Mid Salinity Research Articles

A comparison of intertidal metazoan biodiversity among different salinity zones of Louisiana coastal marshes

Tidal marshes are among the most valuable, productive, and vulnerable ecosystems with high biodiversity. Louisiana’s saltmarshes are endangered by natural and man-made stressors, including oil pollution, saltwater intrusion, and land loss due to sea level rise and erosion. Freshwater diversions have been planned to restore sediment input from the Mississippi River to rebuild marsh habitats in South Louisiana. These proposed diversions will undoubtedly change salinity levels, which is a major controlling factor in the distribution of marsh organisms, including those in soil; however, detailed pre-event inventories are lacking. This study describes the diversity of metazoan meiofauna (organisms between 45 and 500 μm) and environmental DNA in marsh soil collected in 2018 from Barataria and Caillou Bay, Louisiana, across three salinity zones and four distances from the marsh edge. Diversity analyses using 18S rRNA gene metabarcodes identified salinity as a factor impacting soil metazoan composition. Nematoda and Mollusca were equally distributed across salinity zones. Gastrotricha, Bryozoa, Rotifera, and Platyhelminthes were more prevalent in low salinity while Kinorhyncha were not detected in low salinity. Annelida and insects were equally common in low and high salinity but less in mid salinity. Five nematodes (Eumonhystera filiformis, two Prismatolaimus spp., Anoplostoma sp., and Prodorylaimus sp.), two annelids (Marionina southerni and Dendronereis aestuarina), two platyhelminthes (Rhynchoscolex simplex and Olisthanella truncula), the gastrotrich Chaetonotus novenarius and four collembola and ostracods appear to be low salinity bioindicators and are expected to expand range with freshwater diversions. No frequently detected organisms were unique to mid or high salinity zones, but four Nematoda (Meleidogyne spartinae, Prochaetosoma sp., Halalaimus sp., and Dichromadora sp.), two Annelida (Alitta succinea and Namalycastis jaya), two Platyhelminthes (Macrostomum kepneri and Mesorhynchus terminostylis), and one Kinorhyncha (Echinoderes sp.) were never detected in low salinity zones. None of the frequently detected taxa were unique for a particular distance from the marsh edge or bay. This dataset will be useful as baseline for assessing how soil communities will change in response to salinity changes caused by freshwater diversions and saltwater intrusion as well as measuring the environmental impact of pollution and other stressors.

Effects of salinity and light on growth and interspecific interactions between Myriophyllum spicatum L. and Ruppia maritima L.

Submerged macrophyte habitats provide significant benefits to estuarine systems. In southeast Louisiana, Myriophyllum spicatum L. (milfoil) and Ruppia maritima L. (widgeongrass) are dominant species existing across fresh to brackish areas. Though frequently co-occurring across the range of salinity and light conditions, their individual responses to changing environmental conditions from restoration, weather and climate may determine overall species distribution, and biomass abundance. We compared milfoil and widgeongrass growth (i.e., biomass increase) across a range of salinity and light, in monoculture (salinity: 0, 5, 10, 15, 20; light: high ˜ 50% ambient; low ˜ 20% ambient), and in mixture (salinity: 0, 10, 20; light: high, low). In monoculture, milfoil growth was reduced at high salinity (20) versus low salinity (0), while biomass allocation differed significantly with greater allocation to shoots under high light, compared to low light. Widgeongrass was minimally affected by salinity, with reduced stem densities at high salinity compared to low salinity. In mixture, both species under-yielded compared to monoculture with milfoil reduced with high salinity and light, and low salinity and light; widgeongrass under-yielded with low salinity and high light, and mid salinity (10) and low light. These differences in species’ responses suggest that salinity and light contribute to the distribution of milfoil and widgeongrass, with higher salinities and light favoring widgeongrass growth, and lower light possibly decreasing both species’ growth, and ultimately, distribution. With continued changes occurring and predicted from both coastal restoration and climate change, understanding drivers of habitat forming species remains critical to inform future landscapes.

