Benthic Mats Research Articles

(Sub‐)Antarctic endemic cyanobacteria from benthic mats are rare and have restricted geographic distributions

The Antarctic terrestrial macrobiota are highly endemic and biogeographically structured, but whether this also holds true for microbial groups remains poorly understood. We studied the biogeographic patterns of Antarctic cyanobacteria from benthic microbial mats sampled in 84 lakes from two sub‐Antarctic islands, as well as from eight Antarctic Conservation Biogeographic Regions (ACBRs) which were previously defined based mainly on macroscopic taxa. Analysis of 16S rRNA gene sequences revealed that Antarctic and sub‐Antarctic lakes host significantly different cyanobacterial communities, yet that the bioregionalization pattern did not correspond to the division into ACBRs. Both Antarctic and sub‐Antarctic lakes contain a high number of potentially endemic taxa (41% of the total diversity), of which 33.3% attain a relative abundance of < 1%. Our findings highlight the uniqueness of Antarctic microbiota and the need for increased protection of inland waters in both Antarctica and the sub‐Antarctic islands.

Antarctic lake viromes reveal potential virus associated influences on nutrient cycling in ice-covered lakes.

The McMurdo Dry Valleys (MDVs) of Antarctica are a mosaic of extreme habitats which are dominated by microbial life. The MDVs include glacial melt holes, streams, lakes, and soils, which are interconnected through the transfer of energy and flux of inorganic and organic material via wind and hydrology. For the first time, we provide new data on the viral community structure and function in the MDVs through metagenomics of the planktonic and benthic mat communities of Lakes Bonney and Fryxell. Viral taxonomic diversity was compared across lakes and ecological function was investigated by characterizing auxiliary metabolic genes (AMGs) and predicting viral hosts. Our data suggest that viral communities differed between the lakes and among sites: these differences were connected to microbial host communities. AMGs were associated with the potential augmentation of multiple biogeochemical processes in host, most notably with phosphorus acquisition, organic nitrogen acquisition, sulfur oxidation, and photosynthesis. Viral genome abundances containing AMGs differed between the lakes and microbial mats, indicating site specialization. Using procrustes analysis, we also identified significant coupling between viral and bacterial communities (p = 0.001). Finally, host predictions indicate viral host preference among the assembled viromes. Collectively, our data show that: (i) viruses are uniquely distributed through the McMurdo Dry Valley lakes, (ii) their AMGs can contribute to overcoming host nutrient limitation and, (iii) viral and bacterial MDV communities are tightly coupled.

Cyanotoxins in Epipelic and Epiphytic Cyanobacteria from a Hypersaline Coastal Lagoon, an Environmental Hazard in Climate Warming Times and a Potential Source of New Compounds.

Cyanobacterial biodiversity and potential toxicity in coastal lagoons have barely been studied despite these transitional water systems being very important in conservation and for the preservation of economic resources. Most of these transitional systems have been affected by eutrophication, and climate change will severely affect them by promoting cyanobacteria growth, especially in Mediterranean areas. This study aims to characterize the diversity of epipelic and epiphytic cyanobacteria species in a Mediterranean coastal lagoon and their potential for toxins production (microcystins and saxitoxins). Strains were isolated and genetically identified. Toxins were extracted and quantified by LC/MS-MS. All the taxa belong to the former Oscillatoriales. The presence of Nodosilinea and Toxifilum is reported for the first time for Spanish waters, but Pseudanabaena, Phormidium, Geitlerinema and Synechococcus also formed part of benthic mats. All the strains contained Microcystin-YR (MC-YR), but saxitoxin (STX) was present only in the extracts of Nodosilinea and Pseudanabena. MC-LY, MC-LW and [D-Asp3] MC-LR were detected in the extracts of Synechococcus and MC-LF in Toxifilum, but at concentrations that did not permit quantification. Toxins production by epipelic and epiphytic strains in coastal lagoons may represent a hazard, but also an opportunity to obtain potentially interesting compounds that should be further studied.

