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Chlorophyll and carotenoid pigments were measured at stations in the Bismarck Sea north of Papua New Guinea and along the equator between 143°E and 152°E as part of the Tropical River Ocean Processes In Coastal Settings (TROPICS) programme in August 1997 and January/February 2000. Algal class abundances were estimated from these pigments using the CHEMTAX programme. The algal classes likely to be present (based on microscopy, HPLC chromatograms, literature and unpublished data from the region) and estimated by CHEMTAX were diatoms, cryptophytes, chlorophytes, haptophytes, chrysophytes, Synechococcus and Prochlorococcus. The first period corresponded to the SE tradewind season, when there was a drought in Papua New Guinea and the discharge from the Sepik River was unusually low. Samples were collected on four N–S transects (approximately 150 km in length): one to the east of the Sepik River, one from the mouth of the Sepik River and two to the west of the Sepik River. Stations in the central Bismarck Sea and along the equator were characterised by a deep chlorophyll maximum (DCM), and haptophytes and Prochlorococcus were the major algal classes. Stations affected by the Sepik River plume were characterised by a more homogeneous distribution of chlorophyll with chlorophytes making a significant contribution, particularly at shallower depths. Synechococcus and chrysophytes were moderately abundant, while cryptophytes and diatoms were of minor importance. The second cruise occurred during the NW monsoon under conditions of high river flow, and samples were collected along a transect from the mouth of the Sepik River to Manus Island and in the central Bismarck Sea. Chlorophyll concentrations were higher than in 1997, particularly in near surface waters, while a DCM was generally not observed at any station in the Bismarck Sea—even at stations upstream (and upwind) and far removed from the mouth of the Sepik River. Prochlorococcus made a smaller, and chlorophytes a larger, contribution to chlorophyll than in 1997. Unlike the situation in 1997, there were large station to station variations in the vertical profiles of chlorophyll and algal class distributions which cannot be attributed directly to the plume from the Sepik River. Pigment ratios, fitted by the CHEMTAX programme, were generally in good agreement with literature values.

In both the warm pool region and the high-nutrient low-chlorophyll (HNLC) region of the equatorial Pacific, the phytoplankton community is dominated by high concentrations of picophytoplankton regardless of whether El Nino, La Nina or normal conditions prevail. Flow cytometry measurements indicate that the picoplankton community consists of two species of prokaryotes, Prochlorococcus and Synechococcus, and a diverse mixture of picoeukaryotes that cannot be differentiated. Analyses of chlorophyll and carotenoid pigments, determined by HPLC, confirm the importance of Prochlorococcus and Synechococcus and indicate that the eukaryotes are predominantly haptophytes. There are at least three ecotypes of Prochlorococcus and, possibly, various ecotypes of Synechococcus. These ecotypes have quite different pigment ratios and, possibly, pigment to carbon ratios, which complicates comparisons between cell counts by flow cytometry and the contribution that prokaryotes make to total chlorophyll as calculated from pigment analysis. Increased productivity is associated with the transient influx of nutrients, El Nino conditions in the warm pool, or surface nutrients in HNLC waters. Under these conditions there seems to be a small increase in the relative abundances of Synechococcus, diatoms and chlorophytes. Grazing of picophytoplankton by macro-grazers may make an important contribution to the ‘biological pump’, which may not be dominated by large phytoplankton such as diatoms.

Nine lakes in northern Wisconsin were sampled from February through September 1996, and HPLC analysis of water column pigments was carried out on epilimnetic seston. Pigment distributions were evaluated throughout the water column during summer in Crystal Lake and Little Rock Lake. The purpose of our study was to investigate the use of phytopigments as markers of the main taxonomic groups of algae. As a first approach, multiple regression of marker pigments against chlorophyll a (chl a) was used to derive the best linear combination of the main xanthophylls (peridinin, fucoxanthin, alloxanthin, lutein, and zeaxanthin). A significant regression equation (r2 = 0.98) was obtained for epilimnion data. The good fit indicates that the chl a:xanthophyll ratios were fairly constant in the epilimnion of the nine lakes over time. Chlorophyll a recalculated from the main xanthophylls in each sample showed good agreement with measured chl a in epilimnetic waters. A second approach used the CHEMTAX program to analyze the same data set. CHEMTAX provided estimates of chl a biomass for all algal classes and allowed distinction between diatoms and chrysophytes, and between chlorophytes and euglenophytes. These results showed a reasonably good agreement with biomass estimates from microscope counts, despite uncertainties associated with differences in sampling procedure. Changes of pigment ratios over time in the epilimnetic waters were also investigated, as well as differences between surface and deep samples of Little Rock Lake and Crystal Lake. We found evidence that changes in the ratio of photoprotective pigments to chl a occurred as a response to changes in light climate. Changes were also observed for certain light-harvesting pigments. The comparison between multiple regression and CHEMTAX analyses for inferring chl a biomass from concentrations of marker pigments highlighted the need to take account of variations in pigment ratio, as well as the need to acquire additional data on the pigment composition of planktonic algae.

