Primary Production Measurements Research Articles

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.

Remotely sensed agricultural grassland productivity responses to land use and hydro-climatic drivers under extreme drought and rainfall

Climate change is expected to increase the frequency and intensity of drought globally with potentially significant consequences for grasslands. We examined grassland responses to a long-term drought on the Darling Downs, eastern Australia, using the Enhanced Vegetation Index (EVI), a remotely sensed measure of primary productivity. This extreme drought period had rainfall deficits comparable to the hottest and driest projected climate change scenarios for 2030 and was followed by extreme rainfall. This juxtaposition allowed investigation of grassland dynamics (decline and recovery) under extreme climatic variability. Our aim was to determine whether factors associated with grassland decline during extreme drought are the same as those that drive recovery post drought. There is limited knowledge about whether the determinants of grassland decline and recovery are consistent, but this information is important for understanding how best to reduce grassland decline, without inhibiting recovery. We calculated EVI (Enhanced Vegetation Index) trends at 2549 grassland sites situated in an agricultural landscape and used boosted regression trees to model these against multiple hydro-climatic and land use factors. As anticipated, hydro-climatic variables were key drivers of EVI trends in both the drought and wet phases, with higher soil moisture corresponding to less decline in the drought phase and enhanced recovery in the wet phase; however, land use and plant trait variables were also important predictors of EVI trends. Higher proportions of dryland agriculture in the local landscape, high C3:C4 ratios and lower proportions of woody vegetation in the local landscape were associated with negative EVI trends (i.e. greater decline) during drought, but had inverse or negligible effects during the post drought recovery phase. Our results suggest that mitigating decline and fostering grassland recovery following drought requires considering multiple hydro-climatic, land use and plant trait drivers and how their importance changes under drought and wet phases.

Using otolith chronologies to understand long‐term trends and extrinsic drivers of growth in fisheries

AbstractIdentifying trends and drivers of fish growth in commercial species is important for ongoing sustainable management, but there is a critical shortage of long‐term datasets in marine systems. Using otolith (ear bone) sclerochronology and mixed‐effects modeling, we reconstructed nearly four decades (37 yr) of growth across four oceanographically diverse regions in an iconic fishery species, snapper (Chrysophrys auratus). Growth was then related to environmental factors (sea surface temperature, chlorophyll‐a, and Southern Oscillation Index) and population performance indicators (recruitment and commercial catch). Across the decades, growth rates declined in the two most productive fishery regions. Chlorophyll‐a (a measure of primary productivity) was the best predictor of growth for all regions, but direction and magnitude of the relationships varied, indicating regional‐specific differences in intra‐specific competition. Sea surface temperature was positively correlated with fish growth, but negatively correlated after temperature reached optimum thermal maxima, which suggests individuals in warmer regions may be under thermal stress. Growth also decreased at the extremes of the Southern Oscillation Index, indicating fish growth is impeded in significant climatic events. Contrasting relationships between growth, catch, and recruitment indicated regional‐specific density‐dependent effects, with growth positively correlated with population size in one region but negatively correlated in another. Our results indicate that under future ocean warming and increased frequency of extreme climate events, fish growth and fisheries productivity are likely to be affected. Furthermore, the interactive effects of extrinsic factors also indicated that stressors on fisheries should be managed collectively. We show that otolith chronologies are an effective method to assess long‐term trends and drivers of growth in fishery species. Such informed ecological predictions will help shape the sustainable management of fisheries under future changing climates.

Efectos de la fertilización del suelo sobre la producción de hojarasca en bosques pluviales tropicales del Chocó biogeográfico, Colombia

