Distribution Of Benthic Invertebrates Research Articles

Temporal scales, sampling designs and age distributions in marine conservation palaeobiology

Abstract Conservation palaeobiology informs conservation and restoration of ecosystems by using the fossil record to discriminate between baseline and novel states and to assess ecosystem response to perturbations. Variability in the time-scale of palaeobiological data can generate patterns that either exaggerate or mute the magnitude of biotic changes. We identify two approaches that remedy the challenges associated with the mixing of baseline and post-impact states and with the transformation of the stratigraphic depth to time. First, combining surface death assemblages with both (1) fossil assemblages preserved in the subsurface historical layers and (2) living assemblages can better resolve the nature of ecosystem shifts than within-core surveys or live–dead analyses alone. Second, post-mortem age distributions of skeletal particles and their preservation states are not only informative about stratigraphic resolution and time averaging of death assemblages but also about the timing of changes in abundance of skeletal producers. High abundance of the youngest age cohorts in surface death assemblages is a null expectation of disintegration and burial dynamic. When this dynamic is accounted for, age distributions of benthic invertebrates from Holocene sediments often reveal high volatility, prolonged turn-offs in production or pervasive regime shifts that are obscured in the raw stratigraphic record.

Diversity and distribution of benthic invertebrates dwelling rivers of the Kruger National Park, South Africa

Meiobenthos (or meiofauna) are microscopic invertebrates that inhabit biofilms and interstitial spaces in rivers. They are diverse and extremely abundant, and they perform essential ecological functions by linking microbial production to higher trophic levels (e.g. macrobenthic invertebrates and fishes). However, meiobenthic communities remain poorly studied in Africa. Here, we sampled meio- and macrobenthic invertebrate communities associated with biofilms and sediments across an upstream–downstream gradient along the Olifants, Sabie and Crocodile rivers flowing through the Kruger National Park (KNP). We expected to link differences in community structure to environmental gradients as those rivers show different degrees of anthropogenic stress as they enter the park. Both meio- and macrobenthic communities differed across rivers and also structured along an upstream–downstream gradient. The upstream sites, which were the closest to the park borders, consistently showed a lower diversity in all three rivers. There, the invasive snail Tarebia granifera strongly dominated (making up 73% – 87% of the macrobenthos), crowding hard substrates, while concomitantly the abundances of biofilm-dwelling meiobenthos like nematodes and rotifers were substantially reduced. Nevertheless, the diversity and evenness of communities then tended to increase as water flowed downstream through the park, suggesting a beneficial effect of protected river reaches on benthic invertebrate diversity. However, for the Crocodile River, which makes up the southern border of the park, this trend was less conspicuous, suggesting that this river may experience the greatest threats. More generally, benthic invertebrate communities were driven by the concentrations of phosphates, sulphates, ammonium and organic matter and by substrate characteristics.Conservation implications: Meiobenthic organisms are very abundant in KNP rivers and react to environmental gradients; thus, they should be more considered for bio-monitoring or conservation of comprehensive assemblages of animals. Interestingly, protected reaches tended to show a reduced dominance of the invasive T. granifera and a higher diversity of benthic invertebrates.

Editorial: Biodiversity and Distribution of Benthic Invertebrates - From Taxonomy to Ecological Patterns and Global Processes

Biodiversity loss due to human activities is increasing worldwide at an alarming rate, and the oceans 15 are not an exception to this pattern (O´Hara et al., 2021). Loss of biodiversity weakens the ability of 16 ecosystems to function efficiently and can influence their capacity to provide vital goods and services 17 to humanity (Roe, 2019). We are still far away from a complete inventory of all habitats and life 18 forms harbored by Earth's oceans. With the exception of few charismatic (e.g., corals) or edible (e.g., 19 mussels or oysters) invertebrate species, most of the attention of the general public and scientific 20 community is focused on vertebrates. However, invertebrate phyla represent about 75 % of all 21 described species both in ocean and land (Eisenhauer and Hines, 2021). The marine benthic realm is 22 one of the largest and probably more diverse habitats on Earth, harboring a huge taxonomical and 23 functional diversity of invertebrates (Snelgrove, 1999). Unfortunately, knowledge about patterns of 24 biodiversity of benthic invertebrates is still very focused on the most accessible intertidal and shallow 25 subtidal domains; there is also a geographic bias because large areas of the planet remain almost 26 unexplored as well. 27The main objective of this special topic collection was to improve our knowledge in the above-28 described gaps about benthic invertebrate biodiversity. In this frame, 15 papers by 82

