Hydrothermal vents trigger massive phytoplankton blooms in the Southern Ocean

Ardyna, Mathieu; Lacour, Léo; Sergi, Sara; d’Ovidio, Francesco; Sallée, Jean Baptiste; Rembauville, Mathieu; Blain, Stéphane; Tagliabue, Alessandro; Schlitzer, Reiner; Jeandel, Catherine; Arrigo, Kevin R.; Claustre, Hervé

doi:10.1038/s41467-019-09973-6

Cited by 87 publications

(64 citation statements)

References 33 publications

(46 reference statements)

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“…The second float (Float ID: 5904683) is located downstream of the Kerguelan Plateau and drifts along the Subantactic Front (SAF; Figures b and S3a). This is a region of vigorous eddy activity, and the presence of the Kerguelan Islands and hydrothermal vents can act as a source of lithogenic/benthic iron here (Ardyna et al, ; Blain et al, ; Bowie et al, ; Gille et al, ; Schallenberg et al, ). This float happened to see a short‐lived period of growth in July, but the onset to apex is from August till the end of December.…”

Section: Resultsmentioning

confidence: 99%

“…To the north of the SAF, Ekman downwelling results in a deep nutricline and nutrient limitation year round (McClain et al, ; Wilson & Coles, ), likely causing low values of

r_{normalp}^{climax}

and Δ ao . The very high rates to the south of the sACCF are likely associated with the iron fertilization via glacial and sea ice melt (Ardyna et al, ; Boyd & Ellwood, ; Boyd et al, ; McGillicuddy et al, ).…”

Section: Discussionmentioning

confidence: 99%

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Southern Ocean Phytoplankton Blooms Observed by Biogeochemical Floats

et al. 2019

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The spring bloom in the Southern Ocean is the rapid-growth phase of the seasonal cycle in phytoplankton. Many previous studies have characterized the spring bloom using chlorophyll estimates from satellite ocean color observations. Assumptions regarding the chlorophyll-to-carbon ratio within phytoplankton and vertical structure of biogeochemical variables lead to uncertainty in satellite-based estimates of phytoplankton carbon biomass. Here, we revisit the characterizations of the bloom using optical backscatter from biogeochemical floats deployed by the Southern Ocean Carbon and Climate Observations and Modeling and Southern Ocean and Climate Field Studies with Innovative Tools projects. In particular, by providing a three-dimensional view of the seasonal cycle, we are able to identify basin-wide bloom characteristics corresponding to physical features; biomass is low in Ekman downwelling regions north of the Antarctic Circumpolar Current region and high within and south of the Antarctic Circumpolar Current. Plain Language SummaryThe advent of satellites has allowed us to observe the ocean surface on unprecedented scale. One of the major biogeochemical findings from these observations was that phytoplankton in the Southern Ocean repeatedly went through a dramatic phase of growth every spring basin wide. Phytoplankton, however, exist not only at the ocean surface but also in the interior, generally in the top 100 m. In our study, we revisit the characterization of this spring growth using autonomous floats that vertically profile biogeochemical properties including phytoplankton concentration, providing three-dimensional estimates of phytoplankton. Our results support the conventional knowledge of there being a robust seasonal cycle in phytoplankton within and south of the Antarctic Circumpolar Current region, an energetic eastward current that wraps around Antarctica.

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Section: Resultsmentioning

confidence: 99%

“…To the north of the SAF, Ekman downwelling results in a deep nutricline and nutrient limitation year round (McClain et al, ; Wilson & Coles, ), likely causing low values of

r_{normalp}^{climax}

Section: Discussionmentioning

confidence: 99%

Southern Ocean Phytoplankton Blooms Observed by Biogeochemical Floats

et al. 2019

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“…Thus, vent primary chemosynthetic production is exported at least as far as ~90 m in the Lucky Strike vent field. This energy may be used by taxa exclusively found at these sites, establishing spatial subsidies that may extent the vent’s “sphere of influence” (sensu Levin et al 2016) far from areas under direct vent fluid influence (Reid et al 2013, Bell et al 2017, Ardyna et al 2019, Le Bris et al 2019). Much effort has been invested in raising awareness on the largely under‐sampled and poorly studied inactive sulfide deposits, the main mining industry target (Van Dover 2019).…”

Section: Discussionmentioning

confidence: 99%

High environmental stress and productivity increase functional diversity along a deep‐sea hydrothermal vent gradient

