Annual Phytoplankton Primary Production Research Articles

Future Climate Scenarios for Northern Baffin Bay and the Pikialasorsuaq (North Water Polynya) Region

ABSTRACT Northern Baffin Bay is distinct due to the presence of the North Water Polynya, a region referred to as “Pikialasorsuaq” by Inuit in Greenland and “Sarvarjuaq” by Inuit in Canada. Surrounding communities rely on the polynya as hunting and shipping grounds for much of the year due to its lower sea ice concentration and high primary productivity; however, Arctic warming threatens the dynamics of the region by altering the sea ice cycle, oceanic heat content and freshwater input. The aim of this study is to examine the future of northern Baffin Bay and Pikialasorsuaq under various climate warming scenarios using the Nucleus for Modelling of the Ocean (NEMO) engine, coupled to the Louvain-la-Neuve (LIM2) sea ice model. Five experiments were run on a resolution Arctic and Northern Hemispheric Atlantic (ANHA4) configuration over the period 1981–2070 forced by a range of global climate models. By 2070 there is a significant decrease in sea ice thickness and concentration, with an overall warming and salinity increase in the upper 500 m of the water column. Increased freshwater input from melting Greenland glaciers results in a more muted salinity increase in the top 50 m, while deeper waters are impacted by increased penetration of warm, saline Atlantic Water into Baffin Bay through Davis Strait. These physical changes impact the formation of the polynya in the future. The polynya is expected to continue to form on the eastern side near Greenland through mixing of warm Atlantic Waters to the surface, while the western side near Ellesmere Island has an increased ice area flux through Nares Strait and increased stratification. Additionally, there is a shallowing of mixed layer depth and increase in density stratification under the greatest warming scenarios. Implications to biogeochemical properties include a 0.5% decrease in total alkalinity, a 3.4% decreased in dissolved oxygen concentration but no net change in annual phytoplankton primary production. However, there are large changes in the phytoplankton bloom dynamics, including a 50% decrease in the autumn bloom and a 20-day advance in the spring bloom. Overall, our study suggests significant oceanographic changes which could lead to a loss of the recurrent polynya in its historical state, and shifts in primary production which could have, as yet uncertain, consequences for the food web and higher trophic levels.

Seasonal to Inter-Annual Variability of Primary Production in Chesapeake Bay: Prospects to Reverse Eutrophication and Change Trophic Classification

Estuarine-coastal ecosystems are rich areas of the global ocean with elevated rates of organic matter production supporting major fisheries. Net and gross primary production (NPP, GPP) are essential properties of these ecosystems, characterized by high spatial, seasonal, and inter-annual variability associated with climatic effects on hydrology. Over 20 years ago, Nixon defined the trophic classification of marine ecosystems based on annual phytoplankton primary production (APPP), with categories ranging from “oligotrophic” to “hypertrophic”. Source data consisting of shipboard measurements of NPP and GPP from 1982 to 2004 for Chesapeake Bay in the mid-Atlantic region of the United States supported estimates of APPP from 300 to 500 g C m−2 yr−1, corresponding to “eutrophic” to “hypertrophic” categories. Here, we developed generalized additive models (GAM) to interpolate the limited spatio-temporal resolution of source data. Principal goals were: (1) to develop predictive models of NPP and GPP calibrated to source data (1982 to 2004); (2) to apply the models to historical (1960s, 1970s) and monitoring (1985 to 2015) data with adjustments for nutrient loadings and climatic effects; (3) to estimate APPP from model predictions of NPP; (4) to test effects of simulated reductions of phytoplankton biomass or nutrient loadings on trophic classification based on APPP. Simulated 40% decreases of euphotic-layer chl-a or TN and NO2 + NO3 loadings led to decreasing APPP sufficient to change trophic classification from “eutrophic’ to “mesotrophic” for oligohaline (OH) and polyhaline (PH) salinity zones, and from “hypertrophic” to “eutrophic” for the mesohaline (MH) salinity zone of the bay. These findings show that improved water quality is attainable with sustained reversal of nutrient over-enrichment sufficient to decrease phytoplankton biomass and APPP.

