Inland Brackish Water Research Articles

Recovery of fresh water and minerals from inland brackish desalination brine via persulfate-based photochemical treatment and demineralization

Managing inland brackish desalination brine is challenging but critical to future water security. This study investigated the use of a treatment train with an ultraviolet persulfate (UV/PS) oxidative pre-treatment followed by chemical demineralization (CDM), microfiltration (MF), and secondary reverse osmosis (RO) to achieve antiscalant degradation, scale-forming constituent removal, mineral recovery, and fresh water recovery from an inland brackish RO brine. Results showed that the UV/PS pre-treatment efficiently degraded the phosphonate antiscalant ubiquitously present in the brine within 20 min of UV irradiation and improved mineral resource recovery from the brine in a subsequent CDM process. Analyses of the recovered minerals revealed that calcium, magnesium, and silica were the major chemical components, and calcite was a major crystallized mineral. The MF process successfully separated solid and liquid from the CDM process, and MF membrane fouling potential was significantly reduced with UV/PS-CDM treatment. The CDM process, coupled with UV/PS pre-treatment, mitigated membrane fouling and improved fresh water recovery during a subsequent RO step due to the lower magnesium and silica concentrations and the removal of phosphonate antiscalant. Over 40 % of total dissolved solids in the raw brine (>2.1 g⋅L−1) were recovered as mineral resources from the raw brine, and over 75 % fresh water recovery was achieved. The results demonstrated the benefits and applicability of a persulfate-based photochemical treatment followed by CDM, MF, and RO for inland brackish water brine treatment and recovery of additional water.

Comunidades de aves acuáticas de la laguna Mar Chiquita (Córdoba, Argentina)

Mar Chiquita is a large inland brackish water body of about 2,000 km2, with a salinity of around 100 °/oo. Its aquatic bird communities were studied throughout a year in three study areas, representative of the main habitat types found in the región. We collected information on species composition and abundance, as well as foraging behaviour, feeding site utilization and stomach contents.
 In total we recorded 55 species. The richest community (both in number o f species and individuals) was found around the Rio Segundo estuary, while the less diverse corresponde to saline ponds near the coast. Summer migrant species (long range neartic migrants) included nine species and accounted for the 21% of the observed birds. Winter visitors included five species and made up 1% of bird numbers. Ecological guilds species composition and patterns of resource utilization are analyzed. They closely resemble those of marine estuarine and intertidal conditions. At present, the main adverse factors for the preservation of the local aviiauna are linked with planned stream regime modifications through dam building, and contamination due to industrialdevelopment along tributary rivers.

Hybrid BWRO/FO system for high recovery in-land brackish water desalination: techno-economic assessment

Several hybrid Forward osmosis (FO) systems for seawater and brackish water desalination have been developed in recent years. This study investigates two approaches of integrated systems comprising brackish water reverse osmosis desalination (BWRO) and forward osmosis (FO) systems. These approaches aim to minimize the environmental effect of inland reject brine disposal while enhancing total water recovery. Experiments were performed using different draw solution (DS) concentrations of KCl and MgCl2.6H2O (0.5, 1, 1.5 and 2 Molar) to reach maximum recovery. In scheme (A), feed water is directed to BWRO with recovery 45% and 97% rejection, while the brine water is directed to the FO system as FS stream. In scheme (B), the feed water is divided into two streams, one of which is directed to the BWRO with recovery 75% and 98% rejection and the other stream is sent to the FO unit as FS stream. KCl DS displayed higher flux rate of an average 28.5 L/(m2.h) using 2 M concentration, while MgCl2.6H2O 2M solution shows an average flux of 23.5 L/(m2.h) during the first 100 min of operation. Scheme A shows 81% total system recovery, while scheme B shows 78% total system recovery. The cost indicators for desalination system with small capacity of 10 m3/d showed that scheme (A) has lower capital cost 55,732$ for scheme (A), while total capital cost was 59,400 $ for scheme (B).

