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Highlights •A solid knowledgebase and governance process is required to develop policies for sustainable growth of offshore aquaculture in the North Sea. •Environmental goals largely define maximum sustainable production levels. For seaweed culture this is limited to the scale of several hundred km2. •Definition of realistic ambitions is a process rather than a fixed value and greatly benefits from a ‘learning by doing’ approach.

Introduction: Attenuated total reflection (ATR)–Fourier transform infrared (FTIR) analysis is a rapid tool and represents a snapshot of all molecules present in a (plant) sample. Most alternative techniques for biochemical analyses of plant biomass require destructive sampling, complex and laborious sample pre-treatment, and precise and costly analysis. These analyses are often limited to soluble compounds instead of all compounds present. Such complicated procedures are not efficient for manipulative studies that involve repeated sampling and rapid nutrient changes over time, such as in agro-industrial cultivation studies.Methods: In our study, the green seaweed species Ulva laetevirens (Chlorophyta) was cultivated under different nutritional regimes in onshore cultivation tanks. The regimes were nitrogen and phosphorus repletion, nitrogen depletion, phosphorus depletion, and light limitation. Samples were taken and tested according to common laborious analysis methods to determine the biochemical composition of polysaccharides, proteins, carbon, and nitrogen. These results were compared with the potential of ATR-FTIR spectroscopy combined with multivariate analysis to allow for prediction of biomass composition.Results: Statistical analysis of the spectra showed that the samples were clustered according to the nutritional regime during the incubation of U. laetevirens. This made it possible to deduce which abiotic factors were replete or deplete during cultivation. Furthermore, partial least square regression analysis proved the most suitable method to predict carbohydrate concentration and nitrogen content present in the biomass.Discussion/conclusion: On the basis of these findings, it is concluded that ATR-FTIR spectroscopy is an efficient and rapid alternative tool for qualitative and quantitative determination of the biochemical composition of U. laetevirens that can be used in industrial cultivation setups.

Rhodomonas salina is a microalgal species, belonging to the cryptophytes, and is widely used as aquaculture feed because of its high nutritional profile and phycoerythrin content. This study investigated the effect of pH on the growth, biochemical composition, and taste of R. salina when cultivated on a semi-large scale under natural light conditions. Two tubular photobioreactors (200 L) were used for the cultivation of R. salina with sunlight as the only illumination source. Two different pH setpoints were applied, 7 and 8.5. Optimal temperature and nutrient conditions were applied, according to previous research findings. The results demonstrated that the productivity of R. salina was higher at pH 7, 0.06–0.14 gdry weight L−1 day−1, compared to pH 8.5, 0.03–0.12 gdry weight L−1 day−1. It was found that protein and total fatty acid concentrations were higher in the biomass that was produced at pH 8.5, 33.7% and 12.3% of dry weight, respectively, while at pH 7, the protein content was 31.9% and the total fatty acids 8.8% of dry weight. The phycoerythrin concentration, like protein, was higher at pH 8.5, 2.7% of dry weight, compared to pH 7, 1% of dry weight. The free amino acid and nucleotide profile of R. salina was affected by the pH, resulting in increased equivalent umami concentration at pH 7. For the sensory evaluation, an expert panel on algae flavors evaluated the effect of pH on the taste of R. salina, reporting that the biomass that was produced at pH 7 had more umami flavor than the biomass that was produced at pH 8.5, which was evaluated as more bitter.

Kelp cultivation receives increasing interest for its high-value products and ecological services, especially in Europe and North America. Before industrial kelp farming in marine ecosystems continue to scale up, evaluation of the site-wide production relative to ecological carrying capacity (CC) of the identified system is essential. For this purpose, a mechanistic kelp model was developed and applied for hypothetical numerical experiments of expanding the farming area in a Dutch coastal bay (the Eastern Scheldt), where cultivation of Saccharina latissima (sugar kelp) is emerging. The kelp model was implemented within a three-dimensional hydrodynamic–biogeochemical model to account for the environmental interactions. The model captured the seasonal growth dynamics of S. latissima, as well as its carbon and nitrogen contents measured at the Eastern Scheldt pilot sites. The model results suggest that expanding the kelp farming area to ∼1–30% of the bay (representing ∼3.4–75 kt harvest dry weight in the 350-km2 bay) had the potential to weaken the spring bloom, and thereby affected the coexisting shellfish culture in the bay. Competition between S. latissima and phytoplankton mostly occurred in late spring for nutrients (dissolved inorganic nitrogen). The ecological CC should be weighed according to these negative impacts. However, the production CC was not reached even when farming ∼30% of the Eastern Scheldt, i.e. harvesting totally 75 kt dry mass, given that the simulated overall S. latissima production kept increasing with the farming activity. Our modelling approach can be applied to other systems for S. latissima cultivation and assist in assessing CC and environmental impacts.

