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Climate change will alter concurrently many environmental factors that exert control over oceanic phytoplankton. Recent laboratory culture work, shipboard experiments, and field surveys reveal many remaining unknowns about the bottom-up controls for five globally important algal groups. Increasing uncertainties exist, respectively, for picocyanobacteria, diatoms, Phaeocystis spp., [N.sub.2]-fixing cyanobacteria, and coccolithophores. This missing information about current environmental controls will hinder progress in modeling how these phytoplankton will be influenced by climate change. A review of conceptual approaches used to elucidate the relationship between environmental controls and phytoplankton dominance, from Margalef's mandala to functional traits, uncovered limitations regarding their application to climate-change scenarios. For example, these previous approaches have insufficient scope or dimensions to take into account the confounding effects of synergistic and antagonistic interactions of multiple environmental change variables. A new approach is needed that considers all of the different environmental properties altered by climate change and their interactions while at the same time permitting a subset of the most significant controls for a specific phytoplankton group to be isolated and evaluated in factorial matrix perturbation experiments. We advocate three new interlinked approaches, including environmental clusters that incorporate all factors (temperature, C[O.sub.2], light, nutrients, and trace metals), which both exert control over present-day floristics and will be altered by climate change. By carefully linking a holistic conceptual approach to a reductionist experimental design, the future responses of open-ocean phytoplankton groups to a complex, rapidly changing environment can be better predicted. doi: 10.4319/lo.2010.55.3.1353

To study how natural Southern Ocean phytoplankton communities acclimate to rapid fluctuations in irradiance levels that result from deep wind-driven mixing of the upper water column, we measured their fluorescence properties (Fv:Fm, maximum quantum yield of photosystem II; and qN, non-photochemical quenching) and pigment composition. Values of Fv:Fm were low (< 0.46) and qN was high (> 0.67) throughout the upper mixed layer (UML). Short-term (20-min) exposure to incident surface irradiance strongly reduced Fv:Fm and recovery was slow under subsequent incubation at low irradiance. This suggests that phytoplankton cells are frequently photodamaged when mixed up to the surface from depth. Recovery of Fv:Fm was suppressed when lincomycin was added, inhibiting synthesis of the photosystem II reaction center D1 protein. This indicates that D1 protein repair is crucial in maintaining photosynthetic performance under fluctuating irradiance levels. Regions within the Antarctic Circumpolar Current (ACC) with a deep UML had lower depth-integrated phytoplankton biomass than regions close to the Antarctic continent with a shallow UML. Surprisingly, the depth-averaged light level within the UML in these latter regions was lower than in the ACC. Thus, it appears that photodamage incurred during the high irradiance portion of the vertical mixing cycle, rather than light limitation, controls phytoplankton growth in regions of the Southern Ocean with a deep UML. This concept represents a shift from the widely accepted paradigm that phytoplankton growth in the open Southern Ocean is limited by low levels of light or inadequate iron supply. doi: 10.4319/lo.2010.55.3.1248

We compile two data sets from [sup.14]C uptake and dilution experiments conducted in surface waters of the global ocean to investigate the relationship between phytoplankton mass-specific growth rate and cell size. After temperature correction, both data sets suggest that this relationship might be described by a unimodal quadratic curve with the modal size (the size corresponding to the maximal growth rate) being 2.8 and 5.4 [micro]m in the [sup.14]C and dilution data sets, respectively. Nutrient enrichment does not change the qualitative nature of the relationships, and we conclude that inherently low maximal growth rates of picophytoplankton, not ambient nutrient effects, play the major role in determining the positive relationships over the size range where phytoplankton size is below the modal size. Temperature-corrected phytoplankton grazing mortality rate is positively correlated with phytoplankton average size, but the proportion of daily primary production consumed by microzooplankton is negatively correlated with cell size, suggesting a reduced grazing effect as size increases. The unimodal relationship between phytoplankton growth rate and cell size is consistent with theoretical considerations and might reflect an adaptive response of phytoplankton to varying extents of nutrient limitation and grazing effect in marine systems. doi: 10.4319/lo.2010.55.3.0965

We analyzed a 9-yr record of ocean color data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) together with a 4-yr record of satellite-derived sea surface temperature (SST) measurements to investigate potential mechanisms influencing nearshore phytoplankton variability in the Southern California Bight. We also compared in situ physicochemical conditions at four shoreline stations during a year with an extensive nearshore dinoflagellate red tide (2005) to those of the following year when there was no extended red tide (2006). SeaWiFS data indicated that in spring, chlorophyll a (Chl a) and nitrate (N[O.sup.-.sub.3]) were inversely correlated to SSTs, consistent with an upwelling-dominated system, but in summer Chl a and NO-3 were unrelated to SST. Summer dissolved inorganic nitrogen concentrations were not well correlated between alongshore sampling stations, but showed a significant effect of tide stage (low vs. high). Mean summer nearshore Chl a was positively, linearly related to rainfall in the previous winter. The relationship between summer Chl a and winter precipitation could be due either to direct freshwater inputs during the winter rainy season or to delayed input via groundwater discharge. A first-order analysis of nutrient delivery from both surface runoff and groundwater discharge showed that they could sustain summer blooms of up to 7540 and 1700 [km.sup.2], respectively--areas on the order of the study site. However, precipitation-induced physical changes to the nearshore water column cannot be conclusively ruled out as a potential causative mechanism.