Desalination concentrate microalgae cultivation: biomass production and applications

The environmental consequences of desalination concentrate disposal have limited the practical adoption of desalination systems for inland brackish water. Desalination concentrate, which is generated by desalination facilities, has the ability to offer water and nutrients for microalgal growth. A useful application for concentrate from desalination systems is required to boost the feasibility of installing desalination procedures for both inland brackish and seawater plants. Several research has been conducted to investigate the use of desalination concentrate as a medium for microalgal culture. This paper reviews the impact of desalination concentrate on microalgal productivity by describing instances of microalgae cultivated in desalination concentrate. Based on the research results, it was found that Chlorella vulgaris, Scendesmus quadricauda, S. platensis, Nannochloropsis oculata and Dunaliella tertiolecta can be cultivated on desalination brine. Also, the paper reviews the different applications of these types which may contribute to adding revenue that will reduce the cost of desalinated water.

Delineating the Crop-Land Dynamic due to Extreme Environment Using Landsat Datasets: A Case Study

Extreme climatic conditions and natural hazard-related phenomenon have been affecting coastal regions and riverine areas. Floods, cyclones, and climate change phenomena have hammered the natural environment and increased the land dynamic, socio-economic vulnerability, and food scarcity. Saltwater intrusion has also triggered cropland vulnerability and, therefore, increased the area of inland brackish water fishery. The cropland area has decreased due to low soil fertility; around 252.06 km2 of cropland area has been lost, and 326.58 km2 of water bodies or inland fishery area has been added in just thirty years in the selected blocks of the North 24 Parganas district, West Bengal, India. After saltwater intrusion, soil fertility appears to have been decreased and crop production has been greatly reduced. The cropland areas were 586.52 km2 (1990), 419.92 km2 (2000), 361.67 km2 (2010) and 334.46 km2 (2020). Gradually the water body areas were increased 156.21 km2 (1990), 328.15 km2 (2000), 397.77 km2 (2010) and 482.78 km2 (2020). The vegetated land area also decreased due to it being converted into inland fishery areas, and around 79.15 km2 were degraded during the last thirty years. The super cyclone Aila, along with other super cyclones and other environmental stresses, like water-logging, soil salinity, and irrigation water scarcity were the reasons for the development of the new fishery areas in the selected blocks. There is a need for proper planning for sustainable development of this area.

Comparative Evaluation of Patties Prepared from Pacific White Shrimps (Litopenaeus vannamei) Grown in Inland Saline Water and Brackish Water Regimes during Frozen Storage

ABSTRACT In this study, an attempt has been made to develop shrimp patties from inland saline water reared vannamei (ISRV) and compare its quality with that from brackish water reared vannamei (BWRV) under storage conditions at −18°C for 4 months. The patties prepared from ISRV had tantamount protein (21.69%), high ash (1.62%) and low fat (0.31%) content as compared with BWRV patties, which had protein, ash and fat content as 22.45%, 1.52% and 0.43% respectively. No significant difference was observed in sensory scores of the patties. Trimethylamine, total volatile base nitrogen, total viable bacterial count and staphylococcal count were significantly increasing during storage and are within the acceptable limits. Peroxide value and TBARS increased during storage and slightly higher values observed in ISRV. This study concluded that overall quality and shelf life of patties prepared from ISRV was comparable with BWRV and there is no significant effect observed under frozen conditions.

Limits of High Recovery Inland Desalination: Closed‐Circuit Reverse Osmosis – a Viable Option?

AbstractCost‐efficient operation of inland brackish water reverse osmosis (BWRO) demands a high recovery. As recovery of BWRO is often limited to scaling, antiscalants (AS) are applied, whose environmental impact is disputed. In this paper, different systems (conventional single‐ and two‐stage plug flow RO (PFRO) and closed‐circuit RO (CCRO)) were simulated in various configurations (AS dosing, ion exchange (IEX) pretreatment, elements per vessel) to determine the recovery limiting factor for a hard feed. The novel proposed IEX‐CCRO reached the highest recovery without AS dosing. PFRO configurations had lower recoveries, mainly due to hydraulic limitations. Utilizing RO brine reduced both the water demand and salts necessary for IEX regeneration.

