Invertebrate Assemblages Research Articles

Changes in the composition of subfossil algae and invertebrate assemblages along the depth gradient in dimictic Lake Valdayskoye (Novgorod Area, Russia)

Changes in the composition of subfossil algae and invertebrate assemblages along the depth gradient in dimictic Lake Valdayskoye (Novgorod Area, Russia)

Space and spatially structured environmental variables account for variation in blackfly and mayfly communities in sub-tropical South African rivers

Using aquatic invertebrate assemblages for bioassessment of streams and rivers is a fast and cost-effective approach to studying the impact of environmental stressors in aquatic ecosystems. The use of aquatic invertebrates is premised on their predictable responses to environmental stressors. Assemblage structure is not, however, only influenced by environment, but also neutral processes and temporal variation. This study quantified the relative roles of the environment (niche processes), space (neutral processes) and temporal factors in structuring mayfly and blackfly assemblages at family and species levels. Asymmetric eigenvector maps in conjunction with canonical redundancy analysis and variation partitioning were used to explore the relative roles of these three factors in structuring macroinvertebrate assemblages. At a species level, flow and water temperature were more important in explaining assemblage structure than at the family level. At the family level, space was more important than temporal and environmental factors. Unexplained variation at species and family level was more than 50%. This suggests (i) caution in using family-level rapid assessments to infer the role of the environment in structuring aquatic macroinvertebrate assemblages, as neutral processes are also dominant; and (ii) that the importance of stochastic processes, such as dispersal, should not be underestimated in rapid assessments.

Beyond hinges and spires: A critical examination of archaeomalacological quantification methodologies using coral reef molluscan assemblages from Jiigurru (Lizard Island Group), northern Great Barrier Reef

Quantification, as one of the pillars of the zooarchaeological subdiscipline, is an invaluable component of the toolkit researchers use to study past people-animal interactions. Despite being the subject of rigorous (zoo)archaeological debate, the calculation of Minimum Number of Individuals (MNI) values remains one of the main methods of quantifying the relative abundance of taxa within faunal assemblages. Choosing the appropriate quantification protocol to calculate the MNI of archaeological invertebrate assemblages can be challenging due to regional taxonomic considerations and the myriad of quantification methodologies and frameworks available in the global archaeomalacological literature. In an Australian context, methodologies for quantifying coral reef molluscan assemblages have not been explicitly evaluated. Using archaeological molluscan assemblages from two midden sites (Freshwater Bay Midden and Mangrove Beach Headland Midden) on the northern Great Barrier Reef island group of Jiigurru (the Lizard Island Group), we critically examine two commonly adopted archaeomalacological quantification methodologies: the NRE MNI and tMNI protocols. The NRE MNI methodology uses one to two non-repetitive elements (NREs) of molluscs, whilst the tMNI protocol includes a wider range of elements akin to vertebrate MNI quantification methodologies. Through a comparison of taxa abundances and statistical analyses, results show that the tMNI protocol, with some modification, is best suited for the Jiigurru assemblages. Higher MNI values and an increased assemblage diversity, evenness, and richness were recorded for the molluscan assemblages at both midden sites when the tMNI protocol was applied. This study foregrounds the importance of data transparency when reporting quantification protocols and outcomes to ensure the highest degree of data quality, replicability, and usability.

Landscape forest cover and local vegetation structure mediate multitrophic relationships but not the leaf damage in cacao trees

Cacao is the most important agricultural product in the southern region of Bahia state, Brazil, with 70 % of its production occurring under the traditional agroforestry where cacao is mostly shaded by native trees. This traditional system allows to reconcile the production with the maintenance of the portion of original biodiversity. However, increased deforestation and intensified agroforestry management aimed at boosting productivity may impact the diversity of native species and the services they provide. In this context, our aim was to disentangle the role of landscape forest cover and the local vegetation complexity on predation of caterpillars and herbivory of cacao plants located in agroforestry systems. The study was conducted across 18 cacao agroforest sites in southern Bahia located in landscapes with different amounts of forest cover. We assessed predation rate using dummy caterpillars, sampling understory birds and arthropods and collected leaves of cacao trees to analyze damage by herbivory. We also measured shading levels and the abundance of cacao trees in each agroforestry. Predation pressure on dummy caterpillars was positively influenced by the abundance of total predators and the level of landscape forest cover and negatively by the number of cacao trees. Even so, we found no evidence that landscape, local features or the actual invertebrate assemblages (predators or herbivores) influenced the cacao leaf damage. The findings highlight the multifaceted interactions between ecological factors, predation pressure, and leaf damage within cacao agroforestry systems.

