Numerical Abundance Research Articles

Vertical Stratification and Seasonal Dynamics of Coleoptera in Open Biotopes of Forest Ecosystems (Centre of European Russia)

There are few studies on the vertical distribution and seasonal activity of arthropods in open habitats (in glades) in temperate forests due to methodological problems associated with the arrangement of certain structures for trapping. However, glades in forests are places of significant biodiversity of native animals, which are attracted to such areas by the possibilities of nutrition, reproduction, and wintering. The research was carried out on the territory of the Republic of Mordovia (the center of the European part of Russia). Fermental traps (bait—fermenting beer with sugar) were used to collect Coleoptera. They were installed on a special structure at heights of 2, 4, 6, 8, and 10 m. The collections were carried out from May to October 2020 in a glade with an area of 0.93 hectares in a deciduous forest. At the end of the research, 745 specimens of 80 species were registered from 30 Coleoptera families. The greatest species diversity was recorded in Nitidulidae (11 species), Cerambycidae (10 species), Scarabaeidae (7 species), Elateridae, Coccinellidae, and Curculionidae (5 species each). The greatest species diversity (53 species) and numerical abundance were obtained at a height of 2 m, and the smallest one (16 species) at a height of 10 m. The largest differences in the Jaccard similarity index were obtained between samples from a height of 2 and 10 m. The maximum values of the Shannon index and the minimum values of the Simpson index were recorded at the height of 2 m. The most significant relative number of saproxylic species was obtained at a height of 4 m. The relative number of anthophilic species was minimal at a height of 10 m. The seasonal dynamics of Coleoptera abundance were the same at different heights and the highest abundance was observed in late May and early June. However, the seasonal dynamics were different for some Coleoptera species in the glade located and inside the forest. Our data confirm the relevance of sampling in open biotopes at different heights in the study of arthropod biodiversity.

Sulphur-rich cold gas around the hot core precursor G328.2551-0.5321

Context.During the process of star formation, the dense gas undergoes significant chemical evolution leading to the emergence of a rich variety of molecules associated with hot cores and hot corinos. However, the physical conditions and the chemical processes involved in this evolution are poorly constrained; the early phases of emerging hot cores in particular represent an unexplored territory.Aims.We provide here a full molecular inventory of a massive protostellar core that is proposed to represent a precursor of a hot core. We investigate the conditions for the molecular richness of hot cores.Methods.We performed an unbiased spectral survey towards the hot core precursor associated with clump G328.2551-0.5321 between 159 GHz and 374 GHz, covering the entire atmospheric windows at 2 mm, 1.2 mm, and 0.8 mm. To identify the spectral lines, we used rotational diagrams and radiative transfer modelling assuming local thermodynamical equilibrium.Results.We detected 39 species plus 26 isotopologues, and were able to distinguish a compact (~2″), warm inner region with a temperature, T, of ~100 K, a colder, more extended envelope withT ~20 K, and the kinematic signatures of the accretion shocks that have previously been observed with ALMA. We associate most of the emission of the small molecules with the cold component of the envelope, while the molecular emission of the warm gas is enriched by complex organic molecules (COMs). We find a high abundance of S-bearing molecules in the cold gas phase, including the molecular ions HCS+and SO+. The abundance of sulphur-bearing species suggests a low sulphur depletion, with a factor of ≥1%, in contrast to low-mass protostars, where the sulphur depletion is found to be stronger. Similarly to other hot cores, the deuterium fractionation of small molecules is low, showing a significant difference compared to low-mass protostars. We find a low isotopic ratio in particular for12C/13C of ~30, and32S/34S of ~12, which are about two times lower than the values expected at the galactocentric distance of G328.2551-0.5321. We identify nine COMs (CH3OH, CH3OCH3, CH3OCHO, CH3CHO, HC(O)NH2, CH3CN, C2H5CN, C2H3CN, and CH3SH) in the warm component of the envelope, four in the cold gas, and four towards the accretion shocks.Conclusions.The presence of numerous molecular ions and high abundance of sulphur-bearing species originating from the undisturbed gas may suggest a contribution from shocked gas at the outflow cavity walls. The molecular composition of the cold component of the envelope is rich in small molecules, while a high abundance in numerous species of COMs suggests an increasing molecular complexity towards the warmer regions. The molecular composition of the warm gas is similar to that of both hot cores and hot corinos, but the molecular abundances are closer to the values found towards hot corinos than to values found towards hot cores. Considering the compactness of the warm region and its moderate temperature, we suggest that thermal desorption has not been completed towards this object yet, representing an early phase of the emergence of hot cores.

