Estuary Zone Research Articles

A simple optical model to estimate suspended particulate matter in Yellow River Estuary

Distribution of the suspended particulate matter (SPM) concentration is a key issue for analyzing the deposition and erosion variety of the estuary and evaluating the material fluxes from river to sea. Satellite remote sensing is a useful tool to investigate the spatial variation of SPM concentration in estuarial zones. However, algorithm developments and validations of the SPM concentrations in Yellow River Estuary (YRE) have been seldom performed before and therefore our knowledge on the quality of retrieval of SPM concentration is poor. In this study, we developed a new simple optical model to estimate SPM concentration in YRE by specifying the optimal wavelength ratios (600-710 nm)/ (530-590 nm) based on observations of 5 cruises during 2004 and 2011. The simple optical model was attentively calibrated and the optimal band ratios were selected for application to multiple sensors, 678/551 for the Moderate Resolution Imaging Spectroradiometer (MODIS), 705/560 for the Medium Resolution Imaging Spectrometer (MERIS) and 680/555 for the Geostationary Ocean Color Imager (GOCI). With the simple optical model, the relative percentage difference and the mean absolute error were 35.4% and 15.6 gm(-3) respectively for MODIS, 42.2% and 16.3 gm(-3) for MERIS, and 34.2% and 14.7 gm(-3) for GOCI, based on an independent validation data set. Our results showed a good precision of estimation for SPM concentration using the new simple optical model, contrasting with the poor estimations derived from existing empirical models. Providing an available atmospheric correction scheme for satellite imagery, our simple model could be used for quantitative monitoring of SPM concentrations in YRE.

PCO2 distribution and CO2 flux on the inner continental shelf of the East China Sea during summer 2011

Measurements of pH, total alkalinity (TA), partial pressure of CO2 (pCO(2)) and air-sea CO2 flux (FCO2) were conducted for the inner continental shelf of the East China Sea (ECS) during August 2011. Variations in pCO(2) distribution and FCO2 magnitude during the construction of the Three Gorges Dam (TGD) (2003-2009), and the potential effects of the TGD on the air-sea CO2 exchange were examined. Results showed that the ECS acts as an overall CO2 sink during summer, with pCO(2) ranging from 107 to 585 mu atm and an average FCO2 of -6.39 mmol/(m(2) center dot d). Low pCO(2) ( 420 mu atm) levels were found in the Changjiang estuary and Hangzhou Bay which acted as the main CO2 source. A negative relationship between pCO(2) and salinity (R (2)=0.722 0) in the estuary zone indicated the predominant effect of the Changjiang Diluted Water (CDW) on the seawater CO2 system, whereas a positive relationship (R (2)=0.744 8) in the offshore zone revealed the influence of the Taiwan Current Warm Water (TCWW). Together with the historical data, our results indicated that the CO2 sink has shown a shift southwest while FCO2 exhibited dramatic fluctuation during the construction of the TGD, which is located in the middle reaches of the Changjiang. These variations probably reflect fluctuation in the Changjiang runoff, nutrient import, phytoplankton productivity, and sediment input, which are likely to have been caused by the operations of the TGD. Nevertheless, the potential influence of the TGD on the CO2 flux in the ECS is worthy of further study.

Distribution Patterns of Calanoid Copepods along the Seomjin River Estuary in Southern Korea during Summer

The distribution patterns of estuarine copepods were investigated in the Seomjin River estuary of southern Korea after heavy rains in August 2006. Tidal influence extended 16 km from the estuary mouth. Each estuary zone (Oligohaline salinity＜5, mesohaline salinity 5~18, polyhaline salinity ＞18) changed within a range of about 5~6 km between low and high tides. A total of ten species were recorded, of which Pseudodiaptomus koreanus, Sinocalanus tenellus, and Tortanus dextrilobatus were predominant in the oligohaline zone; Acartia ohtsukai and Acartia forticrusa in the mesohaline zone; and A. erythraea, Calanus sinicus, Centropages dorsispinatus, Labidocera rotunda and Paracalanus parvus s. l. in the polyhaline zone. Their density was fastly reduced in the other zones. In particular, the oligohaline species migrated and aggregated into deeper water during ebb tides in order to retain their populations, while the same tendency was weaker for polyhaline species, suggesting that evolutionary traits primarily control population retention behaviors in estuarine environments.

