Primary Production Measurements Research Articles

Warming of alpine tundra enhances belowground production and shifts community towards resource acquisition traits

AbstractClimate warming is expected to stimulate plant growth in high‐elevation and high‐latitude ecosystems, significantly increasing aboveground net primary production (ANPP). However, the effects of simultaneous changes in temperature, snowmelt timing, and summer water availability on total net primary production (NPP)—and elucidation of both above‐ and belowground responses—remain an important area in need of further study. In particular, measures of belowground net primary productivity (BNPP) are required to understand whether ANPP changes reflect changes in allocation or are indicative of a whole plant NPP response. Further, plant functional traits provide a key way to scale from the individual plant to the community level and provide insight into drivers of NPP responses to environmental change. We used infrared heaters to warm an alpine plant community at Niwot Ridge, Colorado, and applied supplemental water to compensate for soil water loss induced by warming. We measured ANPP, BNPP, and leaf and root functional traits across treatments after 5 yr of continuous warming. Community‐level ANPP and total NPP (ANPP + BNPP) did not respond to heating or watering, but BNPP increased in response to heating. Heating decreased community‐level leaf dry matter content and increased total root length, indicating a shift in strategy from resource conservation to acquisition in response to warming. Water use efficiency (WUE) decreased with heating, suggesting alleviation of moisture constraints that may have enabled the plant community to increase productivity. Heating may have decreased WUE by melting snow earlier and creating more days early in the growing season with adequate soil moisture, but stimulated dry mass investment in roots as soils dried down later in the growing season. Overall, this study highlights how ANPP and BNPP responses to climate change can diverge, and encourages a closer examination of belowground processes, especially in alpine systems, where the majority of NPP occurs belowground.

Using chlorophyll fluorescence kinetics to determine photosynthesis in aquatic ecosystems

AbstractVariable fluorescence techniques are increasingly used to assess phytoplankton photosynthesis. All fluorescence techniques and models for photosynthetic electron transport rates (ETRs) are amplitude‐based and are subject to errors, especially when phytoplankton growth is nutrient‐limited. Here we develop a new, kinetic‐based approach to measure, directly and in absolute units, ETRs and to estimate growth rates in phytoplankton. We applied this approach to investigate the effects of nitrogen limitation on phytoplankton photophysiology and growth rates. Nutrient stress leads to a decrease in the quantum yield of photochemistry in Photosystem II (Fv/Fm); however, the relationship between Fv/Fm and growth rates is highly nonlinear, which makes it impossible to quantify the reduction in phytoplankton growth rates from Fv/Fm alone. In contrast, the decline in growth rates under nitrogen stress was proportional to the decrease in kinetic‐based photosynthetic rates. Our analysis suggests the kinetic fluorescence measurements markedly improve the accuracy of ETR measurements, as compared to classical amplitude‐based measurements. Fluorescence‐based methods for primary production rely on measurements of ETRs and then conversion to carbon fixation rates by using the electron yields of carbon fixation. The electron yields exhibit 10‐fold variability in natural phytoplankton communities and are strongly affected by nutrient limitation. Our results reveal that a decrease in the growth rates and the electron yields of carbon fixation is driven by, and can be quantified from, a decrease in photosynthetic turnover rates. We propose an algorithm to deduce the electron yields of carbon fixation, which greatly improve fluorescence‐based measurements of primary production and growth rates.