Cultivation of Saccharina latissima, a brown macroalga, is fast developing in Europe and North America for the sustainable production of food and biorefinery materials and important ecosystem services. Prior studies have demonstrated large spatial variability in the yield and chemical composition of the cultivated S. latissima, even within a small coastal bay. Using a validated hydrodynamic-biogeochemical-kelpmodel, this study examined main drivers of the spatial variability in S. latissima growth dynamics in 40 hypothetical farms throughout a Dutch coastal bay, the Eastern Scheldt. Results indicate that temperatureplays a primary role in driving the spatial variability. For example, S. latissima yield in the deeper and better flushed western part is more than double that in the eastern part, mainly due to its 2–3°C warmer seawater in winter. It is also found that S. latissima benefits from co-cultivation with shellfish, since nutrients excreted by shellfish replenish its nitrogen reserve, which fuels a relatively high growth rate in the nitrogen-depleted late spring. The model assessment offers insight into optimal potential locations of S. latissima farms in the Eastern Scheldt. Applicability of our modelling approach to other coastal ecosystems and possible further improvements for assisting in seaweed farming practice are discussed.

Southern Ocean phytoplankton are especially subjected to pronounced seasonal and interannual changes in light availability. Although previous studies have examined the role of light in these environments, very few combined pigment-based taxonomy with flow cytometry to better discriminate the light response of various phytoplankton groups. In particular the different populations within the diverse and important taxonomic group of diatoms require further investigation. Six incubation experiments (9–10 days) were performed during the main productive period with naturalseawater collected at the Western Antarctic Peninsula. Standing stock of Phaeocystis spp. cells displayed relatively fast accumulation under all levels of light (low, medium, high; 4–7, 30–50 and 150–200 µmol quanta m−2 s−1), whilst the small- and larger-sized diatom populations (4.5 and 20 µm diameter) exhibited faster accumulation in medium and high light. In contrast, intermediate-sized diatoms (11.5 µm diameter) displayed fastest net growth under low light, subsequently dominating the phytoplankton community. Low light was a key factor limiting accumulation and peak phytoplankton biomass, except one incubation displaying relatively high accumulation rates under low light. The 3-week low-light period prior to experimentation likely allowed adaptation to maximize achievable growth and seems a strong determinant of whether the different natural Antarctic phytoplankton populations sustain, thrive or decline. Our study provides improved insight into how light intensity modulates the net response of key Antarctic phytoplankton, both between and within taxonomic groups.

Multiannual delayed gametophyte cultures can stay vegetative for years, while also having the ability to grow. This study aims to investigate whether male and female multiannual delayed gametophyte strains of the species Saccharina latissima and Alaria esculenta grow at different rates in culture. We furthermore assessed how changing sex ratios can affect the reproductive yields of these cultures. The results indicate that the reproductive yield of cultures declines with decreasing male:female ratios, a correlation that becomes especially apparent at higher culture densities for both species. Female gametophyte densities inparticular affected the observed reproductive yield of the cultures, with S. latissima cultures showing a clear reproductive optimum (sporophytes·mL−1) at 0.013 mg·mL−1 DW femalegametophyte biomass, while the reproductive success of A. esculenta peaked at a density of 0.025 mg·mL−1 DW of female gametophyte biomass, after which the reproductive yield started to decline in both species. The results show that the sex ratio of a gametophyte culture is an important biotic life cycle control, with higher amounts of female gametophyte biomass halting gametophyte reproduction. Understanding how these changing sex ratios in gametophyte cultures affect reproduction is especially important in the aquaculture of kelp, where reliable preforming cultures are key to long-term success.

