The Atlantic dipole phosphate utilization (ADPU) index, derived through statistical conversion of 20th century Atlantic basin subpolar sea surface temperatures, is used as a fingerprint of Atlantic meridional overturning circulation (AMOC) variability and as an indicator of global Meridional Overturing Circulation (MOC) variability. ADPU index correlations with differences in sea level anomalies (SLAs) between Canada and the UK and across the Isthmus of Panama demonstrate intrabasin and interbasin associations with MOC variability. Cross-correlation analyses of ADPU index, SLAs, and sardine (S) and anchovy (A) catch differences [S A] (normalized sardine catch minus normalized anchovy catch) confirm strong correlations between ADPU and [S A] off Japan, California, Peru and Southwest Africa (Benguela). Statistically significant cross correlations also exist between the ADPU index and SLAs for Japan, California, Peru and Benguela, and for SLAs and [S A] for Japan, California and Peru, but the short time-series lengths compared with the length of the multidecadal cycle limit the interpretation of the observed lead-lags. Though correlation is not causality, the correlation analyses developed here are useful in support of hypothesis generation. The proposed hypothesis to explain the observed small pelagic fishery synchronies asserts: (i) ocean bathymetry and continental distributions interact with multidecadal variations in MOC strength that occur along the conceptual global conveyor belt to generate changes in global oceanic planetary waves and mesoscale eddies that propagate through the world ocean; (ii) each small pelagic fishery region has a unique spatial relationship with pertinent oceanic planetary wave and mesoscale eddy source regions that affect the timing and strength of the waves and eddies that influence the nearby boundary current; (iii) synchronous changes or phasing among global fisheries depend on how and when MOC variability mediated by oceanic planetary waves and mesoscale eddies reaches each fishery region; (iv) oceanic planetary waves and/or mesoscale eddies influence the strength or meandering of the boundary current adjacent to a small pelagic fishery region to change local SLAs and environmental conditions to favour sardine or anchovy populations at different times.

We have developed a Lagrangian model to investigate a potential mechanism based on phototaxis behavior of phytoplankton cells for the formation of thin layers. We assume that all cells follow a time-regulated diurnal vertical migration during which they experience photo-acclimation based on the Denman and Marra (1986) model. When a cell experiences stress due to strong light that exceeds a threshold level, the cell swims downward, away from the light. We applied the Lagrangian model to a one dimensional second order turbulence closure model that generates a realistic surface mixing condition for a given set of physical parameters, such as wind and optical water type. For the chosen swimming velocities and prescribed behavior, we found that, in coastal water type and Jerlov III type, thin layer formation takes place up to 5 m s−1 winds, while 10 m s−1 winds cause sufficiently strong mixing to prevent the formation of thin layer. We have also investigated the effects of changing the irradiance threshold for the onset of the photoinhibition, the initial density profile and random walk swimming. In conclusion, thin layer formation due to photoinhibition may be possible for a low value of photoinhibition threshold that may occur either due to upwelling or strong light exposure.

The current effort focuses on characterizing physical and biological conditions across the northwest Florida shelf during summer as they influence Karenia brevis distributions and phytoplankton/microphytobenthos community associations. Phytoplankton and benthic algal communities were examined in the context of cross-shelf hydrography and sediment conditions during July 2009 between the 20 and 65 m isobaths off Panama City, FL. A towed undulating profiler (SeaSciences Acrobat) mapped water column characteristics between near-surface and ∼1 m above the sediment. A CTD/rosette provided hydrographic profiles and collected water samples at 17 cross-shelf locations at selected depths for nutrient concentration, phytoplankton biomass determination, and chemotaxonomic and taxonomic phytoplankton identification. In addition, a CTD/rosette time series sample set was collected following a holey sock drogue set at ∼34 m along the ∼50 m isobath, and cores were collected at eight stations approximately along the 30, 40 and 55 m isobaths. Cross-shelf, a pycnocline existed at ∼10 m depth, the 1% light level penetrated to ∼45 m depth, and nitrate–nitrite (NO3−+NO2−) concentrations increased in the lower 10 m of the water column to the 50 m isobath and then below 40-m depth to the 65 m isobath. A chlorophyll a peak occurred near-bottom between the 25 and 35 m isobaths. Gyroxanthin dinoflagellates (GD) representing K. brevis occurred across the shelf in near-surface and near-bottom waters. Near-surface GD co-occurred with cyanophytes at low density in the upper 20 m of the water column where NO3−+NO2− concentrations were low. Above sediments in the euphotic zone, near-bottom GD were most abundant between the 25 and 35 m isobaths where the NO3−+NO2− concentrations were 1–4 µM and where microphytobenthos competed for nutrient sources. Below the euphotic zone, GD were present near-bottom to the 60 m isobath where NO3−+NO2− concentrations approached 6 µM. A pattern consistent with dinoflagellate diel vertical migration was inferred at the 50-m isobath time-series station. The results provide insight into offshore K. brevis seed populations and their associations with other phytoplankton and microphytobenthos. Under summer light and nutrient conditions along the northwest Florida shelf, K. brevis coastal blooms may be seeded by diffuse near-surface populations during occasional downwelling conditions and by more concentrated near-bottom populations during more prevalent upwelling conditions.