It has been hypothesized that the net primary productivity of low-altitude tropical rainforests is limited by the concentration of soil nutrients, mainly by edaphic phosphorus. To test this hypothesis, litter production was evaluated as a measure of net primary productivity in two tropical rain forests located in the towns of Opogodo and Pacurita in the biogeographic Choco. One hundred and twenty-five leaf litter collectors were installed, which were monitored monthly for one year. These collectors were distributed in five fertilization treatments (control, nitrogen, phosphorus, potassium and NPK) to determine the effects of the addition of nutrients on the production of total litter and its components (leaves, branches, reproductive and miscellaneous material (material in decomposition)), and the reproduction / leaf ratio. In Opogodo, the application of nitrogen or phosphorus increased total litter production, nitrogen fertilization increased the production of branches, and the addition of nitrogen, phosphorus or potassium, separately, increased the production of miscellaneous material. Whereas, with fertilization, the production of reproductive material and the relation reproductive/leaves were reduced. In synthesis, fertilization changed the relative contribution of the different litter components, and favored the construction of photosynthetic structures (leaves), compared to reproductive structures. In addition, it was shown that the fall of litter is limited by nitrogen, phosphorus and potassium, which influence the carbon capture of these forest ecosystems. In Pacurita, fertilization had no significant effects on litter production.

Carbon and nitrogen productivity during spring in the oligotrophic Indian Ocean along the GO-SHIP IO9N transect

There is limited biogeochemical rate data from the oligotrophic central Indian Ocean, but it is known that there are geographical gradients in the physical and chemical conditions that may lead to unique biogeochemical regimes. As participants on a GO-SHIP repeat hydrography cruise, a transect was completed in spring of 2016 from 28 °S to 18 °N in the Indian Ocean, roughly along the 95 °E meridion. Cell count samples (phytoplankton and heterotrophic bacteria) analyzed by flow cytometry, and samples for carbon and nitrogen productivity incubations, assessed by stable isotopic tracers, were obtained from 20 m at approximately every other degree of latitude. Microbial cell counts by flow cytometry indicate that Prochlorococcus was the principal autotroph, but with increasing contributions of Synechococcus around the equator. Large eukaryotes (> 20 μm), imaged using FlowCAM, were generally absent or in very low abundance (< 0.5 μg C L−1) from near-surface waters. Heterotrophic bacteria contributed 28.4 ± 4.6% of the microbial community biomass and were positively correlated to autotrophic biomass. Dissolved nitrate and phosphate concentrations were below detection limits throughout the surface 50 m, while ammonium was undetectable at almost all stations and depths. In the 50–200 m depth range, nitrate and phosphate concentrations steadily increased from south to north, reaching a maximum of 31 and 2.2 μM respectively north of 6 °N. The ratio of dissolved NO3-:PO4- standing stocks was always below 15. Urea concentrations (0.02–0.18 μmol L−1) showed an increasing trend towards the north and dissolved organic phosphorus concentrations (0.25–0.37 μmol L−1) had a maxima between 5 and 15 °S. Absolute uptake rates of nitrate, ammonium and urea were all less than 1.5 nmol N L−1 h−1 south of 15 °S, and increased until local maxima of 3.4, 9.0, and 21 nmol N L−1 h−1 for nitrate, ammonium, and urea respectively, were reached between 1.5 and 6.5 °N. Ammonium and urea uptake rates were consistently 3–8 times higher than nitrate uptake rates, with a mean f-ratio of 0.23 for the entire transect. Primary production followed the same trend of nitrogen uptake, with a local maximum of 7.4–10.8 nmol C L−1 h−1 found 1.5–6.5 °N. These data represent some of the first reported measurements of primary production, nitrogen uptake, and phytoplankton diversity across biogeochemical provinces in the central oligotrophic Indian Ocean a large but understudied region of the global ocean.

Carbon Sequestration in the Urban Areas of Seoul with Climate Change: Implication for Open Innovation in Environmental Industry