Spatial and Ontogenetic Patterns in the Trophic Ecology of Two Predatory Fishes in a Large River

ABSTRACTFishes use a variety of physical and biological resources that shift ontogenetically, seasonally and spatially. Quantifying what resources such as prey are required for persistence can improve understanding of ecological needs of fishes and riverine macrosystem functioning. Bowfin (Amia ocellicauda) and largemouth bass (Micropterus nigricans) cohabitate in their native range and potentially compete with one another. Yet, there have been no direct comparisons of their diets across spatial gradients to assess whether they partition resources or shift in prey use. We used multiple univariate and multivariate analyses to compare diet composition, diet overlap, feeding strategy, prey importance and diet partitioning between largemouth bass and bowfin across three reaches of the Upper Mississippi River. Largemouth bass ontogenetically shifted their diet from aquatic invertebrates to fishes and a more diverse assemblage of aquatic invertebrates. Bowfin and adult largemouth bass were top predators which consumed mostly crayfish and fish and overlapped in their diets. Despite overlapping diets, predators partitioned resources by consuming different lengths and abundances of prey, and largemouth bass had greater trophic plasticity. Within a predator group, few differences in diets existed spatially, underscoring the relative homogeneity in resource use potentially from similarities in the river's physical structure. Combined, prey use likely differed sufficiently to reduce potential competition between largemouth bass and bowfin, allowing long‐term coexistence in this system. Our results also highlighted the importance of crayfishes to riverine food webs and underscored the use of multiple prey and habitat types that sustain these predators.

Holocene ecosystem and temperature development inferred from invertebrate remains in Zminje Jezero (Dinaric Alps, Montenegro)

AbstractLake Zminje Jezero (1535 m a.s.l.) in Montenegro was studied for chironomid and other aquatic invertebrate remains in a sediment sequence dating back to 12,000 calibrated 14C years before present (cal yr BP), providing, to our knowledge, the first lake-sediment record studied for chironomids and other associated chitinous aquatic invertebrate remains in the Dinaric Alps. Changes in chironomid and other invertebrate remains along the record make it possible to constrain changes of relevant environmental variables for aquatic invertebrates in the lake including temperature, oxygen availability, trophic status and water depth. The results suggest moderate changes in trophic conditions with chironomid assemblages indicating meso- to eutrophic conditions during the analysed interval. Invertebrate assemblages were typical for lakes with relatively high oxygen availability with a minor trend during the middle to late Holocene to conditions observed in lakes that are more hypoxic. A change in temperature is suggested in the earlier part of the record when the share of chironomid taxa adapted to warmer conditions increased, at the Younger Dryas to Holocene transition, whereas later no particularly pronounced shifts in temperature-sensitive taxa were observed. July air temperatures were estimated based on chironomid assemblages using a transfer function based on calibration data consisting of 117 lakes sampled in the Swiss Alps and northern Switzerland. The results suggest that temperatures rapidly increased by 5 °C at the onset of the Holocene (11,500 cal yr BP) leading to a relatively warm early to mid-Holocene and thereafter slightly decreased during the late Holocene. Reconstructed temperatures are discussed together with a previously published pollen record for our study site and are broadly consistent with other chironomid-based temperature reconstructions from Central, Eastern and Southern Europe. From ca. 3000 cal yr BP sedimentation rates increased and from ca. 500 cal yr BP onwards pollen data suggest that the vegetation and lake catchment were affected by human activities, possibly influencing chironomid and other invertebrate assemblages in the lake and thereby also reconstructed temperatures. Overall, our results show that combining analyses of chironomid and other invertebrate assemblages can provide valuable insights into long-term environmental changes and can provide temperature reconstructions for small mountain lakes in the Balkans, such as Zminje Jezero.

