Food-limited Environment Research Articles

Influence of single-species and species-species competitive interactions, in a food limited environment, among certain stored-grain beetles on population size and grain weight losses

Resource competition is a common biotic factor that affects progeny production and population size of stored-grain beetles. Larvae of the external feeding competitors, Tribolium, Oryzaephilus, and Trogoderma have almost identical habits, all developing and feeding outside grains Trogoderma larvae therefore are likely to face the competition of both competitors that share the same habitat, with the possibility of displacement of one or both of these species from the habitat. A series of trials of the single-, two-, and three-species competitive interactions among Trogoderma granarium, Tribolium castaneum, and Oryzaephilus surinamensis beetles were performed in 20g cracked-wheat grains at 30 ± 1 °C and 65 ± 5% r.h. Population sizes of living individuals, total populations (living + dead), and grain losses in all combinations were estimated after 30 and 60 days. This was to understand the role of external competitors in T. granarium establishment and vice versa. The population size of Trogoderma benefited more from coexisting with Oryzaephilus than with Tribolium, whereas that of Oryzaephilus did not benefit from coexisting with either species. Each of Trogoderma and Tribolium inhibited development of Oryzaephilus with more suffering in the treatment containing the two, which eventually led to greater collapse in Oryzaephilus populations. However, path analysis of the population growth rates of each species in pure and mixed infestations indicates coexistence is possible between all species and mixed infestations are more harmful to the grains than pure ones, since there are positive associations among them.

Pseudo-chromosome-length genome assembly for a deep-sea eel Ilyophis brunneus sheds light on the deep-sea adaptation.

High hydrostatic pressure, low temperature, and scarce food supply are the major factors that limit the survival of vertebrates in extreme deep-sea environments. Here, we constructed a high-quality genome of the deep-sea Muddy arrowtooth eel (MAE, Ilyophis brunneus, captured below a depth of 3,500 m) by using Illumina, PacBio, and Hi-C sequencing. We compare it against those of shallow-water eel and other outgroups to explore the genetic basis that underlies the adaptive evolution to deep-sea biomes. The MAE genome was estimated to be 1.47 Gb and assembled into 14 pseudo-chromosomes. Phylogenetic analyses indicated that MAE diverged from its closely related shallow-sea species, European eel, ∼111.9 Mya and experienced a rapid evolution. The genome evolutionary analyses primarily revealed the following: (i) under high hydrostatic pressure, the positively selected gene TUBGCP3 and the expanded family MLC1 may improve the cytoskeleton stability; ACOX1 may enhance the fluidity of cell membrane and maintain transport activity; the expansion of ABCC12 gene family may enhance the integrity of DNA; (ii) positively selected HARS likely maintain the transcription ability at low temperatures; and (iii) energy metabolism under a food-limited environment may be increased by expanded and positively selected genes in AMPK and mTOR signaling pathways.

Sociality is a key driver of foraging ranges in bees

Bees are important pollinators of wild and agricultural plants1,2,3,4,5 and there is increasing evidence that many bee populations decline due to a combination of habitat loss, climate change, pesticides, and other anthropogenic effects.6,7,8,9,10,11 One trait that shapes both their role in plant reproduction12,13 and their exposure to anthropogenic stressors is the distance at which bees forage. It has been suggested that bee sociality14 and diet15 affect bee foraging ranges, but how these traits and their potential interactions drive foraging ranges remains unclear. We analyzed flight distance data from 90 bee species and developed an agent-based model to test how social, dietary, and environmental factors affect foraging ranges. We confirm that bee sociality is positively associated with foraging range, with average-sized social bees foraging up to 3 times farther from the nest than size-matched solitary bees. A comparative analysis of social bees and computer simulations shows that foraging distances increase with colony size, supporting the hypothesis that greater foraging distances are an emergent property of increasing colony sizes in a food-limited environment. Flower constancy and communication, two traits often found in social bees, synergistically increase foraging distances further in many simulated environments. Diet breadth (oligolectic versus polylectic diet), on the other hand, does not appear to affect foraging ranges in solitary bees. Our findings suggest that multiple traits linked to bee sociality explain why social bees have greater foraging ranges. This has implications for predicting pollination services and for developing effective conservation strategies for bees and isolated plant populations.15,16,17,18,19.

