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Surface pigment data from a transect along the eastern boundary of the Atlantic Ocean was analysed using CHEMTAX to yield more detailed information on the composition of phytoplankton communities. Total chlorophyll a concentrations varied from 0.03 mg m?3 in a northern oligotrophic region to 30.3 mg m?3 in the Benguela ecosystem. Diatoms dominated the Benguela, while both diatoms and haptophytes were the major groups in the Canary ecosystem and the temperate NE Atlantic. Prochlorococcus was the most prominent group in the southern oligotrophic region (15.5°S-15°N) although haptophytes were also a significant component of the population. In contrast, haptophytes dominated the northern oligotrophic region (21°-40°N). Photo-pigment indices indicated that chlorophyll b was mainly associated with prasinophytes and chlorophyll c with diatoms. Elevated photosynthetic carotenoids were due to increased proportions of haptophytes, but also linked with diatoms and dinoflagellates. Photoprotective carotenoids were more prominently associated with Prochlorococcus and to a lesser extent to Synechococcus.

Error-quantified, synoptic-scale relationships between chlorophyll-a (Chl-a) and phytoplankton pigment groups at the sea surface are presented. A total of ten pigment groups were considered to represent three Phytoplankton Size Classes (PSCs, micro-, nano- and picoplankton) and seven Phytoplankton Functional Types (PFTs, i.e. diatoms, dinoflagellates, green algae, prymnesiophytes (haptophytes), pico-eukaryotes, prokaryotes and Prochlorococcus sp.). The observed relationships between Chl-a and PSCs/PFTs were well-defined at the global scale to show that a community shift of phytoplankton at the basin and global scales is reflected by a change in Chl-a of the total community. Thus, Chl-a of the total community can be used as an index of not only phytoplankton biomass but also of their community structure. Within these relationships, we also found non-monotonic variations with Chl-a for certain pico-sized phytoplankton (pico-eukaryotes, Prokaryotes and Prochlorococcus sp.) and nano-sized phytoplankton (Green algae, prymnesiophytes). The relationships were quantified with a least-square fitting approach in order to enable an estimation of the PFTs from Chl-a where PFTs are expressed as a percentage of the total Chl-a. The estimated uncertainty of the relationships depends on both PFT and Chl-a concentration. Maximum uncertainty of 31.8% was found for diatoms at Chl-a = 0.49 mg m−3. However, the mean uncertainty of the relationships over all PFTs was 5.9% over the entire Chl-a range observed in situ (0.02 < Chl-a < 4.26 mg m−3). The relationships were applied to SeaWiFS satellite Chl-a data from 1998 to 2009 to show the global climatological fields of the surface distribution of PFTs. Results show that microplankton are present in the mid and high latitudes, constituting only ~10.9% of the entire phytoplankton community in the mean field for 1998–2009, in which diatoms explain ~7.5%. Nanoplankton are ubiquitous throughout the global surface oceans, except the subtropical gyres, constituting ~45.5%, of which prymnesiophytes (haptophytes) are the major group explaining ~31.7% while green algae contribute ~13.9%. Picoplankton are dominant in the subtropical gyres, but constitute ~43.6% globally, of which prokaryotes are the major group explaining ~26.5% (Prochlorococcus sp. explaining 22.8%), while pico-eukaryotes explain ~17.2% and are relatively abundant in the South Pacific. These results may be of use to evaluate global marine ecosystem models.

The phytoplankton pigment composition (chlorophylls and carotenoids) from 17 Atlantic Meridional Transect (AMT) cruises over the period 1995–2005 was analysed to determine the distributions of pigments and plankton in the Atlantic Ocean between 50°N and 50°S. Data were quality assured by statistical methods, including regression of total chlorophyll a (TChla) versus accessory pigments (AP) and comparison of the AMT-TChla with contemporary SeaWiFS-TChla (cruises AMT-05 to -17). Comparisons of province-mean TChla (±SD) for in situ and satellite data showed good agreement for each cruise. ‘Taxa-specific’ pigments were used to define phytoplankton functional types (PFTs) for each of the biogeochemical provinces along the AMT. Pigment ratios (e.g. TChla/AP) were analysed for each cruise and for each province as indices (characteristic properties) of particular PFTs. Mostly robust positive correlations were observed between TChla and pigment ratios for different PFTs, for some provinces and most cruises. These were consistent with previous observations. Generally there were no significant trends of mean TChla or pigment ratios within provinces over the period 1995–2005, although the previously reported perturbation due to the 1997–1998 ENSO was evident.