Annual Phytoplankton Primary Production Estimation in a Temperate Estuary by Coupling PAM and Carbon Incorporation Methods

Phytoplankton primary production varies considerably with environmental parameters especially in dynamic ecosystems like estuaries. The aim of this study was to investigate short-term primary production along the salinity gradient of a temperate estuary over the course of 1 year. The combination of carbon incorporation and fluorescence methods enabled primary production estimation at short spatial and temporal scales. The electron requirement for carbon fixation was investigated in relation with physical-chemical parameters to accurately estimate primary production at high frequency. These results combined with the variability of the photic layer allowed the annual estimation of primary production along the estuary. Phytoplankton dynamics was closely related to salinity and turbidity gradients, which strongly influenced cells physiology and photoacclimatation. The number of electrons required to fix 1 mol of carbon (C) was ranged between 1.6 and 25 mol electron mol C−1 with a mean annual value of 8 ± 5 mol electron mol C−1. This optimum value suggests that in nutrient replete conditions like estuaries, alternative electron flows are low, while electrons transfer from photosystem II to carbon fixation is highly efficient. A statistical model was used to improve the estimation of primary production from electron transport rate as a function of significant environmental parameters. Based on this model, daily carbon production in the Seine estuary (France) was estimated by considering light and photic zone variability. A mean annual daily primary production of 0.12 ± 0.18 g C m−2 day−1 with a maximum of 1.18 g C m−2 day−1 in summer was estimated which lead to an annual mean of 64.75 g C m−2 year−1. This approach should be applied more frequently in dynamic ecosystems such as estuaries or coastal waters to accurately estimate primary production in those valuable ecosystems.

Phytoplankton primary production in the world's estuarine-coastal ecosystems

Abstract. Estuaries are biogeochemical hot spots because they receive large inputs of nutrients and organic carbon from land and oceans to support high rates of metabolism and primary production. We synthesize published rates of annual phytoplankton primary production (APPP) in marine ecosystems influenced by connectivity to land – estuaries, bays, lagoons, fjords and inland seas. Review of the scientific literature produced a compilation of 1148 values of APPP derived from monthly incubation assays to measure carbon assimilation or oxygen production. The median value of median APPP measurements in 131 ecosystems is 185 and the mean is 252 g C m−2 yr−1, but the range is large: from −105 (net pelagic production in the Scheldt Estuary) to 1890 g C m−2 yr−1 (net phytoplankton production in Tamagawa Estuary). APPP varies up to 10-fold within ecosystems and 5-fold from year to year (but we only found eight APPP series longer than a decade so our knowledge of decadal-scale variability is limited). We use studies of individual places to build a conceptual model that integrates the mechanisms generating this large variability: nutrient supply, light limitation by turbidity, grazing by consumers, and physical processes (river inflow, ocean exchange, and inputs of heat, light and wind energy). We consider method as another source of variability because the compilation includes values derived from widely differing protocols. A simulation model shows that different methods reported in the literature can yield up to 3-fold variability depending on incubation protocols and methods for integrating measured rates over time and depth. Although attempts have been made to upscale measures of estuarine-coastal APPP, the empirical record is inadequate for yielding reliable global estimates. The record is deficient in three ways. First, it is highly biased by the large number of measurements made in northern Europe (particularly the Baltic region) and North America. Of the 1148 reported values of APPP, 958 come from sites between 30 and 60° N; we found only 36 for sites south of 20° N. Second, of the 131 ecosystems where APPP has been reported, 37% are based on measurements at only one location during 1 year. The accuracy of these values is unknown but probably low, given the large interannual and spatial variability within ecosystems. Finally, global assessments are confounded by measurements that are not intercomparable because they were made with different methods. Phytoplankton primary production along the continental margins is tightly linked to variability of water quality, biogeochemical processes including ocean–atmosphere CO2 exchange, and production at higher trophic levels including species we harvest as food. The empirical record has deficiencies that preclude reliable global assessment of this key Earth system process. We face two grand challenges to resolve these deficiencies: (1) organize and fund an international effort to use a common method and measure APPP regularly across a network of coastal sites that are globally representative and sustained over time, and (2) integrate data into a unifying model to explain the wide range of variability across ecosystems and to project responses of APPP to regional manifestations of global change as it continues to unfold.

