High-resolution observations of plankton spatial distributions correlated with hydrography in the Great South Channel, Georges Bank

During a cruise to Georges Bank in May 1992, the Video Plankton Recorder (VPR) was towyoed while non-invasively obtaining images of the plankton and environmental (CTD) data. Data from an 8 h transect across the Great South Channel (GSC) were analyzed on a continuum of spatial scales from coarse-scale (100 km) to micro-scale (mm). Abundance was determined for 12 taxonomic groups including: invertebrate larvae (ophiopluteus larvae, anthozoa larvae: Cerianthus sp.), hydroids, copepods (Calanus sp., Pseudocalanus sp.), pteropods (Limacina retroversa, Clione sp.), ctenophores (Mnemiopsis sp., Pleurobrachia sp.), larvacea (Oikopleura sp.), chaetognatha (Sagitta sp.), and diatom colonies (Chaetoceros socialis). Species-specific plots of the positions of individual plankton in the water column and plots of the temperature and salinity at which the plankton were observed (temperature-salinity-plankton plots) showed that major taxonomic groups were patchy at coarse scales because of their association with specific water masses of different origin and associated temperature/density discontinuities (pycnocline and fronts). Analysis of the T-S characteristics of water types indicated that diatom colonies and ophiopluteus larvae of echinoderms were transported to GSC in a band of cold water originating on the south flank of Georges Bank. Within this band, diatom colonies formed an intense patch at a front reaching a density of 5 ml−1. Within each water mass, fine-scale (10s of meters) plankton patchiness was associated with regions of vertical stability as indicated by the association of plankton with regions of high gradient Richardson number. Aggregation of plankton at the microscale (<1 m) occurred significantly only for plankton capable of active swimming, suggesting a dynamic interaction between biological and physical variables at this spatial scale. On occasion, veliger larvae of Limacina retroversa were found in spawning patches at concentrations exceeding 600 mk−1 within a few centimeters of the air-sea interface. The ability to observe and quantify local concentrations of plankton together with micro-scale physics, but over broad spatial scales, will help provide information on the coupling between spatial scales necessary to understand how individuals interact to form populations and communities in the world oceans.

[1]  A. C. Redfield.  THE HISTORY OF A POPULATION OF LIMACINA RETROVERSA DURING ITS DRIFT ACROSS THE GULF OF MAINE , 1939 .

[2]  Henry B. Bigelow,et al.  Physical Oceanography Of The Gulf Of Maine , 1927 .

[3]  N. Garfield,et al.  Physical origins of Georges Bank water , 1981 .

[4]  Changsheng Chen,et al.  Variability of currents in late spring in the northern Great South Channel , 1995 .

[5]  P. Wiebe,et al.  Tidally generated high-frequency internal wave packets and their effects on plankton in Massachusetts Bay , 1983 .

[6]  H. Bigelow.  Plankton Of The Offshore Waters Of The Gulf Of Maine , 1926 .

[7]  L. Haury.  A comparison of zooplankton patterns in the California Current and North Pacific Central Gyre , 1976 .

[8]  P. Wiebe,et al.  Patterns and Processes in the Time-Space Scales of Plankton Distributions , 1978 .

[9]  Peter Franks,et al.  Sink or swim: Accumulation of biomass at fronts , 1992 .

[10]  S. Gallager,et al.  Ontogenetic changes in the vertical distribution of giant scallop larvae, Placopecten magellanicus, in 9-m deep mesocosms as a function of light, food, and temperature stratification , 1996 .

[11]  A. Longhurst.  Analysis of Marine Ecosystems , 1981 .

[12]  M. D. Keller,et al.  Spring phytoplankton blooms in the absence of vertical water column stratification , 1992, Nature.

[13]  M. Sinclair.  Marine Populations: An Essay on Population Regulation and Speciation , 1988 .

[14]  C. Davis.  The Video Plankton Recorder (VPR) : Design and initial results , 1992 .

[15]  B. Butman,et al.  Long-Term Observations on the Southern Flank of Georges Bank. Part I: A Description of the Seasonal Cycle of Currents, Temperature, Stratification, and Wind Stress , 1987 .

[16]  R. Emlet.  LOCOMOTION, DRAG, AND THE RIGID SKELETON OF LARVAL ECHINODERMS , 1983 .

[17]  Changsheng Chen,et al.  Abundance, distribution and population structure of the copepod Calanus finmarchicus in a springtime right whale feeding area in the southwestern Gulf of Maine , 1995 .

[18]  Physical Processes and Zooplankton Distribution in the Great South Channel: Observational and Numerical Studies. , 1995 .

[19]  Scott M. Gallager,et al.  Differences in fine-scale structure and composition of zooplankton between mixed and stratified regions of Georges Bank , 1996 .

[20]  Marine Zooplankton Colloquium.  Future marine zooplankton research-a perspective , 1989 .

[21]  R. Campbell,et al.  Abundance, biomass, vertical migration and estimated development rate of the copepod Calanus finmarchicus in the southern Gulf of Maine during late spring , 1995 .

[22]  A. C. Hardy,et al.  Plankton Dynamics@@@The Plankton of the South Georgia Whaling Grounds and Adjacent Waters, 1926-27 , 1935 .

[23]  M. C. Macaulay,et al.  Copepod patches and right whales in the great south channel off new England , 1988 .

[24]  P. Mladenov,et al.  Development, settling behaviour, metamorphosis and pentacrinoid feeding and growth of the feather star Florometra serratissima , 1983 .

[25]  Thomas M. Powell,et al.  Effects of physical processes on planktonic ecosystems in the coastal ocean , 1984 .

[26]  A. C. Giese,et al.  Reproduction of marine invertebrates , 1974 .

[27]  C. Garrett,et al.  Tidal mixing versus thermal stratification in the Bay of Fundy and gulf of Maine , 1978 .

[28]  C. Davis,et al.  Micropatchiness, turbulence and recruitment in plankton , 1991 .

[29]  M. Tomczak.  CHAPTER 9 – Hydrology of the Pacific Ocean , 1994 .

[30]  Karl Banse,et al.  On the vertical distribution of Zooplankton in the sea , 1964 .

[31]  L. Mcedward.  Ecology of Marine Invertebrate Larvae , 1995 .

[32]  U. Riebesell.  The formation of large marine snow and its sustained residence in surface waters , 1992 .

[33]  E. Carpenter,et al.  Gulf stream cold core rings: large-scale interaction sites for open ocean plankton communities , 1976 .

[34]  Mark R. Abbott,et al.  Plankton patchiness: biology in the physical vernacular , 1985 .

[35]  A. Solow,et al.  Microaggregations of Oceanic Plankton Observed by Towed Video Microscopy , 1992, Science.

[36]  P. Wiebe.  SMALL-SCALE SPATIAL DISTRIBUTION IN OCEANIC ZOOPLANKTON† , 1970 .

[37]  N. Garfield,et al.  Gulf of Maine intermediate water , 1979 .

[38]  Kenneth L. Denman,et al.  Collection and Analysis of Underway Data and Related Physical Measurements , 1978 .

[39]  R. Limeburner,et al.  Variability of water properties in late spring in the northern Great South Channel , 1995 .

[40]  R. Beardsley,et al.  Springtime nutrient and chlorophyll a concentrations in the southwestern Gulf of Maine , 1995 .