Open Coastal Waters Research Articles

Flood discharges of a small river into open coastal waters: Plume traits and material fate

The dynamics of plumes from large rivers are relatively well known. Many estuaries are small, however, and discharge directly onto exposed, open shorelines and presumably produce smaller plumes that may have different properties. Therefore this study measured traits of a small estuary on the Australian East Coast as a model system, focusing on (a) plume size, (b) distinctness of plume edges, and (c) imprints on the seafloor. Although plumes were found to be limited in spatial extent (ca. 1 km offshore × 2.4 km longshore) and were constrained near the shore by onshore winds, they exported high nutrient loads from an urbanised watershed. The small plumes were shallow (<2 m) and strongly buoyant, with sharp vertical and horizontal clines similar to much larger plumes. The edges of the plumes were highly distinct, clearly separating disparate water masses that trapped significantly higher amounts of nutrients inside the plume. Some particulate material exported from the estuary in the plumes reached the benthos of the nearshore zone, as evidenced by increases in copper concentrations in sediments under the plume. By contrast, the amount of land-sourced carbon delivered by small plumes to the seafloor was minor in comparison to larger inputs from marine sources (e.g. onshore advection of phytoplankton blooms or algae dislodged from reefs) that swamped any contribution from plumes. Overall, small plumes can be important in land–ocean coupling, but their zone of influence may be limited.

Modeling the influence of nutrients, turbulence and grazing on Pfiesteria population dynamics

A semi-idealized marine ecosystem model, designed as a heuristic tool for exploring the population dynamics of non-inducible versus toxic forms of Pfiesteria is described. The model is based on empirical evidence suggesting that these differing functional types of Pfiesteria also differ substantially in terms of what they eat and how they utilize it to optimize their growth. Non-inducible strains are similar to other mixotrophic dinoflagellates, whereas toxic strains may consume organic matter and detritus, produce toxins and attack fish. In our model formulation we represent these differences in a simplified way: the non-inducible strain is kleptochloroplastidic and it can take up DIN, but it cannot utilize DON, whereas the toxic strain is heterotrophic, it cannot utilize DIN, but it can utilize DON directly. These differences give rise to very different impacts on prey and nutrient concentrations in our model. Under high DIN/DON ratio conditions, the non-inducible cells grew much faster and were therefore more likely to bloom, but this advantage is substantially mitigated when the DIN/DON ratio is low. A turbulence parameterization was also incorporated into our model. The effect of this was to reduce the grazing rate of Pfiesteria when turbulence levels are high. According to our model, increased turbulence is more detrimental to the toxic functional type because it grows more slowly. The further imposition of microzooplankton grazing in the model showed that top-down control effects can be very significant, which is consistent with both laboratory and field studies and the general idea that plankton blooms can only happen in the absence of substantial grazing control. In general, our model results suggest that non-toxic blooms are more likely to occur in more turbulent inorganic-nutrient rich conditions, which are often found in more open coastal and estuarine waters that are subject to high inorganic loading. In contrast, toxic blooms are more likely to occur in calm, organic-nutrient rich conditions, which are often found in shallow, protected tributaries that are subject to high organic nutrient loading. Our model results also support the idea that the absence of strong grazing pressure is a prerequisite to bloom formation for both non-inducible and toxic strains of Pfiesteria. These results are generally consistent with observed patterns of toxic Pfiesteria blooms in Chesapeake Bay, the Neuse River of North Carolina and many other coastal and estuarine environments.

Neural network training: Using untransformed or log‐transformed training data for the inversion of ocean colour spectra?

A bio‐optical model coupled with the radiative transfer model Hydrolight was used to create 18,000 synthetic ocean colour spectra corresponding to open ocean and coastal waters. The bio‐optical model took into account the optical properties of the three oceanic constituents, chlorophyll‐a, suspended non‐chlorophyllous particles and coloured dissolved organic matter (CDOM) as well as of normal seawater. The resulting spectra were input into multilayer perceptron neural network algorithms with the aim of computing the original concentrations of chlorophyll‐a, non‐chlorophyllous particles and CDOM initially input into the bio‐optical model. The process of training the neural networks is essential for the accuracy of the inversion the neural net performs on the coupled bio‐optical and radiative transfer models. The objective of this paper is to investigate the performance difference of a neural network trained with untransformed as opposed to logarithmically transformed data.

