Phytoplankton production by remote sensing in the region off Cabo Corrientes, Mexico

Integrated total phytoplankton production (PPmod) (grams of carbon per square meter per day, gC m-2 d-1) was calculated for the oceanic region off Cabo Corrientes, Mexico. This was done with semi-analytic models from the literature and using chlorophyll a concentrations (Chlsat) and photosynthetically active radiation (PARsat) from monthly composites of the satellite sensor SeaWIFS, for May and November 2002, and June 2003. Average values for PPmod had a seasonal variation for the inshore (1.50 and 0.70 gC m-2 d-1 for May and June, and 0.38 for November) and the offshore (0.55 and 0.41 gC m-2 d-1 for May and June, and 0.31 for November) zones. It is interesting to note that our PPmod data are similar to the previously reported PP14C values for the Cabo Corrientes region. In general, Chlsat and PPmod support the previously reported ship data, which showed intense upwelling conditions during May, an upwelling relaxation period in June, and non-upwelling in November. Estimated PPmod values are within the range of those for other upwelling enriched ecosystems of the Pacific off Mexico

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

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

Phytoplankton properties at the studied regions.

<p>Mean (± standard deviation) surface values of chlorophyll <i>a</i> concentration (Chl <i>a</i>, mg m⁻³), phytoplankton carbon biomass (Phyto C, mgC m⁻³), phytoplankton carbon to chlorophyll <i>a</i> ratio (C:Chl <i>a</i>), and rate of primary production (P, mgC m⁻³ d⁻¹) in each location. <i>n</i> is the number of stations visited at each location.</p

Phytoplankton chlorophyll <i>a</i>, biomass and production.

<p>Scatterplots showing the log-log relationship between (a) primary production and phytoplankton carbon biomass, (b) primary production and chlorophyll <i>a</i> concentration and (c) phytoplankton carbon biomass and chlorophyll <i>a</i> concentration. Different symbols indicate the sampling region as defined in the Methods section. ‘Soiree In’ and ‘Soiree Out’ refer to stations located inside and outside, respectively, the iron-fertilized patch during the Soiree study. Data were fitted to a linear model using reduced major axis regression.</p

Temperature and phytoplankton growth.

<p>Carbon-specific production rate (P^C) plotted against temperature for all stations. Symbols as in Fig. 2.</p

Primary production using ¹⁴C method in subtropical gyres regions

Seawater was sampled from five depths in the euphotic zone corresponding to 100 % (ca. 3 m depth), 50 %, 20 %, 7 % and 1 % of incident Photosynthetically Active Radiation (PAR). For each depth, four 72 mL polystyrene bottles (three clear bottles and one dark bottle) were filled with unfiltered seawater, inoculated with 10 - 20 µCi NaH¹⁴CO₃ and incubated on-deck from dawn to dusk. Temperature and irradiance in the incubators simulated the water temperature and the incident irradiance at the corresponding depth of each sample by using a combination of neutral density and blue filters (Mist Blue, ref. 061, Lee Filters ®). After incubation, samples from three of the five depths (100 %, 20 % and 1 % PAR) were sequentially filtered through 20, 2 and 0.2 µm polycarbonate filters while the other depths (50 % and 7 % PAR) were directly filtered by 0.2 µm. Immediately after filtering, filters were then exposed to concentrated HCl fumes at least 12 h to remove the non-fixed inorganic ¹⁴C. Filters were placed in scintillation vials to which 5 mL of liquid scintillation cocktail was added. The radioactivity on each filter (disintegrations per minute, DPM) was determined using a Wallac scintillation counter. To compute the rate of photosynthetic carbon fixation, the dark-bottle DPM was subtracted from the light-bottle DPM values. A constant value of 24,720 µg L-1 (or 2,060 µmol L-1) was assumed for the concentration of dissolved inorganic carbon for surface waters in tropical ocean (Key et al., 2004). A correction factor of 1.05 was applied to this constant value for discrimination isotopic. Total primary production was calculated as the sum of the primary production on each size class

Distribution of transparent exopolymer particles (TEP) in distinct regions of the Southern Ocean

13 pages, 7 figures, 2 tables, supplementary data https://doi.org/10.1016/j.scitotenv.2019.06.524Transparent exopolymer particles (TEP) are an abundant class of suspended organic particles, mainly formed by polysaccharides, which play important roles in biogeochemical and ecological processes in the ocean. In this study we investigated horizontal and vertical TEP distributions (within the euphotic layer, including the upper surface) and their short-term variability along with a suite of environmental and biological variables in four distinct regions of the Southern Ocean. TEP concentrations in the surface (4 m) averaged 102.3 ± 40.4 μg XG eq. L and typically decreased with depth. Chlorophyll a (Chl a) concentration was a better predictor of TEP variability across the horizontal (R = 0.66, p < 0.001) and vertical (R = 0.74, p < 0.001) scales than prokaryotic heterotrophic abundance and production. Incubation experiments further confirmed the main role of phytoplankton as TEP producers. The highest surface TEP concentrations were found north of the South Orkney Islands (144.4 ± 21.7 μg XG eq. L), where the phytoplankton was dominated by cryptophytes and haptophytes; however, the highest TEP:Chl a ratios were found south of these islands (153.4 ± 29.8 μg XG eq (μg Chl a), compared to a mean of 79.3 ± 54.9 μg XG eq (μg Chl a) in the whole cruise, in association with haptophyte dominance, proximity of sea ice and high exposure to solar radiation. TEP were generally enriched in the upper surface (10 cm) respect to 4 m, despite a lack of biomass enrichment, suggesting either upward transport by positive buoyancy or bubble scavenging, or higher production at the upper surface by light stress or aggregation. TEP concentrations did not present any significant cyclic diel pattern. Altogether, our results suggest that photobiological stress, sea ice melt and turbulence add to phytoplankton productivity in driving TEP distribution across the Antarctic Peninsula area and Atlantic sector of the Southern OceanThis research was supported by the Spanish Ministry of Economy and Competitiveness through projects PEGASO (CTM2012-37615) and BIOGAPS (CTM2016-81008-R) to RS. MZ was supported by a FPU predoctoral fellowship (FPU13/04630) from the Spanish Ministry of Education and CulturePeer Reviewe

Stable Isotope (δ13C, δ15N, δ18O,δD) composition and nutrient concentration of Red Sea primary producers

Data of stable isotope composition (δ13C, δ15N, δD, δ18O) and nutrient concentration (%N and %C) of primary producers (halophytes, macroalgae, mangroves, seagrasses, and seston) in the Red Se