key future research priorities. We examined 920 peer‐reviewed articles involving wild Iberian mammalian carnivores, focusing on different bio‐ecological issues. We found considerable heterogeneity in the topics and species investigated, as well as in the study areas (ecoregions) explored, with a mismatch between the research priorities identified by researchers and the knowledge gaps. We suggest that future research should prioritise: 1) rear‐edge populations that are at the southwestern limits of the species' Eurasian range, thus being particularly sensitive to the increasing fragmentation and aridity of Iberian ecosystems, and that were less studied (e.g. brown bear Ursus arctos, stoat Mustela erminea, European mink Mustela lutreola and pine marten Martes martes); 2) less‐studied topics, such as morphometry and body condition, ecophysiology, and reproductive biology, all of which provide essential information for species' management and conservation and 3) specific ecoregions for which studies on species' adaptations to environmental and anthropic contexts are lacking (e.g. northern ecoregions of Iberia, Iberian conifer forests and Northwest Iberian montane forests). Our review provides the necessary background to support future research on carnivore populations in Iberia.

Evaluation of the toxicity of clozapine on the freshwater diatom Navicula sp. using the FTIR spectroscopy

Clozapine is an often prescribed neuroactive pharmaceutical and frequently detected in the aquatic environments. However, its toxicity on low trophic level species (i.e., diatoms) and associated mechanisms are seldom reported. In this study, the toxicity of clozapine on a widely distributed freshwater diatom Navicula sp. was evaluated using the FTIR spectroscopy along with biochemical analyses. The diatoms were exposed to various concentrations of clozapine (0, 0.01, 0.05, 0.10, 0.50, 1.00, 2.00, 5.00 mg/L) for 96 h. The results revealed that clozapine reached up to 392.8 μg/g in the cell wall and 550.4 μg/g within the cells at 5.00 mg/L, suggesting that clozapine could be adsorbed extracellularly and accumulated intracellularly in diatoms. In addition, hormetic effects were displayed on the growth and photosynthetic pigments (chlorophyll a and carotenoid) of Navicula sp., with a promotive effect at concentrations less than 1.00 mg/L while an inhibited effect at concentrations over 2 mg/L. Clozapine induced oxidative stress in Navicula sp., accompanied by decreased levels of total antioxidant capacity (T-AOC) (>0.05 mg/L), in which, the activity of superoxide dismutase (SOD) (at 5.00 mg/L) was increased whereas the activity of catalase (CAT) (>0.05 mg/L) was decreased. Furthermore, FTIR spectroscopic analysis showed that exposure to clozapine resulted in accumulation of lipid peroxidation products, increased sparse β-sheet structures, and altered DNA structures in Navicula sp. This study can facilitate the ecological risk assessment of clozapine in the aquatic ecosystems.

The carrying capacity of the seas and oceans for future sustainable food production: Current scientific knowledge gaps

AbstractThe expected increase in global food demand, as a consequence of a rising and wealthier world population, and an awareness of the limits and drawbacks of modern agriculture, has resulted in a growing attention to the potential of the seas and oceans to produce more food. The capture production of presently exploited marine fish stocks and other species has more or less reached its maximum and can only be slightly improved by better management. This leaves four alternative options open to increase marine food production: (1) manipulating the entire food web structure via removal of high trophic level species to allow an increasing exploitation of low trophic level species, (2) harvesting so far unexploited stocks, such as various fish species from the mesopelagic zone of the ocean or the larger zooplankton species from polar regions, (3) low‐trophic mariculture of seaweeds and herbivorous animals, and (4) restoration of impoverished coastal ecosystems or artificially increasing productivity by ecological engineering. In this paper, we discuss these four options and pay attention to missing scientific knowledge needed to assess their sustainability. To assess sustainability, it is a prerequisite to establish robust definitions and assessments of the biological carrying capacity of the systems, but it is also necessary to evaluate broader socio‐economic and governance sustainability.

