Benthic Primary Consumers Research Articles

Variation in fatty acid content among benthic invertebrates in a seasonally driven system

AbstractAt temperate latitudes where seasonal changing environmental conditions strongly affect the magnitude, duration and species composition of pelagic primary production, macrobenthic organisms living below the photic zone rely on the sedimentation of organic matter as their primary energy source. The succession from nutritious spring blooms to summer cyanobacteria is assumed to reduce food quality for benthic primary consumers and their fatty acid (FA) profiles. In contrast, we find low seasonal variability in FA content of five benthic macroinvertebrates spanning two trophic levels in the Baltic Sea, a system with high seasonal variation in phytoplankton species composition. However, levels of the major FA groups vary greatly between benthic species. The results suggest that benthic macroinvertebrates have evolved FA metabolism adapted to degraded sedimenting material. Moreover, our study shows that species composition of benthic macrofauna rather than seasonal changing conditions affect availability of essential nutrients to higher trophic levels.

Utilization of riverine organic matter by macrobenthic communities in a temperate prodelta

Macrobenthos is an important component of organic carbon storage and energy flow in marine systems, including these impacted by riverine discharge and high share of allochthonous organic matter (OM). Changing environmental conditions, such as lower precipitation and snow cover duration, may affect patterns of riverine input, therefore it is crucial to know how benthic communities utilize different OM sources in areas affected by rivers. Using Bayesian stable isotope mixing models, we assessed the diet composition of common macroinvertebrates forming benthic communities in the transition zone of one of the largest river outlets in the Baltic Sea region, the Vistula River prodelta. Furthermore, we analyzed the spatial and temporal variability in the biomass-weighted resource utilization by those communities. Contribution of riverine OM to the particulate OM in Vistula prodelta decreased with increasing depth. Despite similar distances to the river mouth, the relative contribution of riverine OM to the diet of all studied taxa also decreased with increasing depth, which corresponded to organic matter composition in prodelta waters. Nevertheless, due to synchronous structural changes in benthic communities, and changes in the feeding modes of dominant species, particularly Macoma balthica and Hediste diversicolor, the riverine organic carbon share in the biomass of benthic communities often remained the highest in the deepest prodelta parts. Our study corroborates that benthic primary consumers act as a gateway for riverine organic matter into the marine food web and illustrates that sediment properties and resource partitioning affects spatial structure of benthic communities and their abilities to utilize allochthonous OM.

Selenium Distribution and Trophic Transfer in the Periphyton-Benthic Macroinvertebrate Food Chain in Boreal Lakes Downstream from a Milling Operation.

Selenium (Se) is an essential micronutrient with a narrow essentiality-toxicity range known to bioaccumulate in aquatic food webs. Selenium uptake and trophic transfer at the base of aquatic food chains represent a great source of uncertainty for Se risk assessment. The goal of the present study was to investigate Se distribution in water and sediment and its subsequent transfer into the periphyton-benthic macroinvertebrate (BMI) food chain in boreal lakes downstream from a Saskatchewan uranium mill. In particular, the present study aimed to assess potential differences in Se bioaccumulation patterns by BMI taxa to contribute to the current knowledge gap. During summer 2018 and 2019, water, sediment, periphyton, and BMI were sampled at two sites in Vulture Lake, seven sites in McClean Lake east basin, and one reference site in McClean Lake west basin. Periphyton and BMI taxa were sampled with artificial substrates (Hester-Dendy) deployed for 5 weeks in 2018 and 7 weeks in 2019; BMI were sorted into the lowest practical achievable taxonomic level and analyzed for total Se concentrations. At the diluted effluent exposure sites, Se concentrations in BMI ranged from 1.3 to 18.0 µg/g dry weight and from 0.3 to 49.3 µg/g dry weight in 2018 and 2019, respectively, whereas concentrations ranged from 0.01 to 3.5 µg/g dry weight at the reference site. Selenium concentrations in periphyton and some BMI taxa sampled near the effluent diffuser (Se < 1 µg/L) reached levels comparable to higher effluent exposure sites (Se > 2 µg/L). Despite differences in Se bioaccumulation among BMI taxa, an approximately one-to-one trophic transfer ratio was observed for benthic primary consumers and benthic predatory taxa. Environ Toxicol Chem 2022;41:2181-2192. © 2022 SETAC.

