Changes In Water Salinity Research Articles

A tidal creek water budget: Estimation of groundwater discharge and overland flow using hydrologic modeling in the Southern Everglades

Taylor Slough is one of the natural freshwater contributors to Florida Bay through a network of microtidal creeks crossing the Everglades Mangrove Ecotone Region (EMER). The EMER ecological function is critical since it mediates freshwater and nutrient inputs and controls the water quality in Eastern Florida Bay. Furthermore, this region is vulnerable to changing hydrodynamics and nutrient loadings as a result of upstream freshwater management practices proposed by the Comprehensive Everglades Restoration Program (CERP), currently the largest wetland restoration project in the USA. Despite the hydrological importance of Taylor Slough in the water budget of Florida Bay, there are no fine scale (∼1 km 2) hydrodynamic models of this system that can be utilized as a tool to evaluate potential changes in water flow, salinity, and water quality. Taylor River is one of the major creeks draining Taylor Slough freshwater into Florida Bay. We performed a water budget analysis for the Taylor River area, based on long-term hydrologic data (1999–2007) and supplemented by hydrodynamic modeling using a MIKE FLOOD (DHI, http://dhigroup.com/) model to evaluate groundwater and overland water discharges. The seasonal hydrologic characteristics are very distinctive (average Taylor River wet vs. dry season outflow was 6 to 1 during 1999–2006) with a pronounced interannual variability of flow. The water budget shows a net dominance of through flow in the tidal mixing zone, while local precipitation and evapotranspiration play only a secondary role, at least in the wet season. During the dry season, the tidal flood reaches the upstream boundary of the study area during approximately 80 days per year on average. The groundwater field measurements indicate a mostly upwards-oriented leakage, which possibly equals the evapotranspiration term. The model results suggest a high importance of groundwater contribution to the water salinity in the EMER. The model performance is satisfactory during the dry season where surface flow in the area is confined to the Taylor River channel. The model also provided guidance on the importance of capturing the overland flow component, which enters the area as sheet flow during the rainy season. Overall, the modeling approach is suitable to reach better understanding of the water budget in the mangrove region. However, more detailed field data is needed to ascertain model predictions by further calibrating overland flow parameters.

Modelling soil water and salt dynamics under pulsed and continuous surface drip irrigation of almond and implications of system design

The HYDRUS-2D model was experimentally verified for water and salinity distribution during the profile establishment stage (33 days) of almond under pulsed and continuous drip irrigation. The model simulated values of water content obtained at different lateral distances (0, 20, 40, 60, 100 cm) from a dripper at 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140 and 160 cm soil depths at different times (5, 12, 19, 26 and 33 days of profile establishment) were compared with neutron probe measured values under both irrigation scenarios. The model closely predicted water content distribution at all distances, times and soil depths as RMSE values ranged between 0.017 and 0.049. The measured mean soil water salinity (ECsw) at 25 cm from the dripper at 30, 60, 90 and 150 cm soil depth also matched well with the predicted values. A correlation of 0.97 in pulsed and 0.98 in continuous drip systems with measured values indicated the model closely predicted total salts in the root zone. Thus, HYDRUS-2D successfully simulated the change in soil water content and soil water salinity in both the wetting pattern and in the flow domain. The initial mean ECsw below the dripper in pulsed (5.25 dSm−1) and continuous (6.07 dSm−1) irrigations decreased to 1.31 and 1.36 dSm−1, respectively, showing a respective 75.1 and 77.6% decrease in the initial salinity. The power function [y = ax−b] best described the mathematical relationship between salt removal from the soil profile as a function of irrigation time under both irrigation scenarios. Contrary to other studies, higher leaching fraction (6.4–43.1%) was recorded in pulsed than continuous (1.1–35.1%) irrigation with the same amount of applied water which was brought about by the variation in initial soil water content and time of irrigation application. It was pertinent to note that a small (0.012) increase in mean antecedent water content (θi) brought about 8.25–9.06% increase in the leaching fraction during the profile establishment irrespective of the emitter geometry, discharge rate, and irrigation scenario. Under similar θi, water applied at a higher discharge rate (3.876 Lh−1) has resulted in slightly higher leaching fraction than at a low discharge rate (1.91 Lh−1) under pulsing only owing to the variation in time of irrigation application. The influence of pulsing on soil water content, salinity distribution, and drainage flux vanished completely when irrigation was applied daily on the basis of crop evapotranspiration (ETc) with a suitable leaching fraction. Therefore, antecedent soil water content and scheduling or duration of water application play a significant role in the design of drip irrigation systems for light textured soils. These factors are the major driving force to move water and solutes within the soil profile and may influence the off-site impacts such as drainage flux and pollution of the groundwater.

