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A 17-year time-series of fungal environmental DNA from a coastal marine ecosystem reveals long-term seasonal-scale and inter-annual diversity patterns
Get PDFChanging patterns in diversity are a feature of many habitats, with seasonality a major driver of ecosystem structure and function. In coastal marine plankton-based ecosystems, seasonality has been established through long-term time-series of bacterioplankton and protists. Alongside these groups, fungi also inhabit coastal marine ecosystems. If and how marine fungi show long-term intra- and inter-annual diversity patterns is unknown, preventing a comprehensive understanding of marine fungal ecology. Here, we use a 17-year environmental DNA time-series from the English Channel to determine long-term marine fungal diversity patterns. We show that fungal community structure progresses at seasonal and monthly scales and is only weakly related to environmental parameters. Communities restructured every 52-weeks suggesting long-term stability in diversity patterns. Some major marine fungal genera have clear inter-annual recurrence patterns, re-appearing in the annual cycle at the same period. Low relative abundance taxa that are likely non-marine show seasonal input to the coastal marine ecosystem suggesting land–sea exchange regularly takes place. Our results demonstrate long-term intra- and inter-annual marine fungal diversity patterns. We anticipate this study could form the basis for better understanding the ecology of marine fungi and how they fit in the structure and function of the wider coastal marine ecosystem
The Distribution of Fecal Contamination in an Urbanized Tropical Lake and Incidence of Acute Diarrheal Disease
Get PDFAquatic ecosystems of tropical countries are vulnerable to fecal contamination that could cause spikes in the
incidences of acute diarrheal disease (ADD) and challenge public health management systems. Vembanad lake, situated along the southwest coast of India, was monitored for one year (2018−2019). Escherichia coli, an indicator of fecal contamination, was prevalent in the lake throughout the year. Multiple antibiotic resistance among more than 50% of the E. coli isolates adds urgency to the need to control this contamination. The high abundance of E. coli and incidence of ADD were recorded during the early phase of
the southwest monsoon (June−July), prior to the once-in-a-century floods that affected the region in the later phase (August). The extent of inundation in the low-lying areas peaked in August, but E. coli in the water peaked in July, suggesting that contamination occurred even prior to extreme flooding. During the COVID-19-related lockdown in March−May 2021, fecal contamination in the lake and incidence of ADD reached minimum values. These results indicate the need for improving sewage treatment facilities and city planning in flood-prone areas to avoid the mixing of septic sewage with natural waters during extreme climate events or even
during the normal monsoon
Context-dependent changes in maritime traffic activity during the first year of the COVID-19 pandemic
Get PDFRapid implementation of human mobility restrictions during the COVID-19 pandemic dramatically reduced maritime activity in early 2020. But where and when activity rebounded, or remained low, during the full extent of 2020 restrictions remains unclear. Using global high-resolution datasets, we reveal a surprising degree of complexity in maritime activity patterns during 2020, yielding a more nuanced picture of how restrictions affected activity. Overall, shipping activity in Exclusive Economic Zones decreased (1.35 %), as expected, however high-seas activity increased (0.28 %). While these annual changes appear modest, there were striking spatially and temporally asynchronous variations in different vessel types’ activity in the second half of 2020, ranging from an > 80 % sustained reduction in passenger vessel activity to a 150 % increase in fishing activity. Results suggest systems-level responses were highly context-dependent, pinpointing areas that experienced significant reductions and spikes in activity, and providing hitherto missing details of COVID-19 impacts on economic and environmental sustainability
Seasonal development of a tidal mixing front drives shifts in community structure and diversity of bacterioplankton
Get PDFBacterioplankton underpin biogeochemical cycles and an improved understanding of the patterns and drivers of variability in their distribution is needed to determine their wider functioning and importance. Sharp environmental gradients and dispersal barriers associated with ocean fronts are emerging as key determinants of bacterioplankton biodiversity patterns. We examined how the development of the Celtic Sea Front (CF), a tidal mixing front on the Northwest European Shelf affects bacterioplankton communities. We performed 16S-rRNA metabarcoding on 60 seawater samples collected from three depths (surface, 20 m and seafloor), across two research cruises (May and September 2018), encompassing the intra-annual range of the CF intensity. Communities above the thermocline of stratified frontal waters were clearly differentiated and less diverse than those below the thermocline and communities in the well-mixed waters of the Irish Sea. This effect was much more pronounced in September, when the CF was at its peak intensity. The stratified zone likely represents a stressful environment for bacterioplankton due to a combination of high temperatures and low nutrients, which fewer taxa can tolerate. Much of the observed variation was driven by Synechococcus spp. (cyanobacteria), which were more abundant within the stratified zone and are known to thrive in warm oligotrophic waters. Synechococcus spp. are key contributors to global primary productivity and carbon cycling and, as such, variability driven by the CF is likely to influence regional biogeochemical processes. However, further studies are required to explicitly link shifts in community structure to function and quantify their wider importance to pelagic ecosystems
