Benthic Community Composition Research Articles

Observation of exceptionally strong near-bottom flows over the Atlantis II Seamounts in the northwest Atlantic

Knowledge of near-bottom ocean current velocities and especially their extreme values is necessary to understand geomorphology of the seafloor and composition of benthic biological communities and quantify mechanical energy dissipation by bottom drag. Direct measurements of near-bottom currents in deep ocean remain scarce because of logistical challenges. Here, we report the results of flow velocity and pressure fluctuation measurements at three sites with depths of 2573–4443 m in the area where the Gulf Stream interacts with the New England Seamounts. Repeated episodes of unexpectedly strong near-bottom currents were observed, with the current speed at 4443 m of more than 0.40 m/s. At 2573 m, current speeds exceeded 0.20 m/s approximately 5% of the time throughout the entire eight-week measurement period. The maximum flow speeds of over 1.10 m/s recorded at this site significantly surpass the fastest previously reported directly measured current speeds at comparable or larger depths. A strong correlation is found between the noise intensity in the infrasonic band and the measured current speed. The noise intensity and the characteristic frequency increase with the increasing current speed. Machine-learning tools are employed to infer current speeds from flow-noise measurements at the site not equipped with a current meter.

The drivers of benthic macroinvertebrates communities along a subtropical river system: Sediments chemistry or water quality?

AbstractImpacts of metal pollution, either on water or in sediments within aquatic systems have been a serious challenge globally. Little is known about the ecological impacts of metal pollution on benthic macroinvertebrates species in sub–tropical river systems. The aim of this study was to examine benthic macroinvertebrates community composition in relation to sediment metal concentrations and other physicochemical variables in the Mutshundudi River system. Benthic macroinvertebrates sampling and community composition analysis, sediment collection, processing, metal analysis and assessment of water variables in the river system were done across two seasons at 12 sampling sites. The river was categorized into three segments: upstream, midstream and downstream. The results from geo‐accumulation (Igeo) values showed that sediments were loaded with Na, Zn, and B in all river segments. In comparison with South African water quality guidelines for aquatic ecosystems, water quality ranged from good at upstream sites because of low anthropogenic activities to very poor in downstream sites because of high anthropogenic activities. Sediments from the Mutshundudi River showed significant differences on high concentrations of metals (i.e., Mg, K, Na, and Cu) and seasonal variations. Both water quality and sediment chemistry were considered the driving factors of benthic macroinvertebrates, since species densities and composition reduced with a decline in water and sediment quality during both cool–dry and hot–wet seasons. Continuous build‐up of the metal contaminants, such as Mg, K, Na, and Cu in river sediments may pose adverse impacts on macroinvertebrate community structure.

Environmental impact on marginal coastal benthic communities within the Jeju Island, South Korea temperate transition zone

Aim of studyMarine climatic transition zones are boundary areas of major climate zones, here the boundary between the subtropical and temperate zones. They present areas containing high abundance of organisms living at the limit of their physiological tolerance. These marginal populations are particularly sensitive to changes in their environment. As such, marine climatic transition zones are excellent natural playgrounds for climate change-related hypothesis testing, especially with respect to marine habitat response to ocean warming. The marginal biogenic habitats around Jeju Island, South Korea, which lies within the temperate transition zone, have gradually changed from macroalgal-dominated to hard coral-dominated habitats. Understanding the specific abiotic environmental factors that influence the distribution of the marginal populations in temperate transition zones (i.e., species at their occurrence limit) is crucial to predicting and managing temperate zone habitat changes caused by climate change. This study aims to identify the specific abiotic environmental factors that contribute to explaining the current spatial distribution of the declining temperate and expanding subtropical foundation species in Jeju waters.MethodsCoverage and composition of sessile benthic communities were determined by photo-quadrat analysis at two depths (10 m and 15 m) at three sites along the island’s south, east, and north coasts in May and November 2022. Divergences in community composition between sites were characterized in light of ten quantitative environmental parameters.ResultsOur results show that sessile foundation communities vary significantly at different sites around the island. While the south is defined by high-latitude hard corals, predominately Alveopora japonica, the east is defined by the temperate canopy-forming macroalga Ecklonia cava, and the north is characterized by coralline algae. Winter sea surface temperature, water transparency, nutrient concentration, and water movement were statistically the most impactful environmental factors determining which foundation species constitute each distinct benthic community.ConclusionThis study provides valuable baseline information on the impacts of abiotic environmental factors on marine sessile communities in a temperate transition zone.