Pretreatment of brackish water reverse osmosis (BWRO) concentrate to enhance water recovery in inland desalination plants by direct contact membrane distillation (DCMD)

Inland brackish water desalination plants typically rely on reverse osmosis (RO) for the production of drinking water. However, the usual water recovery in these plants (i.e., 50–75%) results in fairly large quantities of the reject (concentrate) stream that needs to be disposed at considerable cost and with significant adverse environmental impacts. Membrane distillation (MD) offers a unique opportunity to improve the performance of these brackish water reverse osmosis (BWRO) plants by recovering additional clean permeate and reducing the volume of concentrate for disposal. In this study, barite precipitation was utilized to remove about 4000 mg/L of sulfate from actual BWRO concentrate to prevent interference with MD operation. The effect of barium concentration and mixing condition was evaluated for its impact on the removal of sulfate as the key ingredient of inorganic scales that would form in BWRO concentrate with increased water recovery. The pre-treated BWRO concentrate was used as feed in direct contact membrane distillation (DCMD) system operated at 60 °C to achieve at least 85% water recovery. The impact of concentration polarization on the performance of MD explored in a system operated at 80 °C revealed a potential for amorphous silica fouling of the membrane.

Significance of isotopic and geochemical methods to determine the evolution of inland brackish and bitter water: An example from the Zuli river in the upper reaches of the Yellow River, China

AbstractWith the increasing demand for water resources, the utilization of marginal water resources of poor‐quality has become a focus of attention. The brackish water developed in the Loess Plateau is not only salty but also famous for its ‘bitterness’. In the present work, multi‐isotope analysis (Sr, B) was combined with geochemical analysis to gain insight into the hydrogeochemical evolution and formation mechanisms of brackish water. These results demonstrate that groundwater in the headwater is influenced by carbonate weathering. After the confluence of several tributaries in the headwater, the total dissolved solids (TDS) of water is significantly increased. The dissolution of evaporates is shown to be the main source of salinity in brackish water, which also greatly affects the strontium isotopic composition of water. This includes the dissolution of Mg‐rich minerals, which is the main cause of the bitterness. Furthermore, the release of calcium from the dissolution of gypsum may induce calcite precipitation and incongruent dissolution of dolomite, which also contributes to the enrichment of magnesium. The highly fractionated boron isotopic values observed in the upstream groundwater were explained by the absorption with clay minerals. The inflow of brackish groundwater is the source of river water. Then evaporation further aggravates the salinization of river water, with water quality evolving to saline conditions in the lower reach. When the river reaches the valley plain, the 87Sr/86Sr ratios decreases significantly, which is primarily related to erosion of the riverbanks during runoff. These results indicate that water resource sustainability could be enhanced by directing focus to mitigating salinization in the source area of the catchment.

The Impact of Water Intrusion on Pathogenic Vibrio Species to Inland Brackish Waters of China.

The estuary is the ecological niche of pathogenic Vibrio spp. as it provides abundant organic and inorganic nutrients from seawater and rivers. However, little is known about the ecology of these Vibrio species in the inland brackish water area. In this study, their co-occurrence and relationships to key environmental constraints (salinity and temperature) in the Hun-Tai River of China were examined using the most probable number polymerase chain reaction (MPN-PCR) approach. We hereby report 2-year continuous surveillance based on six water indices of the Hun-Tai River. The results showed that seawater intrusion maximally reached inland as far as 26.5 km for the Hun-Tai River. Pathogenic Vibrio spp. were detected in 21.9% of the water samples. In particular, V. cholerae, V. parahaemolyticus, and V. vulnificus were isolated in 10 (10.4%), 20 (20.8.5%), and 2 (2.08%) samples, respectively. All V. parahaemolyticus strains were tdh gene negative, 10% were positive for the trh gene. Multi-locus sequence typing (MLST) divided V. parahaemolyticus strains into 12 sequence types (STs) for the Hun-Tai River. Five STs were respectively present in various locations along the Hun-Tai River. The PCR assay for detecting six virulence genes and Vibrio seventh pandemic island I and II revealed three genotypes in 12 V. cholerae isolates. The results of our study showed that seawater intrusion and salinity have profound effects on the distribution of pathogenic Vibrio spp. in the inland river, suggesting a potential health risk associated with the waters of the Hun-Tai River used for irrigation and drinking.