Bentho-pelagic mismatches in intertidal sandflats in relation to seasonal upwelling: the role of endobenthic ecosystem engineering

Allochthonous transfers are ubiquitous features of marine ecosystems. While these transfers typically subsidise recipient ecosystems and increase donor control, mismatches in allochthony and biotic recipients can also occur. However, driving processes are not well understood, particularly in the context of biotic determinants in coastal ecosystems. Using a 2 yr dataset, we show that allochthonous inputs related to seasonal offshore upwelling on the west coast of South Africa do not lead to strengthening of bottom-up regulation in intertidal lagoonal sandflat ecosystems. Despite an increase in mean phytoplankton biomass by 46.4% at benthic study sites during summer upwelling seasons, benthic primary producer (microphytobenthos) biomass did not increase proportionally, and neither did consumer (macro- and meiofauna) population metrics. Unexpectedly, levels of these response variables were greater during winter downwelling periods than upwelling phases. Correlation analyses indicated that the bentho-pelagic mismatch documented in relation to upwelling may be related to coincidental increases in densities of endobenthic burrowing sandprawnsKraussillichirus kraussi, which are key ecosystem engineers, principally due to rapid sediment reworking and destabilisation. The predominantly negative correlations recorded between benthic response variables and sandprawn density align with our past experimental work, suggesting that the suppressive effect of sandprawns on benthic primary producers and consumers evident in small-scale experiments also manifests over large temporal scales, thereby overriding potential subsidising effects of upwelling. Our findings indicate that in sandflat ecosystems, endobenthic ecosystem engineers that are rapid benthic destabilisers may be important in determining responses to marine allochthonous inputs and the degree of donor control in recipient ecosystems.

The ultimate peanut butter on crackers for Hyalella: diatoms on macrophytes rather than bacteria and fungi on conditioned terrestrial leaf litter

Abstract It is well established that terrestrial and aquatic ecosystems are interlinked in a myriad of ways, yet understanding of the role terrestrial particulate organic matter (OM) plays in supporting aquatic macroinvertebrate production is still incomplete and debated. We investigated the role of terrestrial particulate OM (leaf litter) and autochthonous OM (macrophytes) with and without biofilm as food sources for the model benthic macroinvertebrate Hyalella (Amphipoda). We hypothesised that biofilm (algae, fungi, bacteria) associated with terrestrial and aquatic plants is the main food source for benthic primary consumers. First, we microbially conditioned the leaf litter insitu for 10‐weeks. Then, we performed a laboratory feeding experiment with nine treatments: no food, conditioned leaf litter from two native terrestrial plants, non‐conditioned leaf litter from these plants, two freshly collected macrophyte species with periphyton, and these macrophytes without periphyton. We measured the growth and analysed the fatty acid (FA) composition of field‐collected and experimental amphipods reared on these diets. We found that amphipods fed food sources without biofilm grew poorly and had a FA content and composition resembling that of starved animals. The same was observed for amphipods fed one leaf litter type with biofilm. However, animals fed the other leaf litter type with biofilm grew during the feeding experiment and showed a characteristic FA composition linked to the higher fungal biomass in this food source. We showed that amphipods fed macrophytes with biofilm resembled field‐collected animals regarding FA amounts and composition; monounsaturated FA representing &gt;40% of total FA, with 16:1n‐7 (palmitoleic acid) and 18:1n‐9 (oleic acid) being the most abundant, and polyunsaturated FA representing 30% of total FA. The FA data indicated algae, particularly diatoms, as evidenced by large quantities of its biomarker 16:1n‐7, were the main food for the amphipods. We conclude diatoms were the peanut butter on crackers for the amphipods, and diatom consumption supported its somatic growth and polyunsaturated FA composition. In contrast, bacteria and fungi on conditioned leaf litter were lower quality food sources because they do not provide essential FA for macroinvertebrates growth and physiology. These results have important ecological implications from a food web perspective.