Ecological networks of an Antarctic ecosystem: a full description of non-trophic interactions

Interactions between organisms are diverse and attend to multiple biological demands; hence, understanding ecological communities requires considering different types of species interactions beyond predation. In this work, we assembled the non-trophic networks of a marine Antarctic ecosystem for the first time. We report mutualistic (+ / +), competitive (− / −), commensalistic (+ /0) and amensalistic (− /0) interactions between species of the Potter Cove marine community (South Shetland Is., Antarctica). Based on a network approach, we present a full description of each type of interaction and analyze its distribution according to different species-level properties. Also, we constructed a multiple interactions network including trophic and non-trophic interactions and studied network-level properties. We found more than double non-trophic interactions than trophic mostly corresponding to competitive interactions that mainly involve mid-trophic level species. Low-trophic level species were mainly involved in mutualistic and amensalistic interactions. We observed that single-type interaction networks display differences in their topology. Finally, we highlight that including a description of species interactions in ecological network analyses provides a better understanding of ecosystems which it is crucial to comprehend and predict ecosystems responses to environmental changes.

Carbon Transfer Efficiency and Risk of Fisheries Collapse in Three Large Marine Ecosystems Around China

Fisheries catch is determined by a complex combination of biological and industrial factors. In this study, using data from the online database Sea Around Us from 1950 to 2018, the risk of fisheries collapse was assessed for the three large marine ecosystems (LMEs) around China by analyzing the carbon transfer efficiency, mean trophic level, and mean maximum length of fisheries catch and expansion factor. In addition, these were compared with the corresponding values for other LMEs, especially the Humboldt Current and the North Sea LMEs, which experienced fisheries collapse.Our results revealed high carbon transfer efficiencies in LMEs around China, suggesting large fishing efforts compared with LMEs with similar primary production. Although marine fish landings did not decline significantly, they were maintained by potential resources associated with offshore and deep expansion and fishing of lower–trophic-level species and juvenile fish. However, the potential resources have been largely consumed in the East China Sea and South China Sea LMEs, where the ratio of the primary production required to sustain catches to the total primary production (%PPR) was greater than 50%. In contrast, this ratio in the Yellow Sea LME was lower; however, this value was still higher than the sustainable ratio in the Humboldt Current LME. Without proper fisheries management, the three fisheries around China are likely to collapse, as observed in case of the North Sea LME in the 1970s.

Comparison of Marine Ecosystems of Haizhou Bay and Lvsi Fishing Ground in China Based on the Ecopath Model

Recently, under the impacts of environmental shifts and human activities, marine ecosystem conservation and recovery have become increasingly important for the management and sustainable development of fishery resources. We construct two Ecopath models to describe and compare the similarities and differences in the structure and function of the ecosystems in Haizhou Bay (HZB) for 2020–2021 and Lvsi Fishing Ground (LSFG) for 2018–2019 in this study. Our results highlight the similarities of the two ecosystems in which plankton (e.g., zooplankton and phytoplankton) are important functional groups with bottom-up effect control and congers control the top-down effect. The differences between the two ecosystems indicate that the HZB ecosystem is relatively mature due to higher Finn’s cycling index (FCI), Finn’s mean path length (FMPL), Connectance Index (CI), System Omnivory Index (SOI), and Ascendency/capacity (A/C). However the food web structure in the LSFG is more diverse and stable with higher Overhead/capacity (O/C) and Overhead/capacity (H). The differences are possibly due to the low trophic level (TL) species composition in the two ecosystems. Therefore, we suggest that stock enhancement and release methods should be deployed to release high TL species into designated water areas to increase food web complexity and ecosystem maturity in HZB and LSFG. This study will help inform ecosystem and fishery regulations in different ways and facilitate discussion towards the establishment of strategic conservation planning and adaptive management.

Trophic interactions at avian carcasses: Do scavengers feed on vulture carrion?