Stability of Bacterial Composition and Activity in Different Salinity Waters in the Dynamic Patos Lagoon Estuary: Evidence from a Lagrangian-Like Approach

We employed a Lagrangian-like sampling design to evaluate bacterial community composition (BCC--using temporal temperature gel gradient electrophoresis), community-level physiological profiles (CLPP--using the EcoPlate™ assay), and influencing factors in different salinity waters in the highly dynamic Patos Lagoon estuary (southern Brazil) and adjacent coastal zone. Samples were collected monthly by following limnetic-oligohaline (0-1), mesohaline (14-16), and polyhaline (28-31) waters for 1 year. The BCC was specific for each salinity range, whereas the CLPPs were similar for mesohaline and polyhaline waters, and both were different from the limnetic-oligohaline samples. The limnetic-oligohaline waters displayed an oxidation capacity for almost all organic substrates tested, whereas the mesohaline and polyhaline waters presented lower numbers of oxidized substrates, suggesting that potential activities of bacteria increased from the polyhaline to oligohaline waters. However, the polyhaline samples showed a higher utilization of some simple carbohydrates, amino acids, and polymers, indicating a shortage of inorganic nutrients (especially nitrogen) and organic substrates in coastal saltwater. The hypothesis of bacterial nitrogen limitation was corroborated by the higher Nuse index (an EcoPlate™-based nitrogen limitation indicator) in the polyhaline waters and the importance of NO(2)(-), NO(3)(-), low-molecular-weight substances, and the low-molecular-weight:high-molecular-weight substances ratio, indicated by the canonical correspondence analyses (CCAs). Our results demonstrate the important stability of microbial community composition and potential metabolic activity in the different water salinity ranges, which are independent of the region and time of the year of sample collection in the estuary. This is a quite unexpected result for a dynamic environment such as the Patos Lagoon estuary.

Il “cuneo salino” nelle foci fluviali: sintesi delle problematiche

The “salt wedge” in river estuaries: overview of the issues.The salt wedge flowing landward and seaward in river final parts causes great impacts in estuarine areas both in surface water and groundwater, which are periodically contaminated by salt intrusion. A description of the main type of estuaries and their hydrodynamic classification is given, and salt wedge genesis and development are outlined. Salt wedge dynamics and impacts are discussed, and several examples are presented. The consequences of saltwater contamination affecting groundwater and surface waters used for irrigation in the estuary zones of the river Po and other water courses discharging into the North Adriatic Sea are put in evidence. Finally, structural and no-structural measures to counteract the salt wedge are discussed, and the methods adopted in several cases to minimize its impact are described.

On the potentiality of using the fluorescence of humic substances for the determination of hydrological structures in coastal sea waters and in inland water basins

This paper describes the potentialities of the characteristics of the fluorescence of humic substances (HS), namely, their intensity normalized to the Raman band intensity of water and the shape of their fluorescence band, as indications of the hydrological structures of the surface water layer in marine coastal areas (using the example of the North Sea region near the East Frisian Islands and the estuary zone of the Weser River) and in inland water basins (using the example of the Rybinsk Reservoir). We demonstrate that the HS fluorescence band’s shape parameters allow stricter discrimination of the dominant water masses as compared to the admixtures’ concentration-related indicators (the salinity, electric conductivity, and HS fluorescence intensity).