Geoenvironmental Implications and Biocenosis of Freshwater Lakes in the Arid Zone of East Kazakhstan

Steppe and semi-desert lakes of Central Asia represent unique and still poorly known aquatic ecosystems. The paper provides summaries of multi-proxy environmental and biological investigations of the previously unexplored ground of Sibe lakes in the naturally pristine zone of East Kazakhstan, and of their contributions to people. Data on the taxonomic composition of zooplankton and zoobenthos of these freshwater lacustrine basins are presented in terms of the species’ frequency of occurrence; the abundance of the aquatic biomass and the analyzed water geochemical variables insofar as they are dependent and correlative. The qualitative and quantitative records display variability in the biocenosis diversity due to the lakes’ geochemistry and hydrology differences—some lakes being oligotrophic and others being moderately trophic. In the latter case, the lakes characterized by an increased macrozoobenthos biomass are favourable for local ichthyofauna. Sapro-biological analysis reveals the predominance of β-saprobic species in the zooplankton composition pointing to slight or moderate pollution of surface waters due to natural biotic substances. This observation is in agreement with differences in the water quality of solitary lakes. The uneven distributions of benthic invertebrates (in terms of taxonomy and species populations) in the water bodies suggest specific hydro-ecological conditions that predetermine the structure of the lakes’ biocenosis. The littoral part of the lakes is characterized by the highest abundance of zooplankton and benthic fauna. The Sibe lakes are an example of an autonomous functioning of the lacustrine basins in the upland arid steppe zone, which is characterized by pronounced climate “continentality” and a high level of the sub-aquatic flora and fauna endemism. The present results are relevant to the understanding of the ecosystems’ dynamics and the modern anthropogenic impacts upon the pristine parkland-steppe landscapes of Central Asia, with implications for regional nature protection and sustainable eco-recreation.

Trawl fishing impacts on the status of seabed fauna in diverse regions of the globe

AbstractBottom trawl fishing is a controversial activity. It yields about a quarter of the world's wild seafood, but also has impacts on the marine environment. Recent advances have quantified and improved understanding of large‐scale impacts of trawling on the seabed. However, such information needs to be coupled with distributions of benthic invertebrates (benthos) to assess whether these populations are being sustained under current trawling regimes. This study collated data from 13 diverse regions of the globe spanning four continents. Within each region, we combined trawl intensity distributions and predicted abundance distributions of benthos groups with impact and recovery parameters for taxonomic classes in a risk assessment model to estimate benthos status. The exposure of 220 predicted benthos‐group distributions to trawling intensity (as swept area ratio) ranged between 0% and 210% (mean = 37%) of abundance. However, benthos status, an indicator of the depleted abundance under chronic trawling pressure as a proportion of untrawled state, ranged between 0.86 and 1 (mean = 0.99), with 78% of benthos groups > 0.95. Mean benthos status was lowest in regions of Europe and Africa, and for taxonomic classes Bivalvia and Gastropoda. Our results demonstrate that while spatial overlap studies can help infer general patterns of potential risk, actual risks cannot be evaluated without using an assessment model that incorporates trawl impact and recovery metrics. These quantitative outputs are essential for sustainability assessments, and together with reference points and thresholds, can help managers ensure use of the marine environment is sustainable under the ecosystem approach to management.

