scholarly journals Here are the polyps: in situ observations of jellyfish polyps and podocysts on bivalve shells

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9260 ◽  
Author(s):  
Lodewijk van Walraven ◽  
Judith van Bleijswijk ◽  
Henk W. van der Veer
Keyword(s):  
North Sea ◽  
Natural Environment ◽  
Morphological Characteristics ◽  
Dogger Bank ◽  
The North ◽  
Polyp Stage ◽  
In Situ Observations ◽  
Hard Substrates ◽  
Bivalve Shells

Most Scyphozoan jellyfish species have a metagenic life cycle involving a benthic, asexually reproducing polyp stage and a sexually reproducing medusa stage. Medusae can be large and conspicuous and most can be identified using morphological characteristics. Polyps on the other hand are small, live a cryptic life attached to hard substrates and often are difficult or impossible to distinguish based on morphology alone. Consequently, for many species the polyp stage has not been identified in the natural environment. We inspected hard substrates in various habitats for the presence of Scyphozoan polyps. Three polyps were found on Dogger Bank, Central North Sea, attached to the inside of the umbo of empty valves of the bivalves Mactra stultorum and Spisula subtruncata. One polyp was accompanied by four podocysts. With this knowledge, the inside of bivalve shells washed ashore in Oostende (Belgium) was inspected and supposed podocysts on the inside of empty valves of Cerastoderma edule and Spisula elliptica were found. Polyps and podocysts were identified to species level by 18S rDNA and mitochondrial COI sequencing. The three polyps found on Dogger Bank all belonged to the compass jellyfish Chrysaora hysoscella. One podocyst from the Oostende beach also belonged to this species but another podocyst belonged to Cyanea lamarkii. These are the first in situ observations of C. hysoscella and C. lamarckii polyps and podocysts in the natural environment. Mactra, Cerastoderma and Spisula species are abundant in many North Sea regions and empty bivalve shells could provide an abundant settling substrate for jellyfish polyps in the North Sea and other areas. Several new strategies to increase the detection of polyps on bivalve shells are presented.

scholarly journals Observing and modelling phytoplankton community structure in the North Sea

2017 ◽  
Vol 14 (6) ◽  
pp. 1419-1444 ◽  
Author(s):  
David A. Ford ◽  
Johan van der Molen ◽  
Kieran Hyder ◽  
John Bacon ◽  
Rosa Barciela ◽  
...  
Keyword(s):  
Community Structure ◽  
North Sea ◽  
Phytoplankton Community ◽  
Marine Biodiversity ◽  
Phytoplankton Community Structure ◽  
Pigment Analysis ◽  
The North ◽  
The North Sea ◽  
In Situ Observations

Abstract. Phytoplankton form the base of the marine food chain, and knowledge of phytoplankton community structure is fundamental when assessing marine biodiversity. Policy makers and other users require information on marine biodiversity and other aspects of the marine environment for the North Sea, a highly productive European shelf sea. This information must come from a combination of observations and models, but currently the coastal ocean is greatly under-sampled for phytoplankton data, and outputs of phytoplankton community structure from models are therefore not yet frequently validated. This study presents a novel set of in situ observations of phytoplankton community structure for the North Sea using accessory pigment analysis. The observations allow a good understanding of the patterns of surface phytoplankton biomass and community structure in the North Sea for the observed months of August 2010 and 2011. Two physical–biogeochemical ocean models, the biogeochemical components of which are different variants of the widely used European Regional Seas Ecosystem Model (ERSEM), were then validated against these and other observations. Both models were a good match for sea surface temperature observations, and a reasonable match for remotely sensed ocean colour observations. However, the two models displayed very different phytoplankton community structures, with one better matching the in situ observations than the other. Nonetheless, both models shared some similarities with the observations in terms of spatial features and inter-annual variability. An initial comparison of the formulations and parameterizations of the two models suggests that diversity between the parameter settings of model phytoplankton functional types, along with formulations which promote a greater sensitivity to changes in light and nutrients, is key to capturing the observed phytoplankton community structure. These findings will help inform future model development, which should be coupled with detailed validation studies, in order to help facilitate the wider application of marine biogeochemical modelling to user and policy needs.