Concentration of selected heavy metals in water of the Juru River, Penang, Malaysia

This study was conducted to determine heavy metal lead (Pb), cadmium (Cd), Zinc (Zn) and copper (Cu) concentrations in water body of the Juru River, Penang, Malaysia. A total of 20 sampling stations were chosen and water at 1 m below the surface was sampled using Van Dorn water sampler in December 2009 and April 2010. Collected water samples were kept in ice and acidified to pH 2 using nitrite acid (analytical grade HNO 3 ). Heavy metal concentrations were determined using inductively couple plasma (ICP model Perkin elmer/elan 9000) following standard method procedures. For comparison purposes, the river was divided into three different zones in the first and second samplings that is, upstream zone, middle reach zone and estuary zone and each zone consists of 7, 7, 6 sampling sites, respectively. Generally, results indicate that Pb and Cd and Cu in the first sampling were higher than the second sampling while the concentrations of Zn in the second sampling were higher than the first sampling. Also the results indicate that the Cd and Pb and Zn in the estuary zone were the lowest as compared to other zones. Meanwhile the highest concentration of Cu was in the middle zone. In conclusion, the lowest concentrations of some heavy metals were in estuary zone, it seems to be naturally due to dilution to heavy metals from sea water. Average metal concentrations from 20 water samples indicate that studied metal concentrations were still lower than Malaysian’s National Water Quality Standards (INWQS) guideline. Keywords: Heavy metals, pollution, river, inductively couple plasma

Haemocytic leukemia in Prince Edward Island (PEI) soft shell clam (Mya arenaria): Spatial distribution in agriculturally impacted estuaries

Intensive farming of potatoes in Prince Edward Island (PEI) relies on the repeated and widespread application of fertilizers and pesticides. In PEI the main potato farming areas are in close proximity and drain directly to estuaries. Runoff from high agricultural activity watersheds could impact benthic organism health in the depositional zone of downstream estuaries. The estuarine filter feeder Mya arenaria (soft-shell clam) could be particularly vulnerable to both particle-adsorbed and water soluble contaminants. M. arenaria is susceptible to haemocytic leukemia. In May 2009, we established that heavily proliferated leukemia (HPL) prevalence was generally higher in PEI estuaries located downstream of high intensity potato farming (Dunk and Wilmot estuaries) watersheds than in estuaries downstream of lower intensity areas. Using Mab-1E10 based immunocytochemistry we observed that leukemic haemocytes from the Dunk and Wilmot estuaries were 1E10 negative whereas those from the Ox/Sheep estuary (low potato farming intensity) were 1E10 positive. The expression of genes in the p53 tumour suppressor pathway enabled us to differentiate groups of leukemic and normal M. arenaria, validating our diagnoses. In October 2009, we confirmed that HPL prevalence was elevated in the Dunk and Wilmot estuaries compared to reference (Souris River). Moreover, leukemia prevalence declined with distance from the river mouths along transects through the Dunk and Wilmot estuaries. The pesticides ß-endosulfan and α-endosulfan were detected in surface sediments from the Dunk and Wilmot estuaries, but not in sediments from either the Souris River or several other lower intensity potato farming watersheds. Our study provides evidence of an association between intensity of potato farming and prevalence of clam leukemia at downstream estuaries in PEI.

The physiological ecology of the supratidal amphipod Talorchestia longicornis

Physiology, behavior, habitat, and morphology are used to determine the degree of adaptation to life on land for amphipod species and systemization within the four functional groups of the family talitridae. Talorchestia longicornis is a semi-terrestrial amphipod found in the supratidal zone of estuaries. The present study investigates the physiological adaptations of this species to life on land through measurements of osmoregulation and respiration. Over the salinity range of 1–40‰, T. longicornis regulated its hemolymph hyperosmotically at low salinities and hypoosmotically at high salinities. The isosmotic point was about 27‰. Analogously, hemolymph chloride levels were well regulated being hyperionic at low salinities and hypoionic at high salinities. This species is capable of respiration in both air and water. Slopes ( b values) of the relationship between weight and oxygen uptake rates ranged from 0.316 to 0.590. Oxygen uptake rates were higher in air than water and at night versus day. Q 10 values were slightly below 2.0 for respiration in air for amphipods, irrespective of weight. These physiological adaptations, along with its behaviors, habitat, and morphology, place T. longicornis within the Group III sandhoppers of the Talitridae.

