Biomass of the main elements of the planktonic community in the Equatorial Pacific upwelling

Based on samples with a 140-liter bottles in the upwelling region of the equatorial Pacific, an analysis was made of vertical distribution of various members of the plankton community of organisms (small and large phytoplankton, bacteria, different groups of protozoans, small and large, mainly herbivorous and predatory, animals). There is a distinct vertical divergence between layers of dominance of groups with similar feeding habits against the background of uneven quantitative distribution. Contrariwise, there are masses of consumers in the layers of high concentration of their potential prey.

Synergistic effects of pCO2 and iron availability on nutrient consumption ratio of the Bering Sea phytoplankton community

Little is known concerning the effect of CO2 on phytoplankton ecophysiological processes under nutrient and trace element-limited conditions, because most CO2 manipulation experiments have been conducted under elements-replete conditions. To investigate the effects of CO2 and iron availability on phytoplankton ecophysiology, we conducted an experiment in September 2009 using a phytoplankton community in the iron limited, high-nutrient, low-chlorophyll (HNLC) region of the Bering Sea basin . Carbonate chemistry was controlled by the bubbling of the several levels of CO2 concentration (180, 380, 600, and 1000 ppm) controlled air, and two iron conditions were established, one with and one without the addition of inorganic iron. We demonstrated that in the iron-limited control conditions, the specific growth rate and the maximum photochemical quantum efficiency (Fv/Fm) of photosystem (PS) II decreased with increasing CO2 levels, suggesting a further decrease in iron bioavailability under the high-CO2 conditions. In addition, biogenic silica to particulate nitrogen and biogenic silica to particulate organic carbon ratios increased from 2.65 to 3.75 and 0.39 to 0.50, respectively, with an increase in the CO2 level in the iron-limited controls. By contrast, the specific growth rate, Fv/Fm values and elemental compositions in the iron-added treatments did not change in response to the CO2 variations, indicating that the addition of iron canceled out the effect of the modulation of iron bioavailability due to the change in carbonate chemistry. Our results suggest that high-CO2 conditions can alter the biogeochemical cycling of nutrients through decreasing iron bioavailability in the iron-limited HNLC regions in the future.

(Table 1) Biomass (as energy) of different elements of the planktonic community in the Equatorial Pacific in the 0-150 m layer

An analysis was made of composition and content of nutrients, salts, particulate and dissolved organic matter, and various plankton groups in a series of samples collected by a 140-liter sampling bottle to depth up to 150 m at 4 equatorial stations between 97° and 154°W. Large and small phytoplankton, bacteria (aggregated and dispersed), heterotrophic flagellates, infusorians, radiolarians, foraminifers, fine filter-feeders, small and large, mostly herbivorous copepods, cyclopoids, predatory calanoids, and other predators were investigated separately. Trophic relations between these elements are established from personal and published data, and rate of their metabolism and some other physiological parameters are determined. Such functional characteristics as extent of satisfaction of food requirements of organisms belonging to various trophic groups, intensity of trophic relations, balance between production and consumption by individual elements of the community, ecological efficiency, and net and specific production of the groups distinguished, of individual trophic levels, of total zooplankton, and of the community as a whole are calculated. Variations of these characteristics along the equator with decreasing upwelling intensity are examined and their possible causes and mechanisms are discussed.

(Tables 2) The bPSi:POC ratio of the total diatom community, and abundance of full, empty, and broken diatom cells compared to heavily silicified diatoms during the EIFEX experiment

During the European Iron Fertilisation Experiment (EIFEX), performed in the Southern Ocean, we investigated the reactions of different phytoplankton size classes to iron fertilization, applying measurements of size fractionated pigments, particulate organic matter, microscopy, and flow cytometry. Chlorophyll a (Chl a) concentrations at 20-m depth increased more than fivefold following fertilization through day 26, while concentrations of particulate organic carbon (POC), nitrogen (PON), and phosphorus (POP) roughly doubled through day 29. Concentrations of Chl a and particulate organic matter decreased toward the end of the experiment, indicating the demise of the iron-induced phytoplankton bloom. Despite a decrease in total diatom biomass at the end of the experiment, biogenic particulate silicate (bPSi) concentrations increased steadily due to a relative increase of heavily silicified diatoms. Although diatoms >10 µm were the main beneficiaries of iron fertilization, the growth of small diatoms (2-8 mm) was also enhanced, leading to a shift from a haptophyte- to a diatom-dominated community in this size fraction. The total biomass had lower than Redfield C : N, N : P, and C : P ratios but did not show significant trends after iron fertilization. This concealed various alterations in the elemental composition of the different size fractions. The microplankton (>20 µm) showed decreasing C : N and increasing N : P and C : P ratios, possibly caused by increased N uptake and the consumption of cellular P pools. The nanoplankton (2-20 µm) showed almost constant C : N and decreasing N : P and C : P ratios. Our results suggest that the latter is caused by a shift in composition of taxonomic groups.

Benthic and fish community composition as well as water quality along the Thousand Islands north of the megacity Jakarta, Indonesia

Worldwide, coral reefs are challenged by multiple stressors due to growing urbanization, industrialization and coastal development. Coral reefs along the Thousand Islands off Jakarta, one of the largest megacities worldwide, have degraded dramatically over recent decades. The shift and decline in coral cover and composition has been extensively studied with a focus on large-scale gradients (i.e. regional drivers), however special focus on local drivers in shaping spatial community composition is still lacking. Here, the spatial impact of anthropogenic stressors on local and regional scales on coral reefs north of Jakarta was investigated. Results indicate that the direct impact of Jakarta is mainly restricted to inshore reefs, separating reefs in Jakarta Bay from reefs along the Thousand Islands further north. A spatial patchwork of differentially degraded reefs is present along the islands as a result of localized anthropogenic effects rather than regional gradients. Pollution is the main anthropogenic stressor, with over 80 % of variation in benthic community composition driven by sedimentation rate, NO2, PO4 and Chlorophyll a. Thus, the spatial structure of reefs is directly related to intense anthropogenic pressure from local as well as regional sources. Therefore, improved spatial management that accounts for both local and regional stressors is needed for effective marine conservation.