Benthic foraminifera and their stable isotope composition in sediment cores from Lake Qarun, Egypt: changes in water salinity during the past ~500 years

We studied the sedimentology, benthic foraminifera, molluscs, and δ18O and δ13C of Ammonia tepida tests in two late Holocene sediment cores from Lake Qarun (Egypt). The cores, QARU2 (upper section, 8.2 m) and QARU4 (1.4 m), span approximately the past 500 years of sedimentation. Benthic foraminifera first appeared in the upper part of QARU2 at 314 cm depth, ca. AD 1550. This depth marks the beginning of colonization of the lake by foraminifera and indicates a change in lake water salinity, as foraminifera cannot tolerate fresh water. Initially, three species of benthic foraminifera colonized the lake, Ammonia tepida, Cribroelphidium excavatum and Cribrononion incertum. Relative abundance of these species fluctuated throughout cores QARU2 and QARU4 and highest overall faunal diversity occurred at the beginning of the twentieth century. High relative abundances of C. incertum and deformed tests are attributed to periods of greater lakewater salinity. Peaks in both δ18O and δ13C indicate times of higher evaporation and reduced fresh water inflow. Inferred salinity was high around AD 1700 and after AD 1990. Rapid response of climate proxy variables indicates the high sensitivity of Lake Qarun to environmental changes over the past several 100 years. Increases in lakewater Mg concentration during past evaporative events, associated with less fresh water inflow, probably provided conditions suitable for C. incertum to build its white or transparent tests. Gradual decrease of C. incertum, until its disappearance at 100 cm depth ca. AD 1890, indicates a more persistent trend in lake water chemistry. Higher concentrations of dissolved sulphates were the likely cause of this species disappearance. Recent, twentieth-century sediments were deposited under optimal salinity (37‰) for benthic fauna, but further environmental changes are indicated by the decrease or disappearance of several benthic foraminifera and mollusc species. Intermittent hypoxia in the lake’s bottom waters, caused by cultural eutrophication, may account for these most recent changes.

Grazing as a driver for Populus euphratica woodland degradation in the semi-arid Aibi Hu region, northwestern China

The endangered river plain woodlands of semi-arid Central Asia provide numerous ecosystem services. Previous studies have focused mainly on changes in water supply and salinity as the underlying mechanisms of Populus euphratica woodland’s decline. We tested whether vegetative regeneration of P. euphratica serves as an alternative pathway to propagation from seeds for reproduction in a degraded tree steppe in northwestern China and whether this method also works on grazed sites. We measured the effects of different grazing pressures on tree growth, survival, and vegetative regeneration. When subjected to high or moderate grazing pressure, P. euphratica populations failed to regenerate vegetatively, indicating recruitment limitation. A 25% increase of grazing pressure decreased the ramet density to 50% and the ramet height to 25%, as well as reducing the average age of ramets to one year. As overgrazing seriously limits the potential of natural recovery of P. euphratica a balance between livestock grazing and the regeneration of the Tugai forests is needed to sustain positive effects of increasing water tables and floods on tree vitality and regeneration. To restore population structure, and to support early vegetative regeneration long-term livestock management interventions to exclude livestock from degraded and recovered land need to be developed.

