The impact of atmospheric deposition on the aquatic ecosystem with special emphasis on lake productivity,Newfoundland, Canada

To document and analyze the ecosystem response to acidification and possible concurrent heavy metal enrichment process, a detailed paleoecological study was conducted in Lake 817, a small, and sensitive, second order lake, in insular Newfoundland. The inferred pH history of the lake was recreated using the region-specific equation relating fossil diatom taxa to pH. The profile demonstrated a fairly stable pH history over the bottom 22 cm of the sediment core with an appreciable pH decline in the upper 5 cm. The decrease of inferred pH began in the 1930's (ca. 1931 to 1944) and the lowest inferred pH value (5.3) was observed in the surface stratum. The decreasing pH trend (0.4 unit; 5.7 to 5.3) between ca. 1931 and 1985 correlated well with changes in sediment chemistry. Major elements (P, Mg, Ca, Na, and K) showed significant decrease in deposition primarily in the upper 3 cm level (ca. 1944). The profiles of selected metals (Fe, Mn, Cr, Cu, Zn, Pb, Co, Hg, As, and Ni) indicated that the deposition of these elements increased noticeably, primarily in the upper 3 cm level. The enrichment of Pb began earlier, about 50 years ago (1931 to 1944). The stratigraphy of fossil pigments (chlorophyll derivatives and total carotenoids) demonstrated a general trend of increasing accumulation upwards in the core while the only significant decrease in pigments was observed in the recent strata (ca. between 1957 to 1985). The most dramatic decrease of primary production occurred during ca. 1957 to 1974 period and this phenomenon was associated with increased levels of heavy metals. It seems that primary production in oligotrophic, acidifying lakes in Newfoundland is controlled more by nutrients loading and the possible toxicological effects of heavy metals, than directly by water acidity.     

Comparison of diatoms, fossil pigments and historical records as measures of lake eutrophication

1. Analysis of fossil diatoms and pigments was used to examine the effects of land-management practises on the trophic status of Williams Lake, a eutrophic lake in central British Columbia, Canada. Published weighted-average (WA) models were used to infer changes in total phosphorus concentration (TP) during the past 200 years. 2. Diatom-inferred TP (DI-TP) was compared to 20 years of direct chemical TP measurements to determine the accuracy of diatom-TP models in inferring mean summer TP in Williams Lake. Plant pigments were measured using high performance liquid chromatography (HPLC) to quantify historical changes in gross algal community composition and abundance and to evaluate further diatom-TP inferences. 3. Palaeolimnological analyses showed that Williams Lake has been productive throughout the last 200 years. Diatoms characteristic of alkaline, eutrophic conditions were continuously present c. 1765–1990 AD. Carotenoids from filamentous cyanobacteria (myxoxanthophyll, aphanizophyll) were regularly present in Williams Lake sediments, although cryptophytes (alloxanthin), diatoms (diatoxanthin), chlorophytes (lutein-zeaxanthin, b-phorbins), and siliceous algae (diatoms, chrysophytes) or dinoflagellates (fucoxanthin) were also important components of past algal communities. Terrestrial disturbance (railway and road constructions, cattle ranching) increased lake production, but resulted in relatively little permanent environmental change. 4. Comparison of DI-TP with measured TP (1972–91) showed that inferences from simple WA models were similar to average summer TP (39.1 vs. 35.2 μg TP l^–1). Inferences resulting from data manipulations that down-weighted eutrophic lakes (outlier elimination, bootstrapping) or diatom species (square-root transformation, tolerance-weighting) were weakly and negatively correlated with measured TP, introduced bias into inference models, or underestimated measured TP. These patterns suggest that, when using diatom-TP models developed from sparsely populated regions, accurate palaeoecological inferences for TP in eutrophic lakes should avoid data manipulations which down-weight the most productive sites and taxa. 5. Comparison of DI-TP and fossil-inferred algal abundance during the past 200 years suggested that changes in nutrient inputs accounted for relatively little variation in past algal abundance. Although past changes in total algal biomass (as β-carotene) and DI-TP were broadly similar, the two variables were not significantly correlated (α = 0.05). In contrast, changes in DI-TP were significantly correlated with mean concentrations of diatom-specific carotenoids (diatoxanthin), although the explanatory power was low (r² = 0.16). These patterns suggest that the DI-TP model reflects more closely environmental conditions in Williams Lake during periods of diatom growth, and not necessarily those when total algal biomass is greatest.     