Comparing beach seine and gillnet sampling methods in fish assemblages from Southern Brazilian shallow coastal lakes

The aim of this study was to compare littoral zone fish assemblage richness, composition, dominance and size patterns between beach seine and gillnets sampling methods in coastal lakes at Tramandaí river, Southern Brazil. Monthly samples were taken in the littoral zones of six coastal shallow lakes (Itapeva, Quadros, Malvas, Fortaleza, Rondinha and Barros). Dominance and similarity analyses showed differences in species composition, numerical abundance and biomass among the sampling methods. Eleven species were dominant, but only one (Psalidodon aff. fasciatus) was dominant to both sampling methods. Beach seines sampled individuals with a total length ranging from 20 to 80 mm, while gillnets sampled individuals with a total length over 100 mm. An assemblage with high species richness, dominated by small fishes was found in the lake’s margins. In contrast, an assemblage with lower species richness comprised of larger fishes was found in inner areas. The methods are complementary in accessing species richness. Beach seine is a better alternative for monitoring programs as it provides reliable data at lower cost. These results may be useful in the sample design of future research or in the monitoring of ichthyofauna.

ANATOMICAL ELUCIDATION OF DAMAGE INDUCED BY Tetranychus neocaledonicus ANDRE (ACARI: TETRANYCHIDAE) ON CASSAVA LEAVES

Ultra-structural elucidation of feeding injury inflicted by the vegetable mite, Tetranychus neocaledonicus Andre on the leaves of cassava was done following TEM technique to elucidate anatomical damage and for a detailed investigation into the fine structural changes to Manihot esculenta Crantz leaves following spider mite feeding. The gravity of injury caused to the host leaves was found to increase proportionately with the progressive feeding of the vegetable mites. Leaves with high infestation had marked reduction in thickness following disruption of epidermis and reduction of palisade and spongy mesophyll tissues. Further, there was decline in numerical abundance of cells and organelles like chloroplasts, coagulated protoplasts, structural aberrations at the cellular level, increased space in the mesophyll layers, extensive disruption of the palisade coupled with damage to adjacent cells that were not directly attacked by the mites.

Comammox bacteria predominate among ammonia-oxidizing microorganisms in municipal but not in refinery wastewater treatment plants

Comammox bacteria have proved to be one dominant and significant ammonia-oxidizing microorganisms (AOMs) in municipal wastewater treatment plants (WWTPs), however, it still remains unknown about their abundance and diversity in industrial WWTPs. In this study, activated sludge samples from 8 municipal WWTPs and 6 industrial WWTPs treating refinery wastewater were taken and analyzed using qPCR and amoA gene sequencing. Intriguingly, quantitative real-time PCR (qPCR) results suggested that comammox bacteria had a higher numerical abundance compared with ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in municipal WWTPs but did not in refinery WWTPs. Moreover, comammox amoA sequences obtained from high-throughput sequencing were retrieved from all the 8 municipal samples but only 1 industrial sample. Further phylogenetic analysis revealed that N. nitrosa cluster accounted for as high as 79.56% of the total comammox affiliated sequences, which was the most numerically abundant comammox species in municipal WWTPs. This study provided new insights into the abundance and diversity of comammox bacteria in the biological nitrification process in municipal and refinery wastewater treatment systems.