This study estimates the impact of potential climate change, and human interference (anthropogenic deforestation), on temperate forest carbon pool change in the capital area of South Korea, using a dynamic global vegetation model (DGVM). Additionally, the characteristics of forest carbon pool change were simulated based on a biogeochemical module. The change of atmospheric carbon dioxide (CO2) concentration is deeply related to the change of the forest carbon pool, which is estimated with the measures of Net Primary Productivity (NPP), and Soil Carbon Storage (SCS). NPP and SCS were estimated at 2.02–7.43 tC ha−1 year−1 and 34.55–84.81 tC ha−1, respectively, during the period 1971–2000. SCS showed a significant decreasing tendency under the conditions of increasing air temperature, and precipitation, in the near future (2021–2050), and far future (2071–2100), which were simulated with future-climate scenario data without any human interference. Besides, it is estimated that the temporal change in NPP indicates only a small decrease, which is little influenced by potential climate change. In the case of potential climate change plus human interference, the decrease rate of NPP and SCS were simulated at 17–33% and 21–46%, respectively, during 2000–2100. Furthermore, the effect of potential human interference contributes to 83–93% and 61–54% of the decrease rate of NPP and SCS, respectively. The decline in the forest carbon pool simulated in this study can play a positive role in increasing atmospheric carbon dioxide. Consequently, the effect of potential human interference can further accelerate the decline of the temperate forest carbon pool. For the effective reduction of carbon dioxide emissions in urbanizing areas, it would be more effective to control human interference. Consequently, this study suggests that a rate of reforestation corresponding to the deforestation rate should be at least maintained, with long term monitoring and modeling-related studies, against climate change problems.

Comparing static and dynamic incubations in primary production measurements under different euphotic and mixing depths

Since phytoplankton production is usually estimated from static incubations (fixed depths or light levels), a mesocosm study was performed to evaluate the significance of mixing depth, mixing intensity and load of humus of natural phytoplankton assemblages. Vertically rotated (dynamic) incubations usually gave higher results than static incubations in humus-rich water. Mixing intensity was of significant importance in one of 2 years tested, but strong interaction effects with humus complicated the explanation. Differences in primary production between dynamic incubations did not fully reflect the received PAR dose, and increased humus and increased mixing depth increased the photo-assimilation efficiency. Different single-depth incubations did not provide a shortcut method to measure water-column primary production with high accuracy. Results diverged from theoretical estimates based on recent combined photo-biological and physical environmental models. The large variability in responses to mixing is supposed to reflect species-specific adaptations and pre-history regarding quantity (photons) and quality (spectral distribution) of the optical environment in an assemblage of different species. The proportional abundance of each species with its specific characters will therefore strongly influence bulk primary production. Due to such variable responses, clear guidelines for a “best practice” in primary production measurements cannot be given, based on the present results.

Inter‐annual variations over a decade of primary production of the seagrass Posidonia oceanica

AbstractWe acquired quasi‐continuous measurements of community gross primary production (GPP) by mass balance of O2 measured on a mooring, from August 2006 to October 2016 over a Posidonia oceanica meadow (10 m depth) in the Bay of Revellata (Corsica). Over the 2006–2016 period, annual GPP averaged 88 molO2 m−2 yr−1 and ranged from 61 to 108 molO2 m−2 yr−1. The 2 yr with the lowest annual GPP (2007 and 2015) were characterized by a low occurrence of fall–winter storms, probably leading to the accumulation of leaf litter in fall and early winter; we hypothesize this might have led to occultation of benthic macro‐algae. Among the other years, the inter‐annual variability of GPP was related to changes during the February–August period, as GPP was repeatable among years during the September–January period. For the February–August period, inter‐annual variations of GPP were correlated to chlorophyll a (Chl a), solar radiation (SR) and water temperature. Computed phytoplankton GPP corresponded to a small fraction of community GPP, so the relation between GPP and Chl a probably reflected inter‐annual variations of a common driver that we hypothesize to be nutrient inputs. The correlation of GPP with SR shows that light availability contributed to inter‐annual variations of the development of P. oceanica. The positive relation between GPP and temperature was consistent with the fact that the observed temperatures in the Bay of Revellata were during the study period within the comfort range for the growth of P. oceanica, despite an increase of water temperature of 0.7°C.