The regional impact of global climate change on the ocean circulation around the Galapagos Archipelago is studied using the Hybrid Coordinate Ocean Model (HYCOM) configured for a four-level nested domain system. The modeling system is validated and calibrated using daily atmospheric forcing derived from the NCEP/NCAR reanalysis dataset from 1951 to 2007. The potential impact of future anthropogenic global warming (AGW) in the Galapagos region is examined using the calibrated HYCOM with forcing derived from the IPCC-AR4 climate model. Results show that although the oceanic variability in the entire Galapagos region is significantly affected by global climate change, the degree of such effects is inhomogeneous across the region. The upwelling region to the west of the Isabella Island shows relatively slower warming trends compared to the eastern Galapagos region. Diagnostic analysis suggests that the variability in the western Galapagos upwelling region is affected mainly by equatorial undercurrent (EUC) and Panama currents, while the central/east Galapagos is predominantly affected by both Peru and EUC currents. The inhomogeneous responses in different regions of the Galapagos Archipelago to future AGW can be explained by the incoherent changes of the various current systems in the Galapagos region as a result of global climate change.

The Atlantic Meridional Overturning Circulation (AMOC), part of the global Thermohaline Circulation (THC), is variable. In the present analysis, an Atlantic Dipole Phosphate Utilization (ADPU) index, related to the existing Atlantic Dipole Sea Surface Temperature Anomaly (ADSA) index, is used to represent 20th century changes in AMOC strength that are applied to global ecosystem variability. ADPU index cycles set the timing for the calculation of six 2° latitude–longitude resolution world ocean maps depicting higher surface phosphate utilization (SPU) in some regions when AMOC is weaker and in other regions when AMOC is stronger. The average of these six maps yields a summary map with a pattern of alternating latitudinal SPU regions differentiated by AMOC strength that exhibits relationships with ocean bathymetry and wind-driven currents through a consideration of the THC deep and shallow limbs. The latitudinal pattern of SPU regions exhibits conceptual associations with sardine (S) and anchovy (A) population ranges off Japan (J), California (C), Peru (P) and South Africa (B). These sardine and anchovy populations have exhibited apparently synchronous fluctuations on decadal scales through at least part of the 20th century that is summarized in a Regime Indicator Series (RIS=(JS+CS+PS+BA)–(JA+CA+PA+BS)) index. In the present analysis based on Food & Agriculture Organization (FAO) catch data, a revised Regime Indicator Series index formulation (RIS3=(JS+CA+PS+BA)–(JA+CS+PA+BS)), in which CS and CA catches reverse positions, is defined. AMOC variability represented in ADPU is significantly correlated with the RIS3 index (no lag but a significant range of 14 years) and four of eight small pelagic fisheries (JS, PS, BA, and JA). The post-1950 RIS3 index is significantly correlated with seven of eight small pelagic fisheries but not CS. When the regional small pelagic fisheries are considered as normalized species differences (S-A), ADPU has significant positive correlations with Japan and Peru, and negative tendencies with California and South Africa, while the RIS3 index has significant positive correlations with Japan and Peru and significant negative correlations with California and South Africa. An extended RIS3 index, with pre-1950 catch data based only on Japan and California, continues a coherent, significantly correlated trend with the APDU index through 1920 (no lag but a significant range of 14 years). Though the mechanisms for multidecadal global synchrony are speculative, the global pattern of cyclical AMOC-related, alternating latitudinal SPU regions through the 20th century and the correlation of the ADPU index with the RIS3 and the extended RIS3 indices suggest a link between varying AMOC strength, ocean fertility and global marine ecosystem response. Signals from AMOC variability due to changes in both deep and shallow limb flow intensities propagate as Rossby and Kelvin waves through the Atlantic Ocean and possibly into the Indo-Pacific Ocean. Similar Rossby and Kelvin wave generation outside the Atlantic Ocean as a result of concurrent but complex global THC variability could reinforce AMOC-related planetary waves and contribute to the multidecadal global synchrony of ocean state and of responsive ecosystems. If present patterns continue into the future decades, a weaker AMOC associated with global warming would favor sardine off Japan and Peru and anchovy off California and South Africa.

