Estuarine Sea Research Articles

The molecular response of Mytilus coruscus mantle to shell damage under acute acidified sea water revealed by iTRAQ based quantitative proteomic analysis

Mytilus coruscus is an economically important marine bivalve that lives in estuarine sea areas with seasonal coastal acidification and frequently suffers shell injury in the natural environment. However, the molecular responses and biochemical properties of Mytilus under these conditions are not fully understood. In the present study, we employed tandem mass spectrometry combined with isobaric tagging to identify differentially expressed proteins in the mantle tissue of M. coruscus under different short-term treatments, including shell-complete mussels raised in normal seawater (pH 8.1), shell-damaged mussels raised in normal seawater (pH 8.1), and acidified seawater (pH 7.4). A total of 2694 proteins were identified in the mantle, and analysis of their relative abundance from the three different treatments revealed alterations in the proteins involved in immune regulation, oxidation-reduction processes, protein folding and processing, energy provision, and cytoskeleton. The results obtained by quantitative proteomic analysis of the mantle allowed us to delineate the molecular strategies adopted by M. coruscus in the shell repair process in acidified environments, including an increase in proteins involved in oxidation-reduction processes, protein processing, and cell growth at the expense of proteins involved in immune capacity and energy metabolism. SignificanceThe impact of global ocean acidification on calcifying organisms has become a major ecological and environmental problem in the world. Mytilus coruscus is an economically important marine bivalve living in estuary sea area with seasonal coastal acidification, and frequently suffering shell injury in natural environment. Molecular responses of M coruscus under the shell damage and acute acidification is still largely unknown. For this reason, iTRAQ based quantitative proteomic and histological analysis of the mantle from M. coruscus under shell damage and acute acidification were performed, for revealing the proteomic response and possible adaptation mechanism of Mytilus under combined shell damage and acidified sea water, and understanding how the mussel mantle implement a shell-repair process under acidified sea water. Our study provides important data for understanding the shell repair process and proteomic response of Mytilus under ocean acidification, and providing insights into potential adaptation of mussels to future global change.

Parental exposure to ocean acidification impacts gamete production and physiology but not offspring performance in Nematostella vectensis.

Ocean acidification (OA) resulting from anthropogenic CO2 emissions is impairing the reproduction of marine organisms. While parental exposure to OA can protect offspring via carryover effects, this phenomenon is poorly understood in many marine invertebrate taxa. Here, we examined how parental exposure to acidified (pH 7.40) versus ambient (pH 7.72) seawater influenced reproduction and offspring performance across six gametogenic cycles (13 weeks) in the estuarine sea anemone Nematostella vectensis. Females exhibited reproductive plasticity under acidic conditions, releasing significantly fewer but larger eggs compared to ambient females after 4weeks of exposure, and larger eggs in two of the four following spawning cycles despite recovering fecundity, indicating long-term acclimatization and greater investment in eggs. Males showed no changes in fecundity under acidic conditions but produced a greater percentage of sperm with high mitochondrial membrane potential (MMP; a proxy for elevated motility), which corresponded with higher fertilization rates relative to ambient males. Finally, parental exposure to acidic conditions did not significantly influence offspring development rates, respiration rates, or heat tolerance. Overall, this study demonstrates that parental exposure to acidic conditions impacts gamete production and physiology but not offspring performance in N. vectensis, suggesting that increased investment in individual gametes may promote fitness.

Probabilistic extreme SST and marine heatwave forecasts in Chesapeake Bay: A forecast model, skill assessment, and potential value