Scavenging is a pervasive foraging strategy among vertebrates, yet researchers have only recently begun to reveal the complex implications of scavenging dynamics. Scavenging studies have predominantly used lower trophic level (i.e., herbivore) species as carrion bait, and the few studies that have used higher trophic level (i.e., carnivore) carrion have found these carcass types are generally avoided by vertebrates or scavenged by fewer species than similarly sized herbivore carcasses. No studies have assessed the fate of carcasses of obligate scavengers. To investigate potential differences in scavenging dynamics among avian carrion representing different guilds and trophic levels, we conducted scavenging trials using 20 replicates of two obligate scavenger species (i.e. black vulture, Coragyps atratus; turkey vulture, Cathartes aura) and two lower trophic level species, chicken (Gallus gallus domesticus), and mallard (Anas platyrhynchos). Carcass trials were conducted at the Savannah River Site, SC, USA, and monitored with remote cameras. We hypothesized carcasses of vultures would persist longer and have a distinct scavenging community compared to lower trophic level carcasses (mallard and chicken). As expected, turkey and black vulture carcasses persisted in the environment longer, were less likely to be entirely consumed by vertebrate scavengers, and had a different scavenging community than mallard and chicken carcasses. These results contribute to the growing body of evidence suggesting higher trophic level carrion is exploited differently by vertebrate scavengers. Our findings suggest nutrients derived from vulture carcasses are likely largely reincorporated into lower trophic levels.

Small-scale fisheries of the Bons Sinais Estuary in Mozambique with emphasis on utilization of unselective gear

Small-scale fisheries in estuaries of the Western Indian Ocean form a key component of socio-ecological systems (SES) and food security, yet they remain poorly understood. This study describes the estuarine fisheries of the Bons Sinais Estuary in Mozambique based on fisheries and biological data collected by monitors between 2007 and 2016. Multiple gears were used, including beach seines (78 % of sampled fish), chicocota nets (12 %), gillnets (5 %), and hook and line (4 %). Landings were dominated by small pelagic fishes (Engraulidae 29 %, Pristigasteridae 16 %, Clupeidae 11 %) and prawns (Penaeidae 29 %). Monthly averaged fishing effort, landings and catch per unit effort of beach seine and chicocota nets peaked during the dry season, in April and July to October. The proportion of penaeid prawns in landings increased moderately at the end of the wet season, between January and March. The species and size composition selected by beach seine and chicocota nets overlapped, with chicocota nets also retaining marginally smaller individuals. Both gears exploited low trophic level species near the base of the food web, with low trophic values of 2.8 for chicocota and 3.0 for beach seine nets. The small-scale fishery in the Bons Sinais Estuary followed a ‘balanced harvest’ approach in which unselective fishing gear is used to exploit a mix of species and sizes proportional to natural productivity and relative abundance.

Intrinsic and extrinsic motivations governing prey choice by hunters in a post-war African forest-savannah macromosaic.

Overhunting typically increases during and after armed conflicts, and may lead to regional-scale defaunation. The mitigation of hunting impacts is complex because, among other reasons, several intrinsic and extrinsic motivations underpin the elevated deployment of hunting practices. Here we present the first study focusing on these motivations in a post-war zone. Following persistently heavy hunting pressure during the 27-year Angolan civil war, the offtake of small to medium-bodied species has increased recently as a result of large mammal depletion. However, prey choice associated with different motivations varied in terms of species trophic level and body size. While most residents hunted large-bodied species to maximize revenues from wildlife trade, many low-trophic level smaller species were harvested to meet local subsistence demands because they were more palatable and could be captured using artisanal traps near hunters' households. Mainly low-trophic level species were killed in retaliation for crop-raiding or livestock depredation. Considering all game species sampled in this study, 96% were captured to attend two or more motivations. In addition, hunting associated with different motivations was partitioned in terms of age and gender, with prey acquisition for the wildlife trade primarily carried out by adult men, while hunting to meet local subsistence needs and inhibit human-wildlife conflicts were carried out by adult men and women, children and even the elderly. In natural savannah areas lacking fish as a source of protein, a higher number of species was selected to supply both the meat trade and subsistence, while more species in forest areas were targeted for trade in animal body parts and conflict retaliation. Finally, local commerce in bushmeat and other body parts accrued higher domestic revenues compared to any alternative sources of direct and indirect income. However, these financial benefits were at best modest, largely unsustainable in terms of prey population collapses, and generated high long-term costs for the local to regional scale economy and native biodiversity.