Golden Eagle Breeding Response to Utility-Scale Solar Development and Prolonged Drought in California

Each year from 2012–2016, we conducted helicopter surveys to monitor the distribution, success, and productivity of Golden Eagles (Aquila chrysaetos) breeding within 16 km of California Valley Solar Ranch (CVSR) in San Luis Obispo County, California. This 250-megawatt photovoltaic solar plant was built over 2 yr on 642 ha of disturbed grassland and desert scrub habitat on Carrizo Plain, and was operational in October 2013. Beginning in 2012 coincident with initial CVSR development, the study area and region experienced a severe drought that persisted through the end of the 2016 breeding season. During the study, we detected and monitored 19 variably occupied Golden Eagle breeding territories. We confirmed a similar number of occupied territories in 2012 (15) and 2016 (16), but our ability to reliably confirm pairs declined during the drought and shifting territory dynamics occurred in several areas. Between 2012 and 2015, the proportion of pairs that laid eggs (breeding rate) and fledgling production per occupied territory (productivity) declined by 93–95% (13 pairs laid eggs in 2012; only 1 pair did so in 2015). In 2016, the breeding rate increased sharply again to 63% of occupied territories (87% in 2012) following the return of average rainfall during the preceding winter, but the proportion of pairs that fledged young and productivity rebounded to notably lesser degrees. The eagle breeding rate and productivity trends were strongly correlated with current-year measures of primary plant productivity and rainfall totals from the previous water-year (June–July). Breeding performance metrics for five pairs with territories situated on the periphery of Carrizo Plain and 13 pairs located elsewhere in the study area away from possible development disturbance did not differ statistically. This suggested that CVSR development and initial operation did not adversely affect eagle breeding performance during the study; however, we cannot draw definitive conclusions from this 5-yr study about how CVSR development might have influenced the local eagle breeding population. Instead, we concluded that a severe 5-yr drought dramatically reduced eagle breeding activity in the study area (and region) and confounded our effort to evaluate the effects of the solar development.

Dynamics of sun‐induced chlorophyll fluorescence and reflectance to detect stress‐induced variations in canopy photosynthesis

Passive measurement of sun-induced chlorophyll fluorescence (F) represents the most promising tool to quantify changes in photosynthetic functioning on a large scale. However, the complex relationship between this signal and other photosynthesis-related processes restricts its interpretation under stress conditions. To address this issue, we conducted a field campaign by combining daily airborne and ground-based measurements of F (normalized to photosynthetically active radiation), reflectance and surface temperature and related the observed changes to stress-induced variations in photosynthesis. A lawn carpet was sprayed with different doses of the herbicide Dicuran. Canopy-level measurements of gross primary productivity indicated dosage-dependent inhibition of photosynthesis by the herbicide. Dosage-dependent changes in normalized F were also detected. After spraying, we first observed a rapid increase in normalized F and in the Photochemical Reflectance Index, possibly due to the blockage of electron transport by Dicuran and the resultant impairment of xanthophyll-mediated non-photochemical quenching. This initial increase was followed by a gradual decrease in both signals, which coincided with a decline in pigment-related reflectance indices. In parallel, we also detected a canopy temperature increase after the treatment. These results demonstrate the potential of using F coupled with relevant reflectance indices to estimate stress-induced changes in canopy photosynthesis.

Suitability analysis of aquaculture ponds based on primary productivity parameters in mangrove area of Banda Aceh

Determining the suitability of aquaculture ponds is one of a valuable factor in sustainable aquaculture. One of the factors to consider in establishing a successful aquaculture is aquatic environment, i.e.: the primary productivity of waters and physical-chemical factors. The value of primary productivity describes aquatic trophic and natural food availability. This research was aimed to observe the suitability of aquaculture ponds based on primary productivity, phytoplankton abundance, and water quality (Physical-Chemical factors). The research was conducted on July to August 2018 in mangrove ecosystem at western and eastern coastal area of Banda Aceh with six observation stations, namely Beureunut, Amat Aramanyang, Ruyung, Tibang, Deah Glumpang and Peukan Bada. These stations were determined by stratified random sampling method based on water characteristic. The measurement of primary productivity was conducted by using the dark-light bottle method. The categorizing of suitability of aquaculture ponds was done by using the scoring method. The water quality parameters were given the value and score then following to be divided into four classes of suitability comprise Class S1 (Very suitable), S2 (Suitable), S3 (Conditional Suitable), and TS (Unsuitable). The results showed that the value of primary productivity ranged from 34.72 to 178.82 mgC/m3/hour and the phytoplankton abundance around 1.17 – 3.02 individual/Liter. Land suitability scoring ranged from 70.1 – 75.6%. It was concluded that the station 4th (Tibang) and 5th (Deah Glumpang) were a suitable area for aquaculture ponds with a score of 75.6%.