High Levels of Sediment Contamination Have Little Influence on Estuarine Beach Fish Communities

While contaminants are predicted to have measurable impacts on fish assemblages, studies have rarely assessed this potential in the context of natural variability in physico-chemical conditions within and between estuaries. We investigated links between the distribution of sediment contamination (metals and PAHs), physico-chemical variables (pH, salinity, temperature, turbidity) and beach fish assemblages in estuarine environments. Fish communities were sampled using a beach seine within the inner and outer zones of six estuaries that were either heavily modified or relatively unmodified by urbanization and industrial activity. All sampling was replicated over two years with two periods sampled each year. Shannon diversity, biomass and abundance were all significantly higher in the inner zone of estuaries while fish were larger on average in the outer zone. Strong differences in community composition were also detected between the inner and outer zones. Few differences were detected between fish assemblages in heavily modified versus relatively unmodified estuaries despite high concentrations of sediment contaminants in the inner zones of modified estuaries that exceeded recognized sediment quality guidelines. Trends in species distributions, community composition, abundance, Shannon diversity, and average fish weight were strongly correlated to physico-chemical variables and showed a weaker relationship to sediment metal contamination. Sediment PAH concentrations were not significantly related to the fish assemblage. These findings suggest that variation in some physico-chemical factors (salinity, temperature, pH) or variables that co-vary with these factors (e.g., wave activity or grain size) have a much greater influence on this fish assemblage than anthropogenic stressors such as contamination.

Spatio-temporal variability of phytoplankton assemblages in the Pearl River estuary, with special reference to the influence of turbidity and temperature

The Pearl River Estuary is among the largest estuaries in the subtropical areas of the world. Along the salinity and turbidity gradient between the freshwater reach of the Pearl River and the marine water of the South China Sea, the spatial and temporal composition and abundance of phytoplankton was examined in relation to physic-chemical variables during the dry and wet seasons of 2009. Water samples for phytoplankton and environmental parameters were collected from 18 stations during two seasons along a transect from upper estuary to estuarine and marine sectors. A total of 162 species belonging to 7 phyla were identified, with diatoms dominated in both seasons while dinoflagellates proliferated in autumn. Two main clusters and three sub-clades under each main cluster corresponding to seasons and water sectors were defined with multivariate analysis (cluster and nMDS). Based on the species composition and abundance of phytoplankton, both seasonal and spatial variability were observed at a significant level (ANOSIM: season effect, R=0.896, P<0.01; station effect, R=0.463, P<0.01). The correlation analysis between biotic and abiotic variables indicated that instead of the “proverbial” anthropogenic nutrients loading and salinity gradient, the best 2-variable combination (temperature and turbidity) showed a significant effect on the pattern of phytoplankton assemblages ( ρ w =0.49, BIOENV analysis) between wet and dry seasons in the Pearl River Estuary. This result suggests that physical disturbance either natural or manmade is a more important factor in regulating the phytoplankton community structure within the hydrologically distinct zone of estuaries.

Diel fish movements in the littoral zone of a temporarily closed South African estuary

The importance of shallow littoral habitat is a long standing paradigm of estuarine ecology, particularly in facilitating the nursery role they play for many fish. Diel cycles have been linked to the redistribution of fish between habitats and may also influence the movement of various sized fish within littoral zone of estuaries. Fine scale temporal (hourly) movements of four size classes of fish (< 100 mm, 100–300 mm, 301–500 mm and > 500 mm total length) onto a shallow (< 0.7 m) littoral zone within a South African estuary was examined using a duel frequency identification sonar (DIDSON) continuously over 24 h periods. Fish within the size classes of 100–300 mm and 301–500 mm were more abundant in the littoral zone during twilight and at night compared to day, whilst the largest size class (> 501 mm) showed no difference in abundance among these three diel periods. The strongest patterns were observed within the small fish (< 100 mm), which were abundant in the littoral zone during the day but never observed in this habitat after dark. Daily commuting onto and off the shallow littoral zone occurred within tight time periods (< 45 min), and were synchronous with sunrise and sunset respectively. It is hypothesized that these movements are linked to the presence/absence of zooplankton (feeding ecology) and predator avoidance. Large predatory fish up to 1010 mm were also observed on the littoral zone, and whilst rare, indicate very large fish will swim into shallow estuarine waters. Our results support the theory that littoral zone habitats harbour high abundances of small fish and may provide refuge from large piscivorous predators in deeper waters. However, observations of the diel movement behaviour of small fishes indicate that the use of littoral habitats is more complicated than often suggested.