Local factors drive the richness, biomass and composition of benthic invertebrate communities in Neotropical reservoirs

Local factors drive the richness, biomass and composition of benthic invertebrate communities in Neotropical reservoirs

Functional Traits Drive the Changes in Diversity and Composition of Benthic Invertebrate Communities in Response to Hydrological Regulation

Of all the environmental elements that influence the biological communities of rivers, water flow characteristics are undoubtedly the most important. Unfortunately, natural hydrological characteristics are increasingly threatened by human activities, especially in alpine or high mountain areas where there are numerous hydropower plants. In this study, we analysed the impact of hydrological alterations on the macroinvertebrate community of a lowland river in NW Italy. Specifically, we analysed the macroinvertebrate communities of an unaffected site by comparing them with those of a site subject to hydrological alteration. We adopted an approach that is not only taxonomic but also functional, allowing us to study a component of biodiversity that is generally less known. Our results show that the flow-altered site hosted a benthic community with lower species and functional diversity than the control site. Interestingly, we also detected a number of significant differences between the summer and autumn samples. In particular, examination of community-weighted mean (CWM) trait values reveals significant variation in body size, voltinism, substrate, locomotion, feeding habits and other traits between sites and seasons. The integration of taxonomic and functional approaches provides a comprehensive understanding of how human-induced hydrological variations can affect aquatic biodiversity and ecological functions.

Advanced sustainable processes via functionalized Fe–N co-doped fishbone biochar for the remediation of plasticizer di-(2-ethylhexyl) phthalate-contaminated marine sediment

Sediments are important sinks for di-(2-ethylhexyl) phthalate (DEHP), a plasticizer, and thus, maintaining the sediment quality is essential for eliminating plasticizers in aqueous environments and recovering the sediment ecological functions. To mitigate the potential risks of endocrine-disrupting compounds, identifying an effective and eco-friendly degradation process of organic pollutants from sediments is important. However, sustainable and efficient utilization of slow pyrolysis for converting shark fishbone to generate shark fishbone biochar (SFBC) has rarely been explored. Herein, SFBC biomass was firstly produced by externally incorporating heteroatoms or iron oxide onto its surface in conjunction with peroxymonosulfate (PMS) to promote DEHP degradation and explore the associated benthic bacterial community composition from the sediment in the water column using the Fe-N-SFBC/PMS system. SFBC was pyrolyzed at 300–900 °C in aqueous sediment using a carbon-advanced oxidation process (CAOP) system based on PMS. SFBC was rationally modified via N or Fe–N doping as a radical precursor in the presence of PMS (1 × 10−5 M) for DEHP removal. The innovative SFBC/PMS, N-SFBC/PMS, and Fe-N-SFBC/PMS systems could remove 82%, 65%, and 90% of the DEHP at pH 3 in 60 min, respectively. The functionalized Fe3O4 and heteroatom (N) co-doped SFBC composite catalysts within a hydroxyapatite-based structure demonstrated the efficient action of PMS compared to pristine SFBC, which was attributed to its synergistic behavior, generating reactive radicals (SO4•–, HO•, and O2•–) and non-radicals (1O2) involved in DEHP decontamination. DEHP was significantly removed using the combined Fe-N-SFBC/PMS system, revealing that indigenous benthic microorganisms enhance their performance in DEHP-containing sediments. Further, DEHP-induced perturbation was particularly related to the Proteobacteria phylum, whereas Sulfurovum genus and Sulfurovum lithotrophicum species were observed. This study presents a sustainable method for practical, green marine sediment remediation via PMS-CAOP-induced processes using a novel Fe-N-SFBC composite material and biodegradation synergy.