Phytoplankton samples were collected from the equatorial Pacific (10°S to 10°N along 155°E) in June 1992 as part of the Australian contribution to the JGOFS program. Chlorophyll and carotenoid pigments were measured by HPLC, and a PC-based computer program (CHEMTAX) was used to estimate the contribution of 9 algal classes to the total chlorophyll a concentration in 9 separate depth bands at each location. This cruise occurred in the middle of the prolonged 1991/1993 El Nino, and the results are compared with similar data from a cruise in October 1990 which occurred before this El Nino but after the 1988/1989 La Nina. Changes in the pigment : chlorophyll a ratios appeared consistent across algal classes and, apart from some minor exceptions, consistent between cruises. Pigments involved in light-harvesting generally increased relative to chlorophyll a with increasing depth, whereas the ratio for photoprotective pigments (e.g. diadinoxanthin) usually decreased with depth. The zeaxanthin concentration per cell for cyanobacteria decreased with depth in the surface 75 m during 1992 as would be expected for a photoprotective pigment. Based on their contribution to the total chlorophyll a concentration, haptophytes, prochlorophytes, cyanobacteria ( Synechococcus) and chlorophytes were the dominant algal classes in 1992. The chlorophyte contribution to chlorophyll a in 1992 (14.8%) was almost double that in 1990 (7.8%). This increase was largely at the expense of the cyanobacteria and haptophytes, which both decreased significantly. The increase in chlorophytes in 1992 was particularly noticeable in the surface waters south of the equator at about 4°S, where there was evidence of upwelling.

Samplels for the analysis of phytoplankton photosynthesis pigments were collected from the equatorial Pacific (5°N to 15°S along 155°E) in October 1990 as part of the Australian contribution to the JGOFS program. Chlorophyll and carotenoid pigments were measured by HPLC using a diode-array detector. A PC-based computer program was used to optimise the pigment ratios and to estimate the contributions of 10 algal classes to the total chlorophyll a concentration at each location and in 7 separate depth bands. For the pigments that occur in more than one algal class, the pigment: chlorophyll a ratios for 19′-butanoyloxyfucoxanthin and 19′-hexanoyloxyfucoxanthin (chrysophytes and haptophytes), neoxanthin (prasinophytes, euglenophytes and chlorophytes) and chlorophyll b (prasinophytes, euglenophytes, prochlorophytes and chlorophytes) increase with depth, while those of violaxanthin (prasinophytes and chlorophytes), diadinoxanthin (dinoflagellates, chrysophytes, haptophytes, euglenophytes and diatoms), lutein (prasinophytes and chlorophytes) and, zeaxanthin (prasinophytes, cyanobacteria, prochlorophytes and chlorophytes) decrease with depth. Peridinin: chlorophyll a increases with depth in dinoflagellates, while alloxanthin: chlorophyll a decreases with depth in cryptomonads. The only pigment ratio that does not change consistently with depth is that of fucoxanthin, which increases with depth in chrysophytes and haptophytes but decreases in diatoms. Based on their contribution to the total chlorophyll a , cyanobacteria ( Synechococcus ) were dominant in the nutrient depleted surface waters, haptophytes were dominant at mid depth (70 m), and prochlorophytes were dominant at depths of 100–125 m. These three algal classes were by far the most important, and each contributed up to 30–40% of the total chloro-phyll a at some depth within the water column. Chlorophytes and chrysophytes contributed up to a maximum of about 12% of the total chlorophyll a , while cryptophytes, diatoms, dinoflagellates, prasinophytes and (possibly) euglenophytes generally contributed up to 4–8% of the chlorophyll a .

