Leaf Gas Exchange and Nutrient Use Efficiency Help Explain the Distribution of Two Neotropical Mangroves under Contrasting Flooding and Salinity

Rhizophora mangle and Laguncularia racemosa cooccur along many intertidal floodplains in the Neotropics. Their patterns of dominance shift along various gradients, coincident with salinity, soil fertility, and tidal flooding. We used leaf gas exchange metrics to investigate the strategies of these two species in mixed culture to simulate competition under different salinity concentrations and hydroperiods. Semidiurnal tidal and permanent flooding hydroperiods at two constant salinity regimes (10 g L−1 and 40 g L−1) were simulated over 10 months. Assimilation ( ), stomatal conductance ( ), intercellular CO2 concentration ( ), instantaneous photosynthetic water use efficiency (PWUE), and photosynthetic nitrogen use efficiency (PNUE) were determined at the leaf level for both species over two time periods. Rhizophora mangle had significantly higher PWUE than did L. racemosa seedlings at low salinities; however, L. racemosa had higher PNUE and and, accordingly, had greater intercellular CO2 (calculated) during measurements. Both species maintained similar capacities for A at 10 and 40 g L−1 salinity and during both permanent and tidal hydroperiod treatments. Hydroperiod alone had no detectable effect on leaf gas exchange. However, PWUE increased and PNUE decreased for both species at 40 g L−1 salinity compared to 10 g L−1. At 40 g L−1 salinity, PNUE was higher for L. racemosa than R. mangle with tidal flooding. These treatments indicated that salinity influences gas exchange efficiency, might affect how gases are apportioned intercellularly, and accentuates different strategies for distributing leaf nitrogen to photosynthesis for these two species while growing competitively.

Distribution of Diatoms Along Environmental Gradients in the Charlotte Harbor, Florida (USA), Estuary and Its Watershed: Implications for Bioassessment of Salinity and Nutrient Concentrations

The relative abundance of diatom species in different habitats can be used as a tool to infer prior environmental conditions and evaluate management decisions that influence habitat quality. Diatom distribution patterns were examined to characterize relationships between assemblage composition and environmental gradients in a subtropical estuarine watershed. We identified environmental correlates of diatom distribution patterns across the Charlotte Harbor, Florida, watershed; evaluated differences among three major river drainages; and determined how accurately local environmental conditions can be predicted using inference models based on diatom assemblages. Sampling locations ranged from freshwater to marine (0.1–37.2 ppt salinity) and spanned broad nutrient concentration gradients. Salinity was the predominant driver of difference among diatom assemblages across the watershed, but other environmental variables had stronger correlations with assemblages within the subregions of the three rivers and harbor. Eighteen indicator taxa were significantly affiliated with subregions. Relationships between diatom taxon distributions and salinity, distance from the harbor, total phosphorus (TP), and total nitrogen (TN) were evaluated to determine the utility of diatom assemblages to predict environmental values using a weighted averaging-regression approach. Diatom-based inferences of these variables were strong (salinity R 2 = 0.96; distance R 2 = 0.93; TN R 2 = 0.83; TP R 2 = 0.83). Diatom assemblages provide reliable estimates of environmental parameters on different spatial scales across the watershed. Because many coastal diatom taxa are ubiquitous, the diatom training sets provided here should enable diatom-based environmental reconstructions in subtropical estuaries that are being rapidly altered by land and water use changes and sea level rise.

Loadings of dissolved organic matter and nutrients from the Neva River into the Gulf of Finland – Biogeochemical composition and spatial distribution within the salinity gradient

We studied the loadings of dissolved organic matter (DOM) and nutrients from the Neva River into the Eastern Gulf of Finland, as well as their distribution within the salinity gradient. Concentrations of dissolved organic carbon (DOC) ranged from 390 to 840 μM, and were related to absorption of colored DOM (CDOM) at 350 nm, aCDOM(350), ranging from 2.70 to 17.8 m-1. With increasing salinity both DOC and aCDOM decreased, whereas the slope of aCDOM spectra, SCDOM(300-700), ranging from 14.3 to 21.2 μm-1, increased with salinity.

Loadings of dissolved organic matter and nutrients from the Neva River into the Gulf of Finland – Biogeochemical composition and spatial distribution within the salinity gradient

We studied the loadings of dissolved organic matter (DOM) and nutrients from the Neva River into the Eastern Gulf of Finland, as well as their distribution within the salinity gradient. Concentrations of dissolved organic carbon (DOC) ranged from 390 to 840 μM, and were related to absorption of colored DOM (CDOM) at 350 nm, aCDOM(350), ranging from 2.70 to 17.8 m-1. With increasing salinity both DOC and aCDOM decreased, whereas the slope of aCDOM spectra, SCDOM(300-700), ranging from 14.3 to 21.2 μm-1, increased with salinity.