Assessing the Fisheries and Ecosystem Structure of the Largest Greek Lake (Lake Trichonis)

An Ecopath with Ecosim (EwE) modeling approach was used to explore the ecological structure of the largest lake in Greece (Lake Trichonis). Until the mid-1990s, the lake was receiving a high level of pollution and the fishing pressure was intense, while since the early 2000s, fisheries and other human pressures gradually declined. Nowadays, the lake’s fisheries mainly target Atherina boyeri due to the absence of market demand for the other fish species in the lake, resulting in a low overall fisheries pressure on the fish stocks. The model was built with data collected through: (a) field samplings, (b) in-depth targeted interviews of professional fishermen and (c) historical archive information. The model considered 22 functional groups, while fishing activities were represented by three classes according to the used gears. The outputs of the model revealed that the ecosystem is dominated by low trophic level species (also identified as keystone species), indicating the significance of bottom-up control in the regulation of food web processes. Ecological indicators depicted that the lake’s ecosystem is mature and resilient to external disturbances. The methodological approach used in this study was shown to be helpful for studies addressing ecosystem structure, in particular with limited data availability.

Balanced harvest as a potential management strategy for tropical small-scale fisheries

AbstractTropical small-scale fisheries (SSFs) are characterised by their multidimensionality (fleets, gears, habitats, and species). As many targeted species move between habitats throughout their life cycle, managing coexisting fleets exploiting the same resource is challenging. However, the SSFs operating over multiple habitats target a variety of species and sizes and could benefit from a management strategy such as balanced harvest (BH)—harvesting all species and sizes in proportion to their production rate. To test this hypothesis, we characterised the fishing pattern (distribution of overall fishing pressure on species and sizes) of northeast Brazil SSFs targeting migratory species along an estuarine-shelf break gradient. Specifically, we described the relative captures by gear type and developed a conceptual model to understand fishers’ strategies. All ontogenetic classes of the twelve selected species were caught along the estuary-shelf break gradient, achieving a fishing pattern in line with BH. Young individuals and low trophic level species predominated in most gears. In that context, size limitations would not be sufficient to prevent overfishing and could prejudice the fleets that target small sizes. An ecosystem-based approach like BH, aiming to regulate the overall fishing pressure and consistent with the existing fishing pattern, should instead be promoted.

Integrating multiple chemical tracers to elucidate the diet and habitat of Cookiecutter Sharks

The Cookiecutter shark (Isistius brasiliensis) is an ectoparasitic, mesopelagic shark that is known for removing plugs of tissue from larger prey, including teleosts, chondrichthyans, cephalopods, and marine mammals. Although this species is widely distributed throughout the world’s tropical and subtropical oceanic waters, like many deep-water species, it remains very poorly understood due to its mesopelagic distribution. We used a suite of biochemical tracers, including stable isotope analysis (SIA), fatty acid analysis (FAA), and environmental DNA (eDNA), to investigate the trophic ecology of this species in the Central Pacific around Hawaii. We found that large epipelagic prey constituted a relatively minor part of the overall diet. Surprisingly, small micronektonic and forage species (meso- and epipelagic) are the most important prey group for Cookiecutter sharks across the studied size range (17–43 cm total length), with larger mesopelagic species or species that exhibit diel vertical migration also being important prey. These results were consistent across all the tracer techniques employed. Our results indicate that Cookiecutter sharks play a unique role in pelagic food webs, feeding on prey ranging from the largest apex predators to small, low trophic level species, in particular those that overlap with the depth distribution of the sharks throughout the diel cycle. We also found evidence of a potential shift in diet and/or habitat with size and season. Environmental DNA metabarcoding revealed new prey items for Cookiecutter sharks while also demonstrating that eDNA can be used to identify recent prey in stomachs frozen for extended periods. Integrating across chemical tracers is a powerful tool for investigating the ecology of elusive and difficult to study species, such as meso- and bathypelagic chondrichthyans, and can increase the amount of information gained from small sample sizes. Better resolving the foraging ecology of these mesopelagic predators is critical for effective conservation and management of these taxa and ecosystems, which are intrinsically vulnerable to overfishing and exploitation.

Applying abundance/biomass comparison curves to small mammals: a weak tool for detect urbanization-related stress in the assemblages?