Insular nestling growth and its relationship to parental care effort in Silvereyes, Zosterops lateralis

ABSTRACT The rate at which avian offspring grow can have consequences for survival and reproductive output as an adult and is known to vary widely among and within species. This variation is thought to be an adaptive response to cope with environmental variation. The principal environmental factors affecting growth are food availability and predation risk, predominantly acting as constraints on parental care. Islands pose an interesting system to explore growth rate dynamics, because the characteristic insular features of high population densities and depauperate predator diversity translate into a potentially food limited environment with low predation risk. Insular environments typically produce populations with slower life history strategies and larger body size in small-bodied species, features that are likely to be mediated by growth rate. We describe the nestling growth of an insular population of Silvereyes and how it relates to parental size and parental care. Neither parental size nor parental care explained insular nestling growth rate, even though food acquisition is thought to underpin avian growth rates. This could be due to a mismatch between acquisition and allocation of resources by nestlings. Compared to a small number of mainland nestlings, the island growth curve asymptotes were significantly larger and inflection points much later, but insular growth rates were only marginally slower. This is in line with proposed insular adaptations required to produce larger body size on islands, however understanding the mechanism underlying this pattern will require data on the relationship between food quality and acquisition, and physiological allocation of resources within individuals.

Growth and Mortality as Causes of Variation in Metabolic Scaling Among Taxa and Taxonomic Levels.

Metabolic rate (MR) usually changes (scales) out of proportion to body mass (BM) as MR=aBMb, where a is a normalisation constant and b is the scaling exponent that reflects how steep this change is. This scaling relationship is fundamental to biology, but over a century of research has provided little consensus on the value of b, and why it appears to vary among taxa and taxonomic levels. By analysing published data on fish and taking an individual-based approach to metabolic scaling, I show that variation in growth of fish under naturally restricted food availability can explain variation in within-individual (ontogenetic) b for standard (maintenance) metabolic rate (SMR) of brown trout (Salmo trutta), with the fastest growers having the steepest metabolic scaling (b≈1). Moreover, I show that within-individual b can vary much more widely than previously assumed from work on different individuals or different species, from -1 to 1 for SMR among individual brown trout. The negative scaling of SMR for some individuals was caused by reductions in metabolic rate in a food limited environment, likely to maintain positive growth. This resulted in a mean within-individual b for SMR that was significantly lower than the across-individual ("static") b, a difference that also existed for another species, cunner (Tautogolabrus adspersus). Interestingly, the wide variation in ontogenetic b for SMR among individual brown trout did not exist for maximum (active) metabolic rate (MMR) of the same fish, showing that these two key metabolic traits (SMR and MMR) can scale independently of one another. I also show that across-species ("evolutionary") b for SMR of 134 fishes is significantly steeper (b approaching 1) than the mean ontogenetic b for the brown trout and cunner. Based on these interesting findings, I hypothesise that evolutionary and static metabolic scaling can be systematically different from ontogenetic scaling, and that the steeper evolutionary than ontogenetic scaling for fishes arises as a by-product of natural selection for fast-growing individuals with steep metabolic scaling (b≈1) early in life, where size-selective mortality is high for fishes. I support this by showing that b for SMR tends to increase with natural mortality rates of fish larvae within taxa.

Context-dependent fitness costs of reproduction despite stable body mass costs in an Arctic herbivore.

The cost of reproduction on demographic rates is often assumed to operate through changing body condition. Several studies have found that reproduction depresses body mass more if the current conditions are severe, such as high population densities or adverse weather, than under benign environmental conditions. However, few studies have investigated the association between the fitness components and body mass costs of reproduction. Using 25years of individual-based capture-recapture data from Svalbard reindeer Rangifer tarandus platyrhynchus, we built a novel Bayesian state-space model that jointly estimated interannual change in mass, annual reproductive success and survival, while accounting for incomplete observations. The model allowed us to partition the differential effects of intrinsic and extrinsic factors on both non-reproductive mass change and the body mass cost of reproduction, and to quantify their consequences on demographic rates. Contrary to our expectation, the body mass cost of reproduction (mean=-5.8kg) varied little between years (CV=0.08), whereas the between-year variation in body mass changes, that were independent of the previous year's reproductive state, varied substantially (CV=0.4) in relation to autumn temperature and the amount of rain-on-snow in winter. This body mass loss led to a cost of reproduction on the next reproduction, which was amplified by the same environmental covariates, from a 10% reduction in reproductive success in benign years, to a 50% reduction in harsh years. The reproductive mass loss also resulted in a small reduction in survival. Our results show how demographic costs of reproduction, driven by interannual fluctuations in individual body condition, result from the balance between body mass costs of reproduction and body mass changes that are independent of previous reproductive state. We illustrate how a strong context-dependent fitness cost of reproduction can occur, despite a relatively fixed body mass cost of reproduction. This suggests that female reindeer display a very conservative energy allocation strategy, either aborting their reproductive attempt at an early stage or weaning at a relatively constant cost. Such a strategy might be common in species living in a highly stochastic and food limited environment.

