Phytoplankton community structure and productivity in relation to the hydrological regime of the Gulf of Carpentaria, Australia, in summer

To describe the influence of hydrology on the phytoplankton communites of the Gulf of Carpentaria, six phytoplankton parameters were measured on five transects: productivity, biomass, community structure, phospholipid-derived fatty acids, ratios of stable carbon isotopes and the relationship between photosynthesis and irradiance. The mean (�s.e.) estimate of depth-integrated phytoplankton productivity was 914�185 mgC m-2 day-' (n=9). In the shallow (<30 m) coastal waters, the productivity was 1430�400 mgC m-2 day-1 (n = 3). At the offshore stations (=30 m), it was 660 �108 mgC m-2 day-1 (n = 6). At both the shallow and the offshore stations, primary productivity was distributed equally between the phytoplankton size fractions 0.6-2.0�m and > 10�m, with little in between. The highest rates of growth occurred within a very narrow light regime: self-shading limited growth in deeper water (at light intensities less than 125 mol s-1 m-2), and growth was photoinhibited in shallow water (at light intensities greater than 150 mol s-1 m-2). The resulting biomass-specific primary productivity (mgC mChla-1 day-1) maximum did not coincide with the depth of either the chlorophyll a maximum or the highest nutrient concentration. The natural carbon isotope ratio for the particulate matter showed that little land-derived carbon was exported beyond a narrow coastal fringe (about 10 to 20 km). The profiles of phospholipid fatty acids also showed that particulate organic matter was dominated by algal-derived compounds, which confirms that the bulk of the organic matter in the offshore Gulf of Carpentaria is of marine origin. Therefore, during the summer in this study, the stratified waters of the central gulf were both biologically and hydrologically independent of the coastal water and not influenced by terrestrial runoff. The phytoplankton production in the central gulf is maintained by nutrient supplies from internal sources, such as those that are remineralized in and resuspended from the sediment.

Download Full-text

Exploring the use of compound-specific carbon isotopes as a palaeoproductivity proxy off the coast of Adélie Land, East Antarctica

Biogeosciences ◽

10.5194/bg-18-5555-2021 ◽

2021 ◽

Vol 18 (19) ◽

pp. 5555-5571

Author(s):

Kate E. Ashley ◽

Xavier Crosta ◽

Johan Etourneau ◽

Philippine Campagne ◽

Harry Gilchrist ◽

...

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Carbon Isotopes ◽

Coastal Zone ◽

Primary Productivity ◽

Open Water ◽

Phytoplankton Productivity ◽

Antarctic Sea Ice ◽

Projected Changes ◽

The Antarctic

Abstract. The Antarctic coastal zone is an area of high primary productivity, particularly within coastal polynyas, where large phytoplankton blooms and drawdown of CO2 occur. Reconstruction of historical primary productivity changes and the associated driving factors could provide baseline insights on the role of these areas as sinks for atmospheric CO2, especially in the context of projected changes in coastal Antarctic sea ice. Here we investigate the potential for using carbon isotopes (δ13C) of fatty acids in marine sediments as a proxy for primary productivity. We use a highly resolved sediment core from off the coast of Adélie Land spanning the last ∼ 400 years and monitor changes in the concentrations and δ13C of fatty acids along with other proxy data from the same core. We discuss the different possible drivers of their variability and argue that C24 fatty acid δ13C predominantly reflects phytoplankton productivity in open-water environments, while C18 fatty acid δ13C reflects productivity in the marginal ice zone. These new proxies have implications for better understanding carbon cycle dynamics in the Antarctica coastal zone in future palaeoclimate studies.

Download Full-text

Bacterial communities in temperate and polar coastal sands are seasonally stable

ISME Communications ◽

10.1038/s43705-021-00028-w ◽

2021 ◽

Vol 1 (1) ◽

Author(s):

Sebastian Miksch ◽

Mirja Meiners ◽

Anke Meyerdierks ◽

David Probandt ◽

Gunter Wegener ◽

...