Abstract Urbanization is a form of pervasive human-induced disturbance. We tested the effectiveness of Abundance/Biomass Comparisons (ABC) as an approach in detecting stress due to landscape urbanization in large small mammal assemblages obtained from pellets of Barn Owl (Tyto alba; Strigiformes). We compared three assemblages sampled in not urbanized contexts (agro-mosaic landscapes) with three assemblages preyed in highly urbanized contexts. In all assemblages, the role of strictly synanthropic species (in our case: rodents) emerged since almost all of total biomass was assigned to these species: indeed, everywhere (both in agro-mosaic and urbanized sites) species of low trophic level (i.e. omnivorous/herbivorous rodents) significantly prevail in biomass when compared to insectivorous species (i.e. shrews, Soricomorpha) linked to less anthropized habitats. This biomass dominance in rodent species is highlighted by the data on evenness, showing lower values in biomass when compared to abundance. This pattern did not match with the classic assumption expressed by the ABC model (i.e., species with higher biomass are typical of undisturbed assemblage) and could be wrongly interpreted. Our study evidenced as ABC approach is a not reliable tool to detect the effect of urbanization as landscape disturbance acting on small mammal assemblages. Therefore we suggest that the ABC assumptions are not universal but limited only to assemblages where high body mass species coincide to species of a higher trophic level.

Effects of tris (2-chloroethyl) phosphate (TCEP) on growth, reproduction and gene transcription in the protozoan Tetrahymena thermophila

As a typical organophosphorus flame retardant, tris (2-chloroethyl) phosphate (TCEP) has been widely detected in various environmental media. Toxicity of TCEP to vertebrates have been investigated, but potential effects on lower trophic level species were unknown to date. In this study, toxic effects and molecular mechanisms of toxic actions of TCEP on the aquatic protozoan Tetrahymena thermophila were evaluated by use of phenotypic observations, transcriptome sequencing analysis and real-time quantitative PCR detection. Exposure to 0.044, 0.411 or 4.26 mg/L TCEP for 5 days decreased the theoretical population, cell viability, number of cilia and cell size of Tetrahymena thermophila in a time- and dose-dependent manner. Meanwhile, RNA-Seq analysis indicated that exposure to 4.26 mg/L TCEP significantly changed expression of 2932 genes (up-regulation: 1228; down-regulation: 1704). Of these, expressions of 9, 10 and 17 genes that were enriched in soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) interaction in vesicular transport, proteasome and endocytosis pathway respectively were down-regulated. Data collected during this study suggested that exposure to high concentrations of TCEP might affect growth and reproduction of Tetrahymena thermophila through down-regulating transcriptional levels of genes encoding proteins associated with vesicle trafficking, proteasome and endocytosis.

Coupled trophic and contaminant analysis in seabirds through space and time

Wildlife contaminant loads are often used to indicate ecosystem health, but their interpretation is complicated by the dynamics affecting the trophic transfer of toxins. Yet, coupled analyses of trophic position and contaminants may provide insights that help resolve the underlying signal of contaminants in ecosystems. Here, we analyze heavy metal concentrations and trophic positions for pelagic seabirds across time and space. We derive metal-specific trophic transfer coefficients from the literature and use them to interpret the changes in raw heavy metal concentrations in two settings: (i) for eight seabird species across a 125-year timeline in Hawaii, and (ii) for contemporary specimens of two tern species across three ocean basins. While previous studies report how trophic position varies in these two settings, here we investigate how trophic downgrading may affect the observed raw changes in contaminants. Using this approach, we find the highly-toxic metal elements (Hg, As, Pb) decline after 1980. However, several other metals (Cu, Mn, Mo, Cd, Fe) increase from 1990–2015. Though simultaneous biomagnification and trophic downgrading may obscure contaminant analyses across space and time, the trophic declines we observed (≤0.5 trophic level) are likely not sufficient to influence such comparisons. In addition, as extrapolating contaminant concentrations across broad ranges of trophic levels may be prone to large uncertainties, careful selection of the focal species for analysis is required. While high trophic level species, such as long-lived, fish-eating seabirds, are ideal for monitoring environmental contaminants across large spatial or time scales, lower trophic level species, like primary producers and consumers, may be more suitable for quantifying the concentrations of bio-available contaminants entering the marine ecosystem and the base of the marine food webs. Monitoring low and high trophic levels simultaneously may provide an integrated perspective that is needed to quantify the contaminants entering and bio-magnifying through marine ecosystems.