Alfaro-Lucas

Pradillon

Zeppilli

et al. 2020

Ecology

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Productivity and environmental stress are major drivers of multiple biodiversity facets and faunal community structure. Little is known on their interacting effects on early community assembly processes in the deep sea (>200 m), the largest environment on Earth. However, at hydrothermal vents productivity correlates, at least partially, with environmental stress. Here, we studied the colonization of rock substrata deployed along a deep‐sea hydrothermal vent gradient at four sites with and without direct influence of vent fluids at 1,700‐m depth in the Lucky Strike vent field (Mid‐Atlantic Ridge [MAR]). We examined in detail the composition of faunal communities (>20 μm) established after 2 yr and evaluated species and functional patterns. We expected the stressful hydrothermal activity to (1) limit functional diversity and (2) filter for traits clustering functionally similar species. However, our observations did not support our hypotheses. On the contrary, our results show that hydrothermal activity enhanced functional diversity. Moreover, despite high species diversity, environmental conditions at surrounding sites appear to filter for specific traits, thereby reducing functional richness. In fact, diversity in ecological functions may relax the effect of competition, allowing several species to coexist in high densities in the reduced space of the highly productive vent habitats under direct fluid emissions. We suggest that the high productivity at fluid‐influenced sites supports higher functional diversity and traits that are more energetically expensive. The presence of exclusive species and functional entities led to a high turnover between surrounding sites. As a result, some of these sites contributed more than expected to the total species and functional β diversities. The observed faunal overlap and energy links (exported productivity) suggest that rather than operating as separate entities, habitats with and without influence of hydrothermal fluids may be considered as interconnected entities. Low functional richness and environmental filtering suggest that surrounding areas, with their very heterogeneous species and functional assemblages, may be especially vulnerable to environmental changes related to natural and anthropogenic impacts, including deep‐sea mining.

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“…However, individual studies have shown that remineralization (Boyd et al, 2017), upwelling (Rosso et al, 2016), and lateral advection (Bowie et al, 2009) are important. The impact of remote advection was excluded here but has been shown to be important (Graham et al, 2015), as have hydrothermal vents (Ardyna et al, 2019;Tagliabue et al, 2010) and aeolian dust (Jickells et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

Iron Supply Pathways Between the Surface and Subsurface Waters of the Southern Ocean: From Winter Entrainment to Summer Storms

Nicholson¹,

Lévy

Jouanno

et al. 2019

Geophysical Research Letters

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Dissolved iron (DFe) plays an immeasurable role in shaping the biogeochemical processes of the open-ocean Southern Ocean. However, due to observational constraints iron supply pathways remain poorly understood. Using an idealized eddy-resolving physical-biogeochemical model representing a turbulent sector of the Southern Ocean with seasonal buoyancy forcing and zonal winds overlaid by storms, we quantify the importance of a range of subsurface and surface iron supply mechanisms. The main physical supply pathways to the surface layer are via eddy advection and winter convective mixing in equal proportions. The associated subsurface loss of DFe is restocked via net remineralization (75%) and eddy advection (25%). Summer storms resulted in weak DFe supplies relative to the seasonal supplies (<7.6%). However, in situations of deep summer mixed layers and when interacting with underlying ocean fronts, summer storms resulted in enhanced diffusive and advective DFe supplies and raised summer primary production by 20% for several days. Plain Language SummaryThe surface of the Southern Ocean is iron depleted, which strongly limits the amount of phytoplankton growth that can occur. Every year, deep mixing in winter moves large quantities of iron from a subsurface underutilized iron reservoir to the surface alleviating the iron limitation. Once there is sufficient light in spring, phytoplankton consume this iron supply leaving the summer months iron depleted. How exactly phytoplankton are supported through the summer when iron limitations are strong remains under question. This study uses a numerical model to simulate the seasonal and intraseasonal iron supply pathways. We show that physical supplies via advection by eddies and winter mixing drive surface seasonal supplies in equal proportions. During summer, storms supply iron via intermittent mixing and thus increase primary production, particularly over regions of strong ocean fronts.

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Hydrothermal vents trigger massive phytoplankton blooms in the Southern Ocean

Cited by 87 publications

References 33 publications

Southern Ocean Phytoplankton Blooms Observed by Biogeochemical Floats

Southern Ocean Phytoplankton Blooms Observed by Biogeochemical Floats

High environmental stress and productivity increase functional diversity along a deep‐sea hydrothermal vent gradient

Iron Supply Pathways Between the Surface and Subsurface Waters of the Southern Ocean: From Winter Entrainment to Summer Storms

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