We test whether skillful 35-day probabilistic forecasts of estuarine sea surface temperature (SST) are possible and whether these forecasts could potentially be used to reduce the economic damages associated with extreme SST events. Using an ensemble of 35-day retrospective forecasts of atmospheric temperature and a simple model that predicts daily mean SST from past SST and forecast atmospheric temperature, we create an equivalent ensemble of retrospective SST forecasts. We compare these SST forecasts with reference forecasts of climatology and damped persistence and find that the SST forecasts are skillful for up to two weeks in the summer. Then, we post-process the forecasts using nonhomogeneous Gaussian regression and assess whether the resulting calibrated probabilistic forecasts are more accurate than the probability implied by the raw model ensemble. Finally, we use an idealized framework to assess whether these probabilistic forecasts can valuably inform decisions to take protective action to mitigate the effects of extreme temperatures and heatwaves. We find that the probabilistic forecasts provide value relative to a naive climatological forecast for 1-2 weeks of lead time, and the value is particularly high in cases where the cost of protection is small relative to the preventable losses suffered when a heatwave occurs. In most cases, the calibrated probabilistic forecasts are also more valuable than deterministic forecasts based on the ensemble mean and naive probabilistic forecasts based on damped persistence. Probabilistic SST forecasts could provide substantial value if applied to adaptively manage the rapid impacts of extreme SSTs, including managing the risks of catch-and-release mortality in fish and Vibrio bacteria in oysters.

Microplastics in Seawater, Sediment, and Organisms from Hangzhou Bay

Microplastics (MPs) are widely present in global oceans, and can pose a threat to marine organisms. This study examined the abundance and characteristics of MPs in seawater, sediment, and organism samples collected from Hangzhou Bay. Abundance of MPs in seawater (n = 26) and sediment (n = 26) were 0.77–9.6 items/m3 and 44–208 items/kg dw, respectively. Size of MPs in sediment (mean 2.5 mm, range 0.21–5.3 mm) was significantly (p < 0.05) larger than that in seawater (1.1 mm, 0.13–4.9 mm). Fiber was consistently the predominant shape of MPs in seawater and sediment. The major polymer composition of MPs was polyethylene (PE; mean 47 %) in seawater, but textile cellulose (60 %) was the main polymer type of MPs in sediment. Average abundance of MPs in marine organisms (n = 388) ranged from 0.064 (zooplankton) to 2.9 (Harpodon nehereus) items/ind, with the mean size of 0.19–1.4 mm. MP abundance in marine organisms was not significantly correlated with their trophic level. Fiber was always the predominant shape of MPs in different marine organisms, contributing mean 67 (fish)–93 % (zooplankton) of total MPs. MPs in crustacean (mean 58 %), shellfish (64 %), and cephalopod (29 %) were dominated by textile cellulose. Whereas, PE (mean 44 %) and polypropylene (43 %) were the major polymer compositions of MPs in fish and zooplankton, respectively. To our knowledge, this is the most comprehensive study investigating the occurrence of MPs in environmental matrixes from Hangzhou Bay, which contributes to the better understanding of environmental behaviors of MPs in estuarine sea environment.

Nematostella vectensis exhibits an enhanced molecular stress response upon co-exposure to highly weathered oil and surface UV radiation

Crude oil released into the environment undergoes weathering processes that gradually change its composition and toxicity. Co-exposure to petroleum mixtures and other stressors, including ultraviolet (UV) radiation, may lead to synergistic effects and increased toxicity. Laboratory studies should consider these factors when testing the effects of oil exposure on aquatic organisms. Here, we study transcriptomic responses of the estuarine sea anemone Nematostella vectensis to naturally weathered oil, with or without co-exposure to environmental levels of UV radiation. We find that co-exposure greatly enhances the response. We use bioinformatic analyses to identify molecular pathways implicated in this response, which suggest phototoxicity and oxidative damage as mechanisms for the enhanced stress response. Nematostella's stress response shares similarities with the vertebrate oxidative stress response, implying deep conservation of certain stress pathways in animals. We show that exposure to weathered oil along with surface-level UV exposure has substantial physiological consequences in a model cnidarian.