A simple individual-based population growth model with limited resources

We address a novel approach for stochastic individual-based modelling of a single species population. Individuals are distinguished by their remaining lifetimes, which are regulated by the interplay between the inexorable running of time and the individual’s nourishment history. A food-limited environment induces intraspecific competition and henceforth the carrying capacity of the medium may be finite, often emulating the qualitative features of logistic growth. Inherently non-logistic behaviour is also obtained by suitable change of the few parameters involved, composing a wide variety of dynamical features. Some analytical results are obtained. Beyond the rich phenomenology observed, we expect that possible modifications of our model may account for an even broader scope of collective population growth phenomena.

Differential processing of dissolved and particulate organic matter by deep-sea sponges and their microbial symbionts

Deep-sea sponges create hotspots of biodiversity and biological activity in the otherwise barren deep-sea. However, it remains elusive how sponge hosts and their microbial symbionts acquire and process food in these food-limited environments. Therefore, we traced the processing (i.e. assimilation and respiration) of 13C- and 15N-enriched dissolved organic matter (DOM) and bacteria by three dominant North Atlantic deep-sea sponges: the high microbial abundance (HMA) demosponge Geodia barretti, the low microbial abundance (LMA) demosponge Hymedesmia paupertas, and the LMA hexactinellid Vazella pourtalesii. We also assessed the assimilation of both food sources into sponge- and bacteria-specific phospholipid-derived fatty acid (PLFA) biomarkers. All sponges were capable of assimilating DOM as well as bacteria. However, processing of the two food sources differed considerably between the tested species: the DOM assimilation-to-respiration efficiency was highest for the HMA sponge, yet uptake rates were 4–5 times lower compared to LMA sponges. In contrast, bacteria were assimilated most efficiently and at the highest rate by the hexactinellid compared to the demosponges. Our results indicate that phylogeny and functional traits (e.g., abundance of microbial symbionts, morphology) influence food preferences and diet composition of sponges, which further helps to understand their role as key ecosystem engineers of deep-sea habitats.

Priority determines Tribolium competitive outcome in a food-limited environment.

Flour beetles are a classic model system for studying competitive dynamics between species occupying the same ecological niche. Competitive performance is often interpreted in terms of biological species traits such as fecundity, resource use, and predation. However, many studies only measure competitive ability when species enter an environment simultaneously, and thus do not consider how the relative timing of species’ arrival may determine competitive outcome (i.e., priority effects). Whether priority effects may influence competition in Tribolium remains to be tested. The present study examined the importance of priority effects in competitions between two common species of flour beetle (Coleoptera: Tenebrionidae): Tribolium castaneum and T. confusum. To investigate whether priority effects confer competitive advantages to Tribolium beetles, relative introduction times of T. castaneum and T. confusum to competitive arenas were manipulated, and adult populations were measured for seven months. Four important patterns were noted: (1) Tribolium species given two-weeks priority access to experimental arenas attained larger populations than their late-arriving competitor, (2) when founding adults were introduced simultaneously, T. castaneum was competitively dominant, (3) T. castaneum benefited more from priority arrival than T. confusum, and (4) available bran resources largely predicted population decline in adult beetles toward the end of the experiment. These results suggest competitive outcome in Tribolium is not always predicted by species’ identity, and that performance could instead be determined by the timing of species’ arrivals and available resources.

Dietary separation between co-occurring copepods in a food-limited tropical coral reef of the Sanya Bay

Food differentiation among coexistent species in the field is important strategy for copepods to acquire materials and maintain population stabilization. In situ diet analysis of co-occurring six copepod species in coral waters of the Sanya Bay was conducted using a PCR protocol based on 18S ribosomal gene. Various prey organisms were uncovered, including dinoflagellate, diatom, green algae and plant, protozoa and metazoan. All these spatially coexisting six species showed different dietary diversity, with the food niche breadth (B) ranging from 1.00 (Temora turbinate in morning) to 10.68 (Calanopia elliptica in night). While food overlap between all these copepods were low, with the average value of the diet niche overlap index being approximately 0.09. Even temporally co-existing species sampled from the same time point fed on different groups of prey items with the food overlap index of 0.04 to 0.07 in midday and night but 0 in morning. As the most important dominant copepod in the Sanya Bay, Subeucalanus subcrassus seems to be capable to regulate its feeding, by exhibiting a rhythm of herbivorous feeding in midday and carnivorous feeding in morning and night, to better coordinate with other competitors for utilization of food resources. For most copepods, none of the prey items belonged to the dominant phytoplankton in the ambient water, indicating that copepod can better their survival by widening the choice of potential food resources in food limited environment. The dietary separation observed here might be important strategy for copepod to maintain population stabilization and thriving in the Sanya coastal waters.