<p class="HeadingRunIn"><strong>Long-term macrobenthic community structure changes in the Upper Sakarya River System (1995–2015)</strong></p>

The Upper Sakarya River System (USRS) is one of the most important river systems in Turkey. Its primary drainage is provided by the Porsuk Seydi and Bardakçı Rivers and their tributaries. Long term benthic invertebrate community structure in the USRS was investigated from 1995–2015 (with sampling conducted every five years) in order to assess changes in their composition and in relation to water quality. Oligochaete specimens sorted from samples were identified to the species level when possible; all other invertebrate specimens sorted from samples were identified to order and family level. In addition, some environmental parameters (e.g., dissolved oxygen, temperature, and hydrogen ion concentration as pH) were measured in situ. Although Ephemeroptera-Plecoptera-Trichoptera fauna were the most abundant group in fauna of USRS during the years 1995, 2000 and (in part) 2005 (18.80, 17.69, and 14.07%, respectively), this ratio decreased to 7.90% during the more recent years of monitoring. In 1995, 2000 and 2005, Nais bretscheri, Chaetogaster diastrophus, Chaetogaster langi, Pristinella jenkinae, Aulodrilus pigueti, Aulodrilus pluriseta, Potamothrix hammoniensis, and Psammoryctides albicola were the dominant oligochaete taxa. After 2005, tubificine species became more prevalent in samples. While 6 stations had high BMWP (Biological Monitoring Working Party) value in 1995, 2000 and 2005, only 1 station had high value after 2005. Values of Shannon Diversity Indices ranged from 2.00 to 3.05 for the years 1995–2000, 1.87 to 2.24 for the years 2000–2005, 1.06 to 1.85 for the years 2005–2010, and 0.97 to 1.80 for the years 2010–2015. In USRS, while values of dissolved oxygen were measured as 8.00 mg/l and 9.00 mg/l in 1995 and 2000, this high value was measured only at one station in 2015. It was found that numerical and proportional distributions of benthic invertebrates in the USRS have changed considerably between 1995 and 2015. It is obvious that these changes are the result of anthropogenic habitat degradation.

Impact of water salinity on long-term dynamics and spatial distribution of benthic invertebrates in the Small Aral Sea

Abstract In 1996–2008, macrozoobenthos of the Small Aral Sea was investigated. A total of 320 macrozoobenthos samples were collected. Statistical analysis and statistical mapping were performed using Statistica and Photoshop software. Ten taxa of macrozoobenthos were identified, with an average water salinity of the Small Aral Sea ranging from 6.3 to 19.0 PSU. Average annual community abundance reached 1962 specimens m−2, with biomass of 107.1 g m−2. Quantitative variables of macrozoobenthos decreased by an order of magnitude by the end of the analyzed period. The polychaete Hediste diversicolor and mollusks Abra ovata, Cerastoderma glaucum, Caspiohydrobia sp. were the dominant taxa. Statistical mapping and correlation analysis revealed that the high biomass of A. ovata and Caspiohydrobia sp. occur in areas with high water salinity. Aggregations of the mollusk C. glaucum were observed in various areas of the sea. The polychaete H. diversicolor preferred areas with relatively low salinity. Analysis of the results showed that the optimum salinity gradient with Aral salt composition was 17–27 PSU for A. ovata, Caspiohydrobia sp. and C. glaucum, while 1–27 PSU for H. diversicolor. Along with changes in water salinity, the currently growing pressure from freshwater fish is an additional factor affecting the structure of benthic communities in the Small Aral Sea.

Simulating the distribution of Corbicula fluminea in Lake Taihu by benthic invertebrate biomass dynamic model (BIBDM)

Benthic invertebrates play important roles in aquatic ecosystems, and their distribution are significantly affected by substrate conditions, such as substrate type, particle size, and riverbed stability. Traditional research mainly uses statistical methods based on field observation to analyze the relationship between benthic invertebrate distribution and environmental factors, while lacking the consideration of growth process mechanism. Meanwhile, the effect of bed surface morphology on benthic invertebrate biomass has rarely been evaluated quantitatively for shallow lakes. This study newly develops a benthic invertebrate biomass dynamic model (BIBDM), which is coupled to hydrodynamic and bed surface morphology models, simultaneously considering the processes of growth, excretion, and predation. The ripple height, which represents bed surface morphology, is adopted as key parameter in the growth equation. The proposed model was applied to Lake Taihu, which is the third largest shallow lake in China. Corbicula fluminea, the largest biomass species of benthic invertebrates in Lake Taihu, was selected as the research object. The model performs well in reproducing the temporal biomass growth process, and the spatial simulation also shows good agreement with the observed data. Meanwhile, results confirm the importance of bed surface morphology on benthic invertebrates, with the correlation coefficient of 0.81 between the biomass and the ripple height. The proposed model could be used to evaluate the effect of environmental factors on the benthic invertebrate growth process. Moreover, the model is highly capable of applying to other species with corresponding environmental factor as the key parameter.