Distribution of suspended particulate matter in the North Sea as inferred from NOAA/AVHRR reflectance images and in situ observations

1998 ◽  
Vol 39 (3-4) ◽  
pp. 197-215 ◽  
Author(s):  
W. van Raaphorst ◽  
C.J.M. Philippart ◽  
J.P.C. Smit ◽  
F.J. Dijkstra ◽  
J.F.P. Malschaert
Keyword(s):  
Particulate Matter ◽  
North Sea ◽  
Suspended Particulate Matter ◽  
The North ◽  
Noaa Avhrr ◽  
Suspended Particulate ◽  
The North Sea ◽  
In Situ Observations

scholarly journals Observing and modelling phytoplankton community structure in the North Sea: can ERSEM-type models simulate biodiversity?

2016 ◽  
Author(s):  
David A. Ford ◽  
Johan van der Molen ◽  
Kieran Hyder ◽  
John Bacon ◽  
Rosa Barciela ◽  
...  
Keyword(s):  
Community Structure ◽  
North Sea ◽  
Phytoplankton Community ◽  
Marine Biodiversity ◽  
Phytoplankton Community Structure ◽  
Pigment Analysis ◽  
The North ◽  
The North Sea ◽  
In Situ Observations

Abstract. Phytoplankton form the base of the marine food chain, and knowledge of phytoplankton community structure is fundamental when assessing marine biodiversity. Policy makers and other users require information on marine biodiversity and other aspects of the marine environment for the North Sea, a highly productive European shelf sea. This information must come from a combination of observations and models, but currently the coastal ocean is greatly under-sampled for phytoplankton data, and outputs of phytoplankton community structure from models have therefore yet to be properly validated. This study presents a novel set of in situ observations of phytoplankton community structure for the North Sea using accessory pigment analysis. The observations allow a good understanding of the patterns of surface phytoplankton biomass and community structure in the North Sea for the observed months of August 2010 and 2011. Two physical-biogeochemical ocean models, the biogeochemical components of which are different variants of the widely-used European Regional Seas Ecosystem Model (ERSEM), were then validated against these and other observations. Both models were a good match for sea surface temperature observations, and a reasonable match for remotely sensed ocean colour observations. However, the two models displayed very different phytoplankton community structures, with one better matching the in situ observations than the other. Nonetheless, both models shared some similarities with the observations in terms of spatial features and inter-annual variability. A comparison of the formulations and parameterisations of the two models suggests that diversity between the parameter settings of model phytoplankton functional types, along with formulations which promote a greater sensitivity to changes in light and nutrients, is key to capturing the observed biodiversity. These findings will help inform future model development, which should be coupled with detailed validation studies, in order to help facilitate the wider application of marine biogeochemical modelling to user and policy needs.

scholarly journals Sea Surface Temperature Climate Data Record for the North Sea and Baltic Sea

2016 ◽  
Vol 29 (7) ◽  
pp. 2529-2541 ◽  
Author(s):  
Jacob L. Høyer ◽  
Ioanna Karagali
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
Climate Data ◽  
The North ◽  
Data Record ◽  
The North Sea ◽  
In Situ Observations ◽  
The Baltic ◽  
Climate Data Record

Abstract A 30-yr climate data record (CDR) of sea surface temperature (SST) has been produced with daily gap-free analysis fields for the North Sea and the Baltic Sea region from 1982 to 2012 by combining the Pathfinder AVHRR satellite data record with the Along-Track Scanning Radiometer (ATSR) Reprocessing for Climate (ARC) dataset and with in situ observations. A dynamical bias correction scheme adjusts the Pathfinder observations toward the ARC and in situ observations. Largest Pathfinder–ARC differences are found in the summer months, when the Pathfinder observations are up to 0.4°C colder than the ARC observations on average. Validation against independent in situ observations shows a very stable performance of the data record, with a mean difference of −0.06°C compared to moored buoys and a 0.46°C standard deviation of the differences. The mean annual biases of the SST CDR are small for all years, with a negligible temporal trend when compared against drifting and moored buoys. Analysis of the SST CDR reveals that the monthly anomalies for the North Sea, the Danish straits, and the central Baltic Sea regions show a high degree of correlation for interannual and decadal time scales, whereas the monthly variability differs from one region to another. The linear trends of the 1982–2012 SST anomaly time series range from 0.037°C yr−1 for the North Sea to 0.041°C yr−1 for the Baltic Sea.

