Phytoplankton composition and biomass across the southern Indian Ocean (original) (raw)
Related papers
During the icebreaker SHIRASE cruise of the 27th Japanese Antarctic Research Expedition (JARE-27; 1985/86), vertical profiles of phytoplankton chlorophyll a concentration in the upper 200m of the water column were observed at 12 stations in the Southern Ocean and at 3 stations in the subtropical water from December 1985 to March 1986. High phytoplankton chlorophyll standing crops (ca. 370 mg m 2 in December and 330 mg m 2 in February) were observed in Breid Bay, Antarctica. In other stations of the Antarctic Ocean, the standing crops were less than 52 mg m 2 . Size fractionation studies revealed that net-phytoplankton (>20 p m ) was the dominant fraction of total chlorophyll a during the summer bloom in Breid Bay. In Antarctic waters, the high contributions of the net-phytoplankton fraction corresponded to high total biomass. And also, contribution of the net-phytoplankton to the total phytoplankton was supposed to be controlled by the length of the ice-free period. Considering the high phytoplankton growth rates under the nutrient rich condition, duration under optimum light condition and water stability appear to be important factors affecting the phytoplankton crops in the Antarctic Ocean in summer. key words: size fractioned chlorophyll a, vertical distribution, Southern Ocean, water stability, JARE-27
Deep-sea Research Part Ii-topical Studies in Oceanography, 2020
Phytoplankton, the primary producers in all aquatic systems, plays an important role in key biogeochemical processes that are linked to higher trophic levels and climate variability. The present study deals with the phytoplankton community structure in the Indian Ocean, particularly in the higher latitudes with respect to environmental variables to understand the region specific dominant community and its governing environmental settings. The study areas were selected along the latitudinal transect between 3oN and 53oS (northern Indian Ocean to Indian Ocean sector of Southern Ocean). The surface water phytoplankton community based on microscopy coupled with diagnostic pigment indices showed marked variation in community structure from tropical to polar latitudes of the Indian Ocean. The Prokaryotic diagnostic pigment (ProkDP) dominated in the Equatorial and South Equatorial regions, the Flagellate diagnostic pigment (FlagDP) in the North Equatorial region (NER), Southern Tropical In...
Phytoplankton across Tropical and Subtropical Regions of the Atlantic, Indian and Pacific Oceans
PLOS ONE, 2016
We examine the large-scale distribution patterns of the nano-and microphytoplankton collected from 145 oceanic stations, at 3 m depth, the 20% light level and the depth of the subsurface chlorophyll maximum, during the Malaspina-2010 Expedition (December 2010-July 2011), which covered 15 biogeographical provinces across the Atlantic, Indian and Pacific oceans, between 35°N and 40°S. In general, the water column was stratified, the surface layers were nutrient-poor and the nano-and microplankton (hereafter phytoplankton, for simplicity, although it included also heterotrophic protists) community was dominated by dinoflagellates, other flagellates and coccolithophores, while the contribution of diatoms was only important in zones with shallow nutriclines such as the equatorial upwelling regions. We applied a principal component analysis to the correlation matrix among the abundances (after logarithmic transform) of the 76 most frequent taxa to synthesize the information contained in the phytoplankton data set. The main trends of variability identified consisted of: 1) A contrast between the community composition of the upper and the lower parts of the euphotic zone, expressed respectively by positive or negative scores of the first principal component, which was positively correlated with taxa such as the dinoflagellates Oxytoxum minutum and Scrippsiella spp., and the coccolithophores Discosphaera tubifera and Syracosphaera pulchra (HOL and HET), and negatively correlated with taxa like Ophiaster hydroideus (coccolithophore) and several diatoms, 2) a general abundance gradient between phytoplankton-rich regions with high abundances of dinoflagellate, coccolithophore and ciliate taxa, and phytoplankton-poor regions (second principal component), 3) differences in dominant phytoplankton and ciliate taxa among the Atlantic, the Indian and the Pacific oceans (third principal component) and 4) the occurrence of a diatom-dominated assemblage (the fourth principal component assemblage), including several pennate taxa, Planktoniella sol, Hemiaulus hauckii and Pseudo-nitzschia spp., in the divergence regions.