On the stability and spatiotemporal variance distribution of salinity in the upper ocean

Despite recent advances in ocean observing arrays and satellite sensors, there remains great uncertainty in the large-scale spatial variations of upper ocean salinity on the interannual to decadal timescales. Consonant with both broad-scale surface warming and the amplification of the global hydrological cycle, observed global multidecadal salinity changes typically have focussed on the linear response to anthropogenic forcing but not on salinity variations due to changes in the static stability and or variability due to the intrinsic ocean or internal climate processes. Here, we examine the static stability and spatiotemporal variability of upper ocean salinity across a hierarchy of models and reanalyses. In particular, we partition the variance into time bands via application of singular spectral analysis, considering sea surface salinity (SSS), the Brunt Väisälä frequency (N2), and the ocean salinity stratification in terms of the stabilizing effect due to the haline part of N2 over the upper 500m. We identify regions of significant coherent SSS variability, either intrinsic to the ocean or in response to the interannually varying atmosphere. Based on consistency across models (CMIP5 and forced experiments) and reanalyses, we identify the stabilizing role of salinity in the tropics—typically associated with heavy precipitation and barrier layer formation, and the role of salinity in destabilizing upper ocean stratification in the subtropical regions where large-scale density compensation typically occurs.

Impacts of climatic factors on evolution of molecular diversity and the natural distribution of wild stocks of the giant freshwater prawn (Macrobrachium rosenbergii)

Natural distributions of most freshwater taxa are restricted geographically, a pattern that reflects dispersal limitation. Macrobrachium rosenbergii is unusual because it occurs naturally in rivers from near Pakistan in the west, across India and Bangladesh to the Malay Peninsula, and across the Sunda Shelf and Indonesian archipelago to western Java. Individuals cannot tolerate full marine conditions, so dispersal between river drainage basins must occur at limited geographical scales when ecological or climatic factors are favorable. We examined molecular diversity in wild populations of M. rosenbergii across its complete natural range to document patterns of diversity and to relate them to factors that have driven evolution of diversity in this species. We found 3 clades in the mitochondrial deoxyribonucleic acid (mtDNA) data set that corresponded geographically with eastern, central, and western sets of haplotypes that last shared a common ancestor 1 × 106 y ago. The eastern clade was closest to the common ancestor of all 3 clades and to the common ancestor with its congener, Macrobrachium spinipes, distributed east of Huxley's Line. Macrobrachium rosenbergii could have evolved in the western Indonesian archipelago and spread westward during the early to mid-Pleistocene to India and Sri Lanka. Additional groups identified in the nuclear DNA data set in the central and western clades probably indicate secondary contact via dispersal between regions and modern introductions that have mixed nuclear and mtDNA genes. Pleistocene sea-level fluctuations can explain dispersal across the Indonesian archipelago and parts of mainland southeastern Asia via changing river drainage connections in shallow seas on wide continental shelves. At the western end of the modern distribution where continental shelves are smaller, intermittent freshwater plumes from large rivers probably permitted larval dispersal across inshore areas of lowered salinity.

Development of salinity tolerance in rice by constitutive-overexpression of genes involved in the regulation of programmed cell death

Environmental factors contribute to over 70% of crop yield losses worldwide. Of these drought and salinity are the most significant causes of crop yield reduction. Rice is an important staple crop that feeds more than half of the world’s population. However among the agronomically important cereals rice is the most sensitive to salinity. In the present study we show that exogenous expression of anti-apoptotic genes from diverse origins, AtBAG4 (Arabidopsis), Hsp70 (Citrus tristeza virus) and p35 (Baculovirus), significantly improves salinity tolerance in rice at the whole plant level. Physiological, biochemical and agronomical analyses of transgenic rice expressing each of the anti-apoptotic genes subjected to salinity treatment demonstrated traits associated with tolerant varieties including, improved photosynthesis, membrane integrity, ion and ROS maintenance systems, growth rate, and yield components. Moreover, FTIR analysis showed that the chemical composition of salinity-treated transgenic plants is reminiscent of non-treated, unstressed controls. In contrast, wild type and vector control plants displayed hallmark features of stress, including pectin degradation upon subjection to salinity treatment. Interestingly, despite their diverse origins, transgenic plants expressing the anti-apoptotic genes assessed in this study displayed similar physiological and biochemical characteristics during salinity treatment thus providing further evidence that cell death pathways are conserved across broad evolutionary kingdoms. Our results reveal that anti-apoptotic genes facilitate maintenance of metabolic activity at the whole plant level to create favorable conditions for cellular survival. It is these conditions that are crucial and conducive to the plants ability to tolerate/adapt to extreme environments.