Marine lebensspuren: improving the classification of seafloor traces from underwater imagery and observations

Taxonomy is a dynamic and evolving scientific field in biological and paleontological research, which describes and systematises species and other taxa and thus lays the foundation to solve and structure biological questions. The study of past (fossil) and modern (present) seafloor traces holds huge potential for understanding the composition, behavioural ecology, and ecosystem impact of benthic communities, e.g., in terms of bioturbation and carbon cycling. In trace fossil research (paleoichnology), ichnotaxonomical analysis is based on the application of ichnotaxobases, morphology being the most important and useful criterion. However, marine neoichnological analyses (modern traces; lebensspuren) have no standardised ichnotaxobases. In the literature, classification based on morphological descriptions or behavioural assignations can be found, but without consensus. This lack of standardised terminology hinders comparisons among studies and regions. Through this manuscript, we discuss the limitations of marine lebensspuren characterisation through underwater observations and how further classification could be done (i.e., possible ichnotaxobases). Considering that most of the classifications will be based on marine still images, we propose a classification for marine lebensspuren based on a combination of three labels: 1) morphology (e.g., M-ridged trail), 2) behaviour determination (e.g., locomotion and feeding), and 3) tracemaker taxonomy (e.g., Echinocrepis rostrata). Accordingly, the classification will be 1) M-ridged trail 2) Locomotion and feeding 3) Echinocrepsis rostrata. A set of recommendations is given to address all three labels. Also, we describe some of the contrasting positions of paleo- and neoichnology, particularly where a solution presently seems difficult to find, and argue that open nomenclature could be useful as still images contain large amounts of information. Finally, we provide examples of the usage of this classification for input to a marine lebensspuren online repository and how this nomenclature can help to compare worldwide lebensspuren in a consistent way.

Spatial variation in the rocky temperate benthic mesophotic communities of the Wellington region in New Zealand

ABSTRACT Temperate mesophotic ecosystems (TMEs) have only recently been recognised as distinct ecosystems and generally occur between 30 and 150 m at the limit of photosynthetic light penetration. In this study, we surveyed the benthic communities inhabiting rocky deep-water features in two regions at the south of New Zealand’s North Island to assess small (1–2 km) and larger (10–100 km) scale variation in the benthic communities they support: the Wellington South Coast (WSC) and the Kāpiti Coast (KC). We deployed Remotely Operated Vehicles at seventeen sites, three on the WSC and 14 on the KC, covering a depth range of 26 to 72 m. There was significant variation in the benthic community composition between sites, at both spatial scales, and with depth. Across all sites, sponges and bryozoans were by far the most abundant organisms, covering around 30% of the substrate, with all other groups having <5% cover. The sponges and bryozoans created complex three-dimensional structure on the seafloor, providing habitat and refuge for other mobile organisms. Our work provides an important baseline against which any future changes can be compared and will support future spatial management in this region.

Habitat type strongly influences the structural benthic invertebrate community composition in a landscape characterized by ubiquitous, long-term agricultural stress

ABSTRACT The importance of small waterbodies for biodiversity and ecosystem processes has long been neglected in research and policy development. However, because of their heterogeneous characteristics and habitat structures, these waterbodies are biodiversity hotspots for various aquatic and terrestrial organisms, as previously shown for rotifers, aquatic birds, and amphibians. Knowledge of benthic invertebrate community structures in small waterbodies is scarce. Thus, we performed a comprehensive field study of these structures in an agricultural landscape in the northeastern German lowlands. We obtained a dataset containing biological (taxon abundances) and chemical (pesticide residue and nutrient concentration) data as well as data on environmental parameters (e.g., conductivity and habitat type) for 111 samples. The dataset was analyzed using generalized linear models, permutational multivariate analysis of variance, and partial redundancy analysis to understand the relationships among benthic invertebrate communities, agricultural stressors, and environmental parameters. The factor that best explained structural community composition was habitat type. Pesticide and nutrient concentrations were of minor importance in our analysis. Because of the ubiquitous and long-term occurrence of the agricultural stressors, the structural indices used in benthic invertebrate biomonitoring were not sufficiently sensitive to provide information on the main environmental variables that shape macroinvertebrate communities.

