Sources of zooplankton on the Nova Scotia shelf and their aggregations within deep-shelf basins

Herman, Alex W.; Sameoto, D. D.; Shunnian, Chen; Mitchell, Michel R.; Petrie, Brian; Cochrane, N. A.

doi:10.1016/0278-4343(91)90066-f

Cited by 71 publications

(46 citation statements)

References 21 publications

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“…A similar pattern was found for C. paci$cus in Dabob Bay, a fjord in Washington (Osgood and Frost 1996). In addition, the deep Scotian Shelf basins accumulate high concentrations of latestage copepodids of C. jinmarchicus, Calanus hyperboreus, and Calanus glacialis (Sameoto and Herman 1990;Herman et al 1991).…”

supporting

confidence: 65%

“…Therefore, at the speed we profiled (1 m sp I), it provided data with a 0.5-m vertical resolution. Comparisons between OPC counts and net hauls have shown that the OPC provides very good estimates of copepod concentrations (Herman 1988(Herman , 1992. Coincident counts by the OPC are a potential problem at high zooplankton concentrations.…”

mentioning

confidence: 99%

“…Plankton nets were used to obtain the vertical distribution of C5 C. paci$cus while an optical plankton counter (OPC; Herman 1988Herman , 1992 was used to obtain the spatial extent of the deep C5 C. pacijkus aggregation. Net samples were obtained from discrete depth strata with a double, 1-m' MOCNESS (multiple opening and closing net and environmental sensing system; Wiebe et al 1976) equipped with 20 333-pm mesh nets.…”

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Observations of a deep aggregation of Calanus pacificus in the Santa Barbara Basin

Osgood

Checkley

1997

Limnology & Oceanography

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Abstract-An optical plankton counter/CTD package was used with zooplankton net samples to map the distribution of fifth copepodid (C5) CuZanus paci$cus in the Santa Barbara Basin region during two autumn cruises. Diapausing C5 C. puci$cus were aggregated in a layer just above the basin's oxygen-deficient bottom waters and below its sill depth. The maximal concentration measured was 6,900 ind. m -' from a net sample spanning a depth range double the thickness of the C5 layer. Although the C5 concentration varied, the layer was found at all stations of sufficient bottom depth within the basin. During November 1994, C5 C. pucijcus accounted for 95-97% of all zooplankton caught in net samples from the layer. Relatively low concentrations of deep-dwelling C5 C. pacificus were observed at nearby stations outside the basin. We hypothesize that C5 C. paci$cus descend into the Santa Barbara Basin at diapause, are trapped, and accumulate in a region of relatively low predator abundance. The resultant aggregation is estimated to contain a significant fraction of the regional C. pucijcus population and thus assumes an important role in its dynamics.Cdanus paciJcus, a marine planktonic copepod, is one of the dominant zooplankton species in the waters off southern California (Fleminger 1964;Star and Mullin 1981). In this region, C. pac@cus is active in the surface 100 m of the water column. However, starting in the late spring, some of the C. paci$cus arrest their development at the fifth copepodid (C5) stage and migrate to deeper waters (300-600 m) where they enter a diapause state (Fleminger 1985). A portion of the population remains dormant through the fall, becoming active again and rejoining the surface population around the first of the year.The Santa Barbara Basin (SBB), located off the coast of southern California, has an eastern sill of 225 m and a western sill extending as deep as 472 m in a narrow region (Fig. 1). Within it, Alldredge et al. (1984) observed a dense aggregation of diapausing C5 C. pacifkus from a submersible during early fall 1982. They estimated C5 concentrations up to 26 X lo6 ind. rnpi in a layer 20 m thick at a depth of 450 m, -100 m above the bottom. Although they had 10 dives over a 1.5&m diameter arc, the spatial extent of the aggregation as well as its concentration relative to nearby locations could not be ascertained. If the C5s within the basin are at concentrations much higher than elsewhere, they could be regionally important to the recruitment of C. paciJicus by serving as a potential seed population (e.g. Smith et al. 1986).To determine if Alldredge et al. (1984) had observed a recurring phenomenon, we sampled zooplankton in the SBB and surrounding waters during 20-22 November 1994 and 7-9 September 1995. Plankton nets were used to obtain the vertical distribution of C5 C. paci$cus while an optical plankton counter (OPC;Herman 1988Herman , 1992) was used to obtain the spatial extent of the deep C5 C. pacijkus aggregation. Net samples were obtained from discrete depth strata with a do...