Reconstructed long-term time series of phytoplankton primary production of a large shallow temperate lake: the basis to assess the carbon balance and its climate sensitivity

Aiming at building the carbon budget for further climate change impact research in the large and shallow northern temperate Lake Vortsjarv, the present paper focuses on reconstructing the full phytoplankton primary production (PP) data series for the lake for the period of 1982–2009 covered by disconnected measurements, and testing the uncertainties involved both in the PP measurements and bio-optical modelling. During this 28-year period, in situ PP was measured in Vortsjarv in 18 years with 14C-assimilation technique. We reconstructed the full time series using a semi-empirical PP simulation model based on continuously measured PAR irradiance and interpolated values of monthly measured chlorophyll a (Cchl). The modelling results, which proved highly reliable during the calibration phase, correlated rather weakly with the annual PP estimates for the 18 years, which were based on 2-h incubations at midday, 1–2 times per month. Being based on continuous irradiance data, the modelled PP can be considered more reliable than the sparse measurements, especially for short to medium term studies. We demonstrate that in the long-term, the bio-optical method can be biased if changes in water colour or water level alter the light climate causing adaptive responses in the cellular chlorophyll content of light-limited phytoplankton.

Fifty years of primary production measurements in the Baltic entrance region, trends and variability in relation to land-based input of nutrients

Inter-annual variations and long-term trends in phytoplankton primary production (PP) within the Baltic entrance region (the Kattegat and the Belt Sea) are presented and discussed. The study employs the core of Danish monitoring data, with measurements at 6–8 different sites from the past 20–50 years. Temporal development of the annual PP is compared with changes and variations in the land-based nutrient inputs and to other, independent, Swedish and Danish PP data. Spatial and seasonal variations based on annual and monthly PP, respectively, are evaluated. There are large variations on all scales; annual PP ranges from 50 to 500 g C m − 2, with maximum values in some Danish fjords and minimum values in open waters during the 1950s. The Kattegat and the Sound have a lower mean production (135–165 g C m − 2; 1981–2000) than the Great and Little Belts (185–220 g C m − 2). Compared to 1950s and 1960s, the daily PP has changed from being almost constant between March and October, to having two more distinct maxima, one in March and one between July and September. It is obvious that annual mean production has increased considerably since the 1950s, but also that this increase took place before 1980. For data after 1980, we find a co-variation between annual nutrient loads and regional mean PP; years of low total nitrogen (TN) and total phosphorus (TP) input to the region coincide with low PP and vice versa. Waste-water treatment and measures in agriculture have reduced the land-based input of TN by about 1/3 and input of TP by about 2/3 since the 1980s, enough to cause a substantial decrease in the surface water nutrient concentrations. A simultaneous, but weak downward trend in the regional mean PP can be seen up to 1997, after which the trend is broken. Higher production from 1998 is most likely an effect of changes in the method used for determination of PP.

Trophic Status of the South-Eastern Baltic Sea: A Comparison of Coastal and Open Areas

Primary production, nutrient concentrations, phytoplankton biomass (incl. chlorophylla) and water transparency (Secchi depth), are important indicators of eutrophication. Earlier basin-wide primary production estimates for the Baltic Sea, a shallow shelf sea, were based mainly on open-sea data, neglecting the fundamentally different conditions in the large river plumes, which might have substantially higher production. Mean values of the period 1993–1997 of nutrient concentrations (phosphate, nitrate, ammonium and silicate), phytoplankton biomass, chlorophylla (chla) concentration, turbidity and primary production were calculated in the plumes of the rivers Oder, Vistula and Daugava and Klaipeda Strait as well as the open waters of the Arkona Sea, Bornholm Sea, eastern Gotland Sea and the Gulf of Riga. In the plumes, these values, except for primary production, were significantly higher than in the open waters. N:P ratios in the plumes were >16 (with some exceptions in summer and autumn), indicating potential P-limitation of phytoplankton growth, whereas they were <16 in the open Baltic Proper, indicating potential N-limitation. On the basis of in situ phytoplankton primary production, phytoplankton biomass and nutrient concentrations, the large river plumes and the Gulf of Riga could be characterized as eutrophic and the outer parts of the coastal waters and the open sea as mesotrophic. Using salinity to define the border of the plumes, their mean extension was calculated by means of a circulation model. Taking into account the contribution of coastal waters, the primary production in the Baltic Proper and the Gulf of Riga was 42·6 and 4·3×106tCyr−1, respectively. Hence, an annual phytoplankton primary production in the whole Baltic Sea was estimated at 62×106tCyr−1. The separate consideration of the plumes had only a minor effect on the estimation of total primary production in comparison with an estimate based on open sea data only. There is evidence for a doubling of primary production in the last two decades. Moreover, a replacement of diatoms by dinoflagellates during the spring bloom was noticed in the open sea but not in the coastal waters. A scheme for trophic classification of the Baltic Sea, based on phytoplankton primary production and biomass, chla and nutrient concentrations, is proposed.