Short-term temporal variability in offshore benthic biodiversity across hydrographic regions at a sub-Antarctic archipelago

AbstractCommunity composition is one of the main factors influencing the ecological functioning of any given ecosystem, with a more diverse community providing a larger set of services. Benthic community composition can vary at spatial and temporal scales, with the dynamics of primary production and benthic food availability being key determinants of community structure of a given system. Studies have indicated shifts in benthic community composition at sub-Antarctic Islands over a period of 30 years, linked to variability in food availability driven by climate change. Here, we aim to evaluate possible short-term variability in benthic community composition at the sub-Antarctic archipelago Prince Edward Islands (PEIs), sampling stations across three hydrographically dynamic regions over two consecutive years, 2016–2017. The results indicated significantly higher species richness and abundance in 2017 than in 2016, with some taxa also showing variation among regions around the PEIs. Such effects can be linked to different substratum type or hydrographic regime. This study further contributes to understanding variability and changes in benthic communities in the near future, an essential information to develop efficient management strategies for this vulnerable marine system.

Short-Term Spatiotemporal Variability in Seawater Carbonate Chemistry at Two Contrasting Reef Locations in Bocas del Toro, Panama

There is growing concern about the effects of ocean acidification (OA) on coral reefs, with many studies indicating decreasing calcium carbonate production and reef growth. However, to accurately predict how coral reefs will respond to OA, it is necessary to characterize natural carbonate chemistry conditions, including the spatiotemporal mean and variability and the physical and biogeochemical drivers across different environments. In this study, spatial and temporal physiochemical variability was characterized at two contrasting reef locations in Bocas del Toro, Panama, that differed in their benthic community composition, reef morphology, and exposure to open ocean conditions, using a combination of approaches including autonomous sensors and spatial surveys during November 2015. Mean and diurnal temporal variability in both physical and chemical seawater parameters were similar between sites and sampling depths, but with occasional differences in extreme values. The magnitude of spatial variability was different between the two sites, which reflected the cumulative effect from terrestrial runoff and benthic metabolism. Based on graphical vector analysis of TA–DIC data, reef metabolism was dominated by organic over inorganic carbon cycling at both sites, with net heterotrophy and net calcium carbonate dissolution dominating the majority of observations. The results also highlight the potentially strong influence of terrestrial freshwater runoff on surface seawater conditions, and the challenges associated with evaluating and characterizing this influence on benthic habitats. The Bocas del Toro reef is a unique system that deserves attention to better understand the mechanisms that allow corals and coral reefs to persist under increasingly challenging environmental conditions.

Convergent photophysiology and prokaryotic assemblage structure in epilithic cyanobacterial tufts and algal turf communities.

As global change spurs shifts in benthic community composition on coral reefs globally, a better understanding of the defining taxonomic and functional features that differentiate proliferating benthic taxa is needed to predict functional trajectories of reef degradation better. This is especially critical for algal groups, which feature dramatically on changing reefs. Limited attention has been given to characterizing the features that differentiate tufting epilithic cyanobacterial communities from ubiquitous turf algal assemblages. Here, we integrated an insitu assessment of photosynthetic yield with metabarcoding and shotgun metagenomic sequencing to explore photophysiology and prokaryotic assemblage structure within epilithic tufting benthic cyanobacterial communities and epilithic algal turf communities. Significant differences were not detected in the average quantum yield. However, variability in yield was significantly higher in cyanobacterial tufts. Neither prokaryotic assemblage diversity nor structure significantly differed between these functional groups. The sampled cyanobacterial tufts, predominantly built by Okeania sp., were co-dominated by members of the Proteobacteria, Firmicutes, and Bacteroidota, as were turf algal communities. Few detected ASVs were significantly differentially abundant between functional groups and consisted exclusively of taxa belonging to the phyla Proteobacteria and Firmicutes. Assessment of the distribution of recovered cyanobacterial amplicons demonstrated that alongside sample-specific cyanobacterial diversification, the dominant cyanobacterial members were conserved across tufting cyanobacterial and turf algal communities. Overall, these data suggest a convergence in taxonomic identity and mean photosynthetic potential between tufting epilithic cyanobacterial communities and algal turf communities, with numerous implications for consumer-resource dynamics on future reefs and trajectories of reef functional ecology.

