Increased ocean carbon export in the Sargasso Sea linked to climate variability is countered by its enhanced mesopelagic attenuation

Lomas, Michael W.; Steinberg, Deborah K.; Dickey, Tommy D.; Carlson, Craig A.; Nelson, Norman B.; Condon, Rob; Bates, Nicholas R.

doi:10.5194/bg-7-57-2010

Cited by 116 publications

(167 citation statements)

References 62 publications

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“…Chl a concentrations follow predictable annual patterns during the northwestern Sargasso Sea spring bloom ( Figure 1a) (Steinberg et al, 2001;Lomas et al, 2010). Over the period of this data set, Chl a standing stock, integrated over the photic zone (0-140 m), increased with the onset of mixing and peaks 2 months following the DM events.…”

Section: Resultsmentioning

confidence: 91%

“…Two previous studies, based on the same suite of BATS phytoplankton data from 1990 to 1997 (Steinberg et al, 2001) and additional data extending to 2007 (Lomas et al, 2010) have shown that the bloom can begin as early as January and as late as April. These studies show that the calendar month is irrelevant to the timing of the bloom and that rather the month of DM serves as the best indicator of the bloom onset.…”

Section: Resultsmentioning

confidence: 99%

“…Their average contribution peaked following DM events (Figures 3d, 5e and 6f). Other time-series studies (Steinberg et al, 2001;Lomas et al, 2010) have concluded that diatoms appear episodically at BATS and may be becoming increasingly rare at this site. The period most heavily represented in our data set-1998-2003-corresponds to a period in which diatom abundances were shown to decline at BATS (Lomas et al, 2010).…”

Section: Identification Of Plastid Peaks In T-rflp Datamentioning

confidence: 99%

“…Patterns of primary production (Menzel and Ryther, 1960;Lohrenz et al, 1992;Michaels and Knap, 1996;Steinberg et al, 2001) and the temporal variability of specific phytoplankton groups have been studied extensively at BATS with a variety of approaches, including radiotracers (Brzezinski and Nelson, 1995;Nelson and Brzezinski, 1997), photosynthetic pigment proxies (Bidigare et al, 1990;Goericke, 1998;Steinberg et al, 2001;Lomas and Bates, 2004), flow cytometric measurements of phytoplankton abundance (Olson et al, 1990;Li et al, 1992;DuRand et al, 2001) and growth (Li et al, 1992;Worden and Binder, 2003a, b;Cuvelier et al, 2010). Most notably, a recent study at BATS showed a 450% increase in chlorophyll a (Chl a) data between 1996 and 2007 (Lomas et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…The Bermuda Atlantic Time-Series Study (BATS), initiated in 1988, is one of the lengthiest oceanographic time-series studies, and includes complete records of biogeochemical and biological properties of the water column, such as nutrients, cell counts and phytoplankton pigments (Steinberg et al, 2001;Lomas et al, 2010), as well as extensive physical and meteorological measurements (Michaels and Knap, 1996). Furthermore, several studies have addressed prokaryotic population dynamics at BATS (Morris et al, 2005;Carlson et al, 2009;Treusch et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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Phytoplankton distribution patterns in the northwestern Sargasso Sea revealed by small subunit rRNA genes from plastids

et al. 2011

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Phytoplankton species vary in their physiological properties, and are expected to respond differently to seasonal changes in water column conditions. To assess these varying distribution patterns, we used 412 samples collected monthly over 12 years (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004) at the Bermuda Atlantic Time-Series Study site, located in the northwestern Sargasso Sea. We measured plastid 16S ribosomal RNA gene abundances with a terminal restriction fragment length polymorphism approach and identified distribution patterns for members of the Prymnesiophyceae, Pelagophyceae, Chrysophyceae, Cryptophyceae, Bacillariophyceae and Prasinophyceae. The analysis revealed dynamic bloom patterns by these phytoplankton taxa that begin early in the year, when the mixed layer is deep. Previously, unreported open-ocean prasinophyte blooms dominated the plastid gene signal during convective mixing events. Quantitative PCR confirmed the blooms and transitions of Bathycoccus, Micromonas and Ostreococcus populations. In contrast, taxa belonging to the pelagophytes and chrysophytes, as well as cryptophytes, reached annual peaks during mixed layer shoaling, while Bacillariophyceae (diatoms) were observed only episodically in the 12-year record. Prymnesiophytes dominated the integrated plastid gene signal. They were abundant throughout the water column before mixing events, but persisted in the deep chlorophyll maximum during stratified conditions. Various models have been used to describe mechanisms that drive vernal phytoplankton blooms in temperate seas. The range of taxon-specific bloom patterns observed here indicates that different 'spring bloom' models can aptly describe the behavior of different phytoplankton taxa at a single geographical location. These findings provide insight into the subdivision of niche space by phytoplankton and may lead to improved predictions of phytoplankton responses to changes in ocean conditions.

