Distribution Of Benthic Species Research Articles

Structure of the Bottom Boundary Current South of Iceland and Spreading of Deep Waters by Submesoscale Processes

AbstractThe northeastern part of the North Atlantic subpolar gyre is a key passage for the Atlantic Meridional Overturning Circulation upper cell. To this day, the precise pathway and intensity of bottom currents in this area is not clear. In this study, we make use of regional high resolution numerical modeling to suggest that the main bottom current flowing south of Iceland originates from both the Faroe‐Banks Channel and the Iceland‐Faroe Ridge and then flows along the topographic slope. When flowing over the rough topography, this bottom current generates a 200 m large bottom mixed layer. We further demonstrate that many submesoscale structures are generated at the southernmost tip of the Icelandic shelf, which subsequently spread water masses in the Iceland Basin. These findings have major implication for the understanding of the water masses transport in the North Atlantic, and also for the distribution of benthic species along the Icelandic shelf.

Benthic Foraminifera from the Lower Miocene Sediments of Murachbann, Western Kachchh, Gujarat, India: Implications for Inferring Palaeoenvironment

A thorough taxonomic study was carried out for the first time using high-resolution microscopy from Neogene sections of western Kachchh, India. In the present study, 25 species of benthic foraminifera belonging to 3 classes viz. Globothalamea, Tubothalamea, Nodosariata and 4 orders Rotaliida, Textulariida, Miliolida and Polytmorphinida have been identified from limestone and silty-claystone of Murachbann section belonging to lower Miocene. This taxonomic study provides the distribution of benthic foraminifera species from Murachbann section. The attempt is made to interpret depositional palaeoenvironment based on this distribution of the studied foraminifera. Keywords: Morphology, Taxonomy, Benthic Foraminifera, Limestone, Palaeoenvironment, Chhasra Formation

Taxonomy and abundance of epibenthic Prorocentrum (Dinophyceae) species from the tropical and subtropical Southwest Atlantic Ocean including a review of their global diversity and distribution

In the tropical and subtropical South Atlantic Ocean, studies on the taxonomy and abundance of benthic harmful algae are scarce and the region has been largely under investigated. In this study, morphological descriptions, molecular (LSU rDNA and ITS region) and abundance data of benthic Prorocentrum species from the tropical and subtropical Southwest Atlantic and three oceanic islands are presented. Moreover, a review of global benthic Prorocentrum species richness and distribution is presented. Eleven benthic Prorocentrum species were found in Brazil. Morphological and molecular data on P. borbonicum, P. hoffmannianum, P. lima species complex and P. rhathymum were provided. Prorocentrum panamense, P. cf. caipirignum, P. cf. concavum, P. cf. norrisianum, P. emarginatum/fukuyoi/sculptile complex and two not identified species were observed using scanning electron and/or light microscopy, and morphological descriptions are presented. Prorocentrum lima species complex was found at all investigated sites, in abundances up to 2 × 104 cells g−1 FW at the Northeast Brazil, while maximum abundance of all the remaining species did not exceed 1 × 103 cells g−1 FW. The Fernando de Noronha archipelago can be considered a hotspot of benthic Prorocentrum species diversity, with ten species registered. Data compiled in the literature review shows a clear latitudinal gradient with higher species richness in tropical and subtropical regions relative to temperate areas. It is also evident that there is a bias caused by taxonomic impediment and an uneven sampling effort, with many regions still to be investigated using a combined morphological and molecular effort. Therefore, the current knowledge on the global distribution of benthic Prorocentrum species is likely underestimated.

Spatiotemporal variability of oxygen concentration in coral reefs of Gorgona Island (Eastern Tropical Pacific) and its effect on the coral Pocillopora capitata.