Planktonic primary production in the western Dutch Wadden Sea

Pelagic primary production measurements provide fundamental information about the trophic status of a marine ecosystem. Measured carbon fixation rates generally have a limited temporal and spatial resolution, but can be combined with Earth Observation data to extrapolate the measurements. Here,P-Ecurves were fitted for 3 yr of14C incubation data from the western Wadden Sea, using 4 different models; 2 with and 2 without photo-inhibition. The curve-fit model by Jassby & Platt (1976) best fit the data. Applying this model showed that the photosynthetic parameters, normalised for chlorophyllaconcentration, of maximum production (PBmax) and initial slope of theP-Ecurve (αB) were correlated. Seasonality in photosynthetic parameters of this model and the relationship with environmental variables were explored, with a focus on variables that can be inferred from satellite algorithms. There were no significant correlations between αBand any of the environmental variables measured. WhilePBmaxcorrelated with sea surface temperature (SST), the vertical light attenuation coefficient, silicate and nitrate + nitrite concentration, the multivariate model that best explained the variation in estimates ofPBmaxwas a model that included SST and year. In the period from 2012-2014, daily and annual production ranged between 3.4 and 3800 mg C d-1and between 131 and 239 g C m-2yr-1, respectively. Comparison of these results with historical data (1990-2003) indicates that the decline in planktonic primary production that has been happening since the 1990s has halted. Although not tested, we believe that our approach is generally applicable to coastal waters.

Investigating the Nutrient Landscape in a Coastal Upwelling Region and Its Relationship to the Biological Carbon Pump

AbstractWe investigated nutrient patterns and their relationship to vertical carbon export using results from 38 Lagrangian experiments in the California Current Ecosystem. The dominant mode of variability reflected onshore‐offshore nutrient gradients. A secondary mode of variability was correlated with silica excess and dissolved iron and likely reflects regional patterns of iron limitation. The biological carbon pump was enhanced in high‐nutrient and Fe‐stressed regions. Patterns in the nutrient landscape proved to be better predictors of the vertical flux of sinking particles than contemporaneous measurements of net primary production. Our results suggest an important role for Fe‐stressed diatoms in vertical carbon flux. They also suggest that either preferential recycling of N or non‐Redfieldian nutrient uptake by diatoms may lead to high PO43−:NO3− and Si(OH)4:NO3− ratios, following export of P‐ and Si‐enriched organic matter. Increased export following Fe stress may partially explain inverse relationships between net primary productivity and export efficiency.

Direct climate effects are more influential than functional composition in determining future gross primary productivity

Most future predictions of forest diversity and composition assume species will shift instantaneously. However, evidence suggests there will be considerable inertia between climate change and shifts in plant species distributions, for example due to resident communities resisting changes, the redistribution of resident species’ abundances, and dispersal limitation of species attempting to track preferred climates. To test how inertia in community responses to climate change may affect future primary productivity, and the capacity for communities to respond through local redistribution of abundances. We assessed relationships between community functional trait distributions, climate and environment with a remote-sensed measure of gross primary productivity (GPP) across 1032 woody plant communities and projected these spatially under current and future climates. Using a simulation approach, we also tested the capacity for communities to achieve future trait distributions by shifting the relative abundances of resident species. We found that climate change is likely to reduce GPP in southeast Queensland, and, contrary to expectations, there is little evidence to suggest distributional inertia will contribute substantially to this loss. We show that sites with high existing functional diversity are well-placed to achieve predicted future trait compositions in the absence of long-distance dispersal through redistribution of resident species abundances. Our results show that sites with high existing functional diversity are well placed to achieve predicted future trait compositions in the absence of long-distance dispersal through abundance redistribution of resident species, but it is unlikely this will mitigate strong climate change-driven losses of productivity.