Keyword(s):

Organic Matter ◽

Community Structure ◽

Bacterial Communities ◽

Temporal Stability ◽

Carbon Mineralization ◽

High Temporal Resolution ◽

Phytoplankton Productivity ◽

Annual Cycles ◽

Cell Counts ◽

Dividing Cells

AbstractCoastal sands are biocatalytic filters for dissolved and particulate organic matter of marine and terrestrial origin, thus, acting as centers of organic matter transformation. At high temporal resolution, we accessed the variability of benthic bacterial communities over two annual cycles at Helgoland (North Sea), and compared it with seasonality of communities in Isfjorden (Svalbard, 78°N) sediments, where primary production does not occur during winter. Benthic community structure remained stable in both, temperate and polar sediments on the level of cell counts and 16S rRNA-based taxonomy. Actinobacteriota of uncultured Actinomarinales and Microtrichales were a major group, with 8 ± 1% of total reads (Helgoland) and 31 ± 6% (Svalbard). Their high activity (frequency of dividing cells 28%) and in situ cell numbers of >10% of total microbes in Svalbard sediments, suggest Actinomarinales and Microtrichales as key heterotrophs for carbon mineralization. Even though Helgoland and Svalbard sampling sites showed no phytodetritus-driven changes of the benthic bacterial community structure, they harbored significantly different communities (p < 0.0001, r = 0.963). The temporal stability of benthic bacterial communities is in stark contrast to the dynamic succession typical of coastal waters, suggesting that pelagic and benthic bacterial communities respond to phytoplankton productivity very differently.

Download Full-text

Warming and elevated CO2 promote incorporation of plant-derived lipids into soil organic matter in a spruce-dominated ombrotrophic bog

10.5194/egusphere-egu21-1118 ◽

2021 ◽

Author(s):

Ofiti O.E. Nicholas ◽

Zosso U. Cyrill ◽

Solly F. Emily ◽

Hanson J. Paul ◽

Wiesenberg L.B. Guido ◽

...

Keyword(s):

Fatty Acids ◽

Organic Matter ◽

Soil Organic Matter ◽

Land Surface ◽

Stable Carbon Isotopes ◽

Specific Response ◽

Microbial Decomposition ◽

Short Period ◽

Bulk Organic Matter ◽

The Impact

More than one third of global soil organic matter (SOM) is stored in peatlands, despite them occupying less than 3% of the land surface. Increasing global temperatures have the potential to stimulate the decomposition of carbon stored in peatlands, contributing to the release of disproportionate amounts of greenhouse gases to the atmosphere but increasing atmospheric CO2 concentrations may stimulate photosynthesis and return C into ecosystems. &#160;Key questions remain about the magnitude and rate of these interacting and opposite processes to environmental change drivers.We assessed the impact of a 0&#8211;9&#176;C temperature gradient of deep peat warming (4&#160;years of warming; 0-200 cm depth) in ambient or elevated CO2 (2 years of +500 ppm CO2 addition) on the quantity and quality of SOM at the climate change manipulation experiment SPRUCE (Spruce and Peatland Responses Under Changing Environments) in Minnesota USA. We assessed how warming and elevated CO2 affect the degradation of plant and microbial residues as well as the incorporation of these compounds into SOM. Specifically, we combined the analyses of free extractable n-alkanes and fatty acids together with measurements of compound-specific stable carbon isotopes (&#948;13C).We observed a 6&#8240; offset in &#948;13C between bulk SOM and n-alkanes, which were uniformly depleted in &#948;13C when compared to bulk organic matter. Such an offset between SOM and n-alkanes is common due to biosynthetic isotope fractionation processes and confirms previous findings. After 4&#160;years of deep peat warming, and 2 years of elevated CO2 addition a strong depth-specific response became visible with changes in SOM quantity and quality. In the upper 0-30 cm depth, individual n-alkanes and fatty acid concentrations declined with increasing temperatures with warming treatments, but not below 50 cm depth. In turn, the &#948;13C values of bulk organic matter and of individual n-alkanes and fatty acids increased in the upper 0-30 cm with increasing temperatures, but not below 50 cm depth. Thus n-alkanes, which typically turnover slower than bulk SOM, underwent a rapid transformation after a relatively short period of simulated warming in the acrotelm. Our results suggest that warming accelerated microbial decomposition of plant-derived lipids, leaving behind more degraded organic matter. The non-uniform, and depth dependent warming response implies that warming will have cascading effects on SOM decomposition in the acrotelm in peatlands. It remains to be seen how fast the catotelm will respond to rising temperatures and atmospheric CO2 concentrations.