The evolution of encephalization in caniform carnivorans

A weighted-average model, which reliably estimates endocranial volume from three external measurements of the neurocranium of extant taxa in the mammalian order Carnivora, was tested for its applicability to fossil taxa by comparing model-estimated endocranial volumes to known endocast volumes. The model accurately reproduces endocast volumes for a wide array of fossil taxa across the crown radiation of the Carnivora, three stem carnivoramorphan taxa, and Pleistocene fossils of two extant species. Applying this model to fossil taxa without known endocast volumes expanded the sample of fossil taxa with estimated brain volumes in the carnivoran suborder Caniformia from 11 to 60 taxa. This then allowed a comprehensive assessment of the evolution of relative brain size across this clade. An allometry of brain volume to body mass was calculated on phylogenetically independent contrasts for the set of extant taxa, and from this, log-transformed encephalization quotients (logEQs) were calculated for all taxa, extant, and fossil. A series of Mann-Whitney tests demonstrated that the distributions of logEQs for taxa early in caniform evolutionary history possessed significantly lower median logEQs than extant taxa. Median logEQ showed a pronounced shift around the Miocene-Pliocene transition. Support tests, based on likelihood ratios, demonstrated that the variances of these distributions also were significantly lower than among modern taxa, but logEQ variance increased gradually through the history of the clade, not abruptly. Reconstructions of ancestral logEQs using weighted squared-change parsimony demonstrate that increased encephalization is observed across all major caniform clades (with the possible exception of skunks) and that these increases were achieved in parallel, although an "ancestor-descendant differencing" method could not rule out drift as a hypothesis. Peculiarities in the estimated logEQs for the extinct caniform family Amphicyonidae were also investigated; these unusual patterns are likely due to a unique allometry in scaling brain to body size in this single clade.     

Intraseasonal predictability of natural phytoplankton population dynamics

It is difficult to make skillful predictions about the future dynamics of marine phytoplankton populations. Here, we use a 22‐year time series of monthly average abundances for 198 phytoplankton taxa from Station L4 in the Western English Channel (1992–2014) to test whether and how aggregating phytoplankton into multi‐species assemblages can improve predictability of their temporal dynamics. Using a non‐parametric framework to assess predictability, we demonstrate that the prediction skill is significantly affected by how species data are grouped into assemblages, the presence of noise, and stochastic behavior within species. Overall, we find that predictability one month into the future increases when species are aggregated together into assemblages with more species, compared with the predictability of individual taxa. However, predictability within dinoflagellates and larger phytoplankton (>12 μm cell radius) is low overall and does not increase by aggregating similar species together. High variability in the data, due to observational error (noise) or stochasticity in population growth rates, reduces the predictability of individual species more than the predictability of assemblages. These findings show that there is greater potential for univariate prediction of species assemblages or whole‐community metrics, such as total chlorophyll or biomass, than for the individual dynamics of phytoplankton species.     

Impacts of forestry planting on primary production in upland lakes from north‐west Ireland

Planted forests are increasing in many upland regions worldwide, but knowledge about their potential effects on algal communities of catchment lakes is relatively unknown. Here, the effects of afforestation were investigated using palaeolimnology at six upland lake sites in the north‐west of Ireland subject to different extents of forest plantation cover (4–64% of catchment area). ²¹⁰Pb‐dated sediment cores were analysed for carotenoid pigments from algae, stable isotopes of bulk carbon (δ¹³C) and nitrogen (δ¹⁵N), and C/N ratios. In lakes with >50% of their catchment area covered by plantations, there were two‐ to sixfold increases in pigments from cryptophytes (alloxanthin) and significant but lower increases (39–116%) in those from colonial cyanobacteria (canthaxanthin), but no response from biomarkers of total algal abundance (β‐carotene). In contrast, lakes in catchments with <20% afforestation exhibited no consistent response to forestry practices, although all lakes exhibited fluctuations in pigments and geochemical variables due to peat cutting and upland grazing prior to forest plantation. Taken together, patterns suggest that increases in cyanobacteria and cryptophyte abundance reflect a combination of mineral and nutrient enrichment associated with forest fertilization and organic matter influx which may have facilitated growth of mixotrophic taxa. This study demonstrates that planted forests can alter the abundance and community structure of algae in upland humic lakes of Ireland and Northern Ireland, despite long histories of prior catchment disturbance.     