Assessing Methods to Monitor Aquatic Invertebrates in a Large River: Comparing Rock Baskets and Hess Samplers in the Snake River, Wyoming, USA

Large rivers are difficult to sample due to their size yet critical to monitor because humans heavily rely upon and alter them. Aquatic invertebrates are commonly used to assess the ecosystem quality of streams, but methods to sample large rivers are underdeveloped. We sampled aquatic invertebrates using a Hess sampler and rock baskets in the Snake River near Jackson, Wyoming, USA. Hess samples collected more aquatic invertebrate taxa and a higher proportion of Ephemeroptera, Plecoptera, and burrowing taxa. Rock baskets collected a higher proportion of Trichoptera, filterers, and clinging taxa. Bioassessment metrics differed between sampling methods; richness, diversity, evenness, Ephemeroptera, Plecoptera, and Trichoptera (EPT), and Hilsenhoff’s biotic index produced higher values in Hess samples, and percent EPT was higher in rock baskets. Non-metric multidimensional scaling and analysis of similarity indicated that the samplers collected different assemblages (p < 0.001). The standard error of total invertebrate density was smaller and most taxa were collected with seven replicate samples. Understanding how sampling methods alter the aquatic invertebrates collected will help managers develop monitoring protocols that are best suited to the river and collect the most unbiased invertebrate assemblages.

Spatial and temporal variability of fouling communities on oyster spat collectors at Inhaca Island Southern Mozambique: Exploring the influence on recruitment of the oysters Pinctada capensis and Saccostrea cucullata

In the transition from pelagic larva to benthic adult, larvae likely encounter a diverse assemblage of resident invertebrates in their habitat, which may also compete for space during post-settlement periods. Fouling fauna in rocky and seagrass habitats on Inhaca Island, southern Mozambique, was evaluated over 4 months in each of two seasons on oyster collectors fixed at 2 cm above the bottom. As expected, two species of oysters recruited to tiles: the rock oyster Saccostrea cucullata in rocky habitats and the pearl oyster, Pinctada capensis in seagrass habitats. The composition and density of other fouling fauna varied among habitats, location, seasons and surfaces and depending on the duration of the deployment. In seagrass habitats, oysters and barnacles were generally less abundant, allowing other taxa to have higher relative abundance, while higher density of individuals was recorded in rocky habitat. Barnacles dominate among fouling fauna on collectors in both habitats. Despite evidence consistent with negative interactions between oysters and barnacles, the effects of other fouling fauna on oyster abundance appear modest up to 4 months after tiles are placed. Overall, the results help improve our general understanding of the environmental processes that affect the colonisation of intertidal invertebrates, particularly in the southwestern Indian Ocean.

Macroinvertebrate response to run‐of‐river hydropower tailrace inflow: Spatial assessment of community and traits

AbstractRun‐of‐river (R‐O‐R) hydropower dams introduce two discontinuities in the river: the dam and the tailrace. Discontinuities can lead to changes in the water quality that may affect the survival of aquatic macroinvertebrates, depending on their traits. We investigated the invertebrate assemblage and community‐level traits in an urban river influenced by a small hydropower tailrace in Hokkaido, Japan. As a result of the tailrace inflow to the main channel, the bypassed reach was warmer, and the areas below the confluence were colder. Temperature was a consistent factor affecting the distribution of indicator taxa and of the five major taxa that contributed the most to dissimilarity, but other environmental factors also showed significant effects. At the community level, the weighted mean of taxa with warm preference showed a significant positive relationship with temperature, but taxa with cold preference did not appear to be filtered by the cold water delivered by the tailrace. However, sensitive taxa such as Ephemerella have already started showing negative responses to temperature. The observed distribution of cold‐preferring scrapers could negatively affect the energy transfer from primary producers to higher consumers in the bypassed reach. Appropriate mitigation of climate change effects in hydropower systems can be achieved by increasing the flow in the bypassed reach, especially during the summer months, to maintain a temperature regime that is adequate for the survival of macroinvertebrate populations and maintenance of ecosystem functions.

Changes in the composition of invertebrate assemblages from wave-exposed intertidal mussel stands along the Nova Scotia coast, Canada.