Estimating the primary productivity of phytoplankton as they are mixed through the surface layer is often hampered by methodological or conceptual constraints. Fast Repetition Rate Fluorometry (FRRF) allows some of these constraints to be overcome by providing measurements of the instantaneous, depth-dependent rates of primary productivity of phytoplankton in situ. Data acquired by FRR fluorescence is used in this paper to determine the parameters of the photosynthesis‐irradiance curve and the instantaneous photosynthetic rates for phytoplankton from the mixed layer during a cruise in the Celtic Sea in May 2000. FRR fluorescence-based estimates of the initial slope of the photosynthesis‐light curve (� B ) ranged from 7.5 in well-mixed conditions to 12.7 g C (mol photons) � 1 m 2 (g Chl a) � 1 under stratified conditions. FRR fluorescence-based estimates of the light saturation parameter, Ek, were strongly correlated with the logarithm of the surface PAR. FRR fluorescence-based estimates of the Chl a-specific, light saturated photosynthesis rate (Pm B ) ranged from 1.4 to 2.8 g C (g Chl a) � 1 h � 1 . The FRRF determined values of Pm B were consistent with those measured using radiocarbon techniques, however, there were systematic differences

Phytoplankton photosynthetic quantum efficiency (PQE), pigments, absorption characteristics, species composition (converted to phytoplankton carbon, Cph) and other variables were measured at an offshore site in the western English Channel throughout 2001, using an opportunistic weekly sampling schedule. The variation of chlorophyll-a (Chla) and other phytoplankton pigments followed the classical seasonal cycle, driven by incident light, patterns of stratification and nutrient availability. Phytoplankton and pigment concentrations were low in the winter, rising to a peak in the spring ‘bloom’, with episodic blooms throughout the summer, an autumn bloom and a decline to the winter minimum. Surface layer Chla and total pigment (Tpig) concentrations were highly correlated for the whole year, yet it was observed that the fraction of Chla in Tpig (Chla/Tpig) was not constant and had a distinct seasonal pattern, low in winter and higher in spring, summer and autumn blooms. Chlorophyll-a/Tpig was linearly correlated with recent ambient light fluxes and maximum PQE (PQEm) throughout most of the year, though more significantly within seasonal periods. Chlorophyll-a and Tpig were both linearly correlated to Cph and the Chla/Cph ratio was significantly correlated with both Chla/Tpig and PQEm. Also the optical absorption ratios, a674/a443 and a674/a490 were significantly correlated with PQE and Chla/Tpig, indicating probable optical signatures for these two parameters. The seasonal cycle of measurements of photosynthetic quantum efficiency provided a bench-mark against which all the photosynthetically-driven seasonal changes of biological properties can be understood, in terms of incident solar radiation and nutrient availability. We conclude that phytoplankton synthesize Chla preferentially to other pigments or carbon compounds in conditions beneficial to growth. The PQEm, the ratios of Chla/Tpig, Chla/Cph and a674/a443 are greater when plants are growing actively. In periods of nutrient sufficiency, PQEm, Chla/Tpig and a674/a443 are all linear functions of the mean total photon flux for the recent few days. Photosynthetically driven changes in Chla synthesis, cause observed changes of Chla/Tpig and Chla/Cph ratios.