Water Exchange Between the Gulf of Ob and the Kara Sea During Ice-Free Seasons: The Roles of River Discharge and Wind Forcing

The Gulf of Ob is among the largest estuaries in the World Ocean in terms of area, watershed basin, and freshwater discharge. In this work, we describe the roles of river discharge and wind forcing on the water exchange between the Gulf of Ob and the Kara Sea during ice-free seasons. This work is based on the extensive in situ measurements performed during 10 oceanographic surveys in 2007–2019. Due to large river runoff (∼530 km3 annually) and low tidal forcing (&amp;lt;0.5 m/s), the estuarine processes in the Gulf of Ob during the ice-free season are generally governed by gravitational circulation. Local wind forcing significantly affects general estuarine circulation and mixing only in rare cases of strong winds (∼10 m/s). On the other hand, remote wind forcing over the central part of the Kara Sea regularly intensifies estuarine—sea water exchange. Eastern winds in the central part of the Kara Sea induce upwelling in the area adjacent to the Gulf of Ob, which increases the barotropic pressure gradient between the gulf and the open sea. As a result, intense and distant (120–170 km) inflows of saline water to the gulf occur as compared to the average conditions (50–70 km). Remote wind forcing has a far stronger impact on saltwater intrusion into the Gulf of Ob than the highly variable river discharge rate. In particular, saltwater reaches the shallow central part of the gulf only during upwelling-induced intense inflows. In the other periods (even under low discharge conditions), fresh river water occupies this area from surface to bottom. The upwelling-induced intense inflows occur on average during a quarter of days (July to October) when the gulf is free of ice. They substantially increase the productivity of phytoplankton communities in the gulf and modify the taxa ratio toward the increase of brackish water species and the decrease of freshwater species.

Temporal and Spatial Variability Scales of Salinity at a Large Microtidal Estuary

The Río de la Plata is a large fluvial–estuarine–sea system discharging into the southwestern Atlantic Ocean, which has relevant features such as high fluvial discharge, microtidal astronomical tidal scales, a relevant meteorological tide, and a strong atmospheric forcing effect, due to its large width. The objective of this study is to advance the understanding of the estuarine hydrodynamics and salt transport, as well as discussing the main characteristics of the spatiotemporal variability of the salinity field. To achieve this, the results of a 3D model of the Río de la Plata and its maritime front were used, simulating an extensive period of 10 years. In this study, the model was validated using vertical salinity profiles collected at different locations in the estuary. The temporal variability of the salinity stratification was characterised at different temporal scales: annual, monthly, and storm. At the same time, the influences of fluvial flow and winds were determined. The correlation analysis between fluvial flow and the salinity field showed that high annual fluvial flows generate an extension of the freshwater area, with larger longitudinal salinity gradients and a shift of the salinity front towards the ocean. The tendency at the monthly scale is not as clear as that observed at the annual scale. The results show that the effect of a storm coming from the northwest is quite similar to that of storms coming from the southwest, especially in the central and southern zones of the Río de la Plata, where mixing increases and stratification decreases, according to the intensity of the storm. The effect of south–southeasterly storms increases the mixing process and reduces stratification; the opposite effect was identified with respect to northeasterly storms, under the influence of which the stratified area increases. Synthesising the obtained results, a global zonification of the vertical salinity stratification for the Río de la Plata is proposed.

Differential Tolerance and Seasonal Adaptation to Temperature and Salinity Stress at a Dynamic Range Boundary Between Estuarine Gastropods.

AbstractInsight into how coastal organisms will respond to changing temperature and salinity regimes may be derived from studies of adaptation to fluctuating estuarine environments, especially under stressful range-edge conditions. We characterized a dynamic range boundary between two estuarine sea slugs, Alderia modesta (distributed across the North Pacific and North Atlantic) and Alderia willowi, known from southern and central California. The species overlap from Bodega Bay to San Francisco Bay, where populations are dominated by A. modesta after winter rains but by A. willowi after peak summer temperatures. Laboratory assays confirmed superior tolerance to low salinity for the northern species, A. modesta: encapsulated embryos developed at 8 ppt, larvae survived at 4-6 ppt, and adults survived repeated exposure to 2 ppt, salinities that reduced development or survival for the same stages of A. willowi. Adults did not appreciably differ in their high-temperature threshold, however. Each species showed increased tolerance to either temperature or salinity stress at its range margin, indicating plasticity or local adaptation, but at the cost of reduced tolerance to the other stressor. At its northern limit, A. willowi became more tolerant of low salinity during the winter rainy season, but also less heat tolerant. Conversely, A. modesta became more heat resistant from spring to summer at its southern limit, but less tolerant of low salinity. Trade-offs in stress tolerance may generally constrain adaptation and limit biotic response to a rapidly changing environment, as well as differentiating species niches.