Relationship of Salt Marsh Vegetation Zonation to Spatial Patterns in Soil Moisture, Salinity, and Topography

An intertidal San Francisco Bay salt marsh was used to study the spatial relationships between vegetation patterns and hydrologic and edaphic variables. Multiple abiotic variables were represented by six metrics: elevation, distance to major tidal channels and to the nearest channel of any size, edaphic conditions during dry and wet circumstances, and the magnitude of tidally induced changes in soil saturation and salinity. A new approach, quantitative differential electromagnetic induction (Q-DEMI), was developed to obtain the last metric. The approach converts the difference in soil electrical conductivity (ECa) between dry and wet conditions to quantitative maps of tidally induced changes in root zone soil water content and salinity. The result is a spatially exhaustive map of edaphic changes throughout the mapped area of the ecosystem. Spatially distributed data on the six metrics were used to explore two hypotheses: (1) multiple abiotic variables relevant to vegetation zonation each exhibit different, uncorrelated, spatial patterns throughout an intertidal salt marsh; (2) vegetation zones and habitats of individual plant species are uniquely characterized by different combinations of key metrics. The first hypothesis was supported by observed, uncorrelated spatial variability in the metrics. The second hypothesis was supported by binary logistic regression models that identified key vegetation zone and species habitat characteristics from among the six metrics. Based on results from 108 models, the Q-DEMI map of saturation and salinity change was the most useful metric of those tested for distinguishing different vegetation zones and plant species habitats in the salt marsh.

Large Multidecadal Salinity Trends near the Pacific–Antarctic Continental Margin

Abstract Ocean temperature and salinity measurements on and near the Antarctic continental shelf in the southwest Pacific sector are evaluated for evidence of temporal change. Shelf water in the southwest Ross Sea has declined in salinity by 0.03 decade−1 from 1958 to 2008, while its temperatures have increased in proportion to the influence of salinity on the sea surface freezing point. Modified deep-water intrusions that reach the central Ross Ice Shelf have freshened at a similar rate and cooled by ∼0.5°C since the late 1970s. Salinity has decreased by 0.08 decade−1 in the westward coastal and slope front currents, consistent with increased melting of continental ice upstream in the Amundsen Sea. Overturning of those near-surface waters during winter sea ice formation and mixing across the slope front is sufficient to account for the 5-decade shelf water salinity change. A strong correlation between the freshening and change in the southern annular mode index suggests a link with the large-scale atmospheric circulation. Salinity has decreased by ∼0.01 decade−1 in bottom and lower deep waters north of the continental slope between 140E° and 180°. Accompanying abyssal temperature changes are minor and variability is high, but density has declined along with salinity. Continued increases in water column stratification will modify the mode and formation rate as well as the properties of bottom and deep waters produced in this region.

Salinity changes in the North West Pacific Ocean during the late Pliocene/early Quaternary from 2.73 Ma to 2.52 Ma

Recent research has increasingly advocated a role for the North Pacific Ocean in modulating global climatic changes over both the last glacial cycle and further back into the geological record. Here a diatom δ 18O record is presented from Ocean Drilling Program Site 882 over the Pliocene/Quaternary boundary from 2.73 Ma to 2.52 Ma (MIS G6–MIS 99). Large changes in δ 18O diatom of c. 4‰ from 2.73 Ma onwards are documented to occur on a timeframe broadly coinciding with glacial–interglacial cycles. These changes are primarily attributed to large scale inputs of meltwater from glacials surrounding the North Pacific Basin and the Bering Sea. Despite these inputs and associated change in surface water salinity, on the basis of existing opal and U k 37 temperature data and new modelled water column densities, no evidence exists to suggests a removal of the halocline stratification or a resumption of the high productivity system similar to that which prevailed prior to 2.73 Ma. The permanence of the halocline suggests that the region played a key role in driving global climatic changes over the early glacial–interglacial cycles that followed the onset of major Northern Hemisphere Glaciation by inhibiting deep water upwelling and ventilation of CO 2 to the atmosphere.

