Freshwater Outflow Research Articles

Patterns and predictors of condition indices in a critically endangered fish

Condition indices are key predictors of health and fitness in wild fish populations. Variation in body condition, therefore, can be used to identify stressful conditions that may impact endangered species, such as California’s endemic Delta Smelt (Hypomesus transpacificus McAllister, 1963). Here, we examined spatiotemporal variation in the condition indices of > 1600 Delta Smelt collected over nine years (2011–2019), a period characterized by tremendous variability in hydrodynamic and water quality conditions. The population exhibited low hepatosomatic index (HSI) and condition factor (CF) during September/October/November (fall), and both condition indices declined over the nine-year study during fall. HSI was positively correlated with indicators of pelagic productivity (e.g., Chlorophyll a, zooplankton biomass, and proximity to tidal wetlands), whereas CF was negatively correlated with temperature, peaking at a relatively cool 10–13 °C. In sum, seasonal and interannual variation in body condition corresponded most strongly with pelagic productivity and water temperature, with little correlation to freshwater outflow. Management actions that increase pelagic productivity, restore and freshen productive wetlands during late summer-fall, and reduce water temperatures overall are likely to benefit condition indices and, therefore, fitness of the Delta Smelt population.

Evaluating the Applicability of Thermal Infrared Remote Sensing in Estimating Water Potential of the Karst Aquifer: A Case Study in North Adriatic, Croatia

One of the most prominent tourist destinations in the Adriatic coast, the city of Opatija, is facing a problem concerning seasonal drinking water shortages. The existing water resources are no longer sufficient, and attention is being given to alternative resources such as the underlying karstic aquifer and several coastal springs in the city itself. However, the water potential of the area still cannot be estimated due to the insufficient hydrological data. The goal of this research was to evaluate the use of thermal infrared (TIR) remote sensing as the source of valuable information that will improve our understanding of the groundwater discharge dynamics. Ten Landsat ETM+ (enhanced thematic mapper plus) and two Landsat TM (thematic mapper) images of the north Adriatic, recorded during 1999–2004 at the same time as the field discharge measurements, were used to derive sea surface temperature (SST) and to analyze freshwater outflows seen as the thermal anomaly in the TIR images. The approach is based on finding the functional relationship between the size of the freshwater thermal signatures and the measured discharge data, and to estimate the water potential of the underlying aquifer. It also involved analyzing the possible connection between the adjusted size of the spring’s thermal signatures and groundwater level fluctuations in the deeper karst hinterland. The proposed methodology resulted in realistic discharge estimates, as well as a good fit between thermal anomalies with measured discharges and the groundwater level. It should be emphasized that the results are site specific and based on a limited data set. However, they confirm that the proposed method can provide additional information on groundwater outflow dynamics and coastal springs’ freshwater quantification.

A comparison of the temporal evolution of hydrodynamics and inlet morphology during Tropical Storm Fay (2020)

The record-setting North Atlantic hurricane season of 2020 had 30 named storms and reinforced the need for high-resolution, small-scale data collected in the nearshore zone during storm events to characterize storm impacts on coastal settings. To address these needs, hydrodynamic and morphologic data were collected during the 2020 Atlantic hurricane season, capturing fair weather conditions and the passage of Tropical Storm Fay (July 2020) near Chincoteague Inlet, Virginia. A sector-scanning rotary sonar captured high-resolution imagery of bedform evolution and data were analyzed to relate the migration of bedforms to the concomitant hydrodynamic conditions during the storm event. During the peak of the storm on 10 July 2020, significant wave height and period in Chincoteague Inlet were 0.96 m at 9.6 s arriving from the SSW (201°). The ripple field evolved during the storm in a manner consistent with that found in Hay and Mudge (2005): irregular ripples (O 20 cm wavelength) dominated during fair weather conditions, which developed into a washed-out, flat bed state as the storm arrived. During the peak of the storm, lunate megaripples (O 1 m wavelength) formed and migrated shoreward. A substantial outflow of freshwater from Chincoteague Bay occurred for up to seven days post-storm, and sediment transported by this outflow could serve as a yet-unidentified sediment source for the rapid growth of southern Assateague Island. This outflow of freshwater dampened waves and hindered ripple field recovery for up to seven days post-storm. These extreme event datasets are critical to inform coastal flood models and management decisions, as this work recognizes an increased risk of flooding for the town of Chincoteague from even the offshore passage of tropical storms.

