Some observations on primary production and plankton biomass along the continental shelf and slope off the northeast coast of India during January 1989

The present study deals with the quantitative aspects of chlorophyll pigments, primary productivity and plankton biomass from the continental shelf and slope off the northeast coast of India between 16° and 20°N latitudes towards the end of northeast monsoon season. In surface waters, the mean values of chl-a, -b, and -c were 0.249,0.275 and 0.837 mg/m^ along the shelf and 0.246,0.260 and 0.805 mg/m^ in the slope respectively while the net primary productivity values were 0.074 and 0.081 g C/m /d for the shelf and slope waters respectively. Column productivity in the upper 0-50 m water in the shelf and slope regions were 2.9 and 3.25 g C/m /d with an average production of 3.08 g C/m /d. Higher rate of production was observed around 18° and 20°N latitudes. Zooplankton biomass exhibited progressive increase in volume from 16° to 20°N. The estimated mean zooplankton biomass volume of the study area was 28.83 ml/m . The mean transfer coefficient from primary to secondary production was found to be 14% when 50% of the zooplankton biomass was considered as the daily rate of production. From the mean primary and secondary productivity values, potential tertiary production of pelagic fishery resources in the upper 0-50 m water column of the study area for the month was assessed

Tallaba

Ġabra ta’ poeżiji u proża li tinkludi: Il-Bravi fid-Dar ta’ Luċija ta’ Dun Pawl – X’Qasma ta’ Qalb ta’ C. M. D – Innu ta’ G. M. A. – Ġens il-Malti ta’ R. Briffa – It-Tallaba minn ta’ Matilde Serao ta’ Ġużè Micallef GoggiN/

Assessment of tropical blue carbon reserves in Thailand

University of Technology Sydney. Faculty of Science.Carbon dioxide (CO₂) emission through human activities is one of the most critical issues affecting the entire globe. Among the solutions, carbon sequestration is an important way to reduce atmospheric CO₂. Vegetated coastal habitats – seagrasses, saltmarshes, and mangroves – are among the most effective carbon sinks of the world. These habitats capture and store (sequester) large quanties of organic carbon (Corg), termed ‘blue carbon’. The rapid decline of seagrass in many areas around the world, especially in Southeast Asia has motivated us to study the carbon-sink capacity of tropical Blue Carbon habitats, as well as the impact of the loss of seagrass. This study comprised of three major aims: 1) to investigate the impact of seagrass loss on blue carbon sink capacity; 2) to investigate the influence of seagrass species-specific canopy structure on blue carbon sink capacity; and 3) to investigate the feasibility of using artificial seagrass for blue carbon restoration. Seagrass meadows at Haad Chao Mai National Park, Trang, Thailand trap allochthonous (externally-produced) carbon into sediment reaching up to 90% of Corg stored. At a pristine meadow, seagrass densities play a major role in determining the sediment Corg stock. Seagrass canopy height was found to be not important when comparing Corg sink capacity between Thalassia hemprichii (medium-sized species) and Enhalus acoroides (large-sized species) in this study. On the other hand, seagrass densities influenced the trapping capacity of allochthonous carbon. The sediment organic carbon sources of T. hemprichii and E. acoroides beds for all densities tested were similar (dominated by suspended particulate matter and mangrove for the top 15 cm of sediment). High shoot densities of seagrass could promote the settlement of suspended particles by increasing the chance of particle to contact directly with leaf blade. Seagrass biomass influenced the community metabolism. The Net Community Production (NCP) of seagrass meadows was higher with increased above-ground biomass. NCP measured in meadows with 75% cover of T. hemprichii (104.59 ± 21.72 mmol C m⁻² d⁻¹) and E. acoroides (166.92 ± 12.32 mmol C m⁻² d⁻¹) were higher than these of NCP measured in meadows with 12% cover of T. hemprichii (63.54 ± 5.53 mmol C m⁻² d⁻¹), E. acoroides (78.09 ± 4.63 mmol C m⁻² d⁻¹) and unvegetated sediment (53.36 ± 4.11 mmol C m⁻² d⁻¹). Seagrass loss following elevated sedimentation and increasing water turbidity lead to the loss of 89% of sediment organic carbon (Corg) stock. Loss of seagrass resulted in the loss of allochthonous carbon trapped by the seagrass canopy. Loss of seagrass also altered the sediment grain size distribution. Elevation of coarse grains was found in a denuded site compared to a pristine meadow. About 50% of sediment grain size from the pristine meadow consisted of fine sane (0.125 – 0.25 mm), while 50% of sediment from the pristien meadow consisted of very fine sane (0.0625 – 0.125 mm). The evidence of a weakened blue carbon sink due to seagrass loss was also found as a reduction of carbon sequestration. The level of Net Community Production (NCP) at a denuded site (21.13 ± 8.30 mmol C m⁻² d⁻¹) was lower than the NCP measured at a pristine meadow (53.36 ± 4.11 mmol C m⁻² d⁻¹). While the negative impact of seagrass loss on blue carbon sink capacity was evaluated, artificial seagrass was shown to be an innovative technique to enhance particle- and organic carbon deposition. The particle deposition measured at the denuded site with artificial seagrass was 3-times higher than the particle deposition rate measured at the denuded site without artificial seagrass. The organic carbon trapped by artificial seagrass was 12-times higher than occurred at these denuded sites without artificial seagrass. There was no significant difference in the particle deposition rate and organic carbon deposition rate between an artificial seagrass experiment and the natural pristine seagrass meadows. Thus, artificial seagrass is an effective tool to recover blue carbon sink capacity where the allaochthonous carbon is a major carbon source, artificial seagrass is an effective tool in the recovery of blue carbon sink capacity – it enables a more rapid recovery and requires less effort than other restoration techniques.For better estimates of blue carbon sink capacity, seagrass abundance was recommended as an appropriate monitoring indicator because it influences the sediment Corg stock, while species-specific canopy height did not play an important role determining sediment Corg stock in this particular study