Restored intertidal eelgrass (Z. marina) supports benthic communities taxonomically and functionally similar to natural seagrasses in the Wadden Sea

Ecological restoration has become an important management-tool to counteract the widespread losses of seagrass meadows and their associated biodiversity. In the Dutch Wadden Sea, long-term restoration efforts have recently led to the successful restoration of annual eelgrass (Zostera marina) at high densities on a local scale. However, it is yet unknown if restored seagrass plants also lead to improved local biodiversity and ecosystem functioning in the intertidal zone. We therefore compared the macrozoobenthos communities of a small-scale restored meadow to 22 naturally occurring intertidal seagrass meadows. Using a taxonomic and trait-based approach we aimed to study 1) how intertidal seagrasses (Zostera marina and Zostera noltii) affect benthic communities and their functional trait distribution and 2) if a restored meadow facilitates benthic communities similar to natural meadows. We found that both natural and restored seagrasses increased abundances of benthic animals and the richness (both taxonomic and functional) of associated benthic communities compared to nearby unvegetated areas. Additionally, the presence of intertidal seagrass shifted benthic community composition both taxonomically and functionally, thus broadening the niche space for species inhabiting tidal flats. Seagrasses especially facilitated epifaunal species and traits associated with these animals. Surprisingly, our results indicate that the mere presence of seagrass aboveground structure is enough to facilitate benthic communities, as neither higher seagrass cover nor biomass increased benthic biodiversity in the intertidal zone. By studying the effect of seagrass restoration on benthic diversity, we found that the restored meadow functioned similarly to the natural meadows after only two years and that the success of our restoration efforts indeed led to local biodiversity enhancements. Our findings contribute to the understanding of the ecological functioning of intertidal seagrasses and can be used to define/refine conservation and restoration goals of these valuable ecosystems.

Responses by benthic invertebrate community composition to dissolved organic matter in lakes decline substantially above a threshold concentration

Abstract Dissolved organic matter (DOM), often measured as dissolved organic carbon (DOC), plays a fundamental role in influencing the structure and function of lake ecosystems. Due to the myriad ecosystem effects of DOM, widespread observations of long‐term increasing DOM concentrations have received much attention from ecologists. DOM positively influences primary production and consumer production at low concentrations due to the fertilising influence of bound nutrients. However, beyond a unimodal peak in production, a reduced light environment may result in a negative effect on production. This unimodal model has been largely developed and tested in lakes with low to moderate DOM concentrations (i.e., typically ≤10 mg/L DOC). To understand ecological responses in lakes across a larger range in DOM concentrations, we examined the response of benthic invertebrate communities in 148 Swedish lakes with DOM concentrations ranging between 0.67 and 32.77 mg/L DOC. We found that increasing DOM concentrations had a strong effect on invertebrate community composition below c. 10 mg/L. Across this range, abundances of individual taxa both increased and decreased, probably in response to environmental change induced by DOM. However, in lakes above this concentration, increasing DOM had minimal influence on community composition. As DOM concentrations continue to increase, faunal communities in lakes below this 10 mg/L DOC threshold are likely to undergo substantial change whereas those above this threshold are likely to be minimally impacted.

Linking Resource Quality and Biodiversity to Benthic Ecosystem Functions Across a Land-to-Sea Gradient

Benthic macrofauna modifies carbon and nutrient retention and recycling processes in coastal habitats. However, the contribution of benthic consumers to carbon and nutrient storage and recycling shows variation over spatial scales, as the benthic community composition changes in response to differences in environmental conditions. By sampling both shallow sandy and deep muddy sediments across a land-to-sea gradient in the northern Baltic Sea, we explored if benthic community composition, stoichiometry and process rates change in response to alterations in environmental conditions and food sources. Our results show that benthic faunal biomass, C, N, and P stocks, respiration rate and secondary production increase across the land-to-sea gradient in response to higher resource quality towards the open sea. The seston δ13C indicated terrestrial runoff and δ15N sewage input at the innermost study sites, whereas more fresh marine organic matter towards the open sea boosted benthic faunal carbon storage, respiration rate, and secondary production, that is, the generation of consumer biomass, which are essential processes for carbon turnover in this coastal ecosystem. Also, biological factors such as increasing species richness and decreasing biomass dominance of the clam Macoma balthica were significant in predicting benthic faunal C, N, and P stocks and process rates, especially at sandy sites. Interestingly, despite the variation in food sources, the benthic faunal C:N:P ratios remained stable across the gradient. Our results prove that human activities in the coastal area can influence the important links between biodiversity, structure, and process rates of benthic communities by modifying the balance of available resources, therefore hampering the functioning of coastal ecosystems.