Mixing and photoreactivity of dissolved organic matter in the Nelson/Hayes estuarine system (Hudson Bay, Canada)

This work presents the results of a 4-year study (2009–2012) investigating the mixing and photoreactivity of dissolved organic matter (DOM) in the Nelson/Hayes estuary (Hudson Bay). Dissolved organic carbon (DOC), colored DOM, and humic-like DOM decreased with increasing salinity (r2=0.70–0.84). Removal of DOM was noticeable at low to mid salinity range, likely due to degradation and/or adsorption to particles. DOM photobleaching rates (i.e., decrease in DOM signal resulting from exposure to solar radiation) ranged from 0.005 to 0.030h−1, corresponding to half-lives of 4.9–9.9days. Dissolved organic matter from the Nelson and Hayes Rivers was more photoreactive than from the estuary where the photodegradation of terrestrial DOM decreased with increasing salinity. Coincident with the loss of CDOM absorption was an increase in spectral slope S, suggesting a decrease in DOM molecular weight. Marked differences in photoreactivity of protein- and humic-like DOM were observed with highly humidified material being the most photosensitive. Information generated by our study will provide a valuable data set for better understanding the impacts of future hydroelectric development and climate change on DOM biogeochemical dynamics in the Nelson/Hayes estuary and coastal domain. This study will constitute a reference on terrestrial DOM fate prior to building additional generating capacity on the Nelson River.

Assessing the viability of microorganisms in the ballast water of vessels transiting the North Atlantic Ocean

Testing phytoplankton viability within ballast tanks and receiving waters of ballast water discharge remain understudied. Potentially harmful dinoflagellates and diatoms are transported via ballast water to Galveston Bay, Texas (USA), home to three major ports: Houston, Texas City and Galveston. Ballast water from vessels transiting the North Atlantic Ocean was inoculated into treatments representing low and high salinity conditions similar to the Ports of Houston and Galveston respectively. Phytoplankton in ballast water growout experiments were deemed viable and showed growth in low and mid salinities with nutrient enrichment. Molecular methods identified several genera: Dinophysis, Gymnodinium, Gyrodinium, Heterocapsa, Peridinium, Scrippsiella, Chaetoceros and Nitzschia. These phytoplankton genera were previously identified in Galveston Bay except Scrippsiella. Phytoplankton, including those capable of forming harmful algal blooms leading to fish and shellfish kills, are transported to Galveston Bay via ballast water, and are viable when introduced to similar salinity conditions found in Galveston Bay ports.

Statistical Analysis of the Hydrogeochemical Evolution of Groundwater in the Rangampeta area, Chittoor District, Andhra Pradesh, South India

Multivariate statistical techniques involving factor analysis (FA) and R-mode hierarchical cluster analysis (HCA) were performed on 30 groundwater samples from Rangampeta, Chittoor District, Andhra Pradesh, South India to extract principal processes controlling the water chemistry. The groundwater samples were analyzed for distribution of chemical elements Ca, Mg, Na, K, Si, HCO3, CO3, Cl, and SO4. It also includes pH, and electrical conductivity (EC). Gibbs diagrams were also constructed to identify the processes that are responsible in controlling the water chemistry. Factor analysis extracted for four factors consisting of F1 (with high loading factor of Cl, EC, Mg and Na), F2 (with high loading factor of K, (HCO3+CO3) and Ca), F3 (with high loading factor of pH and Si) and F4 (with high loading factor of SO4). The varifactors obtained from Factor analysis indicated that the parameters responsible for groundwater quality variations are mainly related to groundwater-rock interaction (particularly weathering of silicate minerals), agriculture and anthropogenic sources. With HC analysis the water samples have been classified into 4 clusters. Cluster I (13 wells) and cluster II (8 wells) have shown moderate salinity. However, cluster IV (4 wells) had the lowest concentrations of ions and classified as fresh water. Cluster III (5 wells) shows mid salinity between (I and II) and IV clusters. The distribution of these groundwater types and their quality has been found to be an in direct relation with the host rocks of the area. The results showed that the method was comprehensive and efficient in analyzing the dynamics of water quality.