Global variability and controls on the accumulation of fallout radionuclides in cryoconite
Get PDFThe accumulation of fallout radionuclides (FRNs) from nuclear weapons testing and nuclear accidents has been eval�uated for over half a century in natural environments; however, until recently their distribution and abundance within
glaciers have been poorly understood. Following a series of individual studies of FRNs, specifically 137Cs, 241Am and 210Pb, deposited on the surface of glaciers, we now understand that cryoconite, a material commonly found in the
supraglacial environment, is a highly efficient accumulator of FRNs, both artificial and natural. However, the variabil�ity of FRN activity concentrations in cryoconite across the global cryosphere has never been assessed. This study thus
aims to both synthesize current knowledge on FRNs in cryoconite and assess the controls on variability of activity con�centrations. We present a global database of new and previously published data based on gamma spectrometry of
cryoconite and proglacial sediments, and assess the extent to which a suite of environmental and physical factors
can explain spatial variability in FRN activity concentrations in cryoconite. We show that FRNs are not only found
in cryoconite on glaciers within close proximity to specific sources of radioactivity, but across the global cryosphere,
and at activity concentrations up to three orders of magnitude higher than those found in soils and sediments in the
surrounding environment. We also show that the organic content of cryoconite exerts a strong control on accumulation
of FRNs, and that activity concentrations in cryoconite are some of the highest ever described in environmental matri�ces outside of nuclear exclusion zones, occasionally in excess of 10,000 Bq kg−1
. These findings highlight a need for
significant improvements in the understanding of the fate of legacy contaminants within glaciated catchments. Future
interdisciplinary research is required on the mechanisms governing their accumulation, storage, and mobility, and
their potential to create time-dependent impacts on downstream water quality and ecosystem sustainability
Review of Admirandus Belogurov & Belogurova, 1979 (Nematoda, Oncholaimidae) with the description of a new species and the first record of the genus from Brazil
No full textThe present study provides a description of a new Admirandus species from northeastern Brazil, together with an updated species identification key. Admirandus capibaribei sp. n. can be distinguished from all the other Admirandus species by its physical dimensions (body length, a, stoma and spicule ratios), sexual dimorphism of the tail, the absence of pre-cloacal supplements, and the presence of a row of denticles at the base of the right ventrosublateral tooth. While Admirandus has been reported from temperate, subtropical and tropical environments around the world, this is the first record of the genus from Brazil. Further research on Admirandus and other Adoncholaiminae species, which include the integration of morphological and molecular approaches, will be important to provide a better understanding of the taxonomy of this group, as well as on its demanian system
Organization of planktonic Tintinnina assemblages in the Atlantic Ocean
Get PDFMarine plankton have different biogeographical distribution patterns. However, it is not clear how the entire plankton assemblage is composed of these species with distinct biogeographical patterns. Tintinnina (tintinnids) is single-celled planktonic protozoa commonly used as model organisms in planktonic studies. In this research, we investigated the organization of Tintinnina assemblages along the Atlantic Meridional Transect (AMT) spanning over 90 degrees of latitude during the 29th AMT cruise (2019). Tintinnina with high frequency of occurrence was classified into four biogeographic distribution patterns (equatorial, gyre, frontal, and deep Chl a maximum) according to their vertical and horizontal distribution. All species falling within each distribution pattern formed a sub-assemblage. Equatorial sub-assemblage dominated in upper waters of the equatorial zone and gyre centres. Equatorial and frontal sub-assemblages co-dominated in upper waters of the frontal zones. Deep Chlorophyll a maximum Layer (DCM) sub-assemblage dominated in the DCM waters. Some Tintinnina species with high abundance could be used as indicator species of sub-assemblages. The Tintinnina assemblages in the northern and southern hemispheres exhibited asymmetry in terms of species composition. The latitudinal gradient of Tintinnina species richness was bimodal, which was shaped by the superposition of the species number of the four sub-assemblages with latitude. The result of this study contributes to the understanding of Tintinnina assemblage in the equatorial zone and subtropical gyres of the Pacific and Indian Ocean. It is also valuable for predicting the influence of global warming on changes in Tintinnina distribution and species richness