How Much Arctic Fresh Water Participates in the Subpolar Overturning Circulation?

AbstractFresh Arctic waters flowing into the Atlantic are thought to have two primary fates. They may be mixed into the deep ocean as part of the overturning circulation, or flow alongside regions of deep water formation without impacting overturning. Climate models suggest that as increasing amounts of freshwater enter the Atlantic, the overturning circulation will be disrupted, yet we lack an understanding of how much freshwater is mixed into the overturning circulation’s deep limb in the present day. To constrain these freshwater pathways, we build steady-state volume, salt, and heat budgets east of Greenland that are initialized with observations and closed using inverse methods. Freshwater sources are split into oceanic Polar Waters from the Arctic and surface freshwater fluxes, which include net precipitation, runoff, and ice melt, to examine how they imprint the circulation differently. We find that 65 mSv (1 Sv ≡ 106 m3 s−1) of the total 110 mSv of surface freshwater fluxes that enter our domain participate in the overturning circulation, as do 0.6 Sv of the total 1.2 Sv of Polar Waters that flow through Fram Strait. Based on these results, we hypothesize that the overturning circulation is more sensitive to future changes in Arctic freshwater outflow and precipitation, while Greenland runoff and iceberg melt are more likely to stay along the coast of Greenland.

Inter-annual fluctuation in the population structure of an estuarine fish: Influence of environmental drivers

The environmental influence on the long-term variations of fish population structure, mainly that which drives the movements between segregated life stages, is not yet fully understood in estuarine systems. As a case study, we used seasonal (winter, spring) fishery-independent data of whitemouth croaker (Micropogonias furnieri) to determine the influence of environmental drivers (salinity, temperature, depth, freshwater outflow, and wind) on the long-term inter-annual scale (1993–2006) variation in the population structure. We used an approach based on size assemblages to represent and model the length distribution of the population structure. The different size assemblages (four in winter, five in spring) identified and verified by ordination analyses (cluster and nMDS) indicated a demographic structure that resembled juveniles, adolescent, and adult stages. The size assemblage composition showed significant inter-annual differences in both seasons. Additionally, there was significant decrease in the abundance of most size assemblages, except for juveniles which increased in winter. A multivariate regression tree analysis indicated that salinity expressed a greater influence on the size assemblage composition than the temperature. Moreover, the river outflow showed greater localized effects at the upper estuary across the variation in the spatial cover of salinity, which favored juveniles. On short time scales (between consecutive years), demographic variations responded to changes in the availability of environmental conditions preferred by each size assemblage, whereas long-term variations could be attributed to other effects (e.g. fishing mortality, habitat degradation).

Results of seawater intrusion in Mediterranean Spain and the Spanish islands according to the SASMIE report

