Daro, M.H.

Open Marine Archive

764 BULLETINOFMARINESCIENCE,VOL.37, NO.2, 1985
shellfish poisoning have generally been inconclusive and until recently the toxicity of G. aureolum
has been considered doubtful. Expl:riments with cultured G. aureolum and young trout have confirmed
the toxicity of this denoflagellate. The effects of the toxin are discussed and the relevance, in this case,
ofPSP toxin tests is questioned, It is suggested that G, aureolum might have toxic and nontoxic phases
and that the occurrence of these depends on environmental conditions. It is hoped to discuss results
of recent experiments concerned with this hypothesis.-Scottish Marine Biological Association, Oban,
Argyll, Scotland PA34 4AD.
FIELDSTUDYOF SELECTIVITY,EFFlCIENCYANDDAILYVARIATIONIN THEFEEDINGOF THEMARINE
COPEPODTEMORALONG/CORN/S,INTHESOUTHERNBIGHTOFTHENORTHSEAby M, H. Daro, - Temora
longicornis is the dominant species among the zooplankton during the phytoplankton bloom being
dominated by Phaeocystis pouchetti, Shipboard grazing experiments carried out before, during and
after the bloom showed that Temora feeds very inefficiently on Phaeocystis, as far as the late copepodites
and the adults are concerned. Ivlev Parsons feeding relationships on different size classes of phyto-
plankton are given for all developmental stages. When diatoms blooming (at the beginning of April,
before the Phaeocystic bloom) or, when the Phaeocystic develops, and after the bloom when only
small flagellates are present, different relations for the same stage were found. This inefficient feeding
occurs when Phaeocystis develops its mucous envelope at the top and in the declining phase of the
bloom: colonies ofa few mm to a few cm diameter-the top of the bloom can represent 20-30 mg
chlorophyll aim' and daily ingestions of late copepodites and adults represent only 15-20% of their
own weight. Together with the low ingestion rates, day-night feeding rhythms disappear. Discussion
is given about the consequence of 24 hours activity (instead of a few hours nightly at high rates) on
the energy budget of the animals whose production is declining, this phenomenon is paralleled by
increasing temperature on a shallow water column (higher oxygen demand and metabolic rates).
Possible surviving mechanisms are discussed (lipid reserves, resistant egg production, switching to
other food diet).-Free University Brussels, Laboratory Ecology, Pleinlaan 2, B-1050 Brussels, Belgium.
IN SITUOBSERVATIONSONSURFACESWARMINGEUPHAUS/APAC/FlCAINSENDAIBAYINEARLYSPRING
WITHSPECIALREFERENCETOTHEIRBIOLOGICALCHARACTERISTICSby Y. Endo, Y. Hanamura and A.
Taniguchi. - When underwater observations on a surface swarm of a euphausiid, Euphausia paci./i£a,
were made, swarming individuals were collected by a hand net to provide detailed information on
their biological characteristics. No fish predators were found near the swarm. Euphausiids do not seem
to come to the surface to feed, because the stomach fullness is low and their probable food is not
plentiful at the surface layer. Forty-six percent of the stomachs contained crystalline cones of euphausiid
eyes and 90% contained crustacean spines, perhaps of thoracic legs of euphausiids. While all the males
were in breeding condition, we found no female attached spermatophores. This indicates that mating
would occur later in the swarming season.-(A. T.) Laboratory of Oceanography, Faculty of Agriculture,
Tohoku University, Sendai 980, Japan.
SPECTRALQUALITYANDQUANTITYEFFECTSONTHEPRIMARYPRODUCTIVITYOFPHYTOPLANKTONby
M. A. Faust. - Photosynthetic-irradiance response of phytoplankton in sunlight, blue-green and orange-
red lights were measured in the Atlantic Barrier Reef Ecosystem at Carry Bow Caye, Belize. The blue-
green (400-500 nm) and orange-red (550-700 nm) radiation was obtained by using Roscolene plastic
filters. Photosynthetic pigment composition and cell densities of algal assemblages were determined.
Dominant phytoplankton were diatoms, cyanobacteria and dinoflagellates, their proportion varied
with the site examined, Blue-green and orange-red light in addition to sunlight was effectively utilized
by phytoplankton. These results demonstrate that phytoplankton assemblages can effectively absorb
in situ radiation over a wide spectral region of the visible spectrum. The ecological significance of
light quality and accessory pigments on aquatic primary production will be discussed.-Smithsonian
Environmental Research Center, Edgewater, Maryland 21037.
SUBSURFACECHLOROPHYLLMAXL\fAINTHEWESTERNPACIFICOCEANby K. Furuya and T. Nemoto.-
Phytoplankton carbon abundance, population structure in terms of size distribution and taxonomic
composition, and their growth rates at layers of subsurface chlorophyll maxima (SCM) were inves-
tigated and compared with those in the upper layers in the western Pacific Ocean from 1979 to 1982.
SCM were primarily due to an accumulation of cells rather than increase in cellular chlorophyll. SCM
were characterized by a dominance of cells smaller than 8 ILmin terms of phytoplankton carbon. This
fraction was composed of non-preservable flagellates and monads, i.e., fragile forms. Among the fragile
forms, Micromonas, Ochromonas, Gymnodinium and green coccoid forms were dominant. There was
no distinct difference in size distribution and taxonomic composition within major taxonomic groups
between SCM and the surface layer, though a marked difference existed in species and generic assem-
blages. Simulated in situ incubation of diluted natural seawater resulted in higher growth rates at SCM
than at 10m depth. Transmission electron micrographs of cells at SCM showed more densely stacked


Field study of selectivity, efficiency and daily variation in the feeding of the marine copepod <i>Temora longicornis</i>, in the southern bight of the North Sea

Field study of selectivity, efficiency and daily variation in the feeding of the marine copepod <i>Temora longicornis</i>, in the southern bight of the North Sea

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