Modeling Carbon Budgets and Acidification in the Mediterranean Sea Ecosystem Under Contemporary and Future Climate
Get PDFWe simulate and analyze the effects of a high CO2 emission scenario on the Mediterranean Sea biogeochemical state at the end of the XXI century, with a focus on carbon cycling, budgets and fluxes, within and between the Mediterranean subbasins, and on ocean acidification. As a result of the overall warming of surface water and exchanges at the boundaries, the model results project an increment in both the
plankton primary production and the system total respiration. However, productivity increases less than respiration, so these changes yield to a decreament in the concentrations of total living carbon, chlorophyll, particulate organic carbon and oxygen in the epipelagic layer, and to an increment in the DIC pool all over the basin. In terms of mass budgets, the large increment in the dissolution of atmospheric CO2 results in an increment of most carbon fluxes, including the horizontal exchanges between eastern and western sub-basins, in a reduction of the organic carbon component, and in an
increament of the inorganic one. The eastern sub-basin accumulates more than 85% of the absorbed atmospheric CO2. A clear ocean acidification signal is observed all over
the basin, quantitatively similar to those projected in most oceans, and well detectable also down to the mesopelagic and bathypelagic layers
The impact of ocean biogeochemistry on physics and its consequences for modelling shelf seas
Get PDFWe use modelling and assimilation tools to explore the impact of biogeochemistry on physics in the shelf sea environment, using North-West European Shelf (NWES) as a case study. We demonstrate that such impact is significant: the attenuation of light by biogeochemical substances heats up the upper 20 m of the ocean by up to 1 °C and by a similar margin cools down the ocean within the 20–200 m range of depths. We demonstrate that these changes to sea temperature influence mixing in the upper ocean and feed back into marine biology by influencing the timing of the phytoplankton bloom, as suggested by the critical turbulence hypothesis. We compare different light schemes representing the impact of biogeochemistry on physics, and show that the physics is sensitive to both the spectral resolution of radiances and the represented optically active constituents. We introduce a new development into the research version of the operational model for the NWES, in which we calculate the heat fluxes based on the spectrally resolved attenuation by the simulated biogeochemical tracers, establishing a two-way coupling between biogeochemistry and physics. We demonstrate that in the late spring–summer the two-way coupled model increases heating in the upper oceanic layer compared to the existing model and improves by 1–3 days the timing of the simulated phytoplankton bloom. This improvement is relatively small compared with the existing model bias in bloom timing, but is sufficient to have a visible impact on model skill in the free run. We also validate the skill of the two-way coupling in the context of the weakly coupled physical–biogeochemical assimilation currently used for operational forecasting of the NWES. We show that the change to the skill is negligible for analyses, but it remains to be seen how much it differs for the forecasts
Microplastic ingestion in zooplankton from the Fram Strait in the Arctic
Get PDFSome of the highest microplastic concentrations in marine environments have been reported from the Fram Strait in
the Arctic. This region supports a diverse ecosystem dependent on high concentrations of zooplankton at the base of the food web. Zooplankton samples were collected during research cruises using Bongo and MOCNESS nets in the boreal summers of 2018 and 2019. Using FTIR scanning spectroscopy in combination with an automated polymer identification approach, we show that all five species of Arctic zooplankton investigated had ingested microplastics.
Amphipod species, found in surface waters or closely associated with sea ice, had ingested significantly more
microplastic per individual (Themisto libellula: 1.8, Themisto abyssorrum: 1, Apherusa glacialis: 1) than copepod species (Calanus hyperboreus: 0.21, Calanus glacialis/finmarchicus: 0.01). The majority of microplastics ingested were below 50 μm in size, all were fragments and several different polymer types were present. We quantified microplastics in water samples collected at six of the same stations as the Calanus using an underway sampling system (inlet at 6.5 m water depth). Fragments of several polymer types and anthropogenic cellulosic fibres were present, with an average concentration of 7 microplastic particles (MP) L−1 (0–18.5 MP L−1). In comparison to the water samples, those microplastics found ingested by zooplankton were significantly smaller, highlighting that the smaller-sized microplastics were being selected for by the zooplankton. High levels of microplastic ingestion in zooplankton have been associated with negative effects on growth, development, and fecundity. As Arctic zooplankton only have a short window of biological productivity, any negative effect could have broad consequences. As global plastic consumption continues to increase and climate change continues to reduce sea ice cover, releasing ice-bound microplastics and leaving ice free areas open to exploitation, the Arctic could be exposed to further plastic pollution which could place additional strain on this fragile ecosyste