Freshwater release into estuarine wetlands changes the structure of benthic invertebrate assemblages: A case study from the Yellow River Delta

Freshwater releases to wetlands degraded by excessive soil salinity in estuarine areas have been widely used to restore vegetation and maintain biodiversity of the wetland ecosystems. However, freshwater release also alters the physical and chemical properties of the water body, having a profound impact on the ecology of restored wetland ecosystems. In this study, physical and chemical parameters of water quality were compared between restored and non-restored tidal wetlands after 10 years of freshwater release in the Yellow River estuary. In addition, benthic invertebrates were used as bioindicators to reveal the effects of freshwater release on estuarine wetland ecology. The results showed that there was a significant difference in salinity between restored and non-restored wetlands (P < 0.05), which led to differences in the composition of benthic invertebrate communities (ANOSIM P < 0.001). The primary components of benthic invertebrate community were insects in restored wetlands, and in non-restored tidal wetlands the primary components were annelids, crustaceans, and gastropods. More long-term monitoring research of the impacts of freshwater introduction on degraded estuarine wetland ecosystems is needed to fully assess consequences.

Biotypology of stream macroinvertebrates from North African and semi arid catchment: Oued Za (Morocco)

The aim of this study is to investigate the longitudinal zonation of macroinvertebrates assemblages in the Za River basin, the main tributary of Moulouya River (Morocco). This work carried out in three campaigns between March and August 2014 on 12 stations selected. This study allowed the identification of 137 species classified in 109 genera and 65 families. In addition to the physicochemical parameters measured three times in each station, a description of the aquatic environment was made to characterize each of the stations surveyed; in particular with regard to altitude, slope, Emberger quotient, thermal amplitude, kilometers at the source, current velocity and bioclimatic zones. The treatment of this benthic population as well as the stations environmental descriptors, using Foucart' factorial correspondence analysis (FCA) and partial triadic analysis (PTA) respectively, allowed for the development of a typology of this watercourse, where altitude and current speed seem to play a major role in the distribution of benthic invertebrates. The biocenotic study revealed the presence of three stationary groupings corresponding to four faunal groups.

Spatial variation of benthic invertebrates at the whole-ecosystem scale in a large eutrophic lake

The spatial distribution of benthic invertebrates is fundamental to the ecology of lakes and has implications for higher trophic levels and ecosystem processes. We conducted a lake-wide study of the spatial variation of benthic invertebrates in Lake Winnebago, Wisconsin (USA) with emphasis on the chironomid community. We asked: 1) What is the extent of spatial variation in benthic invertebrate community structure and abundance among and within major lake zones in the lake? 2) What factors are correlated with spatial variation of benthic invertebrates at multiple scales? 3) How has the chironomid community and the abundance of Chironomus varied temporally at the multidecadal scale in the lake? We collected benthic invertebrates from the profundal (33 sampling locations), offshore reef (17), and littoral (15) zones in August 2013. Profundal locations were sampled again in August 2014. Habitat variables, including water depth and temperature, Secchi depth, and benthic organic matter were measured with the goal of investigating potential causes of variation in the biota. The highest mean invertebrate densities occurred in the offshore reef and littoral zones (13,987 and 10,638 individuals [ind]/m2, respectively), relative to the profundal zone (2103 ind/m2). Zebra mussels were the numerically dominant taxon in both the littoral and offshore reef zones, whereas chironomids were the most abundant macroinvertebrates in the profundal. Large differences in chironomid community composition occurred among the 3 major zones. Within the profundal zone, the pattern of spatial variation in total chironomid abundance differed between the 2013 and 2014 sampling events. Local factors (e.g., sediment characteristics) and stochastic factors (e.g., wind and current speed) probably interact to influence the spatial distribution of chironomid taxa between and within zones in large shallow lakes, such as Lake Winnebago.