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confidence: 99%

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Observations of a deep aggregation of Calanus pacificus in the Santa Barbara Basin

Osgood

Checkley

1997

Limnology & Oceanography

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“…The two-dimensional spatial ramifications of the pattern presented by Smith (1989, 1990) and especially its variability remain poorly quantified. On the Scotian Shelf, Herman et al (1991) show that by May in 1985 the spring bloom was over, surface concentrations were o1.0 mg m À3 , and a subsurface chlorophyll maximum at 40 m was well developed, persisting into October. In this region, the spring bloom typically occurs in late March (Perry et al, 1989) with interannual variability in both timing and magnitude controlled by hydrographically controlled differences in vertical stability.…”

Section: Introductionmentioning

confidence: 98%

Satellite-measured phytoplankton variability in the Gulf of Maine

Thomas

Townsend

Weatherbee

2003

Continental Shelf Research

108

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The first 4 years of SeaWiFS ocean color data (September 1997-August 2001 provide the first synoptic quantification of seasonal and interannual phytoplankton chlorophyll variability in the Gulf of Maine. Climatological monthly means show spatial patterns associated with the annual cycle. Concentrations are elevated throughout the year in coastal regions and over shallow banks (Georges Bank, Nantucket Shoals and Browns Bank) with a spring and fall bloom superimposed. Over deeper basins and the Scotia Shelf, a canonical North Atlantic seasonal cycle is present with low (o 1 mg m À3 ) winter (December-February) concentrations, an annual maximum in March-April (>2 mg m À3 ), reduced concentrations in summer and a fall bloom beginning as early as September in Jordan Basin but in OctoberNovember over other regions. Strong interannual variability over the 4-year time series shows the climatological seasonal features are often a biased picture of both timing and magnitude. The clearest interannual signal is of reduced chlorophyll concentrations throughout 1998, including weak spring and fall blooms. A connection between low concentrations in 1998 and local wind forcing is not evident. However, the low concentrations are coincident with negative anomalies in satellite surface temperature fields and follow the intrusion of relatively cold, low salinity slope water into the Northeast Channel which previous authors have argued is linked to changes in Labrador slope water transport induced by the North Atlantic Oscillation. Reduced concentrations in 1998 are consistent with both lower nitrate/nitrite concentrations in the intruding water as well as reduced subsurface stratification which would delay or reduce the onset of the spring bloom. r

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“…In the NW Atlantic, Meganyctiphanes norvegica is known to reproduce in the Gulf of St. Lawrence, in the Gulf of Maine and on the Scotian Shelf, although Herman et al (1991) concluded that Scotian Shelf plankton biomass production is enriched by transport from the St. Lawrence Gulf (see Bucklin et al 1997) (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Genetic differentiation and local temporal stability of population structure in the euphausiid Meganyctiphanes norvegica

Papetti¹,

Zane²,

Bortolotto³

et al. 2005

Mar. Ecol. Prog. Ser.

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Meganyctiphanes norvegica (M. Sars 1856), the northern krill, is the largest and most abundant euphausiid species in the northern hemisphere, where it represents a key component of many pelagic communities. Although planktonic, krill could be considered a nektonic organism, as it is capable of active movements. This behaviour may be adaptive, because it allows these organisms to maintain their geographic position, leading to stable population structure, despite being continuously exposed to the heterogeneous oceanic conditions. By means of single-strand conformation polymorphism and DNA sequencing, we analyzed allelic variation of the Subunit 1 of NADH dehydrogenase mtDNA locus in 23 populations of the northern krill Meganyctiphanes norvegica, from 15 locations spanning the distribution range of the species. Analysis of the data indicated that the genetic structure, as revealed by analysis of population samples collected at the same site in consecutive years, was stable during that sampling period. Our results revealed the existence of 4 genetically and geographically distinct gene pools of M. norvegica, 2 occurring in the NE Atlantic ('northern' NE Atlantic and 'southern' NE Atlantic), 1 in the NW Atlantic, and 1 in the Mediterranean (Ligurian) Sea.

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Sources of zooplankton on the Nova Scotia shelf and their aggregations within deep-shelf basins

Cited by 71 publications

References 21 publications

Observations of a deep aggregation of Calanus pacificus in the Santa Barbara Basin

Observations of a deep aggregation of Calanus pacificus in the Santa Barbara Basin

Satellite-measured phytoplankton variability in the Gulf of Maine

Genetic differentiation and local temporal stability of population structure in the euphausiid Meganyctiphanes norvegica

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