Stability of eelgrass (Zostera marina L.) depth limits: influence of habitat type

Seagrass meadows are generally considered stable although few studies have specified and tested this statement. On the basis of a large monitoring dataset from Danish coastal waters, we aimed to test whether the stability of deep eelgrass populations changes along a eutrophication gradient extending from inner bays over outer bays to open coastal waters. We defined stability in terms of the ‘stability properties’ of ‘constancy’, ‘resilience’, and/or ‘persistence’. Our data allowed us to investigate the stability property constancy expressed as temporal variability in eelgrass depth limits over a time scale of 10 years. We hypothesised that colonisation depths were large and relatively constant along open coasts because of low and relatively constant levels of nutrients and turbidity. Conversely, colonisation depths were hypothesised to be low and variable in protected bays due to higher and more variable levels of nutrients and turbidity. We found that depth limits increased from inner bays towards open coastal waters, matching declines in nutrient concentration and increases in water clarity and oxygen concentration. Stability expressed as constancy of depth limits did not differ significantly between habitat types, and neither did stability of physicochemical variables. However, when data from all habitat types were analysed together, they showed that eelgrass populations at the depth limit were significantly more constant and thus, in this respect, more stable when occurring in deep waters as compared to shallow waters. Areas of good water quality may thus obtain the double benefit of deeper-growing and more stable eelgrass populations. The most likely reason why this pattern did not appear at habitat-type level is that the habitat types studied represented wide spatial variation in water quality and depth limit. We conclude that the question of whether eelgrass populations are stable depends on the stability property and the ecological situation in question. Populations may be considered unstable in terms of inter-annual variation but stable in terms of long-term persistence. Therefore, the common statement that eelgrass populations are stable is not universally true.

Reframing the ‘Everything is everywhere’ debate: evidence for high gene flow and diversity in ciliate morphospecies

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 41:55-65 (2005) - doi:10.3354/ame041055 Reframing the ‘Everything is everywhere’ debate: evidence for high gene flow and diversity in ciliate morphospecies Laura A. Katz1, 2, *, George B. McManus3, Oona L. O. Snoeyenbos-West1, 5, Autumn Griffin1, Katarzyna Pirog1, Barbara Costas3, Wilhelm Foissner4 1Department of Biological Sciences, Smith College, College Road, Northampton, Massachusetts 01063, USA2Program in Organismic and Evolutionary Biology, University of Massachusetts-Amherst, 611 N. Pleasant Street, Amherst, Massachusetts 01003, USA3Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Rd., Groton, Connecticut 06340, USA4Institut für Zoologie, Universität Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria5Present address: Dept of Plant, Soil and Insect Sciences, Fernald Hall, UMASS Amherst, Amherst, Massachusetts 01003, USA *Email: lkatz@smith.edu ABSTRACT: Current debate on microbial diversity contrasts the ‘cosmopolitan’ hypothesis, which argues for high gene flow and low diversity, with the ‘endemism’ hypothesis, which argues for high diversity and geographically restricted gene flow. Our analyses of genetic variation in ciliate morphospecies isolated from ephemeral environments (freshwater ponds and tide pools) redefine this debate. In 2 different clades of oligotrich ciliates (in the genera Halteria/Meseres and Strombidium), we found both high levels of diversity and evidence of high gene flow as indicated by the presence of identical haplotypes across broad geographic ranges. Five recognizable morphospecies of Halteria/Meseres were found to be composed of 7 different clades, differing by as much as 7.6% sequence divergence at the ITS locus (ITS1, ITS2 and 5.8S rDNA). Two recognizable morphospecies of Strombidium (S. oculatum and S. stylifer) resolved into 10 distinct clades, differing by as much as 15.7% at the same locus. For both groups of ciliates, the genetic divergence underlying these morphospecies may be related to cycles of isolation in their ephemeral habitats (freshwater lakes and ponds for Halteria/Meseres and tide pools for Strombidium). By comparison, there is both low diversity and highgene flow in published data on ciliates from open coastal water (Laboea strobila and several species of tintinnids), a more stable environment over evolutionary time-scales. Our analyses indicate that models of microbial diversity must test for ecologically driven patterns in the interactions of gene flow and species richness to account for observed patterns of high dispersal and high gene flow. KEY WORDS: Ciliate phylogeography · Endemism · Cosmopolitanism · Gene flow · Cryptic species Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 41, No. 1. Online publication date: November 11, 2005 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2005 Inter-Research.