Internal solitons in the north-ern South China Sea from in-situ observations

2005 ◽  
Vol 50 (15) ◽  
pp. 1627 ◽  
Author(s):  
Wendong FANG
Keyword(s):  
South China Sea ◽  
South China ◽  
China Sea ◽  
The North ◽  
In Situ Observations

scholarly journals Effect of Temperature on Stiffness of Sandstones from the Deep North Sea Basin

2020 ◽  
Author(s):  
Tobias Orlander ◽  
Katrine Alling Andreassen ◽  
Ida Lykke Fabricius
Keyword(s):  
North Sea ◽  
Temperature Effects ◽  
Mass Density ◽  
Thermal Strain ◽  
High Stress ◽  
Testing Temperature ◽  
Effect Of Temperature ◽  
Stress Regime ◽  
The North

Abstract Development of high-pressure, high-temperature (HPHT) petroleum reservoirs situated at depths exceeding 5 km and in situ temperature of 170 °C increases the demand for theories and supporting experimental data capable of describing temperature effects on rock stiffness. With the intention of experimentally investigating temperature effects on stiffness properties, we investigated three sandstones from the deep North Sea Basin. As the North Sea Basin is presently undergoing substantial subsidence, we assumed that studied reservoir sandstones have never experienced higher temperature than in situ. We measured ultrasonic velocities in a low- and high-stress regime, and used mass density and stress–strain curves to derive, respectively, dynamic and static elastic moduli. We found that in both regimes, the dry sandstones stiffens with increasing testing temperature and assign expansion of minerals as a controlling mechanism. In the low-stress regime with only partial microcrack closure, we propose closure of microcracks as the stiffening mechanism. In the high-stress regime, we propose that thermal expansion of constituting minerals increases stress in grain contacts when the applied stress is high enough for conversion of thermal strain to thermal stress, thus leading to higher stiffness at in situ temperature. We then applied an extension of Biot’s effective stress equation including a non-isothermal term from thermoelastic theory and explain test results by adding boundary conditions to the equations.

scholarly journals In situ observations of aerosol particles remaining from evaporated cirrus crystals: Comparing clean and polluted air masses

2002 ◽  
Vol 2 (5) ◽  
pp. 1599-1633 ◽  
Author(s):  
M. Seifert ◽  
J. Ström ◽  
R. Krejci ◽  
A. Minikin ◽  
A. Petzold ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Aerosol Particles ◽  
Pollution Level ◽  
Size Distributions ◽  
Number Density ◽  
Particle Volume ◽  
The North ◽  
In Situ Observations

Abstract. In situ observations of aerosol particles contained in cirrus crystals are presented and compared to interstitial aerosol size distributions (non-activated particles in between the cirrus crystals). The observations were conducted in cirrus clouds in the Southern and Northern Hemisphere mid-latitudes during the INCA project. The first campaign in March and April 2000 was performed from Punta Arenas, Chile (54° S) in pristine air. The second campaign in September and October 2000 was performed from Prestwick, Scotland (53° N) in the vicinity of the North Atlantic flight corridor. Size distribution measurements of crystal residuals (particles remaining after evaporation of the crystals) show that small aerosol particles (Dp < 0.1µm) dominate the number density of residuals. The crystal residual size distributions were significantly different in the two campaigns. On average the residual size distributions were shifted towards larger sizes in the Southern Hemisphere. For a given integral residual number density, the calculated particle volume was on average three times larger in the Southern Hemisphere. This may be of significance to the vertical redistribution of aerosol mass by clouds in the tropopause region. In both campaigns the mean residual size increased with increasing crystal number density. The observations of ambient aerosol particles were consistent with the expected higher pollution level in the Northern Hemisphere. The fraction of residual particles only contributes to approximately a percent or less of the total number of particles, which is the sum of the residual and interstitial particles.

scholarly journals Connectivity of larval stages of sedentary marine communities between hard substrates and offshore structures in the North Sea

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Johan van der Molen ◽  
Luz María García-García ◽  
Paul Whomersley ◽  
Alexander Callaway ◽  
Paulette E. Posen ◽  
...  
Keyword(s):  
North Sea ◽  
Offshore Structures ◽  
Marine Communities ◽  
Larval Stages ◽  
The North ◽  
The North Sea ◽  
Hard Substrates
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