A catalogue and bibliography of non-marine (freshwater and estuarine) Rhodophyta (red algae) of India

An annotated bibliographic catalogue of Indian red algae (Rhodophyta) occurring in freshwater and estuarine habitats (moist terrestrial soils, ponds, streams, rivers, lakes, large inland brackish water lagoons and coastal estuaries), based on more than a century (1846 to 2017) of publications is presented in a single coherent work for the first time. There have been 81 taxonomic entities (species, varieties and doubtful records), distributed among 21 genera recorded for the vast Indian sub-continent. Species distribution among the 21 genera are as follows: Audouinella—12; Balliopsis—1; Batrachospermum—11; Bostrychia—7; Caloglossa—8; Catenella—3; Chroodactylon (including Asterocytis)—2; Chroothece—1; Compsopogon—8, Compsopogonopsis—1; Hildenbrandia—1; Kumanoa—7; Kyliniella—1; Lemanea—6; Nothocladus—1; Polysiphonia—1; Porphyridium—1; Sheathia—1; Sirodotia—4; Thorea—2; and Tuomeya—2. Of the seven currently recognized classes of Rhodophyta, no members of Bangiophyceae, Cyaniodiophyceae, or Rhodellophyceae are recorded from India. For each taxon, the following information is provided: (i) valid and currently accepted binomial (ii) synonyms as applicable to Indian records (iii) references with distribution in India and (iv) brief notes. Descriptions of new species based on Indian collections (holotypes) are indicated and some new combinations were made, when necessary. Several generic records (e.g., Balliopsis, Hildenbrandia, Kyliniella, Nothocladus and Tuomeya) and some species records (e.g. Batrachospermum longiarticulatum, Lemanea australis, L. catenata, L. fluviatilis, L. mamillosa, L. torulosa and Thorea hispida) warrant detailed confirmatory data based on reinvestigation of fresh collections for morphology, reproduction and particularly molecular data to confirm the presence in the country. Future collections, especially in the Indian Biodiversity Hotspots (Indo-Burma, Western and Eastern Ghats and Andaman & Nicobar Islands), may uncover the occurrence of genera such as Bangia, Cyanidium and Nemalionopsis known to be present in neighbouring countries of Pakistan, Nepal and Thailand. Geothermal (acidic) hot water springs in India may reveal the presence of extremophilic unicellular red algal genera like Cyanidium, Cyanidioschyzon and Galdieria of the Cyanidiophyceae. Two maps showing the political and biogeographic zones of India are included. The need to preserve holotype and duplicate/voucher specimens with GPS data of future collections of red algal groups in a centralized national facility is also highlighted.

Spawning time of Atlantic herring (Clupea harengus) populations within a restricted area reflects their otolith growth at the larval stage