Drivers of cyanotoxin and taste-and-odor compound presence within the benthic algae of human-disturbed rivers

Freshwater benthic algae form complex mat matrices that can confer ecosystem benefits but also produce harmful cyanotoxins and nuisance taste-and-odor (T&O) compounds. Despite intensive study of the response of pelagic systems to anthropogenic change, the environmental factors controlling toxin presence in benthic mats remain uncertain. Here, we present a unique dataset from a rapidly urbanizing community (Kansas City, USA) that spans environmental, toxicological, taxonomic, and genomic indicators to identify the prevalence of three cyanotoxins (microcystin, anatoxin-a, and saxitoxin) and two T&O compounds (geosmin and 2-methylisoborneol). Thereafter, we construct a random forest model informed by game theory to assess underlying drivers. Microcystin (11.9 ± 11.6 µg/m2), a liver toxin linked to animal fatalities, and geosmin (0.67 ± 0.67 µg/m2), a costly-to-treat malodorous compound, were the most abundant compounds and were present in 100 % of samples, irrespective of land use or environmental conditions. Anatoxin-a (8.1 ± 11.6 µg/m2) and saxitoxin (0.18 ± 0.39 µg/m2), while not always detected, showed a systematic tradeoff in their relative importance with season, an observation not previously reported in the literature. Our model indicates that microcystin concentrations were greatest where microcystin-producing genes were present, whereas geosmin concentrations were high in the absence of geosmin-producing genes. Together, these results suggest that benthic mats produce microcystin in situ but that geosmin production may occur ex situ with its presence in mats attributable to adsorption by organic matter. Our study broadens the awareness of benthic cyanobacteria as a source of harmful and nuisance metabolites and highlights the importance of benthic monitoring for sustaining water quality standards in rivers.

Environmental Factors Impacting the Development of Toxic Cyanobacterial Proliferations in a Central Texas Reservoir.

Cyanobacterial harmful algal proliferations (cyanoHAPs) are increasingly associated with dog and livestock deaths when benthic mats break free of their substrate and float to the surface. Fatalities have been linked to neurotoxicosis from anatoxins, potent alkaloids produced by certain genera of filamentous cyanobacteria. After numerous reports of dog illnesses and deaths at a popular recreation site on Lady Bird Lake, Austin, Texas in late summer 2019, water and floating mat samples were collected from several sites along the reservoir. Water quality parameters were measured and mat samples were maintained for algal isolation and DNA identification. Samples were also analyzed for cyanobacterial toxins using LC-MS. Dihydroanatoxin-a was detected in mat materials from two of the four sites (0.6-133 ng/g wet weight) while water samples remained toxin-free over the course of the sampling period; no other cyanobacterial toxins were detected. DNA sequencing analysis of cyanobacterial isolates yielded a total of 11 genera, including Geitlerinema, Tyconema, Pseudanabaena, and Phormidium/Microcoleus, taxa known to produce anatoxins, including dihydroanatoxin, among other cyanotoxins. Analyses indicate that low daily upriver dam discharge, higher TP and NO3 concentrations, and day of the year were the main parameters associated with the presence of toxic floating cyanobacterial mats.

İki yabancı gastropod türünün [Epitonium aranea Bonfitto, 2018 ve Stosicia annulata (Dunker, 1860) (Mollusca)] Akdeniz’den ilk defa kaydedilmesi

In a benthic material taken from the Levantine coast of Türkiye, Epitonium aranea Bonfitto, 2018, a species previously known from the Red Sea only, and Stosicia annulata (Dunker, 1860) distributed in Japan Sea, Persian Gulf and Central and East Indian Ocean were recorded for the first time from the Mediterranean Sea. Along with two unknown species from the region, herein have also been dealing with Melanella sp., Oscilla virginiae Peñas, Rolán and Sabelli, 2020 and Zafra pumila (Dunker, 1860) which are poorly known species from the area, and some remarks of the taxonomy and distribution of the studied taxa are discussed.