Adaptive and Plastic Responses to Environmental Variation: Introduction to a Virtual Symposium in The Biological Bulletin.

Adaptive and Plastic Responses to Environmental Variation: Introduction to a Virtual Symposium in The Biological Bulletin.

Measuring mutual movements, mixing, and mingling among multiple mangrove bays by an important estuarine sea bream (Archosargus rhomboidalis)

Quantifying the spatial and temporal aspects of fish residency is needed to understand energy transfer, habitat function, contaminant exposure, and effective design of MPAs in estuarine systems. The spatial and temporal movements of 19 sea bream (Archosargus rhomboidalis), an ecologically important species in mangrove estuaries of the western Atlantic, were investigated in multiple bays on a Caribbean Island over two years using surgically implanted acoustic transmitters. Fish were almost continuously monitored (residency index 96–100%) by an array of hydrophones during the 11–13 month battery-life of their transmitters. Individual fish utilized small core areas (mean = 9.8 ha during daytime and 11.0 ha at night), displayed daily site fidelity (mean = 57% overlap in day night core area), showed no evidence of an ontogenetic increase in core habitat size, and many exhibited a change in the bays utilized during winter months which is coincident with suspected spawning. Fish captured from the same bay generally occupied the same spaces within the study area, and in similar proportions, compared to fish captured in adjacent bays. Fish from different bays did not mix and wander throughout the ecosystem even though it is all suitable habitat and is used by different groups of localized individuals. This similarity of occupancy patterns is limited to the spatial scale of bays and temporal scales of weeks or months. When considered at the resolution of individual receivers and hourly time steps, most fish are not in close proximity to one another for the vast majority of the time. Although some pairs of fish had as many as 84% of their hourly detections on the same receivers in the month after tagging, they gradually spent less time near each other, even though their overall pattern of movements was consistent at the scale of whole bays. This highlights the importance of examining movements of fish on multiple spatial scales and time-intervals to understand their interactions.

Research on Optimal Allocation of Sea Area Utilization Based on Genetic Algorithm: A Case Study of Dengsha Estuary Sea Area

Optimal allocation of sea area utilization is a necessary method to coordinate the conflicts between different departments and realize the dual goals of development and ecological protection. This paper presents an optimal allocation method of sea area utilization based on genetic algorithm. Taking the estuarine sea area of Dengsha Estuary Sea Area as an example, the empirical study was conducted. The results show that the sea area utilization optimization allocation method based on genetic algorithm can produce the optimization result scheme with higher comprehensive benefit and lower ecological loss based on the initial scheme. Under the guidance of constraint conditions, the problem of conflicts between different departments can be solved by optimizing the spatial distribution and the demand of each department can be fully met. Different spatial distribution optimization alternatives can be produced under the same sea area utilization structure.

Thermal exposure and transgenerational plasticity influence embryonic success in a bivoltine estuarine sea hare