Substantial changes in the depth distributions of benthic invertebrates in the eastern Kattegat since the 1880s.

Bottom trawling and eutrophication are well known for their impacts on the marine benthic environment in the last decades. Evaluating the effects of these pressures is often restricted to contemporary benthic data, limiting the potential to observe change from an earlier (preimpact) state. In this study, we compared benthic species records from 1884 to 1886 by CGJ Petersen with recent data to investigate how benthic invertebrate species in the eastern Kattegat have changed since preimpact time. The study shows that species turnover between old and recent times was high, ca. 50%, and the species richness in the investigation area was either unchanged or higher in recent times, suggesting no net loss of species. Elements of metacommunity structure analysis of datasets from the 1880s, 1990s, and 2000s revealed a clear change in the depth distribution structure since the 1880s. The system changed from a Quasi‐nested/Random pattern unrelated to depth in the 1880s with many species depth ranges over a major part of the studied depth interval, to a Clementsian pattern in recent times strongly positively correlated with depth. Around 30% of the 117 species recorded both in old and in recent times, including most trawling‐sensitive species, that is large, semiemergent species, showed a decrease in maximal depth of occurrence from the deeper zone fished today to the shallower unfished zone, with on average 20 m. Concurrently, the species category remaining in the fished zone was dominated by species less sensitive to bottom trawling like infauna polychaetes and small‐sized Peracarida crustaceans, most likely with short longevity. The depth interval and magnitude of the changes in depth distribution and the changes in species composition indicate impacts from bottom trawling rather than eutrophication. Furthermore, the high similarity of results from the recent datasets 10 years apart suggests chronic impact keeping the system in an altered state.

Spatial distribution, fractionation, toxicity and risk assessment of surface sediments from the Baiyangdian Lake in northern China

The pollution of Baiyangdian Lake (BYDL) has been of concern since the Xiongan New Area was established. To conduct ecological restoration of BYDL, the heavy metals (HMs) levels in sediments were assessed. Specifically, Surface sediments (0–10 cm) samples in BYDL were analyzed for Cd, Cr, Cu, Ni, Pb and Zn in October 2016 to evaluate the risk posed by trace metals, as well as their bioavailability and toxicity. The results demonstrated that HMs showed high pollution and risk levels in most sample sites as a result of Cd and Pb. Metals speciation analysis demonstrated that Cd, Cu, Pb and Zn were dominated by non-residual fractions that originated from anthropogenic sources and presented higher bioavailability. The risk assessment code indicated that Cd poses a medium level biological risk in BYDL, which reached 10.25% and 29.38%. The bioavailable metals index showed a strong correlation with acute toxicity (R2 = 0.704), indicating bioavailable metals are an important reason for sediment acute toxicity. Canonical correspondence analysis demonstrated that HMs have a coercive effect on the distribution of benthic invertebrates. Overall, the results indicate that HMs pollution should be considered during the development of strategies for ecological restoration in BYDL.

Taxonomic diversity of benthic invertebrates of the Moskva River in the Moscow area: diversity and distribution

&lt;p&gt;Biological diversity and distribution of benthic invertebrates in the Moskva River within the frames of Moscow are studied. Totally, 72 invertebrate taxa were found including 8 invasive species with amphipod &lt;em&gt;Gmelinoides fasciatus &lt;/em&gt;(Stebbing, 1899), an invader from the Lake Baikal. A number of observed species are characterized with high abundance and biomass while most of observed taxa are represented by a small number of individuals. The greatest species diversity was revealed for insect larvae, mainly due to Chironomidae. The main species on the investigated section of the river are various crustaceans, mainly amphipods and decapods (when present in samples) showing more than 70-90% of all biomass of zoobenthos at all stations (sites). Multivariate cluster analysis allowed concluding that bottom communities in Moskva River, the degree of their quantitative development, species richness and diversity are mainly influenced by the structure of bottom substrates rather than other factors. The most diverse benthic communities are presented on silty bottom with mixture of shells of mollusks and plant remains. The lowest diversity of benthic communities is characteristic for sites with relatively strong water and well washed sand as the main bottom substrate. Obtained data starts annual monitoring of the river at indicated stations using biological indicators, namely native amphipod &lt;em&gt;Gammarus lacustris&lt;/em&gt; and invasive &lt;em&gt;G. fasciatus&lt;/em&gt;.&lt;/p&gt;