High Net Primary Production of Mediterranean Seagrass (Posidonia oceanica) Meadows Determined With Aquatic Eddy Covariance

We report primary production and respiration of Posidonia oceanica meadows determined with the non-invasive aquatic eddy covariance technique. Oxygen fluxes were measured in late spring at an open-water meadow (300 m from shore), at a nearshore meadow (60 m from shore), and at an adjacent sand bed. Despite the oligotrophic environment, the meadows were highly productive and highly autotrophic. Net ecosystem production (54 to 119 mmol m-2 d-1) was about one-half of gross primary production. In adjacent sands, net primary production was a tenth- to a twentieth smaller (4.6 mmol m-2 d-1). Thus, P. oceanica meadows are an oasis of productivity in unproductive surroundings. During the night, dissolved oxygen was depleted in the open-water meadow. This caused a hysteresis where oxygen production in the late afternoon was greater than in the morning at the same irradiance. Therefore, for accurate measurements of diel primary production and respiration in this system, oxygen must be measured within the canopy. Generally, these measurements demonstrate that P. oceanica meadows fix substantially more carbon than they respire. This supports the high rate of organic carbon accumulation and export for which the ecosystem is known.

Primary Production, an Index of Climate Change in the Ocean: Satellite-Based Estimates over Two Decades

Primary production by marine phytoplankton is one of the largest fluxes of carbon on our planet. In the past few decades, considerable progress has been made in estimating global primary production at high spatial and temporal scales by combining in situ measurements of primary production with remote-sensing observations of phytoplankton biomass. One of the major challenges in this approach lies in the assignment of the appropriate model parameters that define the photosynthetic response of phytoplankton to the light field. In the present study, a global database of in situ measurements of photosynthesis versus irradiance (P-I) parameters and a 20-year record of climate quality satellite observations were used to assess global primary production and its variability with seasons and locations as well as between years. In addition, the sensitivity of the computed primary production to potential changes in the photosynthetic response of phytoplankton cells under changing environmental conditions was investigated. Global annual primary production varied from 38.8 to 42.1 Gt C yr − 1 over the period of 1998–2018. Inter-annual changes in global primary production did not follow a linear trend, and regional differences in the magnitude and direction of change in primary production were observed. Trends in primary production followed directly from changes in chlorophyll-a and were related to changes in the physico-chemical conditions of the water column due to inter-annual and multidecadal climate oscillations. Moreover, the sensitivity analysis in which P-I parameters were adjusted by ±1 standard deviation showed the importance of accurately assigning photosynthetic parameters in global and regional calculations of primary production. The assimilation number of the P-I curve showed strong relationships with environmental variables such as temperature and had a practically one-to-one relationship with the magnitude of change in primary production. In the future, such empirical relationships could potentially be used for a more dynamic assignment of photosynthetic rates in the estimation of global primary production. Relationships between the initial slope of the P-I curve and environmental variables were more elusive.

Protist grazing contributes to microbial food web at the upper boundary of the twilight zone in the subarctic Pacific