Pigment patterns and associated absorption properties of phytoplankton were investigated in the euphotic zone along two meridional transects in the Atlantic Ocean, between the UK and the Falkland Islands, and between South Africa and the UK. Total chlorophyll a (TChla=MVChla+DVChla+chlorophyllide a) concentrations and the biomarker pigments for diatoms (fucoxanthin), nanoflagellates and cyanobacteria (zeaxanthin) appeared to have similar distribution patterns in the spring and in the autumn in the temperate NE Atlantic and the northern oligotrophic gyre. Divinyl chlorophyll a levels (prochlorophytes) were greater in spring at the deep chlorophyll maximum in the oligotrophic gyre, however. Marked seasonal differences were observed in the NW African upwelling region. TChla concentrations were twice as high in the upper mixed layer in the spring, with the community dominated by diatoms and prymnesiophytes (19?-hexanoyloxyfucoxanthin). A layered structure was prevalent in the autumn where cyanobacteria, diatoms and prymnesiophytes were located in the upper water column and diatoms and mixed nanoflagellates at the sub-surface maximum. In the South Atlantic, the Benguela upwelling ecosystem and the Brazil-Falklands Current Confluence Zone (BFCCZ) were the most productive regions with the TChla levels being twice as high in the Benguela. Diatoms dominated the Benguela system, while nanoflagellates were the most ubiquitous group in the BFCCZ. Pigment concentrations were greater along the eastern boundary of the southern oligotrophic gyre and distributed at shallower depths. Deep chlorophyll maxima were a feature of the western boundary oligotrophic waters, and cyanobacteria tended to dominate the upper water column along both transects with a mixed group of nanoflagellates at the chlorophyll maximum. Absorption coefficients were estimated from spectra reconstructed from pigment data. Although absorption was greater in the productive areas, the TChla-specific coefficients were higher in oligotrophic regions. In communities that were dominated by diatoms or nanoflagellates, pigment absorption was generally uniform with depth and attenuating irradiance, with TChla being the major absorbing pigment at 440 nm and photosynthetic carotenoids (PSC) at 490 nm. Absorption by chlorophyll c and photoprotective carotenoids (PPC) was much lower. Populations where cyanobacteria were prevalent were characterized by high PPC absorption, particularly at 490 nm, throughout most of the euphotic zone. The data suggested that the effect of pigments on the variability of phytoplankton absorption was due primarily to the variations in absorption by PPC.

Reduced sulfur gases and optical properties were measured in the upper ocean during an Atlantic Meridional Transect cruise of the RRS James Clark Ross from England to the Falkland Islands in 1998. Sea surface concentrations of carbonyl sulfide (COS) exhibited a pronounced diel variation at low latitudes but no diel cycle at mid and high latitudes possibly because of oceanic fronts and the longer hydrolysis time constant in cold water. The highest COS concentrations were observed in coastal and upwelling areas. CS2 concentrations varied less than those of COS, and the highest concentrations were found in the North African upwelling area with decreasing concentrations both northward and southward of this maximum. Dimethylsulfide (DMS) had the largest concentrations in the upper ocean, but methyl mercaptan (CH3SH) was an important reduced sulfur species in some coastal and upwelling areas. This may be associated with high bacterial growth rates. Colored dissolved organic matter (CDOM) fluorescence and absorbance also exhibit the highest values in coastal and upwelling areas and the lowest values in the southern subtropical gyre. The results suggest that carbon disulfide (CS2) outgassed from the oceans and oxidized in the atmosphere may represent a larger source of COS to the atmosphere than the direct flux of COS across the sea-air interface.

We present a synthesis of physical, chemical and biological shipboard observations of a convergent front at 2°N, 140°W and its surrounding environment. The front was a component of a tropical instability wave generated by shear between westward-flowing equatorial waters to the south and warmer equatorial counter current water to the north. Surface waters on the cold side were undersaturated with oxygen, which suggests that the water had only been exposed at the sea surface for a period of a few weeks. Although the atmospheric exposure time was short, the effects of biological activity could be detected in enhanced concentrations of total (dissolved plus suspended particulate) organic carbon concentration, proving that TOC can be produced in the top centimeters of the changing environmental conditions. The front itself was dominated by the accumulation of a “patch” of buoyant diatoms Rhizosolenia castracanei concentrated in the top centimeters of the warm surface water north of the front, and elevated chlorophyll concentrations were observed from the air over a spatial scale of order 10–20 km northward from the front. The nitrogen budget and thorium data suggest that a significant fraction of the elevated POC, and virtually all of the PON, arrived in the patch waters as imported particles rather than in situ photosynthesis. Photosynthetic uptake of carbon appears to have occurred in patch waters, but without corresponding uptake of fixed nitrogen (an uncoupling of the usual Redfield stoichiometry). Solute chemistry of the patch appears to be controlled by turbulent mixing, which flushes out patch waters on a time scale of days