Polychaetes (Annelida: Polychaeta) off Kyky (Black Sea, Trkiye) with descriptions of three new species.

The examination of benthic materials collected in September 2022 at six stations off Kyky (south-west coast of the Black Sea, Trkiye) both on hard (three stations) and soft substrata (three stations) at depths ranging from 8 and 27 m revealed a total of 57 polychaete species belonging to 22 families. Among the species, the polynoid Malmgrenia polypapillata is a new record for the Black Sea fauna, and three species belonging to the Syllidae (Erinaceusyllis defneae n. sp.) and Terebellidae (Polycirrus karadenizicus n. sp. and P. rhombolabiatus n. sp.) are new to science. Algae dominated (Cystoseira cinita, Cladophora sp. and Phyllophora crispa) rocky substrata had 30 polychaete species and a maximum polychaete density of 7325 individuals/m2, while soft bottom substrata (fine sand and muddy sand with shell fragments) possessed 38 species and a maximum polychaete density of 3520 individuals/m2. The family Nereididae (3176% of the total number of individuals), and the species Platynereis dumerilii and Polyphthalmus pictus dominated hard bottom stations, whereas the families Nephtyidae, Spionidae and Dorvilleidae, and the species Micronephthys longicornis, Protodorvillea kefersteini and Prionospio maciolekae were represented by high number of individuals at soft-bottom stations.

Occurrence of tardigrades and morphometric and chemical conditions in rock pools by the Baltic Sea

Rock pools are eroded depressions in bedrock providing temporary aquatic habitats with varying morphometric and chemical conditions. Tardigrades have adapted to many habitats with varying and extreme abiotic conditions, including desiccation, but their occurrence in rock pools have rarely been investigated. This study investigated the occurrence of tardigrades and the morphometric and chemical conditions in rock pools by the Baltic Sea in southeast Sweden. Samples of benthic material were collected from rock pools at three sites near the town Karlshamn together with measurements of pool size, pH, temperature, salinity, and dissolved oxygen of the water. Tardigrades occurred in about one fifth of the rock pools and included five eutardigrade genera. Also rotifers and nematodes were observed in the samples. The morphometric and chemical variables varied both within and among the three sites but with few differences between rock pools with or without tardigrades. However, rock pools with tardigrades tended to be overall shallower than pools without tardigrades, indicating that more desiccating-prone rock pools may be more favourable habitats for tardigrades. The study shows that tardigrades are part of the micro-invertebrate fauna in rock pools and this habitat deserves more investigations into the occurrence of this animal group.

Efficient and rapid control of Eurasian watermilfoil (Myriophyllum spicatum) by combining benthic mats and hand pulling

AbstractEurasian watermilfoil (Myriophyllum spicatum L.) is an aquatic vascular plant that forms extensive dense beds in lakes. This invader competes with native plants, interferes with aquatic activities, and decreases riparian property values. In Canada, the use of aquatic herbicides is highly restricted. Environmental managers must therefore rely on physical methods such as hand pulling or benthic matting for control. Although these methods are not new, there has been little scientific investigation regarding their effectiveness and cost over multiple years. Benthic matting and hand pulling were used in Lac des Abénaquis (area: 1.2 km2) to control 3.6 ha of M. spicatum beds. Initiated by citizens in 2016, control procedures were scientifically studied in 2020 and 2021. Benthic fiberglass mats were deployed on dense M. spicatum patches for 10 wk. Isolated plants and patches <100 m2 were hand pulled by divers, and the harvested material surfaced via a suction hose or in hand-filled bags. By August 2021, all the M. spicatum patches had been eliminated, and only 560 widely scattered plants remained. Over the last 2 yr of control, hand pulling required 243 person-hours and removed 2,245 kg of biomass. The biomass brought to the surface was 2.4 times higher per person-hour with the suction system than with bags. The use of 1,000 m2 of benthic mats required 47 to 51 person-hours per summer season, including installation, removal, and maintenance. Intensive management (years 1 to 5) using benthic mats and hand pulling cost an estimated Can$185,000 (US$140,000) ha−1 of M. spicatum bed. Hand pulling of scattered individuals (years 6+), estimated at Can$20,000 (US$15,000) per summer, is essential to avoid reinfestation. An invasion of M. spicatum can successfully be managed in small lakes without herbicides, but control remains a costly and long-term endeavor.

