We present measurements of bulk properties of the matter produced in Au+Au collisions at √ sNN = 7.7, 11.5, 19.6, 27, and 39 GeV using identified hadrons (π ± , K ± , p andp) from the STAR experiment in the Beam Energy Scan (BES) Program at the Relativistic Heavy Ion Collider (RHIC). Midrapidity (|y| <0.1) results for multiplicity densities dN/dy, average transverse momenta pT and particle ratios are presented. The chemical and kinetic freeze-out dynamics at these energies are discussed and presented as a function of collision centrality and energy. These results constitute the systematic measurements of bulk properties of matter formed in heavy-ion collisions over a broad range of energy (or baryon chemical potential) at RHIC.

A laboratory study ~n v e s t~g a t e d cell ingestion, absorption of organlc matter, and paralytic shellfish poisoning (PSP) toxin ~ncorporation by iclytilus eduljs exposed to a high-tox~city isolate of the red tide dinoflagellate Alexandrium fundyense (strain GtCA29, toxicity = 66 pg saxltoxin equivalents (STXeq) cell-'). Maximum ingestion rate was achieved at 150 to 250 cells ml-' Clearance rates on A. fundyense were about 48'1.;) lower than those for a non-toxic control diet of the diatom Thalassioslra weissflogii. Mussels with no prior h~story of exposure to PSP maintained a constant ingest~on rate over 17 d of exposure to a A. fundyense (at 256 cells ml-l), and absorbed ca 6 2 % of the organic matter ingested. They experienced no mortality or sublethal adverse effects during intoxication. Maximum (saturation) toxin levels of 4.5 X 10"ig STXeq 100g-' were attained after 12 to 13 d. a value comparable to maximum toxicities reported during major toxic bloom events. Mussels could exceed the quarantine toxin level (80 pg STXeq 100g-l) in < 1 h of exposure to high densities of this isolate. At saturation, they incorporated 79 O/o of the toxin ingested, primarily in the viscera. This provides the first estimate of toxin incorporation efficiency in a bivalve under steady state conditions. Dinoflagellate toxins, determined by HPLC, were dominated by carbamate derivatives. The muscle, mantle/gill and foot of M. edulis showed significant enrichment in STX and reduction in the gonyautoxins GTX2+3 and neoSTX relative to ingested cells. The toxin composition of the viscera more closely resembled that of ingested cells, reflecting the presence of numerous intact cells in gut contents. Through its potential use of A. fundyense as a sole food source, M eduljs is thus capable of remarkably efficient toxln accumulation at environmentally realistic dinoflagellate cell densities.

Diel vertical migration patterns of the dinoflagellates Gonyaulax tamarensis and Heterocapsa triquetra were monitored in an estuarine embayment subject to localized blooms of both species. A concurrent study of tidal flushing using a dye tracer demonstrated an efficient, densitydriven mixing process that exchanged water within the embayment at a rate of approximately 0.5 d-'. Loss rates of the whole pond populations of G. tamarensis and H. trjquetra cells were smaller, ranging between 0.02 and 0.13 d-'. The cells were thus able to maintain a non-mixed distribution even under weakly stratified conditions. This selective retention of the 2 species relative to water exchange was due to the differential advection of surface and bottom waters through the inlet channel and the general avoidance of high irradiance surface layers by the dinoflagellates. Both species migrated to irradiances equivalent to 30% of summer sunlight when nutrients were presumably non-limiting, resulting in subsurface aggregations 1 to 2 m deep. Under nutrient-limited conditions, G. tamarensjsmigration was restricted to irradiance at or below 10 to 15% summer sunlight. Planozygotes (a life-cycle stage preceding cyst formation) migrated in a manner indistinguishable from the remainder of the nutrientlimited G. tamarensis population. The results help to explain the dominance of dinoflagellates in such embayments, the localization of their blooms, and the distribution of their resting cysts in the region.

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Separate polyclonal antibodies were developed against cell surface antigens of the 2 forms of the pennate diatom Pseudonitzschia (previously known as N~tzschia) pungens, i.e. forma multiseries (the domoic-acid-producing form) and forma pungens (the nontoxic form). Positive antigenic reactions were visualized with epifluorescence microscopy, using a fluorescein isothiocyanate (FITC) indirect immunofluorescence assay. The assay successfully distmguished 31 clones of f . multiseries from the l ? clones of f. pungens tested, with no cross reactions of the antisera between the 2 forms. The antisera were active against P, pungens cells isolated from Prince Edward Island and Nova Scotia, Canada, and Massachusetts, Rhode Island, Texas and Washington. USA. Of the 27 other clones tested from the genera Pseudonitzschia and Nitzschia, 2 other domoic-acid-producing species (P. australis and P. pseudodelicatissima) and 2 nontoxic species (P. subcurvata and P. fraudulenta) showed a slight positive response to the antisera, as did the domoic-acid-producing pennate diatom Amphora coffaeiformis. These reactions are not great enough to cause concern about misidentification, but pose questions about phylogenic relationships. Other representatives from the class Bacillariophyceae and from 8 other major classes of phytoplankton did not cross react with the antisera. Excellent labelling was obtained with live cells and those frozen at -6OoC, or preserved in 2 % glutaraldehydeparaformaldehyde, 2 % borate-buffered formalin or 2 % paraformaldehyde. Immunofluorescence shows great promise as a technique to distinguish between the 2 forms of P. pungens for research and monitoring purposes.