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Identification Of Plastid Peaks In T-rflp Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phytoplankton distribution patterns in the northwestern Sargasso Sea revealed by small subunit rRNA genes from plastids

et al. 2011

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Long‐term variability of phytoplankton carbon biomass in the Sargasso Sea

Wallhead

Garçon

Casey

et al. 2014

Global Biogeochemical Cycles

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Time series of phytoplankton carbon biomass are scarce yet may provide important insights into ocean productivity and carbon export to depth via the oceanic biological pump. We combine recent flow-cytometric measurements with pigment concentrations and other standard measurements to reconstruct taxon-specific phytoplankton carbon biomass in the Sargasso Sea over 22 years, using a multiple regression approach. The reconstructed series reveal an increasing trend (~3% per year) in total phytoplankton carbon, apparently driven by increasing nutrient supply by vertical mixing associated with a shift to a negative phase in the winter North Atlantic Oscillation index. Also, the reconstructed eukaryote biomass fraction shows a multiannual shift from~45% in the early 1990s/late 2000s to~70% in the late 1990s/early 2000s. We hypothesize that a multiannual shift in the seasonal pattern of mixing may have stimulated and restructured the eukaryote community while suppressing prokaryote populations by increasing photodamage and grazing mortality.

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Decoupling of net community and export production on submesoscales in the Sargasso Sea

Estapa

Siegel

Buesseler

et al. 2015

Global Biogeochemical Cycles

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Determinations of the net community production (NCP) in the upper ocean and the particle export production (EP) should balance over long time and large spatial scales. However, recent modeling studies suggest that a horizontal decoupling of flux-regulating processes on submesoscales (≤10 km) could lead to imbalances between individual determinations of NCP and EP. Here we sampled mixed-layer biogeochemical parameters and proxies for NCP and EP during 10, high-spatial resolution (~2 km) surface transects across strong physical gradients in the Sargasso Sea. We observed strong biogeochemical and carbon flux variability in nearly all transects. Spatial coherence among measured biogeochemical parameters within transects was common but rarely did the same parameters covary consistently across transects. Spatial variability was greater in parameters associated with higher trophic levels, such as chlorophyll in >5.0 μm particles, and variability in EP exceeded that of NCP in nearly all cases. Within sampling transects, coincident EP and NCP determinations were uncorrelated. However, when averaged over each transect (30 to 40 km in length), we found NCP and EP to be significantly and positively correlated (R = 0.72, p = 0.04). Transect-averaged EP determinations were slightly smaller than similar NCP values (Type-II regression slope of 0.93, standard deviation = 0.32) but not significantly different from a 1:1 relationship. The results show the importance of appropriate sampling scales when deriving carbon flux budgets from upper ocean observations.

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Increased ocean carbon export in the Sargasso Sea linked to climate variability is countered by its enhanced mesopelagic attenuation

Cited by 116 publications

References 62 publications

Phytoplankton distribution patterns in the northwestern Sargasso Sea revealed by small subunit rRNA genes from plastids

Phytoplankton distribution patterns in the northwestern Sargasso Sea revealed by small subunit rRNA genes from plastids

Long‐term variability of phytoplankton carbon biomass in the Sargasso Sea

Decoupling of net community and export production on submesoscales in the Sargasso Sea

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