Novel virulent and temperate cyanophages predicted to infect Microcoleus associated with anatoxin-producing benthic mats.

Cyanophages are crucial for regulating cyanobacterial populations, but their influence on anatoxin-producing Microcoleus mat dynamics remains unexplored. Here, we use metagenomics to explore phage presence in benthic mats from the Wolastoq|Saint John River (New Brunswick, Canada) and the Eel River (California, USA). We recovered multiple viral-like sequences associated with different putative bacterial hosts, including two cyanophage genomeswith apparently different replication strategies. A temperate cyanophage was found integrated in the genomes of Microcoleus sp. 3 recovered from the Eel River and is phylogenetically related to Phormidium phages. We also recovered novel virulent cyanophage genomes from Wolastoq and Eel River mats that were dominated by anatoxin-producing Microcoleus species predicted to be the host. Despite the geographical distance, these genomes have similar sizes (circa 239 kbp) and share numerous orthologous genes with high sequence identity. A considerable reduction of the anatoxin-producing Microcoleus species in Wolastoq mats following the emergence of the virulent phage suggests that phage infections have an important role in limiting the abundance of this toxigenic cyanobacterium and releasing anatoxins into the surrounding water. Our results constitute the first report of cyanophages predicted to infect mat-forming Microcoleus species associated with anatoxin production.

Novel diversity within Roseofilum (Desertifilaceae, Cyanobacteria) from marine benthic mats with description of four new species.

Benthic cyanobacterial mats (BCMs) are natural phenomena in marine environments. Reports of BCMs occurring across coastal marine environments have increased, partly driven by nutrient loading and climate change; thus, there is a need to understand the diversity involved in the proliferations and potential toxicity of the BCMs. Furthermore, marine cyanobacterial mats are observed growing on and affecting the health of corals with one specific cyanobacterial genus, Roseofilum, dominating the microbial mats associated with black band disease (BBD), a destructive polymicrobial disease that affects corals. To explore the diversity of Roseofilum, cyanobacterial mats from various marine habitats were sampled, and individual isolates were identified based on morphology, 16S rRNA gene phylogenies, 16S-23S ITS rRNA region sequence dissimilarities, and phylogenomics. Four novel species of Roseofilum were isolated from benthic marine mats, three from the coasts of Florida, United States (R. capinflatum sp. nov., R. casamattae sp. nov., and R. acuticapitatum sp. nov.) and one from the coast of France (R. halophilum sp. nov.). Our analyses revealed that Roseofilum associated with coral BBD and those not associated with corals but rather from coastal benthic mats are systematically distinct based on both phylogenetic and phylogenomic analyses. Enzyme-linked immunosorbent assay (ELISA) and LC-MS data indicated that microcystin production was found in one of the four species.

Cyanobacteria in Hypolithic Horizons of Soils in the Larsemann Hills Oasis, East Antarctica