Rocky intertidal habitats occur worldwide and are mainly characterized by primary space holders such as seaweeds and sessile invertebrates. Some of these organisms are foundation species, as they can form structurally complex stands that host many small invertebrates. The abundance of primary space holders is known to vary along coastlines driven directly or indirectly by environmental variation. However, it is less clear if the invertebrate assemblages associated to a foundation species may remain relatively unchanged along coastlines, as similar stands of a foundation species can generate similar microclimates. We examined this question using abundance data for invertebrate species found in mussel stands of a similar structure in wave-exposed rocky habitats at mid-intertidal elevations along the Atlantic coast of Nova Scotia (Canada). While the most abundant invertebrate species were found at three locations spanning 315 km of coastline, species composition (a combined measure of species identity and their relative abundance) differed significantly among the locations. One of the species explaining the highest amount of variation among locations (a barnacle) exhibited potential signs of bottom-up regulation involving pelagic food supply, suggesting benthic-pelagic coupling. The abundance of the species that explained the highest amount of variation (an oligochaete) was positively related to the abundance of their predators (mites), further suggesting bottom-up forcing in these communities. Overall, we conclude that species assemblages associated to structurally similar stands of a foundation species can show clear changes in species composition at a regional scale.

Successions of terrestrial invertebrate communities during the Tsey Glacier retreat, Central Caucasus

In the Caucasus, the total area taken up by glaciers is known to have reduced by 23% over the last 20 years. This natural experiment allows for additive and replacement models of autogenic succession of biocoenoses within paraglacial landscapes to be tested. A certain risk of the extinction of cryophilic species also exists. However, montane paraglacial successions of invertebrate assemblages have hitherto been studied neither in the Caucasus nor in Russia as a whole. Structural changes of taxocoenoses were traced in a spatial and temporal sequence of ten properly dated paraglacial sites in the Tsey Gorge, North Ossetia − Alania (1–170-years old) among the testate amoebae, earthworms, molluscs, myriapods, mites, spiders, harvestmen, pseudoscorpions, collembolans, and beetles. As the glacier retreats, in place of bare paraglacial wastelands, grassland communities are formed that, after 10–14 years, are replaced by shrub vegetation and, on 30–35-year old surfaces, by forest communities. Most of the invertebrate groups, once “appearing” along a postglacial transect, were recorded from most older plots as well. Yet, their taxocoenoses underwent considerable transformations through increasing (or an increase turning into some decline in beetles) the species diversity and a strong, often complete change in the taxonomic composition and dominance structure. The most considerable transformations were observed at all major vegetation changes. The “appearance” of some groups in the transect was determined not only by dispersion capacities but mainly by the environmental conditions of particular habitats. When comparing the composition of the pioneer postglacial species complex of the study region with that in the mountains of Europe’s south and north, its high-degree regional specificity was noted, sometimes shown at the family level (in spiders). Spatial β-diversity of all larger taxa studied was mainly attributed to turnover (due to “the replacement model” of succession). The general level of change diminished towards the later succession stages. Endemic arthropod species were revealed both in pioneer grassland and developed forest communities.

Do different camera trap lures result in different detection rates of vertebrates because of their attractiveness to invertebrates?

SummaryThe type of attractant used in camera trap lures is recognised as an important methodological decision. We investigated whether the type of attractant in lures indirectly influences detectability of wildlife on cameras via differential attraction of invertebrates which themselves constitute prey of insectivorous animals. We indexed invertebrate abundance using pitfall and sticky‐traps at 36 camera stations deployed in a Latin Squares design for 5 days, with three lure options (peanut‐butter, tuna oil and control) in a coastal mosaic, at Cape Otway, Victoria, Australia. We classified vegetation types (habitat) as: low (no or sparse), medium (grass), and high (shrubs) from aerial imagery and estimated their percentage cover at each grid point (medium and high were uncorrelated and included as separate variables in models). We first examine if attractant types or the habitat influence invertebrate abundance and assemblage, and then examine whether invertebrate abundance influences vertebrate detectability on cameras. There was a trend for the composition of terrestrial invertebrate assemblages to be influenced by lure type (peanut‐butter, tuna oil and control attractants) and the proportional cover of medium height vegetation within 20 m; however, assemblage composition was clearly influenced by the proportional area of high vegetation cover within 20 m. The detection probability of insectivorous birds increased where medium‐sized (2.5–5 mm) flying invertebrates were present whereas insectivorous mammal detectability increased with terrestrial invertebrate species richness. Mammal detections are more likely associated with use of habitats that have more diverse invertebrate communities. This study provides some support to the hypothesis of the indirect mechanism whereby bird detections are influenced by invertebrate attraction to lures. Therefore, lure choice for camera traps is critical and the possibility of guild‐level biases in detection suggests that cautious interpretation of results is required.