Salinity and flow regime independent multiphase flow measurements

For oil production fields, there is a need for downhole measurements of the gas/water/oil multiphase flow. In extreme conditions a relatively simple, robust, and non-intrusive system will be appropriate. A measurement setup that combines multiple gamma beam (MGB) and dual modality densitometry (DMD) measurements, would be able to determine the gas volume fraction (GVF) independently of the flow pattern, and monitor changes in water salinity. MGB measurements of gamma-ray transmission along multiple sections across the oil pipe will provide information on the flow pattern. Whereas the DMD principle will give information on changes in salinity from a combination of transmission and scattering gamma-radiation measurements. In this work we present the results from MGB and DMD measurements of a multiphase flow with high-speed gamma-ray tomograph measurements as reference for the flow pattern. The MGB measurements should enable us to distinguish between stratified or wavy/slug and annular or slug flow. Flow patterns with several minor components distributed evenly over the measurement cross section, like bubble flow, will be interpreted as homogeneous flow. The DMD measurements can be used to monitor salinity changes of the water component for intervals where the GVF is low and the water cut of the liquid is high. Combined with other gauges for water cut measurements, the MGB and DMD measurement setup should improve the multiphase flow measurements, and enable increased oil/gas recovery and production water monitoring.

Compensating for temperature variations in time-lapse electrical resistivity difference imaging

Variations in temperature during time-lapse electrical resistivity imaging (ERI) surveys introduce changes in electrical conductivity (EC). When the goal of the time-lapse ERI survey is to image changes in EC due to changes in saturation or pore water salinity, compensation must be made for the effect of temperature variations. A temperature-compensation method can approximate time-lapse ERI data with the effect of temperature variations removed. First uncompensated ERI data are inverted. The inversion model then is adjusted to a standard temperature image. Forward simulations are performed using the uncompensated inversion and the standard temperature equivalent model. The temperature-compensated simulated resistance data are subtracted from the uncompensated simulated resistance data, forming data correction terms. The data correction terms then are subtracted from the measured data to yield temperature-compensated data. Using the temperature-compensated data, inversions have been carried out on two synthetic data sets and a field example. Differencing two temperature-compensated data inversions is found to be superior to differencing two postinversion standard temperature equivalent images. Temperature compensation on the data allows temperature corrections to be applied to time-lapse difference inversion schemes and hydrogeophysical inversion where postinversion temperature-correction methods are not easily applied.

The paleoclimate of the Eastern Mediterranean during the transition from early to mid Pleistocene (900 to 700 ka) based on marine and non-marine records: An integrated overview

Climate change is frequently considered an important driver of hominin evolution and dispersal patterns. The role of climate change in the last phase (900–700 ka) of the Middle Pleistocene Transition (MPT) in the Levant and northeast Africa was examined, using marine and non-marine records. During the MPT the global climate system shifted from a linear 41 k.yr. into a highly non-linear 100 k.yr. system, considerably changing its global modulation. Northeast Africa aridity further intensified around 950 ka, as indicated by a sharp increase in dust flux, and a jump to overall higher levels thereafter, coinciding with a lack of sapropels in the deep eastern Mediterranean (930–690 ka). The increased dust flux centering at ∼800 ka corresponds to the minima in 400 k.yr. eccentricity, a minima in 65 °N solar forcing and in the weakest African monsoon precession periodicity. This resulted in expansion of hyper-arid conditions across North Africa, the lowest lake levels in eastern Africa and the lowest rainfall in the Nile River headwaters. In the eastern Mediterranean an increasing continental signature is seen in glacial stages 22 (∼880 ka) and 20 (∼800 ka). Lower arboreal pollen values also indicate arid conditions during these glacial stages. The southern and eastern parts of the Negev Desert, unlike its northern part, were hyper-arid during the MPT, making them highly unsustainable. The fluctuations in the stands of Lake Amora follow global climate variability but were more moderate than those of its last glacial Lake Lisan successor. In the northern Jordan-Valley Hula Lake, frequent fluctuations in lake level coincide with both global climate changes and minor changes in water salinity varying from fresh to oligohaline. It appears therefore that the most pronounced and widespread deterioration in climate occurred in northeast Africa from 900 to 700 ka, whereas in the Levant the corresponding climatic changes were more moderate.

