While environmental reconstruction has been a staple in the study of past societies, underused tools from ecology, such as food webs, can enable a more thorough understanding of the human place within ecosystems. Drawing on two recent studies, this article describes the types of questions that can be addressed using this approach. The authors demonstrate how food webs that include archaeological data can provide insights into the effects of extinctions, invasion and ecosystem change on communities, and can address key questions of the structure and dynamics of past societies. This article highlights examples of best practice for the compilation of archaeo-ecological networks, and suggest ways of developing a synthetic understanding of past environments.

In Antarctica, amphipods form a highly diverse group, occupy many different ecological niches and hold an important place in food webs. Here, we aimed to test whether differences in Antarctic amphipod feeding habits were reflected in their mandible morphology, and if mouthpart specialization could be used to describe amphipod trophic ecology. To do so, we compared mandible morphology in nine species spanning seven families and five functional groups (grazers, suspension feeders, generalist predators, specialist predators and scavengers). Mandible morphology adequately depicted some aspects of amphipod trophic ecology, such as the trophic level at which animals feed or their degree of dietary specialization. On the other hand, links between mandible morphology and amphipod diet were seldom unambiguous or straightforward. Similar adaptations were found in distinct functional groups. Conversely, mandible morphology could vary within a single functional group, and phylogenetic effects sometimes complicated the interpretation of form-function relationships. Overall, mandible morphology on its own was generally not sufficient to precisely predict amphipod feeding strategies. However, when combined with other methods (e.g. gut contents, trophic markers), it constitutes a valuable source of information for integrative studies of amphipod ecological diversity in the Southern Ocean.

Parasites can have strong effects on invertebrate host behaviour, fecundity and survival in marine ecosystems. However, parasites are often poorly documented and still rarely integrated into marine ecological modelling; comprehensive surveys of infection in marine invertebrates are sporadic at best. For example, rock crabs are an important part of Californian coastal ecosystems, both as regulators of mussel populations and non-native species, and as prey items for predators like sea otters, but their parasite communities and potential effects on crab population dynamics are seldom studied or understood. Here, we present the first report of infection by the trematode Helicometrina nimia in the economically and ecologically important red rock crab (Cancer productus) and Pacific rock crab (Romaleon antennarium). As intermediate hosts, they are a missing link for infection by H. nimia in Californian fish that was unreported until now. Based on these findings, we advocate for further research into parasite diversity and their potential effects on ecologically and commercially important species.

Carbon and nitrogen stable isotopes were used to describe an estuarine mangrove food web in New Caledonia, SW Pacific. Isotopic values were measured for all components of the ecosystem, from various organic matter (OM) sources to predators. Primary producers showed δ13C values from −32.29‰ (Bruguiera gymnorhiza) to −24.67‰ (mouth particulate organic matter), whereas δ15N values ranged from 1.48‰ (Avicennia marina) to 10.17‰ (Eichomia crassipes). Two potential organic matter sources, i.e. the mangrove species and E. crassipes, appeared not to be directly used by consumers although were indirectly entering the food web through particulate and sedimentary organic matter pools (POM and SOM). Overall, invertebrates showed C-depleted and N-depleted values compared with fish, highlighting their lower trophic level. The highest trophic levels in this estuarine mangrove were represented by carangids (δ15N of 11.24‰ for Caranx sp. and 10.81‰ for Carangoides fulvoguttatus) and gerrids (δ15N of 10.42‰ for Gerres filamentosus). Two main pathways of organic matter were identified from sources of OM to end-members, i.e. from estuarine POM and SOM toward gerrids and from marine POM towards carangids. The food chain comprised three or four trophic levels, depending on the pathway of organic matter. The position of some consumer species within the reconstructed food web might imply that an important source of organic matter was probably missing, i.e. microphytobenthos. Despite an obvious connection, the role of river inputs as potential drivers of mangrove food web dynamics appeared important only during the wet season.

