Time variability of acoustic backscatter from zooplankton in the Ibiza Channel (western Mediterranean)

Pinot, Jean-Michel; Jansa, Javier

doi:10.1016/s0967-0637(00)00095-9

Cited by 64 publications

(63 citation statements)

References 17 publications

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“…However, animals with body sizes less than the wavelength by an order of magnitude can create strong backscatter signals too, if they are numerous enough to dominate the zooplankton assemblage as often reported from copepods, which represent the mm-size class (e.g. Pinot and Jansá 2001). The backscatter strength of objects is also strongly influenced by their acoustic properties, in particular by their sound speed contrast to the environment, which depends mainly on their material composition.…”

Section: Relationship Between Zooplankton and Acoustic Backscattermentioning

confidence: 99%

“…Since the pioneering work of Flagg and Smith (1989), many investigators have utilized the echo intensity measured by acoustic Doppler current profilers (ADCPs) to examine the temporal and spatial variability in the distribution of zooplankton biomass and diel vertical migration for over two decades, presuming that zooplankton are the main scatterers of sound in the typically used frequency range of 10s to 100s kHz (e.g., Heywood et al, 1991;Fischer and Visbeck, 1993;Flagg et al, 1994;Heywood, 1996;Ashjian et al, 1998;Luo et al, 2000;Pinot and Jansá, 2001;le -el e al., 2002;Jiang et al, 2007;Cisewski et al, 2010;Radenac et al, 2010;Wallace et al, 2010). ADCPs can complement conventional net sampling in an excellent way because they can be deployed in extreme environments and can operate autonomously year-round, and thus provide sufficient spatial and temporal resolution to yield precise estimates of timing, velocity and extent of DVM.…”

Section: Introductionmentioning

confidence: 99%

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Acoustic insights into the zooplankton dynamics of the eastern Weddell Sea

Cisewski

Strass

2016

Progress in Oceanography

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The success of any efforts to determine the effects of climate change on marine ecosystems depends on understanding in the first instance the natural variations, which contemporarily occur on the interannual and shorter time scales. Here we present results on the environmental controls of zooplankton distribution patterns and behaviour in the eastern Weddell Sea, Southern Ocean. Zooplankton abundance and vertical migration are derived from the mean volume backscattering strength (MVBS) and the vertical velocity measured by moored acoustic Doppler current profilers (ADCPs), which were deployed simultaneously at 64°S, 66.5°S and 69°S along the Greenwich Meridian from February, 2005, until March, 2008 While these time series span a period of full three years they resolve hourly changes.A highly persistent behavioural pattern found at all three mooring locations is the synchronous diel vertical migration (DVM) of two distinct groups of zooplankton that migrate between a deep residence depth during daytime and a shallow depth during nighttime. The DVM was closely coupled to the astronomical daylight cycles. However, while the DVM was symmetric around local noon, the annual modulation of the DVM was clearly asymmetric around winter solstice or summer solstice, respectively, at all three mooring sites. DVM at our observation sites persisted throughout winter, even at the highest latitude exposed to the polar night. Since the magnitude as well as the relative rate of change of illumination is minimal at this time, we propose that the ultimate causes of DVM separated from the light-mediated proximal cue that coordinates it. In all three years, a marked change in the migration behaviour occurred in late spring (late October/early November), when DVM ceased. The complete suspension of DVM after early November is possibly caused by the combination of two factors: (1) increased availability of food in the surface mixed layer provided by the phytoplankton spring bloom, and (2) vanishing diurnal enhancement of the threat from visually oriented predators when the illumination is quasi-continuous during the polar and subpolar summer. 3Zooplankton abundance in the water column, estimated as the mean MVBS in the depth range 50 -300 m, was highest end of summer and lowest mid to end winter on the average annual cycle. However, zooplankton abundance varied several-fold between years and between locations. Based on satellite and in situ data of chlorophyll and sea ice as well as on hydrographic measurements, the interannual and spatial variations of zooplankton mean abundance can be explained by differences in the magnitude of the phytoplankton spring bloom, which develops during the seasonal sea ice retreat. Whereas the vernal ice melt appears necessary to stimulate the blooming of phytoplankton, it is not the determinator of the blooms magnitude, its areal extent and duration. A possible explanation for the limitation of the phytoplankton bloom in some years is top-down control. We hypothesize that the phytoplankton spring ...