The cryptophyte Rhodomonas salina is widely used in aquaculture due to its high nutritional profile. This study aims to investigate the effect of salinity and pH on the growth, phycoerythrin concentrations, andconcentrations of non-volatile umami taste active compounds ofR. salina, using a design of experiment approach. Rhodomonas salina was cultivated in a flat-panel photobioreactor in turbidostat mode in a range of salinity (20–40 ‰) and pH (6.5–8.5). The strain was able to grow steadily under all conditions, but the optimal productivity of 1.17 g dry weight L−1 day−1 was observed in salinity 30 ‰ and pH 7.5. The phycoerythrin concentration was inversely related to productivity, presenting higher values in conditions that were not optimal for the growth of R. salina, 7% of dry weightat salinity 40 ‰, and pH 8.5. The identification of the umami taste of R. salina was based on the synergistic effect of umami compounds 5′-nucleotides (adenosine 5′-monophosphate, guanosine 5′-monophosphate, inosine 5′-monophosphate) and free amino acids (glutamic and aspartic acids), using the equivalent umami concentration (EUC). The results indicated that an increase in pH induces the accumulation of 5′-nucleotides, resulting in an EUC of 234 mg MSG g−1 at asalinity of 40 and pH 8.5. The EUC values that were observed in R. salina were higher compared to other aquatic animals, a fact that makes R. salina promising for further research and application in the food and feed sectors.

Seaweed phytosterols are associated with potential health benefits, affording them and the seaweeds that produce them commercial interest. However, little is known about how their production is affected by the cultivation environment, limiting the efficiency with which these compounds can be exploited. Therefore, we performed a pilot study on the effect ofnutrient availability and light stress on the sterol content of Saccharina latissima, a rapid growing brown alga of increasing interest in western mariculture. Individuals of S. latissima were subjected to a nutrient-replete and nutrient-depleted regime for 5 weeks, followed by the introduction of light-limited and light-saturated conditions in the sixth week; sampling occurred each week. No significant inter-treatment differences were found in the sterol content in week 1–5. However, significant intra-treatment differences were found in weeks 3–5 regardless of nutrient treatment, wherein the fucosterol, 24-methylenecholesterol, and squalene contents of both treatment groups were found to correlate inversely with photosynthetic performance. Factorial treatment of differential nutrient availability and light stress resulted in marked differences between the sterol content of all groups in week 6. Here, squalene and cycloartenol increased in concentration with increasing irradiance regardless of nutrient treatment. Concentrations of all other sterolic components increased with increasing irradiance and low nutrient conditions while decreasing or remaining unchanged with increasing irradiance and high nutrient conditions. Our data shows that within ourcultivation conditions and time frame, the sterol content of S. latissima is unaffected by nutrient availability alone but changes with combined alterations in irradiance and nutrient availability.

The seaweed industry is growing worldwide to meet future resource needs in terms of food and fuel. In the meantime, the impact of expanding off-bottom seaweed cultivation on its environment is unclear. For example, it remains poorly understood how off-bottom seaweeds affect the local hydrodynamic environment, especially concerning turbulence that is more important for nutrient transport and availability than the mean flow velocity. Here, we carried out well-controlled flume experiments with mimic seaweed thalli, which are available, controllable, and stable, to investigate the impact of off-bottom seaweed canopies on whole-depth flow velocities in terms of both mean flow and turbulence velocity profiles. A careful comparison of behavior in the flow between natural and mimic seaweed thalli was made before these experiments. The results show that the floating seaweed thalli generate a surface boundary layer and have a profound impact on the velocity structure in the bottom boundary layer. More importantly, the generation, growth and dissipation of turbulence in the seaweed thalli area deeply affect the downstream distribution of near-bed turbulent strength and associated bed shear stress. Ignoring this turbulent variation would cause inaccurate predictions of morphological changes of the seabed. Our findings suggest that expanding the seaweed cultivation area may cause high risks of bed degradation and low diffusion in the downstream cultivation area. These findings provide novel insights into the environmental influence of off-bottom seaweed cultivation, with important implications for optimizing management strategies to promote seaweed productivity while minimizing seabed destabilization.

