Influence of iron on algal community composition and physiological status in the Peru upwelling system

DiTullio, Giacomo R.; Geesey, Mark E.; Maucher, Jennifer M.; Alm, Melissa B.; Riseman, S. F.; Bruland, Kenneth W.

doi:10.4319/lo.2005.50.6.1887

Cited by 39 publications

(21 citation statements)

References 39 publications

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“…In contrast, the southern coastal upwelling and offshore regions of the Peru Current lack this external supply of iron and the waters evolve into Fe‐limited HNLC “blue waters” containing relatively low diatom biomass and Chl a [ Minas and Minas , 1992; Bruland et al , 2005]. “Blue water” phytoplankton communities are dominated by haptophytes [ Hutchins et al , 2002], whereas large diatoms are the most abundant phytoplankton group inhabiting the coastal upwelling “brown waters” [ Rojas de Mendiola , 1981; Wilkerson et al , 2000; Iriarte and Gonzalez , 2004; DiTullio et al , 2005].…”

Section: Study Regionmentioning

confidence: 99%

Alkenone unsaturation in surface sediments from the eastern equatorial Pacific: Implications for SST reconstructions

Kienast¹,

MacIntyre²,

Dubois³

et al. 2012

Paleoceanography

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[1] Significant uncertainties persist in the reconstruction of past sea surface temperatures in the eastern equatorial Pacific, especially regarding the amplitude of the glacial cooling and the details of the post-glacial warming. Here we present the first regional calibration of alkenone unsaturation in surface sediments versus mean annual sea surface temperatures (maSST). Based on 81 new and 48 previously published data points, it is shown that open ocean samples conform to established global regressions of U K′ 37 versus maSST and that there is no systematic bias from seasonality in the production or export of alkenones, or from surface ocean nutrient concentrations or salinity. The flattening of the regression at the highest maSSTs is found to be statistically insignificant. For the near-coastal Peru upwelling zone between 11-15°S and 76-79°W, however, we corroborate earlier observations that U K′ 37 SST estimates significantly over-estimate maSSTs at many sites. We posit that this is caused either by uncertainties in the determination of maSSTs in this highly dynamic environment, or by biasing of the alkenone paleothermometer toward El Niño events as postulated by Rein et al. (2005).

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Section: Study Regionmentioning

confidence: 99%

Alkenone unsaturation in surface sediments from the eastern equatorial Pacific: Implications for SST reconstructions

Kienast¹,

MacIntyre²,

Dubois³

et al. 2012

Paleoceanography

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“…The potential for Fe‐limited growth conditions in this region has been demonstrated by Fe enrichment experiments and via comparison of dissolved Fe concentrations, chlorophyll a biomass, phytoplankton fluorescence characteristics, and molecular Fe stress signatures (Bruland et al, ; DiTullio et al, ; Eldridge et al, ; Hutchins et al, ; Martin et al, ). The possible role of cobalt (Co) in (co‐)limiting part of the extant phytoplankton community has also been predicted for this region (Hawco et al, ; Saito et al, ); furthermore, this has been demonstrated directly in the Costa Rica Dome further to the north (Saito et al, ).…”

Section: Introductionmentioning

confidence: 99%

Influence of Iron, Cobalt, and Vitamin B₁₂ Supply on Phytoplankton Growth in the Tropical East Pacific During the 2015 El Niño

Browning

Rapp

Schlösser

et al. 2018

Geophysical Research Letters

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Iron (Fe), cobalt (Co), and vitamin B 12 addition experiments were performed in the eastern Equatorial Pacific/Peruvian upwelling zone during the 2015 El Niño event. Near the Peruvian coastline, apparent photosystem II photochemical efficiencies (F v /F m ) were unchanged by nutrient addition and chlorophyll a tripled in untreated controls over 2 days, indicating nutrient replete conditions. Conversely, Fe amendment further away from the coastline in the high nitrate, low Fe zone significantly increased F v /F m and chlorophyll a concentrations. Mean chlorophyll a was further enhanced following supply of Fe + Co and Fe + B 12 relative to Fe alone, but this was not statistically significant; further offshore, reported Co depletion relative to Fe could enhance responses. The persistence of Fe limitation in this system under a developing El Niño, as previously demonstrated under non-El Niño conditions, suggests that diminished upwelled Fe is likely an important factor driving reductions in offshore phytoplankton productivity during these events. Plain Language Summary Phytoplankton productivity in the Equatorial Pacific is critical forcurbing CO 2 outgassing from upwelling waters and sustaining globally important fisheries. We tested which micronutrients were limiting phytoplankton growth in the Equatorial Pacific during the 2015 El Niño. To date evidence for nutrient limitation status during these events remains indirect. We show iron is limiting offshore of Peru and that cobalt or vitamin B 12 could be approaching limitation, with limitation by the latter micronutrients possibly becoming more important further offshore. Linked to satellite data, the new results shed light on critical controls on marine productivity in this biogeochemically/economically important region. Our results suggest reduced upwelled iron-predicted under El Niño conditions would be primarily responsible for observed offshore Peru productivity decreases.