Urban greening with shrubs can supercharge invertebrate abundance and diversity

In urban areas, diverse and complex habitats for biodiversity are often lacking. This lack of diversity not only compromises essential ecological processes, such as pollination and nutrient cycling, but also diminishes the resilience of urban ecosystems to pests and diseases. To enhance urban biodiversity, a possible solution is to integrate shrubs alongside trees, thereby increasing the overall amount of vegetation, structural complexity and the associated resource diversity. Here, using a common garden experiment involving a variety of trees and shrubs planted alone and in combination, we evaluate how canopy-associated invertebrate assemblages are influenced by vegetation type. In particular, we test whether the presence of shrubs, alone or with trees, results in increased abundance and taxonomic richness of invertebrates, compared to trees on their own. We found that the overall abundance of invertebrates, and that of specific functional groups (e.g., herbivores, pollinators, detritivores), was higher on shrubs, compared to trees, and when trees and shrubs were planted in combination (relative to trees on their own). Our results suggest that planting shrub and tree species with wide and dense crowns can increase the associated abundance and taxonomic and functional group richness of invertebrate communities. Overall, our findings indicate that urban planning would benefit from incorporating shrubs alongside urban trees to maximise invertebrate abundance, diversity and function in urban landscapes.

Density data for Lake Erie benthic invertebrate assemblages from 1930 to 2019.

Benthic invertebrates are important trophic links in food webs and useful bioindicators of environmental conditions, but long-term benthic organism abundance data across broad geographic areas are rare and historic datasets are often not readily accessible. This dataset provides densities of benthic macroinvertebrates collected from 1930 to 2019 during surveys in Lake Erie, a Laurentian Great Lake. The surveys were funded by the governments of the United States and Canada to investigate the status and changes in the benthic community. From the total of 21 lake-wide and basin-wide benthic surveys conducted in Lake Erie from 1929 to 2019, we were able to acquire data for 17 surveys, including species-level data for 10 surveys and data by higher taxonomic groups for seven surveys. Our amassed Lake Erie dataset includes data from 11 surveys (including five with species-level data) conducted in the western basin in 1930-2019, seven surveys (six with species-level data) in the central basin, and eight surveys (seven with species-level data) in the eastern basin (1973-2019). This Lake Erie dataset represents the most extensive temporal dataset of benthic invertebrates available for any of the Laurentian Great Lakes. Benthic samples were collected using Ponar or Shipek bottom dredges and taxa densities were calculated as individuals per square meter using the area of the dredge. Density data are provided for taxa in the Annelida, Arthropoda, Mollusca, Cnidaria, Nemertea, and Platyhelminthes phyla. Current taxonomy was used for most groups but, in a few cases, older taxonomic names were used for consistency with historical data. Analysis of this dataset indicates that eutrophication, water quality improvement, and dreissenid introduction were the major drivers of changes in the benthic community in the western basin, while hypoxia was a major factor in the central basin, and dreissenid introduction was the most important driver in the eastern basin. Considering the rarity of high taxonomic resolution long-term benthic data for lake ecosystems, this dataset could be useful to explore broader aspects of ecological theory, including effects of eutrophication, hypoxia, invasive species, and other factors on community organization, phylogenetic and functional diversity, and spatial and temporal scales of variation in community structure. In addition, the dataset could be useful for studies on individual species, including abundance and distribution, species co-occurrence, and how the patterns of dominance and rarity change over space and time. Use of this dataset for academic or educational purposes is encouraged as long as this data paper is properly cited.