Grazing by herbivorous protists (microzooplankton) is a major loss pathway of primary production in the surface ocean, yet its impact below the well-lit surface ocean is largely unknown. The upper boundary of the twilight zone is critically important to understanding carbon cycling and is often the depth of highest attenuation of particulate carbon flux. Available measurements of primary production and grazing below the well-lit surface ocean suggest that the upper boundary of the twilight zone may harbor active but poorly constrained food web processes. Previous grazing rates from the base of the euphotic zone were measured in subtropical and tropical environments. Thus, the impact of protist grazing on prey populations remains unknown in colder conditions at higher latitudes. To advance understanding and provide mechanistic insight into processes occurring at the base of the euphotic zone (0.4-0.7% PAR), we measured predation rates on both phytoplankton and heterotrophic prokaryotes in the North Pacific, using a novel method that amplified the grazing signal by concentrating the predator community, enabling detection of grazing rates far below previous limits. Protists consumed 0.6% of the phytoplankton population daily and 12% of daily heterotrophic prokaryote growth. These conservative rate measurements document marginal removal of phytoplankton even in these colder regimes, implying flows of energy from single-cell primary producers and prokaryotes to single-cell protists at rates far below previous detection limits in this twilight region of a low-productivity system.

Extending a first-principles primary production model to predict wheat yields

Climate exerts a major influence on crop development and yield. Despite extensive modelling efforts, there is still considerable uncertainty about the consequences of a changing climate for the yields of major crops. Existing crop models are complex and rely on many assumptions and parameters, motivating a quest for more parsimonious models with stronger theoretical and empirical foundations. This paper presents a prototype of such a model for wheat, informed by measurements of gross primary production (GPP), biomass and yield at research sites across the wheat-growing regions of China. First, GPP was predicted using a recently developed first-principles model driven only by climate, carbon dioxide (CO2) concentration, and light absorbed by leaves. Modelled GPP was shown to agree well with eddy-covariance measurements. Second, the data were used to show that above-ground biomass (AB) is proportional to time-integrated GPP, and that grain yield shows a saturating relationship with AB. Simple empirical equations based on these findings were combined with modelled GPP to predict yield, including propagated errors due to parameter uncertainty in both the GPP model and the empirical equations. The resulting 'hybrid' model, applied in a variety of climates, successfully predicted measured interannual variations in AB and yield. Third, the model was extended to include a phenology scheme, a mass-balance equation relating mean leaf area index to accumulated GPP over the growth phase, and an independently observed response of leaf mass-per-area to CO2. Sensitivity analyses and scenario runs with this extended model showed a positive but saturating (at ∼600 ppm) response of yield to rising CO2, consistent with experimental evidence. This positive effect was partially counteracted by a net negative response of yield to increasing temperature, caused by increasing photorespiration and an accelerated growth cycle.

Acoustic investigation of the primary production of an Australian temperate macroalgal (Ecklonia radiata) system

Temperate marine systems are dominated by rocky reef macroalgal habitats, and there is now evidence that some seaweed communities are retreating in a manner consistent with climate change. Obtaining measurements of primary production across entire assemblages of algae over ecologically meaningful spatial scales is difficult, and acoustic techniques emerge as a method to consider. Acoustics has the potential to detect oxygen in gaseous form, hence it can measure primary production that is unseen by methods that use dissolved oxygen to estimate productivity. With levels of dissolved oxygen in kelp environments regularly reaching supersaturation, it is possible – even likely – that ecologically significant proportions of production have been neglected by traditional methods. To investigate the potential use of underwater acoustics in monitoring productivity of macroalgal habitats an experiment was run over two weeks during the Austral summer in February 2012 in Canoe Bay, Tasmania. This paper details the results of ray-based acoustic predictive models for two periods during the experiment chosen to compare contrasting diurnal productivity periods, together with inverted acoustic propagation waveguide features from the empirical experiment itself for these periods. Results of the Bellhop modelling suggest that acoustic transmissions can detect ecologically significant proportions of oxygen in gaseous form in seaweed environments (>5% of total predicted production). However, changes in diurnal cycles of oxygen production were not seen in the empirical acoustic data during the experimental period, indicating that it is unlikely that there was a significant level of oxygen in gaseous form in the canopy layer. This work details the first research into the use of acoustics to measure productivity in macroalgal systems. It is possible that further research, particularly in highly productive environments or when conditions are more favourable, may prove acoustics to be a useful tool for assisting in monitoring primary productivity in seaweed communities.