The importance of even highly incomplete fossil taxa in reconstructing the phylogenetic relationships of the tetraodontiformes (acanthomorpha: pisces)

The use of fossils in the phylogenetics of extant clades traditionallyhas been a contentious issue. Fossils usually are relativelyincomplete, and their use commonly leads to an increase in thenumber of equally most parsimonious trees and a decrease inthe resolution of phylogenies. Fossils alone, however, providecertain kinds of information about the biological history ofa clade, and computer simulations have shown that even highlyincomplete material can, under certain circumstances, increasethe accuracy of a phylogeny, rather than decrease it. Because empirical data are still scarce on the effects of theinclusion of fossils on phylogenetic reconstructions, we attemptedto investigate this problem by using a relatively well-knowngroup of acanthomorph fishes, the Tetraodontiformes (triggerfishes,pufferfishes, and ocean sunfishes), for which robust phylogeniesusing extant taxa already exist and that has a well-studiedfossil record. Adding incomplete fossil taxa of tetraodontiformsusually increases the number of equally most parsimonious treesand often decreases the resolution of consensus trees. However,adding fossil taxa may help to correctly establish relationshipsamong lineages that have experienced high degrees of morphologicaldiversification by allowing for a reinterpretation of homologousand homoplastic features, increasing the resolution rather thandecreasing it. Furthermore, taxa that were scored for 25% ormore of their characters did not cause a significant loss ofresolution, while providing unique biological information.     

Patterns of predictability in coral reef community structure

The question of whether population numbers are predictable in coral reef communities is confronted directly by trying to predict abundances of benthic taxa both within and between two reefs on the central Great Barrier Reef. Using models derived via the Group Method of Data Handling (GMDH), taxon abundances were found to be more predictable at Davies Reef than at Myrmidon Reef and a significant number of taxa showed consistent predictability patterns in all tests. For most taxa, the predictability of benthic abundances increased steadily with increasing spatial scale. Water depth figured prominently in almost all of the models obtained, emphasizing its importance as a physical determinant of local taxon abundances.     

The first Loranthaceae fossils from Africa

An ongoing re-investigation of the early Miocene Saldanha Bay (South Africa) palynoflora, using combined light and scanning electron microscopy (single grain method), is revealing several pollen types new to the African fossil record. One of the elements identified is Loranthaceae pollen. These grains represent the first and only fossil record of Loranthaceae in Africa. The fossil pollen grains resemble those produced by the core Lorantheae and are comparable to recent Asian as well as some African taxa/lineages. Molecular and fossil signals indicate that Loranthaceae dispersed into Africa via Asia sometime during the Eocene. The present host range of African Loranthaceae and the composition of the palynoflora suggest that the fossil had a range of potential host taxa to parasitise during the early Miocene in the Saldanha Bay region.     

Increased Atmospheric SO2 Detected from Changes in Leaf Physiognomy across the Triassic–Jurassic Boundary Interval of East Greenland

The Triassic–Jurassic boundary (Tr–J; ∼201 Ma) is marked by a doubling in the concentration of atmospheric CO₂, rising temperatures, and ecosystem instability. This appears to have been driven by a major perturbation in the global carbon cycle due to massive volcanism in the Central Atlantic Magmatic Province. It is hypothesized that this volcanism also likely delivered sulphur dioxide (SO₂) to the atmosphere. The role that SO₂ may have played in leading to ecosystem instability at the time has not received much attention. To date, little direct evidence has been presented from the fossil record capable of implicating SO₂ as a cause of plant extinctions at this time. In order to address this, we performed a physiognomic leaf analysis on well-preserved fossil leaves, including Ginkgoales, bennettites, and conifers from nine plant beds that span the Tr–J boundary at Astartekløft, East Greenland. The physiognomic responses of fossil taxa were compared to the leaf size and shape variations observed in nearest living equivalent taxa exposed to simulated palaeoatmospheric treatments in controlled environment chambers. The modern taxa showed a statistically significant increase in leaf roundness when fumigated with SO₂. A similar increase in leaf roundness was also observed in the Tr–J fossil taxa immediately prior to a sudden decrease in their relative abundances at Astartekløft. This research reveals that increases in atmospheric SO₂ can likely be traced in the fossil record by analyzing physiognomic changes in fossil leaves. A pattern of relative abundance decline following increased leaf roundness for all six fossil taxa investigated supports the hypothesis that SO₂ had a significant role in Tr–J plant extinctions. This finding highlights that the role of SO₂ in plant biodiversity declines across other major geological boundaries coinciding with global scale volcanism should be further explored using leaf physiognomy.     