Methane Seeps on the US Atlantic Margin and Their Potential Importance to Populations of the Commercially Valuable Deep-Sea Red Crab, Chaceon quinquedens

Methane seeps provide a variety of ecosystem services, including the provision of complex habitat structures and high levels of primary production, which can act as trophic support to non-seep-endemic species in an otherwise food-limited environment. The discovery of hundreds of seeps on the US Atlantic margin, ranging in depth from ~50 to 1700m, provides the opportunity to assess depth-related differences in seep-associated communities. Here, we use photo transects to characterize the megafaunal communities at six seeps along the US Atlantic margin, comparing taxonomic richness and community structure (taxon-abundance patterns) at shallow (~400m) and deep (~1500m) seeps. We use molecular analysis to identify the mussel species present and stable isotope analysis to explore the trophic ecology of bathymodiolin mussels and red crabs (Chaceon quinquedens). Our results suggest a faunal boundary exists between shallow and deep seeps; depth, and the co-varying factor temperature, explained 72% of the variation observed in taxon-abundance patterns. All mussel samples were identified as Bathymodiolus childressi, extending the known dominance of B. childressi at seeps near Baltimore Canyon to seeps off New England. Stable isotope analyses suggest B. childressi relies predominantly, if not entirely, on methane-derived nutrition at both shallow and deep seeps. For red crab, the proportion of methane-derived carbon within muscle tissue is highly variable, contributing ~0% of nutrition for crabs sampled at Shallop East and West but ~30% and ~50% of nutrition for two individuals sampled at Chincoteague East. In addition to red crabs using seeps as a food resource, invertebrate larvae samples and observational data suggests Chincoteague East may act as a reproductive hotspot for red crabs. Fifteen mating pairs, three ovigerous females, and numerous zoea larvae (identified as belonging to C. quinquedens) were observed at or above Chincoteague East, providing what we believe is the first evidence that some seeps may act as a reproductive hotspot for a commercially valuable species. This study highlights two ways that seeps may support fishery productivity (i.e. providing trophic support and increasing reproductive success) and encourages future research exploring the connection between deep-sea chemosynthetic ecosystems and commercially valuable species.

Flipping for Food: The Use of a Methane Seep by Tanner Crabs (Chionoecetes tanneri)

Methane seep habitats are widespread chemosynthesis-based ecosystem that span continental margins and interact with surrounding marine systems. With many of these habitats occurring below 200m, seeps can serve as an important source of nutrients in otherwise food limited deep-sea environments. However, the potential for marauding megafauna to assimilate seep derived nutrition has been difficult to quantify. Here, we provide the first evidence of a commercially harvested species, Chionoecetes tanneri (tanner crab), assimilating chemosynthetic production. Although bulk isotope analysis of C. tanneri tissue indicated no quantifiable incorporation of seep-derived carbon or sulfur (mean δ13C, -18.5‰; mean δ34S, 19.5‰), depletions in 13C (δ13C as light as -38.8 ‰) were noted in fatty acid (FA) compounds. In addition, diagnostic biomarkers for seep bacteria, including 16:16 and 18:18c FA’s, were found to have been assimilated by C. tanneri. Futher supporting a trophic link between the seep and the C. tanneri, seep associated bacteria and archaea were, in certain cases, the dominant taxa in the gut contents of the crab. This work provides the first insights into a link between seep production and deep-sea ecosystem services, specifically fisheries production. In addition, it reveals a methodological bias that could exist in some trophic studies where bulk isotopes under-represent the role of seep nutrition in the diet of marauding animals.

GEOMETRICAL ANALYSIS OF A PEST MANAGEMENT MODEL IN FOOD-LIMITED ENVIRONMENTS WITH NONLINEAR IMPULSIVE STATE FEEDBACK CONTROL

In this paper, a nonlinear impulsive state feedback control system is proposed to model an integrated pest management in food-limited environments. In the system, impulsive feedback control measures are implemented to control pests on the basis of the quantitative state of pests. Mathematically, an intuitive geometric analysis is used to indicate the existence of periodic solutions. The stability of periodic solutions is investigated by using Analogue of Poincare Criterion. At last, numerical simulations are given to verify the theoretical analysis.