Fish distribution dynamics in the Aghanashini estuary of Uttara Kannada, west coast of India

Fish diversity (77 species) in the Aghanashini River estuary of the Indian west coast is linked to variable salinity conditions and zones I, II and III for high, medium and low salinity respectively. Zone I, the junction between Arabian Sea and the estuary, had all species in yearly succession due to freshwater conditions in monsoon to high salinity in pre-monsoon. The medium (zone II) and low (zone III) salinity mid and upstream portions had maximum of 67 and 39 fish species respectively. Maintenance of natural salinity regimes in estuary, among other ecological factors, is critical for its fish diversity.

Mercury in Florida Bay fish: spatial distribution of elevated concentrations and possible linkages to Everglades restoration

Health advisories are now posted in northern Florida Bay, adjacent to the Everglades, warning of high mercury concentrations in some species of gamefish. Highest concentrations of mercury in both forage fish and gamefish have been measured in the northeastern corner of Florida Bay, adjacent to the dominant freshwater inflows from the Everglades. Thirty percent of spotted seatrout (Cynoscion nebulosus Cuvier, 1830) analyzed exceeded Florida’s no consumption level of 1.5 μg g−1 mercury in this area. We hypothesized that freshwater draining the Everglades served as the major source of methylmercury entering the food web supporting gamefish. A lack of correlation between mercury concentrations and salinity did not support this hypothesis, although enhanced bioavailability of methylmercury is possible as freshwater is diluted with estuarine water. Stable isotopes of carbon, nitrogen, and sulfur were measured in fish to elucidate the shared pathways of methylmercury and nutrient elements through the food web. These data support a benthic source of both methylmercury and nutrient elements to gamefish within the eastern bay, as opposed to a dominant watershed source. Ecological characteristics of the eastern bay, including active redox cycling in near-surface sediments without excessive sulfide production are hypothesized to promote methylmercury formation and bioaccumulation in the benthos. Methylmercury may then accumulate in gamefish through a food web supported by benthic microalgae, detritus, pink shrimp (Farfantepenaeus duorarum Burkenroad, 1939), and other epibenthic feeders. Uncertainty remains as to the relative importance of watershed imports of methylmercury from the Everglades and in situ production in the bay, an uncertainty that needs resolution if the effects of Everglades restoration on mercury levels in fish are to be modeled and managed.

Some features of the autecology and distribution of chaetognatha in the Eastern Tropical Pacific

ENGLISH: The Inter-American Tropical Tuna Commission, in cooperation with the Tuna Oceanography Research program of the Scripps Institution of Oceanography, is studying in the Eastern Tropical Pacific Ocean methods of identifying waters of different characteristics that may influence the distribution and behavior of the tropical tunas. One method of attacking the problem has been to attempt to use zooplankton species as biological indicators of water masses. It has been demonstrated that certain zooplankters have ecological affinities that make them useful for identifying and tracing the movements of water masses. In the Eastern Pacific Ocean, Bieri (1957), Lea (1955), Le Brasseur (1959), Sund (1959), and Sund and Renner (1959) have presented evidence that certain species of Chaetognatha possibly can serve as indicators. The present work reports on a study of the distributions of species of Chaetognatha, obtained from various depths by means of horizontal closing-net hauls, in relation to concurrent measurements of temperature, salinity, and dissolved oxygen. Analyses of these data have provided a basis for determining which species are of potential use as biological indicators within the area of the Eastern Pacific considered in this study. SPANISH: La Comisión Interamericana del Atún Tropical, en cooperación con el programa de la "Tuna Oceanography Research" de la Institución Scripps de Oceanografía, viene estudiando en el Océano Pacífico Oriental Tropical métodos para identificar aguas de características diferentes que podrían influir en la distribución y en el comportamiento de los atunes tropicales. Uno de los métodos para abordar el problema ha sido el de intentar la utilización de especies zooplanctónicas como índices biológicos de masas de agua. Se ha demostrado que ciertos organismos del zooplancton tienen afinidades ecológicas, merced a las cuales son útiles para identificar y trazar los movimientos de las masas de agua. Bieri (1957), Lea (1955), Le Brasseur (1959), Sund (1959) y Sund y Renner (1959) presentaron evidencia de que ciertas especies de quetognatos pueden servir, posiblemente, como tales índices en el Océano Pacífico Oriental. El presente trabajo informa sobre un estudio de la distribución de las especies de quetognatos obtenidos de distintas profundidades por medio de la red de plancton que se cierra en lanzamientos horizontales y en relación con mediciones concomitantes de la temperatura, la salinidad y el oxígeno disuelto. El análisis de estos datos ofreció una base para la determinación de las especies que son potencialmente aptas para ser usadas como índices biológicos dentro del área del Pacífico Oriental a la cual se refiere este estudio.