Uptake dynamics of dissolved inorganic phosphate (DIP) and dissolved inorganic nitrate (DIN) in young Palmaria palmata (n = 49), cultivated in a range of DIP concentrations (0.0–6.0 µmol · L−1) and nonlimiting DIN concentration (50 µmol · L−1) under fully controlled laboratory conditions, were quantified in a ‘pulse‐and‐chase’ approach over 5 weeks. Two different uptake rates were specified: (1) surge uptake (VS) after starvation and (2) maintenance uptake with filled nutrient pools (VM). VS for DIP of 1.57 ± 0.29 µmol · cm−2 · d−1 and DIN of 15.6 ± 4.3 µmol · cm−2 · d−1 , as well as VM for DIP of 0.57 ± 0.22 µmol · cm−2 · d−1 and DIN of 5.6 ± 2.1 µmol · cm−2 · d−1 were calculated. In addition, an absolute size of the internal storage capacity (ISC) for DIP of 22 µmol · cm2 and DIN of 222 µmol · cm2 was determined. A DIP‐to‐DIN uptake ratio of 1:10 under VM showed a weekly rhythmic uptake pattern, highlighted by a high correlation between DIP and DIN uptake (R = 0.943). VS for DIN did not occur under DIP depletion, but uptake rates increased with increasing DIP availability. Hence, DIP availability limited access to DIN, which was also reflected by total dissolvable protein concentrations in sporophytes, which ranged from 10.2 ± 2.5% to 24.6 ± 8.0% dry weight depending on DIP availability. Similarly, total dissolvable carbohydrate concentration ranged from 22.1 ± 3.6% to 54.3 ± 12.3% dry weight. The data presented in this study open further insight into ecological and physiological aspects of nutrient availability in P. palmata and allow for an optimization in cultivation.

Coastal ecosystems are increasingly threatened by global change. Insight in their resilience against increased storminess is needed for their application in nature‐based coastal defense schemes. This is often gained from flume experiments. Laboratory flumes provide excellent hydrodynamic control, but are restrictive in that it is extremely difficult to experiment on ecosystems with a naturally developed stability. Field flumes resolve the latter, but are limited to unidirectional currents. This study introduces an easily deployable field flume that mimics the near‐bed water motion of waves: the Tidal Dynamics WAVE flume (the TiDyWAVE). The hydrodynamics of the TiDyWAVE are assessed and compared to natural waves. We also compare it with a more traditional unidirectional flow channel by measuring the erodibility (ucr) of (1) bare sediments of which ucr can be calculated and (2) a seagrass meadow. The TiDyWAVE can generate peak oscillatory currents up to 0.32 m s−1 with a maximum wave period of 3.5 s, corresponding to 0.42 m high waves for a water depth of 3 m. ucr measurements showed that bed shear stress in the TiDyWAVE mimics field waves well. In accordance with theory, the observed ucr on bare sediment is consistently lower for oscillatory flow compared to unidirectional currents. On Thalassia testudinum, ucr under unidirectional currents increases 3.5 times faster with increasing blade area than under oscillatory flow. The difference in hydrodynamic sheltering of the seabed by flexible vegetation under currents vs. waves emphasizes the need for imposing representative hydrodynamics to study hydrodynamic thresholds of coastal ecosystems.

Heme is the iron-containing prosthetic group of hemoproteins, and is thus required for photosynthesis, respiration and nitrate reduction in marine phytoplankton. Here we report concentrations of heme b in Southern Ocean phytoplankton and contrast our findings with those in coastal species. The concentration of particulate heme b (pmol l-1) observed at the end of the exponential growth phase was related to the concentration of dissolved iron in the culture media. Small Southern Ocean phytoplankton species (<6 µm in diameter) had heme b quotas <1 µmol mol-1 carbon, the lowest yet reported for marine phytoplankton. Heme b was also depleted in these species with respect to chlorophyll a. We calculated the amount of carbon accumulated per mole of heme b per second in our cultures (heme growth efficiency, HGE) and found that small Southern Ocean species can maintain growth rates, even while heme b content is reduced. Small Southern Ocean phytoplankton can thus produce more particulate carbon than larger Southern Ocean or small coastal species at equivalent iron concentrations. Combining primary productivity and heme b concentrations reported for the open ocean, we found that HGE in natural populations was within the range of our laboratory culture results. HGE was also observed to be higher at open ocean stations characterized by low iron concentrations. Our results suggest that low heme b quotas do not necessarily result in reduced growth and that marine phytoplankton can optimize iron use by manipulating the intracellular hemoprotein pool.