Larval growth from three putative populations was estimated by microstructure analysis of otoliths of four year classes of adult herring sampled over a wide spawning season (February-June) in and around an inland brackish water lake (Landvikvannet) in southern Norway during the years 2012–2015. Mean width of daily increments at distances between 20 and 170μm from the otolith core were significantly higher in Landvik herring (peak spawning in May) compared with the two other populations, Coastal Skagerrak spring spawners (peak spawning in March-April) and Norwegian spring spawning herring (peak spawning in February-March). These population differences were observed for all studied year classes and years and highly consistent with expected temperature dependent larval growth based on timing of successive spawning events. The observed patterns imply that timing of spawning was population specific with a tendency of adult herring to spawn at the same time and under the same conditions as they hatched themselves. This was also supported by vertebral counts, which are negatively correlated with temperatures during the embryonic stage. Firstly, Landvik herring which experienced higher ambient temperature during the embryonic stage were characterised by significantly lower counts than herring from the two other populations. Secondly, daily otolith growth also tended to decrease with increasing vertebral counts within the populations. The present study signifies the importance of otolith growth history for population discrimination in herring, even within the same spawning season, and further supports the use of vertebral counts in the continuous discussion on herring population structure, assessment and management.

Heliozoa (Centrohelea, Haptista, Hacrobia) of saline and brackish water bodies and watercourses of Russia

The species composition of centrohelid heliozoa (Centrohelida) in saline and brackish inland water bodies and watercourses with salinity 2.0–42.2‰ was studied in the subarid zone of Russia. Nine species (Polyplacocystis ambigua, Pterocystis foliacea, Choanocystis ebelii, Acanthocystis astrakhanensis, A. dentata, A. myriospina, A. pectinata, A. taurica, A. turfacea) are new for saline and brackish inland waters. A. astrakhanensis and A. taurica are new for the fauna of Orenburg region. The first data on centrohelidian fauna in saline rivers of Elton region were obtained. The fauna comprises Polyplacocystis ambigua, Pterocystis foliacea, A. turfacea and Choanocystis ebelii. C. ebelii is new for the protist fauna of Russia. Five species (Polyplacocystis ambigua, Pterocystis foliacea, A. pectinata, A. dentata, A. taurica) were recorded for the first time in saline and brackish waters and described as eurihaline. Morphological diagnoses of Acanthocystis dentata and A. taurica were completed.

Relative contributions of organic and inorganic fouling during nanofiltration of inland brackish surface water

Bench-scale nanofiltration (NF) experiments were performed with two commercially available membranes having different ion rejection characteristics to assess dominant fouling mechanisms during inland brackish surface water desalination and the role of rejection on flux decline. The Foss Reservoir in the state of Oklahoma, USA was used as a representative natural brackish surface water source in these experiments. Both nanofilters rejected divalent cations to a very high extent (Mg>94% and Ca>92%) but exhibited substantially different rejections of monovalent cations (e.g. Na removals of 60% and 97%). A model solution formulated to have a similar ionic composition as the natural water but with no added natural organic matter (NOM) was also employed to isolate mineral scaling effects. The low monovalent ion rejecting membrane was predominantly fouled by NOM with only limited contributions from calcium carbonate scaling. In contrast, electron microscopy along with infrared and X-ray photoelectron spectroscopy revealed that both NOM and gypsum were major foulants for the membrane that highly rejected both mono- and divalent ions. The exacerbated flux decline for the more salt-rejecting nanofilter was attributed to the synergistic effects of NOM and gypsum on fouling coupled with the formation of a very compact organic foulant layer due to greater extent of Ca-NOM interactions and the higher ionic strength of the concentration polarization layer. These results demonstrate that the relative contributions of NOM and mineral scaling to flux decline during brackish surface water NF depends on membrane ion rejection characteristics. Hence, optimal membrane selection needs to balance total dissolved solids concentration of the product water with the need to minimize fouling.

Defect engineered visible light active ZnO nanorods for photocatalytic treatment of water

Photocatalytic degradation of organic wastes and microbes in water using solar light is a green technology that requires the design of visible light active photocatalysts. Here we report the fabrication of visible light active zinc oxide nanorods (ZnO NRs), wherein the visible light absorption is enhanced by modulating the surface defects on the NRs. Oxygen vacancies in the NRs as characterized by photoluminescence and X-ray photoelectron spectroscopy are controlled by annealing at different temperatures in the ambient. The role of surface defects on the visible light photocatalytic degradation of an organic dye, industrial waste, bacterial culture and inland brackish water is studied. Results presented here provide a simple strategy to make the wide bandgap ZnO NRs visible light active, enabling their use for the photocatalytic decontamination of water.