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 634:199-211 (2020) - DOI: https://doi.org/10.3354/meps13207 Thermal exposure and transgenerational plasticity influence embryonic success in a bivoltine estuarine sea hare Richelle L. Tanner1,2,5,*, Rauri C. K. Bowie1,3, Jonathon H. Stillman1,2,4 1Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA 2Estuary and Ocean Science Center, San Francisco State University, Tiburon, CA 94920, USA 3Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA 94720, USA 4Department of Biology, San Francisco State University, San Francisco, CA 94132, USA 5Present address: School of Biological Sciences, Washington State University, Pullman, WA 99163, USA *Corresponding author: richelle.tanner@richelletanner.com ABSTRACT: Phenotypic plasticity has the potential to influence environmental adaptation on extremely short evolutionary timescales. Transgenerational plasticity (TGP) allows parents to provision their offspring for rapid environmental shifts in as little as one generation. We hypothesized that organisms that produce multiple generations of offspring each year use TGP to maximize their fitness under predictable fluctuations in seasonal environments. Using the direct-developing bivoltine eelgrass sea hare Phyllaplysia taylori as a test case, we examined the impacts of seasonal thermal variation (i.e. average temperature and acute heat stress) on physiological tolerance, maternal provisioning, and developmental plasticity across multiple generations. In the laboratory, we acclimated seasonally acclimatized adults from successive generations at 13, 17, and 21°C in order to assess plasticity of thermal tolerance limits. We also examined the effects of thermal acclimation and heat stress on reproductive output within a single generation in order to characterize TGP. Physiological plasticity, including but not limited to TGP, successfully maintained the viability of offspring under 2 seasonal conditions regularly experienced in the wild, despite differences in the density of offspring per clutch and large individual differences in offspring numbers under these conditions. These results indicate that warmer conditions (21°C) disrupt current patterns of plasticity and warrant further investigation of the long-term effects of chronic stress on TGP under climate change. KEY WORDS: Phyllaplysia taylori · Physiological plasticity · Seasonal variation · Estuarine invertebrate · Thermal tolerance Full text in pdf format Supplementary material PreviousNextCite this article as: Tanner RL, Bowie RCK, Stillman JH (2020) Thermal exposure and transgenerational plasticity influence embryonic success in a bivoltine estuarine sea hare. Mar Ecol Prog Ser 634:199-211. https://doi.org/10.3354/meps13207 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 634. Online publication date: January 23, 2020 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2020 Inter-Research.

Dynamic remodeling of the interactomes of Nematostella vectensis Hsp70 isoforms under heat shock

Heat shock protein 70s (Hsp70s) are a highly conserved class of molecular chaperones that fold a large proportion of the proteome. Nematostella vectensis (Nv) is an estuarine sea anemone that has emerged as a model species to characterize molecular responses to physiological stressors due to its exposure to diverse, extreme abiotic conditions. Previous transcriptional data has shown dramatic differences among expression profiles of three NvHsp70 isoforms (NvHsp70A, B and D) under stress but it is unknown if, and to what extent, the client proteins for these chaperones differ. In order to determine client specificity, NvHsp70A, B and D were expressed in Saccharomyces cerevisiae budding yeast lacking native Hsp70 and interacting proteins for each Hsp70 were determined with mass spectrometry in yeast ambient and heat shock conditions. Our analyses showed <50% of identified interacting proteins were common to all three anemone Hsp70s and 3–18% were unique to an individual Hsp70. Mapping of temperature induced interactions suggest that under stress a proportion of clients are transferred from NvHsp70A and NvHsp70D to NvHsp70B. Together, these data suggest a diverse set of interacting proteins for Hsp70 isoforms that likely determines the precise functions for Hsp70s in organismal acclimation and potentially adaptation. Biological significanceAlthough the Hsp70 family of molecular chaperones has been studied for >50 years, it is still not fully understood why organisms encode and express many highly-similar Hsp70 isoforms. The prevailing theory is that these isoforms have identical function, but are expressed under unique cellular conditions that include heat shock to cope with increased number of unfolded/misfolded proteins. The sea anemone Nematostella vectensis encodes three Hsp70 isoforms A, B and D that when expressed in yeast demonstrate unique functionalities. This study provides the interactome of NvHsp70s A, B and D and demonstrates that Hsp70 isoforms, while highly similar in sequence, have unique co-chaperone and client interactors.

Vulnerability of a semienclosed estuarine sea to ocean acidification in contrast with hypoxia

AbstractThe Strait of Georgia (SoG) is a large semienclosed estuary that spatially dominates the Salish Sea on the North American Pacific coast. The region is well populated, harbors significant aquaculture, and is vulnerable to climate change. We present the first inorganic carbon data collected in the SoG covering all seasons (2003 and 2010–2012) and put them into the context of local circulation and oxygen cycles. Results show that the SoG has a higher carbon content and lower pH than surrounding waters. Aragonite saturation horizons in the SoG do not become deeper than 20–30 m and shoal to the surface for extended periods. Furthermore, incoming upwelled “acidified” water from the outer coast actually increases local pH. Finally, intense mixing in the physically restricted channels connecting the SoG to the outer coast allows significant oxygen uptake but minimal CO2 out gassing, protecting the SoG from hypoxia but not from ocean acidification.