The research is devoted to the analysis of biodiversity of Antarctic cyanobacteria in hypolithic organic-accumulative horizons of soils in the Larsemann Hills oasis. Studies of fouling glasses by the methods of light and confocal microscopy, as well as by fluorescent in situ hybridization, indicate that filamentous forms predominate among cyanobacteria in the upper layers of Antarctic hypolithic microbial communities. Strains of the genera Nostoc, Halotia, Leptolyngbya, Plectolyngbya, and Phormidesmis, as well as some new and previously undescribed cyanobacteria, were isolated from corresponding soil samples to clarify their taxonomic status. As a result, a unique collection of Antarctic cyanobacteria isolated from soils was obtained for the first time. The strains were described according to the modern polyphasic taxonomy methods based on an integrated assessment of morphological and molecular-genetic features. Phylogenetic analysis of primary 16S rRNA sequences and peculiarities of secondary structures of internal transcribed spacers enabled us to identify new taxa of potentially endemic cyanobacteria among the strains studied. The high level of similarity between the 16S rRNA gene sequences of soil strains and those previously found in benthic mats of water bodies in the Larsemann Hills confirmed the ability of cyanobacteria to expand beyond different ecological niches and to adapt to contrasting environmental conditions.

Occurrence, Distribution and Toxins of Benthic Cyanobacteria in German Lakes.

Cyanobacteria are favored by climate change and global warming; however, to date, most research and monitoring programs have focused on planktic cyanobacteria. Benthic cyanobacteria blooms also increase and pose a risk to animal and human health; however, there is limited knowledge of their occurrence, distribution and the toxins involved, especially in relation to their planktic conspecifics. Therefore, we analyzed the benthic and planktic life forms of cyanobacterial communities in 34 lakes in Germany, including a monitoring of cyanotoxins. Community analyses were based on microscopic examination and Illumina sequencing of the 16S rRNA gene. The analyses of cyanotoxins were carried out using LC-MS/MS and ELISA. Observed benthic mats containing cyanobacteria consisted mainly of Nostocales and Oscillatoriales, being present in 35% of the lakes. Anatoxin was the most abundant cyanotoxin in the benthic samples, reaching maximum concentrations of 45,000 µg/L, whereas microcystin was the predominate cyanotoxin in the open-water samples, reaching concentrations of up to 18,000 µg/L. Based on the results, specific lakes at risk of toxic cyanobacteria could be identified. Our findings suggest that monitoring of benthic cyanobacteria and their toxins should receive greater attention, ideally complementing existing open-water sampling programs with little additional effort.

A cylindrospermopsin-producing cyanobacterium isolated from a microbial mat in the Baltic Sea

Toxic benthic mats of cyanobacteria are associated with water quality problems and animal poisonings around the world. A strain of the filamentous cyanobacterial genus Kamptonema was isolated from a water bloom in the Baltic Sea four decades ago and later shown to produce cylindrospermopsins. However, the exact habitat of this strain remains unclear and cylindrospermopsins have not yet been reported from water blooms in the Baltic Sea. Here, we report the isolation of Kamptonema sp. UHCC 0994 from a benthic microbial mat collected in shallow water on the coast of Helsinki. We obtained draft genome sequences for the Kamptonema spp. PCC 7926 and UHCC 0994 strains that were isolated from the Baltic Sea. These genomes were 90–96% similar to previously studied Kamptonema sp. PCC 6506 and Kamptonema formosum PCC 6407, which were isolated from benthic and North American freshwater environments, respectively. The genomes of all four Kamptonema strains encode complete cylindrospermopsin biosynthetic gene clusters. We detected the production of cylindrospermopsin and 7-epi-cylindrospermopsin in the four Kamptonema strains using high-resolution liquid chromatography mass spectrometry. The four strains encode genes for producing gas vesicles distributed in two to three different regions of their genomes. Kamptonema spp. UHCC 0994 and PCC 7926 have both retained the ability to regulate their buoyancy when grown in liquid culture. Together this suggests that these toxic cyanobacteria may exhibit a tychoplanktic lifestyle in the Baltic Sea. This study suggests that microbial mats containing cyanobacteria could be a source of environmental toxins in the Baltic Sea.