Coastal upwelling affects filter-feeder stable isotope composition across three continents

Large-scale nutrient fertilisation by coastal upwelling promotes benthic productivity through energy subsidies from enhanced phytoplankton production, and predictions of alterations to upwelling under climate change have implications for benthic ecosystem functioning. We investigated the stable isotope compositions of two bioengineers of global significance, the mussels Perna perna and Mytilus galloprovincialis, from upwelling and non-upwelling sites in five upwelling systems. Samples from Brazil, South Africa and Oman exhibited lower δ13C values at upwelling sites than at non-upwelling sites, with clearer effects where upwelling is more intense and frequent. North West Africa showed variability, probably linked to Saharan dust input. We highlight the importance of upwelling to sustaining benthic primary consumers and the sensitivity of consumer diet to the intensity and frequency of upwelling within each region. These results have implications in relation to climate change scenario effects on upwelling events, with potential cascading effects on higher trophic levels and ecosystem functioning.

Relationships between depth and δ15N of Arctic benthos vary among regions and trophic functional groups

Stable isotope ratios of nitrogen (δ15N) of benthic primary consumers are often significantly related to water depth. This relationship is commonly attributed to preferential uptake of 14N from sinking particulate organic matter (POM) by microbes, and suggests that relationships between δ15N and water depth may be affected by local POM sources and flux dynamics. We examined the relationships between δ15N and water depth (20–500 m) for six trophic functional groups using a mixed effects modelling approach, and compared relationships between two contiguous Arctic marine ecosystems with different POM sources and sinking export dynamics: the Canadian Beaufort Sea and Amundsen Gulf. We demonstrate for the first time in the Arctic that δ15N values of mobile epifaunal carnivores increased as a function of depth when considered separately from benthopelagic and infaunal carnivores, which contrarily did not exhibit increasing δ15N with depth. The δ15N of suspension/filter feeders, infaunal deposit feeders and bulk sediment also increased with water depth, and the slopes of the relationships were steeper in the Amundsen Gulf than in the Beaufort Sea. We propose that regional differences in slopes reflect differences in POM sources exported to the benthos. In the Beaufort Sea, terrestrial POM discharged from the Mackenzie River quantitatively dominates the sedimentary organic matter across the continental shelf and slope, dampening change in δ15N of benthic POM with depth. In the Amundsen Gulf, we attribute a faster rate of change in δ15N of POM with increasing depth to larger contributions of marine-derived POM to the benthic sedimentary pool, which had likely undergone extensive biological transformation in the productive offshore pelagic zone. Differences in POM input regimes among regions should be considered when comparing food webs using stable isotopes, as such differences may impact the rate at which consumer δ15N changes with depth.

Positive feedback between chironomids and algae creates net mutualism between benthic primary consumers and producers.

The chironomids of Lake Mývatn show extreme population fluctuations that affect most aspects of the lake ecosystem. During periods of high chironomid densities, chironomid larvae comprise over 90% of aquatic secondary production. Here, we show that chironomid larvae substantially stimulate benthic gross primary production (GPP) and net primary production (NPP), despite consuming benthic algae. Benthic GPP in experimental mesocosms with 140,000 larvae/m2 was 71% higher than in mesocosms with no larvae. Similarly, chlorophyll a concentrations in mesocosms increased significantly over the range of larval densities. Furthermore, larvae showed increased growth rates at higher densities, possibly due to greater benthic algal availability in these treatments. We investigated the hypothesis that larvae promote benthic algal growth by alleviating nutrient limitation, and found that (1)larvae have the potential to cycle the entire yearly external loadings of nitrogen and phosphorus during the growing season, and (2) chlorophyll a concentrations were significantly greater in close proximity to larvae (on larval tubes). The positive feedback between chironomid larvae and benthic algae generated a net mutualism between the primary consumer and primary producer trophic levels in the benthic ecosystem. Thus, our results give an example in which unexpected positive feedbacks can lead to both high primary and high secondary production.