Heterotrophic bacterial production in the eastern South Pacific: longitudinal trends and coupling with primary production

Spatial variation of heterotrophic bacterial production and phytoplankton primary production were investigated across the eastern South Pacific Ocean (−141° W, −8° S to −72° W, −35° S) in November–December 2004. Bacterial production (³H leucine incorporation) integrated over the euphotic zone encompassed a wide range of values, from 43 mg C m⁻² d⁻¹ in the hyper-oligotrophic South Pacific Gyre to 392 mg C m⁻² d⁻¹ in the upwelling off Chile. In the gyre (120° W, 22° S) records of low phytoplankton biomass (7 mg Total Chla m⁻²) were obtained and fluxes of in situ 14C-based particulate primary production were as low as 153 mg C m⁻² d⁻¹, thus equal to the value considered as a limit for primary production under strong oligotrophic conditions. Average rates of ³H leucine incorporation rates, and leucine incorporation rates per cell (5–21 pmol l⁻¹ h⁻¹ and 15–56×10⁻²¹ mol cell⁻¹ h⁻¹, respectively) determined in the South Pacific gyre, were in the same range as those reported for other oligotrophic subtropical and temperate waters. Fluxes of dark community respiration, determined at selected stations across the transect varied in a narrow range (42–97 mmol O2 m⁻² d⁻¹), except for one station in the upwelling off Chile (245 mmol O2 m⁻² d⁻¹). Bacterial growth efficiencies varied between 5 and 38%. Bacterial carbon demand largely exceeded 14C particulate primary production across the South Pacific Ocean, but was lower or equal to gross community production

Primary production of phytoplankton in the three types of Amazonian waters. V. Some investigations on the phytoplankton and its primary productivity in the clear water of the lower Rio Tapajós (Pará, Brazil)