Harmful Algal Blooms: A Prolific Issue in Urban Stormwater Ponds

Nutrient-driven cyanobacteria blooms are an increasingly common issue in freshwater environments, particularly in anthropogenically altered landscapes. As stormwater runoff is one of the largest sources of nutrients for freshwater bodies, stormwater retention ponds in urban and suburban areas are likely environments for harmful cyanobacteria blooms and were thus targeted for an in-depth investigation assessing taxonomic composition, bloom morphological composition, toxicity, and impact of nutrients and other environmental drivers. Eighty-seven algal blooms were sampled from 2019 to 2022 in the greater Wilmington, North Carolina, area. Physicochemical parameters were recorded, and blooms were classified by type (defined as surface mat, surface scum, water column distribution, or benthic mat) and dominant taxa. Blooms of potentially toxic cyanobacteria genera in the water column of stormwater retention ponds were most prevalent. Dissolved inorganic phosphorus was significantly related to chlorophyll-α, Microcystis bloom formation, and the production of microcystin. Seventeen potentially toxic cyanobacteria genera were identified in retention ponds, some of whose blooms demonstrated detectable microcystin. Monoclonal cultures isolated from some blooms were found to produce anabaenopeptin and saxitoxin. The results demonstrate a higher incidence of potentially toxic cyanobacteria over other bloom-forming taxa (chlorophytes, euglenoids, chrysophytes, dinoflagellates, and diatoms) in the 39 water bodies sampled. The frequency of blooms occurring in stormwater ponds and the diversity of potentially toxic cyanobacteria identified suggest such harmful blooms are likely widespread in similar freshwater environments across multiple urbanizing areas. The blooms sampled in this study were all within residential, commercial, or recreational areas easily accessible to people, presenting serious hazards to both environmental and public health.

A search for life in Palaeoproterozoic marine sediments using Zn isotopes and geochemistry

Sediments from the 2.1- to 1.9-billion-year-old Francevillian Group in southeastern Gabon include centimeter-sized pyritized structures suggestive of colonial organisms (El Albani et al., 2010), some of which may have been motile (El Albani et al., 2019). However, these interpretations were largely based on morphological and geochemical characteristics that lack metabolic clues and/or can be explained by abiotic processes. To move this work forward, we describe other centimeter-sized specimens, loosely referred to as lenticular forms (LF), from the same area and apply a more holistic approach including morphology, mineralogy, and geochemistry. The objects are 0.2–4 cm in diameter, and most of them are endowed with a regular brim that scales proportionally to external diameter reminiscent of biological order, hence rendering the LF putative biogenic traces. The LF are perfectly delineated in every direction and deflect the sedimentary layers on which they rest. X-ray microtomography further demonstrates that the LF are syn-depositional features and not concretions, while lead isotope systematics indicate that the geochemical imprint of diagenesis is inconsequential. Low sulfur content is largely concentrated in the organic matrix, and scarcity of pyrite and its persistence as micron-sized crystals show that the role of sulfate reduction is minor. Most interestingly, the fillings of the LF cavities show large and correlated excesses of organic carbon and zinc, with the latter being distinctly enriched in its light isotopes. The geochemical anomalies of the fillings relative to the host rock, notably those associated with Zn, clearly were buried with the LF, and further imply biogenicity. In this regard, a ten-fold increase in LF size towards the top of the black shale series hosting the LF might be related to increasing Zn (nutrient) availability. Although we cannot conclude with any certainty what these remnant organisms were, their features all taken together are evocative of very large agglutinate protists that grazed on bacterial biomass either in the water column or as benthic mats.

Short-chain n-alkanes in benthic mats and mosses from the Larsemann Hills, East Antarctica

Variation in leaf colour (green, red and grey) of mosses and lake benthic mats in Antarctica is often linked to water stress and ultraviolet light (UV-B) exposure. Changes in the abundance of organic compounds, such as pectin and phenols, are associated with mechanisms protecting against desiccation and UV radiation. However, the function of n-alkanes, especially against UV radiation, is rarely examined. Here, gas chromatography–mass spectrometry and Fourier-transform infrared spectroscopy analyses were performed to study the variation in n-alkanes in freshwater lake benthic mats and mosses collected from the Larsemann Hills in East Antarctica. Stable isotopes of organic carbon and nitrogen, environmental DNA characterisation and microscopy-based analyses are used to estimate the presence of cyanobacteria, algae and diatoms in moss and benthic mat consortia. Variation in the short-chain (n-C17 to n-C20) versus long-chain (n-C21 to n-C30) n-alkanes in the mosses and benthic mats with their colour were noted. The research links the relative abundance of short-chain n-alkanes to the UV-B exposure and proposes that Antarctic mosses and benthic mats synthesise short-chain n-alkanes for protection against UV-B.