Macrofauna Associated With a Rhodolith Bed at an Oceanic Island in the Eastern Tropical Pacific (Isla del Coco National Park, Costa Rica)

Rhodoliths are round calcareous red algae that form extensive beds and associated with them are a diverse suite of species. Rhodolith beds are among the least known coastal–marine ecosystems, and even less is understood about their associated flora and fauna. Here, we present an evaluation of the biodiversity larger than 500 μm associated with rhodoliths at Isla del Coco National Park, Costa Rica, an oceanic island in the Eastern Tropical Pacific, 500 km offshore of the mainland. This research determined the influence of rhodolith degree of aggregation (distance among individual rhodolith) as well as rhodolith complexity, volume, and mass in relation to the diversity, composition, and biomass of the associated fauna. A total of 145 taxa were collected in 60 rhodolith samples. Arthropods, polychaetes, and mollusks were the dominant taxa in terms of richness, and crustaceans + acari represented >50% of the total abundance. Five potentially new species were collected in this study. Collections identified 31 new records, with 20 of them being newly reported genera for Isla del Coco. Many of the organisms found were juveniles as well as adult stages bearing eggs, demonstrating the importance of this ecosystem. The faunal composition changed along the gradient of rhodolith aggregation. Moderately aggregated rhodoliths (separated by 5 to 10 cm) had the highest diversity, with the highest averages of taxon richness and total numerical abundance and the highest faunal biomass. There were more organisms in more complex rhodoliths; nevertheless, the complexity of the rhodolith did not affect the number of taxa or total organism biomass. Larger rhodoliths, in size and mass, favored higher amounts of taxa and organisms. The rhodolith bed studied is an example of the intermediate disturbance hypothesis because the highest value of biodiversity of invertebrates was at the moderate aggregation level of rhodoliths. In this density of rhodoliths, the fauna was less exposed to hard environmental conditions and prevented dominant species.

Soil Mite (Acari: Mesostigmata) Communities and Their Relationships with Some Environmental Variables in Experimental Grasslands from Bucegi Mountains in Romania.

Simple SummaryGrasslands are critical from ecological and pastoral points of view, being defined by valuable species of plants and animals. One of the most important biological components is soil fauna, as soil mites. The objective of the present study was to study the relation between fertilised experimental grasslands and soil mite (Acari: Mesostigmata) fauna. In this context, the aims of the research were to investigate the structural differences between mite communities and some key environmental variables from in five fertilised plots, the correlations of these variables with mites, and the dispersal rates of these invertebrate communities between grasslands. The number of species and their abundances recorded the highest values in the reseeded grassland and the lowest in the control plot. An indicator species analysis identified characteristic species for each experimental plot. The structural differences of the mite communities between plots were due to the significant influences of environmental variables. Between the experimental grasslands dominated by the accessory and accidental species, the dispersal rate of the mite communities was higher, in comparison were populations characterised by the constant species. Controlled and rationale use of agrochemicals (organic and chemic), influenced positive the numerical abundance and species richness of the soil mite communities, improving the soil environmental conditions for these invertebrates.The main objective of the study was to analyse, for the first time in Romania, the relationships between five experimental grasslands and Mesostigmata fauna, considering: (1) the structural differences between mite communities; (2) the variations in some important abiotic factors (vegetation cover, soil temperature, soil moisture content, pH, soil resistance at penetration); and (3) the influence of these abiotic factors on the structures of Mesostigmata mite communities and the dispersal rates of these communities between the investigated plots. In total, 250 soil samples were analysed in July 2017, revealing the presence of 30 species, with 1163 individuals. Using the multivariate analysis, we observed that each experimental plot was defined by characteristic environmental conditions, i.e., vegetation cover, soil moisture content, and soil temperature differed significantly between the experimental grasslands. Each experimental plot was characterised by a specific indicator species and population parameters (numerical abundance and species richness). The effects of these soil variables were even demonstrated at species level: Veigaia planicola, Geolaelaps nolli, and Gamasellodes insignis were influenced by vegetation cover, Lysigamasus conus and Dendrolaelaps foveolatus by soil temperature. The dispersal rates of mite communities from one plot to another were higher in the grasslands, where there were euconstant–constant species.