Groundwater salinization of the Spanish aquifers by seawater has been known for decades. However, in only a few cases has this been managed to control the damage, as salinization affects small territories and involves water rights that in practice remain largely in the private domain. Groundwater salinization affects many people and industrial, tourist and agricultural activities. The greatest problems appeared in the last decades of the 20th century. Some of them still persist but others have been dwindling as water from other origins rather than local ones has been made available to substitute existing pumped wells. The abandonment of part of the coastal aquifers as a freshwater resource is an important hydraulic inheritance loss and especially a decrease in the guarantee of water availability if other costly and environmentally less friendly structures are not incorporated. Global and climatic change may modify the current situation. Coastal aquifers can be recovered if the cost is proportionate. Seawater intrusion implies an impairment to general wellbeing due to enhanced corrosion, negative effects on agriculture, deterioration of wetlands, and a decrease in the ecologically important continental freshwater outflow to the ocean. All this goes beyond the scope of the aquifer good status of coastal groundwater bodies to be achieved according to the European Water Framework Directive. Long-term manag ement action is needed, both structural and non–structural. The current experience in Spain has been synthetized in the SASMIE (2017) report, developed by the Technical University of Catalonia with the support of SUEZ-Spain and the overview of CETAQUA, which centers on the Mediterranean and island areas of Spain. Some of the most relevant situations here are considered, based on the available data.

Fixed-point time series, repeat survey and high-resolution modeling reveal event scale responses of the Northwestern Iberian upwelling

The hydrography and circulation of the Northwestern Iberian Margin (NWIM) was studied over an annual cycle from November 2008 to December 2009. The study was focused on the Cape Silleiro border region that separates the rugged northern coastline of the Rías Baixas embayments and the smoother southern coastline, a source of major fresh water outflows. Monthly across-shelf transects off Cape Silleiro monitored hydrography and currents, while an upward-looking ADCP registered currents in 72 m depth on the shelf over the period. To provide greater detail of the variability both spatial and temporal, during the annual cycle, a ROMS-AGRIF configuration of the region was built. Validation of the model against the observations produced robust results that reproduced many aspects of the observed variability. It was therefore possible to examine features of the NWIM, such as the seasonal cycle, wind-induced upwelling and downwelling and their associated horizontal circulations, as well as nearshore countercurrents related to freshwater plumes, in unprecedented detail. Five different scenarios were investigated in the study year through examination of characteristic physical processes: (1) late autumn upwelling, (2) high energy winter conditions, (3) spring upwelling-downwelling cycles, (4) summer upwelling, and (5) autumn transition to high energy conditions. The demonstration of the robust capacity of this model configuration, to reproduce in detail the phenomena observed in this region, suggests that the physical model could be reliably extended to other years in order to provide the basis for multidisciplinary studies in relation to biogeochemical cycles and harmful blooms. Other applications could include transport of sediments, larvae, microplastics and other contaminants as well as operational application for general ocean forecasting.

Washouts as a source of dissolved elements to the coastal ocean in southern Brazil and its hydrogeological characteristics

The coastal zone of Rio Grande do Sul state, Brazil, presents several surficial water bodies (washouts), which act as a drainage system of the coastal plain. Considering the entire extension of the coast, the number of washouts is very significant, thus, this study aims to assess in an unprecedented way the availability of nutrients, carbon and iron, dissolved in washout waters and its contribution in terms of concentration to the coastal ocean. Furthermore, due to groundwater in the beach region being one of the major sources for the formation and maintenance of these water bodies and influencing their hydrochemistry, we used the Ground Penetrating Radar as a tool to understand the interaction between the surficial and subterranean compartments, the influence of freshwater from the washouts on the aquifers and the extent of this interaction. The influence of the freshwater flux through the washout may reach 1000 m in length and a trough of up to 3.2 m. The medium outflow of freshwater by the washouts was heavily influenced by the rainfall, ranging between 0.12 m3 s−1 and 0.95 m3 s−1, in the dry and wet seasons, respectively. Throughout the Rio Grande do Sul coastal plain, washouts may represent 28% of the medium freshwater outflow from the Patos Lagoon Estuary and can top the outflow from Tramandaí Lagoon by 25%. The high outflow in the wet season impacted on the dissolved elements flux, with estimates of 274 ton y−1 for SiO44−, 0.42 ton y−1 for PO43−, 7.07 ton y−1 for total inorganic N, 1.7 ton y−1 for Fe and 262 ton y−1 for total dissolved C. Reckoning the values for the inorganic nitrogen flux, the washouts can support a potential primary production in the surf zone of 18 gC m−2 y−1, considering the entire Rio Grande do Sul coastal plain.

