Trophic Structure Of Ecosystem Research Articles

A scalable and normalized reef status index for assessing fish trophic structure reveals conservation gaps

The trophic structure of ecosystems, reflecting biomass distribution across different levels, is paramount for understanding energy dynamics and community assemblages in marine environments. Typically, ecosystems devoid of external energy influx exhibit a bottom-heavy trophic pyramid, yet higher biomass systems often display a top heavy or concave distribution. Such structures are susceptible to alterations due to species turnover, trophic cascades, and anthropogenic impacts, particularly the phenomenon of ’Fishing down’ the food web. Recognizing the trophic structure as a simplified yet potent indicator, we identify the necessity for a standardized, expedient method to assess reef health—a criterion fulfilled by our Normalized Reef Status Index (NRSI). The NRSI offers a novel metric for scientists and conservation practitioners to augment traditional reef health assessments. Utilizing the NRSI, we assessed the ecological status of 346 reefs across the Mexican Pacific. Our results demonstrated that only reefs within Fully Protected areas conform to the concave trophic structure indicative of low human interference. In stark contrast, unprotected reefs exhibited a depleted trophic architecture, often devoid of apex predators. This depletion not only threatens coastal livelihoods and food security but also disrupts the delicate balance of marine ecosystems critical to sustaining global ecological functions. Through the NRSI, we provide a robust, scalable tool for ongoing monitoring and conservation efforts, underscoring the urgent need to address human-induced trophic disruptions.

Gadiform species display dietary shifts in the Celtic Sea

Global changes, through their impacts on ecosystem trophic structures, are behind regime shifts and cascading effects, and could result in the reorganization of whole ecosystems. The Celtic Sea is a temperate sea at risk of the above because of the interplay between climate change and fisheries. This sea has only displayed slight changes in species diversity between the late 20th century and the present day. However, this apparent stability in species diversity could be hiding structural transformations, including the rearrangement of trophic relationships. Historical stomach content database offers the opportunity to investigate changes in ecosystem trophic structure. Based on such database, this study explored shifts in the feeding habits of gadiform species in the Celtic Sea in the 1980s, 1990s, and 2010s. To this end, it examined dietary generalism and composition for four top predator fish species. During the target period, generalists maintained their diets, while specialists adopted more generalist diets. There were also decreases in frequencies of occurrence of certain fishes within the diets of gadiform species. These recent changes in trophic structure organization have likely been caused by the influence of global changes on both top-down and bottom-up processes that occurred in the Celtic Sea.

Size and sex composition of three carcharhiniform sharks landed by a coastal artisanal fleet from the northeastern coast of Brazil

Abstract Sharks are among the marine organisms most impacted by intense fisheries, a worrying fact since they are key components in the trophic structure of ecosystems. In this context, fish landing data can help managers in shark conservation. This study characterized the landings of Carcharhinus acronotus, Mustelus cf. canis, and Sphyrna mokarran in the Mucuripe Embayment, Ceará, Brazil, along three study periods (1998–1999, 2006–2008, and 2015–2016). A total of 223 specimens were recorded from 227 site visits. Carcharhinus acronotus specimens measured from 50 to 139 cm in total length (TL), with a 1.3:1 sex ratio in favor of males. Most of the specimens recorded were adults (55.1% of males and 62.9% of females). Mustelus cf. canis varied from 64 to 133 cm in TL, with a sex ratio in favor of females (3.1:1). Most of the specimens recorded were adults (50% of males and 68% of females). Sphyrna mokarran specimens varied from 116 to 380 cm in TL, with a sex ratio of 7:1 in favor of males. Most of the specimens recorded were juveniles. This is the first fishery-dependent study to provide information on size and sex composition of these species for most of the southwestern equatorial Atlantic.

Biogeochemistry and trophic structure of a cold seep ecosystem, offshore Krishna-Godavari basin (east coast of India)

Active cold seep sites associated with shallow gas hydrates were recently reported from Krishna-Godavari (K-G) basin, off east coast of India. Benthic fauna including chemosymbiotic bivalves (genera Bathymodiolus, Acharax, Conchocele), polychaetes (genus Sclerolinum), and heterotrophs (gastropods: Provannidae family; squat lobster: Munidopsidae/Galatheidae; Goose barnacle: genus Neolepas; Brittle star: genus Amphiodia) were sampled from the cold seep locations. Here, we present the first δ13C and δ15N data sets of the soft tissues extracted from the organisms along with the sediment pore fluid composition. The isotope ratios of the soft tissues provide a glimpse of the potential food sources for the cold seep organisms and the trophic structure of the ecosystem. The δ13C values suggest the dependence of the Bathymodiolus on methanotrophic symbionts, whereas Acharax, Conchocele, and Sclerolinum show the tell-tale signature of the thiotrophic pathways. In contrast, the heterotrophic benthic fauna shows a wide range of δ13C values, a signature of a variety of carbon sources. The δ15N values of the studied organisms also show a broad range (−1 to +9 ‰) indicating variable food sources as well as variable nitrogen assimilation pathways followed by various symbionts.