Performance evaluation of reverse osmosis (RO) pre-treatment technologies for in-land brackish water treatment

Integration of renewable energy with desalination technologies has emerged as an attractive solution to augment fresh water supply sustainably. Fouling and scaling are still considered as limiting factors in membrane desalination processes. For brackish water treatment, pre-treatment of reverse osmosis (RO) feed water is a key step in designing RO plants avoiding membrane fouling. This study aims to compare at pilot scale the rejection efficiency of RO membranes with multiple pre-treatment options at different water recoveries (30, 35, 40, 45 and 50%) and TDS concentrations (3500, 4000, and 4500mg/L). Synthetic brackish water was prepared and performance evaluation were carried out using brackish water reverse osmosis (BWRO) membranes (Filmtec LC-LE-4040 and Hydranautics CPA5-LD-4040) preceded by 5 and 1μm cartridge filters, 0.02μm ultra-filtration (UF) membrane, and forward osmosis (FO) membrane using 0.25M NaCl and MgCl2 as draw solutions (DS). It was revealed that FO membrane with 0.25M MgCl2 used as a draw solution (DS) and Ultra-filtration (UF) membrane followed by Filmtec membrane gave overall 98% rejection but UF facing high fouling potential due to high applied pressure. Use of 5 and 1μm cartridge filter prior to Filmtec membrane also showed effective results with 95% salt rejection.

Characterization of reverse osmosis and nanofiltration membranes: effects of operating conditions and specific ion rejection

Reverse osmosis (RO) and nanofiltration (NF) are two of the most commonly used technologies for desalinating brackish and saline waters to provide potable water. However, there is still lack of a thorough comparison between these two methods providing the better option in different conditions. Therefore, in this paper, salt rejection and the effects of operation conditions on the performance of RO and NF systems are compared. Inlet water conductivity, inlet pH, permeate flow rate, temperature, and recovery rate are used as variable operating conditions, and permeate conductivity is considered as the target of comparison as it reflects the level of salts in product water. Five combinations of inland brackish water, drawn from wells located at the experimental site, were applied as different feed waters and five distinct types of membranes, three RO and two NF, were studied using pilot-scale equipment. To allow meaningful comparison among RO and NF membrane performances, identical hydrodynamic operating conditions and feed water chemistries were employed during tests. In both systems, negative rejection occurred for specific ions. The results suggest that the performances of RO and NF membranes (i.e. the amount of total dissolved salts remaining in produced water) are quite different. Based on the experimental data, new insights can be reached regarding the best choice of membrane, based on the minimization of electrical conductivity and the ability to reject specific ions in different operating conditions.

High-recovery electrodialysis reversal for the desalination of inland brackish waters

Since the inland disposal of large volumes of desalination concentrate is environmentally and financially impractical, a high-recovery desalination design is required to reduce concentrate volume. In practical applications, recovery is limited by scale formation from minimally soluble salts, which acids and antiscalant compounds can inhibit only temporarily. Therefore, the risk of scale formation, which is governed by the system’s electrochemical behavior, determines the high-recovery potential of desalination technologies. In this research, high recovery was investigated using a pilot-scale electrodialysis reversal (EDR) system and natural feedwaters from a deep aquifer at the Brackish Groundwater National Desalination Research Facility in Alamogordo, NM. Experiments were performed to identify the maximum permissible CaSO4 saturation levels during long-term, continuous operation with antiscalant dosing. The results indicated that EDR has enormous potential for treating CaSO4-rich inland brackish waters and that EDR may not be severely limited by the risk of scale formation in the hydrodynamic/concentration boundary layer. Long-term operation saturation indices were achieved, which were significantly greater than previously published values, and the system’s eventual failure point provides insight into the hypothesized operating conditions. Therefore, the obtained results for high-recovery inland brackish water EDR determined the highest permissible CaSO4 saturation index during long-term, continuous system operation.