New information on the biology and ecology of an abundant ‘rockcod’ species, Lepidonotothen squamifrons (family: Nototheniidae), found at South Georgia is presented. Data collected from twenty demersal trawl surveys carried out at South Georgia and Shag Rocks (sub-Antarctic) from 1986–2012 were analysed to investigate distribution, size, maturity and diet. Distribution was patchy with large aggregations in consistent high-density ‘hotspots’ to the east of Shag Rocks and to the west of South Georgia. Fish density was shown to vary between regions of the shelf and between years but there was little evidence of significant changes in catch per unit effort (CPUE) over the duration of the study. Length at first maturity for males and females (37–38 cm, total length) was very similar to that described for the Indian Ocean population. Detailed stomach contents analysis (2005–12) indicated a varied diet dominated by salps/tunicates, but with ontogenetic and depth variations in prey composition. Lepidonotothen squamifrons was shown to be an opportunistic bentho-pelagic forager. Enhanced knowledge of the ecology of L. squamifrons will be valuable in future research on food web modelling and marine spatial management in the Southern Ocean and to provide baseline data on the ecology of the species in a rapidly changing environment.

The planktonic microbial communities of three meltwater ponds, located on the McMurdo Ice Shelf, were investigated from the end of January 2008 to early April, during which almost the entire pond volumes froze. The ponds were comprised of an upper mixed layer overlying a salt-stabilized density gradient in which planktonic communities were primarily embedded. Plankton comprised all components of the “microbial loop”, though carnivorous protists were rare. As the ponds froze and light became increasingly limited, it was expected conditions would induce physiological changes altering the functional role of autotrophic and heterotrophic microplankton within the ponds. The results showed that microbial groups responded to the onset of winter by declining in abundance, though an exception was the appearance of filamentous cyanobacteria in the water column in March. As freezing progressed, autotrophs declined more rapidly than heterotrophs and grazing rates and abundances of mixotrophic and heterotrophic organisms increased. Grazing pressure on bacteria and picophytoplankton also increased, in part explaining their decline over time. The results indicate that stressors imposed during freezing select for increasing heterotrophy within the remaining microbial communities, although all components of the food web eventually decline as the final freeze approaches.

Regulators are acutely aware of the need for meaningful risk assessments to supportdecisions on the safety of GM crops to non-target invertebrates in determining theirsuitability for field release. We describe a process for developing appropriate, testablerisk hypotheses for invertebrates in agroecosystems that might be exposed to plantsdeveloped by GM and future novel technologies. An existing model (PRONTI) generates aranked list of invertebrate species for biosafety testing by accessing a database ofbiological, ecological and food web information about species which occur in croppingenvironments and their potential interactions with a particular stressor (EcoInvertebase). Our objective in this contribution is to explore and further utilise theseresources to assist in the process of problem formulation by identifying potentiallysignificant effects of the stressor on the invertebrate community and the ecosystemservices they provide. We propose that for high ranking species, a conceptual food webusing information in Eco Invertebase is constructed, and using an accepted regulatory riskanalysis framework, the likelihood of risk, and magnitude of impact for each link in thefood web is evaluated. Using as filters only those risks evaluated as likely to extremelylikely, and the magnitude of an effect being considered as moderate to massive, the mostsignificant potential effects can be identified. A stepwise approach is suggested todevelop a sequence of appropriate tests. The GM ryegrass plant used as the “stressor” inthis study has been modified to increase triacylglyceride levels in foliage by 100% toincrease the metabolisable energy content of forage for grazing animals. The high-ranking“test” species chosen to illustrate the concept are New Zealand native speciesWiseana cervinata (Walker) (Lepidoptera: Hepialidae),Persectania aversa (Walker) (Lepidoptera: Noctuidae), and theself-introduced grey field slug, Deroceras reticulatum (Müller).

We analyzed stable isotopes of carbon and nitrogen to investigate the trophic structureof the subtidal food web around the Mingan Islands, northern Gulf of St. Lawrence, easternCanada. All benthic consumers were enriched in 13C (mean δ13C of–17.1‰) compared to particulate organic matter (POM: –23.3‰). Nitrogen stable isotoperatios ranged from 6‰ to 14‰ and the organisms studied fell into three distinct trophicgroups, primary producers, primary consumers (herbivores), and predators. The sea starCrossaster papposus and the sculpin Myoxocephalusscorpius, known to be top level predators, had slightly higher δ15Nthan other predators. Although the average isotope signature of the sea starSolaster endeca placed it among regular predators, the δ15Nincreased with sea star size and large individuals could be considered as top predators.The relatively small number of organisms located at intermediate trophic levels suggests alow level of omnivory in the Mingan Islands’ system, which contrasts with previouslydescribed benthic systems that exhibit a continuum between herbivores and predators. Lowomnivory, in addition to low diversity, suggests that this ecosystem may be relativelyunstable if exposed to natural and/or anthropogenic disturbances such as exploitation andclimate change.