Both the Atlantic Meridional Overturning Circulation (AMOC) and the North Atlantic Ocean (NA) biosphere have recognized associations with the North Atlantic Oscillation (NAO). These multidecadal physical–biological affinities inspired a closer look at AMOC influences on bottom-up control of NA and South Atlantic Ocean (SA) pelagic ecosystem variability. Various ocean models associate changes in the AMOC with sea surface temperature (SST) differences in the western subpolar NA and SA represented as the Atlantic Dipole SST Anomaly (ADSA) index. The Extended Reconstructed SST version 2 (ERSSTv2) dataset for 2° quadrangles from 1890 to 2007 was used here to represent Atlantic Ocean SST patterns and to gauge 20th century AMOC variability using an Atlantic Dipole SST (ADS) index, an un-normalized version of ADSA index. Temperature–phosphate (T–PO4) linear regressions were used to convert temperature to phosphate concentration ([PO4]). The interannual stability of T–PO4 linear regressions first was examined using 26 Bermuda area T–PO4 datasets between 1958 and 2001. Within the constraints provided by the Bermuda analysis, climatological T–PO4 linear regressions based on GEOSECS-derived slopes and NODC-derived X-intercepts supported the conversion of monthly Atlantic Ocean ERSSTv2 temperatures for each 2° quadrangle to monthly surface [PO4]. A representative annual surface phosphate utilization (SPU) was calculated for each 2° quadrangle by subtracting monthly minimum surface [PO4] from monthly maximum surface [PO4] to determine the annual surface [PO4] ranges from 1890 to 2007. Annual average SST tended to increase and overall annual average SPU tended to decrease through the 20th century in both the NA and SA, but the NA exhibited more temporal variability. An Atlantic Dipole Phosphate Utilization (ADPU) index related to the ADS index was calculated for each year from 1890 to 2007. The ADS and ADPU indices were inversely correlated with about 57% of the variability in the ADPU index explained by the ADS index. The ADPU index exhibited three distinct cycles through the 20th century. Cross-correlation analysis showed that the NAO led the ADS and ADPU indices by about 14 years. Differences in annual average SPU for each Atlantic Ocean 2° quadrangle between the three high and four low years of the ADPU cycles yielded six maps that, when averaged, clearly exhibited reversed east–west patterns distributed in alternating latitudinal bands in both the NA and SA. The east–west patterns spatially corresponded to the NA and SA surface circulation and temporally resembled NA patterns previously associated with the NAO. AMOC variability, mediated by Kelvin and Rossby waves associated with changes in both deep and surface arm circulation, likely contributed to meridional continuity of phosphate-classified, NA, and SA pelagic ecosystem variability, including fisheries, through the 20th century. Based on the results, future global warming influences on the AMOC, well short of shutdown, likely will have complex pelagic ecosystem impacts throughout the Atlantic Ocean.