Downwelling wind, tides, and estuarine plume dynamics

AbstractThe estuarine plume dynamics under a downwelling‐favorable wind condition were examined in the windy dry season of the Pearl River Estuary (PRE) using the PRE primitive‐equation Finite‐Volume Community Ocean Model (FVCOM). The wind and tide‐driven estuarine circulation had a significant influence on the plume dynamics on both local and remote scales. Specifically, the local effect of downwelling‐favorable winds on the plume was similar to the theoretical descriptions of coastal plumes, narrowing the plume width, and setting up a vertically uniform downstream current at the plume edge. Tides tended to reduce these plume responses through local turbulent mixing and advection from upstream regions, resulting in an adjustment of the isohalines in the plume and a weakening of the vertically uniform downstream current. The remote effect of downwelling‐favorable winds on the plume was due to the wind‐induced estuarine sea surface height (SSH), which strengthened the estuarine circulation and enhanced the plume transport accordingly. Associated with these processes, tide‐induced mixing tended to weaken the SSH gradient and thus the estuarine circulation over a remote influence scale. Overall, the typical features of downwelling‐favorable wind‐driven estuarine plumes revealed in this study enhanced our understanding of the estuarine plume dynamics under downwelling‐favorable wind conditions.

Trace metals in an urbanized estuarine sea turtle food web in San Diego Bay, CA

San Diego Bay is an anthropogenically impacted waterway that is also a critical habitat for many sensitive species such as the green sea turtle (Chelonia mydas). In this study, we quantified trace metal concentrations in sediment and organisms composing the green sea turtle diet, and identified bioaccumulation patterns for a suite of trace metals. We found Ag, Cd, Cu, Mn, Se, and Zn exhibited the highest bioaccumulation levels in this food web. Cu and Mn concentrations in resident biota displayed a strong spatial gradient from the mouth to the head of the Bay, which was different from the patterns found in the sediment itself. Sediment median concentrations followed a general pattern across the bay of Al>Mn>Cu≈Zn>Pb>As>Cd>Ag>Se>Hg. In contrast, eelgrass displayed differential patterns in the mouth versus the back of the Bay (three front Bay sites: Al>Mn>Zn>Cu>Pb>Se>Cd≈Ag>As; five back Bay sites: Mn>Al>Zn>Cu>Pb≈Se>Cd>Ag>Hg>As) with the exception of Shelter Island where levels of Zn and Cu were elevated as a result of anti-fouling paint pollution. Observed differences between sediment and biota metal patterns are likely due to complex processes related to trace metals input and bioavailability, habitat characteristics and specific metabolic functioning of the trace metals for each member of the food web. These data highlight the fact that for the San Diego Bay ecosystem, the current use of toxicity reference values scaled up from sediment and invertebrate testing ex-situ is likely to be inaccurate when transposed to the green sea turtle. Here, we illustrate how identifying spatial variability in metal exposure can improve our understanding of habitat utilization by sea turtles in highly urbanized estuaries. Monitoring contaminants directly in food webs of sensitive vertebrates may greatly improve our understanding of their direct and indirect exposure to potentially deleterious contamination, and should be considered in the future to improve traditional risk assessment approaches.

INCREASED OVERTOPPING SECURITY OF DYKES: A POTENTIAL FOR COMPENSATING FUTURE IMPACTS OF CLIMATE CHANGE

Anticipated acceleration of sea level rise in combination with expected higher set-up of storm surges will require strengthening of coastal protection structures. Dykes e. g. must then be heightened according to the existing design rules taking only hydrodynamical loads into consideration. Alternatively the development of new design rules taking both hydrodynamical loads and the strength of the available soil for the construction of a dyke might allow the explo-ration of up to now undetected safety margins. In order to explore these possibilities the German Coastal Engineering Research Council has provided the funds for a research project targeting these aims. First results of this project are presented in this paper on the background of achieved improvements for the determination of design wave run-up on coastal and estuarine sea dykes.

