Coccolithophore calcification is independent of carbonate chemistry in the tropical ocean

Marañón, Emilio ... et al.-- 13 pages, 7 figures, 1 table, supporting information https://dx.doi.org/10.1002/lno.10295Short-term experiments indicate that seawater acidification can cause a decrease in the rate of calcification by coccolithophores, but the relationship between carbonate chemistry and coccolithophore calcification rate in natural assemblages is still unclear. During the Malaspina 2010 circumnavigation, we measured primary production, calcification, coccolithophore abundance, particulate inorganic carbon (PIC) concentration, and the parameters of the carbonate system, along basin-scale transects in the tropical Atlantic, Indian and Pacific oceans. Euphotic layer-integrated calcification and mean cell-specific calcification in the euphotic layer ranged between 2–10 mgC m−2 d−1 and 5–20 pgC cell−1 d−1, respectively. We found a significant relationship between primary production and calcification, such that the calcification to primary production (CP/PP) ratio was relatively invariant among ocean basins, with an overall mean value of 0.05 ± 0.04. Extrapolating this value to the entire ocean would result in a global pelagic calcification rate of 2.4 PtC yr−1. The mean PIC concentration in surface waters was 1.8 ± 1.6 mgC m−3 and its turnover time averaged 20 d. We combined our data of calcification, primary production, and carbonate chemistry from Malaspina 2010 with those obtained during two previous cruises in the northern Arabian Sea. Both the CP/PP ratio and cell-specific calcification were largely constant across a wide range of calcite saturation state (1.5–6.5), [ inline image]/[H+] (0.08–0.24; mol: μmol), and pH (7.6–8.1), which indicates that calcification by natural coccolithophore assemblages was independent of carbonate chemistry. Our results suggest that coccolithophore calcification, at least in tropical regions, may not be decreasing in the currently acidifying oceanFunding for this study was provided by the Spanish Ministry of Science and Innovation through research projects Malaspina 2010 (grant no. CSD2008-00077), PERSEO (CTM2007-28925-E/MAR), MANIFEST (CTM2012-32017) and TERRIFIC (CTM2014-53582-R). Funding for W.M.B. came from the NSF (OCE-0961660; OCE1220068), NASA (NNX11AO72G; NNX11AL93G; NNX14AQ41G; NNX14AQ43A; NNX14AL92G; NNX14AM77G) and NOAA (NA11OAR4310055).Peer Reviewe

Export and turnover of transparent exopolymer particles into the deep ocean

2nd Meeting of the Iberian Ecological Society (SIBECOL), XXI conference of the Iberian Association of Limnology (AIL) and 21st National Congress of the Portuguese Ecological Society (SPECO), 3-8 July 2022, AveiroAcidic polysaccharides released by phytoplankton and prokaryotic heterotrophs promote the formation of gel-like transparent exopolymer particles (TEPs). TEPs play a key role in the biological carbon pump due to their carbon-rich composition and their ability to coagulate and sink towards the deep ocean. Yet, very little is known about TEP distribution, export, and turnover at a global scale, particularly at deep ocean depths. We provide the first inventory of TEP from the surface up to 4000 m depth in the Atlantic, Indian, and Pacific Oceans and have assessed their contribution to carbon export into the deep ocean. Primary production determines TEP concentration above the deep chlorophyll maximum, and prokaryotic biomass also contributes in deeper waters. In the deep ocean waters, TEP concentrations are lower and mirror the concentrations in the surface, evidencing the importance of TEP sinking both at the export depth (200 m) with a global value of 2.9 Pg C year-1 and at the sequestration depth (1000 m) of 0.9 Pg C year-1 of particulate carbon. However, incubation experiments across ocean basins depicted rapid TEP turnover rates of 71 and 333 days (on average) within the export and sequestration depths, respectively. These findings reveal that the export of carbon by TEP sinking towards deep oceans escapes from long-term paths of the global carbon cycleN

A global compilation of coccolithophore calcification rates

The biological production of calcium carbonate (CaCO3), a process termed calcification, is a key term in the marine carbon cycle. A major planktonic group responsible for such pelagic CaCO3 production (CP) is the coccolithophores, single-celled haptophytes that inhabit the euphotic zone of the ocean. Satellite-based estimates of areal CP are limited to surface waters and open-ocean areas, with current algorithms utilising the unique optical properties of the cosmopolitan bloom-forming species Emiliania huxleyi, whereas little understanding of deep-water ecology, optical properties or environmental responses by species other than E. huxleyi is currently available to parameterise algorithms or models. To aid future areal estimations and validate future modelling efforts we have constructed a database of 2765 CP measurements, the majority of which were measured using 12 to 24 h incorporation of radioactive carbon (14C) into acid-labile inorganic carbon (CaCO3). We present data collated from over 30 studies covering the period from 1991 to 2015, sampling the Atlantic, Pacific, Indian, Arctic and Southern oceans. Globally, CP in surface waters ( < 20 m) ranged from 0.01 to 8398 µmol C m−3 d−1 (with a geometric mean of 16.1 µmol C m−3 d−1). An integral value for the upper euphotic zone (herein surface to the depth of 1 % surface irradiance) ranged from  < 0.1 to 6 mmol C m−2 d−1 (geometric mean 1.19 mmol C m−2 d−1). The full database is available for download from PANGAEA at https://doi.org/10.1594/PANGAEA.888182