Tropicalization unlocks novel trophic pathways and enhances secondary productivity in temperate reefs

Abstract The structure of ecological communities is rapidly changing across the globe due to climate‐mediated shifts in species distributions, with novel ecosystem states emerging as new species become dominant. While it is clear that such changes restructure habitat properties and their associated assemblages, how new nutritional resources and consumers may affect the ecosystem trophic structure and energetic dynamics remains poorly resolved. Here, we investigate how the reconfiguration of tropicalized reefs—that is, temperate ecosystems receiving an influx of tropical species—affects the availability of nutritional resources and energy flow through herbivore‐based trophic pathways. To do so, we quantified changes in algal and detrital resources along a tropicalization gradient in eastern Australia. We also estimated energy flow towards herbivorous fishes by quantifying their standing biomass (kg/ha), productivity (kg ha−1 day−1), and biomass turnover (% day−1), using an individual‐level modelling approach that combines estimates of fish growth rates and mortality. Along the gradient, tropicalized reefs had relatively higher amounts of palatable algal turfs and detrital particulates compared to non‐tropicalized sites. Feeding intensity by herbivorous fishes was also c. 400 times higher on tropicalized reefs, with tropical turf‐cropping surgeon fishes being responsible for >98% of the feeding rates. Turf‐driven trophic pathways underpinned virtual all (>99%) of the biomass produced by tropical fishes, which contributed up to 63% of the total herbivorous fish standing biomass and 86% of the productivity despite only representing 35% of the abundance. Turfs also fuelled most of the secondary productivity of tropical fishes on tropicalized reefs across Australia's western tropical–temperate transition zone, although their overall productivity was ~5 times lower. This is possibly due to turfs there containing elevated sediment loads, which dilute the nutritional quality of turf‐based resources, as well as other differences in the biogeographical context. We propose that algal turfs are central drivers of ecosystem energetic shifts on temperate reefs as they become tropicalized because they support novel algal and detrital trophic pathways that enhance secondary productivity and biomass turnover. Our results also suggest that turf characteristics such as organic content or sediment load may emerge as increasingly important drivers of energy flow in temperate locations where turfs dominate benthic cover. A free Plain Language Summary can be found within the Supporting Information of this article.

Ecosystem trophic structure and fishing effort simulations of a major fishing ground in the northeastern Mediterranean Sea (Thermaikos Gulf)

Ecosystem modelling constitutes a useful tool for the ecosystem approach to fisheries management, which demands a shift to more complex models that include multi-species trophic interactions, environmental and anthropogenic forcing. The Thermaikos Gulf is a shallow gulf in the northwestern Aegean Sea (Greece) and one of the major fishing grounds of the northeastern Mediterranean concentrating high fishing effort of trawlers and purse-seiners and producing more than 20% of the total Greek catches. In the present work, we developed an Ecopath base model and ran Ecosim simulations for 26 years (2000–2025), including the calibration period (2000–2016), aiming to describe the food web structure and function of the Thermaikos Gulf, identify main components and interactions among the 33 functional groups, assess the ecosystem impacts of fishing over time, and compare ecosystem properties with other Mediterranean areas. Overall ecosystem degradation with biomass and catch decline was observed at the end of the calibration period due to the impact of environmental factors and fishing activities. The ecosystem seemed to stabilize in an intermediate state by the end of the projection years, but with an overall biomass and catch decline. Fishing effort reduction after 2016 resulted in higher biomass and catches compared to 2014–2015, that could not however reach the 2000 levels in most cases. The examined fishing effort reduction scenarios clearly showed that the more the fishing effort is reduced, the higher the biomass in the ecosystem and the lower the catches obtained compared to the baseline scenario. In a nutshell, since environmental drivers may be harder to predict or control, lowering the exploitation levels is an important step towards the rebuilding of overfished marine resources and more resilient ecosystems.