Dissolved Mo and U in rivers and estuaries of India: Implication to geochemistry of redox sensitive elements and their marine budgets

Dissolved molybdenum (Mo) and uranium (U) concentrations were measured in five Indian estuaries; the Narmada, Tapi, Mandovi and the Mahi fall into the Arabian Sea and the Hooghly falling into the Bay of Bengal. Riverine Mo and U vary significantly, in the range of 1 to 90 and 0.02 to 19 nmol/kg respectively. The lowest Mo and U were observed in the Mandovi river, consistent with lateritic lithology exposed in its drainage, higher runoff and lower water-rock interaction. The Sabarmati has the highest U, 19 nmol/kg and sources from the groundwater having very high U concentration. The highest Mo (90 nmol/kg) is observed in the Mahi river and probably results from anthropogenic sources. Hooghly river seems to have high concentrations of Mo (14 nmol/kg) and U (8 nmol/kg) and are possibly derived from weathering of black shales of the Himalaya. Behaviour of Mo and U in all the estuaries analysed in this study is highly variable. Both Mo and U in the Narmada estuary during pre-monsoon and monsoon seasons and U in the Tapi estuary behave conservatively. Mo in the Tapi shows its addition in the mid salinity ranges (~ 4 to 12‰) and is sourced from anthropogenic activity probably related to effluent from industries situated along the estuary in this salinity range. Both dissolved Mo and U show their removal at lower salinity ranges in the Hooghly and the Mandovi estuaries. These estuaries are net sink of Mo in which significant amount of oceanic Mo along with riverine Mo is being lost. About 1.6 × 10 6 and 2 × 10 5 mol of Mo are being removed annually in the Hooghly and the Mandovi estuaries. Uranium removal is order of magnitude lower compared to Mo in both the Hooghly and the Mandovi estuaries. The loss of Mo and U in the estuaries are associated with mangrove swamps present in the estuaries which seems to be an important sink of the oceanic Mo and could represent its significant sink in oceanic budget of Mo. The Gulf of Cambay has high dissolved Mo concentration compared to that of global average seawater value which is attributed to its supply from anthropogenic sources. Industrial effluent waste waters along with polluted rivers supply ~ 5 × 10 6 mol of Mo annually to the Gulf of Cambay which could be derived from petrochemicals and pharmaceutical industries situated along the Gulf coast.

Variation in ultrafiltered and LMW organic matter fluorescence properties under simulated estuarine mixing transects: 1. Mixing alone

Ultrafiltered and low molecular weight dissolved organic matter (UDOM and LMW‐DOM, respectively) fluorescence was studied under simulated estuarine mixing using samples collected from Delaware, Chesapeake, and San Francisco Bays (USA) transects. UDOM was concentrated by tangential flow ultrafiltration (TFF) from the marine (>33 PSU), mid‐estuarine (∼16 PSU), and freshwater (<1 PSU) members. TFF permeates (<1 kDa) from the three members were used to create artificial salinity transects ranging from ∼0 to ∼36, with 4 PSU increments. UDOM from the end‐ or mid‐members was added in equal amounts to each salinity‐mix. Three‐dimensional fluorescence excitation‐emission matrix (EEMs) spectra were generated for each end‐member permeate and UDOM through the full estuarine mixing transect. Fluorescence components such as proteinaceous, terrigenous, and marine derived humic peaks, and certain fluorescent ratios were noticeably altered by simulated estuarine mixing, suggesting that LMW DOM and UDOM undergo physicochemical alteration as they move to or from the freshwater, mid‐estuarine, or coastal ocean members. LMW fluorescence components fit a decreasing linear mixing model from mid salinities to the ocean end‐member, but were more highly fluorescent than mixing alone would predict in lower salinities (<8). Significant shifts were also seen in UDOM peak emission wavelengths with blue‐shifting toward the ocean end‐member. Humic‐type components in UDOM generally showed lower fluorescent intensities at low salinities, higher at mid‐salinities, and lower again toward the ocean end‐member. T (believed to be proteinaceous) and N (labile organic matter) peaks behaved similarly to each other, but not to B peak fluorescence, which showed virtually no variation in permeate or UDOM mixes with salinity. PCA and PARAFAC models showed similar results suggesting trends could be modeled for DOM end‐ and mid‐member sources. Changes in fluorescence properties due to estuarine mixing may be important when using CDOM as a proxy for DOM cycling in coastal systems.