Light and nutrient availability change throughout dinoflagellate diel vertical migration (DVM) and/or with sub-population location in the water column along the west Florida shelf. Typically, the vertical depth of the shelf is greater than the distance a sub-population can vertically migrate during a diel cycle, limiting the ability of a sub-population to photosynthetically fix carbon toward the surface and access nutrients sub-surface. This project investigated changes of Karenia brevis (C.C. Davis) G. Hansen et Moestrup intracellular carbon, nitrogen, internal nitrate (iNO3), free amino acid (FAA), and total lipid concentrations in high-light, nitrate-replete (960μmolquantam−2s−1, 80μM NO3), and high-light, nitrate-reduced (960μmolquantam−2s−1, <5μM NO3) mesocosms. The nitrate-reduced mesocosm had a slowed cell division rate when compared to the nitrate-replete mesocosm. Minimum intracellular carbon, nitrogen, iNO3, FAA, and total lipid concentrations during the largest surface sub-population aggregations led to the conclusion that daughter cells resulting from cell division received unequal shares of the parental resources and that this inequality influenced migration behavior. Nutrient reduced daughter cells were more strongly influenced by light and phototaxis for carbon production than their replete same cell division sister cells during vertical migration thus rapidly increasing the fulfillment of constituents through photosynthesis. Vertical migration was consistent with an optimization scheme based on threshold limits through utilization or formation of photosynthate. We propose a simplified conceptual model describing how K. brevis is transported along the benthos of the west Florida shelf from off-shore to on-shore. Dynamic carbon thresholds are also suggested for future DVM modeling efforts on K. brevis populations transported between nitrogen replete and nitrogen reduced environmental conditions.

The internal lipid, carotenoid, and toxin concentrations of Karenia brevis (C. C. Davis) Gert Hansen and Moestrup are influenced by its ability to use ambient light and nutrients for growth and reproduction. This study investigated changes in K. brevis toxicity, lipid class, and carotenoid concentrations in low‐light, nitrate‐replete (250 μmol quanta · m−2 · s−1, 80 μM NO3); high‐light, nitrate‐replete (960 μmol quanta · m−2 · s−1, 80 μM NO3); and high‐light, nitrate‐reduced (960 μmol quanta · m−2 · s−1, <5 μM NO3) mesocosms. Reverse‐phase HPLC quantified the epoxidation state (EPS) of the xanthophyll‐cycle pigments diadinoxanthin and diatoxanthin, and a Chromarod Iatroscan thin layer chromatography/flame ionization detection (TLC/FID) system quantified changes in lipid class concentrations. EPS did not exceed 0.20 in the low‐light mesocosm, but increased to 0.65 in the high‐light mesocosms. Triacylglycerol and monogalactosyldiacylglycerol (MGDG) were the largest lipid classes consisting of 9.3% to 48.7% and 37.3% to 69.7% of total lipid, respectively. Both lipid classes also experienced the greatest concentration changes in high‐light experiments. K. brevis increased EPS and toxin concentrations while decreasing its lipid concentrations under high light. K. brevis may mobilize its toxins into the surrounding environment by reducing lipid concentrations, such as sterols, limiting competition, or toxins are released because lipids are decreased in high light, reducing any protective mechanism against their own toxins.

The dinoflagellate Karenia brevis is responsible for nearly annual red tides in the Gulf of Mexico that cause extensive marine mortalities and human illness due to the production of brevetoxins. Although the mechanisms regulating its bloom dynamics and toxicity have received considerable attention, investigation into these processes at the cellular and molecular level has only begun in earnest during the past decade. This review provides an overview of the recent advances in our understanding of the cellular and molecular biology on K. brevis. Several molecular resources developed for K. brevis, including cDNA and genomic DNA libraries, DNA microarrays, metagenomic libraries, and probes for population genetics, have revolutionized our ability to investigate fundamental questions about K. brevis biology. Two cellular processes have received particular attention, the vegetative cell cycle and vertical migration behavior, which are of key importance due to their roles in the development of both surface populations that constitute blooms and subsurface cell aggregations that may serve to initiate them. High throughput sequencing of cDNA libraries has provided the first glimpse of the gene repertoire in K. brevis, with approximately 12,000 unique genes identified to date. Phylogenomic analysis of these genes has revealed a high rate of horizontal gene transfer in K. brevis, which has resulted in a chimeric chloroplast through the selective retention of genes of red, green, and haptophyte origin, whose adaptive significance is not yet clear. Gene expression studies using DNA microarrays have demonstrated a prevalence of post-transcriptional gene regulation in K. brevis and led to the discovery of an unusual spliced leader trans-splicing mechanism. Among the trans-spliced gene transcripts are type I polyketide synthases (PKSs), implicated in brevetoxin biosynthesis, which are unique among type I PKSs in that each transcript encodes an individual catalytic domain, suggesting a novel gene structure in this dinoflagellate. Clone libraries of 16S ribosomal DNA sequences developed from bloom waters have unveiled the temporal and spatial complexity of the microbial soup that coexists with K. brevis and its active involvement in both bloom growth and termination processes. Finally, the development and application of population genetic markers has revealed a surprisingly high genetic diversity in K. brevis blooms, long assumed to consist of essentially clonal populations. With these foundations in place, our understanding of K. brevis bloom dynamics is likely to grow exponentially in the next few years.