Review of the Monograph by Yu.N. Gurskii Geochemistry of the Lithohydrosphere of Interior Seas Volume 1: Methods of the Investigation and the Processes of the Formation of the Chemical Composition of the Interstitial Waters in Deposits of the Black, Azov, Kaspian, White, and Baltic Seas (Moscow, GEOS, 2003.). Volume 2: Interstitial Waters of the Red and Mediterranean Seas and Estuary

Review of the Monograph by Yu.N. Gurskii Geochemistry of the Lithohydrosphere of Interior Seas Volume 1: Methods of the Investigation and the Processes of the Formation of the Chemical Composition of the Interstitial Waters in Deposits of the Black, Azov, Kaspian, White, and Baltic Seas (Moscow, GEOS, 2003.). Volume 2: Interstitial Waters of the Red and Mediterranean Seas and Estuary

Habitat shifts and spatial distribution of the intertidal crab Neohelice ( Chasmagnathus) granulata Dana

Intertidal zones of estuaries and embayments of the SW Atlantic are dominated by the semiterrestrial burrowing grapsid crab, Neohelice ( Chasmagnathus) granulata, and characterized by extensive mud flats surrounded by salt marshes. In this work we examined spatial patterns of distribution of N. granulata during two years to explain their movement patterns. The results of the population sampling showed segregation by sex and size throughout the intertidal, with seasonal variations in densities and different condition indices for adults and juveniles at the different zones. The comparison of seasonal activity (ambulatory activity outside burrows) between marshes and mudflats shows that short term (e.g. daily) variations in activity were controlled by tides. Crabs were active at high tides but increased their activity on days with higher tidal amplitude. Seasonal activity showed that at both areas, females remain with low activity except for a peak in winter, while males showed the highest activity during summer in the mudflat zone, but not so in the marsh. This pattern can be the response to differences in stress tolerance, suggesting that high temperatures are limiting the performance of adult crabs during summer, especially at the marsh where physical conditions can be more critical. The spatial size segregation can be explained by differential mortality in each zone (estimated with tethered crabs), and by the juvenile movement between these zones (estimated with movement traps). Juvenile mortality is higher at the mudflat, while adult mortality is higher in the marsh. Smaller juveniles moved to the marsh, where the mortality is lower, and the larger juveniles moved towards the mudflat. This mortality is due almost exclusively to cannibalism, so our results suggest that this movement of different size classes between zones is controlled, at least in part, by intraspecific predation.

Residency time, migration route and survival of Atlantic salmon Salmo salar smolts in a Canadian fjord

Atlantic salmon Salmo salar smolts (n = 181) from two rivers were surgically implanted with acoustic transmitters and released to determine migration route, residency time and survival in a 50 km long estuarine fjord located on the south coast of Newfoundland, Canada. Data obtained from automated receivers placed throughout the Bay d'Espoir fjord indicated that migrating smolts used different routes to reach the outer areas of the fjord. The duration of time that smolts spent in the immediate estuary zone also differed between the two localities (7 and 17 days) although the total time smolts were resident in the fjord was similar and extensive (40 days). Many smolts were resident for periods of 4-8 weeks moving back and forth in the outer part of the fjord where maximum water depths range from 300 to 700 m. Survival in the estuary zone was greater for smolts with prolonged residency in estuarine habitat. Overall smolt survival to the fjord exit was moderately high (54-85%), indicating that the initial phase of migration did not coincide with a period of unusually high mortality.