First screening of biocides, persistent organic pollutants, pharmaceutical and personal care products in Antarctic phytoplankton from Deception Island by FT-ICR-MS

In recent years, the Antarctic territory has seen a rise in the number of tourists and scientists. This has led to an increase in the anthropogenic footprint in Antarctic ecosystems, namely in terms of emerging contaminants, such as Biocides, Persistent Organic Pollutants (POPs) as well as Pharmaceutical and Personal Care Products (PPCPs). Yet scarce information on the presence of these emerging contaminants is available for trophic compartments, especially the phytoplankton community. Using high resolution Fourier-transform ion cyclotron-resonance mass spectrometry (FT-ICR-MS), an untargeted screening of the metabolome of the phytoplankton community was performed. Seventy different contaminant compounds were found to be present in phytoplankton collected at two sites in Port Foster Bay at Deception Island. These emerging contaminants included 1 polycyclic aromatic hydrocarbon (PAH), 10 biocides (acaricides, fungicides, herbicides, insecticides and nematicides), 11 POPs (flame retardants, paints and dyes, polychlorinated biphenyl (PCB), phthalates and plastic components), 5 PCPs (cosmetic, detergents and dietary compounds), 40 pharmaceutical compounds and 3 illicit drugs. Pharmaceutical compounds were, by far, the largest group of emerging contaminants found in phytoplankton cells (anticonvulsants, antihypertensives and beta-blockers, antibiotics, analgesic and anti-inflammatory drugs). The detection of several of these potentially toxic compounds at the basis of the marine food web has potentially severe impacts for the whole ecosystem trophic structure. Additionally, the present findings also point out that the guidelines proposed by the Antarctic Treaty and Protocol on Environmental Protection to the Antarctic Treaty should be revisited to avoid the proliferation of these and other PPCPs in such sensitive environments.

Long-Term Presence of the Island Mass Effect at Rangiroa Atoll, French Polynesia

Enhancement of phytoplankton biomass near island and atoll reef ecosystems—termed the Island Mass Effect (IME)—is an ecologically important phenomenon driving marine ecosystem trophic structure and fisheries in the midst of oligotrophic tropical oceans. This study investigated the occurrence of IME at Rangiroa Atoll in the French Polynesian Tuamotu archipelago, and the physical mechanisms driving IME, through the analysis of satellite and in situ data. Comparison of chlorophyll-a concentration near Rangiroa Atoll with chlorophyll-a concentration in open ocean water 50 km offshore, over a 16-year period, showed phytoplankton enhancement as high as 130% nearshore, over 75.7% of the study period. Our statistical model examining physical drivers showed the magnitude of IME to be significantly enhanced by higher sea surface temperature (SST) and lower photosynthetically active radiation (PAR). Further, in situ measurements of water flowing through Tiputa Channel revealed outflowing lagoon water to be warmer, lower in salinity, and higher in particulate load compared to ocean water. We suggest that water inside Rangiroa’s lagoon is enriched in nutrients and organic material by biological processes and advected as a result of tidal and wave forcing to coastal ocean waters, where it fuels primary production. We suggest that a combination of oceanographic and biological mechanisms is at play driving frequency and magnitude of IME at Rangiroa Atoll. Understanding the underlying processes driving IME at Rangiroa is essential for understanding future changes caused by a warming climate and changing environmental conditions for the marine ecosystem.

Predator-prey body size relationships of cod in a low-diversity marine system

How predators select their prey largely defines ecosystem trophic structure, function and dynamics. In aquatic systems, organism body size is an important trait explaining predator− prey interactions. Here, we used a unique Atlantic cod Gadus morhua stomach content dataset with diet information from over 100 000 individuals collected from the Baltic Sea in 1963−2014, to explore prey size distribution and predator−prey mass ratios in the diet of Eastern Baltic cod. Maximum and average prey sizes increased with predator size, as for cod in other systems. However, the prey size spectra found in Eastern Baltic cod stomachs reflect the low species diversity in the Baltic Sea. In general, Eastern Baltic cod feed on smaller prey in relation to their body size than other cod populations. Due to the truncated prey size distribution in the Baltic Sea, cod cannibalism functions as a compensatory mechanism that allows Baltic cod to reach their prey size potential. On the other hand, small- and intermediate-sized cod prey mainly on a few invertebrate prey species, potentially making them vulnerable to changes in these prey populations. Our results encourage further studies disentangling the relative effects of prey preference and prey availability on cod trophodynamics in species-poor systems such as the Baltic Sea.