As a component of the ECOHAB Florida Regional Field Program, this study addresses cell cycle behavior and its importance to bloom formation of the Florida red tide dinoflagellate, Karenia brevis. The cell cycle of K. brevis was first studied by flow cytometry in laboratory batch cultures, and a laboratory mesocosm column, followed by field populations over the 5-year course of the ECOHAB program. Under all conditions studied, K. brevis displayed diel phased cell division with S-phase beginning a minimum of 6h after the onset of light and continuing for 12–14h. Mitosis occurred during the dark, and was generally completed by the start of the next day. The timing of cell cycle phases relative to the diel cycle did not differ substantially in bloom populations displaying radically different growth rates (μmin 0.17–0.55) under different day lengths and temperature conditions. The rhythm of cell cycle progression is independent from the rhythm controlling vertical migration, as similar cell cycle distributions are found at all depths of the water column in field samples. The implications of these findings are discussed in light of our current understanding of the dinoflagellate cell cycle and the development of improved models for K. brevis bloom growth.

Nutrient delivery to populations of Karenia brevis in oligotrophic water columns in the Gulf of Mexico remains uncertain. Aggregations of K. brevis near the sediment-water interface suggest that cells derive nutrients from the sediment. Video of cells near the sediment suggest that cells either access nutrients that flux out of the sediment or migrate into the sediment pores where higher nutrient concentrations exist. Experiments tested K. brevis' ability to migrate into the sediment using chambers divided by a 100 mu m mesh overlain with a thin layer of sediment. Since the diel vertical migration of K. brevis typically displays a nocturnal descent, experiments tested migration response at night in response to sub-sediment nutrient sources. The experiments suggest that while the sediment affects the progress of descending cells, migration occurs through thin layers of sediment and increases in response to elevated nutrient concentrations below the sediment. Since all cells found below the sediment had significantly higher C/N ratios than those remaining above the sediment, migration appears related to a cell's internal biochemical state. The vertical migration behavior of K. brevis may help alleviate bottom-up controls and permit populations to persist as vegetative cells near the sediment-water interface.

The ARGO free-drifting profiling float array, with >3125 floats deployed between 60°N and 60°S latitudes at about 3° resolution as of May 2008 and each float profiling through 2000m every 10 days, provides a comprehensive four-dimensional view of temperature and salinity in the world ocean. The resulting dataset complements satellite-based sea surface temperature (SST) measurements and similarly will complement future satellite-based sea surface salinity measurements. Although plans exist to add biogeochemical sensors to future floats, cost and depth restrictions may limit comprehensive upgrades to a fraction of all floats deployed after 2008. Temperature–nutrient (TN) relationships provide a mechanism to estimate nutrient concentrations from temperature to supplement sparser nutrient concentration measurements potentially obtained using non-chemical approaches like ISUS-based nitrate. Both negative and positive aspects of applying a temperature–phosphate (TP) linear regression matrix with global coverage (70°N and 70°S) are examined. The TP linear regression matrix was derived by combining an existing 1° latitude and longitude table of phosphate depletion temperatures (PDT) or X-intercepts with representative TP linear regression slopes derived from the GEOSECS dataset. Temperatures from datasets with associated latitude and longitude coordinates and, in some cases, measured phosphate concentrations ([PO4]) were matched with calculated TP linear regression slopes and Y-intercepts in the global matrix with 1° resolution using MSExcel Lookup worksheet functions to calculate TP-estimated [PO4]. The mean deviation of TP-estimated [PO4] <3.0μM from measured [PO4] is 0.18±0.18μM at Hawaii (HOT) and 0.04±0.08μM at Bermuda (BATS) time series stations and 0.28±0.27μM over all considered World Ocean Circulation Experiment (WOCE) stations representing the different ocean basins. In general, TP-estimated [PO4] represents measured [PO4] more accurately in the southern hemisphere than in the northern hemisphere. For the World Ocean Atlas 2005 (WOA05), a TP-estimated [PO4] map based on annual statistical mean SST approximates an annual statistical mean measured [PO4] map in overall geographic pattern but less so in absolute concentration. ARGO 0–10m temperature data and derived TP-estimated [PO4] maps from all 2006 compare more favorably with the WOA05 annual statistical mean SST and measured [PO4] maps. For winter 2006, ARGO 0–10m temperature and derived TP-estimated [PO4] maps favorably compare with MODIS mean SST and derived TP-estimated [PO4] maps. ARGO 30–50m and 75–100m temperatures from winter 2006 and derived TP-estimated [PO4] demonstrate that the ARGO dataset provides a subsurface nutrient complement to nutrient inferences based on MODIS SST. The TP-estimated [PO4] approach is responsive to changing conditions since the independent variable, temperature, integrates ambient environmental variability as expressed in the vertical thermal structure at the time of the ARGO profile. TP-estimated [PO4] can enhance the interpretation of developing ARGO-based ecosystem applications by providing more specific estimates of nutrient availability than temperature alone.