In aquatic food webs zooplankton constitutes an important link between primary producers and higher trophic levels. Copepods often dominate the zooplankton in coastal oceans and are the prey of the majority of planktivorous fish. Feeding behaviour, as well as the food quantity and quality are recognized factors that affect copepod growth, and therefore, the energy transfer efficiency throughout food webs. The natural occurrence and magnitude of these growth factors and their combined effects on marine copepods, as keystone grazers in the pelagic marine realm, are poorly understood. Here, we assessed how these different factors vary throughout the year, and then examine their relative influence upon copepods maximal growth rates. A multiple regression model, including all variables previously selected, and the inclusion of the sea temperature allowed us to estimate the pure influence of the studied factors, and the environmental effect on copepod growth rates. The results imply that ingestion of diatoms may induce a positive effect on specific growth rates of copepods, and the quality of this food item (high PUFA and HUFA availability) might explain such effect. Therefore, seasonal variability in diatom abundance, possibly driven by changes in the oceanographic regime, should be considered a critical factor controlling copepod growth in productive coastal ecosystems.

The trophic ecology of Konaino Creek, a small mountain headwater stream draining rainforest in the aseasonal tropics on Bougainville Island, Papua New Guinea, was examined and a food web was constructed. The major source of energy in Konaiano Creek was allochthonous detritus, most of which had been terrestrially degraded to fine particulate organic matter rather than entering the stream as leaf litter. This fine detritus was collected by the filter-feeders (mostly Simuliidae and also Hydropsychidae) which formed the dominant functional feeding group (64.4% of the fauna). Thus filterers processed most of the allochthonous detritus and made the energy available to other trophic levels, rather than shredders (1.7% of the fauna) which perform this role in temperate headwater streams. Collector-gatherers made up 22.7% of the fauna, carnivorses, mostly Odonata, Decapoda (crabs) and Hydrobiosidae, comprised 2.8% of the fauna and grazer-scrapers made up 7.4%. The latter were inhibited by low instream production owing to heavy shading and the instability and abrasion of the substrate due to frequent spates. In comparison, the trophic ecology of the nearby, coastal, Bovo River (with a catchment mainly in rainforest but mostly cleared with introduced species at the study site) was quite different and it was dominated by collector-gatherers (74%) and grazer-scrapers (15%).

The area planted to genetically engineered crops has increased dramatically in the last ten years. This has generated many studies examining non-target effects of bioengineered plants expressing Bacillus thuringiensis endotoxins. To date, most have focused on population-level effects in the field or laboratory evaluation of specific plant-herbivore or plant-herbivore-predator trophic pathways. Using a post-mortem enzyme-linked immunosorbent assay, we examined the uptake of Cry1Ab-endotoxins by predatory coccinellids and the importance of anthesis to this trophic pathway. Adult Coleomegilla maculata, Harmonia axyridis, Cycloneda munda and Coccinella septempunctata contained low, but detectable, quantities of Bt-endotoxin when screened by ELISA. This was most evident in C. maculata, with 12.8% of 775 individuals testing positive for Cry1Ab-endotoxins. Interestingly, the presence of endotoxins in gut samples was not confined to periods around anthesis, but coccinellid adults tested positive two weeks before and up to ten weeks after pollen was shed, suggesting tri-trophic linkages in their food chain facilitates the transfer of endotoxins into higher-order predators. This contrasts with adult Coleomegilla maculata entering overwintering sites where Bt-endotoxins were not detected in gut samples, indicating low levels of persistence of Cry1Ab-endotoxins within coccinellid predators. This study enhances our understanding of complex interactions between transgenic crops and non-target food webs, but further research is required to quantify the significance of specific trophic linkages in the field.