Dissolved oxygen concentration (DO) is one of the main factors limiting benthic species distribution. Due to ocean warming and eutrophication, the ocean is deoxygenating. In the Eastern Tropical Pacific (ETP), deep waters with low DO (<1 mg L-1) may reach coral reefs, because upwelling will likely intensify due to climate change. To understand oxygen variability and its effects on corals, we characterize the Spatio-temporal changes of DO in coral reefs of Gorgona Island and calculate the critical oxygen tension (P crit) to identify the DO concentration that could represent a hypoxic condition for Pocillopora capitata, one of the main reef-building species in the ETP. The mean (±SD) DO concentration in the coral reefs of Gorgona Island was 4.6 ± 0.89 mg L-1. Low DO conditions were due to upwelling, but hypoxia (<3.71 mg L-1, defined as a DO value 1 SD lower than the Mean) down to 3.0 mg O2 L-1 sporadically occurred at 10 m depth. The P crit of P. capitata was 3.7 mg L-1 and lies close to the hypoxic condition recorded on coral reefs during the upwelling season at 10 m depth. At Gorgona Island oxygen conditions lower than 2.3 mg L-1 occur at >20 m depth and coincide with the deepest bathymetric distribution of scattered colonies of Pocillopora. Because DO concentrations in coral reefs of Gorgona Island were comparably low to other coral reefs in the Eastern Tropical Pacific, and the hypoxic threshold of P. capitata was close to the minimum DO record on reefs, hypoxic events could represent a threat if conditions that promote eutrophication (and consequently hypoxia) increase.

A Taxonomic Baseline to Monitor Retreating Arctic Biota: The Marine Invertebrate Collection of the Icelandic Institute of Natural History (IINH)

The IINH collection comprises ~5.3 million specimens of marine invertebrates, collected within 758,000 km2 of the 200-mile Exclusive Economic Zone (EEZ) of Iceland, which is a significant part of the greater Arctic-Boreal biogeographic boundary in the northern Atlantic. The oldest collected specimen is from 1871, but most of the specimens (4.7 million) were collected during the BIOICE project between 1991 and 2004. The program objective is to build a museum collection, reflecting the geographical distribution and morphological variation of benthic species. Over 1,390 zoological samples were collected following a stratified random sampling plan with 579 stations at a depth range of 20 to 3,000 m, and temperatures from −1°C to over +9°C. The material is sorted to about 50 higher taxonomic groups, and 3,007 benthic species, of which fifty-one are new to science. The collection offers a baseline to monitor changing biodiversity at the Arctic-Boreal boundary, with rising temperature, salinity, and acidification.

Ostreopsis spp.: Morphology, proliferation and toxic profile in the North-West of Agadir (North Atlantic Ocean).

The distribution of benthic Ostreopsis species is poorly known in the Moroccan coasts. The current study is aiming to investigate: i) the distribution of Ostreopsis spp. cells on macroalgae and in the seawater column of the Cape Ghir area (North-West of Agadir) during the summer season of Ostreopsis from July 15 to November 17, 2020; ii) the toxic profile at the level of the three matrices (benthic Ostreopsis attached to macroalgae, Ostreopsis in the water column and mussels) via chemical analysis using mass spectrometry. A taxonomic study of Ostreopsis spp. was carried out using the light and inverted optical microscopes. Chemical analysis showed the presence of ovatoxins (OvTX-A and OvTX-B) in Ostreopsis samples in low quantities, in the order of fg.cell −1 and at levels below the limit of quantification (0.04 μg.mL −1) in mussels. Morphological observations showed that the cells were ovoid and flattened, large, and ventrally pointed with a dorsoventral diameter (DV) and width (W) of 57-84μm and 33-52μm, respectively, and a dorsoventral/anteroposterior diameter (DV/AP) of about 3.23.