The Galapagos Marine Reserve (GMR) is one of the most diverse ecosystems in the world. Phytoplankton are the base of the ecosystem food chain for many higher trophic organisms, so identifying phytoplankton biomass distribution is the first step in understanding the dynamic environment for effective management of the GMR. Moderate Resolution Imaging Spectroradiometer (MODIS) and hyperspectral surface acquisition system derived chlorophyll, in-situ chlorophyll fluorescence, nitrate, salinity, and temperature were collected from March 2005 to the onset of a mild El Niño in November 2006. Islands in the eastern GMR, such as San Cristobal and Espanola, are the first to experience impacts of El Niño and southern migration of the Equatorial Front. Productive habitats were defined as surface waters with salinities > 34, temperatures < 24 °C, and chlorophyll a > 0.4 mg m− 3. Six temporally variable productive habitats identified were: west of Isabela Island, southwest of Floreana Island, south of Santa Cruz, between Santiago and Santa Cruz Islands, and on the eastern side near San Cristobal Island. Model results coupled with surface acquisition system derived chlorophyll indicated productive habitats may also occur for short periods and at a distance from islands such as when the Equatorial Undercurrent (EUC) and South Equatorial Current (SEC) collide over the seamounts north of Isabela Island. All productive habitats were related to topographic upwelling from the EUC into surface waters.

Many laboratories have solely used the Wilson isolate to physiologically characterize the harmful algal bloom (HAB) dinoflagellate Karenia brevis (C. C. Davis) G. Hansen et Moestrup. However, analysis of one isolate may lead to misinterpretations when extrapolating measurements to field populations. In this study, pulse‐amplitude‐modulated chlorophyll fluorometer (PAM‐FL) relative electron transport rate (ETR), Fv/Fm, and chl were compared with traditional techniques, such as 14C photosynthesis versus irradiance (P–E) curves, DCMU [3‐(3′,4′‐dichlorophenyl)‐1,1‐dimethyl urea] Fv/Fm, and extracted chl. The DCMU and PAM‐FL values of Fv/Fm (r2 = 0.51) and chl (r2 = 0.58) were in good agreement. There was no correlation between 14C and PAM‐FL α, Pmax, and β parameters because PAM‐FL ETR was only a relative measurement. The PAM‐FL techniques were then used to investigate P–E curves, quantum yield of PSII (Fv/Fm), and chl from 10 K. brevis isolates to determine whether one or all isolates would better represent the species. Comparisons were made with a radial photosynthetron, which allowed for controlled conditions of light and temperature. Isolate α, Pmax, and β varied between 0.097 and 0.204 μmol e− · m−2 · s−1 · (μmol quanta · m−2 · s−1)−1, 80.41 and 241 μmol e− · m−2 · s−1, and 0.005 and 0.160 μmol e− · m−2 · s−1 · (μmol quanta · m−2 · s−1)−1, respectively. Either carbon limitation and/or bacterial negative feedback were implicated as the cause of the P–E parameter variability. Furthermore, these results directly contradicted some literature suggestions that K. brevis is a low‐light‐adapted dinoflagellate. Results showed that K. brevis was more than capable of utilizing and surviving in light conditions that may be present on cloudless days off Florida.