Equivalence of trophic structure between a tropical and temperate mangrove ecosystem in the Indo-Pacific

In this study we compared ecosystem trophic structure between a tropical mangrove forest at Matang, Malaysia, and a temperate mangrove forest near mangrove poleward limits at Towra Point in south-east Australia. These forests are separated by 8500km of ocean over 45° of latitude and are of contrasting size, productivity and diversity. However, we observed a marked degree of similarity in food chain length (approximately four trophic levels in both forests), the taxonomy of key intermediate members of the food chain and the isotope signature of primary carbon sources, suggesting a strong contribution of surface organic matter rather than mangrove detritus. Common families were represented among dominant grazing herbivores, zooplanktivorous fishes, decapod crustaceans and top predators. These similarities suggest that there is some consistency in trophic interactions within two mangroves on opposite sides of the Indo-Pacific, despite a degree of evolutionary divergence in the assemblage.

What a Decade (2006–15) Of Journal Abstracts Can Tell Us about Trends in Ocean and Coastal Sustainability Challenges and Solutions

Text mining and analytics may offer possibilities to assess scientists’ professional writing and identify patterns of co-occurrence between words and phrases associated with different environmental challenges and their potential solutions. This approach has the potential to help to track emerging issues, semi-automate horizon scanning processes, and identify how different institutions or policy instruments are associated with different types of ocean and coastal sustainability challenges. Here I examine ecologically-oriented ocean and coastal science journal article abstracts published between 2006 and 2015. Informed by the Institutional Analysis and Development (IAD) framework, I constructed a dictionary containing phrases associated with 40 ocean challenges and 15 solution-oriented instrument or investments. From 50,817 potentially relevant abstracts, different patterns of co-occurring text associated with challenges and potential solutions were discernable. Topics receiving significantly increased attention in the literature in 2014-15 relative to the 2006-13 period included: marine plastics and debris; environmental conservation; social impacts; ocean acidification; general terrestrial influences; co-management strategies; ocean warming; licensing and access rights; oil spills; and economic impacts. Articles relating to global environmental change were consistently among the most cited; marine plastics and ecosystem trophic structure were also focal topics among the highly cited articles. This exploratory research suggests that scientists’ written outputs provide fertile ground for identifying and tracking important and emerging ocean sustainability issues and their possible solutions, as well as the organizations and scientists who work on them.

Trophic relationships and ecosystem functioning of Bakreswar Reservoir, India

Reservoirs are artificial water bodies having social application and hybrid characters of both river and lake. Thorough analysis of water quantity and quality is necessary to ensure the health of these ecosystems, as they are considered one of the major water sources in developing countries. Biological subsystem of reservoirs consists of both autotrophs and heterotrophs in the open zone and littoral zone. These components are critical for freshwater aquatic food webs. Bakreswar reservoir has been selected as the current study site. Static model representing ecosystem trophic structure is developed through Ecopath with Ecosim software and is analysed to obtain idea about the ecosystem functioning and functioning. This reservoir is found to be approaching maturity but with vulnerabilities being present as is evident from the studies of ecosystem attributes, transfer efficiencies, mixed trophic impact, niche overlap and other attributes. Good assemblage of biota like macrophytes, zooplankton etc. is observed, thus presenting some diversity in the food web. Based on the primary production to respiration ratio, this system can be categorized as a moderately mature and healthy ecosystem but is vulnerable to perturbations as is evident by low values of connectance index and system omnivory index. Comparatively low Finn cycling index indicates that this system is approaching maturity but is vulnerable. With a pedigree index of 0.459, the model is well suited for the study site. The knowledge thus obtained for this reservoir can be utilized to form proper management strategies to facilitate successful conservation management and proper resource utilization.

Global microbialization of coral reefs.

Microbialization refers to the observed shift in ecosystem trophic structure towards higher microbial biomass and energy use. On coral reefs, the proximal causes of microbialization are overfishing and eutrophication, both of which facilitate enhanced growth of fleshy algae, conferring a competitive advantage over calcifying corals and coralline algae. The proposed mechanism for this competitive advantage is the DDAM positive feedback loop (dissolved organic carbon (DOC), disease, algae, microorganism), where DOC released by ungrazed fleshy algae supports copiotrophic, potentially pathogenic bacterial communities, ultimately harming corals and maintaining algal competitive dominance. Using an unprecedented data set of >400 samples from 60 coral reef sites, we show that the central DDAM predictions are consistent across three ocean basins. Reef algal cover is positively correlated with lower concentrations of DOC and higher microbial abundances. On turf and fleshy macroalgal-rich reefs, higher relative abundances of copiotrophic microbial taxa were identified. These microbial communities shift their metabolic potential for carbohydrate degradation from the more energy efficient Embden-Meyerhof-Parnas pathway on coral-dominated reefs to the less efficient Entner-Doudoroff and pentose phosphate pathways on algal-dominated reefs. This 'yield-to-power' switch by microorganism directly threatens reefs via increased hypoxia and greater CO2 release from the microbial respiration of DOC.