The oceans play a pivotal role in the global carbon cycle. It is not practical to measure the global daily production of organic carbon, the product of phytoplankton standing stock and its growth rate using discrete oceanographic methods. Instead, optical proxies from Earth-orbiting satellites must be used. To test the accuracy of optically derived proxies of phytoplankton physiology and growth rate, hyperspectral reflectance data from the wax and wane of a Phaeocystis bloom in laboratory mesocosms were compared with standard ex situ data. Chlorophyll biomass could be estimated accurately from reflectance using specific chlorophyll absorption algorithms. However, the conversion of chlorophyll (Chl) to carbon (C) was obscured by the non-linear increase in C : Chl under nutrient-limited growth. Although C : Chl was inversely correlated (r2 = 0.88) with the in situ fluorometric growth rate indicator Fv / Fm (Photosystem II quantum efficiency), none of them was linearly correlated to growth rate, constraining the accurate calculation of Phaeocystis growth or production rates. Unfortunately, the optical proxy ?ph (quantum efficiency of fluorescence: the ratio of the number of fluoresced photons to the number of photons absorbed by the phytoplankton) did not show any correlation with Phaeocystis growth rate, and therefore it is concluded that ?ph cannot be applied in the remotely sensed measurement of this species' carbon production rate.

Growth and viral infection of the marine picoeukaryote Micromonas pusilla was studied under a future-ocean scenario of elevated partial CO2 (pCO(2); 750 mu atm versus the present-day 370 mu atm) and simultaneous limitation of phosphorus (P). Independent of the pCO(2) level, the ratios of M. pusilla cellular carbon (C) to nitrogen (N), C: P and N: P, increased with increasing P stress. Furthermore, in the P-limited chemostats at growth rates of 0.32 and 0.97 of the maximum growth rate (mu(max)), the supply of elevated pCO(2) led to an additional rise in cellular C: N and C: P ratios, as well as a 1.4-fold increase in M. pusilla abundance. Viral lysis was not affected by pCO(2), but P limitation led to a 150% prolongation of the latent period (6 to 12 h) and an 80% reduction in viral burst sizes (63 viruses per cell) compared to P-replete conditions (4 to 8 h latent period and burst size of 320). Growth at 0.32 mu(max) further prolonged the latent period by another 150% (12 to 18 h). Thus, enhanced P stress due to climate change-induced strengthened vertical stratification can be expected to lead to reduced and delayed virus production in picoeukaryotes. This effect is tempered, but likely not counteracted, by the increase in cell abundance under elevated pCO(2). Although the influence of potential P-limitation-relieving factors, such as the uptake of organic P and P utilization during infection, is unclear, our current results suggest that when P limitation prevails in future oceans, picoeukaryotes and grazing will be favored over larger-sized phytoplankton and viral lysis, with increased matter and nutrient flow to higher trophic levels.

Relationships between sea surface temperature (SST, > 10 m) and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and chlorophyll a (Chl a) specific absorption were assessed in spring and summer from latitudes 29 to 63 degrees N in the northeast Atlantic Ocean. The goal of this study was to identify relationships between phytoplankton and abiotic factors in an existing SST and stratification gradient. Furthermore, a bio-optical model was used to estimate productivity for five phytoplankton groups. Nutrient concentration (integrated from 0 to 125 m) was inversely correlated with SST in spring and summer. SST was also inversely correlated with near-surface (0-50 m) Chl a and productivity for stratified stations. Near-surface Chl a and productivity showed exponential relationships with SST. Chl a specific absorption and excess light experiments indicated photoacclimation to lower irradiance in spring as compared to summer. In addition, Chl a specific absorption suggested that phytoplankton size decreased in summer. The contribution of cyanobacteria to water column productivity of stratified stations correlated positively with SST and inversely with nutrient concentration. This suggests that a rise in SST (over a 13-23 degrees C range) stimulates productivity by cyanobacteria at the expense of haptophytes, which showed an inverse relationship to SST. At higher latitudes, where rising SST may prolong the stratified season, haptophyte productivity may expand at the expense of diatom productivity. Depth-integrated Chl a (0-410 m) was greatest in the spring at higher latitudes, where stratification in the upper 200m was weakest. This suggests that stronger stratification does not necessarily result in higher phytoplankton biomass standing stock in this region.

