Profundal Invertebrate Research Articles

Phenotypic and resource use partitioning amongst sympatric, lacustrine brown trout, Salmo trutta

Divergence into discrete foraging specialist morphs living in sympatry is relatively well described in lacustrine fishes of the Salmonidae. Although piscivorous forms of Salmo trutta have been widely reported, other trophic foraging specialists are strangely rarely recorded amongst Salmo species. Microsatellite and mitochondrial genetic data segregated S. trutta collected from Loch Laidon, Scotland, into four distinct genetic groups. Three groups analysed in this study showed significant differences in body shape, stomach contents, muscle stable isotope signature, gill raker length and spacing, and habitat use. We conclude that the three genetically defined groups comprise: a generalist foraging morph, a pelagic feeding specialist morph and a profundal macrobenthos feeding morph. The features distinguishing these morphs, however, show a degree of overlap. This appears to be only the second record of invertebrate resource use partitioning associated with expression of alternative morphologies in sympatry this species and the first report of a profundal invertebrate feeding morph. Why such polymorphisms are generally rare in Salmo species remains unclear, but potential explanations are discussed.

An extended Benthic Quality Index for assessment of lake profundal macroinvertebrates: addition of indicator taxa by multivariate ordination and weighted averaging

The chironomid Benthic Quality Index (BQI) is a widely used metric in assessments of lake status. The BQI is based on 7 indicator taxa, which like most profundal fauna, often occur sporadically in low densities. Hence, a major weakness of the index is that it cannot be calculated when indicator taxa are not captured. Thus, an extension of the BQI that incorporates more macroinvertebrate taxa is desirable. We used 2 statistical approaches (Detrended Correspondence Analysis and Weighted Averaging) to estimate new benthic quality indicator scores for profundal macroinvertebrate taxa and to construct modified BQIs called Profundal Invertebrate Community Metrics (PICMs). We calibrated the PICMs and evaluated their bioassessment performance with macroinvertebrate and environmental data from 735 lake basins in Finland. Both PICMs included 70 taxa and could be calculated for a substantially greater proportion (99.5%) of sites than the original BQI (83.5%). Compared to the BQI, the PICMs were more strongly correlated with whole-community variation and were more predictable from environmental factors independent of human activities in undisturbed reference lakes. PICMs were more specific in identifying undisturbed lakes and more sensitive in discriminating nonreference from reference lakes. The strength of relationships to total P concentration was equal among indices. These results suggest that the extension of BQI to incorporate more taxa will increase generality, accuracy, and representativeness of lake profundal macroinvertebrate assessment.

Nearshore energy subsidies support Lake Michigan fishes and invertebrates following major changes in food web structure.

Aquatic food webs that incorporate multiple energy channels (e.g., nearshore benthic and pelagic) with varying productivity and turnover rates convey stability to biological communities by providing independent energy sources. Within the Lake Michigan food web, invasive dreissenid mussels have caused rapid changes to food web structure and potentially altered the channels through which consumers acquire energy. We used stable C and N isotopes to determine how Lake Michigan food web structure has changed in the past decade, coincident with the expansion of dreissenid mussels, decreased pelagic phytoplankton production, and increased nearshore benthic algal production. Fish and invertebrate samples collected from sites around Lake Michigan were analyzed to determine taxa-specific 13C:12C (delta13C) and 15N:14N (delta15N) ratios. Sampling took place during two distinct periods, 2002-2003 and 2010-2012, that spanned the period of dreissenid expansion, and included nearshore, pelagic and profundal fish and invertebrate taxa. The magnitude and direction of the delta13C shift indicated significantly greater reliance upon nearshore benthic energy sources among nearly all fish taxa as well as profundal invertebrates following dreissenid expansion. Although the mechanisms underlying this delta13C shift likely varied among species, possible causes include the transport of benthic algal production to offshore waters and increased feeding on nearshore prey items by pelagic and profundal species. delta15N shifts were more variable and of smaller magnitude across taxa, although declines in delta15N among some pelagic fishes suggest a shift to alternative prey resources. Lake Michigan fishes and invertebrates appear to have responded to dreissenid-induced changes in nutrient and energy pathways by switching from pelagic to alternative nearshore energy subsidies. Although large shifts in energy allocation (i.e., pelagic to nearshore benthic) resulting from invasive species appear to affect total production at upper trophic levels, changes in trophic structure and utilization of novel energy pathways may help to stabilize food webs following species invasions.