Responses of a Natural Phytoplankton Community From the Drake Passage to Two Predicted Climate Change Scenarios

Contrasting models predict two different climate change scenarios for the Southern Ocean (SO), forecasting either less or stronger vertical mixing of the water column. To investigate the responses of SO phytoplankton to these future conditions, we sampled a natural diatom dominated (63%) community from today’s relatively moderately mixed Drake Passage waters with both low availabilities of iron (Fe) and light. The phytoplankton community was then incubated at these ambient open ocean conditions (low Fe and low light, moderate mixing treatment), representing a control treatment. In addition, the phytoplankton was grown under two future mixing scenarios based on current climate model predictions. Mixing was simulated by changes in light and Fe availabilities. The two future scenarios consisted of a low mixing scenario (low Fe and higher light) and a strong mixing scenario (high Fe and low light). In addition, communities of each mixing scenario were exposed to ambient and low pH, the latter simulating ocean acidification (OA). The effects of the scenarios on particulate organic carbon (POC) production, trace metal to carbon ratios, photophysiology and the relative numerical contribution of diatoms and nanoflagellates were assessed. During the first growth phase, at ambient pH both future mixing scenarios promoted the numerical abundance of diatoms (∼75%) relative to nanoflagellates. This positive effect, however, vanished in response to OA in the communities of both future mixing scenarios (∼65%), with different effects for their productivity. At the end of the experiment, diatoms remained numerically the most abundant phytoplankton group across all treatments (∼80%). In addition, POC production was increased in the two future mixing scenarios under OA. Overall, this study suggests a continued numerical dominance of diatoms as well as higher carbon fixation in response to both future mixing scenarios under OA, irrespective of different changes in light and Fe availability.

The Key Role of Peroxisomes in Follicular Growth, Oocyte Maturation, Ovulation, and Steroid Biosynthesis.

The absence of peroxisomes can cause disease in the human reproductive system, including the ovaries. The available peroxisomal gene-knockout female mouse models, which exhibit pathological changes in the ovary and reduced fertility, are listed in this review. Our review article provides the first systematic presentation of peroxisomal regulation and its possible functions in the ovary. Our immunofluorescence results reveal that peroxisomes are present in all cell types in the ovary; however, peroxisomes exhibit different numerical abundances and strong heterogeneity in their protein composition among distinct ovarian cell types. The peroxisomal compartment is strongly altered during follicular development and during oocyte maturation, which suggests that peroxisomes play protective roles in oocytes against oxidative stress and lipotoxicity during ovulation and in the survival of oocytes before conception. In addition, the peroxisomal compartment is involved in steroid synthesis, and peroxisomal dysfunction leads to disorder in the sexual hormone production process. However, an understanding of the cellular and molecular mechanisms underlying these physiological and pathological processes is lacking. To date, no effective treatment for peroxisome-related disease has been developed, and only supportive methods are available. Thus, further investigation is needed to resolve peroxisome deficiency in the ovary and eventually promote female fertility.

FIRST DATA ON THE ICHTYOLOGICAL POPULATION OF A NEW HYDROELECTRIC LAKE: CASE OF THE DAM OF SOUBRE, COTE DIVOIRE

The new dam of Soubre in Cote dIvoire resulted in the creation of a 17.3 km2 lake in April 2017. After an 18-month ban, the exploitation of fishery resources started and is mainly carried out by foreignBozofishermen. The present study, whose main objective was to conduct the ichthyological inventory of this lake, was executed between August 2019 and July 2021. The artisanal catches of fishermen were examined monthly in the three main landing sites of the lake. The species richness of the lake was estimated at 42 species. The specific weight composition of the catches indicates the predominance of the catfish Chrysichthys nigrodigitatus with 16% of catches.For numerical abundance, the Mormyridae Marcusenius senegalensis leads the catches with a17% rate. It should be noted that this study allowed the observation of specimens of the freshwater shrimp of the genus Macrobrachium upstream of the lake, in the river-lake transition zone, while no individual of this species was captured in the lake.