Integrative taxonomy identifies a new stingray species of the genus Hypanus Rafinesque, 1818 (Dasyatidae, Myliobatiformes), from the Tropical Southwestern Atlantic.

An integrative approach by the congruence of genetics, morphology and ecological niche modelling (ENM) was used to delimit a new species of Hypanus (Rafinesque, 1818), a recently resurrected genus of marine stingrays comprising eight species, five of which occur in the western Atlantic. The species with the widest distribution, Hypanus americanus (Hildebrand and Schroeder, 1928), from the northeastern coast of the United States to southeastern Brazil, was demonstrated to be paraphyletic based on protein-coding mitochondrial genome analyses. This data set also indicates that the genetic distance between the new species Hypanus berthalutzae sp. nov. and its three closely related species (H. americanus, H. longus and H. rudis) varies from 0.82% to 3.14%. In addition, Bayesian Analysis of Population Similarity using the mitochondrial gene mt-nd2 supports the separation of H. berthalutzae sp. nov. (southwestern Atlantic) from its sister species H. rudis (eastern Atlantic). Similarly, morphological and morphometric analyses corroborated four morphotypes within the H. americanus species group and indicated the ventral caudal fold height and length and interspiracular and interorbital lengths as useful measurements to distinguish among them. Claspers of adult males also exhibit morphological differences among species. The ENM agreed with molecular and morphological analyses and delimits the distribution of H. berthalutzae sp. nov. to shallow areas close to shore along the Brazilian coast, from the mouth of the Amazon River to São Paulo State, including the northeastern oceanic islands, suggesting that the great outflow of fresh water and sediments and the Mid-Atlantic Ridge might act as barriers. The integration of these data to describe a new species provides information relevant to their conservation status, because all species of the H. americanus species group are under the "data-deficient" status.

Methylmercury biomagnification in coastal aquatic food webs from western Patagonia and western Antarctic Peninsula

Mercury (Hg) is a global pollutant of concern because its organic and more toxic form, methylHg (MeHg), bioaccumulates and biomagnifies through aquatic food webs to levels that affect the health of fish and fish consumers, including humans. Although much is known about trophic transfer of MeHg in aquatic food webs at temperate latitudes in the northern hemisphere, it is unclear whether its fate is similar in biota from coastal zones of the southeastern Pacific. To assess this gap, MeHg, total Hg and food web structure (using δ13C and δ15N) were measured in marine macroinvertebrates, fishes, birds, and mammals from Patagonian fjords and the Antarctic Peninsula. Trophic magnification slopes (TMS; log MeHg versus δ15N) for coastal food webs of Patagonia were high when compared with studies in the northern hemisphere, and significantly higher near freshwater inputs as compared to offshore sites (0.244 vs 0.192). Similarly, in Antarctica, the site closer to glacial inputs had a significantly higher TMS than the one in the Southern Shetland Islands (0.132 vs 0.073). Composition of the food web also had an influence, as the TMS increased when mammals and seabirds were excluded (0.132–0.221) at a coastal site. This study found that both the composition of the food web and the proximity to freshwater outflows are key factors influencing the TMS for MeHg in Patagonian and Antarctic food webs.