Patterns of Species Number and Abundance in Macroalgal Communities in Coastal Waters

Predictable patterns of species number have been observed in relation to habitat size, habitat heterogeneity and environmental conditions, while patterns in relative abundance of species have been examined for few communities and no assembly rules have been established. We studied communities of attached macroalgae in 61 individual sites located in four different areas; the inner, middle and outer parts of three neighbouring low-tidal estuaries and the adjacent open waters of the Kattegat, Denmark. The objectives were to determine (1) the relationships of species number and rank-abundance to the environmental conditions, and (2) the importance of scale and the consistency of species rank number at the sites for these relationships. We found that species number increased significantly from the inner estuaries to the open coastal waters along with decreasing nutrient concentrations. Turnover (β) diversity was lowest in the open waters suggesting that species composition was more similar among samples there than in the estuaries. Rank-abundance curves did not differ between depth intervals and individual sites across the environmental gradients. However, the summed rank-abundance patterns for two sites showed significantly steeper initial slopes and dominance of few species (i.e., low evenness) in the inner estuaries than in open waters. This pattern was due to high rank consistency of dominant species among sites in the inner estuaries. In open waters rank consistency was low, and the summed abundance across sites showed an even abundance of species. The results imply that the scale of the study and the community variability observed at that particular scale, is the main determinant of abundance patterns.

ABUNDANCE OF INDO‐PACIFIC BOTTLENOSE DOLPHINS, TURSIOPS ADUNCUS, OFF POINT LOOKOUT, QUEENSLAND, AUSTRALIA

AbstractManaging escalating human impacts on nearshore cetaceans requires information on a species' demography and distribution patterns at appropriate spatial scales. Identification photographs of individuals of a population of inshore Indo‐Pacific bottlenose dolphins, Tursiops aduncus, were obtained in the open coastal waters off North Stradbroke Island, Australia and used to estimate population density and residency. Five hundred and eighty‐one individuals were identified from 342 school sightings during 1998 and 1999. Mark‐recapture analysis using closed population models estimated a population size of between 700 and 1,000 individuals within the study area during winter, with evidence that the population contained resident individuals. This represents an extremely high number of dolphins within a small area, which requires a pre‐emptive management strategy to ensure their continued occupancy.

Evidence of connectivity between juvenile and adult habitats for mobile marine fauna: an important component of nurseries

A critical link missing from our understanding of the nursery role of specific marine habitats is the evidence of connectivity between juvenile and adult habitats. This paper reviews and evaluates evidence of, and spatial scales for, movements from juvenile to adult habitats and it sum- marises the methods used to study movements. Examples include many fish families but few inverte- brate taxa, and most are species of economic importance for USA and Australia. The types of juvenile habitat range from the entire estuary or shallow open coastal waters to specific habitats within estu- aries or coastal waters; in some cases juvenile habitats include habitats not traditionally regarded as nursery areas (e.g. the surf zone). The duration of time spent in juvenile habitats averages 13 mo (range 8 d to 5 yr). The majority of organisms move distances of kilometres to hundreds of kilometres from juvenile to adult habitats, although the scale of movements ranged from metres to thousands of kilometres. Changes in abundance among separate habitats and the progression of size classes among separate habitats are the main methods used to infer movement and habitat connectivity. Spa- tial partitioning of stages of maturity, natural parasites, and a variety of artificial tagging methods have also been used. The latter will become more useful with continued developments in the minia- turisation of artificial tags. More recent studies have used natural tags (e.g. trace elements and stable isotopes) and these methods show great promise for determining movements from juvenile to adult habitats. Few studies provide good evidence for movement from specific juvenile habitats to adult habitats. Future studies need to focus on this movement to supplement data on density, growth and survival of organisms in putative nursery habitats. Such information will allow management and con- servation efforts to focus on those habitats that make the greatest contribution to adult populations.

