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The plume advection hypothesis links blooms of the toxic dinoflagellate Alexandrium fundyense in the western Gulf of Maine (GOM) to a buoyant plume derived from river outflows. This hypothesis was examined with cruise and moored-instrument observations in 1993 when levels of paralytic shellfish poisoning (PSP) toxins were high, and in 1994 when toxicity was low. A coupled physical-biological model simulated hydrography and A. fundyense distributions. Initial A. fundyense populations were restricted to low-salinity nearshore waters near Casco Bay, but also occurred in higher salinity waters along the plume boundary. This suggests two sources of cells-those from shallow-water cyst populations and those transported to shore from offshore blooms in the eastern segment of the Maine coastal current (EMCC). Observations confirm the role of the plume in A. fundyense transport and growth. Downwelling-favorable winds in 1993 transported the plume and its cells rapidly alongshore, enhancing toxicity and propagating PSP to the south. In 1994, sustained upwelling moved the plume offshore, resulting in low toxicity in intertidal shellfish. A. fundyense blooms were likely nutrient limited, leading to low growth rates and moderate cell abundances. These observations and mechanisms were reproduced by coupled physical-biological model simulations. The plume advection hypothesis provides a viable explanation for outbreaks of PSP in the western GOM, but should be refined to include two sources for cells that populate the plume and two major pathways for transport: one within the low-salinity plume and another where A. fundyense cells originating in the EMCC are transported along the outer boundary of the plume front with the western segment of the Maine coastal current.Toxic dinoflagellate blooms are a serious economic and

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Particles in suspension in fresh, sea, and estuarine waters appear uniquitously to exhibit a small range of negative surface charge, as measured by electrophoresis. This uniformity is often attributed to the presence of organic or oxide surface coatings on the particles. Here we present experimental results which lend direct support to the idea of control of the particle surface charge by organic coatings. Iron oxide particles formed in situ in organic‐free water exhibit the expected positive charge but, on immersion in water containing its natural organic material, rapidly acquire the negative charge normally found for field samples.

We report data for the Enewetak site of the SEAREX program from the rainy season in 1979. The concentrations of n-alkanes, n-alkanols, sterols, n-alkanoic acids and their salts, and total organic compounds in rain are reported, as well as the apparent gaseous hydrocarbon concentrations. These data and information on the particulate forms are analyzed in conjunction with ancillary chemical and meteorological data to draw inferences about sources, fluxes, and chemical speciations. While the higher molecular weight lipid biomarker components are exclusively terrestrial, the organic carbon in rain may be derived from atmospheric transformations of terrestrial carbon. Distinctively marine components are nearly absent. Comparison of the scavenging ratios of the organic components in rain vs. those for clays reveals that the alkanoic acids and the higher molecular weight alkanols behave as essentially particulate materials, whereas lower alkanols and most hydrocarbons show much higher scavenging ratios, probably due to the involvement of a gaseous phase or sampling artifact. Vaporization in the atmosphere and scavenging of a gas phase would lead to higher scavenging ratios; vaporization during sampling would give low aerosol concentrations and high gas-phase concentrations, leading to high scavenging ratios. The major fluxes at Enewetak result from rain rather than dry deposition, and extrapolating the measured values to meaningful annual averages requires adjustment for seasonally varying source intensity and rain dynamics. Aerosol data for other seasons and other substances are used to correct for sourcestrength intensity variations, and a 2•o Pb/organic compound correlation is established and extrapolated to adjust for rainfall volume effects. These corrections, assumed independent and applied together, yield inferred fluxes 2.5-9 times larger than the fluxes calculated for mean concentrations. The inferred fluxes to the ocean, while small compared to primary production, are large enough to have potential impacts in the cycle of dissolved organic carbon and the sedimentary geochemistry of refractory lipid components. INTRODUCTION The Sea-Air Exchange Program (SEAREX) conducted an atmospheric program in the wet and dry seasons at Enewetak Atoll, Marshall Islands, from April to August 1979. These measurements have yielded an extensive set of remote marine organic analyses. The goals of the program are to measure concentrations of components in the atmosphere and in rain and to infer their sources, transport mechanisms, and fluxes. Enewetak, which lies just north of the northernmost excursion of the ITCZ, proved to have very strong seasonal patterns in the delivery of atmospherically transported inorganic components of terrestrial origin [Duce et al., 1980]. Likewise, the aerosol concentrations of four lipid classes covaried with inorganic terrestrial markers (particulate A1 and 2•øpb) and showed concentration distributions indicating terrestrial plant sources [Gagosian et al., 1981, 1982]. In this paper we present anal...