Geochemical features of processes on the ground floor of the marginal filter in the river-sea system

The interaction between ocean and continent is essentially controlled by the existence of a marginal filter in the global river-sea system, which determines the main features of the transformation of sedimentary material and individual chemical elements in the mix� ing zone of river water and seawater (1, 2). The results of longterm studies of researchers of the Laboratory of Physicogeological Investigations of the Institute of Oceanology, Russian Academy of Sciences, allowed us to reveal regularities in the evolution of this system and establish specific peculiarities of the transformation of suspended and dissolved forms of elements in the water column on the river-sea profile in the most dif� ferent areas of the World Ocean and in numerous estu� ary zones (3, 4). The main attention in these studies was given to the conditions of extraction and precipi� tation of sedimentary material to the floor from the river water in the course of its mixing with seawater, which determines successive change in the stages of the evolution of the whole system along the horizontal profile of the water column from the surface to the bottom of the estuary (1, 5). However, no less interesting and important are geochemical and hydrodynamic processes, which are developed under the bottom of the estuary, namely in the bottom deposits and the mutually related exchange system of sediment-interstitial water-bottom water, i.e., at the ground floor of the marginal filter. The point is that precipitation of particles of river suspension and colloids in the estuary zones requires months, days, and possibly even hours at relatively low depths. In the geological sense this is a momentary process. But nature provides much longer time (tens, hundreds, thousands, and tens of thousands years) for the devel� opment of early diagenesis in modern deposits.

Phylogeny, phenotypic and nutritional characteristics of estuarine soil actinomycetes having broad-spectrum antimicrobial activity derived from an ecologically guided bioprospecting programme

No investigation has been done to identify ecological factors selecting for broad-spectrum antimicrobial activity of actinomycetes in the estuaries. Previously, we established that, in the Sundarbans (the world’s largest tidal mangrove forest), high antagonistic potential (AP) sampling sites were influenced by tides, while the low AP sites were not. We now report molecular phylogenetic analysis, morphological, physiological and biochemical characteristics of actinomycetes of high AP sites. The effects of soil organic carbon, nitrogen and ionic content (which strongly influenced AP) on the strength and spectrum of activity of the isolates were also studied in shake flasks. Molecular phylogenetic analysis showed sequences of our strains to be 96–99% similar to the 16S rDNA sequences of Streptomyces. Results showed variation among sporophore sizes, ornamentation and number of spores. Jaccard’s similarity coefficients of the isolates varied from 0.512 to 0.884 indicating disparity in the biochemical and physiological characteristics, possibly due to spatial separation of the sampling sites. Top soil in the intertidal zone of estuaries is generated from settling and consolidation of fluid mud and Streptomyces would be expected to produce broad-spectrum antimicrobials in such virgin soil. Isolates should be collected from the narrow band between the mean high and low tide marks to maximize chances of finding broad-spectrum activity. Considering the study on nutritional requirements vis-a-vis the field studies, it was concluded that results of this investigation corroborated the field observations where soil nitrogen, rather than organic carbon or ionic concentration, played a major role in determining the antimicrobial spectrum.

Dissolved oxygen in contrasting estuaries of the Bay of Biscay: effects of temperature, river discharge and chlorophyll a