Polar Biology, 1999
The composition of the phytoplanktonic communities in the surface waters of the La Reunion-Kerguelen transect (from 38°36S to 46°33S) has been investigated under spring conditions (AntareÁ s 3 cruise, France-JGOFS, 28 September±8 November, 1995). The study, conducted at six stations in the subtropical frontal zone, involved size fractionations (threshold: 2 lm). The large variations in the overall biomass and autotrophic carbon ®xation, calculated via Rubisco activity measurements and expressed respectively in terms of lg chlorophyll (a + b + c) per liter and nmol ®xed carbon dioxide per liter and per hour, were attributable only to phytoplanktonic cells of >2 lm, with a peak observed in the frontal zone. The picophytoplankton (<2 lm) biomass remained constant throughout the transect, but the evolution of the species composition of the picophytoplanktonic population, as calculated from ow cytometry measurements through this frontal zone, changed. This study provides evidence, for the ®rst time in this area, of the disappearance of prochlorophytes from the south of the frontal zone (42±47°S). Picoeukaryotes (<2 lm) and cyanobacteria populations, resolved by¯ow cytometry, were present all along the transect. However, their abundance decreased southward up to the quasi-disappearance of cyanobacteria at the southernmost station (52°S) that is characteristic of antarctic waters. The presence of prochlorophytes that is exclusive to the subtropical surface waters, and the low carbon ®xation activity associated with these waters, may be linked to the speci®c hydrological features encountered. In contrast, the marked reduction in the cyanobacteria and the abundance of picoeukaryotes along the north-south transect is more likely to be a result of the reduction in temperature through the frontal zone. Polar Biol (1999) 21: 90±96 Ó Springer-Verlag 1999 E. Fouilland á C. Descolas-Gros (8) á C. Courties á V. Pons
Environmental Monitoring and Assessment, 2014
The spatial variation of chlorophyll a (Chl a) and factors influencing the high Chl a were studied during austral summer based on the physical and biogeochemical parameters collected near the coastal waters of Antarctica in 2010 and a zonal section along 60°S in 2011. In the coastal waters, high Chl a (>3 mg m −3 ) was observed near the upper layers (∼15 m) between 53°30′E and 54°30′E. A comparatively higher mesozooplankton biomass (53.33 ml 100 m −3 ) was also observed concordant with the elevated Chl a. Low saline water formed by melting of glacial ice and snow, as well as deep mixed-layer depth (60 m) due to strong wind (>11 ms −1 ) could be the dominant factors for this biological response. In the open ocean, moderately high surface Chl a was observed (>0.6 mg m −3 ) between 47°E and 50°E along with a Deep Chlorophyll Maximum of ∼1 mg m −3 present at 30-40 m depth. Melt water advected from the Antarctic continent could be the prime reason for this high Chl a. The mesozooplankton biomass (22.76 ml 100 m −3 ) observed in the open ocean was comparatively lower than that in the coastal waters. Physical factors such as melting, advection of melt water from Antarctic continent, water masses and wind-induced vertical mixing may be the possible reasons that led to the increase in phytoplankton biomass (Chl a).
