Vertical Distribution Of Primary Production Research Articles

Vertical distribution of primary production and chlorophyll a in the eastern Kara Sea: Relations with river plume effects in late summer and autumn

Quantification of the vertical distribution of chlorophyll a (Chl-a), as one of characteristics of primary production (PP), is critically important to estimate annual PP in the water column (IPP) using models and remote sensing data. IPP estimation in optically complex and highly variable waters such as the Kara Sea is not a trivial task. In the present study, based on the data obtained during three multidisciplinary cruises to the eastern regions of the Kara Sea in August–October, the differences in the vertical distribution of Chl-a and PP under and without the influence of the river plume (Case II and Case I water types, respectively) are established. In Case I waters in August 2014, under the low values of the diffuse attenuation coefficient (Kd) of downwelling photosynthetically available radiation (PAR) (the median value (Me) Kd = 0.158 m-1) and the deep euphotic layer (Zeu) (Me = 30 m), the deep chlorophyll maximum (DCM) was well-pronounced. At the end of September 2015 in Case II waters influenced by the river runoff, when Me Kd increased 1.7-fold and Zeu decreased 1.3-fold, the DCM was absent. Also, the DCM was not manifested at the end of the growing season, under conditions of extremely low underwater PAR (Me = 0.35 mol quanta m−2 d−1). In the sampling period, the PP maxima were observed at the surface and the DCM did not influence the vertical PP distribution. The depth of the nitracline was directly associated with the distribution of riverine waters and determined the depth and degree of DCM manifestation. The outcomes of the presented study suggest that a decrease in subsurface PAR influenced by the impact of riverine waters and the total decline of incident radiation from August to October determine the vertical distribution of PP and Chl-a.

Study of monthly variations in primary production and their relationships with environmental factors in the Daya Bay based on a general additive model

In this study, the horizontal and vertical distribution of primary production (PP) and its monthly variations were described based on field data collected from the Daya Bay in January–December of 2016. The relationships between PP and environmental factors were analyzed using a general additive model (GAM). Significant seasonal differences were observed in the horizontal distribution of PP, while vertical distribution showed a relatively consistent unimodal pattern. The monthly average PP (calculated by carbon) ranged from 48.03 to 390.56 mg/(m2·h), with an annual average of 182.77 mg/(m2·h). The highest PP was observed in May and the lowest in November. Additionally, the overall trend in PP was spring>summer>winter>autumn, and spring PP was approximately three times that of autumn PP. GAM analysis revealed that temperature, bottom salinity, phytoplankton, and photosynthetically active radiation (PAR) had no significant relationships with PP, while longitude, depth, surface salinity, chlorophyll a (Chl a) and transparency were significantly correlated with PP. Overall, the results presented herein indicate that monsoonal changes and terrestrial and offshore water systems have crucial effects on environmental factors that are associated with PP changes.

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.

The importance of local versus external nutrient loads for Chl a and primary production in the Western Baltic Sea

The Western Baltic Sea is affected by eutrophication and receives nutrients from local land-based sources, atmospheric deposition and by advection from the neighbouring North Sea and Baltic Sea. In the present study, we evaluated the importance of local (Danish) versus external (Baltic Sea–North Sea) nutrient loads for surface Chl a-concentrations, total areal primary production and the vertical distributions of primary production in the W. Baltic Sea using the 3D coupled HBM-ERGOM model. This was assessed by improving descriptions of nutrient loads and primary production in the model and by conducting scenarios of different nutrient loads according to (i) the eutrophication level in 1990, (ii) the new Danish Water Plan (DWP) and iii) DWP+ the Baltic Sea Action Plan (BSAP2). The model results showed that local nutrient reductions have a profound effect on Chl a concentrations and primary production in the coastal areas of the Western Kattegat and the Belt Sea with the highest impact <10–25km from the coast. However, on average for the study area, Danish reductions have a limited effect. The DWP complemented the BSAP2 reductions spatially, since they had the highest impact in different areas and both were important for improving the ecological status of the ecosystem. The model suggested a significant change in the vertical distribution of primary production with less deep primary production in response to increased nutrient load. We recommend using this redistribution as an ecological indicator of eutrophication in seasonally stratified seas. The new description of primary production takes into account that carbon fixation continue, even when phytoplankton is severely nutrient limited. This model improvement increases primary production by a factor of 2.6 and brings the model estimates in agreement with measurements and the physiology of phytoplankton. We recommend that other dynamic ecosystem models using Liebig's law for primary production consider a similar approach.