Distribution and Abundance of Juvenile Salmonids off Oregon and Washington, 1981-1985

This report is a summary of the results of 883 purse seine sets made for juvenile salmonids during 15 cruises off the coasts of Oregon and Washington during the springs and summers of 1981-1985. Juvenile coho salmon (Oncorhynchus kisutch) occurred most frequently, followed by chinook salmon (0. tshawytscha). The juveniles of these two species co-occurred more frequently than expected. Juvenile chum, pink and sockeye salmon (0. keta, O. gorbuscha, and O. nerka), steelhead (0. mykiss) and cutthroat trout (0. clarki clarki) were caught much less frequently and in lower numbers than coho or chinook salmon. We found no evidence of large schools ofjuvenile salmonids. A northerly movement of juvenile coho salmon wa~ suggested by decreased catches off Oregon and increased catches off Washington between early and late summer. Highest catch per set of juvenile coho salmon was usually found inshore of 37.2 km. Juvenile chinook salmon were usually found within 27.9 km of the coast. Juvenile salmonids were found over a broad range of surface salinities and temperatures. High catches of juvenile coho salmon occurred in both the low salinity waters of the Columbia River plume and in adjacent higher salinity waters. Preferences for specific salinities or temperatures were not obvious for any species, although catch rates of juvenile coho salmon were highest in years when chlorophyll content was also high. Based on expansions of fish with coded wire tags, we estimated that hatchery coho salmon smolts comprised 74%, on average, of the juvenile coho salmon catches. The remaining 26% were presumably wild fish or hatchery fish released as fingerlings. Hatchery coho salmon were caught roughly in proportion to the numbers released. However, hatchery fish from the Columbia River and private coastal facilities were caught at slightly higher rates while those from coastal Washington and public coastal Oregon hatcheries were caught at slightly lower rates than expected from the numbers released. No juvenile coho salmon with coded wire tags were caught that had originated from either California or Puget Sound hatcheries. (PDF file contains 88 pages.)

Early-life-history profiles, seasonal abundance, and distribution of four species of Carangid larvae off Louisiana, 1982 and 1983

We present data on ichthyoplankton distribution, abundance, and seasonality and supporting environmental information for four species of coastal pelagics from the family Carangidae: blue runner Caranx crysos, Atlantic bumper Chloroscombrus chrysurus, round scad Decapterus punctatus, and rough scad Trachurus lathami. Data are from 1982 and 1983 cruises off Louisiana sponsored by the Southeastern Area Monitoring and Assessment Program (SEAMAP). Bioprofiles on reproductive biology, early life history, meristics, adult distribution, and fisheries characteristics are also presented for these species. Maximum abundances of larval blue runner, Atlantic bumper, and round scad were found in July inside the 4O-m isobath, although during the rest of the cruises these species were rarely found together. Larval Atlantic bumper were captured in June and July only; blue runner in May, June, and July; and round scad in all seasons. Atlantic bumper larvae, concentrated mostly off western Louisiana, were by far the most abundant carangid in 1982 and 1983. Larval blue runner were the second most abundant summer-spawned carangid in 1982 and 1983, but their abundance and depth distribution varied considerably between years. Relative abundance of larval round scad off Louisiana was low, and they were captured only west of the Mississippi River delta, although they are reported to dominate carangid populations in the eastern Gulf of Mexico. Rough scad were primarily winter/spring and outer-shelf (40-182 m) spawners. They ranked third in overall abundance, but were the most abundant target carangid on the outer shelf. Ecological parameters such as surface salinity, temperature, and station depth are presented from capture sites for recently hatched larvae <2.5 mm notochord length, except round scad) as well as for all sizes of fish below 14 mm standard length. (PDF file contains 44 pages.)