Seasonal Changes of Surface-Active Beach Invertebrate Assemblages in Southern Central Victoria, Australia

Invertebrates play a critical role in beach ecosystems, and seasonal variation in their occurrence and abundance likely influences food webs. We examine and characterise seasonal patterns in invertebrate activity on a temperate, southern sandy dune and beach ecosystem at Venus Bay, Victoria, Australia. We index invertebrate abundance, diversity and assemblage composition at fixed-site pitfall traps which were deployed in four transects from the lower dunes to the beach. Seasonal differences occurred in assemblage composition (foredunes only), richness and abundance. Insects dominated assemblages in summer, spring and autumn; crustaceans dominated winter assemblages. Morphospecies richness was lowest in winter (139% higher in summer and 169% higher in autumn). Our results contrast with other studies from temperate beaches in that (1) richness was higher on beaches compared to in foredunes across all seasons and (2) abundance differed significantly such that winter abundance was higher than for all other seasons. Possible explanations include the exposed nature of the study foredunes, marine ecological subsides in the form of beach wrack in winter and/or between-site variations in such factors. Further studies would usefully examine between-beach variation in seasonality in invertebrate activity in foredunes and dunes.

Effect of coral‐giant clam artificial reef on coral recruitment: insights for restoration and conservation efforts

Coral recruitment is a vital process for the maintenance and recovery of coral reefs, particularly due to their decline from global change. While it is well established that larval settlement cues significantly influence coral recruitment, the investigation of recruitment success associated with the surrounding community mainly focuses on algae. To investigate other factors controlling this process, we examined the impact of benthic invertebrate assemblages on coral recruitment using artificial reefs. Three types of artificial reefs (mono‐, bi‐, and tri‐species) with different assemblages of three common species, Pocillopora acuta, Acropora cytherea, and Tridacna maxima, were studied over 8 months. This study revealed that benthic assemblages play a significant role in coral recruitment and survival. High biodiversity was found to enhance coral recruitment and inhibit potential negative cues from A. cytherea. Our findings underscore the importance of preserving high biodiversity using not only hard coral but a wide range of phyla, including bivalves, in coral restoration efforts. Maintaining sustainable populations is an important goal to reach in the face of the multiple threats that impact coral reefs.

Intertidal mussels as ecosystem engineers: maintenance of invertebrate assemblages amid intertidal stress gradients

Species that form complex biogenic structures may increase niche space for many others and are assumed to be paramount for whole‐assemblage stability and ecosystem functioning. Because they often ameliorate physical conditions, ecosystem engineering species are also predicted to become more important with environmental stress. Testing this hypothesis, however, has proven difficult because isolating facilitation effects along the entire stress gradient is challenging. Here we addressed motile invertebrate assemblages associated to the mid‐intertidal chthamalid barnacle cover at four rocky shores, either with (‘facilitated') or without (‘control') a secondary natural cover of small mussels (Mytilaster solisianus and Brachidontes darwinianus). Following a factorial balanced design, replicate samples were taken at three tidal heights in all sites, encompassing a clear gradient of thermal stress and desiccation potential along the vertical range of the mussel‐enriched zone. While observations on general abundance were mostly consistent with stress‐independent facilitation, results for richness, diversity and assemblage structure indicated overarching stress‐dependent responses. All these later three response variables steadily declined from the low to the high level in the control barnacle habitat but remained unaltered in the mussel‐facilitated habitat. Increased facilitation higher on the shore is mostly due to retention of stress‐vulnerable groups such as polychaetes, flatworms and large nematodes which virtually collapse in the higher control habitat, further indicating that mechanisms of mussel facilitation involve relief of environmental stress rather than protection from higher‐order consumers. Our results suggest that mussel ecosystem engineering was fully preserved during the summer season when sampling took place. Ongoing research simulating heat waves compatible to climate‐change scenarios will test whether mussel facilitation would hold over the coming decades.

Temporal dynamics of invertebrate community assembly in Lake Victoria since the late Pleistocene based on chitinous remains