Deep and cold: are Boreal and Arctic finned octopods, Stauroteuthis syrtensis and Cirroteuthis muelleri (Cephalopoda, Octopoda, Cirrata), ecological analogues?

Stauroteuthis syrtensis and Cirroteuthis muelleri were studied based on representative material collected in Greenland, Iceland, and the Barents Sea and adjacent deep-sea areas (96 stations and 165 individuals for S. syrtensis, and 82 stations and 215 individuals for C. muelleri). The species occur on the border of the Arctic and the northern North Atlantic; S. syrtensis is a southern species and C. muelleri is a northern species, in the area from the Denmark and Davis Straits and associated underwater ridges. These species were demonstrated to be ecological analogues since they: a) occupy the same depths; b) reach the same abundance density; c) reach virtually the same biomass density when corrected for size differences; and d) their food spectra largely coincide. Temperature, not depth, is a principal factor that prevents these species from crossing the border between the Arctic and the northern North Atlantic, with mean habitat temperatures of 3.5 ± 0.06 °C for S. syrtensis and 0.3 ± 0.06 °C for C. muelleri. This study provides unprecedented density estimates for the North Atlantic and Arctic Cirrata: the highest in the world ocean in terms of biomass and second highest in terms of numerical abundance. Food spectra of the studied species consist of Calanoida (including eurybathic Paraeucheta spp. and Calanus spp., and deep-sea Bradyidius similis), Mysidacea and Isopoda (including deep-sea Eurycopinae) (Crustacea), and in C. muelleri also Cumacea, Amphipoda (Crustacea) and Polychaeta (Polynoidae). Additionally, this study: a) provides specific growth and morphometric equations; b) provides equations to estimate mantle length (ML) and body mass (BM) from beak measurements, and BM of fresh individuals (for modelling purposes or predators diet analyses) from BM of fixed individuals; c) reports maximum sizes for C. muelleri (ML 170 mm, total length 400 mm, BM 781.0 g); and d) reports findings of rarely encountered juvenile cirrates.

Lobos marinos de un pelo sudamericanos Otaria flavescens ¿buenos indicadores de cambios espaciales y temporales relativos en la distribución y abundancia de los recursos marinos?

ABSTRACT. Oceanographic fluctuations and changes in ocean productivity directly affect the abundance and distribution of prey species, which in turn, affect the population status of their predators. In order to have a better understanding of this predator-prey relationship, the aim of the present study was to analyze the diet of the South American Sea Lion Otaria flavescens (Shaw, 1800) in two rookeries of the San Matias Gulf, in northern Patagonia (Argentina). A total of 52 scat samples of O. flavescens were collected in the Promontorio Belén colony and 35 in Caleta de los Loros during the late spring of 2011. The analysis of the samples indicated that at both localities fish occurred in 100% of scats with prey remains, followed by cephalopods (32.3%) and crustaceans (21.4%). The fish Raneya brasiliensis (Kaup, 1856) constituted the main prey taxon, both in terms of occurrence and numerical abundance. The octopod Octopus tehuelchus (d’ Orbigny, 1834) and squids of the genus Doryteuthis constituted the dominant cephalopod prey. It is concluded that sea lions focused their foraging activity on those species of demersal and benthic habits, associated with coastal and shelf waters. Furthermore, this study reports for the first time the feeding habits of the South American Sea Lion colony of Promontorio Belén, second in population size of Río Negro province.