Integrating tunable anion exchange with reverse osmosis for enhanced recovery during inland brackish water desalination.

For inland brackish water desalination by reverse osmosis or RO, concentrate or reject disposal poses a major challenge. However, enhanced recovery and consequent reduction in the reject volume using RO processes is limited by the solubility of ions present in the feedwater. One of the most common and stubborn precipitate formed during desalination is calcium sulfate. Reducing or eliminating the presence of sulfate would allow the process to operate at higher recoveries without threat to membrane scaling. In this research, this goal is accomplished by using an appropriate mixture of self-regenerating anion exchange resins that selectively remove and replace sulfate by chloride prior to the RO unit. Most importantly, the mixed bed of anion exchange resins is self-regenerated with the reject brine from the RO process, thus requiring no addition of external chemicals. The current work demonstrates the reversibility of the hybrid ion exchange and RO (HIX-RO) process with 80% recovery for a brackish water composition representative of groundwater in San Joaquin Valley in California containing approximately 5200 mg/L of total dissolved solids or TDS. Consequently, the reject volume can be reduced by 50% without the threat of sulfate scaling and use of antiscaling chemicals can be eliminated altogether. By appropriately designing or tuning the mixed bed of anion exchange resins, the process can be extended to nearly any composition of brackish water for enhanced recovery and consequent reduction in the reject volume.

Prymnesium parvum invasion success into coastal bays of the Gulf of Mexico: Galveston Bay case study

The toxic haptophyte Prymnesium parvum regularly forms fish-killing blooms in inland brackish water bodies in the south-central USA. Along the Texas coast smaller blooms have occurred in isolated areas. There appears to be an increasing risk that harmful P. parvum blooms will propagate into open coastal waters with implementation of future water plans. These plans will include increased interbasin water transfers from the Brazos River, regularly impacted by P. parvum blooms, to the San Jacinto-Brazos Coastal Basin, which ultimately flows into Galveston Bay (GB). Persisting source populations of P. parvum in inland waters elevates this risk. Thus, there is a need for an increased understanding of how P. parvum might perform in coastal waters, such as those found in GB. Here, two in-field experiments were conducted to investigate the influence of various plankton size-fractions of GB water on inoculated P. parvum during fall and winter, periods when blooms are typically initiating and developing inland. Stationary- and log-growth phase P. parvum were used to represent high and low toxicity initial conditions. Results revealed that P. parvum could grow in GB waters and cause acute mortality to silverside minnows (Menidia beryllina). Depending on season and growth phase, however, P. parvum growth and toxicity varied in different size fractions. During the fall, P. parvum inoculated from stationary-, but not log-growth phase culture, was negatively affected by bacteria-sized particles. During the winter, bacteria and nanoplankton together had a negative effect on P. parvum inoculated from stationary- and, to a lesser degree, log-growth phase cultures. Intermediate- and large-sized grazers when combined with bacteria and nanoplankton had complex relationships with inoculated P. parvum, sometimes stimulating and sometimes suppressing population growth. Toxicity to fish occurred in almost all plankton size fractions. The inclusion of progressively larger sized plankton fractions resulted in trends of decreased toxicity in treatments inoculated with stationary-, but not log-growth phase P. parvum in the fall. In the winter, however, inclusion of larger sized plankton fractions resulted in trends of increased toxicity to fish in treatments inoculated with both stationary- and log-growth phase P. parvum. This study indicates that understanding P. parvum population dynamics in open waters of estuaries and bays will be challenging, as there appears to be complex relationships with naturally occurring components of the plankton. The observations that P. parvum is able to grow to high population density and produce fish-killing levels of toxins underscores the need for advanced risk assessment studies, especially in light of water use plans that will result in P. parvum invasions of greater size.