Factors Influencing the Distribution of Poeciliopsis fasciata along the Rio Salado (Puebla, Mexico)

ABSTRACT In Mexico, several species of fishes are being affected by anthropogenic changes in rivers and streams. In order to understand the potential impacts of human activities on Poeciliopsis fasciata, we examined characteristics of the Rio Salado in Puebla, Mexico that were associated with the presence of P. fasciata. Fish were observed in the river in March 2007 and from November 2007 through February 2008, but not from April 2007 through October 2007. The dynamic nature of the Río Salado likely influences the presence of P. fasciata, as evidenced by our finding fish in the study area only during a limited period during the year. The distribution of P. fasciata along the Rio Salado is clearly influenced by factors related to the permanence of water, the chemical nature of the water (salinity, dissolved oxygen), and the presence of vegetation. Our results suggest that the presence of salt factories (“salineras”) along the Río Salado have the potential to influence the presence of P. fasciata, either through changes in water flow or salinity.

Interannual and long-term hydrographic changes in the Yellow Sea during 1977–1998

Abstract Interannual and long-term changes in water temperature and salinity (T-S) in the Yellow Sea were examined using seasonal observations made during 1977–1998. The winter and summer seasons are distinctly different in their stratification conditions. In winter the water column is well mixed and the dominant feature of the T-S distribution is the warm and saline Yellow Sea Warm Water occupying the deep region. The winter water temperature has interannual variations, a long-term warming trend, and distinct cold and warm phases before and after 1986. Changes in the winter water temperature are driven by the lateral heat input associated with the intrusion by the Yellow Sea Warm Current. Changes in winter sea-surface salinity correspond to changes in the rate of surface evaporation. In summer the water column is strongly stratified. Interannual changes in surface temperature are caused by changes in surface heat flux, while surface salinity changes correlate well with the changes in precipitation. The summer surface temperature (salinity) tends to be low (high) in El Nino years and increases (decreases) in the year after El Nino. In summer, changes in the bottom temperature and salinity are not coherent over the whole region. In the deep region, the summer bottom T-S represent a property of the Yellow Sea Cold Water, and their interannual changes correspond to T-S changes in the Yellow Sea Warm Water in winter.

Hydrological structure of the Sheksna River Deep of the Rybinsk Reservoir and water quality assessment by biological parameters

Peculiarities of formation and seasonal dynamics of hydrological structure of the Sheksna River Deep of the Rybinsk Reservoir are considered. The contribution of various genetic water types, including run-offs of the town of Cherepovets, to the formation of its water masses is established on the grounds of model calculations. It is shown, that the hydrological structure effects the distribution of hydrobionts in sewage disposal areas. The assessment of the contribution of Cherepovets run-offs to the change of total water salinity of the deep is given.

Cretaceous Phytoplankton Assemblages from Songke Core‐1, North and South (SK‐1, N and S) of Songliao Basin, Northeast China

Abstract:Cretaceous phytoplankton from the newly completed core hole (SK‐1, N&S) in the central Songliao Basin was studied. The target interval is from the upper Quantou Formation of Upper Cretaceous to Mingshui Formation. Twelve genera of dinoflagellates, six of acritarcha and three of chlorophyta were identified in 588 samples from the 2300‐m deep core. Ten phytoplankton assemblages have been classified: Tetranguladinium‐Subtilisphaera‐Botryococcus, Botryococcus‐Pediastrum, Pediastrum, Dinogymniopsis‐Chlamydophrella‐Vesperopsis bifurcate, Dinogymniopsis minor‐Balmula, Pediastrum‐Botryococcus, Schizosporis‐Campenia, Kiokansium‐Dinogymniopsis‐Botryococcus, Dinogymniopsis‐Granodiscus‐Filisphaeridium and Granodiscus. According to the findings mentioned above, the age of the upper Qantou Formation is Cenomanian, the Qingshankou Formation belongs to upper Cenomanian‐Turonian, the Yaojia Formation to Coniancian‐Santonian age, the Nenjiang Formation is of Campanian age, and Sifangtai‐Mingshui formations are referred to Maastrichtian stage. The ecology of phytoplankton is closely related to water salinity. Each type of phytoplankton is within a certain living water mass whose evolution type reflects salinity change of the Songliao Lake. The assemblages from the SK‐1 indicate that water salinity changes with the cycle of freshwater–slight brackish water–brackish water–slight brackish water–freshwater in the lake.