Hydrological connectivity, surface water quality and distribution of fish species within sub-locations of an urban oxbow lake, East India

Ecological processes and distribution of biodiversity within river floodplains are driven by the hydrological regime of the area. The relationship between fish abundance/diversity and surface water quality at four impact points of the Sashadanga oxbow lake was examined based on hydrological connectivity (distance of lake sections from parent channel; density of buffer vegetation and hydrological phases of seasons). Fish sample populations (n = 1440) belonging to 10 orders showed greater numerical abundance in the pre-and post-flooding phases. Oxbow sites proximal to the parent channel showed higher comprehensive pollution index (CPI), higher dominance and lower species evenness during the pre-monsoon (minor flooding) and vice versa during the monsoon and post-monsoon (greater flooding periods). Diversity descriptors using curve/asymptote based on Hill’s numbers indicate significant site-specific fish diversity within the oxbow lake at different seasons. Discriminant analysis revealed that change in temperature, turbidity and concentration of inorganic nitrogen were significant predictors in differentiating the quality of the different sites of the lake. Principal component analysis (PCA) revealed that the relative abundance of each species order across sites was significantly influenced by changes in seasons and physicochemical parameters, and showed a weak association with the density of buffer vegetation at sites. Depending on the distance of oxbow areas to the parent channel, the combination of periodic flooding, riparian buffer and lake morphology define the degree of hydrological connectivity which in turn affects the composition and abundance of fish communities at different points of the lake.

INVERTEBRATES OF CONSERVATIVE INTEREST FROM PLATFORMA COTMEANA, A ROMANIAN NATURAL PROTECTED AREA

Current work was carried out in a Natura 2000 site of community importance, ROSCI 0354, Platforma Cotmeana, with a surface of 12.529 ha, located in the Central Southern part of Romania in a hilly area. The site is mainly dominated by broadleaf forest, from which 30% consists of beech species, an important habitat component for the studied species. Focal species of this research were: Lucanus cervus (Linnaeus, 1758), Cerambyx cerdo Linnaeus, 1758, and Morimus asper funereus Mulsant, 1862, as listed in the annex of EU Habitat Directive. For each species, numerical abundance, sex ratio, and other aspects of their biology were estimated. Habitat preference and the occurrence of individuals were recorded in order to evaluate their distribution in the site. Future perspectives on the status of the conservation of species in site were assessed by evaluation of human impact activities affecting the quality of their habitat. It was noted that most dominant species is L. cervus with an occurrence of 314 individuals, followed by M. asper funereus with 92 individuals, and C. cerdo with 41 individuals. An exoskeleton of Rosalia alpina (Linnaeus, 1758) was found, fact explained by the limit of species distribution area in the site.

A Preliminary Study on the Intense Pelagic and Benthic Mucilage Phenomenon Observed in the Sea of Marmara

In the intense mucilage formation observed in the Sea of Marmara in 2021, Phaeocystis pouchetii (Prymnesiophyceae) together with Skeletonema costatum, Cylindrotheca closterium, Thalassiosira rotula (Bacillariophyceae), and Gonyaulax fragilis (Dinophyceae) were detected in the foamy mucilage in the surface layer, and Chrysoreinhardia giraudii and Nematochrysopsis marina (Chrysophyceae), which are known to produce filamentous mucilage in benthic habitat. In addition, with the contribution of these groups, a higher cell abundance (2.1×107 cells/L) and chlorophyll-a value (15.9 µg/L) was reached than the mucilage event experienced in previous years. In the microscopic observations, typical dominant genera of the Sea of Marmara such as Protoperidinium and Tripos were observed very little in terms of species composition, and the fact that three previously unobserved species became dominant and the Cyanophyceae group was represented by different species indicated that phytoplankton composition changed in the mucilage formation in this period. The changing species composition with these 3 species that are known to make mucilage and which are new records for the Sea of Marmara point to the transportation by ship ballast waters or the inflow of brackish water with heavy rains. It is recommended to take the necessary measures to control domestic and industrial wastes and terrestrial inputs, which cause these species to reach numerical abundance and form mucilage, to carry out fisheries in a controlled manner, and to prevent the discharge of ship ballast waters and bilge waters.