Monitoring coral reef conditions in the Biorock Pemuteran rehabilitation area during the 2016 coral bleaching

Pemuteran is well-known for its community-based coral reef conservation activities utilising Biorock technology, through the application of low voltage electricity. The main objective of this research is to assess the condition of coral reefs and fish communities within the Biorock area in Pemuteran, Bali. Data collection was implemented in June 2016 at the bleaching event, employing the Point Intercept Transect (PIT) method, and the Underwater Visual Census (UVCs) method. The benthic community composition at both research stations was dominated by dead coral with algae (Biorock Pemuteran 48.9%, Menjangan Island 51%). Both research locations exhibited branching coral and massive coral as the predominant coral lifeforms. Observational findings reveal noticeable differences in the community structure of coral fish between Biorock Pemuteran and Menjangan Island waters. A total of 11,260 individuals covering 120 fish species across 21 families. Higher fish abundance in Menjangan Island (1,326 ± 224 ind/250 m2) compared to Biorock Pemuteran (551 ± 235 ind/250 m2). The condition of coral reefs at both research locations is included in the poor category (0 – 24.9%). The reef fish community in both Biorock Pemuteran and Menjangan Island is in a stable condition with low dominance level and a moderate to high diversity.

Seasonal regulation of tidal creek burrow distribution: Unveiling the dynamic interplay of biotic and abiotic factors

Intertidal creek ecosystems in saltmarsh wetlands provide crucial ecological services, with burrows facilitating material exchange between these environments. Investigating burrow distribution in tidal creeks is essential, yet the underlying mechanisms remain poorly understood. Our study conducted field observations during two seasons, dividing the typical creek section into microhabitats: flat (F), gentle edge (GE), gentle slope (GS), steep slope (SS), and steep edge (SE). Comprehensive analysis of sediment samples encompassed assessments of water content, organic matter, particle size, and salinity. Burrow parameters were extracted using a deep learning method applied to sample images. Benthic biodiversity and community compositions were characterized through eDNA analysis. Our findings revealed significant variations in burrow distribution, sediment properties, and community compositions, both between and within creek sections. Temporal heterogeneity emerged as a substantial influencer of burrow characteristics, while the propensity of benthic communities to respond to topography and sediment properties constituted a chief determinant of burrow distribution. Utilizing a structural equation model based on field data, we illuminated four response pathways governing burrow distribution. Abiotic factors, especially under temporal heterogeneity, had a paramount impact, highlighting the need to explore relative biotic and abiotic influences, considering seasonal regulation. These findings establish a foundational understanding of burrow distribution and its driving mechanisms in creek ecosystems. They offer valuable insights for future field observations and research directions in this field.

Salinity and resource availability as drivers of Baltic benthic fungal diversity

AbstractMarine biodiversity consists of a complex network of organisms responsible for keeping the ecosystem's balance. Fungi are an understudied group of organisms despite their recognized importance for ecosystem processes and diversity. How fungi respond to environmental change remains poorly understood, especially in marine benthic habitats. The Baltic Sea is a brackish coastal ecosystem with steep environmental gradients in a relatively limited geographical area and is therefore a particularly good system to investigate the impact of different abiotic factors on benthic fungal diversity. This study used environmental DNA (eDNA) metabarcoding to analyze the spatial dynamics of benthic fungal diversity in the Baltic Sea and quantify the environmental drivers that shape these dynamics. Based on 59 stations spreading over 1145 km the results showed that benthic fungal communities were dominated by the phylum Chytridiomycota, and the fungal species Alphamyces chaetifer and Operculomyces laminatus from this phylum were the main drivers of the community structure dissimilarities observed between regions. Water depth and salinity were the main predictors of the benthic fungal community composition. The impact of nutrient availability was also significant, possibly related to the known role of Chytridiomycota species such as A. chaetifer and O. laminatus in nutrient cycling. Our results indicate that the benthic fungal diversity of the Baltic Sea is shaped by salinity gradients and nutrient availability and highlights that the current fungal biodiversity is at risk of species shift or decline with predicted changes in salinity due to climate change and intensified eutrophication.

