a b s t r a c tNeustonic microplastic and zooplankton abundance was determined in the North Western Mediterranean Sea during a summer cruise between July 9th and August 6th 2010, with a break between July 22th and 25th due to a strong wind event. Ninety percent of the 40 stations contained microplastic particles (size 0.3-5 mm) of various compositions: e.g., filaments, polystyrene, thin plastic films. An average concentration of 0.116 particles/m 2 was observed. The highest abundances (>0.36 particles/m 2 ) were observed in shelf stations.The neustonic plastic particles concentrations were 5 times higher before than after the strong wind event which increased the mixing and the vertical repartition of plastic particles in the upper layers of the water column. The values rise in the same order of magnitude than in the North Pacific Gyre. The average ratio between microplastics and mesozooplankton weights was 0.5 for the whole survey and might induce a potential confusion for zooplankton feeders.
Using phytoplankton pigments as biomarkers, we investigated the relationship between the physical forcing and the resulting biological, ecological and biogeochemical properties of the geostrophic front of the Eastern Alboran Sea. (1) Typical frontal sites present biomass levels averaging 60 mg chl a mm2 (up to 100 mg mm2), whereas the adjacent zones (typical Atlantic and Mediterranean) are characterized by an average integrated chlorophyll biomass of 20 mg chl a rnm2. (2) The phytoplankton biomass at front is diatom-dominated and differs markedly from the adjacent zones (typical Atlantic and Mediterranean), flagellate-and cyanobacteriadominated.Therefore, high biomasses at the front do not result from purely physical accumulation but rather from local production.(3) The chlorophyll and diatom biomasses increase from the left to the right side of the Atlantic jet, which supports the hypothesis of a cross-frontal secondary circulation allowing a diatom bloom development. (4) Using assumptions on the carbon/chlorophyll ratio and growth rates for the different phytoplankton taxa, we evaluated the specific productions: diatoms account for 67% of the production at front and only about 10% at adjacent zones. (5) High concentrations of phaeopigments are only found at frontal stations, which points out the pecularities of the food web at the frontal site, compared to adjacent areas. (6) The observations made during this study give a precise picture of that frontal system: autotrophic new production and exportation are enhanced. The implication of this fro&l system on the carbon budget at a regional scale may be important.
The annual variation in neustonic plastic particles and zooplankton was studied in the Bay of Calvi (Corsica) between 30 August 2011 and 7 August 2012. Plastic particles were classified into three size classes, small microplastics (0.2-2mm), large microplastics (2-5mm) and mesoplastics (5-10mm). 74% of the 38 samples contained plastic particles of varying composition: e.g. filaments, polystyrene, thin plastic films. An average concentration of 6.2 particles/100 m(2) was observed. The highest abundance values (69 particles/100 m(2)) observed occurred during periods of low offshore wind conditions. These values rose in the same order of magnitude as in previous studies in the North Western Mediterranean. The relationships between the abundance values of the size classes between zooplankton and plastic particles were then examined. The ratio for the intermediate size class (2-5mm) reached 2.73. This would suggest a potential confusion for predators regarding planktonic prey of this size class.
A long-term time series of plankton records collected by the continuous plankton recorder (CPR) Survey in the northeast Atlantic indicates an increased occurrence of Cnidaria since 2002. In the years 2007 and 2008, outbreaks of the warm-temperate scyphomedusa, Pelagia noctiluca, appeared in CPR samples between 45° N to 58° N and 1° W to 26° W. Knowing the biology of this species and its occurrence in the adjacent Mediterranean Sea, we suggest that P. noctiluca may be exploiting recent hydroclimatic changes in the northeast Atlantic to increase its extent and intensity of outbreaks. In pelagic ecosystems, Cnidaria can affect fish recruitment negatively. Since P. noctiluca is a highly venomous species, outbreaks can also be detrimental to aquaculture and make bathing waters unusable, thus having profound ecological and socio-economic consequences.
The spatial and temporal distributions of phytoplankton pigments were investigated in the western and south central Ross Sea during austral spring 1994 and summer 1990. Large gradients in biomass and phytoplankton community composition were observed both in the east-west and south-north directions, in relation to differences in water column structure and stability, which themselves depend on the processes of ice retreat within the different areas. Important are melting in the western Ross Sea, which induces strong stratification, and ice breakup and wind stress in the south central Ross Sea, which Ž . result in deep mixing and weakly stratified waters. In the western Ross Sea, the highest chlorophyll a chl. a concentrations Ž upper 100 m . In the diatom bloom area, high levels of phaeophorbides a maximum value of 192 mg m in the upper 100 . w m indicated that the dominant grazers, identified as Limacina helecina and copepods Hecq, J.H., Magazzu, G., Goffart, A., Catalano, G., Vanucci, S., Guglielmo, L., 1992. Distribution of planktonic components related to vertical structure of water masses in the Ross Sea and the Pacific sector of the Southern Ocean. In: Anonymous, Atti del 98 congresso A.I.O.L., Santa x Margherita Ligure, 20-23 Novembre 1990, 665-678 , transferred a sustained part of the diatom production to the herbivore trophic level. Synthesis of our data with published information suggests that the diatom bloom we observed in the western Ross Sea was dominated by the species Fragilariopsis curta, and occurs annually off the coast of Victoria Land from 72830 X S to 778S within 100-250 km from the coastal ice edge. It is assumed to persist on the order of 2.5-3 months during summer. In the south central Ross Sea, which was characterized by a poorly or unstratified water column, moderate chl. a Ž . mg fucoxanthin m in the upper 100 m overlapped with the Phaeocystis bloom in the slightly stratified marginal ice zone. This was an area of increased grazing pressure by various types of herbivorous zooplankton, among which very large amounts of krill were observed. q
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