Dynamics of Bioluminescence Potential and Physical, Bio‐Optical Properties on the Shelf and Shelf‐Slope of Delaware Bay

AbstractThe dynamics of physical and bio‐optical properties on the shelf and the shelf‐slope break areas offshore of the Delaware Bay were investigated. Compared to monthly means, there were elevated daily freshwater outflows. Glider observations demonstrated significant changes in bio‐optical properties before and after sampling fresher water masses. Prior to sampling fresher water masses, the glider observations exhibited a coincidence of high values in bioluminescence (BL) potential, chlorophyll, and optical backscattering. However, as the glider started to sample fresher water masses, there was a gradual decoupling of high values in BL potential with the high values in chlorophyll and optical backscattering. This indicates a shift from an autotrophic and mixotrophic toward a more heterotrophic bioluminescent community between water masses. During the glider survey, a high chlorophyll filament was observed by satellite ocean color imagery along the shelf‐slope break of the Delaware Bay. The high chlorophyll filament had weakened and disappeared in satellite imagery over the next 2 days when upwelling was progressing, and the glider started to sample fresher water masses. The filament was on the dense side of the shelf‐slope front, and the glider observations indicated a subduction of high chlorophyll values into subsurface (below the fresher surface water masses) with high values of BL potential deeper than high values of chlorophyll. The studies presented here are the first BL potential studies on the shelf and the shelf slope areas of the Delaware Bay, as well as the first studies of BL potential resulted from deployments of the glider with BL potential sensor on board.

Experimental investigation of tidal and freshwater influence on Symbiodiniaceae abundance in Anthopleura elegantissima.

The San Francisco Bay outflow creates a tidally influenced low-salinity plume that affects adjacent coastal sites. In the study region, Anthopleura elegantissima (Cnidaria; Anthozoa) hosts a single symbiont, the dinoflagellate Breviolum muscatinei. Salinity, temperature, and aerial stress induce a bleaching response similar to corals where symbionts are expelled, causing further energetic stress. Using field observations of environmental conditions and symbiont abundance at sites on a gradient of exposure to estuarine outflow, along with a fully crossed multifactorial lab experiment, we tested for changes in symbiont abundance in response to various combinations of three stressors. Lab experiments were designed to mimic short term outflow events with low salinity, high temperature, and aerial exposure treatments. The lab aerial exposure treatment was a statistically significant factor in suppressing symbiont repopulation (ANOVA, p = .017). In the field, symbiont density decreased with increasing tidal height at the site closest to freshwater outflow (ANOVA, p = .007), suggesting that aerial exposure may affect symbiont density more than sea surface temperature and salinity. Unanticipated documentation of survival in 9 months of sand burial and subsequent repopulation of symbionts is reported as a six-month extension to past observations, exemplifying strong tolerance to environmental insult in this Cnidarian mutualism. The study of this symbiosis is useful in examining predicted changes in ocean conditions in tidepool communities and considering relative sources of stress.

Combining resistivity and frequency domain electromagnetic methods to investigate submarine groundwater discharge in the littoral zone

Abstract. Submarine groundwater discharge (SGD) is an important gateway for nutrients and pollutants from land to sea. While understanding SGD is crucial for managing nearshore ecosystems and coastal freshwater reserves, studying this discharge is complicated by its occurrence at the limit between land and sea, a dynamic environment. This practical difficulty is exacerbated by the significant spatial and temporal variability. Therefore, to capture the magnitude of SGD, a variety of techniques and measurements, applied over multiple periods, is needed. Here, we combine several geophysical methods to detect zones of fresh submarine groundwater discharge (FSGD) in the intertidal zone, upper beach, dunes, and shallow coastal area. Both terrestrial electrical-resistivity tomography (ERT; roll-along) and marine continuous resistivity profiling (CRP) are used from the shallow continental shelf up to the dunes and combined with frequency domain electromagnetic (FDEM) mapping in the intertidal zone. In particular, we apply an estimation of robust apparent electrical conductivity (rECa) from FDEM data to provide reliable lateral and vertical discrimination of FSGD zones. The study area is a very dynamic environment along the North Sea, characterized by semi-diurnal tides between 3 and 5 m. CRP is usually applied in calmer conditions, but we prove that such surveys are possible and provide additional information to primarily land-bound ERT surveying. The 2D inversion models created from ERT and CRP data clearly indicate the presence of FSGD on the lower beach or below the low-water line. This discharge originates from a potable freshwater lens below the dunes and flows underneath a thick saltwater lens, present from the dunes to the lower sandy beach, which is fully observed with ERT. Freshwater outflow intensity has increased since 1980, due to a decrease of groundwater pumping in the dunes. FDEM mapping at two different times reveals discharge at the same locations, clearly displays the lateral variation of the zone of discharge, and suggests that FSGD is stronger at the end of winter compared to the beginning of autumn. ERT, CRP, and FDEM are complementary tools in the investigation of SGD. They provide a high-resolution 3D image of the saltwater and freshwater distribution in the phreatic coastal aquifer over a relatively large area, both off- and onshore.