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Section: Relationship Between Zooplankton and Acoustic Backscattermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Acoustic insights into the zooplankton dynamics of the eastern Weddell Sea

Cisewski

Strass

2016

Progress in Oceanography

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“…The correlation between ADCP acoustic signal and zooplankton abundance is well known [Flagg and Smith, 1989]. Pinot and Jansá [2001] used data from an ADCP in the nearby Ibiza Channel to identify zooplankton diel migration, ascending at dusk and descending at dawn. The sharper peaks at dusk agree with the zooplankton ascension, although few peaks also were observed at dawn.…”

Section: Role Of Itwsmentioning

confidence: 99%

Evidence of sediment resuspension by island trapped waves

Jordi

Basterretxea

Wang

2009

Geophysical Research Letters

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Six months of current and acoustic backscatter data from an acoustic Doppler current profiler (ADCP) moored in the shelf off Mallorca (Balearic Islands, Mediterranean Sea) were analyzed. The presence of island trapped waves (ITWs) was determined by correspondence of energetic subinertial peaks in the alongshore current spectra with theoretical wave modes. Although currents in this area averaged 0.06 m/s and rarely exceeded 0.5 m/s, an intense episode with currents larger than 1 m/s was observed between March 8 and 11, 2007. Our analysis demonstrates that ITWs generated by local wind forcing were responsible for such currents, causing significant sediment resuspension on those days. It is suggested that even moderate wind pulses can induce important resuspension along the shelf by generating ITWs. This could be an overlooked mechanism of coupling between atmospheric and shelf circulation with significant implications for sediment dynamics and biogeochemical cycles.

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“…In the NW Mediterranean, organismal behaviour and physical heterogeneity are important as variability sources, specifically for zooplankton (Pinot and Jansá 2001). A sub-surface maximum of phytoplankton productivity and biomass occurs most of the year (Estrada 1985) and is especially strong during the summer stratification period.…”

Section: Introductionmentioning

confidence: 99%

Variability of mesozooplankton biomass and individual size in <em>a</em> coast-offshore transect in the Catalan Sea: relationships with chlorophyll <em>a</em> and hydrographic features

et al. 2016

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Summary:The temporal and spatial changes of zooplankton and chlorophyll a concentration were studied during the warm stratification period (early June) at three stations whose traits corresponded to the coastal, frontal, and offshore-dome water conditions described for the Catalan Sea. We sampled the stations for 12 days at a frequency ranging from less than 10 to 10 2 h, with a spatial resolution ranging from 10 to 10 4 m. The objective was to determine the variability of mesozooplankton and phytoplankton (chlorophyll a) biomass, and average individual size (mass) across a coast-offshore transect in relation to the stratification conditions prevailing in the NW Mediterranean during summer. The vertical distribution of phytoplankton biomass displayed a clear deep maximum at 60 m depth except at the coastal station. This maximum exists during most of the year and is especially important during the density stratification period. It was accompanied during daylight hours by a coherent zooplankton maximum. At sunset mesozooplankton ascended and dispersed, with larger organisms from deeper layers joining the migrating community and increasing the average individual mass. The highest variability of mesozooplankton biomass, individual mass and chlorophyll a concentration occurred at the front station due to the coupling between the vertical migration of zooplankton and the particular characteristics of the front. According to the data shown, the highest variability was observed at the lowest scales.Keywords: zooplankton biomass; NW Mediterranean; spatial distribution; short-term variability.Variabilidad de la biomasa del zooplankton y de su tamaño individual en un transecto costa-alta mar en el ar Catalán: relaciones con la clorofila a y las estructuras hidrográficas Resumen: Durante el periodo de estratificación térmica (principios de junio) se estudiaron los cambios temporales y espaciales de concentración de zooplancton y clorofila a en tres estaciones cuyos rasgos corresponden a las condiciones de aguas costeras, frontal y domo central descritas para el Mar Catalán. Muestreamos las estaciones a lo largo de 12 días con una frecuencia que varió entre <10 h y 10 2 h, y con una resolución espacial entre 10 y 10 4 m. El objetivo fue determinar la variabilidad de la biomasa del fitoplancton (clorofila a) y del mesozooplancton, así como de su tamaño individual promedio a lo largo de un transecto costa-mar abierto en relación con las condiciones de estratificación térmica típicas del Mediterráneo del Noroccidental desde finales de primavera a finales de verano. La distribución vertical de la biomasa de fitoplancton mostró la existencia de un máximo profundo a 60 m de profundidad, excepto en la estación costera. Aunque cierta heterogeneidad vertical en la biomasa de fitoplancton suele observarse durante la mayor parte del año, es especialmente importante durante el período de estratificación de densidad. El máximo de fitoplancton estuvo acompañado durante las horas de luz por un máximo de zooplancton, que en la crepúsculo as...

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Time variability of acoustic backscatter from zooplankton in the Ibiza Channel (western Mediterranean)

Cited by 64 publications

References 17 publications

Acoustic insights into the zooplankton dynamics of the eastern Weddell Sea

Acoustic insights into the zooplankton dynamics of the eastern Weddell Sea

Evidence of sediment resuspension by island trapped waves

Variability of mesozooplankton biomass and individual size in <em>a</em> coast-offshore transect in the Catalan Sea: relationships with chlorophyll <em>a</em> and hydrographic features

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