The aim of this study was to determine the effects of the tidal dynamics and physical forcing on phytoplankton distribution and photosynthesis dynamics in the Chubut River estuary, Argentina. Physical, chemical, and biological variables measured at the surface and at the bottom of the water column (variable between 0.5-m and 6-m depth) were made every 30-45 d during tidal cycles (13 h of duration) from June 2007 to November 2008 (11 tidal cycles). There was a remarkable consistency among different tidal cycles throughout the year, with strong stratification during the flood and almost complete mixing during the period high tide--ebb--low tide. Strong stratification during the flood resulted in significant inhibition of photosynthesis of mostly nanoplankton cells at the surface, while microplankton sank out of this upper layer and, thus, were less inhibited. Mixing conditions during the ebb, together with relatively high concentration of dissolved organic matter and particulate material, resulted in partial protection for phytoplankton against solar radiation stress and, therefore, relatively high maximum electron transport rate values were determined under this condition. However, the lowest photoinhibition and higher maximum rate of production ([P.sub.max]) values occurred at depth during stratified conditions, probably due to relatively low solar radiation in this condition. Tidal dynamics together with physical forcing are key factors that condition the distribution, dynamics, and photoinhibition of phytoplankton in the Chubut River estuary.

Abstract: In 2003, the Georges Bank stock of haddock (Melanogrammus aeglefinus) experienced the largest recruitment event recorded during its assessed history. Several hypotheses have been advanced to explain recruitment variability [...]

Water-type (WT) definition as a function of bio-optical properties has relevance to the exploitation of satellite ocean color data because it may provide a mean to optimize the atmospheric correction process or select the most appropriate bio-optical algorithm for the determination of optically significant constituents in seawater. Within such a framework, this paper defines a WT index assuming the existence of two extreme conditions. On one side, there are waters with optical properties totally depending on the phytoplankton component. On the other side, waters characterized by fully unrelated bio-optical quantities. The index of intermediate WTs is then defined on a statistical basis, and the resulting scheme is applied to a set of experimental data collected in an optically complex coastal region. Finally, in view of supporting remote sensing applications, a neural network algorithm is implemented to identify WTs using the normalized water leaving radiance. Index Terms--Ocean color, remote sensing, water type (WT).

Byline: Akiyoshi Shinada (1), Syuhei Ban (1), Tsutomu Ikeda (1) Keywords: Microbial food web; dilution method; micro-zooplankton; HNF; bacteria Abstract: Seasonal changes in nano/micro-zooplankton grazing on pico-, nano- and micro-size phytoplankton and heterotrophic nano-flagellates (HNF) feeding on heterotrophic bacteria were quantified by the dilution technique in the surface layer off Cape Esan, southwestern Hokkaido, Japan. Pico- and nano-size phytoplankton were major components throughout the year except in spring when a diatom bloom was observed. Although there was little seasonal variation in bacteria and HNF biomass throughout the year, the micro-zooplankton biomass varied appreciably with a peak in spring. Nano/micro-zooplankton grazing or feeding on pico-size chl-a and bacteria were well balanced throughout the year. However, nano-size and micro-size chl-a growth were much greater than grazing in summer. Nano/micro-zooplankton ingestion of phytoplankton was greater than their ingestion of bacteria almost throughout the year, which suggests phytoplankton are more important as food sources of nano/micro-zooplankton in microbial food webs off Cape Esan than bacteria off Cape Esan. Author Affiliation: (1) Faculty of Fisheries Science, Hokkaido University, Minato-cho, Hakodate, 041-0821, Japan Article History: Registration Date: 06/10/2004

The study focuses on the impact on phytoplankton growth and phytoplankton distributions due to submesoscale vertical motions by modeling a phytoplankton population in a baroclinically unstable submesoscale eddy. Results show that plankton distributions depend strongly on the light intensity and local vertical transport.

As oceans take up more carbon dioxide, their increasing acidity could be decreasing the weight of one of the most abundant calcium-producing marine phytoplankton. Low pH is known to interfere [...]