Phenotypic differentiation of the Red Sea gastropods in response to the environmental deterioration: Geometric morphometric approach

The negative impacts of degradation in the coastal zone of the Red Sea are becoming well known in upper portions of the trophic web (e.g., humans and fish), but are less well known among the benthic primary consumers. In addition, the degree to which heavy metals are entering the trophic web can be better-quantified using macrobenthos. Two-gastropod genera encompassing Echinolittorina subnodosa and Planaxis sulcatus from three different localities on the Egyptian coast of the Red Sea were examined in order to deduce the impact of environmental deterioration on the morphology of shells. The examined sites include clean pristine, slightly polluted, and markedly polluted rocky shores. Phosphate/lead industry is the main source of pollution in this zone. Because landmarks on the rugose Echinolittorina are difficult to define and to ensure finer resolution of the analyses, a newly ‘grid-based’ landmarks was implemented. Both Canonical Variate Analysis (CVA) and Thin Plate Spline (TPS) were particularly capable to capture and terrace the minor morphological variations accurately. Two phenotypes portioned among the environmentally different populations were recognized and interpreted as ecotypes with many intermediate forms. The first ecotype has a higher spire and smaller aperture and dominating the pristine site North of Marsa Alam, whereas the second ecotype has a globular shell shape with big aperture and dominating the markedly polluted site. The intermediate forms dominating the slightly polluted site. The shape differences are interpreted as an adaptive differentiation to different metal concentrations. As the morphological variation between the two-ecotypes of both taxa is still minors, and both ecotypes occur together with many intermediate forms, the phenotypic divergence stage has not yet accomplished. The gradational shape change among the investigated populations was positively correlated with index of Pollution (IP). As the human activities were the main driver of the phenotypic changes, hence anthropogenic impact may shift the evolution and/or the extinction rates.

Roles of epiphytes associated with macroalgae in benthic food web of a eutrophic coastal lagoon

Macroalgae perform a significant function in the trophic dynamics in many coastal lagoons, and conventionally, they are the key trophic base that fuels the overall aquatic food web. However, few studies have considered the trophic contribution of epiphytes that attach to macroalgae in the diet of benthic primary consumers or their contribution to the trophic base of the aquatic food web. In this study, macrobenthic invertebrate biomass was combined with multiple-isotope-mixing models to distinguish the trophic importance of macroalgae and their associated epiphytic assemblages in the benthic food web during Ulva lactuca bloom in the Yundang Lagoon, a eutrophic coastal lagoon in Xiamen, China. Amphipods primarily dominated the zoobenthos, with the biomass varied from 40.9g/m2 in January to 283.9g/m2 in March. They mainly fed on U. lactuca and its associated epiphytes, which jointly contributed more than 60% to amphipod diets, but species-specific feeding habits were exhibited among amphipods. Using the zoobenthos biomass as a weighting factor, the contribution of U. lactuca and its epiphytes to total benthic communities during U. lactuca bloom exceeded 65%.The epiphytes were clearly utilized more than U. lactuca, with a median contribution ranging from 48.5% in January to 66.6% in March. Our findings demonstrate the trophic importance of the epiphytes in macroalgae-based coastal habitats, as found in many seagrass beds. Therefore, we propose that further food web studies of macroalgae-based ecosystems should pay greater attention to the role of epiphytes.

Modelling the effect of Cerastoderma edule bioturbation on microphytobenthos resuspension towards the planktonic food web of estuarine ecosystem