Early sea mortality of mark-recaptured juvenile chum salmon in open coastal waters

Early sea mortality of mark-recaptured juvenile chum salmon in open coastal waters

Early sea mortality of mark‐recaptured juvenile chum salmon in open coastal waters

Estimates of instantaneous mortality rate of mark‐recaptured chum salmon Oncorhynchus keta juveniles in coastal waters of the Sea of Japan ranged from 0·033 to 0·268 day−1 in the 14–43 days after release. High mortality rate may have been caused by size‐selective mortality or poor ability to adapt to the coastal environment inhabited by chum salmon juveniles soon after release. The results indicated that large‐scale mark‐recapture experiments are useful for estimating mortality during the early sea life that is considered to be a critical period for Pacific salmon.

A comparison of visual observations of surface oil with Synthetic Aperture Radar imagery of the Sea Empress oil spill

A comparison has been made between the visual observations of surface oil and four satellite-borne Synthetic Aperture Radar (SAR) images taken during the Sea Empress oil spill in February 1996. Whilst the basic oil slick imaging capabilities of SAR are well documented, to be of use at the time of a major oil spill, the imagery must be able to provide information on the thickness of oil. This analysis suggests that, under certain environmental conditions, this is possible. The optimum wind speed for the identification of heavy surface oil is around 5-6 m s-1 . At this wind speed, light and medium sheen is not evident in the imagery and there is a distinction between the backscatter reductions due to heavy sheen and thick brown/black oil. At higher wind speeds, even thick oil slicks readily mix into the water column and their SAR signature weakens. In light winds, pattern recognition is very important to the identification of oil slicks. The images are more sensitive to the presence of sheen within the sheltered waters of Milford Haven than in the open coastal waters, indicating a possible relationship between sheen visibility in satellite-borne SAR and sea state.

Increased marine production of N2O due to intensifying anoxia on the Indian continental shelf.

Eutrophication of surface waters and hypoxia in bottom waters has been increasing in many coastal areas, leading to very large depletions of marine life in the affected regions. These areas of high surface productivity and low bottom-water oxygen concentration are caused by increasing runoff of nutrients from land. Although the local ecological and socio-economic effects have received much attention, the potential contribution of increasing hypoxia to global-change phenomena is unknown. Here we report the intensification of one of the largest low-oxygen zones in the ocean, which develops naturally over the western Indian continental shelf during late summer and autumn. We also report the highest accumulations yet observed of hydrogen sulphide (H2S) and nitrous oxide (N2O) in open coastal waters. Increased N2O production is probably caused by the addition of anthropogenic nitrate and its subsequent denitrification, which is favoured by hypoxic conditions. We suggest that a global expansion of hypoxic zones may lead to an increase in marine production and emission of N2O, which, as a potent greenhouse gas, could contribute significantly to the accumulation of radiatively active trace gases in the atmosphere.

Simulation of MERIS measurements above selected ocean waters

We report on a number of radiative transfer calculations that have been performed in order to predict Medium Resolution Imaging Spectrometer (MERIS) measurements for the anticipated spectral bands and observation geometries for selected open ocean and coastal waters. The simulations show that, above coastal waters, significant levels of the water-leaving radiance must be expected in several of the MERIS channels dedicated to the atmospheric correction. These channels should be included in the algorithms to retrieve concentrations of water constituents. In addition, sunglint may affect large parts of MERIS satellite images, especially in the lower latitudes between ca 20 N and 20 S. Radiative transfer calculations similar to those presented here are used to derive algorithms for the assessment of constituent concentrations in Case II waters from ocean colour measurements.