Activity of antioxidant enzymes and physiological responses in ark shell, Scapharca broughtonii, exposed to thermal and osmotic stress: Effects on hemolymph and biochemical parameters

Changes in water temperature and salinity are responsible for a variety of physiological stress responses in aquatic organisms. Stress induced by these factors was recently associated with enhanced reactive oxygen species (ROS) generation, which caused oxidative damage. In the present study, we investigated the time-related effects of changes in water temperature and salinity on mRNA expression and the activities of antioxidant enzymes (SOD and CAT) and lipid peroxidation (LPO) in the gills and digestive glands of the ark shell, Scapharca broughtonii. To investigate physiological responses, hydrogen peroxide (H(2)O(2)), lysozyme activity, aspartate aminotransferase (AspAT), and alanine aminotransferase (AlaAT) were measured in the hemolymph. Water temperature and salinity changes significantly increased antioxidant enzyme mRNA expression and activity in the digestive glands and gills in a time-dependent manner. H(2)O(2) concentrations increased significantly in the high-temperature and hyposalinity treatments. LPO, AspAT and AlaAT levels also increased significantly in a time-dependent manner, while lysozyme activity decreased. These results suggest that antioxidant enzymes play important roles in reducing oxidative stress in ark shells exposed to changes in water temperature and salinity.

Effects of extreme changes of sea water temperature and salinity on the development of the sand dollar Scaphechinus mirabilis

The combined effects of temperatures of 14, 17, 20, 22, and 25°C and salinities of 36–12‰ on embryos and larvae of the sand dollar Scaphechinus mirabilis was studied. Embryonic development is the most sensitive stage in the early ontogenesis of S. mirabilis. It is completed at a temperature of 14–20°C in a salinity range of 36–24‰ and at temperature of 22°C to 26‰. The fertilization proceeds in wider ranges of temperature and salinity. Among the swimming larvae, blastulae showed the greatest resistance to variations of these environmental factors. All the larvae survived at a temperature of 14–22°C and a salinity of 36–20‰, and more than 70% of them at 18‰. The pluteus I is the most vulnerable stage; probably this is related to the formation of the larval skeleton and transition to phytoplankton feeding. The survival of larvae at the age of 20 days was 100% at 14–22° C and a salinity of 36–24‰, most of them survived at 14–20°C and a salinity 18‰. The temperature 25 ° C is the most damaging for early development of S. mirabilis. The duration of development of that species lasts 28.5–29 days at 20°C and a salinity of 32.2–32.6‰. At 20 and 22°C, the larvae settled and completed metamorphosis more quickly if sand from the parental habitat was present. The larvae did not settle during the experiment (14 days) at 14 ° C and in the absence of sand.

Regional and seasonal variability of zooplankton collected using sediment traps in the southeastern Beaufort Sea, Canadian Arctic

Time-series sediment traps were deployed at six mooring sites in the southeastern Beaufort Sea from October 2003 to August 2004 during the cruise of the Canadian research vessel Amundsen within the framework of the Canadian Arctic Shelf Exchange Study (CASES). Trap-collected zooplankton (TCZ) at around 200 m water depth was dominated by copepods accounting for 74–93% of the total abundance throughout the year with increase in abundance at all sites during the fall. Seven distinct TCZ groups were identified through cluster analysis. Two marked seasonal shifts in TCZ composition from late fall to early winter and from spring to early summer were revealed at five sites at 200 m depth. The zooplankton was dominated by Oncaea spp., pteropods, and copepod nauplii in the late fall cluster and in the winter cluster, and by copepod nauplii in the summer cluster. A significant change in water temperature, salinity, and sea ice concentration was observed only with the spring–summer shift. The cluster analysis also revealed that TCZ composition at 200 m at a station located in the Cape Bathurst Polynya was markedly different from those at other sites through the study period by being characterized by the dominance of various copepodite stages of Metridia longa. This was probably due to a less prolonged period of sea ice cover, which provides favorable food conditions for the zooplankton community.