Bathurst Harbour and Macquarie Harbour are estuarine systems on the west coast of Tasmania, Australia. While Macquarie Harbour is grossly polluted from mine operations via contamination of the King River, Bathurst Harbour is surrounded by World Heritage wilderness and is essentially free of anthropogenic influences. The vegetation of the catchments of both harbours is similar and the waters of both harbours are deep brown due to the presence of humic substances. A hydrographic survey of the pristine Bathurst Harbour estuarine system was carried out over 4 days in January/February of 1990 (Austral Summer). Sampling and laboratory analyses for a range of trace elements (Cd, Co, Cu, Fe, Mn, Ni, and Zn) were made using non-contaminating procedures. The concentrations of dissolved cadmium (0.02 – 0.06 nM) and nickel (2.4 – 4.9 nM) were essentially the same as the total reactive concentrations. A significant fraction of copper and zinc was associated with particles since the concentrations of dissolved copper (2.2–3.7 nM) and zinc (6–45 nM) were often less than the concentrations of total reactive copper (2.7 – 6.7 nM) and zinc (10–58 nM). The concentrations of copper, cadmium and nickel were comparable with levels in open-ocean seawater. Total reactive concentrations of iron and manganese were very high in the rivers entering Bathurst Harbour (7900 and 124 nM, respectively) and a large fraction of these metals was associated with particulate matter particularly as the salinity increased. The lowest concentrations of iron and manganese were found in filtered waters at salinity ( S ) ≈ 35 (31 and 10 nM, respectively). The large amounts of organic matter draining into the estuarine system have fixed ratios between the fractions: dissolved organic carbon, humic substances, and copper-complexing capacity. This implies that it may be possible to estimate the copper-complexing capacity from a simple measurement of light absorbance. The copper-complexing capacity is a measure of the concentration of organic matter that is able to form strong complexes with copper and its concentration (7–93 nM) was in excess of the total concentration of copper in all samples from this survey. Comparison of results from this survey, with those from Macquarie Harbour in the summer of 1989, provided a clearer assessment of the effects of mining operations on trace metal concentrations in Macquarie Harbour.

During October 1990 in the western equatorial Pacific, from 5°S to 5°N along 155°E, the isothermal and isopycnal lines (near 150 m) domed upwards, surface temperatures were high (29.5–30.5°C), surface salinites were low (33.8–34.2), SST anomalies were

Metal—organic complexes were isolated from seawater by adsorption on reversed-phase chromatographic supports such as C18 Sep-Pak cartridges and XAD-2 resin and subsequent elution with methanol, acetonitrile or tetrahydrofuran. Preliminary results indicate that Sep-Pak cartridges packed with Styragel are also suitable, although back pressures are higher and low blank values are difficult to achieve. Analysis of the extracts by high-performance liquid chromatography with atomic fluorescence detection of trace metals showed that methanol extracts remain unchanged for up to three months in polypropylene at temperatures between −20°C and 20°C and in glass at −20°C. No changes were observed in acetonitrile extracts stored for one week at −20°C, even though the wet extract separated into two phases. Rapid freezing of C18 Sep-Pak cartridges to /t-195°C also seemed to be a suitable method for preserving samples for future analysis. High-intensity lamps improved the sensitivity of the atomic fluorescence detector by 1/2-2 orders of magnitude and zinc, magnesium, copper, nickel and iron could be determined simultaneously with detection limits ranging from 0.05 μg l−1 (zinc) to 7 μg l−1 (iron). The chromatograms were calibrated by standard additions of trace metals. All the chromatographic columns investigated (C18 Resolve, C18 Nova-Pak, PRP-1 and Protein-Pak 125) contained impurity sites that could interfere with the analysis of metal—organic compounds at the ultra-trace level. As interference was most pronounced for magnesium—organic complexes, magnesium was used as an indicator of the presence of coordinating sites on the chromatographic support. Interference effects could be reduced by the addition of modifying agents containing alkali metal salts at a concentration of 50 mM. The most suitable salt was potassium trifluoromethanesulfonate. Metal—organic compounds were isolated on XAD-2 resin (waters from Storm Bay, Tasmania), and on C18 Sep-Pak cartridges (waters from south-east Australian waters and the Fiji Basin). The concentrations of copper (410 pM), zinc (650 pM) and iron (800 pM) organic complexes from south-east Australian waters were higher than the values obtained for copper (60/2-120 pM), zinc (50/2-150 pM and iron (150/2-180 pM) organic complexes isolated from the Fiji Basin.