Climatically influenced distribution of Gymnodinium catenatum during the past 2000 years in coastal sediments of southern Norway

Dinoflagellate cyst analysis of cored late Holocene sediments from the Norwegian coast of the Skagerrak and northern North Sea confirms the conclusions of previous studies from the Kattegat that climate influenced the quantitative distribution of Gymnodinium catenatum Graham 1943. These studies provide some of the first data on the effect of small-scale climatic changes on one component of the phytoplankton during the past 2000 years. In core 9310 from the Skagerrak, as in previous cores from the Kattegat, G. catenatum cysts increase proportionally from about AD 0 to peak amounts at about AD 900, 1200 and 1450 corresponding to periods of relatively warmer climate. Proportional decreases in G. catenatum correspond to periods of cooler climate in the 900s and 1300s, and to the colder climate of the Little Ice Age climax in the 1600s. In the site of core 9307 from the North Sea coast higher proportions of G. catenatum (15%) were probably reached between 300 and 1000 years later than in the other cores, due to the location of this site being closer to the biogeographic limit for high proportions of the species. New results also suggest that high proportions of the species (2–58%) were confined to open coastal waters south of Bergen, Norway. Living and fossil cysts of G. catenatum in this region are small compared with reported sizes elsewhere (24–40 vs. 37–60 μm), and may not be conspecific with G. catenatum. Irrespective of their taxonomy, the quantitative distribution of these cysts is influenced by climatic changes, and they are a reliable indicator of warmer water in more open coastal waters of Scandinavia during the late Holocene.

Potential Effects of Canada Geese and Climate Change on Phosphorus Inputs to Suburban Lakes of the Northeastern U.S.A.

ABSTRACT Inputs of total phosphorus (TP) to a small lake (0.4 km2) located in western suburban Boston were compared during a drought (fall 1995) and a normal rainfall period (fall 1994) to explore potential effects of Canada geese (Branta canadensis maxima) and climate change on phosphorus loading to suburban lakes of the Northeastern U.S.A. In fall 1994, the watershed supplied 18 times more TP than Canada geese, but during the fall drought of 1995, TP from Canada geese exceeded that from the watershed by more than 7 times. Differences in the relative importance of TP loading from Canada geese and the watershed were caused by variation in streamflow between years. Under conditions of climatic warming, annual streamflow in the Northeast (U.S.A.) is projected to decline by ~30% with greatest reductions (~60%) occurring in the fall. At this time of year, Canada geese are most abundant and are likely to become the major contributor of TP to urban lakes. Furthermore, annual absolute inputs of TP from geese to suburban and urban lakes of the Northeast are likely to increase with warmer conditions associated with climate change, because ice cover in winter is unlikely to form on lakes in this region. Consequently, geese are likely to remain on such lakes during the winter rather than moving to open coastal waters as they do presently when lakes freeze. Thus, both the warmer and drier conditions predicted to accompany climate change may exacerbate effects of Canada geese on the water quality of suburban-urban lakes in this region of North America.

Seasonal and fine-scale spatial variations in egg production and triacylglycerol content of the copepod Acartia tonsa in a river-dominated estuary and its coastal plume

We measured egg production rates of the estuarine calanoid copepod Acartia tonsa in Mobile Bay, an estuary in the northern Gulf of Mexico. Two stations were sampled approximately monthly, one at the mouth of the bay and the other just beyond the mouth in the salinity front between bay and coastal waters. Over the whole year, temperature was the most important environmental variable controlling egg production. Rates increased with temperature up to 30°C and 140 eggs female1 day-'. We found no evidence of food limitation. There was no correlation between egg production and phytoplankton abundance, nor increased egg production in response to supplements of phytoplankton added to natural food, suggesting that non-phytoplankton food was important in the diet. At the highest egg production rates, the amount of the storage lipid triacylglycerol (TAG) in adult females was greatly diminished, to <50 ng female1. This suggests that lipids in the diet can be very tightly coupled to egg production. Both egg production and TAG content of females showed significant variability on spatial scales of 3-15 km, especially in relation to the salinity front separat- ing water outwelling from the bay from open coastal water. For organisms that are using copepods and their eggs as food, this variability would result in a heterogeneous food environment, both in terms of the abundance of food and its nutritional content.