Agriculture influences ammonium and soluble reactive phosphorus retention in South American headwater streams

AbstractAgricultural activities can affect the delivery of nutrients to streams, riparian canopy cover, and the capacity of aquatic systems to process nutrients and sediments. There are few measures of nutrient uptake and metabolism from tropical or subtropical streams in general, and even fewer from tropical regions of South America. We examined ammonium (NH4+) and soluble reactive phosphorus (SRP) retention in streams in Brazil and Argentina. We selected 12 streams with relatively little or extensive agricultural activity and conducted whole‐stream nutrient additions and measurements of gross primary production and ecosystem respiration. We used multiple linear regression to determine potential drivers of nutrient uptake metrics across the streams. Nutrient concentrations and retention differed significantly between land use categories. Both NH4+ and SRP concentrations were higher in the agricultural sites (means of 161 and 495 μg l–1, respectively), whereas metabolic rates were slower and transient storage was smaller. Our analysis indicated that agriculture increased ambient uptake lengths and decreased uptake velocities. The regression models revealed that ambient SRP had a positive effect on NH4+ uptake and vice versa, suggesting strong stoichiometric controls. Drivers for nutrient uptake in streams with low‐intensity agriculture also included canopy cover, temperature, and ecosystem respiration rates. Nutrient assimilation in agricultural sites was influenced by a higher number of variables (gross primary production for SRP, discharge, and transient storage for both nutrients). Our results indicate agricultural activity changes both the magnitude of in‐stream nutrient uptake and the mechanisms that control its variation, with important implications for South American streams under agricultural intensification.

Dynamic variability of the phytoplankton electron requirement for carbon fixation in eastern Australian waters

Fast Repetition Rate fluorometry (FRRf) generates high-resolution measures of phytoplankton primary productivity as electron transport rates (ETRs). How ETRs scale to corresponding inorganic carbon (C) uptake rates (the so-called electron requirement for carbon fixation, e,C), inherently describes the extent and effectiveness with which absorbed light energy drives C-fixation. However, it remains unclear whether and how e,C follows predictable patterns for oceanographic datasets spanning physically dynamic, and complex, environmental gradients. We utilise a unique high-throughput approach, coupling ETRs and 14C-incubations to produce a semi-continuous dataset of e,C (n = 80), predominantly from surface waters, along the Australian coast (Brisbane to the Tasman Sea), including the East Australian Current (EAC). Environmental conditions along this transect could be generally grouped into cooler, more nutrient-rich waters dominated by larger size-fractionated Chl-a (>10 um) versus warmer nutrient-poorer waters dominated by smaller size-fractionated Chl-a (< 2 um). Whilst e,C was higher for warmer water samples, environmental conditions alone explained less than 20% variance of e,C, and changes in predominant size-fraction(s) distributions of Chl-a (biomass) failed to explain variance of e,C. Instead, NPQNSV was a better predictor of e,C, explaining 55% of observed variability. NPQNSV is a physiological descriptor that accounts for changes in both long-term driven acclimation in non-radiative decay, and quasi-instantaneous PSII downregulation, and thus may prove a useful predictor of e,C across physically-dynamic regimes, provided the slope describing their relationship is predictable.

Uncertainties in variable fluorescence and 14C methods to estimate primary production: a case study in the coastal waters off the Korean peninsula