Locomotion of Niphargus amphipods from cave lakes and streams

Locomotion is a complex trait directly linked to different fitness components such as foraging, mate-finding, and escaping from predators. In a food-limited subterranean environment a strong selection for an energetically optimal strategy of locomotion is expected and should lead to different strategies among closely related species adapted to different microhabitats. Due to its taxonomic and ecological diversity, the amphipod genus Niphargus is an ideal model system for studying locomotion strategies of species affiliated with different subterranean aquatic microhabitats. Such species differ from each other morphologically, and we predicted that they also evolved alternative strategies of locomotion. In this study, we examined three species from cave lakes and five species from cave streams or springs. After collection all species were first acclimated in a cave laboratory. Then, we video-recorded behaviour in a rectangular open-field arena of approximately 10 individuals per species. A single individual at a time was recorded under red light for 20 minutes. Videos were used to construct ethograms of distinct locomotor behaviours such as swimming, crawling, and walking. A video-tracking analysis was performed to extract variables like total path covered, time spent moving, average and maximal speed. Individuals were euthanized and measured for several morphological traits likely related to locomotion. Additionally, we measured activities of enzymes acetylcholinesterase and glutathione S-transferase, which are likely related to animals’ locomotor and metabolic activity, respectively. Preliminary analyses suggest that species from lakes and streams differ in locomotor behaviour. Interestingly, variation in locomotor behaviour was larger among lake species, possibly implying that selection for the optimal locomotion strategy is stronger and more uniform in streams than in lakes.

Heavy sea louse infection is associated with decreased stomach fullness in wild juvenile sockeye salmon

Foraging success can be mediated by parasites, but this is poorly understood for marine fish whose aggregations and patchy prey fields create conditions for intense intraspecific competition. We evaluated whether sea louse infection is associated with decreased stomach fullness of wild juvenile sockeye salmon (Oncorhynchus nerka) in Johnstone Strait, British Columbia, during their marine migration from the Fraser River. Caligus clemensi comprised 98.6% of the pre-adult and adult lice and 86.5% of the copepodites (freshly attached juvenile lice); the rest were Lepeophtheirus salmonis. We found that infection status was an important predictor of relative stomach fullness for juvenile sockeye (wet stomach content mass divided by body mass), as indicated by mixed-effects model selection, and that highly infected fish had 17% ± 8% lower relative stomach fullness than did lightly infected fish. This louse-associated reduction in relative stomach fullness occurs as the juvenile sockeye migrate through a food-limited environment and, presumably, elevated competition. Given that early marine growth for juvenile salmon is often a predictor of survival, our results highlight the importance of understanding sublethal effects of parasites on salmonids and possibly other fish species.

Clonal fish are more aggressive to distant relatives in a low resource environment

Abstract Kin selection explains conditions under which closely related individuals should be less antagonistic towards one another. One benefit of kin selection is a reduction in aggression towards kin in various social contexts, such as foraging. In the gynogenetic Amazon molly, females have been shown to differentiate between clone types, preferring to associate with clonal sisters to non-sisters, regulating their aggressive behaviours accordingly. We ask if Amazon mollies in resource-limited environments retain the ability to regulate aggressive behaviours according to relatedness. We found that focal females regulated their aggressive behaviours depending on partner type. Females spent more time behaving aggressively towards the heterospecific females than either of the clonal lineages, and towards non-sister clones compared to clonal sisters. We are able to confirm that kin discrimination is maintained, resulting in females showing more aggression towards heterospecific females and non-sister clones in a food-limited environment, and that this aggression scales with relatedness.