Microphytobenthos (MPB) represents an important food source for primary consumers in estuarine ecosystems and the availability of MPB as food items results from complex physical, chemical, and biological interactions. In Baie des Veys (Lower Normandy, France), the common cockle Cerastoderma edule constitutes the major bioturbator in the ecosystem in terms of biomass. In this ecosystem, cockle bioturbation is a key process regulating the MPB erosion flux in the water column. This bivalve intensely modifies the top layer of the sediment by increasing the sediment erodibility and the fluxes of suspended chlorophyll a through the valve movements. More precisely, cockle bioturbation destabilizes the sediment surface by creating a biogenic layer that is easily eroded with tidal hydrodynamic forces. Associated MPB can then be exported to the water column to fuel higher trophic levels of the planktonic food web. The aim of this study was to develop a numerical model that reproduces the export of MPB associated to the biogenic layer erosion. Kinetics of suspended MPB, in response to increasing stress, were obtained from flume experiments in lab controlled conditions and in situ natural conditions. Following this, the suspended MPB were analyzed to respectively parameterize the model by (1) a calibration approach, and (2) an independent validation. The analysis has highlighted that the higher the biomass of cockles, the higher the MPB resuspension rates. Our model consistently reproduces the tendency encountered in laboratory analysis and with in situ natural conditions. During the validation, a small site-specific lack of adjustment was identified, but, among the macrozoobenthic community, the model can be significantly improved by considering the bioturbation activities of another ecosystem engineer, Pygospio elegans. This study thus provides reliable estimates of the daily food availability from benthic primary consumers in an estuarine system where cockles dominate the bioturbating assemblage. This model can be inserted in various model designs (0D, 1D-vertical or 3D).

Benthic faunal assimilation pathways and depth-related changes in food-web structure across the Canadian Arctic

Climate changes in the Arctic are expected to decrease the currently tight pelagic–benthic coupling, yet large-scale, regional understanding of the origin of food for benthic organisms across both biological productivity and depth gradients is still missing. The organic matter assimilation pathways of benthic organisms, along with food-web structure, were investigated at shelf and slope locations spanning 2000km across the Canadian Arctic using stable carbon and nitrogen isotope analysis. Three potential food sources and over 75 benthic taxa belonging to four feeding guilds were analyzed, but the δ13C end-members for the benthic food-webs could not be clearly discerned. While spatial patterns of δ13C for pelagic particulate organic matter were linked to phytoplankton biomass at the time of sampling, sediment δ13C values reflected the relative composition of terrestrial and marine organic matter. On average, benthic primary consumers were enriched in 13C by 5 and 7‰ compared to the potential organic matter sources sampled in sediment and the water column, respectively. The δ13C discrepancy between identified sources of organic matter and benthic organisms suggests that an uncharacterized food source provided a significant carbon source to these animals. We propose that the 13C enrichment of benthic organisms may be largely caused by the assimilation of ice algae (which were not sampled in this study), particularly in regions of known high ice-algal standing stock such as Barrow Strait and Eclipse Sound. The δ15N values of bottom-water particulate organic matter and of benthic primary consumers increased with depth due to greater degradation of the settling organic material. The δ15N values of secondary consumers did not increase with depth, leading to a decrease of their trophic position compared with shallower regions and likely reflecting an increase in omnivory due to scarcity of prey at depth. This study emphasizes the potential importance of sea-ice algae as a carbon source for benthic communities in the Canadian Arctic and suggests that distinct food-web structures prevail over the shelf and slope.

Impact of forest harvesting on trophic structure of eastern Canadian Boreal Shield lakes: insights from stable isotope analyses.

Perturbations on ecosystems can have profound immediate effects and can, accordingly, greatly alter the natural community. Land-use such as forestry activities in the Canadian Boreal region have increased in the last decades, raising concerns about their potential impact on aquatic ecosystems. The objective of this study was to evaluate the impact of forest harvesting on trophic structure in eastern Canadian Boreal Shield lakes. We measured carbon and nitrogen stable isotopes values for aquatic primary producers, terrestrial detritus, benthic macroinvertebrates, zooplankton and brook trout (Salvelinus fontinalis) over a three-year period in eight eastern Boreal Shield lakes. Four lakes were studied before, one and two years after forest harvesting (perturbed lakes) and compared with four undisturbed reference lakes (unperturbed lakes) sampled at the same time. Stable isotope mixing models showed leaf-litter to be the main food source for benthic primary consumers in both perturbed and unperturbed lakes, suggesting no logging impact on allochthonous subsidies to the littoral food web. Brook trout derived their food mainly from benthic predatory macroinvertebrates in unperturbed lakes. However, in perturbed lakes one year after harvesting, zooplankton appeared to be the main contributor to brook trout diet. This change in brook trout diet was mitigated two years after harvesting. Size-related diet shift were also observed for brook trout, indicating a diet shift related to size. Our study suggests that carbon from terrestrial habitat may be a significant contribution to the food web of oligotrophic Canadian Boreal Shield lakes. Forest harvesting did not have an impact on the diet of benthic primary consumers. On the other hand, brook trout diet composition was affected by logging with greater zooplankton contribution in perturbed lakes, possibly induced by darker-colored environment in these lakes one year after logging.