Environmental influences on the cyanobacterial mat formation in the mangrove ecosystems along the southwest coast of India

AbstractMangrove forests are highly diverse niches playing fundamental roles in ecosystem sustainability, particularly in the tropics. Benthic realms in mangrove forest sustain a wide variety of autotrophs among which cyanobacteria forms a major component. The present study discusses the spatiotemporal variabilities in benthic cyanobacterial assemblage in selected mangrove ecosystems (Kannur—S1, Kochi—S2 and Kollam—S3 were sampled for 1 year, 2018 to 2019) along the south‐west coast of India. A total of nine cyanobacterial species belonging to six genera were identified, which included mainly non‐heterocystous forms like Oscillatoria irrigua, Phormidium chalybeum, Geitlerinema bigranulatum, Oscillatoria sancta, Spirulina major, Trichodesmium sp., whereas heterocystous cyanobacteria included Nostoc sp. Oscillatoria irrigua was the major species distributed in all the mangrove ecosystems. Temporal variations were observed in the distribution with pre‐monsoon (PRM) and monsoon (MON) seasons having higher numerical density and lesser diversity of benthic cyanophytes with lesser abundance and comparatively higher diversity during post‐monsoon (POM). Regionally, S2 observed higher numerical abundance with higher dominance, whereas S3 observed less abundance with high diversity. Physico‐chemical parameters of sediment and pore water analysis observed that sediment temperature positively correlated with cyanobacterial abundance, whereas a negative correlation was observed with dissolved oxygen and pore water dissolved nitrate. Pore water salinity also influenced the community composition of cyanobacteria with heterocystous cyanobacteria in comparatively less saline conditions. Hence, the study emphasis spatiotemporal variabilities in the benthic cyanobacterial assemblage of mangrove ecosystems in relation to environmental variables.

Raman Spectroscopy for the Analysis of Microplastics in Aquatic Systems.

Raman spectroscopy is gaining ground in the analysis of microplastics, especially due to its high spatial resolution that allows the investigation of small plastic particles, whose numeric abundance is argued to be particularly relevant in aquatic systems. Here, we aimed at outlining the status of Raman analysis of microplastics from aquatic systems, highlighting the advantages and the drawbacks of this technique and critically presenting tools and ways to effectively employ this instrument and to improve the spectra obtained and their interpretation. In particular, we summarized procedural information for the use of Raman spectroscopy, and we discussed issues linked to fluorescence interference and the analysis of weathered polymers, which may complicate the interpretation of Raman signatures. In this context, a deep understanding of the different plastic polymers and their Raman peaks and chemical fingerprints is fundamental to avoid misidentification. Therefore, we provided a catalog with detailed information about peaks of most common plastic polymers, and this represents, to the best of our knowledge, the first comprehensive resource that systematically synthesized plastic Raman peaks. Additionally, we focused on plastic additives, which are contained in the majority of plastics. These compounds are often intense in Raman scattering and may partly or completely overlie the actual material types, resulting in the identification of additives alone or misidentification issue. For these reasons, we also presented a new R package "RamanMP" that includes a database of 356 spectra (325 of which are additives). This will help to foster the use of this technique, which is becoming especially relevant in microplastic analysis.

Stochastic evaluation of benthic biocoenosis as pollution assessment tool in a perturbed aquatic ecosystem