The distribution, abundance, and ecology of larval tunas from the entrance to the Gulf of California

ENGLISH: This study is based on collections of larvae of Thunnus albacares, Euthynnus llneatus, and Auxis sp. obtained from surface and oblique net tows made during seven cruises, each along a comparable track in the entrance of the Gulf of California and each during a different month. Concomitant measurements of surface temperature, salinity, and zooplankton were made at each of the plankton stations. The catches of larval Auxis sp. were examined by analysis of variance techniques to determine which environmental features were associated with the spawning of this tuna as indicated by the distribution of larvae and to gain some insight into the behavior of the larvae themselves. The testing indicated that the spawning of Auxis sp. varied significantly among the different months of the cruises. The testing also indicated that if the larvae were capable of avoiding the sampling apparatus, this ability was not related to features associated with time of day such as light conditions. The analysis did not detect any change in the vertical distribution of the larvae among the months of the experiment. It was concluded that the larvae did not exhibit a diel vertical movement. The measurements of temperature, salinity, and zooplankton volumes were treated as covariates in the analysis. The surface temperature proved to be a highly important factor in explaining the distribution of larvae, but salinity and zooplankton volumes were not. Catches of Thunnus albaeares and Euthynnus lineatus were rare during the course of the study; these are discussed in qualitative terms with respect to the time of the year and the surface temperature. The distribution of larval tunas in the area of study was compared with the distribution of surface water masses. It appeared that these masses had no influence per se on the distribution of larvae. SPANISH: Este estudio está basado en las recolecciones de larvas de Thunnus albacares, Eutbynnus lineatus, y Auxis sp. obtenidas según los arrastres superficiales y oblicuos de la red, realizados durante siete cruceros, cada uno a la entrada del Golfo de California a lo largo de un derrotero comparable, y cada uno durante distintos meses. Las mediciones correspondientes de la temperatura superficial, salinidad y de zooplancton se realizaron en cada una de las estaciones de plancton. Las capturas de larvas Auxís sp. fueron examinadas mediante el análisis de la varianza para determinar cuales características ambientales se encontraban asociadas con el desove de este atún según lo indicaba la distribución de las larvas, y para obtener alguna idea del comportamiento de las larvas en sí mismas. Las pruebas indicaron que el desove de Auxis sp. varió significativamente entre los diferentes meses de los cruceros; indicaron también que si las larvas eran capaces de evitar el aparato de muestreo, esta habilidad no se relacionaba a las características asociadas con la hora del día de acuerdo a las condiciones de luz. El análisis no demostró ningún cambio en la distribución vertical de las larvas durante los meses del experimento. Se determinó que las larvas no exhiben un movimiento vertical diario. Las mediciones de temperatura, salinidad, y de los volúmenes de zooplancton fueron tratadas como covariables en el análisis. La temperatura superficial demostró ser un factor altamente importante en la explicación de la distribución de las larvas, pero la salinidad y los volúmenes de zooplancton no lo fueron. Las capturas de Thunnus albacares y Eutbynnus lineatus fueron pocas durante el curso de este estudio; éstas se discuten en términos cualitativos respecto a la época del año y a la temperatura superficial. La distribución de los atunes larvales en el área de estudio fue comparada con la distribución de las masas superficiales de agua. Parece que estas masas no tienen influencia per se en la distribución de las larvas. (PDF contains 40 pages.)

Synopses of research on shrimps: 1. The common shrimp species of Sierra Leone's coastal waters: their distribution, abundance and size composition

The authors present quantitative information on the shrimp resources of Sierra Leone waters. Four of the nine species present have been studied, of which Paenaeus duorarum notialis is dominant in the fishery. Synoptic surveys were undertaken in June 1977, and March 1978, to determine the abundance of the shrimp stock on the inshore shelf. The temperature-salinity-depth curves for the fishing ground show the existence of three water masses. The majority of fish caught were sciaenids, with some sparids also being taken. Detailed discussion of distribution and abundance of individual species of shrimp is given. The surveys have shown that the Banana Islands are the most productive shrimp grounds in the country, and the authors believe that they can support a viable shrimp industry for several years to come at present rates of exploitation

Influence of temperature and salinity fluctuations on propagation behaviour of partially coherent beams in oceanic turbulence

A theoretical study of the behaviour of partially coherent beams propagating through oceanic turbulence has been performed. Based on the previously developed knowledge of beam spreading of a partially coherent beam in the atmosphere and the spatial power spectrum of the refractive index of ocean water, we study the normalized root-mean-square width of a partially coherent beam on propagation through oceanic turbulence and its turbulence distance which may be a measure of turbulence resistance. Our analysis indicates that the behaviour of partially coherent beams on propagation may be described by the rate of dissipation of the mean-squared temperature chi(T) and that of salinity chi(S). In terms of a quantity w that defines the contributions of the temperature and salinity distributions to the distribution of the refractive index, chi(S) could be written as a function of chi(T) and w. Therefore, the behaviour of partially coherent beams on propagation can be characterized only by chi(T) for a given w. The results are shown for curved surfaces, from which one can see that partially coherent beams exhibit robust turbulence resistance when the water volume has a smaller chi(T).