The Mechanism of the Freshwater Outflow Through the Ganges‐Brahmaputra‐Meghna Delta

AbstractThe Ganges‐Brahmaputra‐Meghna (GBM) delta is a major source of freshwater for the Bay of Bengal. The flow through this megadelta is complex because of its large size and numerous river networks, making the region a challenging area for river‐routing models. This study investigates the dynamics of the riverine outflow across the GBM delta and its interaction with the ocean on monthly to seasonal time scales, using a two‐layer model that represents the riverine water and the oceanic water. The model simulates a seasonal increase and decrease of discharge and sea surface height (SSH) at both the main stem and the distributaries. Although discharge through the main stem is driven by that propagating from the upstream, model experiments show that the distributaries are an active region of river‐ocean interactions as a result of a river plume established on the oceanic side of the river mouth. This river plume is induced by river discharge in the presence of the Coriolis force and is associated with an increase in SSH along the coast. Backwater is induced at the river mouth, resulting in convergence and higher SSH in distributaries. The narrow, meandering, and shallow paths of the distributaries enhance the role of friction on the flow from the upstream, making their river mouths more sensitive to oceanic variability. The results of our study demonstrate that river plumes may play a central role in the dynamics of megadelta flow by connecting the dynamics at the main stem and the distributaries with ocean dynamics.

Vertical distribution of water mass properties under the influence of subglacial discharge in Bowdoin Fjord, northwestern Greenland

Abstract. Subglacial discharge has significant impacts on water circulation, material transport, and biological productivity in proglacial fjords of Greenland. To help clarify the fjord water properties and the effect of subglacial discharge, we investigated the properties of vertical water mass profiles of Bowdoin Fjord in northwestern Greenland based on summer hydrographic observations, including turbidity, in 2014 and 2016. We estimated the fraction of subglacial discharge from the observational data and interpreted the observed differences in subglacial plume behavior between two summer seasons with the numerical model results. At a depth of 15–40 m, where the most turbid water was observed, the maximum subglacial discharge fractions near the ice front were estimated to be ∼6 % in 2014 and ∼4 % in 2016. The higher discharge fraction in 2014 was likely due to stronger stratification, as suggested by the numerical experiments performed with different initial stratifications. Turbidity near the surface was higher in 2016 than in 2014, suggesting a stronger influence of turbid subglacial discharge. The higher turbidity in 2016 could primarily be attributed to a greater amount of subglacial discharge, as inferred from the numerical experiments forced by different amounts of discharge. This study suggests that both fjord stratification and the amount of discharge are important factors in controlling the vertical distribution of freshwater outflow.

Thermal Remote Sensing for Water Outflows Detection and Determination of the Role of Lineaments in Underground Hydrodynamics of Evia Island, Central Greece

The coastal karst system of Evia Island is developed due to the extended presence of carbonate formations, discharges into the sea either at the coastal zone or via submarine springs, having a direct relation to the tectonic system of the area. Thermal infrared remote sensing has been proved its capability in monitoring thermal differentiations of coastal water plumes. This work aims to locate the freshwater outflows through remote sensing and specific with the use of Landsat’s 8 thermal images and to reveal how the lineaments of the area control this karstification process. L8 contains two thermal bands (Band 10, high gain and Band 11, low gain) with resolution 30m which record the scattering of infrared radiation from the sea surface. Spectral Band 10 was selected due to the high gain characteristics which provide more suitable radiometric resolution (sensitivity). Finally, combing thermal images with geological maps, sea surface temperature (SST) maps have been created.