Seasonal patterns of thermal stratification and primary production in the northern parts of Lake Tanganyika

Abstract Thermal stratification in meromictic Lake Tanganyika weakens during the cool, dry and windy season, allowing intrusions of deeper nutrient-rich waters into the upper mixed layer enhancing primary productivity. The current study examined the seasonal influence of thermal structure on the patterns of primary production in Lake Tanganyika. Two sites (Kigoma Bay and Mahale) were sampled on a monthly basis for 1 year. Water temperature and chlorophyll a fluorescence profiles (0–100 m) were measured using a multisonde. Water samples were taken every 20 m (0–100 m) to measure soluble reactive phosphorus (SRP), chlorophyll a and primary production. Pulse Amplitude Modulated Fluorometry was used for the measurements of primary production. The results show that the dry season coincided with higher wind speeds, elevated SRP and some peaks of chlorophyll a and primary production at both sites. During the wet season, high levels of chlorophyll a and primary production coincided with an increase in the euphotic depth, a deep chlorophyll maximum (DCM) and a contribution from metalimnetic areal production at both sites. Our results suggest that the vertical distribution of primary production in Lake Tanganyika is affected by the lake thermal structure, nutrient availability and the extent of the euphotic zone. In Lake Tanganyika, estimates of areal primary production were significantly affected by DCM and required estimation throughout the entire upper mixed layer and the metalimnion which extended to ~89 m.

A 55-Year Time Series Station for Primary Production in the Adriatic Sea: Data Correction, Extraction of Photosynthesis Parameters and Regime Shifts

In 1962, a series of in situ primary production measurements began in the Adriatic Sea, at a station near the island of Vis. To this day, over 55 years of monthly measurements through the photic zone have been accumulated, including close to 3000 production measurements at different depths. The measurements are conducted over a six-hour period around noon, and the average production rate extrapolated linearly over day length to calculate daily production. Here, a non-linear primary production model is used to correct these estimates for potential overestimation of daily production due to linear extrapolation. The assimilation numbers are recovered from the measured production profiles and subsequently used to model production at depth. Using the recovered parameters, the model explained 87% of variability in measured normalized production at depth. The model is then used to calculate daily production at depth, and it is observed to give on average 20% lower daily production at depth than the estimates based on linear extrapolation. Subsequently, water column production is calculated, and here, the model predicted on average 26% lower water column production. With the recovered parameters and the known magnitude of the overestimation, the time-series of water column production is then re-established with the non-linearly-corrected data. During this 55-year period, distinct regimes were observed, which were classified with a regime shift detection method. It is then demonstrated how the recovered parameters can be used in a remote sensing application. A seasonal cycle of the recovered assimilation number is constructed along with the seasonal cycle of remotely-sensed chlorophyll. The two are then used to model the seasonal cycle of water column production. An upper and a lower bound on the seasonal cycle of water column production based on remotely-sensed chlorophyll data are then presented. Measured water column production was found to be well within the range of remotely-sensed estimates. With this work, the utility of in situ measurements as a means of providing information on the assimilation number is presented and its application as a reference for remote sensing models highlighted.

Produktivitas Primer Fitoplankton pada Daerah Penangkapan Ikan di Taman Wisata Alam Danau Buyan, Buleleng, Bali

This research aims to identify productivity value of phytoplankton’s net primary as well as its relation within parameter of physics, chemistry, and aquatic biology to the productivity value of phytoplankton’s net primary in the waters of Lake Buyan Nature Park. Measurement of primary phytoplankton productivity is conducted by using bright and dark bottle method. The taking of lake water samples for measurement of phytoplankton primary productivity and measurement of supporting parameters namely physics (temperature, brightness, turbidity), chemistry (pH, nitrate, phosphate) and biology (phytoplankton abundance) were carried out at four research stations in the fishing area. Data analysis used in this research is correlation analysis among parameters of physic, chemistry, and aquatic biology to the net primary productivity value of phytoplankton by using the PAST 3.1 application. The obtained result showed that the value of net primary productivity ranged from 76.39 to 211.46 mgC / m3 / day and the parameters of physics, chemistry and aquatic biology have a relationship with net primary productivity of phytoplankton. Brightness, abundance of phytoplankton, nitrate, temperature, dissolved oxygen, pH and phosphate which are positively correlated with net primary productivity of phytoplankton while water turbidity is negatively correlated with it. Parameters that have a strong to very strong relationship with net primary productivity are dissolved oxygen, temperature, nitrate, phytoplankton abundance, and water brightness.

The 13C method as a robust alternative to 14C-based measurements of primary productivity in the Mediterranean Sea.