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 418:57-71 (2010) - DOI: https://doi.org/10.3354/meps08812 Dissolved oxygen in contrasting estuaries of the Bay of Biscay: effects of temperature, river discharge and chlorophyll a Arantza Iriarte1,*, Guillermo Aravena1, Fernando Villate1, Ibon Uriarte2, Berta Ibáñez3,7, Marcos Llope4,6, Nils Chr. Stenseth4,5 1Laboratory of Ecology, Department of Plant Biology and Ecology, Faculty of Science and Technology, University of the Basque Country, PO Box 644, 48080 Bilbao, Spain 2Laboratory of Ecology, Department of Plant Biology and Ecology, Faculty of Pharmacy, University of the Basque Country, Paseo de la Universidad 7, 01006 Gasteiz, Spain 3Basque Foundation for Health Innovation and Research (BIOEF), 48015 Sondika, Bizkaia, Spain 4Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway 5Flødevigen Marine Research Station, Institute of Marine Research, 4817 His, Norway 6Present address: Instituto Español de Oceanografía (IEO), Centro Oceanográfico de Cádiz, Puerto Pesquero, Muelle de Levante s/n, PO Box 2609, 11006 Cádiz, Andalucía, Spain 7Present address: Biomedical Research Center, 31008 Pamplona, Spain *Email: arantza.iriarte@ehu.es ABSTRACT: The effects of environmental factors on variations of dissolved oxygen (DO) saturation was assessed in 2 estuaries (Bilbao and Urdaibai) in the Bay of Biscay with contrasting hydrography and anthropogenic impact, for the period 1997 to 2006, using generalised additive models (GAMs) and generalised additive mixed models (GAMMs). Spatial and temporal variations in DO saturation and the current severity and extent of hypoxia were higher in the culturally eutrophicated and stratified Bilbao estuary. Seasonal patterns of DO saturation and the hierarchy of factors controlling them differed both between estuaries and between salinity zones. In the inner Bilbao estuary, the main factor explaining DO-saturation variations was temperature, with a dominant effect on oxygen consumption processes. In contrast, in the outer Bilbao estuary, the main factor explaining DO-saturation variations was chlorophyll a, suggesting that the effect of oxygen production through photosynthesis was stronger than that of oxygen consumption. In the inner Urdaibai estuary, both a negative relationship with temperature and a positive relationship with chlorophyll a were detected. The outer Urdaibai estuary showed strong water-column mixing and very high tidal flushing, and ventilation processes were more important than oxygen production or consumption processes. River discharge affected DO saturation only at the inner waters, but when the effects of several variables on DO-saturation variability were tested in an additive model, river discharge was excluded from the models. The effects of temperature-dependent processes on DO-saturation dynamics decreased from the inner to the outer zones of both estuaries. KEY WORDS: Dissolved oxygen · Chlorophyll · Temperature · River discharge · Estuary · Generalised additive models · Bay of Biscay Full text in pdf format PreviousNextCite this article as: Iriarte A, Aravena G, Villate F, Uriarte I, Ibáñez B, Llope M, Stenseth NC (2010) Dissolved oxygen in contrasting estuaries of the Bay of Biscay: effects of temperature, river discharge and chlorophyll a. Mar Ecol Prog Ser 418:57-71. https://doi.org/10.3354/meps08812 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 418. Online publication date: November 18, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Suspended particulate matter in the St. Lawrence estuary and Gulf surface layer and development of a remote sensing algorithm

Remote sensing of chlorophyll concentration is potentially affected by the presence of inorganic matter in the water column. Seasonal variability of total suspended particulate matter (SPM) concentration and its partition into organic and inorganic fractions was thus measured in the estuary and Gulf of St. Lawrence during five cruises. These measures were made in the surface layer down to the depth of the 0.1% light level. Results indicate that vertical variability was small for the entire study area. Data analysis lead to the definition of two main regions having different SPM characteristics: 1) the estuary zone characterized by a strong spatial variability, intermediate SPM concentrations and a clear spring phytoplankton bloom that is combined to an increased inorganic matter load; 2) the gulf region characterized by a relatively low SPM concentration and phytoplankton blooms in the spring and fall periods. Combined with in situ measurements of remote sensing reflectances, the database was used to validate existing inorganic matter retrieval algorithms and develop a new one better adapted to the low concentrations encountered in the St. Lawrence estuary and Gulf.

