Life cycle and distribution of Calanus finmarchicus in deep basins on the Nova Scotia shelf and seasonal changes in Calanus spp.

Sameoto, D. D.; Herman, AW

doi:10.3354/meps066225

Cited by 79 publications

(41 citation statements)

References 10 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: 67%

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: 67%

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

Osgood

Checkley

1997

Limnology & Oceanography

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“…Since the data already indicate population centers over the basins, these are potentially very important. Sameoto & Herman (1990) and Herman et al (1991) found this to be the case in the deep basins on the Scotian Shelf; it is reasonable to anticipate the same in the Gulf of Maine. We imagine, therefore, deep unexplored reservoirs of diapausing copepodites within the 200 m isobaths.…”

Section: Mmentioning

confidence: 71%

Biological/physical simulations of Calanus finmarchicus population dynamics in the Gulf of Maine

Lynch¹,

Gentleman²,

McGillicuddy³

et al. 1998

Mar. Ecol. Prog. Ser.

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A site-specific, coupled biologicaVphysica1 model is described for the dominant winterspring copepod in the Gulf of Maine. The biological portion describes temperature-and fooddependent progression through 13 life stages in an Eulerian (concentration-based) framework. The population is transported in a flow field depicting the climatological mean conditions in 2 mo 'seasons'. Behavioural assumptions account for depth selection and 2 limiting cases are contrasted: dispersal throughout the water colun~n, and aggregation in the surface layer. Simulations are inspired by MARMAP observat~ons, with an emphasis on the mid-winter initiation of the annual bloom by diapausing populations, and their role in supplying reproducing populations to Georges Bank during spring. Passive tracer sirnulations illustrate the role of the circulation. Georges Bank itself is an open system and depends on resupply from external sources. A l l 3 deep basins of the Gulf are capable of contributing populations to the Bank. The Scotian Shelf is capable of populating the Southern Flank. In the case where the organisms aggregate in the surface layer, the effect of convergence in downwelling zones is shown to be a significant contributor to population &stribution. Baseline population dynamics are initiated on January 1 by activating a diapausing population (Go) based on 10 yr mean abundance and distribution from the MARMAP program. The abundance and distribution of Go adults is reproduced with a 3-layer model, spatially vanable mortality, an extended period of activation, no food limitation, and a large, heretofore unobserved source of diapausing C5s near-bottom. Reproduction modeled in this system shows significant development of generation 1 (G,) over the Gulf of Maine in February-March, which is not observed. Delay of reproduction over the Gulf, and/or severe early-stage mortality, is required to conform with the data. The space-time pattern of this effect is consistent with the observed chlorophyll distribution and hming, and reasonable food-limitation thresholds. Inclusion of this effect initiates the spring Calanus bloom in the correct space-time pattern, with significant cohorts of Go females and G, nauplii over important cod and haddock spawning grounds on Georges Bank. The implication is that G, is locally spawned in food-rich waters over Georges Bank by females advected in the food-poor Gulf of Maine surface layer.

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“…This is the same mechanism proposed for the high concentrations of deep-dwelling stages of Calanus spp. in basins on the Nova Scotia shelf (Sameoto & Herman 1990). Advection of organisms to a n area combined with a concentrating mechanism is also the explanation Wishner et What happens to the deep aggregation?…”

Section: How Does the Deep Aggregation Build Up?mentioning

confidence: 99%

Seasonal variations in a deep aggregation of Calanus pacificus in the Santa Barbara Basin

Ke¹,

Checkley²

1997

Mar. Ecol. Prog. Ser.

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A deep aggregation of fifth copepodid (C5) Calanuspacificus in the Santa Barbara Basln (SBB) was mapped over yr w~t h zooplankton net tows, a n optical plankton counter, and a moored acoushc Doppler current profller Hlgh concentrations of diapausing C5 C pacificus bullt up in the deep waters of the SBB dunng the summer and into the fall Dunng the buddup the deep aggregation moved up from the bottom as oxygen became depleted In the basin S deep waters The deep aggregatlon apparently bullds u p due to the basin trapping C5s that migrate below the sill depth from water advected over the basin C5s are retalned within the basln until they swim or are forced above the sill depth Possible mechanisms responsible for the dispersal of the deep aggregation are mlgratlon to the surface waters with subsequent dispersal by surface currents advection over the basin s sill due to the buildup of oxygen-deficient water or flushing of the basin's deep water

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Life cycle and distribution of Calanus finmarchicus in deep basins on the Nova Scotia shelf and seasonal changes in Calanus spp.

Cited by 79 publications

References 10 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

Biological/physical simulations of Calanus finmarchicus population dynamics in the Gulf of Maine

Seasonal variations in a deep aggregation of Calanus pacificus in the Santa Barbara Basin

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