The pigment complex and photosynthetic activity in the annual cycle of Polytrichum commune in the forest belt of the Khibiny Mountains on the Kola Peninsula of Russia

This paper presents data on the content and ratio of pigments, photosynthesis rate, and assimilation number throughout the annual cycle of Polytrichum commune in the forest belt of the Khibiny Mountains. It is shown that the activity of the pigment complex in the photosynthetic organs of P. commune is preserved and maintained over 2 years. The highest content of plastid pigments in this year’s shoots was recorded in fall, in the past year’s shoots in the summer. In winter, the content of chlorophylls in the photosynthetic organs of this year’s shoots decreased in 1.5 times relative to the summer maximum, and carotenoids - in 1.4 times. In the past year’s shoots, no significant changes in the content of the pigments were noted. During the active vegetation period, the photosynthetic intensity in this year’s shoots is in 1.5 times as high as that in the past year’s shoots. At the end of the growing season in the past year’s shoots the value of LHC (76%) due to their immersion deep into the moss clumps and shading them with this year’s shoots. Chlorophyll’s efficiency (assimilation number) in P. commune shoots of different ages in early spring (April) is in 2 times as high as that in fall (October).

Estimation of primary production in the northwestern part of the Sea of Japan by ship- and satellite-based observations

In this paper, we analyzed data of POI FAB RAS cruise (No. 33) held on «Akademik M.A. Lavrentyev» vessel in the northwestern part of the Japan Sea in May 2004 and compared them with satellite derived data from Climate Change Initiative Ocean Colour (CCI-OC) and Ocean productivity databases. The following in situ data were used for the analysis: CTD-data, assimilation number, nutrients (P, N, Si) and chlorophyll a (Chl). Ship assessments of Chl in the first optical layer were in average 0.5±0.58 mg/m3, while satellite Chl were nearly twice more – 0.95±0.36 mg/m3. Ship assessments of primary production (PP) were 1870±900 mg C/m2day that is 1.5 times larger than satellite derived data - 1226±432. Vertical profiles of nutrients, temperature and Chl showed that main mass of Chl was concentrated in a layer from 20 to 45 m, where the main production is formed. According to values of assimilation number, main production formed in a layer of 0-55 m in the south of the region and 0-30 m in the north. Weak correlation between ship and satellite PP values found in this paper may be explained by low accuracy of satellite derived estimation.

Evaluation of primary production in the northeastern Japan Sea on the base of shipboard and satellite data

Satellite data on chlorophyll concentration from ESA (CCI-OC) and Goddard Space Flight Center, NASA and shipboard observations of CTD, P, N, Si, inorganic carbon, DCI, and Chlaat 38 stations in the northeastern Japan Sea (46th cruise of RV Academik M.A. Lavrentyev on July 9–19, 2009) are analyzed. The highest chlorophyll concentrations were found in the subsurface layer (depth 20–40 m) or even deeper in the Polar Front zone, so they were not reflected in the satellite data. The minimal depths of the subsurface maximum were observed northward from the Polar Front where the estimations of chlorophyll concentration in the upper optical layer (Zd= 1/kd) were similar for the shipboard and satellite measurements (on average 0.384 ± 0.160 mg/m3 and 0.406 ± 0.120 mg/m3, respectively). Primary production was calculated using the assimilation number 4.46 mgC/mgChl per hour. Depth of euphotic layer was estimated using the vertical profles of nutrients and Chla. Within this layer, the primary production in the northeastern Japan Sea was evaluated for the shipboard stations as 895–2275 mgС.m–2.day–1, on average 1450 ± 430 mgС.m–2.day–1, and for the satellite data on average 770 ± 190 mgС.m–2.day–1. The estimations based on the shipboard and satellite data were weakly correlated. The shipboard estimations exceed considerably the results obtained by Koblents-Mishke et al. (1956, 1970) and Yamada et al. (2005). Poor accuracy of satellite estimations of primary production is concluded because the deeper part of the euphotic layer with the maximum concentration of chlorophyll is in shadow for satellite sensors.