Hydrodynamic Conditions Effects on Soft-Bottom Subtidal Nearshore Benthic Community Structure and Distribution

This study assesses the impacts of wave action and freshwater outflow on soft-bottom benthic macrofauna spatial distribution and temporal stability along the highly exposed French Basque coast. Sediment characteristics and macrofauna abundance have been seasonally investigated during two years for nine stations located at the same (6 m) depth and spread over three subtidal sites showing distinct exposure levels. Wave climate has been determined through an operational numerical model. A total of 121 taxa were recorded, gathered in three main faunal assemblages, as revealed by classification and ordination methods. Non-parametric multivariate multiple regression (distance-based linear model) showed that the variations in macrofaunal distribution can be explained by hydrodynamic conditions. Wave exposure strongly linked to estuarine inputs were the most relevant abiotic factors influencing distributional patterns and functional structure as described by biological traits analysis. Despite the influence of these abiotic variables affecting sedimentary dynamics, seasonal stability was observed in macrobenthic assemblages composition suggesting an ability to recover from natural disturbances such as (e.g.) winter storms. In this way, these results provide baseline knowledge for future ecosystem and resource management in shallow subtidal areas strongly exposed to swell and freshwater outflow where soft-bottom macrozoobenthic communities are less frequently studied.

MiR-10 involved in salinity-induced stress responses and targets TBC1D5 in the sea cucumber, Apostichopus japonicas.

The sea cucumber is an economically important aquaculture species in China, where it encounter hypo-saline conditions caused by freshwater outflow from rivers and rainfall. MicroRNAs (miRNA) are small noncoding RNAs of about 22 nucleotides, which are crucial regulators of gene expression at the post-transcriptional level and are involved in a variety of physiological and pathophysiological processes. miR-10 is differentially expressed in salinity acclimation, and has a seed-region match with TBC1D5. The expression profiles of miR-10 and TBC1D5 indicate that miR-10 negatively regulates the expression of TBC1D5 in coelomocytes and sea cucumbers with a miR-10 agomir or antagomir. During salinity acclimation, up-regulation of miR-10 was induced after transfection in coelomocytes with a miR-10 inhibitor, while down-regulation of TBC1D5 was induced. The miR-10 expression maximum in coelomocytes appeared at 48h post-transfection with a miR-10 inhibitor, was later than that of in sea cucumbers, which appeared 24h after miR-10 antagomir injection. There was no longer a negative relationship between miR-10 and TBC1D5 expression in coelomocytes and sea cucumbers with miR-10 mimics or agomir during salinity acclimation. The miR-10 antagomir or agomir only affected sodium and NKA enzyme activities, and has little effect on other chloride and potassium ions. Our results demonstrate miR-10 directly regulates TBC1D5 by targeting its 3'-UTR, and that miR-10 suppression substantially increases TBC1D5 mRNA levels in vivo and in vitro. Furthermore, miR-10 and TBC1D5 fluctuating expression patterns after treatment with a miR-10 inhibitor or mimics during salinity acclimation may indicate that they are required for adaptation to salinity stress caused by environmental change. Especially, the miR-10 up-regulation in coelomocytes with miR-10 inhibitor during salinity acclimation indicated that they are required for adaptation to salinity stress caused by environmental change. We propose that miR-10 participates in a regulatory circuit that allows for rapid gene program transitions in response to osmotic stress.