Benthic macroinvertebrate community structure in nutrient‐rich, spring‐fed streams recently invaded by non‐native New Zealand mud snails

Abstract Ecological roles of non‐native species can vary over space and time due to abiotic factors and characteristics of the invaded communities. For instance, nutrient availability, temperature, and flow regime can influence invasion outcomes in freshwaters. This variability makes it challenging to predict non‐native species' effects in newly introduced areas. New Zealand mud snails (Potamopyrgus antipodarum; NZMS) are among the most widespread aquatic invasive species globally and have recently been detected in highly productive, spring‐fed streams in the upper mid‐west U.S.A. that are important trout fisheries. We hypothesised that the nutrient‐rich, thermally stable groundwater‐fed streams would provide favourable conditions for NZMS populations, potentially amplifying their effects on native communities. We surveyed benthic macroinvertebrate community structure at 10 streams representing a gradient of NZMS densities in the Driftless Area of southern Wisconsin. At five of the streams, we quantified temporal variation in NZMS and other benthic macroinvertebrates over three seasons. NZMS populations varied considerably across sites and over time, ranging from a few hundred to over 70,000 snails/m2. NZMS numerically represented as much as 97% of the invertebrate community at the highest density sites. At two sites, NZMS increased in population density by 50‐fold and 22‐fold over the survey duration, while at other sites their densities were relatively constant. Based on a principal components analysis summarising stream environmental variables, NZMS densities were negatively associated with stream discharge and positively associated with nitrogen and phosphorus concentrations. The total density and biomass of all benthic invertebrates, and Ephemeroptera and Amphipoda in particular, were negatively associated with NZMS density and biomass. Based on multivariate analyses, overall benthic community composition differed based on NZMS invasion status, as well as across seasons. These results suggest that the environments of southern Wisconsin spring‐fed streams provide favourable conditions for NZMS populations, allowing them to dominate some benthic communities. NZMS effects are likely to vary strongly across streams and over time within streams, highlighting the importance of future work to mechanistically test biotic and abiotic factors influencing their abundance.

Morpho-molecular characterization of sand-dwelling dinoflagellate communities from the German Wadden Sea and insights into their spatiotemporal distribution

ABSTRACT Benthic protist communities, including sand-dwelling dinoflagellates, are still poorly characterized worldwide and there is a lack of knowledge on their diversity and spatiotemporal dynamics. In this study, sediments were obtained from several coastal locations of the German Wadden Sea during the summer months of 2017 and 2018 to determine the diversity and spatiotemporal distribution of sand-dwelling dinoflagellates. The analyses consisted of light microscopy and the metabarcoding of small subunit (SSU) rRNA gene V4 region amplicons. Additionally, SSU rRNA sequences were newly obtained for 15 observed taxa included in a reference database and were used to taxonomically assign the obtained amplicon sequence variants (ASVs). The combination of morphological and molecular approaches allowed a deep characterization of dinoflagellate communities. Seventy-three morphospecies were detected by microscopy, while metabarcoding ASVs (amplicon sequence variants) were assigned to 116 species, resulting in a more comprehensive biodiversity inventory than achieved with either method alone. Pfiesteriaceae, Togula compacta and Thecadinium yashimaense predominated in the different sampling locations. Communities from Wilhelmshaven diverged from the others, consistent with its muddier sediment. A high level of resemblance was determined for the communities from each location, regardless of the sampling month and year, indicating a high summertime stability of benthic communities. Further efforts will be needed to characterize benthic protist diversity, as a first step in obtaining a complete picture of the habitat characteristics and physico-chemical conditions that influence benthic community composition.