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 627:13-31 (2019) - DOI: https://doi.org/10.3354/meps13083 Uncertainties in variable fluorescence and 14C methods to estimate primary production: a case study in the coastal waters off the Korean peninsula Eunho Ko1,2, Jisoo Park1,2, Maxim Y. Gorbunov3, Sinjae Yoo2,4,* 1Division of Polar Ocean Environment, Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-Gu, Incheon 21990, Republic of Korea 2University of Science and Technology, 217 Gajeongh-ro, Daejeon 34113, Republic of Korea 3Department of Marine and Coastal Sciences, Rutgers University, New Brunswick, New Jersey 08901, USA 4Jeju Marine Research Section, Korea Institute of Ocean Science & Technology, 2670 lljudong-ro, Gujwa-eup, Jeju-si, Jeju-do 63349, Republic of Korea *Corresponding author: sjyoo@kiost.ac.kr ABSTRACT: To understand what controls the decoupling of photosynthetic electron transfer and carbon fixation in natural phytoplankton communities, we compared the primary production rates estimated by 14C uptake and fast repetition rate fluorometry (FRRF) in Korean waters under diverse environmental conditions. Our comparison showed that these 2 methods produce consistent results, with the FRRF method systematically yielding 1.9 times higher values than the 14C method. To quantify the potential factors that contribute to this discrepancy, we analyzed the variability in the electron requirement for carbon fixation, which showed a wide range of 5.5-71.3 mol electrons (mol CO2)-1, in relation to environmental variables. The analysis revealed that nutrient availability and the state of stratification may be the major factors that control variability in the electron requirement for carbon fixation. The strong dependence on nitrogen suggests that photosynthetic processes and phytoplankton growth are not in balance in natural communities. Based on the relationship with environmental variables, we propose a regional algorithm for the electron requirement for carbon fixation, which markedly improves FRRF-based measurements of primary production in this geographical area. KEY WORDS: Primary production · 14C · Variable fluorescence · Electron requirement for carbon fixation · Electron transfer rate · Fast repetition rate fluorometry Full text in pdf format PreviousNextCite this article as: Ko E, Park J, Gorbunov MY, Yoo S (2019) Uncertainties in variable fluorescence and 14C methods to estimate primary production: a case study in the coastal waters off the Korean peninsula. Mar Ecol Prog Ser 627:13-31. https://doi.org/10.3354/meps13083 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 627. Online publication date: September 26, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Relationship Between Carbon- and Oxygen-Based Primary Productivity in the Arctic Ocean, Svalbard Archipelago

Phytoplankton contribute half of the primary production in the biosphere and are the major source of energy for the Arctic Ocean ecosystem. While primary production measurements are therefore fundamental to our understanding of marine biogeochemical cycling, the extent to which current methods provide a definitive estimate of this process remains uncertain given differences in their underlying approaches and assumptions. This is especially the case in the Arctic Ocean, a region of the planet undergoing rapid evolution as a result of climate change, yet where primary production measurements are sparse. In this study, we compared three common methods for estimating primary production in the European Arctic Ocean: 1) production of 18O-labeled oxygen (GPP-18O), 2) changes in dissolved oxygen (GPP-DO) and 3) incorporation rates of 14C-labelled carbon into particulate organic carbon (14C-POC) and into total organic carbon (14C-TOC, the sum of dissolved and particulate organic carbon). Results show that primary production rates derived using oxygen methods showed good agreement across season and were strongly positively correlated. While also strongly correlated, higher scatter associated with seasonal changes was observed between 14C-POC and 14C-TOC. The 14C-TOC-derived rates were, on average, approximately 50 % of the oxygen-based estimates. However, the relationship between these estimates changed seasonally. In May, during a spring bloom of Phaeocystis sp., 14C-TOC was 52 % and 50 % of GPP-DO and GPP-18O respectively, while in August, during post-bloom conditions dominated by flagellates, 14C-TOC was 125 % of GPP-DO and 14C-TOC was 175 % of GPP-18O. Varying relationship between C and O rates may be the result of varying importance of respiration, where C-based rates estimate Net Primary Production (NPP) and O-based rates estimate Gross Primary Production (GPP).However, uncertainty remains in this comparison, given differing assumptions of the methods and the photosynthetic quotients.The median O:C ratio of 4.75 in May is within the range of that observed for other regions of the world’s ocean. However, the median O:C ratio for August is < 1, lower than in any other reported region. Our results suggest further research is needed to estimate O:C in Arctic waters, and at different times of the seasonal cycle.