Polar bioscience, 2002
The abundance, size structure and community composition of phytoplankton in the Southern Ocean were studied, using flow cytometry, microscopy and pigment profiles on two transects one latitudinal (N) and one longitudinal (W) during December 1999 and January 2000. In both transects, the concentration of autotrophic eukaryotes of 2-10 µm equivalent spherical diameter (ESD) commonly exceeded those < 2 µm ESD. No cells > 10 µm ESD were detected by flow cytometry (however microscopy showed cells> 10 µm in length). Throughout transect N, chlorophyll a concentrations were generally <0.5 µg 1 •• 1 • South of the Antarctic Polar Front (APP), chlorophyll a concentrations increased southward. CHEMT AX allocation of pigment data (italicized) showed that Diatoms contributed most chlorophyll with Haptophytes subdominant. North of the APP, chlorophyll a concentrations tended to increase northward. Here, Haptophytes contributed most chlorophyll, followed by Diatoms, Chlorophytes and Cyanobacteria, except at the northernmost stations where Cyanobacteria dominated. In transect W, chlorophyll a concentrations were also <0.5 µg Ii in most cases, but variable. Higher concentra tions occasionally occurred in the west. In this transect, Diatoms contributed most (mean=6 l ± 15%) of the chlorophyll a, followed by Haptophytes. Nanodiatoms (particularly Fragilariopsis spp.) numerically dominated the diatom community. Fecal pellets composed of these nanodiatoms were observed in the Antarctic water, probably originating from heterotrophic dinoflagellates, implying a significant contribution of nanodiatoms to the microbial food web. However they contributed little to total chlorophyll a and diatom carbon biomass, particularly when chlorophyll and carbon concentrations were high.
Ocean Science, 2011
During the 1999 Marion Island Oceanographic Survey (MIOS 4) in late austral summer, a northbound and reciprocal southbound transect were taken along the Southwest Indian and Madagascar Ridge, between the Prince Edward Islands and 31 • S. The sections crossed a number of major fronts and smaller mesoscale features and covered a wide productivity spectrum from subtropical to subantarctic waters. Associated with the physical survey were measurements of size fractionated chlorophyll, nutrients and nitrogen (NO 3 , NH 4 and urea) uptake rates. Subtropical waters were characterised by low chlorophyll concentrations (max = 0.27.3 mg m −3 ) dominated by picophytoplankton cells (> 81%) and very low f-ratios (< 0.1), indicative of productivity based almost entirely on recycled ammonium and urea. Micro-phytoplankton growth was limited by the availability of NO 3 (< 0.5 mmol m −3 ) and Si(OH) 4 (< 1.5 mmol m −3 ) through strong vertical stratification preventing the upward flux of nutrients into the euphotic zone. Biomass accumulation of small cells was likely controlled by micro-zooplankton grazing. In subantarctic waters, total chlorophyll concentrations increased (max = 0.74 mg m −3 ) relative to the subtropical waters and larger cells became more prevalent, however smaller phytoplankton cells and low f-ratios (< 0.14) still dominated, despite sufficient NO 3 availability. The results from this study favour Si(OH) 4 limitation, light-limited deep mixing and likely Fe deficiency as the dominant mechanisms controlling significant new production by micro-phytoplankton.
Phytoplankton chlorophyll distributions and primary production in the Southern Ocean
Journal of Geophysical Research, 2000
Satellite ocean color data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) were used to examine distributions of chlorophyll concentration within the Southern Ocean for the period October 1997 through September 1998. Over most of the Southern Ocean, mean chlorophyll concentrations remained quite low (<0.3-0.4 mg m-3). Phytoplankton blooms where chlorophyll concentration exceeded 1.0 mg m -3 were observed in three general areas, which included coastal/shelf waters, areas associated with the seasonal sea ice retreat, and the vicinity of the major Southern Ocean fronts. These chlorophyll distribution patterns are consistent with an iron-limited system. Mean chlorophyll concentrations from SeaWiFS are compared with values from the coastal zone color scanner (CZCS). The SeaWiFS global chlorophyll algorithm works better than the CZCS in Southern Ocean waters. Primary production in the Southern Ocean was estimated with the vertically generalized production model of Behrenfeld and Falkowski [1997]. Annual primary production in the Southern Ocean (>30øS) was estimated to be 14.2 Gt C yr -•, with most production (-80%) taking place at midlatitudes from 30 ø to 50øS. Primary production at latitudes >50øS was estimated to be 2.9 Gt C yr -•. This is considerably higher than previous estimates based on in situ data but less than some recent estimates based on CZCS data. Our estimated primary production is sufficient to account for the observed Southern Hemisphere seasonal cycle in atmospheric 02 concentrations. 