Download Full-text

Fatty acid carbon isotopes: a new indicator of marine Antarctic paleoproductivity?

10.5194/bg-2020-124 ◽

2020 ◽

Author(s):

Kate Ashley ◽

James Bendle ◽

Xavier Crosta ◽

Johan Etourneau ◽

Philippine Campagne ◽

...

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Carbon Isotopes ◽

Coastal Zone ◽

Primary Productivity ◽

Open Water ◽

Phytoplankton Productivity ◽

Antarctic Sea Ice ◽

Projected Changes ◽

The Antarctic

Abstract. The Antarctic coastal zone is an area of high primary productivity, particularly within coastal polynyas where large phytoplankton blooms and drawdown of CO2 occur. Reconstruction of historical primary productivity changes, and the associated driving factors, could provide baseline insights on the role of these areas as sinks for atmospheric CO2, especially in the context of projected changes in coastal Antarctic sea ice. Here we investigate the potential for using carbon isotopes (δ13C) of fatty acids in marine sediments as a proxy for primary productivity. We use a highly resolved sediment core from off the coast of Adélie Land spanning the last ~ 400 years and monitor changes in the concentrations and δ13C of fatty acids along with other proxy data from the same core. We discuss the different possible drivers of their variability and argue that C24 fatty acid δ13C predominantly reflects phytoplankton productivity in open water environments, while C18 fatty acid δ13C reflects productivity in the marginal ice zone. These new proxies have implications for better understanding carbon cycle dynamics in the Antarctica coastal zone in future paleoclimate studies.

Download Full-text

By-products as an amendment of a mine soil: effects on microbial biomass determined using phospholipid fatty acids

Spanish Journal of Soil Science ◽

10.3232/sjss.2018.v8.n1.01 ◽

2018 ◽

Vol 8 ◽

Author(s):

Vanesa Santás-Miguel ◽

Laura Cutillas-Barreiro ◽

Juan Carlos Nóvoa-Muñoz ◽

Manuel Arias-Estévez ◽

Montserrat Díaz-Raviña ◽

...

Keyword(s):

Fatty Acids ◽

Organic Matter ◽

Community Structure ◽

Microbial Biomass ◽

Fungal Biomass ◽

Phospholipid Fatty Acids ◽

Pine Bark ◽

Mine Soil ◽

Mussel Shell ◽

By Products

In the present work, the effect of two by-products (pine bark and crushed mussel shell) on microbial biomass and community structure was studied in a soil from a mine tailing located in a copper mine. In a laboratory experiment, different doses (0, 12, 24, 48, 96 and 192 Mg ha-1) of pine bark, crushed mussel shell or mixtures of both by-products were added to the soil. The amended soil samples were incubated for one year at 60% of water holding capacity, and then 33 phospholipid fatty acids (PLFAs) were extracted from these samples and quantified. The PLFAs concentrations were used for different microbial biomass estimations: total biomass, bacterial biomass, fungal biomass, gram-positive (G+) biomass and gram-negative (G-) biomass. The addition of crushed mussel had no significant effects on the total soil microbial biomass, either bacterial of fungal biomass. However, the addition of pine bark increased the total microbial biomass in the soil (up to 40%), mainly due to increases in the fungal biomass (it increased 1600%). No synergistic effects were observed when the soil was amended with both, pine bark and crushed mussel shell. The main community structure changes were due to the addition of pine bark to the soil, and were also due to modifications in fungal communities. Our results suggest that the microbial biomass was mainly limited in the mine soil by low organic matter concentrations, and therefore, practices increasing the amount of soil organic matter should be priorities for soil reclamation.