Trends in Total Phosphorus Loadings and Concentrations Regarding Surface Waters of the Baltic Sea, 1968-2007

The Baltic Sea, a large estuarine sea in northern Europe, has for many decades displayed obvious signs of an- thropogenic eutrophication. This study relates long-term trends in total phosphorus (TP) loadings and TP concentrations in surface waters regarding five major sub-basins of the Baltic Sea; the Bothnian Bay, the Bothnian Sea, the Baltic Proper, the Gulf of Finland and the Gulf of Riga. The longest time series ever published on these variables was developed and used for this purpose. TP loadings to these waters have decreased greatly and significantly since the 1980s. However, TP concentrations have only decreased slightly in one of the sub-basins while concentrations have increased in the other four basins. Four possible hypotheses about the weak connection between TP loadings and concentrations are 1) increasing TP concentration is a delayed effect from many decades of intensive TP loading, 2) fewer saline inflows of high intensity have decreased sedimentation rates and increased TP concentrations, 3) fewer oxygen-rich saline inflows of high intensity have increased TP diffusion from deep sediments to the whole water column and 4) less ice in the winter has increased the erosion and resuspension of shallow sediments and increased TP concentrations.

Discovering SNPs in Protein Coding Regions with StellaSNP: Illustrating the Characterization and Geographic Distribution of Polymorphisms in the Estuarine Anemone Nematostella vectensis

Single-nucleotide polymorphisms (SNPs) can be used to study the nucleotide diversity both within and between species. Furthermore, as some SNPs impact organismal phenotype, characterizing SNPs can provide insights into the relationship between genotype and phenotype and the adaptive evolution of populations. Model systems that combine a large quantity of available sequence data (e.g., large-scale expressed sequence tag (EST) sequencing projects) with diverse natural environ- ments provide potent opportunities to investigate the evolution of adaptive nucleotide polymorphism in the wild. We developed a relational database of SNPs from 17,108 ESTs for the estuarine sea anemone Nematostella vectensis (www.stellabase.org/SNP). In these ESTs, we identified 20,063 candidate SNPs in 3,233 assembled contigs. Of these SNPs, 555 can be regarded with a high degree of confidence because the nucleotide variants occurring at that position were observed in at least two different ESTs. All 555 of these high-confidence SNPs were scored with respect to their location in coding or noncoding regions. Three hundred forty-three SNPs were within coding regions, 78 of which were nonsynonymous polymorphisms. We sequence-confirmed and analyzed the distribution of three nonsynonymous polymorphisms—one that occurs in the highly conserved homeodomain of the transcription factor tlx and two that occur in a deiodinase gene.

Modeling diagnosis of suspended sediment transport in tidal estuarine system

A three-dimensional, time-dependent hydrodynamic and suspended sediment transport model was performed and applied to the Danshuei River estuarine system and adjacent coastal sea in northern Taiwan. The model was validated with observed time-series salinity in 2001, and with salinity and suspended sediment distributions in 2002. The predicted results quantitatively agreed with the measured data. A local turbidity maximum was found in the bottom water of the Kuan-Du station. The validated model then was conducted with no salinity gradient, no sediment supply from the sediment bed, wind stress, and different freshwater discharges from upstream boundaries to comprehend the influences on suspended sediment dynamics in the Danshuei River estuarine system. The results reveal that concentrations of the turbidity maximum simulated without salinity gradient are higher than those of the turbidity maximum simulated with salinity gradient at the Kuan-Du station. Without bottom resuspension process, the estuarine turbidity maximum zone at the Kuan-Du station vanishes. This suggests that bottom sediment resuspension is a very important sediment source to the formation of estuarine turbidity maximum. The wind stress with northeast and southwest directions may contribute to decrease the suspended sediment concentration. When the freshwater discharges increase at the upstream boundaries, the limits of salt intrusion pushes downriver toward river mouth. Suspended sediment concentrations increase at the upriver reaches in the Danshuei River to Tahan Stream, while decrease at Kuan-Du station.