Disentangling trawling impact from natural variability on benthic communities

Various environmental parameters such as temperature, depth and currents influence the composition and distribution of benthic assemblages. However, the impact of trawling on benthic communities depends on their species composition since not all benthic species are equally sensitive to trawling. Moreover, trawling can have effects on benthic species similar to some natural disturbances, such as a local increase in turbidity. Thus, species adapted to these natural disturbances may be resistant to a certain level of trawling. This study evaluates the joint influence of environmental parameters and trawling pressure on four functional sensitivity indices in three environmentally contrasted areas: the English Channel, the Gulf of Lion and the eastern coast of Corsica, the two latter being located in the Mediterranean Sea. The different environmental parameters influencing the behaviour of these indices were identified in each of the study areas. These parameters were divided into two groups according to the type of influence they have on the benthic community. The first group of variables, used for modeling “Scope for Growth” (SfG), relates to the resilience of species, while the second, “Disturbance” (Dist), concerns their resistance to physical impacts. This work highlighted that the distribution of benthic species in the English Channel is mainly linked to physical disturbances and therefore to their resistance, whereas it is mainly parameters linked to the resilience of communities that influence the distribution of benthic fauna in the Mediterranean. The effect of abrasion could be distinguished from the natural environmental disturbances in the English Channel and Gulf of Lion where trawling was found to have a significant effect on functional sensitivity indices. The composition and distribution of benthic communities in Corsica, did not seem to be influenced by trawling pressure.

DISTRIBUTION OF BENTHIC FORAMINIFERA IN THE CORAL REEFS ECOSYSTEM OF PULAU BIDONG, TERENGGANU, SOUTHERN SOUTH CHINA SEA

A study on the distribution of benthic foraminiferal species in the surface sediments of coral reefs was carried out in Pulau Bidong in the southern South China Sea (SCS). Samples were collected at 12 sites around Pulau Bidong at water depths ranging from 5 m to 30 m. Live (rose bengal stained) and optimally preserved empty tests of benthic foraminifera were analysed based on their chamber and apertural characteristics observed under binocular microscope (Leica Zoom 2000). The results revealed that 32 genera of benthic foraminifera were found in the coral reefs sediments. Amphistegina was the most abundant genus with relative abundance of 68% and frequently recorded at depths of between 10-15 m and 25-30 m. Other common genera that were found were Calcarina, Elphidium, Heterolepa, Heterostegina, Quinqueloculina, Peneroplis and Triloculina. These genera showed depth distribution preference in the shallow water zone (5 m depth). The highest diversity index (2.3) and number of taxa (26 genera) were recorded at station W2, located at the western part of Pulau Bidong. The lowest diversity index (0.2) and number of taxa (seven genera) were recorded at station S3, located at the southern part of Pulau Bidong. The frequency distribution and diversity of benthic foraminifera in the study area were related to water depth.

Local fishers experience can contribute to a better knowledge of marine resources in the Western Mediterranean Sea

In this study we explore fishers’ perceptions in the Ebro Delta area, Western Mediterranean, throughout structured questionnaires. Specifically, we compare the coherence of information provided by fishers with those resulting by scientific studies in terms of the status of demersal marine resources in the Ebro Delta area; we describe temporal trends of demersal key species in the area with fishers’ perceptions; and we explore the use of Local Ecological Knowledge (LEK) as an alternative data sources to reduce the gap of knowledge on the spatial distribution and temporal trends of sensitive and vulnerable benthic marine species. Our results document important changes in the bottom trawling activity in the study area and in the abundance of commercial species with time according to fishers’ perceptions. Our results mostly match quantitative information from national statistics and stock assessment analyses. In addition, we document important changes in the presence of Vulnerable Marine Ecosystems (VMEs) in the study area due to the by-catch of habitat forming species with time. According to fishers’ perceptions, habitat forming species occur in the area, but were more frequently captured incidentally in the 1980 s and 1990 s. Overall, our study evidences that fisher’s perception represents an important source of complementary information to describe bottom trawling fisheries characteristics and the long-term changes of demersal target species in the Western Mediterranean Sea. Moreover, it highlights that LEK can provide fundamental and additional information on ecosystem changes and it can be a useful tool to increase the knowledge on spatial distribution and on temporal trends of vulnerable benthic species.

