scholarly journals Marine turf of an invasive alga expels lugworms from the lower shore

2021 ◽  
Vol 169 (1) ◽  
Author(s):  
Karsten Reise ◽  
Dagmar Lackschewitz ◽  
K. Mathias Wegner
Keyword(s):  
North Sea ◽  
Wadden Sea ◽  
Benthic Fauna ◽  
Algal Turf ◽  
The Novel ◽  
Mosaic Pattern ◽  
Arenicola Marina ◽  
Lower Shore ◽  
Tide Level ◽  
Invasive Alga

AbstractBare sandy flats at and below low tide level of the Wadden Sea (eastern North Sea, European Atlantic) were observed in 2020 to have been invaded by an introduced grass-like alga, Vaucheria cf. velutina (Xanthophyceae). A dense algal turf accumulated and stabilized mud, where resident seniors of the lugworm Arenicola marina had reworked rippled sand. Algae and worms were incompatible. Initially, rising patches with algal turf alternated with bare pits where lugworms crowded. Their bioturbation inhibited young algae, while the felt of established algal rhizoids clogged feeding funnels of worm burrows. Eventually, a mosaic pattern of competitors gave way to a coherent algal turf without lugworms. Concomitantly, a rich small-sized benthic fauna took advantage of the novel algal turf. This exotic Vaucheria may have the potential for drastically altering the ecological web at the lower shore.

scholarly journals Marine Turf of an Invasive Alga Ousts Lugworms From Lower Shore

2021 ◽  
Author(s):  
Karsten Reise ◽  
Dagmar Lackschewitz
Keyword(s):  
North Sea ◽  
Wadden Sea ◽  
Benthic Fauna ◽  
Algal Turf ◽  
The Novel ◽  
Mosaic Pattern ◽  
Arenicola Marina ◽  
Lower Shore ◽  
Tide Level ◽  
Invasive Alga

Abstract Bare sandy flats at and below low tide level were observed in 2020 to have been invaded by an introduced grass-like alga, Vaucheria cf. velutina (Xanthophyceae). A dense algal turf accumulated and stabilized mud where resident seniors of the lugworm Arenicola marina had reworked rippled sand. Algae and worms were incompatible. Initially, rising patches with algal turf alternated with bare pits where lugworms crowded. Their bioturbation inhibited young algae, while the felt of established algal rhizoids clogged feeding funnels of worm burrows. Eventually, the mosaic pattern of competitors gave way to a coherent algal turf without lugworms. Concomitantly, a rich small-sized benthic fauna took advantage of the novel algal turf. This exotic Vaucheria has the potential for taking over at the lower shore of the Wadden Sea (eastern North Sea, European Atlantic).

scholarly journals Monitoring juvenile stocks of flatfish in the Wadden Sea and the coastal areas of the southeastern North Sea

1989 ◽  
Vol 43 (3-4) ◽  
pp. 461-477 ◽  
Author(s):  
F. A. Beek ◽  
A. D. Rijnsdorp ◽  
R. Clerck
Keyword(s):  
North Sea ◽  
Wadden Sea ◽  
Coastal Areas

scholarly journals Inventory and comparison of abundance of parasitic copepods on fish hosts in the western Wadden Sea (North Sea) between 1968 and 2010

2013 ◽  
Vol 94 (3) ◽  
pp. 547-555 ◽  
Author(s):  
Wouter Koch ◽  
Peter Boer ◽  
Johannes IJ. Witte ◽  
Henk W. Van der Veer ◽  
David W. Thieltges
Keyword(s):  
North Sea ◽  
Wadden Sea ◽  
Temporal Stability ◽  
Parasite Fauna ◽  
Fixed Number ◽  
Fish Host ◽  
Host Size ◽  
Negative Effects ◽  
Parasitic Copepods ◽  
Fish Hosts

A conspicuous part of the parasite fauna of marine fish are ectoparasites, which attach mainly to the fins or gills. The abundant copepods have received much interest due to their negative effects on hosts. However, for many localities the copepod fauna of fish is still poorly known, and we know little about their temporal stability as long-term observations are largely absent. Our study provides the first inventory of ectoparasitic copepods on fish from the western Wadden Sea (North Sea) based on field data from 1968 and 2010 and additional unpublished notes. In total, 47 copepod parasite species have been recorded on 52 fish host species to date. For two copepod species parasitizing the European flounder (Platichthys flesus), a quantitative comparison of infection levels between 1968 and 2010 was possible. Whereas Acanthochondria cornuta did not show a change in the relationship between host size and infection levels, Lepeophtheirus pectoralis shifted towards the infection of smaller hosts, with higher infection levels in 2010 compared to 1968. These differences probably reflect the biology of the species and the observed decrease in abundance and size of flounders during the last decades. The skin-infecting L. pectoralis can probably compensate for dwindling host abundance by infecting smaller fish and increasing its abundance per given host size. In contrast, the gill cavity inhabiting A. cornuta probably faces a spatial constraint (fixed number of gill arches), thus limiting its abundance and setting a minimum for the host size necessary for infections.

scholarly journals Living and dead foraminiferal assemblage from the supratidal sand Japsand, North Frisian Wadden Sea: distributional patterns and controlling factors

2021 ◽  
Vol 75 (1) ◽  
Author(s):  
Sarina Schmidt ◽  
Joachim Schönfeld
Keyword(s):  
North Sea ◽  
Wadden Sea ◽  
Distribution Patterns ◽  
Abundant Species ◽  
Foraminiferal Assemblage ◽  
The North ◽  
Key Species ◽  
Reproduction Season ◽  
The Dead ◽  
Reproductive Cycles

AbstractSupratidal sands are vitally important for coastal defence in the German Wadden Sea. They are less affected by human activities than other areas as they are located far off the mainland shore, touristical and commercial activities are generally prohibited. Therefore, supratidal sands are of high ecological interest. Nevertheless, the faunal inventory and distribution pattern of microorganisms on these sands were studied very little. The composition of living and dead foraminiferal assemblages was therefore investigated along a transect from the supratidal sand Japsand up to Hallig Hooge. Both assemblages were dominated by calcareous foraminifera of which Ammonia batava was the most abundant species. Elphidium selseyense and Elphidium williamsoni were also common in the living assemblage, but Elphidium williamsoni was comparably rare in the dead assemblage. The high proportions of Ammonia batava and Elphidium selseyense in the living assemblage arose from the reproduction season that differed between species. While Ammonia batava and Elphidium selseyense just finished their reproductive cycles, Elphidium williamsoni was just about to start. This was also confirmed by the size distribution patterns of the different species. The dead assemblage revealed 20 species that were not found in the living assemblage of which some were reworked from older sediments (e.g., Bucella frigida) and some were transported via tidal currents from other areas in the North Sea (e.g., Jadammina macrescens). The living foraminiferal faunas depicted close linkages between the open North Sea and the mainland. Key species revealing exchange between distant populations were Haynesina germanica, Ammonia batava and different Elphidium species. All these species share an opportunistic behaviour and are able to inhabit a variety of different environments; hence, they well may cope with changing environmental conditions. The benthic foraminiferal association from Japsand revealed that transport mechanisms via tides and currents play a major ecological role and strongly influence the faunal composition at this site.

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