1. sociated with sea ice retreat, shallow waters, areas of strong upwelling, and regions of high eddy kinetic energy (mainly associated with Southern Ocean fronts) [Comiso et al., 1993]. The strongest correlation with pigments was a negative correlation between ocean depth and pigment concentrations, possibly the result of higher available iron concentrations in shallow water regions [Comiso et al., 1993]. Sullivan et al. [1993] also examined CZCS pigment data for the whole Southern Ocean. They noted intense phytoplankton blooms within and downstream of coastal/shelf areas, which they attributed to elevated iron availability [Sullivan et al., 1993]. Silicic acid availability may limit diatom production and biomass accumulation in several areas [Trdguer and Jacques, 1992; Sullivan et al., 1993]. Mitchell and Holm-Hansen [1991] developed a regional Southern Ocean pigment (SOP) retrieval algorithm for the CZCS on the basis of the bio-optical properties of Antarctic Peninsula waters. This regional pigment algorithm was deemed necessary because the global pigment (GP) algorithm for CZCS [Gordon et al., 1983] resulted in underestimates of surface chlorophyll concentrations in Southern Ocean waters [Mitchell and Holm-Hansen, 1991; Sullivan et al., 1993; Amigo et al., 1994]. Amigo et al. [1994] provided correction factors for converting GP pigment estimates to SOP pigment values. The SOP pigment values are higher than the GP estimates by a factor ranging from -2.1 to 2.5 for chlorophyll concentrations below 1.5 mg m -3 [Amigo et al., 1994]. In this study, Sea-viewing Wide Field-of-view Sensors (SeaWiFS) satellite-based estimates of surface chlorophyll concentrations are used to examine phytoplankton biomass distributions and dynamics within the Southern Ocean. We use a broad definition for the Southern Ocean encompassing the area from the Antarctic continent north to 30øS. This northern 28,709 28,710 MOORE AND ABBOTT: SOUTHERN OCEAN PHYTOPLANKTON CHLOROPHYLL Ocean, Science, 262, 1832-1837, 1993. Takeda, S., Influence of iron availability on nutrient consumption ratio of diatoms in oceanic waters, Nature, 393, 774-777, 1998. Tr6guer, P., and G. Jacques, Dynamics of nutrients and phytoplankton, and fluxes of carbon, nitrogen, and silicon in the Antarctic Ocean,
Deep-sea Research Part Ii-topical Studies in Oceanography, 2007
Deep chlorophyll maxima (DCM) have the capacity to fuel substantial fractions of total water column production. The ecological importance of a ubiquitous DCM layer ranging from 50 to 120 m deep within Leeuwin Current (LC) and offshore waters of Western Australia is addressed here using data from a regional oceanographic field study conducted during the austral summer of 2000. Phytoplankton communities from surface and DCM layers were compared by examining pigments (chlorophyll a), phytoplankton carbon, photosynthetic characteristics and productivity rates estimated using 14C-based photosynthesis versus irradiance relationships. In the DCM layer, both extracted pigments (up to 0.83 mg m−3) and phytoplankton carbon (6.4–54.4 mg C m−3) were maximal, and were on average 6 and 5 times larger than in the surface layer, respectively. Sensitivity analyses were performed on production estimates using regionally relevant ranges of light attenuation (Kd=0.050–0.066 m−1) and photoinhibition (β*=0.00–0.01 mg C (mg chl a)−1 h−1 [μmol m−2 s−1]−1). These analyses provide upper and lower limits on previously reported estimates of primary production for the region, and show that small differences in light attenuation and photoinhibition can significantly affect computations of primary production and cause a shift from surface-dominated to DCM-dominated production scenarios. The contribution of the DCM layer to total water-column production ranged from a maximum of 30–70% under the scenarios examined. A regional overview of nitrate and stratification conditions in relation to the depth of the phytoplankton biomass maximum indicated that the critical balance between light and nutrients was a key factor driving DCM structure. We show that changing oceanographic conditions in both the along-shore and cross-shore directions, which included latitudinal variation in the strength of the LC, are accompanied by changes in the depth (and in turn production) of the DCM. The previously unrecognized significance of these DCM layers in the coastal eastern Indian Ocean has important implications for satellite-based estimates of production within the region.