Rates of phytoplankton production and nitrogen assimilation were measured at various stations along a transect in the northwestern Indian Ocean, from near the equator, northwards into the upwelling system off the Arabian peninsula, during September–October 1986. The measurements were made using in situ incubation techniques with the simultaneous use of 14C and 15N isotopes. Samples were fractionated after the incubations into three size classes: 0.2–0.8μm, 0.8–5.0 μm, and >5.0μm for the 14C incubations; and 5μm for the 15N incubations. The assimilation of nitrate and ammonium was measured. These measurements were supported by a detailed description of the horizontal and vertical distributions of chlorophyll, temperature and underwater light field, by the deployment of a towed undulating oceanographic recorder. Rates of primary production ranged from approximately 0.5 g C m−2 day−1 at the equator, reducing to 2.5 in the upwelling region off the coast of Oman; total nitrogen assimilation followed a similar pattern. Very significant variations in the size distribution of the activity of the plankton were observed. Over 75% of the carbon and nitrogen assimilation was in the

The Atlantic Meridional Transect (AMT) cruises have been operating since 1995 with SeaWiFS satellite ocean colour data being available since September 1997. AMT sampling includes both underway and CTD stations with analysis of chlorophyll-a undertaken through HPLC. Matchups between AMT HPLC and SeaWiFS chlorophyll-a have been analysed using the SeaWiFS 8-day composites, and there is generally a good agreement (R2 from 0.68-0.91, slopes from 0.89-1.08 and intercepts of less than plusmn0.19). However, the long time series has uncovered inconsistencies which could be attributed to biases in the HPLC data once further research is undertaken

2004 ENVISAT Symposium, Salzburg, AUSTRIA, SEP, 2004; We measured water leaving reflectance, phytoplankton pigments, optical properties and photosynthetic parameters in the southern Benguela ecosystem in October 2002. These data were used to validate MERIS standard products: reflectance (MERIS wavelengths) and Case 1 Chlorophyll- a. In this heterogeneous area, accurate validation required sampling within a few minutes of the satellite overpass. Inter-pigment relationships e. g. Total Chlorophyll (TChla) to Total Pigment (TP) were robust (R-2 similar to 0.99) yet pigment ratios (TChla/TP) were not constant (range 0.44 to 0.62) increasing log-linearly with biomass (R-2 similar to 0.7). Photosynthetic parameters (e. g. Photosynthetic Quantum Efficiency, PQE) and optical ratios (a(676)/a(440)) also increased log-linearly with biomass (R-2 similar to 0.8). PQE, pigment and optical ratios were linearly inter-correlated (R-2 similar to 0.7 to 0.8). From these data we derived the bio-optical traits for several phytoplankton functional types (PFTs): micro-plankton (diatoms and dinoflagellates) had high biomass, pigment ratios and PQE; nano-flagellates had low to intermediate biomass, pigment ratios and PQE; prokaryotes had very low biomass, pigment ratios and PQE. We present MERIS data analysed for PFTs and new products (PQE).

The interaction of the atmosphere and the ocean has a profound effect on climate, while the uptake by the oceans of a major fraction of atmospheric carbon dioxide has a moderating influence. By improving accuracy in the quantification of the ocean’s carbon dioxide budget, a more precise estimation can be made of the terrestrial fraction of global carbon dioxide budget and its subsequent effect on climate change. First steps have been taken towards this from an environmental and economic point of view, by using an instance based reasoning system, which incorporates a novel clustering and retrieval method. This paper reviews the problems of measuring the ocean’s carbon dioxide budget and presents the model developed to resolve them.