Planktonic foraminifera as indicators of oceanographic complexity on the southern Caribbean Sea continental shelf

The southern Caribbean Sea over the northern South American continental shelf is oceanographically complex. It is subject to (1) widespread coastal upwelling, (2) wakes and eddies in the NW-flowing Guiana and Caribbean Currents to the lee of islands, and (3) the hypopycnal Orinoco River plume. Upwelled water is dispersed NW along high-productivity filaments. Offshore northern Trinidad, an intra-plume front separates higher-productivity Orinoco-derived water to the west from lower-productivity Amazon-derived water. This paper examines planktonic foraminiferal assemblages in surface sediment samples (a) below upwelling foci in the Gulf of Venezuela (GoV). North of Lake Maracaibo, and (b) at an upwelling focus in the North Coast Marine Area (NCMA) offshore northern Trinidad, near but west of the intra-plume front. The samples were collected for previous studies and only certain size fractions, which differed between the study areas, were available for current study.Samples from the GoV (>250 μm fraction; taken using an Alpine corer or a Petersen dredge) were assigned a priori to groups underlying upwelled and non-upwelled water. Discriminant analysis after cluster analysis confirmed these assignments. Total recovery was dominated by Neogloboquadrina dutertrei with lesser Globigerinoides ruberpink and the upwelling indicator Globigerina bulloides. All four non-upwelled samples, co-dominated by N. dutertrei and Gs. ruberpink, reflect seasonal freshwater outflow from Lake Maracaibo. Five upwelled-area samples were dominated by G. bulloides with subdominant N. dutertrei or Globigerinoides ruber Morphotype B. The remaining two upwelled samples (dominant N. dutertrei, subdominant Gs. ruber Morphotype A) apparently reflect the transition between upwelling and non-upwelling areas. The mean proportions of assemblages as Trilobatus sacculifer Morphotype A did not differ markedly between the upwelled and non-upwelled GoV clusters. This morphotype was absent from the Gulf proper but present to the north.NCMA total recovery (>150 μm fraction; samples taken using a van Veen grab) was dominated by Gs. ruber Morphotype B. Cluster analysis here indicated three clusters: Cluster 1, proximal to the intra-plume front; Cluster 2, distal to the intra-plume front; and Cluster 3, scattered throughout the NCMA. Upwelling was pervasive, canonical variate analysis (CVA) verifying that G. bulloides did not differentiate the clusters. Instead, these clusters were differentiated by Gs. ruber Morphotype B only, the proportional abundance of which was highest in Cluster I and lowest in Cluster 2. This pattern indicates that the influence of the Orinoco plume on assemblage composition is stronger than that of upwelling, Cluster 1 reflecting higher productivity near the front.

Distinct temporal dynamics of planktonic archaeal and bacterial assemblages in the bays of the Yellow Sea.

The Yellow Sea features unique characteristics due to strong tides and nutrient-enriched freshwater outflows from China and Korea. The coupling of archaeal and bacterial assemblages associated with environmental factors at two bay areas in the Yellow Sea was investigated. Temporal variations of the archaeal and bacterial assemblages were shown to be greater than the spatial variations based on an analysis of the 16S rRNA gene sequences. Distinct temporal dynamics of both planktonic archaeal and bacterial assemblages was associated with temperature, NO2-, and chlorophyll a ([chl-a]) concentrations in the bays of the Yellow Sea. The [chl-a] was the prime predictor of bacterial abundance, and some taxa were clearly correlated with [chl-a]. Bacteroidetes and Alpha-proteobacteria dominated at high [chl-a] stations while Gamma-proteobacteria (esp. SAR86 clade) and Actinobacteria (Candidatus Actinomarina clade) were abundant at low [chl-a] stations. The archaeal abundance was comparable with the bacterial abundance in most of the October samples. Co-dominance of Marine Group II (MGII) and Candidatus Nitrosopumilus suggests that the assimilation of organic nitrogen by MGII could be coupled with nitrification by ammonia-oxidizing archaea. The distinct temporal dynamics of the archaeal and bacterial assemblages might be attributable to the strong tides and the inflow of nutrient-rich freshwater.