Four limnological investigations were conducted in different seasons of the years 1968 and 1969 at the lower reaches of the Rio Tapajóz. The physical and chemical parameters generally correspond with earlier findings of other authors. Midriver areas show no stratification of the water body. In certain reaches of the river, distinct increases of pH-values temporarily occur due to strong phytoplankton activity. A few species of cyanophyceae and diatomeae make up the vast majority of phytoplankton in terms of nu,bers. Chlorophyceae, desmidiaceae, and other algae are characterized by high species variety but only occur in low or moderate densities. Despite of the low nutrient concentrations encountered, phytoplankton production is high, which can be attributed to the excellent light conditions in the river. The net production of 2.4 g C/m²/d exceeds by far production rates from várzea-lakes, although production densities are lower. A mighty productive zone in combination with extremely fast turn over rates male this unexpected high production per unit area possible. The shortest C turn over time of all samples was 0.3 days. Phytoplankton net production amounts to a calculated 5 t C hectare and year. Derived from primary production data, a theoretical fish production of 100 kg/ha/year can be estimated, which would allow yearly catches of at least 10 to 20 kg per hectare for human consumption without provocing ecological disturbances

Primary production of phytoplankton in the three types of Amazonian waters. III. Primary productivity of phytoplankton in a tropical flood-plain lake of Central Amazonia, Lago do Castanho, Amazonas, Brasil

The primary productivity of phytoplankton in Lago do Castanho is characterized by a high production density (production per unit volume g C/m³). Because of unfavourable optical conditions in the water body, however, the thickness of the productive area is generally small. It fluctuated according to the season between 6 m and less than 0,5 m. Seasonal differences occur in the productivity per unit volume and area. In the lower water phase, between October and November, the production density reaches its maximum of net 2,15 g C/m³/d. The corresponding minimum value was 0,32 g C/m³/d and was measured in the period of influx of turbid river water into the lake basin, which dilutes the phytoplankton densities further on. This phase lasted from January till May. The area production i.e. the production per unit area, reached its maximum at high water when inflow of river water had ceased. This phase lasted from around the middle of May till the end of September. The highest value of production per unit area in Lago do Castanho was 1,5 g C/m²/d. The annual mean net productivity amounted to 0,8 g C/m²/d. The gross production per m was around 25-40% greater than the corresponding net production. Within the same season the noticeable fluctuations in production varied only slightly from day to day. Photosynthesis of phytoplankton showed clear daytime differences. It was lower in two tests between 14 and 18 h than between 6-10 h and 10-14 h. The portion of the dark fixation of C(14) fluctuated between 1-6% of the C(14) fixation in light bottles. In the year between the end of August 1967 and the end of August 1968 the net productivity of phytoplankton in Lago do Castanho amounted to approximately 3 t C/ha. The corresponding gross production was approximately 3,9 t C/ha. On the basis of chlorophyll data of the trophogenic zone - the average was 0,052 mg/l - a mean C content of 0,8 mg/t bound in phytoplankton was calculated, opposed to 10 - 15 mg total C/t dissolved and suspended C compounds in the water. The mean algal biomass calculated from the chlorophyll data was, in the trophogenic zone, 1,9 g C/m² and 3,8 g ash free dry weight/m². From this algal biomass and the average gross productivity of about 1,1 g C/m²/d, a mean C turnover rate of approximately 1,7 days was deduced for the trophogenic zone. Altogether the results showed that in Lago do Castanho, as a type of tropical inland lake fed by white water, the most important factor controlling primary production of phytoplankton is the light which primarily limits it rather than the nutrient content in the water. In a discussion of the conditions of production determined for Lago do Castanho, they are compared with other tropical inland waters. In this connection, it is apparent that this lake can be placed with other higher productive waters, that however a production as high as it was found in some tropical waters which are eutrophicated more or less due to human influence cannot be achieved in Lago do Castanho. The production per surface area in Lago do Castanho is mainly limited by the unfavourable optical conditions, the water being especially characterized by high contents of mineral and organic detritus. On the basis of the primary production of phytoplankton in Lago do Castanho, one can expect a fish production of at least 60 kg per hectare per year. Considering the portions of the littoral and terrestrial environment, an estimate of an average yearly fish production of 100-150 kg/ha seems realistic. In conclusion, a short discussion of the possibilities for raising the primary production and thus fish production is given