Helminth parasites of fish in marine systems are often considered to be generalists, lacking host specificity for both intermediate and definitive hosts. In addition, many parasites in marine waters possess life cycles consisting of long-lived larval stages residing in intermediate and paratenic hosts. These properties are believed to be adaptations to the long food chains and the low densities of organisms distributed over broad spatial scales that are characteristic of open marine systems. Moreover, such properties are predicted to lead to the homogenization of parasite communities among fish species. Yet, these communities can be relatively distinct among marine fishes. For benthos, the heterogeneous horizontal distribution of invertebrates and fish with respect to sediment quality and water depth contributes to the formation of distinct parasite communities. Similarly, for the pelagic realm, vertical partitioning of animals with depth will lead to the segregation of parasites among fish hosts. Within each habitat, resource partitioning in terms of dietary preferences of fish further contributes to the establishment of distinct parasite assemblages. Parasite distributions are predicted to be superimposed on distributional patterns of free-living animals that participate as hosts in parasite life cycles. The purpose of this review is first, to summarize distribution patterns of invertebrates and fish in the marine environment and relate these patterns to helminth transmission. Second, patterns of transmission in marine systems are interpreted in the context of food web structure. Consideration of the structure and dynamics of food webs permits predictions about the distribution and abundance of parasites. Lastly, parasites that influence food web structure by regulating the abundance of dominant host species are briefly considered in addition to the effects of pollution and exploitation on food webs and parasite transmission.

There is mounting evidence that parasites can influence the composition and structure of natural animal communities. In spite of this, it is difficult to assess just how important parasitism is for community structure because very few studies have been designed specifically to address the role of parasites at the community level, no doubt because it is difficult to manipulate the abundance of parasites in field experiments. Here, we bring together a large amount of published information on parasitism in intertidal communities to highlight the potential influence of parasites on the structure and biodiversity of these communities. We first review the impact of metazoan parasites on the survival, reproduction, growth and behaviour of intertidal invertebrates, from both rocky shores and soft-sediment flats. Published evidence suggests that the impact of parasites on individuals is often severe, though their effects at the population level are dependent on prevalence and intensity of infection. We then put this information together in a discussion of the impact of parasitism at the community level. We emphasize two ways in which parasites can modify the structure of intertidal communities. First, the direct impact of parasites on the abundance of key host species can decrease the importance of these hosts in competition or predator-prey interactions with other species. Second, the indirect effects of parasites on the behaviour of their hosts, e.g. burrowing ability or spatial distribution within the intertidal zone, can cause changes to various features of the habitat for other intertidal species, leading to their greater settlement success or to their local disappearance. Our synthesis allows specific predictions to be made regarding the potential impact of parasites in certain intertidal systems, and suggests that parasites must be included in future community studies and food web models of intertidal ecosystems.

An important principle of environmental science is that changes in single components of systems are likely to have consequences elsewhere in the same systems. In the sea, food web data are one of the few foundations for predicting such indirect effects, whether of fishery exploitation or following recovery in marine protected areas (MPAs). We review the available literature on one type of indirect interaction in benthic marine ecosystems, namely trophic cascades, which involve three or more trophic levels connected by predation. Because many indirect effects have been revealed through fishery exploitation, in some cases we include humans as trophic levels. Our purpose is to establish how widespread cascades might be, and infer how likely they are to affect the properties of communities following the implementation of MPAs or intensive resource exploitation. We review 39 documented cascades (eight of which include humans as a trophic level) from 21 locations around the world; all but two of the cascades are from shallow systems underlain by hard substrata (kelp forests, rocky subtidal, coral reefs and rocky intertidal). We argue that these systems are well represented because they are accessible and also amenable to the type of work that is necessary. Nineteen examples come from the central-eastern and north-eastern Pacific, while no well-substantiated benthic cascades have been reported from the NE, CE or SW Atlantic, the Southern Oceans, E Indian Ocean or NW Pacific. The absence of examples from those zones is probably due to lack of study. Sea urchins are very prominent in the subtidal examples, and gastropods, especially limpets, in the intertidal examples; we suggest that this may reflect their predation by fewer specialist predators than is the case with fishes, but also their conspicuousness to investigators. The variation in ecological resolution amongst studies, and in intensity of study amongst systems and regions, indicates that more cascades will likely be identified in due course. Broadening the concept of cascades to include pathogenic interactions would immediately increase the number of examples. The existing evidence is that cascade effects are to be expected when hard-substratum systems are subject to artisanal resource exploitation, but that the particular problems of macroalgal overgrowth on Caribbean reefs and the expansion of coralline barrens in the Mediterranean rocky-sublittoral will not be readily reversed in MPAs, probably because factors other than predation-based cascades have contributed to them in the first place. More cascade effects are likely to be found in the soft-substratum systems that are crucial to so many large-scale fisheries, when opportunities such as those of MPAs and fishing gradients become available for study of such systems, and the search is widened to less conspicuous focal organisms such as polychaetes and crustaceans.