Threatened Biodiversity of Sundarban Biosphere Reserve with Reference to Faunal Habitat and Need for Its Preservation

The beautiful forests of Sunder bans embracing mysterious tracts of wilderness are located in the lower Ganga delta of Bengal. The mangrove forests and the overall ecosystem in Sunder bans are the ideal habitats for large group of terrestrial, avian and aquatic fauna, starting from Protozoa to Mammals. It contains the richest biodiversity among the inter-tidal forest in the worlds and is the only natural mangrove forest in the world, where the tiger (Panthera tigris tigris L.) resides. The reason for high faunal diversity is the fact that here the ocean and land comes in contact of each other. The succession from ocean to land and to fresh water/ brackish-water through estuaries, change in water salinity from almost nil to high through grades of different concentration; newly formed islands with soft swampy mud to mature old islands with hard saline banks provides fascinating habitat opportunities to various organism. During the last two centuries, these highly productive mangrove ecosystems had been suffering from rapid degradation. If this negligence or ignorance continues in future there will be random exploitation of this natural resource and loss of diverse biota will be unavoidable. A genuine understanding of the interaction of responsible factors should be of paramount interest to the estuarine ecosystem and for prosperity. Recently, it has been established that natural factors along with direct and indirect human interferences have largely changed the biological composition, ecosystem function, productivity, and regeneration and succession patterns within the mangrove ecosystem.

Episodic meteorological and nutrient-load events as drivers of coastal planktonic ecosystem dynamics: a time-series analysis

In temperate coastal zones, episodic meteorological forcing can have a strong impact on the classical seasonal phytoplankton succession. Episodes of continental runoff and wind storms involve nutrient enrichment and turbulence, 2 factors that can promote primary production and alter the planktonic community species composition and size structure. We determined the joint influence of these 2 variables on the osmotrophic plankton of an oligotrophic NW Mediterranean open bay. We used an 8 yr long time series of monthly physical, chemical and biological water-column parameters, and we looked for correlations between these and several meteorological and physical high- frequency time series through cross-correlation analyses. Influence of river runoff in this particular location was found to be very important for phytoplankton dynamics, whereas no immediate response of bacterioplankton was detected. Resuspension events caused by waves had a secondary importance. Cross correlations allowed defining a sequence of responses to these types of forcing, from changes in water turbidity and salinity, to increases in phytoplankton and bacteria abundances through nutrient enrichments. The maximum response of the ecosystem in terms of chlorophyll a concentration lagged nutrient enrichment events by about 1 wk. A more detailed analysis was per- formed between June 2003 and June 2004, a period characterised by an intense drought in summer and by 6 strong meteorological events afterwards. The increase in the frequency of meteorological events during this period drove the system from heterotrophy to autotrophy. Our data stress the importance of episodic meteorological events in coastal planktonic communities.

Phytoplankton bloom status: Chlorophyll a biomass as an indicator of water quality condition in the southern estuaries of Florida, USA

Altered freshwater inflows have affected circulation, salinity, and water quality patterns of Florida Bay, in turn altering the structure and function of this estuary. Changes in water quality and salinity and associated loss of dense turtle grass and other submerged aquatic vegetation (SAV) in Florida Bay have created a condition in the bay where sediments and nutrients have been regularly disturbed, frequently causing large and dense phytoplankton blooms. These algal and cyanobacterial blooms in turn often cause further loss of more recently established SAV, exacerbating the conditions causing the blooms. Chlorophyll a (CHLA) was selected as an indicator of water quality because it is an indicator of phytoplankton biomass, with concentrations reflecting the integrated effect of many of the water quality factors that may be altered by restoration activities. Overall, we assessed the CHLA indicator as being (1) relevant and reflecting the state of the Florida Bay ecosystem, (2) sensitive to ecosystemdrivers (stressors,especially nutrient loading), (3)feasible to monitor, and (4) scientifically defensible. Distinct zones within the bay were defined according to statistical and consensual information. Threshold levelsof CHLA for each zonewere defined using historical data and scientific consensus. A presentation template of condition of the bay using these thresholds is shown as an example of an outreach product.