Phytoplankton abundance and pigment changes during simulated in situ dilution experiments in estuarine waters: possible artifacts caused by algal light adaptation

I performed a dilution experiment during summer in mesohalineChesapeake Bay, comparing net growth rates of phytoplanktonbased on increases in accessory pigments with those based oncell counts of corresponding algal taxa. Fucoxanthin and peridininincreases were poor predictors of cell growth rates for diatomsand dinofiagellates, respectively, especially in the high dilutions(90% filtered seawater), while zeaxanthin predicted growth ratesof coccoid cyanobacteria closely. The insensitivity of microscopeestimates for rare, large phytoplankters may have contributedto the disparity between pigment and cell growth rates, butthis effect is argued to be small because all species presentat >1 cell ml^–1 were enumerated. Further experimentswith phytoplankton cultures suggest that light adaptation canlead to underestimates of growth when pigments are used as asurrogate for cell abundance in turbulent, eutrophic waterswhere the light field experienced by phytoplankton in Situ 5difficult to simulate.     

Different strategies for photoprotection during autumn senescence in maple and oak

During autumn senescence, plants must disassemble the photosynthetic apparatus as nutrients are remobilized from the leaves. The goal of this study was to examine changes in relative abundance of photosynthetic proteins and pigments throughout autumn senescence in order to understand the mechanisms of photoprotection used during this process. We sampled leaves from two deciduous tree species [sugar maple (Acer saccharum Marsh.) and swamp white oak (Quercus bicolor Willd.)] throughout autumn during 2010 and 2013. Chlorophyll fluorescence was measured, thylakoids were isolated for western blotting with antibodies to individual proteins and pigment content was assessed. Both species retained high photochemical efficiency until late autumn and showed earlier onset of degradation of photosystem I relative to photosystem II. The species differed in the timing and pattern of degradation of individual photosynthetic proteins and pigments. In maple, there were increases in anthocyanins, more rapid degradation of light‐harvesting proteins and enrichment of xanthophyll cycle pigments in late autumn. In oak, light‐harvesting proteins were retained in higher abundance throughout autumn, PsbS levels increased during early autumn and lutein was enriched in late autumn samples. The results suggest that the species differ in strategies for photoprotection during autumn senescence.     

Early Cretaceous angiosperm invasion of Western Europe and major environmental changes

BACKGROUND AND AIMS: At the beginning of the Late Cretaceous, angiosperms already inhabited all the environments and overtopped previously gymnosperm-dominated floras, especially in disturbed freshwater-related environments. The aim of this paper is to define what fossil plant ecology occurred during the early Cretaceous in order to follow the early spread of angiosperm taxa. METHODS: Floristic lists and localities from the Barremian to the Albian of Europe are analysed with the Wagner's Parsimony Method. KEY RESULTS: The Wagner's Parsimony Method indicates that (a) during the Barremian, matoniaceous ferns formed a savannah-like vegetation, while angiosperms composed freshwater aquatic vegetation; (b) during the Late Aptian humid phase, conifers increased, while matoniaceous ferns decreased, reflecting the closure of the vegetation; and (c) from the Albian, warmer and drier conditions induced the recovery of the matoniaceous ferns, while core angiosperms first developed in floodplains. CONCLUSIONS: During the late Early Cretaceous (Barremian-Albian), angiosperms showed a stepwise widening of their ecological range, being recorded first during the Barremian as aquatic plant mega-remains and at the Cenomanian onwards occurred in all the environments.     

Functional morphology of cercopithecoid primate metacarpals

The primate fossil record suggests that terrestriality was more common in the past than it is today, particularly among cercopithecoid primates. Whether or not a fossil primate habitually preferred terrestrial substrates has typically been inferred from its forelimb anatomy. Because extant large-bodied terrestrial cercopithecine monkeys utilize digitigrade hand postures during locomotion, being able to identify if a fossil primate habitually adopted digitigrade postures would be particularly revealing of terrestriality in this group. This paper examines the functional morphology of metacarpals in order to identify osteological correlates of digitigrade versus palmigrade hand postures. Linear measurements were obtained from 324 individuals belonging to digitigrade and palmigrade cercopithecoid species and comparisons were made between hand posture groups. Digitigrade taxa have shorter metacarpals, relative to both body mass and humerus length, than palmigrade taxa. Also, digitigrade taxa tend to have metacarpals with smaller dorsoventral diameters, relative to the product of body mass and metacarpal length, compared to palmigrade taxa. The size and shape of the metacarpal heads do not significantly differ between hand posture groups. Multivariate analyses suggest that metacarpal shape can only weakly discriminate between hand posture groups. In general, while there are some morphological differences in the metacarpals between hand posture groups, similarities also exist that are likely related to the fact that even digitigrade cercopithecoids can adopt palmigrade hand postures in different situations (e.g., terrestrial running, arboreal locomotion), and/or that the functional demands of different hand postures are not reflected in all aspects of metacarpal morphology. Therefore, the lack of identifiable adaptations for specific hand postures in extant cercopithecoids makes it difficult to determine a preference for specific habitats from fossil primate hand bones.     