Abstract Preserved assemblages of invertebrate remains in lacustrine sediment reveal temporal variations of community composition and environmental conditions. However, records for large tropical lakes are scarce. Lake Victoria, the largest tropical lake, has a dynamic history of changes in water level, biogeochemistry and fish community composition over the past ~17,000 cal yr BP. In order to quantify changes in the invertebrate assemblage of Lake Victoria from the late Pleistocene throughout the Holocene, we examined chitinous remains of Cladocera and larval dipterans (Chironomidae and Chaoboridae) from a sediment core (37 m water depth) dated from ~13,700 cal yr BP to present. We identified four major phases in the invertebrate assemblage throughout this period of lake history. Firstly, Chironomidae and Chaoboridae appeared at low abundances during the earliest stages of lake inundation in the late Pleistocene, at a time when Cladocera were notably absent. Secondly, chaoborids and chironomids increased in abundance during the mid‐Holocene, which coincided with high diatom production toward the end of the Holocene African Humid Period. Thirdly, starting ~4,700 cal yr BP, Alona, a predominantly littoral cladoceran genus, consistently appeared in the invertebrate assemblage alongside changes in mixing regimes and persisted throughout the late Holocene to the present. Fourthly, the arrival of both Chydorus and Bosmina longirostris marked the establishment of an abundant cladoceran assemblage at ~1,350 cal yr BP. The assemblage then gradually shifted toward the increasing dominance of B. longirostris, a planktonic cladoceran. Several of the observed changes in the invertebrate assemblage occurred concurrently with changes in climatic conditions in East Africa and diatom productivity that have been previously recorded in Lake Victoria. This multi‐millennial record of sedimentary invertebrate assemblages in Lake Victoria elucidates some of the temporal development of these communities throughout most of the dynamic modern history of the ecosystem.

The first cetacean from the early Oligocene of the SW German Mainz Basin: a probable cheek tooth of a mysticete (Mammalia: Cetacea)

AbstractDespite two centuries of fossils collecting, no cetacean remains from the Oligocene marine deposits of the Mainz Basin (western Germany) have ever been reported. Here, we describe a possible mysticete tooth from the sand pit of Eckelsheim, which exposes high energy deposits belonging to the Rupelian Alzey Formation. The latter has yielded a rich assemblage of vertebrates and invertebrates, but so far, only one marine mammal in the form of the sirenian Kaupitherium. The whale tooth in some ways resembles the m2 of Llanocetus from the latest Eocene of Seymour Island, Antarctica. If the find from the Mainz Basin is not a regionally evolved form, Llanocetus, which is known from the South Atlantic, could have migrated through the Atlantic realm during the early Oligocene. It cannot be excluded that the tooth represents a more widely occurring lineage, neither endemic nor necessarily related to llanocetids, that—given the generally poor Rupelian record—has not been well documented yet.

Heavy metal movement through insect food chains in pristine thermal springs of Yellowstone National Park.

Yellowstone National Park thermal features regularly discharge various heavy metals and metalloids. These metals are taken up by microorganisms that often form mats in thermal springs. These microbial mats also serve as food sources for invertebrate assemblages. To examine how heavy metals move through insect food webs associated with hot springs, two sites were selected for this study. Dragon-Beowulf Hot Springs, acid-sulfate chloride springs, have a pH of 2.9, water temperatures above 70°C, and populations of thermophilic bacterial, archaeal, and algal mats. Rabbit Creek Hot Springs, alkaline springs, have a pH of up to 9, some water temperatures in excess of 60°C, and are populated with thermophilic and phototrophic bacterial mats. Mats in both hydrothermal systems form the trophic base and support active metal transfer to terrestrial food chains. In both types of springs, invertebrates bioaccumulated heavy metals including chromium, manganese, cobalt, nickel, copper, cadmium, mercury, tin and lead, and the metalloids arsenic, selenium, and antimony resulting from consuming the algal and bacterial mat biomass. At least two orders of magnitude increase in concentrations were observed in the ephydrid shore fly Paracoenia turbida, as compared to the mats for all metals except antimony, mercury, and lead. The highest bioaccumulation factor (BAF) of 729 was observed for chromium. At the other end of the food web, the invertebrate apex predator, Cicindelidia haemorrhagica, had at least a 10-fold BAF for all metals at some location-year combinations, except with antimony. Of other taxa, high BAFs were observed with zinc for Nebria sp. (2180) and for Salda littoralis (1080). This accumulation, occurring between primary producer and primary consumer trophic levels at both springs, is biomagnified through the trophic web. These observations suggest trace metals enter the geothermal food web through the microbial mat community and are then transferred through the food chain. Also, while bioaccumulation of arsenic is uncommon, we observed five instances of increases near or exceeding 10-fold: Odontomyia sp. larvae (13.6), P. turbida (34.8), C. haemorrhagica (9.7), Rhagovelia distincta (16.3), and Ambrysus mormon (42.8).