Effects of Sedimentation on the Profundal Benthic Macroinvertebrates of a Great Plains Reservoir

Reservoir sedimentation has become a large and pervasive problem throughout the entire United States. Sedimentation gradually destroys and eliminates the services for which reservoirs were constructed (flood protection, water storage, and recreation), yet sedimentation is also an ecological problem. Organisms that depend on the deep parts of lakes cannot survive if their habitats are being buried by sediments. Perry Lake, in northeastern Kansas, has lost 23% of its original volume. Sediment thicknesses (depth of sediment accrued since lake formation) in the main lake range from 2–140cm, and upper portions of the lake have become unnavigable. To measure the effect of sedimentation the diversity and density of profundal invertebrate macrofauna were sampled. Thirteen taxa were collected and assemblages were dominated by oligochaetes, midges (chironomidae), and the Phantom Midge Chaoborus. No significant associations between sediment thickness and invertebrate metrics were found, however sediment size was cor...

Effects of Dispersal-Related Factors on Species Distribution Model Accuracy for Boreal Lake Ecosystems

Species distribution modeling is used in applied ecology; for example in predicting the consequences of global change. However, questions still remain about the robustness of model predictions. Here we estimate effects of landscape spatial configuration and organism flight ability—factors related to dispersal—on the accuracy of species distribution models. Distribution models were developed for 129 phytoplankton taxa, 164 littoral invertebrate taxa and 44 profundal invertebrate taxa sampled in 105 Swedish lakes, using six different modeling techniques (generalized linear models (GLM), multivariate adaptive regression splines (MARS), classification tree analysis (CTA), mixture discriminant analysis (MDA), generalized boosting models (GBM) and random forests (RF)). Model accuracy was not affected by dispersal ability (i.e., invertebrate flight ability), but the accuracy of phytoplankton assemblage predictions and, to a lesser extent, littoral invertebrate assemblages were related to ecosystem size and connectivity. Although no general pattern across species or spatial configuration was evident from our study, we recommend that dispersal and spatial configuration of ecosystems should be considered when developing species distribution models.

The importance of spatial variation of benthic invertebrates for the ecological assessment of European lakes

Lake assessment systems based on benthic macroinvertebrates critically depend on the amount of spatial variation of organisms within and between lakes. Investigators need to distinguish between community changes that are related to human pressures and those that are caused by inherent natural variability. However, littoral and profundal invertebrate communities are constrained by different drivers of change and may respond unevenly to distinct human disturbances. How human disturbances determined by different pressures interact in modifying the distribution of benthic invertebrate species at multiple spatial scales needs to be assessed and efficiently quantified, in order to set up reliable assessment tools of ecological status. Driven by the research activity carried out within the European project Wiser (Water bodies in Europe: Integrative Systems to assess Ecological status and Recovery, funded by the European Union under the 7th Framework Programme), we collated several case studies with the aim to increase our understanding of basic sources of spatial variation of invertebrate assemblages. The set of papers includes a variety of different European lakes, habitat types and human pressures from the Nordic, Central, Atlantic, Alpine and Mediterranean regions. All papers have an obvious applied objective and suggest which factors need to be considered when designing invertebrate-based classification tools.

Evaluation of approaches for measuring taxonomic completeness of lake profundal macroinvertebrate assemblages

Summary 1. Benthic macroinvertebrates (MI) are commonly used to assess freshwater ecosystems with the reference condition approach. Such assessments necessitate control for natural community variation, either by categorical typologies or by predictive models that have been widely and successfully developed for running water biota but not previously for lake profundal invertebrates. 2. We evaluated four modelling techniques [multivariate regression tree (MRT), limiting environmental differences, nonparametric multiplicative regression (NPMR) and River Invertebrate Prediction And Classification System (RIVPACS) and the operative Finnish lake typology for assessing taxonomic completeness (observed-to-expected number of taxa, O/E) of profundal MI assemblages. We used data from 74 and 33 minimally disturbed reference lake basins for calibration and validation of the approaches, respectively, and 72 test basins subject to various anthropogenic pressures to evaluate sensitivity to detect impact. Either all predicted taxa (threshold probability of capture Pt = 0+) or only those predicted to be captured with ≥0.25 probability were used to calculate O/E. 3. With Pt = 0.25, all four modelling approaches were accurate (mean O/E = 0.966–1.053) but imprecise (SD of O/E = 0.279–0.304) in predicting the fauna actually observed in validation sites. All models were subtly more precise than a null model (mean 1.038, SD 0.343) or the typology (1.046, 0.327). The taxon-specific NPMR model was slightly more precise than the other three models based on site groupings. 4. The O/E values correlated relatively weakly (r = 0.55–0.86) among the approaches, which thus produced contrasting lake-specific assessments, despite their seemingly comparable performances. Indeed, typology, suggesting that MI assemblages were impaired in 56% of test sites, was more sensitive than the other approaches (26–46%) as an indicator of human-induced deterioration. However, this greater ostensible sensitivity seemed to be biased, as lake morphometry, a main driver of natural community variation, remained uncontrolled by the typology. 5. Generally, our exercise illustrates the inconclusiveness of the common validation criteria for the assessment methods. The apparent poor predictability of the profundal fauna, irrespective of the method, may partly stem from large observation error, which could be alleviated by more intensive sampling. However, instead of an O/E-taxa index, some other metric encompassing quantitative aspects might be preferable for assessing these species-poor communities.