Due to the increasing constraints on using the radioactive isotope 14C to measure primary productivity (14C-PP), we determined the surface carbon fixation rates in the Mediterranean Sea, using the alternative stable isotope 13C method (13C-PP). Rates obtained (13C-POCp) were compared with simultaneous 14C-POCp measurements in samples of different volumes (72 mL and 1.2 L). We also tested the variation of the percentage of dissolved primary production (PER), to the total productivity using organic and inorganic filters (14C method). 13C-POCp rates ranged from 0.4, in the Ionian basin, to 1.5 mgC m−3 h−1 in the Ligurian region. These results agreed with those found with the 14C-PP in 1.2-L samples (two sample t-test, t = 1.035, df = 22, P = 0.31). However, we found that 14C-POCp rates derived from 72-mL incubations were 46% lower than those measured with 13C-PP. The discrepancy between large and small volume incubations was likely due to differences in the number of large phytoplankton cells within the community. PER values measured with silver membrane filters yielded similar results than those obtained using polycarbonate filters. Our findings showed that when the sample size is carefully chosen, the 13C-PP provide comparable results to 14C-PP even in waters of low productivity in the Mediterranean Sea.

Turbulence simultaneously stimulates small- and large-scale CO2 sequestration by chain-forming diatoms in the sea

Chain-forming diatoms are key CO2-fixing organisms in the ocean. Under turbulent conditions they form fast-sinking aggregates that are exported from the upper sunlit ocean to the ocean interior. A decade-old paradigm states that primary production in chain-forming diatoms is stimulated by turbulence. Yet, direct measurements of cell-specific primary production in individual field populations of chain-forming diatoms are poorly documented. Here we measured cell-specific carbon, nitrate and ammonium assimilation in two field populations of chain-forming diatoms (Skeletonema and Chaetoceros) at low-nutrient concentrations under still conditions and turbulent shear using secondary ion mass spectrometry combined with stable isotopic tracers and compared our data with those predicted by mass transfer theory. Turbulent shear significantly increases cell-specific C assimilation compared to still conditions in the cells/chains that also form fast-sinking, aggregates rich in carbon and ammonium. Thus, turbulence simultaneously stimulates small-scale biological CO2 assimilation and large-scale biogeochemical C and N cycles in the ocean.

A multi-method autonomous assessment of primary productivity and export efficiency in the springtime North Atlantic.

Fixation of organic carbon by phytoplankton is the foundation of nearly all open-ocean ecosystems and a critical part of the global carbon cycle. But quantification and validation of ocean primary productivity at large scale remains a major challenge, due to limited coverage of ship-based measurements and the difficulty of validating diverse measurement techniques. Accurate primary productivity measurements from autonomous platforms would be highly desirable, due to much greater potential coverage. In pursuit of this goal we estimate gross primary productivity over two months in the springtime North Atlantic from an autonomous Lagrangian float using diel cycles of particulate organic carbon derived from optical beam attenuation. We test method precision and accuracy by comparison against entirely independent estimates from a locally parameterized model based on chlorophyll a and light measurements from the same float. During nutrient replete conditions (80% of the study period), we obtain strong relative agreement between the independent methods across an order of magnitude of productivities (r2=0.97), with slight under-estimation by the diel cycles method (-19±5 %). At the end of the diatom bloom, this relative difference increases to -58 % for a six-day period, likely a response to SiO4 limitation, which is not included in the model. In addition, we estimate gross oxygen productivity from O2 diel cycles and find strong correlation with diel cycles-based gross primary productivity over the entire deployment, providing further qualitative support to both methods. Finally, simultaneous estimates of net community productivity, carbon export and particle size suggest that bloom growth is halted by a combination of reduced productivity due to SiO4 limitation and increased export efficiency due to rapid aggregation. After the diatom bloom, high chlorophyll a normalized productivity indicates that low net growth during this period is due to increased heterotrophic respiration and not nutrient limitation. These findings represent a significant advance in the accuracy and completeness of upper ocean carbon cycle measurements from an autonomous platform.

