The Experts below are selected from a list of 5097 Experts worldwide ranked by ideXlab platform

Lori Bronars - One of the best experts on this subject based on the ideXlab platform.

Mati Kahru - One of the best experts on this subject based on the ideXlab platform.

  • multidecadal time series of satellite detected accumulations of cyanobacteria in the baltic sea
    Biogeosciences, 2014
    Co-Authors: Mati Kahru, Ragnar Elmgren
    Abstract:

    Cyanobacteria, primarily of the species \textit{Nodularia spumigena}, form extensive surface accumulations in the Baltic Sea in July and August, ranging from diffuse flakes to dense surface scums. The area of these accumulations can reach ~ 200 000 km 2 . We describe the compilation of a 35-year-long time series (1979–2013) of cyanobacteria surface accumulations in the Baltic Sea using multiple satellite sensors. This appears to be one of the longest satellite-based time series in Biological Oceanography. The satellite algorithm is based on remote sensing reflectance of the water in the red band, a measure of turbidity. Validation of the satellite algorithm using horizontal transects from a ship of opportunity showed the strongest relationship with phycocyanin fluorescence (an indicator of cyanobacteria), followed by turbidity and then by chlorophyll a fluorescence. The areal fraction with cyanobacteria accumulations (FCA) and the total accumulated area affected (TA) were used to characterize the intensity and extent of the accumulations. The fraction with cyanobacteria accumulations was calculated as the ratio of the number of detected accumulations to the number of cloud-free sea-surface views per pixel during the season (July–August). The total accumulated area affected was calculated by adding the area of pixels where accumulations were detected at least once during the season. The fraction with cyanobacteria accumulations and TA were correlated ( R 2 = 0.55) and both showed large interannual and decadal-scale variations. The average FCA was significantly higher for the second half of the time series (13.8%, 1997–2013) than for the first half (8.6%, 1979–1996). However, that does not seem to represent a long-term trend but decadal-scale oscillations. Cyanobacteria accumulations were common in the 1970s and early 1980s (FCA between 11–17%), but rare (FCA below 4%) during 1985–1990; they increased again starting in 1991 and particularly in 1999, reaching maxima in FCA (~ 25%) and TA (~ 210 000 km 2 ) in 2005 and 2008. After 2008, FCA declined to more moderate levels (6–17%). The timing of the accumulations has become earlier in the season, at a mean rate of 0.6 days per year, resulting in approximately 20 days advancement during the study period. The interannual variations in FCA are positively correlated with the concentration of chlorophyll a during July–August sampled at the depth of ~ 5 m by a ship of opportunity, but interannual variations in FCA are more pronounced as the coefficient of variation is over 5 times higher.

Ragnar Elmgren - One of the best experts on this subject based on the ideXlab platform.

  • multidecadal time series of satellite detected accumulations of cyanobacteria in the baltic sea
    Biogeosciences, 2014
    Co-Authors: Mati Kahru, Ragnar Elmgren
    Abstract:

    Cyanobacteria, primarily of the species \textit{Nodularia spumigena}, form extensive surface accumulations in the Baltic Sea in July and August, ranging from diffuse flakes to dense surface scums. The area of these accumulations can reach ~ 200 000 km 2 . We describe the compilation of a 35-year-long time series (1979–2013) of cyanobacteria surface accumulations in the Baltic Sea using multiple satellite sensors. This appears to be one of the longest satellite-based time series in Biological Oceanography. The satellite algorithm is based on remote sensing reflectance of the water in the red band, a measure of turbidity. Validation of the satellite algorithm using horizontal transects from a ship of opportunity showed the strongest relationship with phycocyanin fluorescence (an indicator of cyanobacteria), followed by turbidity and then by chlorophyll a fluorescence. The areal fraction with cyanobacteria accumulations (FCA) and the total accumulated area affected (TA) were used to characterize the intensity and extent of the accumulations. The fraction with cyanobacteria accumulations was calculated as the ratio of the number of detected accumulations to the number of cloud-free sea-surface views per pixel during the season (July–August). The total accumulated area affected was calculated by adding the area of pixels where accumulations were detected at least once during the season. The fraction with cyanobacteria accumulations and TA were correlated ( R 2 = 0.55) and both showed large interannual and decadal-scale variations. The average FCA was significantly higher for the second half of the time series (13.8%, 1997–2013) than for the first half (8.6%, 1979–1996). However, that does not seem to represent a long-term trend but decadal-scale oscillations. Cyanobacteria accumulations were common in the 1970s and early 1980s (FCA between 11–17%), but rare (FCA below 4%) during 1985–1990; they increased again starting in 1991 and particularly in 1999, reaching maxima in FCA (~ 25%) and TA (~ 210 000 km 2 ) in 2005 and 2008. After 2008, FCA declined to more moderate levels (6–17%). The timing of the accumulations has become earlier in the season, at a mean rate of 0.6 days per year, resulting in approximately 20 days advancement during the study period. The interannual variations in FCA are positively correlated with the concentration of chlorophyll a during July–August sampled at the depth of ~ 5 m by a ship of opportunity, but interannual variations in FCA are more pronounced as the coefficient of variation is over 5 times higher.

Suree Satapoomin - One of the best experts on this subject based on the ideXlab platform.