Assimilation of freshwater salmonid aquaculture waste by native aquatic biotaThis paper is part of the series “Forty Years of Aquatic Research at the Experimental Lakes Area”.

An experimental finfish aquaculture farm was operated in a small lake at the Experimental Lakes Area in northwestern Ontario, Canada. In this study, we used the distinct and enriched carbon and nitrogen isotope ratios (δ13C and δ15N) of rainbow trout ( Oncorhynchus mykiss ) feed and waste to determine whether the operation provided a novel source of energy for native biota. For 1 year prior to and for 3 years during the cage culture, we collected littoral, pelagic, and profundal invertebrates and minnows from the experimental and reference lakes. In both the second and third years of aquaculture, there was a significant increase in δ15N of all organisms sampled in the experimental lake; mean δ15N values of littoral, pelagic, and profundal invertebrates and minnows shifted towards the signature of the fish feed by up to 4.2‰. Significant increases in δ13C of up to 2.6‰ were observed in Mysis , profundal chironomids, and minnows but not in littoral invertebrates or zooplankton. Aquaculture waste became a progressively more important component of minnow diets over the course of this study. The dissolved and (or) particulate wastes of the cage operation became a novel source of energy for the native biota in this experimental lake.

Natural variation of profundal macroinvertebrate communities in boreal lakes is related to lake morphometry: implications for bioassessment

Modern biological assessment of aquatic systems is often based on the reference condition approach, which requires characterization of biota in undisturbed conditions. For this approach, it is essential to recognize the origins and degree of natural variation in communities. We used data from 55 minimally disturbed Finnish lake basins to investigate the natural variation of profundal macroinvertebrate community composition in relation to environmental factors. Partial canonical correspondence analysis showed that most (68% combined, 39% uniquely) of the total explained compositional variation (29%) was correlated with environmental variables insensitive to human activities, especially lake morphometry. In contrast, the unique contributions of geographical location and variables influenced by human activities (dissolved oxygen and total phosphorus) were substantially smaller (5.5% and 22%, respectively). All of the explained variation (38%–64%) of three widely used community metrics was also correlated with human-insensitive environmental factors. The results suggest that variation in undisturbed profundal invertebrate communities of reference sites is strongly dependent on variables insensitive to human activities and especially on those related to lake morphometry, suggesting that reference communities for bioassessment of impacted lakes should be rather predictable from these variables.

Tracking recovery trends of boreal lakes: use of multiple indicators and habitats

Recovery rates of different metrics (physiological, biological), trophic levels (phytoplankton, invertebrate consumers), and habitats (pelagic, benthic) were studied over a 16-y period in 10 boreal lakes recovering from acidification. Several of the metrics showed significant, positive trends over time that supported our expectations of biological recovery. Taxonomic diversity of phytoplankton assemblages, but not assemblage composition, showed early signs of recovery that were strongly related to increases in pH in both reference and acidified lakes. Results from benthic invertebrate assemblages were, however, equivocal. Littoral invertebrate taxon richness and diversity increased in both acidified and reference lakes, whereas sublittoral and profundal invertebrate assemblages of both lake groups showed clear negative trends. These findings indicate that sublittoral and profundal assemblages might be influenced by factors other than lake acidity, such as coincident changes in habitat quality (e.g., ambient O2 and temperature). Our findings show that the selections of the group of organisms to monitor recovery and the habitat in which to monitor recovery must be considered carefully when designing and implementing programs to assess degradation and recovery.