The geomorphology of an ebb-tidal-delta linked to benthic species distribution and functionality

As a response to climate change and sea-level rise, new nourishment strategies for low-lying sandy coasts are developed. These interventions affect the habitat quality of coastal ecosystems for benthic communities. Unraveling the relationship between benthic fauna and their environment facilitates the design of sustainable management strategies for the coastal ecosystem. At the ebb-tidal delta of Ameland, The Netherlands, a unique dataset of 166 benthic and sediment samples is collected and allowed for an investigation of the macrobenthic fauna distribution at the spatial scale of morphological features. The benthic community at the ebb tidal delta is composed of species capable of withstanding the dynamic nature of these sandy coastal ecosystems. Despite the dynamic environment, the geomorphology of the ebb-tidal delta is reflected in the benthic species distribution. Distinct species assemblages were identified, covering a gradient of physical stress from extremely exposed to waves or currents, to relatively low energetic environments such as found on the delta plane seaward of the ebb-tidal delta terminal lobe. This gradient is reflected in the median grain size, organic matter content, and oxygenation of the sediment. A second gradient distinguishes well-sorted, mainly wave-exposed sediments from less well-sorted, mainly current-exposed sites. The functional characteristics of the benthic fauna show a clear contrast between the three most exposed, and the three most sheltered assemblages. Small, short-lived, surface deposit-feeding, highly mobile, burrowing organisms dominate in the most exposed sites, whereas with increasing shelter also larger, long-lived, filter-feeding and sessile organisms become more dominant. The functional characteristics suggest that the fauna of the most exposed sites will likely show a fast recovery of disturbance by sand nourishments. A much longer-lasting effect can be expected on sheltered parts of the ebb-tidal delta.

Shifts in Estuarine Macroinvertebrate Communities Associated With Water Quality and Climate Change

The present work aims to identify changes in the macroinvertebrate community of the Tagus estuary (Portugal) due to improvements in water quality and to climate change. Data was collected over a period of 16 years (1998–2014) from different sites located along the estuarine gradient. The AZTI Marine Biotic Index (AMBI) was used to assess the ecological quality status based on benthic invertebrate communities and identify possible variations associated with changes in water quality. The overall distribution of each species was examined to detect possible changes associated with climate, based on species’ affinity for more temperate or subtropical climates. Results demonstrate that there was an overall improvement of AMBI scores during the assessment period. The analysis of the geographical distribution of benthic species seems to indicate that there has been an increase of species which prefer subtropical climates in the shallower waters of the estuary, whereas in the deeper estuarine sections the propensity is for species that prefer temperate climates.

Development of benthic macroinvertebrate species distribution models using the Bayesian optimization

Development of benthic macroinvertebrate species distribution models using the Bayesian optimization

Measurements of hydrodynamics, sediment, morphology and benthos on Ameland ebb-tidal delta and lower shoreface