Large carbon export, but short residence times, of transparent exopolymer particles in the global ocean

ASLO Aquatic Sciences Meeting 2023, Resilience and Recovery in Aquatic Systems, 4–9 June 2023, Palma de Mallorca, SpainAcidic polysaccharides released by phytoplankton and prokaryotic heterotrophs promote the formation of gel-like transparent exopolymer particles (TEPs). TEPs can have a relevant contribution to the biological carbon pump due to their carbon-rich composition and their ability to coagulate and sink towards the deep ocean. However, little is known about TEPs distribution, carbon export, and residence times below the export (200 m) and sequestration (1000 m) depths. We provide the first comprehensive inventory of TEP from the ocean surface to a depth of 4000 meters in the tropical and subtropical Atlantic, Indian, and Pacific Oceans, evaluating its contribution to carbon export and sequestration into the deep ocean. Results indicate that TEP concentration is primarily determined by primary production, with higher concentrations located above the deep chlorophyll maxima. In the deep ocean, TEP concentrations are lower yet mirror the concentrations in the surface, demonstrating the significance of TEP sinking below both the export compartment (2.8 Pg C yr-1; 27% of total POC flux at 200 m) and the sequestration compartment (0.8 Pg C yr-1; 36% of total POC flux at 1000 m). In situ incubation experiments conducted across ocean basins indicate short TEP residence times, averaging 27 and 333 days in the export and sequestration compartments, respectively. These findings reveal that the export and subsequent sequestration of carbon by TEP sinking into the deep ocean diverts it from the long times observed for the dissolved carbon fraction (i.e. centuries) in the global carbon cycleN

Resource Supply Overrides Temperature as a Controlling Factor of Marine Phytoplankton Growth

The universal temperature dependence of metabolic rates has been used to predict how ocean biology will respond to ocean warming. Determining the temperature sensitivity of phytoplankton metabolism and growth is of special importance because this group of organisms is responsible for nearly half of global primary production, sustains most marine food webs, and contributes to regulate the exchange of CO2 between the ocean and the atmosphere. Phytoplankton growth rates increase with temperature under optimal growth conditions in the laboratory, but it is unclear whether the same degree of temperature dependence exists in nature, where resources are often limiting. Here we use concurrent measurements of phytoplankton biomass and carbon fixation rates in polar, temperate and tropical regions to determine the role of temperature and resource supply in controlling the large-scale variability of in situ metabolic rates. We identify a biogeographic pattern in phytoplankton metabolic rates, which increase from the oligotrophic subtropical gyres to temperate regions and then coastal waters. Variability in phytoplankton growth is driven by changes in resource supply and appears to be independent of seawater temperature. The lack of temperature sensitivity of realized phytoplankton growth is consistent with the limited applicability of Arrhenius enzymatic kinetics when substrate concentrations are low. Our results suggest that, due to widespread resource limitation in the ocean, the direct effect of sea surface warming upon phytoplankton growth and productivity may be smaller than anticipated

How bacterioplankton is affected by the shifts in biogenic carbon flow from particulate primary production to dissolved forms

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, SpainPhotosynthesis by phytoplankton in sunlit surface waters transforms inorganic carbon and nutrients into particulate and dissolved organic matter (POC and DOC). POC can be efficiently transported downwards by the biological carbon pump whereas DOC is mostly recycled by bacteria back into dissolved inorganic forms and is the trophic link between photoautotrophs and bacteria heterotrophs. DOC production is an important part of the global primary production. There are, scarce studies that quantify its contribution in a large scale and probably does not include data from different oceans using a consistent methodology. Malaspina 2010 offers an excellent opportunity to cover the lack of knowledge regarding DOC primary production large scale variability and the degree of coupling with bacterioplankton. Simultaneously measuring DOC-14, POC14 and H-3 leucine bacterial production (within, the euphotic layer of the low-latitude Atlantic, Indian and Pacific Ocean) gave consistent results on planktonic community functioning. POC and DOC production rates tended to follow a similar vertical pattern with percent extracellular release (PER) values (42 % ± 2) not significantly different between depths. DOC and POC production rates were positively and significantly correlated with a slope significantly different than 1. On average, most of the bacterial production was sustained by DOC primary production within the euphotic layer all over the oceans. The vertical variability of DOC primary production and its degree of coupling with bacterioplankton metabolism in these largely unexplored systems will help us better understand the global oceanic carbon cyclePeer Reviewe