Biotic diversity of benthic macroinvertebrates at contrasting glacier-fed systems in Patagonia Mountains: The role of environmental heterogeneity facing global warming

Patagonia is by far the largest glacierized area in South America. However, little is known about ecology, functioning and biodiversity of glacier-fed streams facing global warming. We investigated changes in environmental features and macroinvertebrate communities along a longitudinal gradient of glacier influence of two Patagonian systems that differ in glacier cover magnitude and the spatial sequence of lotic and lentic phases. Both glaciers, Torrecillas (~5.5km2, Torrecillas system) and Cónico (~0.44km2, Baggilt system), are retreating. Longitudinal distribution of benthic invertebrates partially fitted to predictions for glacierized temperate systems, with Diamesinae spp. dominating at closest sites to the Cónico, and Orthocladiinae increasing downstream, but patterns were unclear at Torrecillas. Generalized Linear Model identified chlorophyll a and conductivity as having significant effect on richness and density respectively at Torrecillas; detritus biomass and gravel influenced species richness, and boulder percentage and water temperature affected density, at Baggilt. Canonical Correspondence Analyses integrating benthic biota and environmental variables revealed that a higher environmental heterogeneity at Baggilt, related with spatial dimension (unshaded/shaded reaches, wetland reaches), local resources (detritus, bryophytes) and temperature, probably explained the unexpected high richness in benthic assemblages (67 taxa). Environmental conditions imposed by the lake outlet (proglacial) at Torrecillas resulted in a less diverse community (31 taxa). Finally our results suggest that these isolated, small glacier-fed streams typical of the Patagonian landscape appear highly vulnerable to global warming. Endemic elements could disappear at upper segments being replaced by other species common at rhithral environments, which might increase local diversity (alfa diversity) but decrease regional diversity (gamma diversity). From an ecosystem perspective stream functioning can result altered. Glacier retreating or disappearing threatens major ecosystem services for Patagonian inhabitants such as water supply, hydrological regulation, recreation and tourism.

Process-driven and biological characterisation and mapping of seabed habitats sensitive to trawling.

The increase of anthropogenic pressures on the marine environment together with the necessity of a sustainable management of marine living resources have underlined the need to map and model coastal environments, particularly for the purposes of spatial planning and for the implementation of integrated ecosystem-based management approach. The present study compares outputs of a process-driven benthic habitat sensitivity (PDS) model to the structure, composition and distribution of benthic invertebrates in the Eastern English Channel and southern part of the North Sea. Trawl disturbance indicators (TDI) computed from species biological traits and benthic community composition were produced from samples collected with a bottom trawl. The TDI was found to be highly correlated to the PDS further validating the latter’s purpose to identify natural process-driven pattern of sensitivity. PDS was found to reflect an environmental potential that may no longer be fully observable in the field and difference with in situ biological observations could be partially explained by the spatial distribution of fishery pressure on the seafloor. The management implication of these findings are discussed and we suggest that, used in conjunction with TDI approaches, PDS may help monitor management effort by evaluating the difference between the current state and the presumed optimal environmental status of marine benthic habitats.

Building a database for long-term monitoring of benthic macrofauna in the Pertuis-Charentais (2004-2014).