Interdecadal declines in flood frequency increase primary production in lakes of a northern river delta

Human activities and climate change have greatly altered flooding regimes in many of the world's river deltas, but the impact of such changes remains poorly quantified on decadal to multidecadal timescales. This study identified the response of delta lake primary production (measured as the concentration of sedimentary pigments) to variations in flood frequency using spatial surveys and paleolimnological analyses of lakes in the Peace‐Athabasca Delta (PAD), Canada. Surveys of 61 lakes spanning a range of hydrological conditions showed that those lakes that received flood waters less frequently were associated with elevated algal production (surface sedimentary pigments) and, in some lakes, increased growth of emergent macrophytes and epiphytic diatoms. Paleolimnological analyses of five lakes corroborated the contemporary spatial survey results by showing that production of pigments from most algal groups increased during recent periods of lower flood frequency in the 20th century as determined from increases in cellulose‐inferred lake‐water oxygen isotope composition and plant macrofossils, but remained stable in a ‘reference’ basin. In general, past periods of elevated algal production coincided with the increased abundance of submerged macrophytes or emergent vegetation that provide habitat for attached algae. These results suggest that interdecadal declines in river discharge arising from increased aridity, hydrologic regulation or consumptive water use will cause long‐term increases in primary production and alter ecosystem processes (carbon sequestration, biological diversity) in aquatic delta ecosystems similar to the PAD where lakes become nutrient‐rich in the absence of flooding.     

Floristic turnover in Iceland from 15 to 6 Ma – extracting biogeographical signals from fossil floral assemblages

Aim This study aims to document the floristic changes that occurred in Iceland between 15 and 6 Ma and to establish the dispersal mechanisms for the plant taxa encountered. Using changing patterns of dispersal, two factors controlling floristic changes are tested. Possible factors are (1) climate change, and (2) the changing biogeography of Iceland over the time interval studied; that is, the presence or absence of a Miocene North Atlantic Land Bridge. Location The North Atlantic. Methods Species lists of fossil plants from Iceland in the time period 15 to 6 Ma were compiled using published data and new data. Closest living analogues were used to establish dispersal properties for the fossil taxa. Dispersal mechanisms of fossil plants were then used to reconstruct how Iceland was colonized during various periods. Results Miocene floras of Iceland (15–6 Ma) show relatively high floristic turnover from the oldest floras towards the youngest; and few taxa from the oldest floras persist in the younger floras. The frequencies of the various dispersal mechanisms seen in the 15‐Ma floras are quite different from those recorded in the 6‐Ma floras, and there is a gradual change in the prevailing mode of dispersal from short‐distance anemochory and dyschory to long‐distance anemochory. Two mechanisms can be used to explain changing floral composition: (1) climate change, and (2) the interaction between the dispersal mechanisms of plants and the increasing isolation of proto‐Iceland during the Miocene. Main conclusions Dispersal mechanisms can be used to extract palaeogeographic signals from fossil floras. The composition of floras and dispersal mechanisms indicate that Iceland was connected both to Greenland and to Europe in the early Middle Miocene, allowing transcontinental migration. The change in prevalence of dispersal modes from 15 to 6 Ma appears to reflect the break‐up of a land bridge and the increasing isolation of Iceland after 12 Ma. Concurrent gradual cooling and isolation caused changes in species composition. Specifically, the widening of the North Atlantic Ocean prevented taxa with limited dispersal capability from colonizing Iceland, while climate cooling led to the extinction of thermophilous taxa.     