Trophic resource use by macrozoobenthic primary consumers within a semi-enclosed coastal ecosystem: Stable isotope and fatty acid assessment

The diet of different macrozoobenthic trophic groups was investigated in the Arcachon Bay—a semi-enclosed macrotidal ecosystem that shelters the largest Zostera noltei seagrass meadow in Europe—in early spring and late summer 2009, using stable isotopes and fatty acids. Fatty acid profiles and literature information about the biology and physiology of benthic consumers were combined to identify the main organic matter sources for the benthic primary consumers. An isotope mixing model was then run to evaluate the contribution of each organic matter source to each identified trophic group (suspension feeders, sub-surface deposit feeders, micro-and macrograzers, suspension-oriented interface feeders and deposit-oriented interface feeders). Variations in organism' diets with respect to both habitats (intertidal seagrass meadows, intertidal bare sediments and subtidal bare sediments) and study periods were also investigated. At the scale of this study, it appeared that the diet of macrozoobenthos primary consumers was based exclusively on autochthonous material (no use of terrestrial organic matter): mainly microphytobenthos, seagrasses and their epiphytes, and phytoplankton. In addition, the different trophic groups relied on different organic matter pools: for instance, suspension feeders mainly fed on microphytobenthos and phytoplankton, whereas subsurface deposit feeders fed on microphytobenthos, decayed seagrasses and bacteria, and grazers mainly fed on microphytobenthos, and seagrasses and their epiphytes. The same pattern was observed in both early spring and late summer, indicating a stability of the benthic system at a six-month time scale. Finally our results showed that, in Arcachon Bay, the seagrass meadow directly or indirectly (through detritus) plays a significant role in the diet of most benthic consumers.

Phytoplankton Abundance Constrains Planktonic Energy Subsidy to Benthic Food Web

Linkages across habitats between habitats are fundamental components of ecological processes. As a major characteristic of within-lake food webs, linkage of benthic and planktonic food webs has received a great deal of attention in recent aquatic studies. However, planktonic energy subsidy to benthic consumers has been infrequently tested in experiment. In a field experiment manipulating nutrients and phytoplankton abundance, we ask how changes in phytoplankton abundance affect planktonic energy subsidy to benthic primary consumers across nutrient levels. Our results suggest that the planktonic subsidy to benthic primary consumers depends on the phytoplankton abundance. Furthermore, highly taxon-specific planktonic energy subsidy to benthic primary consumers suggests that the benthic community composition partially determines the degree of the planktonic-benthic linkage. Because shallow and eutrophic lakes distribute worldwide, and many ecological functions are mediated by planktonic-benthic linkage, it will be important to consider these findings to protection and restoration of lake ecosystems.

An investigation of enhanced mercury bioaccumulation in fish from offshore feeding