Download Full-text

Sources of Organic Matter for Reservoir Fish Production: A Trophic-Dynamics Analysis

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f83-170 ◽

1983 ◽

Vol 40 (9) ◽

pp. 1480-1495 ◽

Cited By ~ 53

Author(s):

S. M. Adams ◽

B. L. Kimmel ◽

G. R. Ploskey

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Food Webs ◽

Fish Community ◽

Trophic Dynamics ◽

Phytoplankton Production ◽

Fish Production ◽

Allochthonous Organic Matter ◽

Phytoplankton Productivity ◽

Carbon Supply

A trophic-dynamics approach was used to examine the relationships of phytoplankton production, other autochthonous primary producers, and allochthonous organic matter to the organic carbon supply necessary to support the fish community production in 17 southeastern and midwestern U.S. reservoirs. Fish community carbon requirements were estimated using average efficiencies of 10 and 15% per trophic transfer to bracket the range of efficiencies that probably occur in reservoir food webs. At 10% efficiency, most of the reservoir food webs considered appeared to be supplemented significantly by allochthonous organic matter. At 15% efficiency, phytoplankton production accounted for the organic carbon required for fish production in 10 of the 17 reservoirs. In this case, supplementary organic carbon sources were invoked to meet fish production requirements in the remaining seven reservoirs. Our results suggest that, depending on the actual food web efficiencies, autochthonous primary production can often account for the organic carbon supply required for reservoir fish production and that the importance of allochthonous organic matter to reservoir biological productivity may have been previously overemphasized. Although both the morphoedaphic index (MEI) and phytoplankton productivity were strongly correlated with reservoir fish production, a simple relationship does not appear to exist between the MEI and phytoplankton productivity, probably because of the complex aggregate nature of the MEI descriptor.

Download Full-text

Impacts of long-term plant residue management on soil organic matter quality, Pseudomonas community structure and disease suppressiveness

Soil Biology and Biochemistry ◽

10.1016/j.soilbio.2019.05.020 ◽

2019 ◽

Vol 135 ◽

pp. 396-406 ◽

Cited By ~ 7

Author(s):

Bryony E.A. Dignam ◽

Maureen O'Callaghan ◽

Leo M. Condron ◽

Jos M. Raaijmakers ◽

George A. Kowalchuk ◽

...

Keyword(s):

Organic Matter ◽

Community Structure ◽

Soil Organic Matter ◽

Residue Management ◽

Plant Residue ◽

Organic Matter Quality ◽

Soil Organic Matter Quality

Download Full-text

Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs

Scientific Reports ◽

10.1038/s41598-021-95742-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Pianpian Wu ◽

Martin J. Kainz ◽

Fernando Valdés ◽

Siwen Zheng ◽

Katharina Winter ◽

...

Keyword(s):

Climate Change ◽

Fatty Acids ◽

Organic Matter ◽

Food Webs ◽

Essential Fatty Acids ◽

Trophic Levels ◽

Climate Change Scenarios ◽

Essential Nutrients ◽

Aquatic Food Webs ◽

Aquatic Food

AbstractClimate change scenarios predict increases in temperature and organic matter supply from land to water, which affect trophic transfer of nutrients and contaminants in aquatic food webs. How essential nutrients, such as polyunsaturated fatty acids (PUFA), and potentially toxic contaminants, such as methylmercury (MeHg), at the base of aquatic food webs will be affected under climate change scenarios, remains unclear. The objective of this outdoor mesocosm study was to examine how increased water temperature and terrestrially-derived dissolved organic matter supply (tDOM; i.e., lake browning), and the interaction of both, will influence MeHg and PUFA in organisms at the base of food webs (i.e. seston; the most edible plankton size for zooplankton) in subalpine lake ecosystems. The interaction of higher temperature and tDOM increased the burden of MeHg in seston (< 40 μm) and larger sized plankton (microplankton; 40–200 μm), while the MeHg content per unit biomass remained stable. However, PUFA decreased in seston, but increased in microplankton, consisting mainly of filamentous algae, which are less readily bioavailable to zooplankton. We revealed elevated dietary exposure to MeHg, yet decreased supply of dietary PUFA to aquatic consumers with increasing temperature and tDOM supply. This experimental study provides evidence that the overall food quality at the base of aquatic food webs deteriorates during ongoing climate change scenarios by increasing the supply of toxic MeHg and lowering the dietary access to essential nutrients of consumers at higher trophic levels.

Download Full-text