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.

Mass Appearance of Cyanobacterium Planktothrix rubescens in Lake Piaseczno, Poland

In 1989, Lake Piaseczno, Poland, exhibited a mass appearance of Planktothrix rubescens. During this time the pelagic and littoral areas exhibited significant increases in areal primary production (400 and 41 mg C m-2 h-1, respectively), chlorophyll α (100 and 6.9 mg m-2, respectively) and assimilation number (4 and 5.9 mg C m-2 h-1/mg chlα m-2, respectively). After the water bloom subsided, a reduction of dissolved oxygen concentration (down to 1.5 mg L-1) and high water temperature (10.2°C) in the offshore bottom zone was observed. While from 1991 to 1996, the primary production, chlorophyll α concentration and assimilation number values were decreasing, they were significantly higher than the values reported in 1986, prior to the mass cyanobacteria appearance. An indirect correlation with ion levels indicated that the outbreak of the cyanobacteria was linked with inflow of nutrients from the catchment area. The dramatic changes in the range and variability of the phytoplankton density indicate that the recent eutrophication of the lake has had profound effects on the structure and productivity of the aquatic community.

Productivity of the Psammic Algal Communities in the Near-Shore Zone of the Mesotrophic Lake Piaseczno (Eastern Poland)

From 1986 to 1998, the primary productivity of psammic algae was investigated in the psammolittoral of Lake Piaseczno, a mesotrophic lake. The oxygen method was developed for the direct measurement of primary production of these algae based on light and dark bottles without disturbing the subsoil structure. This productivity was also estimated in an indirect way by measurement of chlorophyll a concentrations. The productivity of phytoplankton was also measured in the same zone. The correlation between the productivity of algae and the concentration of nutrients and major ions in water was calculated. During the study period, the highest production was found in the eupsammon (31.1 to 187.7 Cass·m-2·h-1), with the hydropsammon being lower (9.6 to 100.6 Cass·m-2·h-1). For phytoplankton biomass, the numbers were very low, which is typical of pristine lakes. The chlorophyll a concentration during the study period demonstrated a different pattern ranging from 53 mg·m-2 in the hydropsammon to 765 mg·m-2 in the eupsammon. The assimilation number for these communities was always <1. A positive (r >0.4) correlation was found between the primary production of the eupsammon and the psammolittoral phytoplankton, and the concentration of NH4-N, NO3-N, Ntot, PO4-P, Ptot. and K+ in the piezometer groundwater. No correlation was found between primary production, chlorophyll a concentration and the concentration of nutrients and major ions in the piezometer groundwater and psammolittoral water.

Dynamics of Lake Michigan Phytoplankton: Primary Production and Growth

Primary production was measured with the 14C technique during May through July–August 1982–84. 14C experiments varied from short-term incubations (1–2 h) in a photosynthesis–irradiance (P–I) chamber to 24-h in situ incubations. The maximum assimilation number from six P–I experiments during thermal stratification averaged 2.1 mg C∙mg Chl−1∙h−1 which agreed well with estimates from the 1970s. Chlorophyll-corrected P–I curves were combined with incident irradiation, chlorophyll concentrations, and extinction coefficients to estimate daily production (model estimate). Summer average integral production estimates in 1983 and 1984 were 615–630 mg C∙m−2∙d−1. Approximately 50% of summer primary production occurred below the epilimnion. Daily model production estimates were higher than 24-h in situ estimates at light intensities above Ik, the light saturation parameter, and similar at intensities below Ik. Comparisons of production estimates converted to growth rates suggest that 24-h in situ estimates provide a measure close to net production whereas model estimates provide a measure greater than net production. Summer epilimnetic growth rate estimates were low (range 0.06–0.60∙d−1), reflecting the limited availability of phosphorus.