  • Biological Oceanography across the southern indian ocean basin scale trends in the zooplankton community
    Deep Sea Research Part I: Oceanographic Research Papers, 2013
    Co-Authors: Sigrun Jonasdottir, Torkel Gissel Nielsen, Christian Marc Andersen Borg, Eva Friis Moller, Hans Henrik Jakobsen, Suree Satapoomin
    Abstract:

    We present a study on the protozooplankton > 5 mu m and copepods larger than 50 mu m at a series of contrasting stations across the Southern Indian Ocean (SIO). Numerically, over 80% of the copepod community across the transect was less than 650 mu m in size, dominated by nauplii, and smaller copepods, while 80% of the biomass (as mg C m(-3)) was larger than 1300 mu m in body length. Predation by the carnivorous copepod Corycaeus sp. was estimated to be able to remove up to 2% d(-1) of the copepods < 1000 mu m in size. By the help of grazing models we estimated that primary producers were mainly grazed upon by ciliates and heterotrophic dinoflagellates (40-80% d(-1) combined) in temperate waters but appendicularians became increasingly important in the tropical waters grazing about 40% of the biomass per day. Despite their high abundance and biomass, copepods contributed less than 20% of the grazing at most stations. Secondary production was low (carbon specific egg production < 0.14 d(-1)) but typical for food limited oligotrophic oceans.

Jonathan Sharples - One of the best experts on this subject based on the ideXlab platform.

  • introduction to the physical and Biological Oceanography of shelf seas
    2012
    Co-Authors: John H Simpson, Jonathan Sharples
    Abstract:

    Preface 1. Introduction to the shelf seas 2. Physical forcing of the shelf seas: what drives the motion of ocean? 3. Response to forcing: the governing equations and some basic solutions 4. Waves, turbulent motions and mixing 5. Life in the shelf seas 6. Seasonal stratification and the spring bloom 7. Interior mixing and phytoplankton survival in stratified environments 8. Tidal mixing fronts: their location, dynamics and Biological significance 9. Regions of freshwater influence (ROFIs) 10. The shelf edge system 11. Future challenges in shelf seas References Index.

  • introduction to the physical and Biological Oceanography of shelf seas introduction to the shelf seas
    2012
    Co-Authors: John H Simpson, Jonathan Sharples
    Abstract:

    In this chapter we shall introduce the reader to the shelf seas, their extent and position in the global ocean and the motivation, both fundamental and applied, behind our efforts to understand and model the complex processes which control the shelf sea environment and ecosystem. We shall then briefly explain the historical development of shelf sea science and describe the technical tools which are now available and which have facilitated the relatively rapid advances of recent years. As well as discussing the principal observational techniques, in a final section we shall consider the role of numerical modelling and its potential contribution to developing understanding. Definition and relation to the global ocean Between the deep oceans and the continents lie the seas of the continental shelf. These shallow areas usually have rather flat seafloors and extend out to the shelf break, where the seabed inclination generally increases rapidly at the top of the continental slope leading down to the abyssal ocean. This abrupt change of slope is clear in the map of global bathymetry shown in Fig. 1.1a. It typically occurs at a depth of ~200 metres and a contour, or isobath, at this depth is often taken as defining the outer limit of the shelf seas. This choice is not critical, however, since the continental slope is so steep (~1:10); moving from the 200- to the 500-metre isobath involves little horizontal movement. Using the basis of a 500-metre definition, Fig. 1.2a shows that the shelf seas account for ~9% of the total area of the global ocean and less than 0.5% of the volume. The shelf seas have an influence and importance quite out of proportion to these numbers.

  • Introduction to the Physical and Biological Oceanography of Shelf Seas: Life in the shelf seas
    Introduction to the Physical and Biological Oceanography of Shelf Seas, 2026
    Co-Authors: John H Simpson, Jonathan Sharples
    Abstract:

    Much of the physics in the preceding chapters can be traced back to the fundamentals of fluid flow encapsulated in the equations of motion and continuity, along with the eddy description of turbulence. By contrast, describing the basics of life in the sea presents us with the difficulty of trying to distil a broad set of concepts from a system which is inherently very complex. Our experience of working at sea alongside biologists has been stimulating and fruitful, but there is always a tension: physicists can get exasperated at the complexity of the systems that biologists like to describe, while the biologists roll their eyes at the physicists’ insistence on boiling problems down to as simple a level as possible. In this chapter we will take more of a physicist's view of biology in the ocean, focusing mainly on those aspects of the biology that are relevant to understanding how organisms’ access to resources and growth are controlled by the structure and motion of the fluid environment. Broadly, we are aiming to understand how organic compounds are produced in the ocean, and their fate. The schematic illustration of Fig. 5.1 provides us with a framework for the chapter; you could also have a look at the final schematic in Fig. 5.19 if you would like some idea of the details that we will be adding to this framework. We will begin by describing the fundamental biochemistry that lies at the heart of the growth of the autotrophs , the single-celled, photosynthesising phytoplankton which produce the organic matter and so power both the rest of life in the ocean and the cycling of carbon. In contrast, the heterotrophs consume organic material, either recycling it back to inorganic matter or passing it further up the food chain by being food for larger heterotrophs. Heterotrophs are much more varied in form and in their methods used for finding and consuming their prey, so instead of trying to detail this variety we will identify their broad roles in the ecosystem and some of the constraints that life in a turbulent fluid imposes on them. The Biological processes that we will describe are in general common to the open ocean and to the shelf seas. We will use shelf sea examples to illustrate the processes, and identify where the important contrasts are between shelf and open ocean biology.