We investigated the dietary pathways of mercury transfer in the food web of Morency Lake (Canada) to determine the influence of carbon source and habitat use on mercury bioaccumulation in fish. Whole-body concentrations of methylmercury (MeHg) were significantly different in four fish species (white sucker, brown bullhead, pumpkinseed and smallmouth bass) and increased with both trophic position and greater feeding on offshore (versus littoral) carbon. An examination of fish gut contents and the depth distribution of invertebrates in Morency Lake showed that smallmouth bass and brown bullhead were supplementing their littoral diet with the consumption of either opossum shrimp (Mysis diluviana) or profundal amphipods in offshore waters. The zooplanktivore Mysis had significantly higher MeHg concentrations than zooplankton and benthic invertebrates, and it was an elevated source of MeHg to smallmouth bass. In contrast, profundal amphipods consumed by brown bullhead did not have higher MeHg concentrations than littoral amphipods. Instead, partitioning of benthic invertebrate resources likely explains the greater MeHg bioaccumulation in brown bullhead, associated with offshore feeding of amphipods. White sucker and brown bullhead had a similar trophic position but white sucker consumed more chironomids, which had one-third the MeHg concentration of amphipods. Our findings suggest that offshore feeding in a lake can affect fish MeHg bioaccumulation via two different processes: (1) the consumption of MeHg-enriched pelagic prey, or (2) resource partitioning of benthic primary consumers with different MeHg concentrations. These observations on the mechanisms of habitat-specific bioaccumulation highlight the complexity of MeHg transfer through lake food webs.

Determination of food sources for benthic invertebrates and brook trout Salvelinus fontinalis in Canadian Boreal Shield lakes using stable isotope analysis

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 17:107-117 (2012) - DOI: https://doi.org/10.3354/ab00465 Determination of food sources for benthic invertebrates and brook trout Salvelinus fontinalis in Canadian Boreal Shield lakes using stable isotope analysis Patricia Glaz1,*, Pascal Sirois2, Christian Nozais1 1Département de biologie et centre d’études nordiques, Université du Québec à Rimouski, Rimouski, Québec G5L 3A1, Canada 2Laboratoire des sciences aquatiques, Département des sciences fondamentales, Université du Québec à Chicoutimi, Chicoutimi, Québec G7H 2B1, Canada *Email: patricia.glaz@uqar.ca ABSTRACT: Allochthonous inputs can be an important contribution of organic matter in lake ecosystems. Yet, our understanding of the patterns of energy dependence of littoral invertebrates and fish is poor. We measured carbon (δ13C) and nitrogen (δ15N) stable isotope values for primary producers, terrestrial detritus, benthic macroinvertebrates, zooplankton and brook trout Salvelinus fontinalis in 8 oligotrophic Canadian Boreal Shield lakes to determine food sources that support benthic consumers and brook trout. Mixing models used to determine animal diets from stable isotope analysis showed leaf litter to be the principal food source for benthic primary consumers in 6 out of 8 lakes. Brook trout derived its carbon mainly from benthic predatory macroinvertebrates in all lakes, with a contribution ranging from 60 to 90%. Zooplankton also contributed to brook trout diet in 3 of 8 lakes, ranging from 28 to 37%. δ15N increased from primary producers to consumers at different trophic positions in all lakes. Nitrogen isotopic signatures of brook trout became more positive with increasing fish length, indicating a change in fish foraging strategy related to size. Our study (1) suggests that carbon from terrestrial habitat (leaf litter) may contribute significantly to the food web of oligotrophic Canadian Boreal Shield lakes and (2) highlights the importance of carbon originating from benthic habitats in supporting brook trout in these lakes. KEY WORDS: Allochthonous subsidies · Benthic macroinvertebrates · Zooplankton · Brook trout · Diet breadth · Size-related diet shift · Stable isotopes · Boreal lakes Full text in pdf format PreviousNextCite this article as: Glaz P, Sirois P, Nozais C (2012) Determination of food sources for benthic invertebrates and brook trout Salvelinus fontinalis in Canadian Boreal Shield lakes using stable isotope analysis. Aquat Biol 17:107-117. https://doi.org/10.3354/ab00465 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 17, No. 2. Online publication date: November 06, 2012 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2012 Inter-Research.