Morphological description of the gastropod Heleobia australis (Hydrobiidae) from egg to hatching

Raquel A. F. Neves ¹*, Jean Louis Valentin and Gisela M. Figueiredo ¹Universidade Federal do Rio de Janeiro Programa de Pos-Graduacao em Ecologia (PPGE-UFRJ) Laboratorio de Zooplâncton Marinho Av. Professor Rodolpho Rocco 211, Cidade Universitaria, Rio de Janeiro, RJ, Brasil. CEP: 24949-900 *Corresponding author: raquelneves@ufrj.br Hydrobiidae family (Caenogastropoda) has a global distribution in the intertidal zones of lagoons and estuaries (KABAT; HERSHLER, 1993). They constitute a diverse group of gastropods consisting of more than 1000 species (BOSS, 1971) and they play an important role in the benthic food web (KABAT; HERSHLER, 1993). In South America, Heleobia australis (Orbigny, 1835) is the dominant species of the Hydrobiidae family and it is an important food source for many species (ALBERTONI et al., 2003). Heleobia australis occurs in estuarine systems and coastal lagoons from Rio de Janeiro, Brazil to the Rio Negro, Argentina (SILVA; VEITENHEIMER-MENDES, 2005), and it forms dense populations that reach up to 40,000 ind./m² (BEMVENUTI et al., 1978). It is a gonochoristic species with internal fertilization and the sperm may be stored for some time before fertilization, as described for other Gastropoda (KOHN et al., 1987). As protostomes, H. australis has spiral and determinate cleavage. Their eggs have an animal-vegetal polarity that defines the anterior-posterior axis of the embryo (COLLIER, 1997; NIELSEN, 2004). Related species deposits their egg masses from which pelagic veligers develop (SOLA, 1996), and H. australis has been observed to present a similar development (pers. observation). In order to better understand ecological, behavioral and taxonomic aspects of organisms it is important to know their morphological characteristics throughout their life cycle. However, studies of Hydrobiidae life cycles are still rare, particularly as regards their development from eggs to veliger larvae. For H. australis, despite its abundance, no stage of development has yet been described. This is thus the first study to describe the development of this species from egg to hatching by continuous observation. The characterization of this stage may help in the identification of the species. KOHN et al. (1987) suggested using pigmentation and velar lobe shape to identify living specimens. Heleobia australis was sampled in two areas of Guanabara Bay (Rio de Janeiro, Brazil) (22°84’S 043°20’W; 22°76’S 043°20’W) using a Van-veen grab (0.05 m²) in May and September, 2009. The sediment in the regions sampled was muddy (silt-clay), without any vegetation, and had a low dissolved oxygen concentration (VALENTIN et al., 1999). Egg masses were separated from thirty adults and kept in covered 150-ml Petri dishes with filtered (0.07 µm) sea water at 23°C, the same temperature as that recorded in the natural habitat. Then the eggs were isolated and classified according to their stage and maintained under the same conditions. A few eggs in each stage were observed daily and photographed using a Canon camera attached to a Zeiss Axiostar optic microscope. The images were then analyzed and the embryos measured using the Carl Zeiss imaging solutions program Axio Vision (V 4.5). The egg masses were observed attached to the adult shells (Fig. 1A), which is typical of the Hydrobiidae. Breeding seems to occur year-round in Guanabara Bay. As with other species of Hydrobiidae, mature females lay their fertilized eggs in capsules (or egg masses), preferably on live shells of their own species (FISH; FISH, 1974), but they may also be laid on dead shells, shells of other species, on sand grains, or algae (ANDERSON, 1971). The egg masses of H. autralis were yellow and consisted of capsules, each one containing one white egg that developed into a veliger larva. The number of eggs per egg mass varied between 10 and 15 (n=30). Some eggs had not completed their development and different development stages were to be found in the same egg mass; embryos in the initial stage of development and post-hatching capsules were observed in the same egg mass. Despite not being possible to determine the timing of development of each stage, the stages were classified in accordance with the development proposed by Russo and Patti (2005). A. Pre-division phase: egg before the cleavage. The capsules are of spherical shape and compact. The egg diameter was of about 80 µm and the capsule about 120 µm (Fig. 1B; n = 15).