Vertical distribution of primary production and chlorophyll a in the Kara Sea

On the basis of data obtained during three ecosystem expeditions in the Kara Sea, the vertical variability of the primary production (PP) and chlorophyll a (Chl) in autumn was studied. The Chl maximum was detected mainly on the surface (Chl0). A homogenous Chl distribution in the euphotic layer (1% photo-synthetically available radiation) and a nearly linear decrease in the Chl concentration below this layer were observed in waters with Chl0 values of 0.1–0.5 mg/m3. In waters with Chl0 > 0.5 mg/m3, the Chl concentration in the studied layer decreased linearly or exponentially. The subsurface Chl maximum (SCM) was registered weekly and was detected mostly in waters with a Chl0 content of 0.1–0.5 mg/m3. The SCM formation in the Kara Sea was consistent with the general patterns for the World Ocean. Water-column stability, the content of biogenic elements, and the level of subsurface irradiance had an approximately equal effect on SCM formation. The contribution of the SCM to the depth-integrated PP varied from 1 to 27%. The parameterization of vertical profiles of Chl was performed in order to be used in depth-integrated PP models. The Chl maximum on the surface and the negligible SCM facilitate the estimation of depth-integrated PP on the basis of satellite data and the use of vertical-resolution models.

Changes in the vertical distribution of primary production in response to land‐based nitrogen loading

Anthropogenic nitrogen (N)‐loading has decreased significantly in the Baltic Sea Transition Zone over the past two decades. We show that the vertical distribution of primary production (PP) changed as a function of land‐based N‐loading using 1385 water column photosynthesis estimates, in which photosynthetic parameters were determined both in the surface water layer and in the pycnocline‐bottom layer (PBL) at six stations near the Danish coast between 1998 and 2012. Total annual PP and surface layer PP (SPP) correlate positively with land‐based N‐loading from Denmark (p &lt; 0.003). The percentage of annual PP occurring in the PBL (denoted as deep primary production, DPP) varied annually between 6% and 30% (mean = 17%). The absolute magnitude of the DPP, as well as its relative proportion of total water column PP, correlates negatively with N‐loading (p &lt; 0.009 and p &lt; 0.0003, respectively). Thus, SPP decreases in response to decreased N‐loading, while DPP increases. Land‐based N‐loadings also correlate positively with the light attenuation coefficient (R2 = 0.39, p &lt; 0.05), which may in part explain the response in DPP to changes in N‐loading. DPP occurs in active phytoplankton communities acclimated and/or adapted to low light and producing oxygen in the PBL water.

Vertical variability of primary production and chlorophyll a in the Drake Passage during the austral spring period (October–November)

Vertical distribution of primary production (PP) and concentration of chlorophyll a (Chl) were studied during two cruises in the Drake Passage in November 2007 and 2008. Variability in the vertical curves of Chl was registered in the different hydrological zones of the Drake Passage. The Antarctic waters were characterized by a well-defined deep Chl maximum (DCM) during the austral spring. The investigation allowed us to conclude that the influence of DCM should be taken into consideration for a model-based estimation of annual PP in the Southern Ocean.

Interactions between freshwater input, light, and phytoplankton dynamics on the Louisiana continental shelf

We examined the effects of freshwater flow and light availability on phytoplankton biomass and production along the Louisiana continental shelf in the region characterized by persistent spring–summer stratification and widespread summer hypoxia. Data were collected on 7 cruises from 2005 to 2007, and spatially-averaged estimates of phytoplankton and light variables were calculated for the study area using Voronoi polygon normalization. Shelf-wide phytoplankton production ranged from 0.47 to 1.75 mg C m −2 d −1 across the 7 cruises. Shelf-wide average light attenuation ( k d ) ranged from 0.19–1.01 m −1 and strongly covaried with freshwater discharge from the Mississippi and Atchafalaya Rivers ( R 2=0.67). Interestingly, we observed that the euphotic zone (as defined by the 1% light depth) extended well below the pycnocline and to the bottom across much of the shelf. Shelf-wide average chlorophyll a (chl a) concentrations ranged from 1.4 to 5.9 mg m −3 and, similar to k d , covaried with river discharge ( R 2=0.83). Also, chl a concentrations were significantly higher in plume versus non-plume regions of the shelf. When integrated through the water-column, shelf-wide average chl a ranged from 26.3 to 47.6 mg m −2, but did not covary with river discharge, nor were plume versus non-plume averages statistically different. The high integrated chl a in the non-plume waters resulted from frequent sub-pycnocline chl a maxima. Phytoplankton production rates were highest in the vicinity of the Mississippi River bird's foot delta, but as with integrated chl a were not statistically different in plume versus non-plume waters across the rest of the shelf. Based on the vertical distribution of light and chl a, a substantial fraction of phytoplankton production occurred below the pycnocline, averaging from 25% to 50% among cruises. These results suggest that freshwater and nutrient inputs regulate shelf-wide k d and, consequently, the vertical distribution of primary production. The substantial below-pycnocline primary production we observed has not been previously quantified for this region, but has important implications about the formation and persistence of hypoxia on the Louisiana continental shelf.