Near-island biological hotspots in barren ocean basins.

Phytoplankton production drives marine ecosystem trophic-structure and global fisheries yields. Phytoplankton biomass is particularly influential near coral reef islands and atolls that span the oligotrophic tropical oceans. The paradoxical enhancement in phytoplankton near an island-reef ecosystem—Island Mass Effect (IME)—was first documented 60 years ago, yet much remains unknown about the prevalence and drivers of this ecologically important phenomenon. Here we provide the first basin-scale investigation of IME. We show that IME is a near-ubiquitous feature among a majority (91%) of coral reef ecosystems surveyed, creating near-island ‘hotspots' of phytoplankton biomass throughout the upper water column. Variations in IME strength are governed by geomorphic type (atoll vs island), bathymetric slope, reef area and local human impacts (for example, human-derived nutrient input). These ocean oases increase nearshore phytoplankton biomass by up to 86% over oceanic conditions, providing basal energetic resources to higher trophic levels that support subsistence-based human populations.

Hydrological hydrochemical and toxicological regime of fishery basins of Ural part of the Caspian Sea

Hydrologo-hydrochemical regime of the Caspian sea, its biological productivity and trophic structure of ecosystem of basin essentially depends on natural-climatic factors forming liquid and biogen flow at water scoop of the basin.

Balancing complexity and feasibility in Mediterranean coastal food-web models: uncertainty and constraints

Mass-balance trophic models (Ecopath and EcoTroph) are valuable tools that can be used to describe ecosystem structure and functioning, identify target species to be monitored, and allow comparisons of ecosystem states under different management options. Nevertheless, the Ecopath modelling approach is constrained by 2 major sources of uncertainty: model complexity and input data quality. We developed an approach for identifying the optimum model structure that considers trade-offs between feasibility, complexity, and uncertainty, using a Mediterranean coastal ecosystem as a case study. We began with an existing well-documented and good-quality food-web model comprising 41 functional groups at Port-Cros National Park, France. Based on this model, we assessed the effects of different aggregation choices, driven by a simplification of sampling effort, on the Ecopath and EcoTroph model outputs. We identified the functional groups in which imprecise biomass input significantly influenced the food-web model, and measured the relative effects on the ecosystem trophic structure and ecosystem maturity and complexity indices. A simplified model comprising 32 functional groups was identified as the best compromise between model complexity and reliability. High trophic level predators, abundant primary pro- ducers, and groups with a high biomass and/or diversified diet significantly influenced the model structure. We concluded that the collection of local and accurate biomass data, especially for the most influential functional groups we identified, should be a priority when developing food-web models for similar ecosystems. Our method enables simplified and standardized models, while considering both the feasibility and reliability of the Ecopath and EcoTroph applications for Mediterranean coastal ecosystems.

Range Expansion of the Jumbo Squid in the NE Pacific: δ15N Decrypts Multiple Origins, Migration and Habitat Use

Coincident with climate shifts and anthropogenic perturbations, the highly voracious jumbo squid Dosidicus gigas reached unprecedented northern latitudes along the NE Pacific margin post 1997–98. The physical or biological drivers of this expansion, as well as its ecological consequences remain unknown. Here, novel analysis from both bulk tissues and individual amino acids (Phenylalanine; Phe and Glutamic acid; Glu) in both gladii and muscle of D. gigas captured in the Northern California Current System (NCCS) documents for the first time multiple geographic origins and migration. Phe δ15N values, a proxy for habitat baseline δ15N values, confirm at least three different geographic origins that were initially detected by highly variable bulk δ15N values in gladii for squid at small sizes (<30 cm gladii length). In contrast, bulk δ15N values from gladii of large squid (>60 cm) converged, indicating feeding in a common ecosystem. The strong latitudinal gradient in Phe δ15N values from composite muscle samples further confirmed residency at a point in time for large squid in the NCCS. These results contrast with previous ideas, and indicate that small squid are highly migratory, move into the NCCS from two or more distinct geographic origins, and use this ecosystem mainly for feeding. These results represent the first direct information on the origins, immigration and habitat use of this key “invasive” predator in the NCCS, with wide implications for understanding both the mechanisms of periodic D. gigas population range expansions, and effects on ecosystem trophic structure.