Abstract. A large-scale field campaign was carried out on the ebb-tidal delta (ETD) of Ameland Inlet, a basin of the Wadden Sea in the Netherlands, as well as on three transects along the Dutch lower shoreface. The data have been obtained over the years 2017–2018. The most intensive campaign at the ETD of Ameland Inlet was in September 2017. With this campaign, as part of KustGenese2.0 (Coastal Genesis 2.0) and SEAWAD, we aim to gain new knowledge on the processes driving sediment transport and benthic species distribution in such a dynamic environment. These new insights will ultimately help the development of optimal strategies to nourish the Dutch coastal zone in order to prevent coastal erosion and keep up with sea level rise. The dataset obtained from the field campaign consists of (i) single- and multi-beam bathymetry; (ii) pressure, water velocity, wave statistics, turbidity, conductivity, temperature, and bedform morphology on the shoal; (iii) pressure and velocity at six back-barrier locations; (iv) bed composition and macrobenthic species from box cores and vibrocores; (v) discharge measurements through the inlet; (vi) depth and velocity from X-band radar; and (vii) meteorological data. The combination of all these measurements at the same time makes this dataset unique and enables us to investigate the interactions between sediment transport, hydrodynamics, morphology and the benthic ecosystem in more detail. The data provide opportunities to calibrate numerical models to a high level of detail. Furthermore, the open-source datasets can be used for system comparison studies. The data are publicly available at 4TU Centre for Research Data at https://doi.org/10.4121/collection:seawad (Delft University of Technology et al., 2019) and https://doi.org/10.4121/collection:kustgenese2 (Rijkswaterstaat and Deltares, 2019). The datasets are published in netCDF format and follow conventions for CF (Climate and Forecast) metadata. The http://data.4tu.nl (last access: 11 November 2020) site provides keyword searching options and maps with the geographical position of the data.

Developing the use of convolutional neural networking in benthic habitat classification and species distribution modelling

Abstract Management of the marine environment is increasingly being conducted in accordance with an ecosystem-based approach, which requires an integrated approach to monitoring. Simultaneous acquisition of the different data types needed is often difficult, largely due to specific gear requirements (grabs, trawls, and video and acoustic approaches) and mismatches in their spatial and temporal scales. We present an example to resolve this using a convolutional neural network (CNN), using ad hoc multibeam data collected during multi-disciplinary surveys to predict the distribution of seabed habitats across the western English Channel. We adopted a habitat classification system, based on seabed morphology and sediment dynamics, and trained a CNN to label images generated from the multibeam data. The probability of the correct classification by the CNN varied per habitat, with accuracy above 60% for 85% of habitats in a training dataset. Statistical testing revealed that the spatial distribution of 57 of the 100 demersal fish and shellfish species sampled across the region during the surveys possessed a non-random relationship with the multibeam-derived habitats using CNN. CNNs, therefore, offer the potential to aid habitat mapping and facilitate species distribution modelling at the large spatial scales required under an ecosystem-based management framework.

Unraveling the effects of environmental drivers and spatial structure on benthic species distribution patterns in Eurasian-Arctic seas (Barents, Kara and Laptev Seas)

In times of accelerating climate change, species are challenged to respond to rapidly shifting environmental settings. Yet, faunal distribution and composition are still scarcely known for remote and little explored seas, where observations are limited in number and mostly refer to local scales. Here, we present the first comprehensive study on Eurasian-Arctic macrobenthos that aims to unravel the relative influence of distinct spatial scales and environmental factors in determining their large-scale distribution and composition patterns. To consider the spatial structure of benthic distribution patterns in response to environmental forcing, we applied Moran’s eigenvector mapping (MEM) on a large dataset of 341 samples from the Barents, Kara and Laptev Seas taken between 1991 and 2014, with a total of 403 macrobenthic taxa (species or genera) that were present in ≥ 10 samples. MEM analysis revealed three spatial scales describing patterns within or beyond single seas (broad: ≥ 400 km, meso: 100–400 km, and small: ≤ 100 km). Each scale is associated with a characteristic benthic fauna and environmental drivers (broad: apparent oxygen utilization and phosphate, meso: distance-to-shoreline and temperature, small: organic carbon flux and distance-to-shoreline). Our results suggest that different environmental factors determine the variation of Eurasian-Arctic benthic community composition within the spatial scales considered and highlight the importance of considering the diverse spatial structure of species communities in marine ecosystems. This multiple-scale approach facilitates an enhanced understanding of the impact of climate-driven environmental changes that is necessary for developing appropriate management strategies for the conservation and sustainable utilization of Arctic marine systems.