To analyse the extent of disturbances and determine the state of health of aquatic systems, the integration of several biological effects at different levels of biological organization has been used. One of the most valuable methods of biological effect measurements is the use of ecological surveys at community and population levels. In this study, the distributional evaluation of benthic biocoenosis was undertaken to determine site-specific differences in community assemblage in relation to environmental status of the study sites. Three study locations (Okobaba, Iddo and Tin Can Island) in the western side of the Lagos Lagoon with highest concentrations of human activities were selected. These sites represent areas directly affected by major anthropogenic discharge into the Lagos Lagoon. Samples were collected for six consecutive months (March and August 2014). There was great variation in parameters investigated among the study sites. The concentrations of dissolved oxygen in surface water varied from 3.0- 4.5 mg/L. Chlorophyll a in surface water fluctuated from 0.12- 2.01 mg/L whereas, in sediment values varied from 0.14-1.32 mg/g. Biomass of microphytobenthos (MPB) varied from 1.4-13.2 g. Of the total 841 MPB cells collected the highest population was recorded in Okobaba. Twelve MPB taxa were recorded in the study area. The most important species in terms of numerical abundance was Oscillatoria sp. This organism occurred in all the study stations and recorded a total of 113 cells in the study stretch. A major feature of the population distribution of the MPB taxa in this study is the occurrence of higher number of cells at Okobaba. The number of individuals and the distribution of BMF taxa varied greatly from one study location to another. Of the total 801 individuals collected, 398 were recorded at Okobaba, 316 occurred at Tin Can Island and 18 at Iddo. Unlike the case of MPB organisms, a fewer number of BMF taxa were recorded in the study area. The most important MBF taxon in terms of numerical abundance was Pachymelania aurita. This organism occurred in all the study sites and recorded a total of 162 individuals thereby constituting 20% of the total MBF population collected. The benthic community observed in this study was characterized by low number of individuals and the species of MPB and MBF recorded are known opportunistic species common in stressed environments.

Fish size spectra are affected by nutrient concentration and relative abundance of non-native species across streams of the NE Iberian Peninsula

Aquatic ecosystems are strongly body-size structured with a decline of numerical abundance with increasing body size (hereafter, the size spectrum). Marine and lake fish studies have reported consistent variations of size spectra in relation to environmental conditions and biotic composition, but little is known about stream fishes. Accordingly, in this study we test several hypotheses about the effects of local water conditions, biotic introductions and cumulative pressures (measured as the IMPRESS index) on the fish size-spectrum slope (that is, the linear rate of decline of fish abundance as body size increase in a log-log scale) and the size-spectrum intercept (commonly used as proxy for carrying capacity) among 118 local fish assemblages in streams of the NE Iberian Peninsula. To our knowledge, this is the first time that an extensive river fish dataset is used in a dendritic network to cover systematic changes of size-spectrum parameters. We find that the slope and intercept of the fish size spectrum are negatively correlated with nutrient concentration (mainly total phosphorus), with a greater relative abundance of small fishes but a decline of overall carrying capacity. Moreover, fish assemblages with greater relative abundance of non-native species have flatter size-spectrum slopes. In contrast, the IMPRESS index and climate-related variables are poor predictors of the shape of the fish size spectra. This study contributes to better understanding of the main factors structuring fish assemblages in lotic environments of the Iberian Peninsula. We encourage more research on this line to further explore the use of fish size structure to evaluate the ecological health of riverine ecosystems.

Numerical abundance and biomass reveal different temporal trends of functional diversity change in tropical fish assemblages.

Understanding how the biodiversity of freshwater fish assemblages changes over time is an important challenge. Until recently most emphasis has been on taxonomic diversity, but it is now clear that measures of functional diversity (FD) can shed new light on the mechanisms that underpin this temporal change. Fish biologists use different currencies, such as numerical abundance and biomass, to measure the abundance of fish species. Nonetheless, because they are not necessarily equivalent, these alternative currencies have the potential to reveal different insights into trends of FD in natural assemblages. In this study, the authors asked how conclusions about temporal trends in FD are influenced by the way in which the abundance of species has been quantified. To do this, the authors computed two informative metrics, for each currency, for 16 freshwater fish assemblages in Trinidad's Northern Range that had been surveyed repeatedly over 5 years. The authors found that numerical abundance and biomass uncover different directional trends in these assemblages for each facet of FD, and as such inform hypotheses about the ways in which these systems are being restructured. On the basis of these results, the authors concluded that a combined approach, in which both currencies are used, contributes to our understanding of the ecological processes that are involved in biodiversity change in freshwater fish assemblages.