The influence of landscape position on lakes in northern Wisconsin

1. Using data from the North Temperate Lakes Long‐Term Ecological Research site in northern Wisconsin, we present a series of examples illustrating how landscape setting can influence the static and dynamic aspects of many physical, chemical and biological properties of lakes.2. One important landscape attribute is the hydrologic position of a lake within the regional flow regime. Lake position determines the relative importance of groundwater and precipitation input to a lake, with lakes high in the landscape receiving a greater proportion of their input waters from precipitation than lakes lower in the landscape. Landscape position is strongly correlated with the concentration of base cations such as calcium and magnesium.3. Landscape position also influences how lakes respond to drought conditions. Lakes high in the landscape responded to a 4‐year drought with decreases in calcium mass, whereas lakes low in the landscape increased in mass of calcium. During extended dry conditions, these differential responses of lakes suggest that lakes already low in calcium (i.e. in a high position in the flow system) will have further reductions in calcium concentrations. These reductions could decrease the number of lakes offering suitable habitat for organisms such as crayfish and snails whose distributions are limited by calcium.4. Landscape position also affects silica concentrations in lakes, with lakes low in the landscape having silica concentrations up to three orders of magnitude greater than lakes high in the landscape. Differences in silica concentration affect robustness of freshwater sponge spicules which can potentially alter some aspects of the dynamics of littoral zone food webs.5. Landscape position can influence the vertical distribution of primary production. Concentrations of dissolved organic carbon are affected by landscape setting and can influence vertical light penetration, thus affecting the depth at which primary production can occur.6. Lake area and fish species richness are correlated with landscape position: larger, species‐rich lakes are low in the landscape, whereas smaller lakes with fewer species tend to be high in the landscape.7. By taking a landscape‐scale view, in addition to the more usual lake‐specific view, it is possible to reach a more robust understanding of lake dynamics and avoid some of the problems associated with extrapolating from single lake results.

Photosynthetic rates derived from satellite‐based chlorophyll concentration

We assembled a dataset of 14C‐based productivity measurements to understand the critical variables required for accurate assessment of daily depth‐integrated phytoplankton carbon fixation (PP(PPeu)u) from measurements of sea surface pigment concentrations (Csat)(Csat). From this dataset, we developed a light‐dependent, depth‐resolved model for carbon fixation (VGPM) that partitions environmental factors affecting primary production into those that influence the relative vertical distribution of primary production (Pz)z) and those that control the optimal assimilation efficiency of the productivity profile (P(PBopt). The VGPM accounted for 79% of the observed variability in Pz and 86% of the variability in PPeu by using measured values of PBopt. Our results indicate that the accuracy of productivity algorithms in estimating PPeu is dependent primarily upon the ability to accurately represent variability in Pbopt. We developed a temperature‐dependent Pbopt model that was used in conjunction with monthly climatological images of Csat sea surface temperature, and cloud‐corrected estimates of surface irradiance to calculate a global annual phytoplankton carbon fixation (PPannu) rate of 43.5 Pg C yr‒1. The geographical distribution of PPannu was distinctly different than results from previous models. Our results illustrate the importance of focusing Pbopt model development on temporal and spatial, rather than the vertical, variability.

Primary production of Lake Peipsi-Pihkva

Primary production (PP) in Lake Peipsi-Pihkva, the tripartite border waterbody between Estonia and Russia, was first measured in 1965–1966. Since 1970 there exists a continuous timeseries of monthly PP measurements from May to October. Detailed investigations of the seasonal and daily dynamics as well as the vertical distribution of PP were carried out in 1985–1987. The long-term average values of integral PP (PPint) in Lakes Peipsi and Pihkva were equal (0.8 g C m−2 d−1), although the values per cubic metre (PPmax) differed more than twofold and characterized L. Pihkva as a eutrophic lake and L. Peipsi as a transition type between meso- and eutrophic lakes. The years from 1973 to 1980, 1987 and 1991 were of low productivity, while in 1971, 1983, 1988 and 1990 PP peaks occurred in both lakes. In the seasonal pattern PPint had peaks in May and July. In June, after the spring bloom, PP as well as the chlorophyll a (Chl) and ATP content were low. The high Chl peak in autumn was probably built up by the degradation products of chlorophyll, as neither PP nor ATP increased. Seasonal changes in integral PP in L. Peipsi could be well described (R2 = 0.91) by an empirical model relating PPint to PPmax, Secchi depth (S) and total solar radiation (Q). In mixed conditions prevailing in both lakes, PP was inhibited in the surface layer and its maximum was located at a depth of 0.25...0.5 S. The threshold total solar radiation level for the onset of inhibition was between 1200 and 2000 kJ m−2 h−1 in May and July, and decreased to < 500 kJ m−2 h−1 in October. As a rule, inhibition started in the morning at a higher irradiance than necessary for keeping it up during evening hours. When compared with PPmax, photosynthesis in the surface layer at noon was suppressed by 56% in May, by 45% in July and by 40% in October.