Flooding affects vertical displacement of intertidal macrofauna: A proxy for the potential impacts of environmental changes on sandy beaches

In the context of global environmental changes, sea level rise is expected to cause long-term floods in upper zones of sandy beaches, while increased rainfall may intensify freshwater floods with extreme salinity reductions. However, the effects of these changes on benthic macrofauna behavior, especially the species vertical displacement, remain largely overlooked in sandy beach ecology. Here, we used natural and manipulative experiments to evaluate whether the predicted effects of saltwater and freshwater floods would affect the distribution of beach macrofauna within the sediment column (i.e. vertical distribution). We first tested the effects of natural tidal flooding by analyzing the upper beach macrofauna at different depths within the sediment column during low and high tide periods. Then, we simulated saltwater and freshwater floods in manipulative experiments to examine their effects on the vertical distribution of the semiterrestrial crustacean Excirolana armata within the sediment. We observed that the macrofauna was concentrated closer to the sediment surface layer during low tide and in deeper areas during high tide. We also found that both saltwater and freshwater floods induced a movement of E. armata towards deeper layers of the sediment; yet this effect was dependent on salinity given that fewer individuals reached deeper sediment layers during freshwater floods. Overall, our results show that floods induce movements of sandy beach macrofauna within the sediment column, thereby changing the vertical distribution of benthic species. It is possible that these changes may affect ecological processes and services provided by sandy beach biodiversity such as bioturbation, biomass production and the flux of energy. In this regard, we suggest that future studies focus on the understanding of behavioral responses of macrofauna as a proxy for the impacts of global environmental changes, attempting to upscale their ecological consequences from the short to long-term effects.

Selecting environmental descriptors is critical for modelling the distribution of Antarctic benthic species

Species distribution models (SDMs) are increasingly used in ecological and biogeographic studies by Antarctic biologists, including for conservation and management purposes. During the modelling process, model calibration is a critical step to ensure model reliability and robustness, especially in the case of SDMs, for which the number of selected environmental descriptors and their collinearity is a recurring issue. Boosted regression trees (BRT) was previously considered as one of the best modelling approach to correct for this type of bias. In the present study, we test the performance of BRT in modelling the distribution of Southern Ocean species using different numbers of environmental descriptors, either collinear or not. Models are generated for six sea star species with contrasting ecological niches and wide distribution ranges over the entire Southern Ocean. For the six studied species, overall modelling performance is not affected by the number of environmental descriptors used to generate models, BRT using the most informative descriptors and minimizing model overfitting. However, removing collinear descriptors also helps reduce model overfitting. Our results confirm that BRTs may perform well and are relevant to deal with complex and redundant environmental information for Antarctic biodiversity distribution studies. Selecting a limited number of non-collinear descriptors before modelling may generate simpler models and facilitate their interpretation. The modelled distributions do not differ noticeably between the different species despite contrasting species ecological niches. This unexpected result stresses important limitations in using SDMs for broad scale spatial studies, based on limited, spatially aggregated data, and low-resolution descriptors.

Littoral Benthic Communities Under Effect of Heat Wave and Upwelling Events in the Ne Baltic Sea

Paalme, T.; Torn, K.; Martin, G.; Kotta, I., and Suursaar, Ü., 2020. Littoral benthic communities under effect of heat wave and upwelling events in NE Baltic Sea. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 133–137. Coconut Creek (Florida), ISSN 0749-0208.The Baltic Sea forms a dynamic marine habitat with strong latitudinal and longitudinal gradients in many essential environmental variables. This environmental setting controls pelagic and benthic biodiversity by providing very narrow ecological niches for species displaying varying tolerances to environmental factors such as salinity, temperature and turbidity. In this study, changes in benthic communities in relation to extreme weather conditions, such as the occurrence of heat waves (HW) and coastal upwelling (CU) events, were analyzed and described in the north-eastern Baltic Sea. In the summer of 2018, the maximum water temperatures in the studied coastal sea sections varied between 20 and 25°C at 5 m depth whereby recorded values were up 7°C higher compared to that of the long-term mean. However, daily water temperature showed remarkable variation due to upwelling events occurring on multiple occasions with extreme temperature shifts of 14°C being recorded within a period of a few days. In the NE Baltic Sea, salinity gradient is up to 7 PSU in outer areas and it falls to zero in bays with riverine impact. Salinity has significant importance on benthic species abundance, richness and distribution. A rapid increase in salinity was observed during upwelling events. Extraordinarily, heat wave accompanied with upwelling event caused the increase of zoobenthic biodiversity and species-specific response of abundances. In contrast, the effect on macrovegetation species composition and proportion of opportunistic species was rather negative.