Response of the Dutch Wadden Sea ecosystem to phosphorus discharges from the River Rhine

The primary production in the western part of the Dutch Wadden Sea (Marsdiep tidal basin) has been reported to have increased by a factor of two since the late 1970s. This doubling of the phytoplankton and the microphytobenthos production has been ascribed to the eutrophication of that area: mean annual phosphate concentrations have increased, whereas the nitrogen concentrations have not. Analysis of the available production data indicates a more than tenfold increase of the production of the phytoplankton in the Marsdiep tidal channel since the early 1950s. The increase in the phytoplankton production in the inner area seems to be of the same order of magnitude. The primary production of the phytobenthos and the secondary production of the macrozoobenthos seems to have increased proportionally to that of the phytoplankton. It is known that the nutrients in the Marsdiep tidal basin originate from the River Rhine. However, there are two possible routes for nutrients to reach that area. One is via the River IJssel and Lake IJssel (varying amounts of fresh water are sluiced out from the latter into the Wadden Sea). The other is along the coast of the North Sea, where the water transport is driven northeastwards by the residual current. Analysis of available data shows that the annual primary production in the Marsdiep tidal basin is mainly determined by the phosphate discharge from Lake IJssel which directly reach that part of the Wadden Sea, rather than from the River Rhine of which the water must run northward along the coast before reaching the western Dutch Wadden Sea. The close relation between fluctations in annual phosphate discharges and fluctations in annual phytoplankton primary production up to more than ten times the 1950 values indicates that primary production in the Marsdiep tidal channel and probably even in the main part of the whole basin, was and is phosphate limited.

Increased phytoplankton primary production in the Marsdiep area (Western Dutch Wadden Sea)

Annual phytoplankton primary production in the Marsdiep tidal inlet increased from ca 150 gC·m −2 in the period 1964 to 1976, to ca 300 gC·m −2 in 1981/1982 and 1985. This increase is considerable, but comparable to that observed in the outer Ems estuary, eastern Wadden Sea, from 240 gC·m −2a −1 in 1972/1973 to 400–500 gC.m −2.a −1 in 1976/1980. Although the increase is most probably due to eutrophication, as illustrated by the regular increase in phosphate in the Marsdiep area since 1950, it is difficult to explain why this affected primary production not earlier than the late seventies. Primary production has probably not increased in the more turbid inner parts of the Wadden Sea, where light is the limiting factor, and P values were already higher than in the inlet areas.

Biomass and production of phyto‐ and bacterio‐plankton in eutrophic Lake Tystrup, Denmark

SUMMARY. Phytoplankton primary production and biomass were compared with bacterial secondary production estimated by means of frequency of dividing cells (FDC) in eutrophic Lake Tystrup. Denmark. In the upper part of the photic zone, bacterial secondary production constituted 12% of the carbon fixed by the phytoplankton. In vertical profiles, bacterial secondary production ranged from 7.6% (early spring) to 121% (during August) of the carbon fixed by the algae. A close relationship was found between occurrence and activity of bacteria and algae, suggesting that released organic products are of primary importance to the bacteria. The annual phytoplankton primary production was estimated as 227 g C m‐2 compared to 102 g C m‐2 assimilated by the bacteria, so 45% of the carbon fixed by the phytoplankton went through pelagic bacteria.

A review of data on production and import of organic carbon in the western Wadden Sea

Annual phytoplankton primary production in the tidal channels of the western Wadden Sea cannot be estimated more precisely than 150±50 g C.m−2a−1, due to large spatial and short-term temporal variations. This implies that year-to-year variations and eventually long-term trends have to be very pronounced to be measurable even with a weekly sampling program.