Primary and Bacterial Production in Two Dimictic Indiana Lakes

The relationship between primary and bacterial production in two dimictic Indiana lakes with different primary productivities was examined during the summer stratification period in 1982. Primary production rates were calculated from rates of HCO(3) incorporation by natural samples, and bacterial production was calculated from rates of [H-methyl]thymidine incorporation by natural samples. Both vertical and seasonal distributions of bacterial production in the more productive lake (Little Crooked Lake) were strongly influenced by primary production. A lag of about 2 weeks between a burst in primary production and the subsequent response in bacterial production was observed. The vertical distribution of bacterial production in the water column of the less productive lake (Crooked Lake) was determined by the vertical distribution of primary production, but no clear relationship between seasonal maxima of primary and bacterial production in this lake was observed. High rates of bacterial production in Crooked Lake during May indicate the importance of allochthonous carbon washed in by spring rains. Bacterial production accounted for 30.6 and 31.8% of total (primary plus bacterial) production in Crooked Lake and Little Crooked Lake, respectively, from April through October. High rates of bacterial production during late September and October were observed in both lakes. Calculation of the fraction of bacterial production supported by phytoplankton excretion implies an important role for other mechanisms of supplying carbon, such as phytoplankton autolysis. Several factors affecting the calculation of bacterial production from the thymidine incorporation rates in these lakes were examined.

Vertical distribution of primary production and phytoplankton in two small lakes with different humus concentration in southern Finland

Vertical distribution of primary production and phytoplankton was studied in a polyhumic brownwater lake and in an oligo‐mesohumic lake. During summer both lakes were thermally, chemically and biologically stratified. In the brownwater lake primary production was restricted to the uppermost layer of 1–1.5 m of epilimnion. In the oligo‐mesohumic lake noticeable primary production was detected down to depths of 2–3 m. The ice‐free period primary production was about 20% higher in the oligo‐mesohumic lake, though occasionally the surface production was 2–3 times higher in the brownwater lake. Epilimnetic total phosphorus and total nitrogen concentrations were higher in the brownwater lake, while nitrate‐nitrite, ammonium and phosphate concentrations were very low in both lakes.Phytoplankton was confined to the uppermost productive layer in the brownwater lake. In the oligo‐mesohumic lake phytoplankton was distributed more evenly, though the mean maximum biomass was at the depth of 3–4 m. Below the oxic water layer biomass decreased abruptly in both lakes. In the oligo‐mesohumic lake chlorophyll concentration was extremely high (max. 320 mg chl a m−3) in the anoxic hypolimnion, due to green sulphus bacteria.Flagellated chlorophytes and thrysophytes dominated in the brownwater lake; in spring Chlamydomonas species, followed by Mallomonas caudata. In the oligo‐mesohumic lake small coccal green algae, such as Oocystis, Scenedesmus and Westella‐like species, dominated in mid‐summer, and chrysophytes and cryptomonads in autumn.

Phytoplankton production in relation to physico‐chemical conditions in a small, oligotrophic subarctic lake in South Greenland

Phytoplankton production and physico‐chemical parameters were measured during the summers of 1976 and 1977 in Lake 95 at 60°52′N, 46°01′W (area 8 ha, z 6.9 m). The duration of lake stratification during summer was weather dependent. Concentrations of total‐CO2 ranged from 2.04 mg l−1 (surface) to 4.02 mg l−1 (bottom during stratification). Nutrient concentrations were generally low, and systematic seasonal variation could not be detected with certainty. Vertical distribution of primary production typically showed a distinct maximum followed by a decline with depth. The low production, both per unit area (max. 60 mg C m−2 d−1) and per unit volume (max, 14.3 mg C m−3 d−1), and the annual production of 4.7 g C m−2 classified the lake as extremely oligotrophic.