Paleobotanical remains from the Paleocene–lower Eocene Vagadkhol Formation, western India and their paleoclimatic and phytogeographic implications

A small assemblage of macro- and micro floral remains comprising fossil leaf impressions, silicified wood, spores, and pollen grains is reported from the Paleocene–lower Eocene Vagadkhol Formation (=Olpad Formation) exposed around Vagadkhol village in the Bharuch District of Gujarat, western India. The fossil leaves are represented by five genera and six species, namely, Polyalthia palaeosimiarum (Annonaceae), Acronychia siwalica (Rutaceae), Terminalia palaeocatapa and T. panandhroensis (Combretaceae), Lagerstroemia patelii (Lythraceae), and a new species, Gardenia vagadkholia (Rubiaceae). The lone fossil wood has been attributed to a new species, Schleicheroxylon bharuchense (Sapindaceae). The palynological assemblage, consisting of pollen grains and spores, comprises eleven taxa with more or less equal representation of pteridophytes, gymnosperms, and angiosperms. Angiospermous pollen grains include a new species Palmidites magnus. Spores are mostly pteridophytic but some fungal spores were also recovered. All the fossil species have been identified in the extant genera. The present day distribution of modern taxa comparable to the fossil assemblage recorded from the Vagadkhol area mostly indicate terrestrial lowland environment. Low frequency of pollen of two highland temperate taxa (Pinaceae) in the assemblage suggests that they may have been transported from a distant source. The wood and leaf taxa in the fossil assemblage are suggestive of tropical moist or wet forest with some deciduousness during the Paleocene–early Eocene. The presence of many fungal taxa further suggests the prevalence of enough humidity at the time of sedimentation.     

Metamorphosis of Wing Motor System in the Silk Moth, Bombyx mori: Origin of Wing Motor Neurons

The origin of the peripheral nerve and motor neurons that innervate the adult mesothoracic dorsal longitudinal muscles (DLMs) was examined in the silk moth, Bombyx mori . The anatomical features of the peripheral nerve and motor neurons were investigated by dissection, electron microscopy, and cobalt back-fill staining at different pupal stages. These studies showed that the peripheral nerve (IIN1c) that innervates the adult DLMs originates from a branch (db branch) of the larval mesothoracic dorsal nerve that innervates the larval DLMs. During metamorphosis the larval nerve shortens or lengthens locally without change in its basic branching pattern, and the db branch moves towards the mesothoracic ganglion to become the IIN1c. All the adult DLM motor neurons are from larval ones. Nine of the 14 larval DLM motor neurons survive during metamorphosis to become adult DLM motor neurons, and 5 disappear in early pupal stages.     

Fossilization processes of graptolites: insights from the experimental decay of Rhabdopleura sp. (Pterobranchia)

Laboratory experiments documenting the decomposition pattern of extant organisms are used to reconstruct the anatomy and taphonomy of fossil taxa. The subclass Graptolithina (Hemichordata: Pterobranchia) is a significant fossil taxon of the Palaeozoic era, represented by just one modern genus, Rhabdopleura. The rich graptolite fossil record is characterized by an almost total absence of fossil zooids. Here we investigated the temporal decay pattern of Rhabdopleura sp. tubes, stolons and single zooids removed from the tubarium. Tubes showed decay after four days, when fuselli began to separate from the tube walls. This rapid loss may explain the absence of fuselli from some graptolite fossils. The black stolon did not show decay until day 155. One day after their removal, zooids quickly decomposed in the following temporal sequence: (1) tentacles; (2) ectoderm; (3) arms; (4) gut; (5) cephalic shield, leading to complete disappearance of recognizable body parts in the majority of experimental zooids within 64–104 h. The most resistant zooid features to decay (61 days) were black‐pigmented granules. These results indicate that tubes and the black stolon would persist for weeks across death, transport and burial, whereas a complete decay of zooid features occurs in few days, providing an explanation for the overall poor record of fossil graptolite zooids and suggesting that recorded silhouettes of fossil zooids may be attributed to fossil decay‐resistant pigments.     

Indicator value of midge larvae (Diptera: Nematocera) in shallow boreal lakes with a focus on habitat,water quality,and climate

Identification of indicator species is invaluable for lake management and long-term environmental change assessments. In this study, multi- and intralake datasets were investigated for their fossil midge assemblages (mostly Chironomidae) in the surface sediment layers representing the modern faunal composition. The aim was to examine taxon-specific responses to selected key variables and to assign indicator taxa for these environmental factors. Taxon-specific optima and tolerances were calculated and the significance of a particular environmental variable in explaining the distribution patterns was tested for each taxa. The results showed that numerous taxa had significant relationship with the environmental variables of interest. Thus, several midge indicator taxa were identified for the key variables. For the interest of palaeolimnology, the present results imply that when reconstructing long-term changes in a single environmental variable, variability in other regional, local or in-lake variables can distort the inference due to the complex taxon-specific responses to multiple environmental factors.