Secondary production of Chironomidae in a large eutrophic lake: implications for lake sturgeon production

Abstract. Most foodweb research in lentic systems has focused on pelagic primary (phytoplankton) and secondary (zooplankton) production as the primary energy sources for higher trophic-level production. Recent research has demonstrated that secondary production of benthic primary consumers can affect pelagic fish production and foodweb structure in lakes. We used the instantaneous growth method to calculate secondary production of chironomids in Lake Winnebago, Wisconsin (USA), where previous research has shown that lake sturgeon (Acipenser fulvescens) rely heavily on the benthos (chironomids) as a food source. We also used literature-derived data and the instantaneous growth method to calculate annual production of lake sturgeon to test whether chironomid production is sufficient to support the current lake sturgeon population in Lake Winnebago. We collected benthic samples with an Ekman grab at 4 profundal sites during ice-free conditions on 11 dates from spring 2008 through spring 2009. We measured in...

Influence of piers on functional groups of benthic primary producers and consumers in the channel of a subtropical coastal lagoon

Artificial habitats have become common in coastal areas worldwide and may influence the structure and functioning of benthic ecosystems. We analyze the influence of piers on the benthic morphofunctional groups of rocky seaweeds and of soft bottom macrofauna in the channel of Conceição Lagoon (southern Brazil). The main impact is a reduction in the luminosity available for photosynthetic activity which is directly related to a decrease in the biomasses of sediment microphytobenthos and of more highly structured macroalgae life-forms. Contrary to expectations, the morphotypes of potentially high biomass productivity, such as articulated coralline, corticated and leathery macroalgae, were in general less abundant and the low biomass foliose and filamentous macroalgae occurred in reference areas but not under the piers. The piers' effects on motile epifauna and infauna functional groups were site-specific and probably related to the general reduction in primary producer organisms in the new habitats. The discretely motile infauna was the only functional group able to thrive under the piers due to their reduced motility and fragile morphological structures, being benefited by the shelter provided by the artificial habitats. Our results showed that the piers might have a negative effect on the base-trophic level organisms responsible for bottom-up controls.

Trophic transfer of brevetoxins to the benthic macrofaunal community during a bloom of the harmful dinoflagellate Karenia brevis in Sarasota Bay, Florida

Harmful algal blooms can cause mass mortalities of top predators such as fish, marine mammals and seabirds but the food web transfer from toxic phytoplankton to these organisms has not been fully elucidated. Macrobenthic invertebrates in coastal waters, including bivalve suspension- and deposit-feeders, carnivorous gastropods, deposit-feeding amphipods and polychaetes, are a major food source for a wide variety of predators and can thus play a critical role in the trophic transfer of algal toxins to higher trophic levels. The objective of this study was to investigate toxin accumulation in transplanted juvenile hard clams, Mercenaria mercenaria, a species naturally occurring in the region, and in various macrobenthic functional groups from Florida coastal waters during a natural bloom of the dinoflagellate, Karenia brevis, a producer of brevetoxins. Bloom concentrations in the water column ranged from 100 to 1200cellsml−1 over the course of the experiment. This study revealed that these lipophilic toxins can be rapidly accumulated by both suspension- and deposit-feeding benthos, especially bivalve molluscs [1.9–2.8μg PbTx-3 eq (g wet weight)−1]. Transplanted M. mercenaria rapidly accumulated toxins from the water column attaining ∼0.5μg PbTx-3 eq (g wet tissue)−1 after only 4h-exposure to the K. brevis bloom and a maximum value of 1.5±0.2μg PbTx-3 eq (g wet tissue)−1 after 72h. Relatively high brevetoxin concentrations were also measured in co-occurring benthic carnivorous gastropods [1–2.6μg PbTx-3 eq (g wet weight, WW)−1]. Mean toxin concentrations in polychaetes and crustaceans varied in the range ∼0.04–0.2μg PbTx-3 eq (g WW)−1 over the study period, and thus were typically lower than in molluscs. This study demonstrated in situ toxin accumulation by benthic primary and secondary consumers during a natural Florida red tide. Accumulation by primary consumers may be highly variable in space and time (as shown in bivalves from the natural benthic community) and among taxonomic groups. Toxin transfer further up the food web will thus depend on the toxin level accumulated in prey, the number of pathways from which the predator may accumulate toxins and on possible biological magnification of lipophilic toxins. Overall, this study revealed qualitatively and quantitatively that benthic consumers of a number of taxa can serve as vectors for transporting brevetoxins within the food web.