Eulittoral macroinvertebrate communities of lowland lakes: discrimination among trophic states

Summary1. Nutrient inputs from urban and agricultural land use often result in shifts in species composition of pelagic and profundal invertebrate communities. Here, we test if nutrient enrichment affects the composition of eulittoral macroinvertebrate communities, and, if so, if macroinvertebrate communities of five different habitat types reflect differences in trophic state.2. Macroinvertebrate community composition of 36 lakes was significantly correlated with total phosphorus (TP) concentration, the proportion of coarse woody debris (CWD) and root habitats and the proportion of grassland.3. However, macroinvertebrate communities of five major habitat types from eight lakes were more dissimilar among habitats than among trophic states. Community composition of reed and stone habitats was significantly correlated with wind exposure but not TP concentration, while macroinvertebrate composition of sand habitats was related to TP concentration and coarse sediments. In CWD and root habitats, both TP concentration and a predominance of invasive species covaried, which made it difficult to relate the observed compositional differences to either trophic state or to the effects of competition between native and invasive species.4. Trophic state influenced the composition of eulittoral macroinvertebrate communities but to a lesser extent than has been previously reported for profundal habitats. Moreover, the effects of trophic state were nested within habitat type and were partially superseded by biotic interactions and small‐scaled habitat complexity. Although eulittoral macroinvertebrate communities were not strong indicators of the trophic state of lowland lakes, they may be used to assess other anthropogenic impacts on lakeshores.

Lake trophic status and bioaccumulation of polychlorinated biphenyls in benthic organisms: a comparison between littoral and profundal invertebrates

We investigated the influence of lake trophic status on accumulation of polychlorinated biphenyls (PCBs) in littoral and profundal invertebrates from 19 lakes in southern Sweden. The PCB concentration in profundal chironomids (Chironomus sp.) was negatively correlated with lake trophy but the concentration in littoral crayfish (Pacifasticus leniusculus) was unrelated to shifting nutrient regimes. PCB concentrations in chironomids were negatively correlated, while crayfish did not correlate with lake total phosphorus. Two findings indicate that different processes determine bioaccumulation in littoral and profundal invertebrates: (i) a lack of correlation between PCB concentrations in crayfish and chironomids within lakes and (ii) some differences in congener distribution in the two species. We suggest a possible explanation in that chironomids are directly exposed to settling material from the pelagic zone, while crayfish are omnivorous and feed mainly in the littoral zone. A intensive investigation on one pond population could not reveal any individual factors, such as lipid content, size, or sex, influencing bioaccumulation of PCBs in crayfish.

Fatty acids in profundal benthic invertebrates and their major food resources in Lake Erken, Sweden: seasonal variation and trophic indications

Fatty acid (FA) concentrations and their seasonal variations were quantified for profundal benthic invertebrates, surficial sediment, and sedimenting matter from Lake Erken, Sweden. Food quality for profundal zoobenthos, as indicated by the concentrations of long-chain polyunsaturated FA, ω3 FA, or eicosapentaenoic acid (EPA) in sediment and sedimenting matter, was highest in spring and autumn and markedly lower in summer. Surficial sediment was consistently lower in all FA than was sedimenting matter. Palmitoleic acid (16:1ω7) was the dominating FA in both sedimenting matter and sediment. In fauna samples, EPA, palmitic acid (16:0), palmitoleic acid, and vaccenic acid (18:1ω7) were among the dominant FA. Docosahexaenoic acid was found only in the predators Chaoborus and Procladius. Differences between functional feeding guilds were found for the diatom-indicating FA palmitoleic acid and the bacteria-specific FA isoseptadecanoic acid (17:0iso). Furthermore, principal components analysis showed marked differences in FA composition among taxa. These differences reflect the relative contribution of food from autotrophic (phytoplankton production) and heterotrophic sources (detrital food web) in profundal invertebrate taxa.

On the use of split moving window analysis for boundary detection in ordered dataseries from benthic communities

The capacity of Split Moving Window (SMW) boundary analysis was tested to detect the depth of the transition of a littoral to a profundal invertebrate community in two datasets that were ordered along a depth gradient. The littoral community was dominated byPolypedilum nubeculosum agg.,Potamopyrgus jenkinsi andGlyptotendipes cf.pallens. The species richness of the profundal community was much lower. Its fauna was dominated byChironomus cf.plumosus andChaoborus flavicans. The transition could be detected with small window sizes. The discontinuities are located at the same depth as the oxygen stratification. We conclude that SMW can be used to study artificial transects. Noisy datasets should be transformed to reduce the variation. The scale dependence of SMW is an advantage. Information about the nature of a discontinuity (transition, trend or local discontinuity) can be obtained by increasing the window size. The location of discontinuities that are detected at the edge of a series, with large windows, should be interpreted carefully due to the existence of a blind zone.