Genomic characterization of coexisting anatoxin-producing and non-toxigenic Microcoleus subspecies in benthic mats from the Wolastoq, New Brunswick, Canada

The presence of toxigenic benthic cyanobacteria in riverine ecosystems is an increasing concern around the world. In 2018, the death of three dogs along the Wolastoq (also known as the Saint John River) in New Brunswick, Canada, was attributed to anatoxin exposure after they ingested benthic microbial mats found along the shore. Here, we shotgun sequenced the DNA of 15 non-axenic cyanobacterial isolates derived from four anatoxin-containing benthic mat samples associated with the dog deaths. Anatoxins were produced by some of the isolates, but not all. We retrieved near-complete Microcoleus metagenome-assembled genomes (MAGs) from the isolates that are closely related to anatoxin-producing Microcoleus from the Cardrona River (New Zealand), although the Microcoleus MAGs from the Wolastoq varied in the presence/absence of the anatoxin-a biosynthesis cluster. Sequence similarity at the genomic level suggests that toxigenic and non-toxigenic Microcoleus MAGs from the Wolastoq belong to the same species but are separate subspecies. The toxigenic and nontoxic Wolastoq Microcoleus subspecies coexisted in the mat samples in similar relative abundance. Overall genomic comparisons revealed that toxigenic Microcoleus MAGs are longer and code for more accessory genes than their non-toxigenic relatives, suggesting a differential responsiveness to changing environments, stress conditions and nutrient availability.

A dataset of benthic material distribution of coastal coral reefs in Hainan during 2018–2020

Based on the Sentinel-2 high resolution remote sensing image data, we adopted the object-oriented multi-scale segmentation technology and the nearest neighbor algorithm to classify benthic materials of offshore coral reefs in Wenchang City, Danzhou City, Sanya City of Hainan Province during 2018-2020. Then, combining with the remote sensing images of Gaofen-2 satellite and field validation data we verified the accuracy of the classification results. The dataset can be used to analyze the temporal and spatial changes of benthic materials in coastal coral reefs and assess the health status of coral reefs. Moreover, it can serve as a data foundation for the management and protection of coral reefs in Hainan Island.

The Effects of Roundup™ on Benthic Microbial Assemblages

Given the wide usage of Roundup, a common herbicide, the impacts of its presence in ecological communities are of great interest. Many studies have investigated the effects of glyphosate, the active ingredient in Roundup, on different factions of an ecosystem including on animals, plants, microorganisms, and nutrients. The current study expanded upon these works using Roundup instead of glyphosate to provide a realistic application in which to observe the development of microbial assemblages and nutrient composition in two different habitats. Winogradsky columns were prepared using benthic material from a ditch and a pond. Varying concentrations of Roundup were introduced to the columns at the beginning of the study and microbial growth and nutrient compositions from each column were measured weekly. The results indicate that the presence of Roundup has varying effects on microorganisms and nutrients. While photosynthetic microbes were negatively impacted, a shift in the microbial composition to heterotrophic microbes indicates that these microorganisms were able to utilize some ingredients in Roundup as a nutrient source. Additionally, the temporal analysis of nutrient compositions indicated that microbes metabolize glyphosate starting with the phosphate moiety even when the other compounds in Roundup are present. While these trends were observed in both benthic habitats, the composition of the ecological community can affect its ability to utilize the ingredients in Roundup as a nutrient source.