Functional response to food limitation can reduce the impact of global change in the deep‐sea benthos

AbstractAimA key paradigm of deep‐sea ecology is that the ocean interior is a food‐limited environment, which limits the faunal growth. Here, we estimated the efficiency of deep‐sea fauna in exploiting resources to assess the potential response of deep‐sea organisms to changes in the food inputs expected with global change.LocationMediterranean Sea.Time period1989–2010.Major taxa studiedViruses, prokaryotes, meiofauna, macrofauna and megafauna.MethodsUsing the largest data set spanning from microbes to megafauna produced synoptically so far, we investigated patterns of abundance, biomass and ecosystem efficiency across depth‐related and longitudinal gradients of food availability in both Western and Eastern Basins of the Mediterranean Sea.ResultsOur results revealed that prokaryotes dominated benthic biomass at depths > 2,000 m. Contrary to what has been reported at a global scale, meiofaunal biomass decreased with increasing water depth more rapidly than macrofauna and megafauna. Meiofauna showed a significant negative log‐linear relationship with increasing water depth in the whole Mediterranean Sea, whereas the other benthic components, from viruses to megafauna, did not decrease significantly, decreased or even increased (e.g., prokaryotes) with increasing water depth. Taking all components together, the efficiency of benthic ecosystems in exploiting organic carbon (OC) inputs increased with increasing depth, in both mesotrophic and ultra‐oligotrophic conditions of the deep Mediterranean Sea.Main conclusionsChanges in ecological efficiency in exploiting the energy available in food‐limited conditions suggest that deep‐sea ecosystems can show a responsive adaptation to changes in OC inputs from the photic zone. Our results contribute to explaining the high efficiency of resource exploitation by consumers in limited trophic conditions and allow us to hypothesize that the consequences of a potential reduction of food supply in deep‐sea ecosystems induced by global changes could be less severe than expected.

Ecosystem engineering creates a direct nutritional link between 600-m deep cold-water coral mounds and surface productivity.

Cold-water corals (CWCs) form large mounds on the seafloor that are hotspots of biodiversity in the deep sea, but it remains enigmatic how CWCs can thrive in this food-limited environment. Here, we infer from model simulations that the interaction between tidal currents and CWC-formed mounds induces downwelling events of surface water that brings organic matter to 600-m deep CWCs. This positive feedback between CWC growth on carbonate mounds and enhanced food supply is essential for their sustenance in the deep sea and represents an example of ecosystem engineering of unparalleled magnitude. This ’topographically-enhanced carbon pump’ leaks organic matter that settles at greater depths. The ubiquitous presence of biogenic and geological topographies along ocean margins suggests that carbon sequestration through this pump is of global importance. These results indicate that enhanced stratification and lower surface productivity, both expected consequences of climate change, may negatively impact the energy balance of CWCs.

Approaches and constraints to the reconstruction of palaeoproductivity from Cape Basin abyssal benthic foraminifera (South Atlantic)

The characteristics of benthic foraminiferal assemblages from well-oxygenated deep-sea settings have been used to reconstruct past productivity conditions. None of the different approaches that have been developed is without complications or applies in all settings. In this study we assess the use of benthic foraminifera (accumulation rates and assemblages composition) as proxies for palaeoproductivity changes during the last glacial period (25 – 95 ka) in an abyssal core located in the south of Cape Basin (41.1 °S, 7.8 °E, 4981 m water depth). Assemblage characteristics indicate a generally food-limited environment receiving episodic inputs of labile organic carbon of variable strength. High seasonality in the delivery of organic material to the seafloor in the form of phytodetritus influences the assemblage characteristics because the corresponding response does not involve the whole community. Benefiting from this occasionally high organic input is the opportunistic species Epistominella exigua (Brady) that reproduces rapidly to build up large populations. In general, the rest of the species (i.e. less opportunistic compared to E. exigua) show only subtle variations in their population densities and fauna composition. Under those circumstances benthic foraminiferal accumulation rates seem to be independent of the amount of organic flux arriving at the sediment surface and respond instead to the strength of phytoplankton blooms.

Cold-water coral reefs and adjacent sponge grounds: hotspots of benthic respiration and organic carbon cycling in the deep sea

Cold-water coral reefs and adjacent sponge grounds are distributed widely in the deep ocean, where only a small fraction of the surface productivity reaches the seafloor as detritus. It remains elusive how these hotspots of biodiversity can thrive in such a food-limited environment, as data on energy flow and organic carbon utilization are critically lacking. Here we report in situ community respiration rates for cold-water coral and sponge ecosystems obtained by the non-invasive aquatic Eddy Correlation technique. Oxygen uptake rates over coral reefs and adjacent sponge grounds in the Traena Coral Field (Norway) were 9-20 times higher than those of the surrounding soft sediments. These high respiration rates indicate strong organic matter consumption, and hence suggest a local focusing onto these ecosystems of the downward flux of organic matter that is exported from the surface ocean. Overall, our results show that coral reefs and adjacent sponge grounds are hotspots of carbon processing in the food-limited deep ocean, and that these deep-sea ecosystems play a more prominent role in marine biogeochemical cycles than previously recognized.