Improving the predictive capability of benthic species distribution models by incorporating oceanographic data – Towards holistic ecological modelling of a submarine canyon

Submarine canyons are associated with increased biodiversity, including cold-water coral (CWC) colonies and reefs which are features of high conservation value that are under increasing anthropogenic pressure. Effective spatial management and conservation of these features requires accurate distribution maps and a deeper understanding of the processes that generate the observed distribution patterns. Predictive distribution modelling offers a powerful tool in the deep sea, where surveys are constrained by cost and technological capabilities. To date, predictive distribution modelling in canyons has focussed on integrating groundtruthed acoustically acquired datasets as proxies for environmental variables thought to influence faunal patterns. Physical oceanography is known to influence faunal patterns but has rarely been explicitly included in predictive distribution models of canyon fauna, thereby omitting key information required to adequately capture the species-environment relationships that form the basis of predictive distribution modelling. In this study, acoustic, oceanographic and biological datasets were integrated to undertake high-resolution predictions of benthic megafaunal diversity and CWC distribution within Whittard Canyon, North-East Atlantic. The main aim was to investigate which environmental variables best predict faunal patterns in canyons and to assess whether including oceanographic data improves predictive modelling. General additive models, random forests and boosted regression trees were used to build predictive maps for CWC occurrence, megafaunal abundance, species richness and biodiversity. To provide more robust predictions, ensemble techniques that summarise the variation in predictions and uncertainties between modelling approaches were applied to build final maps. Model performance improved with the inclusion of oceanographic data. Ensemble maps identified areas of elevated current speed that coincided with steep ridges and escarpment walls as the areas most likely to harbour CWCs and increased biodiversity, probably linked to local hydrodynamics interacting with topography to concentrate food resources. This study shows how incorporating oceanographic data into canyon models can broaden our understanding of processes generating faunal patterns and improve the mapping of features of conservation, supporting effective procedures for spatial ecosystem management.

The influence of environmental and spatial factors on benthic invertebrate metacommunities differing in size and dispersal mode

Understanding the drivers of species distribution is an important topic in conservation biology and ecology, pertaining to species traits like dispersal strategies and species–environment interactions. Here we examined the drivers of benthic species distribution at 20 sections of a second-order stream network. Environmental and spatial factors and the dispersal modes of the organisms were considered. We expected that species with aerial dispersal capabilities like insects would be less restrained by distance between sites and thus mostly affected by environmental factors. In contrast, we hypothesized that completely benthic species would mainly be affected by spatial factors due to limited dispersal. However, microscopic species like nematodes characterized by a high passive dispersal potential may be less limited by spatial factors. When using redundancy analyses and subsequent variance partitioning, the included variables explained 24% (insects), 24% (non-flying macrobenthos), and 32% (nematodes) of the variance in the respective community composition. Spatial factors mainly explained the species composition of all tested groups. In contrast with other larger species, nematodes were characterized by fine-scale patterns that might have been induced by random processes (e.g., random distribution and priority effects). Our study showed that dispersal processes are crucial in shaping benthic communities along streams albeit the relatively small sampling area (max. distance between sampling sites: 2 km). The demonstration of spatial factors as important drivers of the species distribution of passively dispersing benthic organismal groups highlights the role played by connectivity in determining species distribution patterns in river systems.