BackgroundLong-term benthic monitoring is rewarding in terms of science, but labour-intensive, whether in the field, the laboratory, or behind the computer. Building and managing databases require multiple skills, including consistency over time as well as organisation via a systematic approach. Here, we introduce and share our spatially explicit benthic database, comprising 11 years of benthic data. It is the result of intensive benthic sampling that has been conducted on a regular grid (259 stations) covering the intertidal mudflats of the Pertuis-Charentais (Marennes-Oléron Bay and Aiguillon Bay). Samples were taken by foot or by boats during winter depending on tidal height, from December 2003 to February 2014. The present dataset includes abundances and biomass densities of all mollusc species of the study regions and principal polychaetes as well as their length, accessibility to shorebirds, energy content and shell mass when appropriate and available. This database has supported many studies dealing with the spatial distribution of benthic invertebrates and temporal variations in food resources for shorebird species as well as latitudinal comparisons with other databases. In this paper, we introduce our benthos monitoring, share our data, and present a "guide of good practices" for building, cleaning and using it efficiently, providing examples of results with associated R code.New informationThe dataset has been formatted into a geo-referenced relational database, using PostgreSQL open-source DBMS. We provide density information, measurements, energy content and accessibility of thirteen bivalve, nine gastropod and two polychaete taxa (a total of 66,620 individuals)​ for 11 consecutive winters. Figures and maps are provided to describe how the dataset was built, cleaned, and how it can be used. This dataset can again support studies concerning spatial and temporal variations in species abundance, interspecific interactions as well as evaluations of the availability of food resources for small- and medium size shorebirds and, potentially, conservation and impact assessment studies.

Benthic invertebrates nestedness in flood and drought periods in a Neotropical floodplain: looking for the richest environments

Abstract Aim Floodplains are among the most biologically diverse systems in the world, where hydrological regime is recognized as crucial to structure aquatic communities. We predicted that i) structure of benthic metacommunity is nested in the drought and random in the flood season in a Neotropical floodplain. We expected to find ii) environmental homogenization during the flood season which may disrupt the nested pattern. Moreover, we identified habitats of high taxa richness of benthic invertebrates and characterized them by habitat type and fluvial systems. Methods We sampled benthic invertebrates from 36 habitats in the Upper Paraná River floodplain. We tested nestedness using NODF index and evaluated the environmental variability using the multivariate homogeneity of group dispersions (PERMDISP), separately for flood and drought periods. Results The environmental variability was lower during the flood. We found a nested distribution among benthic invertebrates in both flood and drought periods. The highest species richness values were recorded in small and unconnected lakes from Paraná fluvial system and some rivers and secondary channels, independent of the fluvial system. Chironomidae, Oligochaeta and Ostracoda were the most frequent taxa and were recorded in all habitats. Conclusion The nested distribution of benthic invertebrates is a consistent pattern for this metacommunity because its distribution was not disrupted by floods that homogenize limnological conditions and increase the connectivity among habitats. We also found that habitats with high taxa richness were both lotic and lentic in the three fluvial systems. Our findings emphasize that different habitats in different subsystems sustains the richness of the benthic invertebrates metacommunity in the Upper Paraná River floodplain over time.

Assessment of the structural role of sedimentary links on the spatial distribution of periphyton and fish in a Canadian Shield river

The Link Discontinuity Concept suggests that sediment recruitment zones, or points, create a series of sedimentary links that may determine the structure of physical and biological components of rivers. Although several studies support the role of sedimentary links on the distribution of benthic invertebrates in rivers, their effects on the distribution of periphyton and fish remain unknown. The purpose of our study was to assess the relationships between the biomass of periphyton, the density of Atlantic salmon parr, and the structure of a series of sedimentary links in a Canadian Shield river during the summers of 2004, and 2005. Periphyton biomass was estimated using a tactile approach. Parr density was estimated visually by underwater observations. Our results suggest that the biomass of periphyton is not determined by sedimentary links. However, sedimentary links play a structuring role on the spatial distribution of parr at the scale of the complete river. This role appears to be mainly, but not strictly driven by the association between parr and boulders (which may improve parr sheltering and feeding habitats).

Diversity and Distribution of Benthic Invertebrates in the West Port, Malaysia

Diversity and Distribution of Benthic Invertebrates in the West Port, Malaysia