Primary Productivity of Blanakan Fishpond at Subang, West Java

Subang regency is one of the largest fisheries area in West Java, so it is important to maintain the quality of fishpond area in Blanakan, Subang. Primary productivity can be defined as the production rate of organic carbon per unit time which is the result of solar energy by green plants to be converted into chemical energy through photosynthesis. Primary productivity can be used to define the quality of an ecosystem including fishpond. The aim of this research was to measure the value of primary productivity in mangrove fishpond, determine the correlation between the primary productivity and the content of nitrate, phosphate, and chlorophyll-a, and to analyse the significance primary productivity differences among three sampling stations. The samples were collected from three sampling stations, where all of those consist of mangrove Avicennia marina vegetation. Each station was divided into two points based on different depth i.e. 0 and 1,5 meters. The measurement of primary productivity was done by light-dark bottle method, meanwhile the nitrate, phosphate and chlorophyll-a concentration by spectrophotometer method. The result showed that the value of primary productivity ranged from 39.0625 to 101.5625 mgC/m3/day with the highest value obtained at station I and the lowest value at station III. According to statistical test, there were a significant differences of primary productivity value among three sampling stations with the value is 0.003 (p < 0.05). Correlation analysis showed that primary productivity was correlated positively with chloropyll-a and negatively with nitrate and phosphate contain water.

Relationship of primary productivity and phytoplankton abundance in Muara Kuala Raja, Bireuen district, Aceh

Phytoplankton is a major producer in oceans which require the availability of nutrients, pH, temperature and light intensity in order to increase the productivity. This study aims to analyse the relationship between the primary productivity and the abundance of phytoplankton in Muara Kuala Raja Bireuen, Aceh. This study was conducted on May 2017. Location sampling have 3 station points. The measure of primary productivity was examined by a light-dark bottle oxygen method. The relationship between the primary productivity and the abundance of phytoplankton was analysed by using Principal Component Analysis (PCA). The results showed that the highest average of gross and net primary productivity were found at station 1 of 209,12 mgC/m3/h and 172,00 mgC/m3/h. The highest abundance of phytoplankton was found at station 1 of 11477,76 ind/l. The result of PCA showed that each of the parameter spread between the two axes indicates the data diversity value. The data diversity value on the 1-axis was 37% and the 2-axis was 59%, so the total of data diversity between 1- axis and 2-axis was 96%. Based on the PCA analysis, it can be concluded that primary productivity has a strong relationship with the abundance of phytoplankton.

Modeling the Impact of Zooplankton Diel Vertical Migration on the Carbon Export Flux of the Biological Pump

One pathway of the biological pump that remains largely unquantified in many export models is the active transport of carbon from the surface ocean to the mesopelagic by zooplankton diel vertical migration (DVM). Here, we develop a simple representation of zooplankton DVM and implement it in a global export model as a thought experiment to illustrate the effects of DVM on carbon export and mesopelagic biogeochemistry. The model is driven by diagnostic satellite measurements of net primary production, algal biomass, and phytoplankton size structure. Due to constraints on available satellite data, the results are restricted to the latitude range from 60°N to 60°S. The modeled global export flux from the base of the euphotic zone was 6.5 PgC/year, which represents a 14% increase over the export flux in model runs without DVM. The mean (± standard deviation, SD) proportional contribution of the DVM‐mediated export flux to total carbon export, averaged over the global domain and the climatological seasonal cycle, was 0.16 ± 0.04 and the proportional contribution of DVM activity to total respiration within the twilight zone was 0.16 ± 0.06. Adding DVM activity to the model also resulted in a deep local maximum in the oxygen utilization profile. The model results were most sensitive to the assumptions for the fraction of individuals participating in DVM, the fraction of fecal pellets produced in the euphotic zone, and the fraction of grazed carbon that is metabolized.