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“…The relative contribution of phytoplankton groups to total Chl a was calculated using the CHEMTAX matrix factorization software (Mackey et al, 1996). We used an initial ratio matrix that was based on ratios developed by DiTullio et al (2005) and Mackey et al (1996) for the equatorial Pacific and Peruvian upwelling region. Slight modifications were made in order to account for the presence of the pigment aphanizophyll (Apha).…”

Section: Methodsmentioning

confidence: 99%

Mechanisms of P* Reduction in the Eastern Tropical South Pacific

et al. 2017

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Water masses influenced by oxygen minimum zones (OMZ) feature low inorganic nitrogen (N) to phosphorus (P) ratios. The surplus of P over N is thought to favor non-Redfield primary production by bloom-forming phytoplankton species. Additionally, excess phosphate (P * ) is thought to provide a niche for nitrogen fixing organisms. In order to assess the effect of low inorganic nutrient ratios on the stoichiometry and composition of primary producers, biogeochemical measurements were carried out in 2012 during a research cruise in the eastern tropical South Pacific (ETSP). Based on pigment analyses, a succession of different phytoplankton functional groups was observed along onshore-offshore transects with diatoms dominating the productive upwelling region, and prymnesiophytes, cryptophytes, and Synechococcus prevailing in the oligotrophic open ocean. Although inorganic nutrient supply ratios were below Redfield proportions throughout the sampling area, the stoichiometry of particulate organic nitrogen to phosphorus (PON:POP) generally exceeded ratios of 16:1. Despite PON:POP ≥ 16, high P * -values in the surface layer (0-50 m) above the shelf rapidly decreased as water masses were advected offshore. There are three mechanisms which can explain these observations: (1) non-Redfield primary production, where the excess phosphorus in the biomass is directly released as dissolved organic phosphorus (DOP), (2) non-Redfield primary production, which is masked by a particulate organic matter pool mainly consisting of P-depleted detrital biomass, and/or (3) Redfield primary production combined with dinitrogen (N 2 ) fixation. Our observations suggest that the three processes occur simultaneously in the study area; quantifying the relative importance of each of these mechanisms needs further investigation. Therefore, it remains uncertain whether the ETSP is a net sink for bioavailable N or whether the N-deficit in this area is replenished locally.

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Influence of iron on algal community composition and physiological status in the Peru upwelling system

Cited by 39 publications

References 39 publications

Alkenone unsaturation in surface sediments from the eastern equatorial Pacific: Implications for SST reconstructions

Alkenone unsaturation in surface sediments from the eastern equatorial Pacific: Implications for SST reconstructions

Influence of Iron, Cobalt, and Vitamin B₁₂ Supply on Phytoplankton Growth in the Tropical East Pacific During the 2015 El Niño

Mechanisms of P* Reduction in the Eastern Tropical South Pacific

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Influence of iron on algal community composition and physiological status in the Peru upwelling system

Cited by 39 publications

References 39 publications

Alkenone unsaturation in surface sediments from the eastern equatorial Pacific: Implications for SST reconstructions

Alkenone unsaturation in surface sediments from the eastern equatorial Pacific: Implications for SST reconstructions

Influence of Iron, Cobalt, and Vitamin B12 Supply on Phytoplankton Growth in the Tropical East Pacific During the 2015 El Niño

Mechanisms of P* Reduction in the Eastern Tropical South Pacific

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Influence of Iron, Cobalt, and Vitamin B₁₂ Supply on Phytoplankton Growth in the Tropical East Pacific During the 2015 El Niño