Cell size of Antarctic phytoplankton as a biogeochemical condition

AbstractTwo contrasting high nutrient/low chlorophyll regions having different conditions that control phytoplankton production, and separated by an area of blooming, are found during summer in the vicinity of the South Shetland Islands (Antarctica). Low chlorophyll conditions occur either in Fe-rich, deeply mixed and high salinity Weddell Sea shelf waters, or the Fe-poor, shoaled and low salinity Drake Passage Antarctic Circumpolar Current waters, while phytoplankton blooms are located between in mid salinity water. Contrasting phytoplankton communities were found to populate these different biogeochemical provinces. In data from six field seasons (1999–2007), nanoplankton (2–20 μm) were found to be dominant in the phytoplankton populations from light-controlled coastal waters, including blooms, with most chlorophyll found in the 2–5 μm size class. In contrast, the adjacent and presumably Fe-controlled Drake Passage waters were dominated by the microplankton (> 20 μm) size class. The asymmetrical distribution of phytoplankton size classes across the salinity gradient, when analysed independently of total chlorophyll concentration, supports the hypothesis that the different food web grazing dynamics are dependent upon biogeochemical provinces.

Survival and Growth of TriploidCrassostrea virginica(Gmelin, 1791) andC. ariakensis(Fujita, 1913) in Bottom Environments of Chesapeake Bay: Implications for an Introduction

Survival and growth of triploid Crassostrea virginica and triploid C. ariakensis were investigated at four sites surrounding Chesapeake Bay, United States, that varied in salinity, tidal regime, water depth, predation intensity and disease pressure. Four experimental treatments were established at each site: C. virginica; C. ariakensis; 50:50 of C. virginica: C. ariakensis; and shell only. Oysters were deployed at mean shell heights of 12.80 mm and 13.85 mm (C. virginica and C. ariakensis, respectively), at an overall density of 347.5 oysters m-2. Oyster survival and growth varied significantly with site and species. Survival was significantly higher in C. virginica than C. ariakensis at the intertidal site, and significantly higher in C. ariakensis than C. virginica at the highest salinity, subtidal site. Survival did not differ significantly between species at the mid and low salinity, subtidal sites. For both species, survival differed significantly between sites, with lowest survival in both species occurring at the intertidal site. Among the subtidal sites, C. virginica survival varied inversely with salinity, whereas C. ariakensis had the lowest survival at the mid salinity site. Eight months after deployment C. ariakensis were significantly larger than C. virginica at all sites. This difference generally persisted throughout the experiment, though the size differences between oyster species at the lowest salinity site were small (< 10%). Shell heights within single-species treatments differed significantly between sites; highest growth rates were observed at the high salinity, subtidal site, whereas lowest growth rates were observed at the high salinity, intertidal site. At low and mid salinity subtidal sites, C. ariakensis shell heights were significantly greater in the single-species treatment compared with the mixed-species treatment. Perkinsus marinus infections occurred in both species at all sites, with prevalences varying between sites. In C. virginica, moderate and high intensity infections were only common at the two higher salinity sites, whereas infections in C. ariakensis were generally low to rare. Haplosporidium nelsoni infections in C. virginica were only observed at the two higher salinity sites and prevalences were generally low. Two out of 53 C. ariakensis tested at the high salinity, subtidal site had rare H. nelsoni infections. Bonamia spp. infections were never observed. Our study supports previous laboratory findings and observations from its native range that C. ariakensis survives poorly in intertidal habitats. In subtidal habitats, however, C. ariakensis displayed broad environmental tolerances, often exceeding native oyster survival and growth rates. Post-introduction C. ariakensis populations would be shaped by the survival and growth patterns described here, but also by their reproductive success, larval survival, predator-prey interactions and prevailing disease dynamics.