Relationships between sea surface temperature (SST, > 10 m) and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and chlorophyll a (Chl a) specific absorption were assessed in spring and summer from latitudes 29 to 63 N in the northeast Atlantic Ocean. The goal of this study was to identify relationships between phytoplankton and abiotic factors in an existing SST and stratification gradient. Furthermore, a bio-optical model was used to estimate productivity for five phytoplankton groups. Nutrient concentration (integrated from 0 to 125 m) was inversely correlated with SST in spring and summer. SST was also inversely correlated with near-surface (0-50 m) Chl a and productivity for stratified stations. Near-surface Chl a and productivity showed exponential relationships with SST. Chl a specific absorption and excess light experiments indicated photoacclimation to lower irradiance in spring as compared to summer. In addition, Chl a specific absorption suggested that phytoplankton size decreased in summer. The contribution of cyanobacteria to water column productivity of stratified stations correlated positively with SST and inversely with nutrient concentration. This suggests that a rise in SST (over a 13-23 C range) stimulates productivity by cyanobacteria at the expense of haptophytes, which showed an inverse relationship to SST. At higher latitudes, where rising SST may prolong the stratified season, haptophyte productivity may expand at the expense of diatom productivity. Depth-integrated Chl a (0-410 m) was greatest in the spring at higher latitudes, where stratification in the upper 200 m was weakest. This suggests that stronger stratification does not necessarily result in higher phytoplankton biomass standing stock in this region. © Author(s) 2013.

Phaeocystis globosa (Prymnesiophyceae) is an ecologically dominating phytoplankton species in many areas around the world. It plays an important role in both the global sulfur and carbon cycles, by the production of dimethylsulfide (DMS) and the drawdown of inorganic carbon. Phaeocystis globosa has a polymorphic life cycle and is considered to be a harmful algal bloom (HAB) forming species. All these aspects make this an interesting species to study the effects of increasing carbon dioxide (CO2) concentrations, due to anthropogenic carbon emissions. Here, the combined effects of three different dissolved carbon dioxide concentrations (CO2(aq)) (low: 4 mu mol kg(-1), intermediate: 6-10 mu mol kg(-1) and high CO2(aq): 21-24 mu mol kg(-1)) and two different light intensities (low light, suboptimal: 80 mu mol photons m(-2) s(-1) and high light, light saturated: 240 mu mol photons m(-2) s(-1)) are reported. The experiments demonstrated that the specific growth rate of P. globosa in the high light cultures decreased with increasing CO2(aq) from 1.4 to 1.1 d(-1) in the low and high CO2 cultures, respectively. Concurrently, the photosynthetic efficiency (F-V/F-M) increased with increasing CO2(aq) from 0.56 to 0.66. The different light conditions affected photosynthetic efficiency and cellular chlorophyll a concentrations, both of which were lower in the high light cultures as compared to the low light cultures. These results suggest that in future inorganic carbon enriched oceans, P. globosa will become less competitive and feedback mechanisms to global change may decrease in strength.

Applied Sciences

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Comparison of eight iron experiments shows that maximum Chl a, the maximum DIC removal, and the overall DIC/ Fe efficiency all scale inversely with depth of the wind mixed layer (WML) defining the light environment. Moreover, lateral patch dilution, sea surface irradiance, temperature, and grazing play additional roles. The Southern Ocean experiments were most influenced by very deep WMLs. In contrast, light conditions were most favorable during SEEDS and SERIES as well as during IronEx-2. The two extreme experiments, EisenEx and SEEDS, can be linked via EisenEx bottle incubations with shallower simulated WML depth. Large diatoms always benefit the most from Fe addition, where a remarkably small group of thriving diatom species is dominated by universal response of Pseudo-nitzschia spp. Significant response of these moderate ( 10 - 30 mu m), medium ( 30 - 60 mu m), and large (> 60 mu m) diatoms is consistent with growth physiology determined for single species in natural seawater. The minimum level of "dissolved'' Fe ( filtrate < 0.2 mu m) maintained during an experiment determines the dominant diatom size class. However, this is further complicated by continuous transfer of original truly dissolved reduced Fe(II) into the colloidal pool, which may constitute some 75% of the "dissolved'' pool. Depth integration of carbon inventory changes partly compensates the adverse effects of a deep WML due to its greater integration depths, decreasing the differences in responses between the eight experiments. About half of depth-integrated overall primary productivity is reflected in a decrease of DIC. The overall C/Fe efficiency of DIC uptake is DIC/Fe similar to 5600 for all eight experiments. The increase of particulate organic carbon is about a quarter of the primary production, suggesting food web losses for the other three quarters. Replenishment of DIC by air/sea exchange tends to be a minor few percent of primary CO2 fixation but will continue well after observations h, info:eu-repo/semantics/published

FLWIN, info:eu-repo/semantics/published

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