Building a Fisheries Trophic Interaction Database for Management and Modeling Research in the Gulf of Mexico Large Marine Ecosystem

Development of ecosystem-based fisheries management models depends, to a large extent, on the availability of trophic interaction data. These models could address ecological questions, examine ecosystem trophic structure, and be used in placement analysis for marine protected areas, among other uses. Many studies on fish trophic interactions have been conducted in the gulf of mexico over the past 120 yrs, and we are currently compiling data from these studies into a database. Here, we report on a collection of 747 references, investigate spatial and taxonomic distributions of the fish species examined, and identify data gaps. Metadata lite, a condensed version of customary metadata that answers the who, what, where, when, and why, has been collected on all studies, all references have been geocoded, and habitat characterizations have been standardized using the coastal and marine ecological classification standard for about 60% of the references. Visualization tools and products to assist in the synthesis, analysis, and interpretation of the data, including maps, network depictions, and dynamic interactions, are discussed. A survey of trophic data available for fisheries management models for managed species in us gulf waters appear to be adequate for at least 23 of 50 of managed species, while data for at least 14 species remain insufficient for model development assessment.

Niche overlap and trophic resource partitioning of two sympatric batoids co-inhabiting an estuarine system in southeast Australia

Elasmobranchs play an important role within the trophic structure of marine ecosystems, but there are relatively few studies published on the feeding ecology of these species. Reported herein is the feeding ecology and trophic resource partitioning of two sympatric batoid species, Urolophus cruciatus and Narcine tasmaniensis from southeast Australia. The diet of males and females of both species was similar, suggesting no sex-specific dietary preferences. Ontogenetic changes in diet were observed from the diets of both species: as the body size increased, the proportion consumed of crustacea to polychaeta decreased. A relatively high degree of niche overlap (70%) was detected between the trophic resources of the two species. The way in which the predators partitioned the resources, however, was significantly different. U. cruciatus fed predominately on small benthic crustaceans (amphipods and decapods), while N. tasmaniensis displayed a preference towards Maldanidae polychaetes. Therefore, although U. cru- ciatus and N. tasmaniensis both feed predominately on benthic invertebrates, they specialise on different taxa. This trophic resource partitioning contributes to the biodiversity of the region by facilitating the coexistence of these sympatric species. The banded stingaree, Urolophus cruciatus and the Tasma- nian numbfish, Narcine tasmaniensis are two sympatric batoids widely distributed around the southeast of mainland Australia from South Australia to New South Wales. Both species are also found in large numbers in the coastal waters of southeast Tasmania, and are regarded as among the most common fish found on soft sediments in the deeper bays of southern Tasmania (Hutchins and Swainston, 1999; Edgar, 2009). They are also commonly caught as by-catch from a range of fisheries throughout their distribution, although incidental mortality rates have not been quantified for either species. Both species share several common traits including: a similar morphology and size as well as co-existing in the same demersal habitat where they remain relatively inactive, lying buried in either sandy or muddy substrate for long periods of time (Edgar, 2009; Last and Stevens, 2009). Given their commonality, we propose that there is a degree of competition for resources between the two species. The objectives of this study were to describe the diet composition of these two species, and assess the level of dietary resource partitioning to determine whether this is a potential mechanism that allows the two species to coexist within the coastal waters of southeast Tasmania.

Producer Nutritional Quality Controls Ecosystem Trophic Structure

Trophic structure, or the distribution of biomass among producers and consumers, determines key ecosystem values, such as the abundance of infectious, harvestable or conservation target species, and the storage and cycling of carbon and nutrients. There has been much debate on what controls ecosystem trophic structure, yet the answer is still elusive. Here we show that the nutritional quality of primary producers controls the trophic structure of ecosystems. By increasing the efficiency of trophic transfer, higher producer nutritional quality results in steeper ecosystem trophic structure, and those changes are more pronounced in terrestrial than in aquatic ecosystems probably due to the more stringent nutritional limitation of terrestrial herbivores. These results explain why ecosystems composed of highly nutritional primary producers feature high consumer productivity, fast energy recycling, and reduced carbon accumulation. Anthropogenic changes in producer nutritional quality, via changes in trophic structure, may alter the values and functions of ecosystems, and those alterations may be more important in terrestrial ecosystems.