Effect of Danube River dam on Black Sea biogeochemistry and ecosystem structure

Rivers contribute significantly to the pollution and eutrophication that have caused drastic changes to the ecosystem of the Black Sea1–3. Although damming is known to affect riverborne nutrient loads, and thus riverine ecosystems, evidence for significant effects in open coastal waters is sparse4–6. Here we present long-term data sets of water and nutrient discharge from the River Danube to the Black Sea. These data reveal a reduction in the dissolved silicate load of the river by about two-thirds since dam constructions in the early 1970s. A concomitant decrease in wintertime dissolved silicate concentrations by more than 60% was observed in central Black Sea surface waters. The consequent changes in silicon to nitrogen ratio of the Black Sea nutrient load appear to be larger than those caused by eutrophication alone, and seem to be responsible for dramatic shifts in phytoplankton species composition from diatoms (siliceous) to coccolithophores and flagellates (non-siliceous). Our results strongly suggest that the damming of the Danube has been instrumental in causing the observed changes in Black Sea surface waters3,7–9, and that the large number of dams in operation around the world today could similarly affect the food web structure and biogeochemical cycling in coastal seas.

Intertidal Benthic Foraminiferal Biofacies on the Central Gulf Coast of Texas: Modern Distribution and Application to Sea Level Reconstruction

Intertidal Benthic Foraminiferal Biofacies on the Central Gulf Coast of Texas: Modern Distribution and Application to Sea Level Reconstruction

Environmental Monitoring by Remote Sensing in Denmark

Kjeld Rasmussen, Henning Skriver, John Tychsen, Preben Gudmandsen & Morten Olsen: Environmental Monitoring by Remote Sensing in Denmark. Geografisk Tidsskrift, Danish Journal of Geography 94:xx–xx. Copenhagen, Dec. 1994. Danish environmental monitoring of the open sea, coastal waters, lakes, streams, ground water, air and land surfaces is presently based solely on conventional in-situ measurements. This paper discusses the potential for supplementing this programme with remote sensing from space- and aircraft. Three classes of remote sensing applications is identified and discussed: Monitoring of quickly varying parameters, requiring modest spatial resolution, monitoring of slowly varying parameters, requiring high spatial resolution, and ‘on-demand’ aircraft-based remote sensing of environmental phenomena. The discussion leads to a series of suggestions, concerning the potential operational applications in the short term as well as, demonstration experiments and research with a longer time horizon and im...

Peracarid Crustacea Inhabiting Aegagropylae of the Red Alga Rytiphloea Tinctoria (Clemente) C. Ag. in the Stagnone Sound, Western Sicily, Italy

The peracarid Crustacea belonging to Cumacea, Tanaidacca, Isopoda and Amphipoda, inhabiting aegagropylae of Rytiphloea tinctoria were studied throughout a year in the Stagnone Sound (western Sicily, Italy). The dominant groups, tanaids (61.7%) and amphipods (32.8%), were represented by 6 and 28 species, and showed complementary trends during the 12 months, reaching their maximum of abundance in spring and autumn, respectively. Tanaids were mainly represented by Apseudes intermedius Hansen, 1895 and Parapseudes latifrons (Grube, 1864), and amphipods by Elasmopus pocillimanus (Bate, 1862), Leptocheirus guttatus (Grube, 1864), Lysianassa longicornis Lucas, 1849 and Maera inaequipes (A. Costa, 1857). These species, often found in open coastal waters, showed different seasonal trends in the Stagnone, probably in relation to their ecological requirements and life cycle. Evidence is provided that these aegagropyla formations are not only a temporary refuge for the peracaridan communities in the sometimes stressed environmental conditions of the Stagnone. In fact, they are a complex microcommunity where species are present constantly in both sexes and at all stages of development. The formations are also the result of an interaction between alga and peracarid crustaceans, which moreover play a major role among the other small invertebrates.