Dietary flexibility in three representative waterbirds across salinity and depth gradients in salt ponds of San Francisco Bay

Salt evaporation ponds have existed in San Francisco Bay, California, for more than a century. In the past decade, most of the salt ponds have been retired from production and purchased for resource conservation with a focus on tidal marsh restoration. However, large numbers of waterbirds are found in salt ponds, especially during migration and wintering periods. The value of these hypersaline wetlands for waterbirds is not well understood, including how different avian foraging guilds use invertebrate prey resources at different salinities and depths. The aim of this study was to investigate the dietary flexibility of waterbirds by examining the population number and diet of three feeding guilds across a salinity and depth gradient in former salt ponds of the Napa-Sonoma Marshes. Although total invertebrate biomass and species richness were greater in low than high salinity salt ponds, waterbirds fed in ponds that ranged from low (20 g l−1) to very high salinities (250 g l−1). American avocets (surface sweeper) foraged in shallow areas at pond edges and consumed a wide range of prey types (8) including seeds at low salinity, but preferred brine flies at mid salinity (40–80 g l−1). Western sandpipers (prober) focused on exposed edges and shoal habitats and consumed only a few prey types (2–4) at both low and mid salinities. Suitable depths for foraging were greatest for ruddy ducks (diving benthivore) that consumed a wide variety of invertebrate taxa (5) at low salinity, but focused on fewer prey (3) at mid salinity. We found few brine shrimp, common in higher salinity waters, in the digestive tracts of any of these species. Dietary flexibility allows different guilds to use ponds across a range of salinities, but their foraging extent is limited by available water depths.

Molecular indicators of the sources and transformations of dissolved organic matter in the Mississippi river plume

The dynamics of dissolved organic matter (DOM) in the Mississippi river plume were investigated during four cruises to the region in 1990–1993. During each cruise, large-volume water samples were collected from a broad salinity gradient (0–36 psu) for the determination of dissolved organic carbon (DOC) concentrations and the isolation of DOM by tangential-flow ultrafiltration. The fraction of DOC recovered by ultrafiltration ranged from 49% in the river to 22% in the Gulf of Mexico. The ultrafiltered DOM (UDOM) was further characterized for the concentrations and compositions of combined neutral sugars and lignin-derived phenols. Concentrations of DOC ranged from 359 μM in the river during the summer to 65 μM in surface waters of the Gulf of Mexico during the winter. Mixing curves indicated minor losses of DOC at low salinities and a major source of DOC at mid salinities. Combined neutral sugars had elevated concentrations at mid salinities where plankton biomass and rates of autotrophic and heterotrophic processes were maximal, indicating that elevated concentrations of sugars and DOC were freshly-derived from plankton. In contrast, concentrations of lignin phenols in UDOM were depleted at low salinities, indicating losses due to flocculation of terrestrially-derived humic substances. The selective removal of syringyl phenols from dissolved lignin was observed in UDOM from higher salinity (>25 psu) waters, providing the first molecular evidence of the removal of terrigenous DOM from the coastal ocean due to photooxidation. Together, these molecular biomarkers indicated much greater dynamic behavior of DOM than was apparent from bulk DOC analyses, and they demonstrated that biological as well as physico-chemical processes were important in controlling the concentrations and compositions of DOM in coastal waters.