Temporal Variability of Primary Production Explains Marine Ecosystem Structure and Function

Understanding drivers of ecosystem structure and function is a pervasive goal in academic and applied research. We used 24 synthetic ecosystem-level indices derived from trophic models, and independently derived data for Net Primary Productivity, to investigate drivers of ecosystem structure and function for 43 marine ecosystems distributed in all oceans of the world and including coastal, estuaries, mid-ocean islands, open-ocean, coral reef, continental shelf, and upwelling ecosystems. Of these indices, ecosystem Biomass, Primary Production, Respiration, the ratio of Biomass to Total System Throughput (sum of total energy flow into and out of an ecosystem as well as between ecosystem components), the ratio of Production to Biomass, Residence Time (mean time that a unit of energy remains in the ecosystem), Average Trophic Level, and Relative Ascendency (index of organization and complexity of a food web) displayed relationships with measures of Net Primary Productivity (NPP). Across all ecosystems, relationships were stronger with seasonal and interannual variability of NPP as compared to mean NPP. Both measures of temporal variability were combined into multivariate predictive relationships for each ecosystem index, with r2 values ranging from 0.14 to 0.49 and Akaike’s information criteria values from − 8.44 to 3.26. Our results indicate that despite large geographic and environmental differences, temporal variability of NPP is strongly linked to the structure and function of marine ecosystems.

Asymmetric responses of primary productivity to altered precipitation simulated by ecosystem models across three long-term grassland sites

Abstract. Field measurements of aboveground net primary productivity (ANPP) in temperate grasslands suggest that both positive and negative asymmetric responses to changes in precipitation (P) may occur. Under normal range of precipitation variability, wet years typically result in ANPP gains being larger than ANPP declines in dry years (positive asymmetry), whereas increases in ANPP are lower in magnitude in extreme wet years compared to reductions during extreme drought (negative asymmetry). Whether the current generation of ecosystem models with a coupled carbon–water system in grasslands are capable of simulating these asymmetric ANPP responses is an unresolved question. In this study, we evaluated the simulated responses of temperate grassland primary productivity to scenarios of altered precipitation with 14 ecosystem models at three sites: Shortgrass steppe (SGS), Konza Prairie (KNZ) and Stubai Valley meadow (STU), spanning a rainfall gradient from dry to moist. We found that (1) the spatial slopes derived from modeled primary productivity and precipitation across sites were steeper than the temporal slopes obtained from inter-annual variations, which was consistent with empirical data; (2) the asymmetry of the responses of modeled primary productivity under normal inter-annual precipitation variability differed among models, and the mean of the model ensemble suggested a negative asymmetry across the three sites, which was contrary to empirical evidence based on filed observations; (3) the mean sensitivity of modeled productivity to rainfall suggested greater negative response with reduced precipitation than positive response to an increased precipitation under extreme conditions at the three sites; and (4) gross primary productivity (GPP), net primary productivity (NPP), aboveground NPP (ANPP) and belowground NPP (BNPP) all showed concave-down nonlinear responses to altered precipitation in all the models, but with different curvatures and mean values. Our results indicated that most models overestimate the negative drought effects and/or underestimate the positive effects of increased precipitation on primary productivity under normal climate conditions, highlighting the need for improving eco-hydrological processes in those models in the future.

Extraction of Photosynthesis Parameters from Time Series Measurements of In Situ Production: Bermuda Atlantic Time-Series Study