Multi-model remote sensing assessment of primary production in the subtropical gyres

The subtropical gyres occupy about 70% of the ocean surface. While primary production (PP) within these oligotrophic regions is relatively low, their extension makes their total contribution to ocean productivity significant. Monitoring marine pelagic primary production across broad spatial scales, particularly across the subtropical gyre regions, is challenging but essential to evaluate the oceanic carbon budget. PP in the ocean can be derived from remote sensing however in situ depth-integrated PP (IPPis) measurements required for validation are scarce from the subtropical gyres. In this study, we collected >120 IPPis measurements from both northern and southern subtropical gyres that we compared to commonly used primary productivity models (the Vertically Generalized Production Model, VGPM and six variants; the Eppley-Square-Root model, ESQRT; the Howard–Yoder–Ryan model, HYR; the model of MARRA, MARRA; and the Carbon-based Production Model, CbPM) to predict remote PP (PPr) in the subtropical regions and explored possibilities for improving PP prediction. Our results showed that satellite-derived PP (IPPsat) estimates obtained from the VGPM1, MARRA and ESQRT provided closer values to the IPPis (i.e., the difference between the mean of the IPPsat and IPPis was closer to 0; |Bias| ~ 0.09). Model performance varied due to differences in satellite predictions of in situ parameters such as chlorophyll a (chl-a) concentration or the optimal assimilation efficiency of the productivity profile (PBopt) in the subtropical region. In general, model performance was better for areas showing higher IPPis, highlighting the challenge of PP prediction in the most oligotrophic areas (i.e. PP < 300 mg C m−2 d−1). The use of in situ chl-a data, and PBopt as a function of sea surface temperature (SST) and the mixed layer depth (MLD) from gliders and floats in PPr models would improve their IPP predictions considerably in oligotrophic oceanic regions such as the subtropical gyres where MLD is relatively low (<60 m) and cloudiness may bias satellite input data

Multi-model remote sensing assessment of primary production in the subtropical gyres

The subtropical gyres occupy about 70% of the ocean surface. While primary production (PP) within these oligotrophic regions is relatively low, their extension makes their total contribution to ocean productivity significant. Monitoring marine pelagic primary production across broad spatial scales, particularly across the subtropical gyre regions, is challenging but essential to evaluate the oceanic carbon budget. PP in the ocean can be derived from remote sensing however in situ depth-integrated PP (IPPis) measurements required for validation are scarce from the subtropical gyres. In this study, we collected >120 IPPis measurements from both northern and southern subtropical gyres that we compared to commonly used primary productivity models (the Vertically Generalized Production Model, VGPM and six variants; the Eppley-Square-Root model, ESQRT; the Howard–Yoder–Ryan model, HYR; the model of MARRA, MARRA; and the Carbon-based Production Model, CbPM) to predict remote PP (PPr) in the subtropical regions and explored possibilities for improving PP prediction. Our results showed that satellite-derived PP (IPPsat) estimates obtained from the VGPM1, MARRA and ESQRT provided closer values to the IPPis (i.e., the difference between the mean of the IPPsat and IPPis was closer to 0; Bias~0.09). Model performance varied due to differences in satellite predictions of in situ parameters such as chlorophyll a (chl-a) concentration or the optimal assimilation efficiency of the productivity profile (PBopt) in the subtropical region. In general, model performance was better for areas showing higher IPPis, highlighting the challenge of PP prediction in the most oligotrophic areas (i.e. PP<300mg C m−2 d−1). The use of in situ chl-a data, and PBopt as a function of sea surface temperature (SST) and the mixed layer depth (MLD) from gliders and floats in PPr models would improve their IPP predictions considerably in oligotrophic oceanic regions such as the subtropical gyres where MLD is relatively low (<60 m) and cloudiness may bias satellite input data.Ministerio de Ciencia e Innovación | Ref. CSD2008-0007

Patterns in the response of marine microbial plankton to Saharan dust.

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Scientists Raise Alarms about Fast Tracking of Transoceanic Canal through Nicaragua

Artículo de publicación ISISeeking economic growth and job creation to tackle the nation's extreme poverty, the Nicaraguan government awarded a concession to build an interoceanic canal and associated projects to a recently formed Hong Kong based company with no track record or related expertise. This concession was awarded without a bidding process and in advance of any feasibility, socio-economic or environmental impact assessments; construction has begun without this information. The 278 km long interoceanic canal project may result in significant environmental and social impairments. Of particular concern are damage to Lake Cocibolca, a unique freshwater tropical lake and Central America's main freshwater reservoir; damage to regional biodiversity and ecosystems; and socio-economic impacts. Concerned about the possibly irreparable damage to the environment and to native communities, conservationists and the scientific community at large are urging the Nicaraguan government to devise and reveal an action plan to address and mitigate the possible negative repercussions of this interoceanic canal and associated projects. Critical research needs for preparation of a comprehensive benefit-cost analysis for this megaproject are presented