The estuarine geochemistry of rare earth elements and indium in the Chao Phraya River, Thailand

A new filtration method using a 0.04 μm hollow fiber filter was applied to the river, estuarine, and coastal waters in the Chao Phraya estuary for geochemical investigation. The filtered waters were analyzed for all the lanthanides, Y and In by using inductively coupled plasma mass spectrometry (ICPMS). The dissolved concentrations of rare earth elements (REEs) are significantly lower than those reported previously for other rivers, presumably because of effective removal of river colloids by the ultra-filtration. The variation of dissolved REEs in the estuary is dependent on the season. The light REEs vary considerably in the low salinity ( S < 3) zone presumably due to adsorption–desorption interaction with suspended particles. In January when the river discharge is low, the REEs show maxima in the mid salinity ( S = 5–12) zone suggesting that dissolved REEs are supplied to the waters by either desorption from suspended loads or remineralization of underlying sediments. The rapid removal of the REEs is also taking place in the turbid-clear water transition zone ( S = 12–15), presumably due to biological uptake associated with blooming of Noctilca occurred at the time of January sampling. In the medium to high discharge season (July and November), the dissolved REE(III)s at S > 3 show almost conservative trends being consistent with some of the previous works. Europium is strongly enriched in the river and estuarine waters compared to the South China Sea waters. Thus, the REE source of the Chao Phraya River must be fractionated and modified in entering to the South China Sea. Dissolved In and Ce in the high salinity ( S = 20–25) zone of the estuary are lower than those of the offshore waters, and therefore, the dissolved flux of the Chao Phraya River cannot account for the higher concentrations of dissolved In and Ce in the surface waters of the South China Sea. The negative Ce anomaly is progressively developed with increasing salinity, being consistent with continued oxidation of Ce(III) to Ce(IV) in the estuary. Fractionation of the light-to-heavy REEs seems to take place, whereas the Y/Ho fractionation is unclear in the estuarine mixing zone.

Primary Productivity Regime and Nutrient Removal in the Danube Estuary

The primary productivity regime, as well as the distribution of dissolved inorganic nutrients and particulate organic matter in the Danube estuary, were investigated during several cruises at different discharge regimes of the Danube River. The shallowness of the upper surface layer due to insignificant tidal mixing and strong stratification of the Danube estuary, as well as the high nutrient concentrations, are favourable for elevated primary production. The incident light levels at the bottom of the upper surface layer of the water column (0·5–3·0m) were generally higher than 20% of the surface irradiance. Elevated chlorophyll (Chl)aconcentrations with maxima at mid salinities were found during each survey. Within the upper mixed layer estimated primary production of 0·2–4·4g m−2day−1is very high compared with estuaries of other major world rivers. Mixing diagrams of dissolved inorganic nutrients reveal removal of significant quantities of nutrients during estuarine mixing. These observations were consistent with the distribution of particular organic matter, which was negatively correlated to the nutrient distribution during each survey. C:Chlaratios, as well as the elevated estimated production, indicate that biological transformation processes govern the nutrient distribution in this estuary.

Embryology and Influence of Temperature and Salinity on Early Development and Survival of Yellowtail Flounder Limanda lerruginea

The purposes of this research were to provide a detailed description of the embryonic development of the yellowtail flounder Limanda ferruginea and to determine the influences of temperature and salinity on developmental rates and survlval within the maximal environmental range of these variables (4-18 C; 28-38 % S ) . Embryological categories were described and related to developmental times at different temperatures. This relationship was direct and a series of power function curves were calculated for predictive purposes. Embryo survival to hatching was interactively affected by temperature and salinity. Response surface analyses showed low survival (10-30 %) a t low salinities coupled with low and high temperatures, and high survival (70-90 %) a t intermediate temperatures and higher salinities. The greatest mortality occurred during gastrulation. Time to 50 % hatching was inversely related to both temperature and salinity. Size at hatching (SL) was influenced by temperature and salinity interaction with larger larvae In the mid salinity range at mid to upper test temperatures. Occurrences of anomalies were relatively low ( < l 0 %). They were lower at intermediate test temperatures integrated over all salinities and higher a t intermediate test salinities integrated over all temperatures. Experimental results arc discussed with reference to environmental impact on yellowtail early life stayc survival.