Computing the vertical structure of primary production in ocean ecosystem models requires information about the vertical distribution of available light, chlorophyll concentration and photosynthesis response parameters. Conversely, given information on vertical structure of chlorophyll and light, we can extract photosynthesis parameters from vertical profiles of primary production measured at sea, as we illustrate here for the Bermuda Atlantic Time-Series Study. The procedure is based on a model of the production profile, which itself depends on the underwater light field. To model the light field, attenuation coefficients were estimated from measured optical profiles using a simple model of exponential decay of photosynthetically-available irradiance with depth, which accounted for 97% of the variance in the measured optical data. With the underwater light climate known, an analytical solution for the production profile was employed to recover photosynthesis parameters by minimizing the residual model error. The recovered parameters were used to model normalized production profiles and normalized watercolumn production. The model explained 95% of the variance in the measured normalized production at depth and 97% of the variance in measured normalized watercolumn production. A shifted Gaussian function was used to model biomass profiles and accounted for 93% of the variance in measured biomass at depth. An analytical solution for watercolumn production with the shifted Gaussian biomass was also tested. With the recovered photosynthesis parameters, maximum instantaneous growth rates were estimated by using a literature value for the carbon-to-chlorophyll ratio in this region of the Atlantic. An exact relationship between the maximum instantaneous growth rate and the daily growth rate in the ocean was derived. It was shown that calculating the growth rate by dividing the production by the carbon-to-chlorophyll ratio is equivalent to calculating it from the ratio of the final to the initial biomass, even when production is time dependent. Finally, the seasonal cycle of the recovered assimilation number at the Bermuda Station was constructed and analysed. The presented approach enables the estimation of photosynthesis parameters and growth rates from measured production profiles with only a few model assumptions, and increases the utility of in situ primary production measurements. The retrieved parameters have direct applications in satellite-based estimates of primary production from ocean-colour data, of which we give an example.

PRODUCTIVITY OF DIATOMS IN CULTURE AND IN MARINE HABITATS

The diatom dominated phytoplankton net primary production in different areas of the ocean (from 100-1000 mg C. m-2. day-1) and in estuaries (up to 2000 mg C. m-2. day-1) is compared with the maximum productivity of marine diatoms in culture (50 g C . m-2 . day-1) for Cyclotella cryptica (Centrales, Diatomeae) and 1000 mg C . m-2. day-1 for Coscinodiscus asteromphalus (Centrales, Diatomeae). The rate of C-assimilation as a measure of primary production is critically discussed in relation to the different factors regulating the reproduction of cells and the production of organic material. The evaluation of another parameter for primary production: light dependent protein synthesis (LPS) is proposed, which brings reproduction of phytoplankton cells and the production of organic material closer together. As an example of the requirement for more information about the potential growth and production rate of diatom species, some results on the cultivation of the tropical shallow water diatom Bellerochea yucatanensis V. STOSCH (Centrales, Diatomeae) are presented. At 30 C this species has a specific growth rate (µ max) of = 4.4 divisions per day and 4 divisions per day at 34°C with an average cell size of 34 x 26 ? m. The temperature range of this species is from 12°C (µ = 0.3) to 35°C (µ = 2).

The best incubation time for primary productivity of phytoplankton in Laguna Lake, North Maluku, Indonesia

Yuliana, Irfan M. 2018. The best incubation time for primary productivity of phytoplankton in Laguna Lake, North Maluku, Indonesia. Biodiversitas 19: 1021-1028. Primary productivity of phytoplankton is a source of energy and organic matter utilized by organisms at higher food chain levels. The measurement of the high rate of primary productivity can be done through the incubation of sample water at a particular time and time depending on sunlight intensity. This study aimed to estimate the best incubation time to achieve the highest primary productivity of phytoplankton in Laguna Lake, Ternate City, North Maluku Province, Indonesia in February 2017. The study was conducted at one location with four different levels of depth of 0, 5, 10, and 15 meters, and at three incubation times, i.e., 09:00-13:00, 10:00-14:00, and 11:00-15:00 (Eastern Indonesian Time). The chemical and physical parameters of radiance, temperature, pH, nitrate, and orthophosphate content were measured to estimate water quality of the lake. The results of this study showed that were 10 genera of phytoplankton belonging to Bacillariophyceae (6 genera), Chlorophyceae (4 genera), and Cyanophyceae (2 genera). The Laguna Lake has temperature ranged between 29.0-31.1oC, nitrate content of 0.22-0.58 mg l-1, orthophosphate content of 0.14-0.27 mg l-1, and pH 7. The primary productivity value at incubation time 09:00-13:00; 10:00-14:00; and 11:00-15:00 were of 101,851-258,278; 40,59-351,643; and 76,197-305,754 mgC m-3 hours-1, respectively. The best incubation time that provides the highest value in the measurement of primary productivity of phytoplankton at Laguna Lake was at 10:00 am to 14:00 pm.