Feeding of benthic foraminifera on diatoms and sewage-derived organic matter: an experimental application of lipid biomarker techniques

Foraminiferal ecology at sewage outfalls has been investigated in numerous field studies over the last 30 years. Foraminifera have been frequently used as biomonitors of sewage pollution since they are both abundant and ubiquitous. Sewage outfalls have been demonstrated to have both positive and negative effects on adjacent foraminiferal populations, but it has never been shown conclusively why sewage affects foraminifera in these ways. Such information on the impact mechanisms of sewage pollution is essential if foraminifera are to be used as sewage pollution biomonitors, and also to understand the ecology of these important protists. One possible cause of a positive effect is the direct consumption of sewage-derived particulate organic matter (POM) by the foraminifera themselves. However this hypothesis has never been tested experimentally. Here, lipid (fatty acid and sterol) biomarker techniques were applied to study the ingestion of two potential food items by the foraminiferan Haynesina germanica in the laboratory. An experiment was conducted to confirm that the laboratory conditions were conducive to the survival and feeding of the foraminifera. In this experiment, foraminifera were provided with the pennate diatom Phaeodactylum tricornutum, which was considered to be a suitable food source. After 2 weeks, a four-fold increase in the levels of the diatom fatty acid biomarker, 20:5(n-3), in the foraminifera suggested that they had fed actively on the diatoms and survived under the experimental conditions. These experimental conditions were used in the main experiment, where foraminifera were fed the POM from sewage. Lipid biomarker analysis indicated that H. germanica did not consume secondary treated sewage-derived POM. Neither fatty acid profiles in the sewage nor coprostanol, the diagnostic human faecal sterol, were detected in foraminifera after exposure to the potential sewage food source. However, foraminifera may have consumed bacteria associated with the sewage in the experiment. The findings are discussed in terms of current EU legislation on sewage treatment that has affected the composition of sewage discharges, and therefore possibly reduced the nutritive value of sewage to the marine benthos.     

The effects of oil exploration and production in the northern North Sea: Part 2—microbial biodegradation of hydrocarbons in water and sediments, 1978–1981

The potential of heterotrophs to degrade aromatic hydrocarbons derived from oil in water and sediments in the northern North Sea around the Brent, Beryl, Forties and Murchison oilfields and at a number of stations, from the Forties field to the Firth of Forth, was estimated using 1-¹⁴C naphthalene and 7, 10-¹⁴C benzo(a)pyrene. The degradation of uniformly labelled ¹⁴C mixed 1-amino acids was used as a measure of total heterotrophic activity. Results showed that microorganisms have the potential to degrade the smaller aromatic hydrocarbon molecules rapidly in the water column and in surface sediments. Close to the Beryl platform, where diesel-washed drill cuttings have been continuously dumped, the rate of input of hydrocarbons to the sediment has exceeded the rate of degradation. Mineralization of benzo(a)pyrene, estimated in the sediments only, was minimal. Close to production platforms the biodegradation rate of mixed 1-amino acids showed no increase comparable with that found for naphthalene, suggesting that existing microbial populations had not increased but adapted to degrade oil in water and sediments.     

An evaluation of systems for the integrated assessment of capture fisheries

Integrated fishery assessments are intended to take an integrated and wholistic view of fisheries management, to provide comprehensive systems-based evaluations of the sustainability of individual fisheries and their products. Using guidance derived from decision theory and management science, we develop 18 criteria to evaluate the likely effectiveness of nine integrated fishery assessment systems. The assessment systems do not consistently consider four key criteria: the socio-economic impacts of fisheries, the provision of food security, the local relevance of the assessment to the fishery under assessment, and the independent peer review of assessment outcomes. Other important areas of weakness include the lack of appropriate consultation processes relating to both the design of the assessment system and the outcomes of fishery assessments, and limitations in the quality of data and information used in assessments. Improvements will be needed in these areas across all the systems we evaluated if fishers, consumers, managers and other stakeholders are to be provided with consistently reliable assessment outcomes, and an assurance of the sustainability of capture fisheries.     

Distributions of dissolved and particulate biogenic thiols in the subartic Pacific Ocean

Dissolved and particulate concentrations of the biogenic thiols cysteine (Cys), arginine–cysteine (Arg–Cys), glutamine–cysteine (Gln–Cys), γ-glutamate–cysteine (γ-Glu–Cys) and glutathione (GSH) were measured in the subartic Pacific Ocean in the summer of 2003 using high performance liquid chromatography (HPLC) with precolumn derivatization as reported in previous work. In this study, a preconcentration protocol for the derivatized thiols was utilized to extend detection limits of dissolved thiols to picomolar levels. The measured concentrations of particulate and dissolved thiols were uncoupled, with distinctive depth profiles and large differences in the particulate to dissolved ratios between individual compounds. Glutathione was the most abundant particulate thiol whereas the most abundant dissolved thiol was γ-Glu–Cys, with concentrations as high as 15 nM. Given the relatively small pool of intracellular γ-Glu–Cys and the very low dissolved concentrations of GSH, we hypothesize that glutathione released from cells is rapidly converted to the potentially degradation resistant γ-Glu–Cys outside the cell. The relatively high concentrations of other dissolved thiols compared to particulate concentrations implies both biological exudation and slow degradation rates. Some thiols appear to vary with changes in nutrient availability but this effect is difficult to decouple from changes in community structure inferred from pigment analyses. Dissolved thiol concentrations also exceed typical metal concentrations in the subartic Pacific, supporting previous arguments that they may be important in metal speciation.     

Gravity field analysis of Sio Guyot: An isostatically compensated seamount in the Mid-Pacific Mountains

Positive gravity anomalies indicate two dense conduits or eruptive centers beneath the northern summit of Sio Guyot, western Mid-Pacific Mountains. The low amplitude of the positive anomalies and the gravity lows flanking the guyot can be explained by crust 2.5 times the normal Pacific Ocean crustal thickness extending to a depth of 22 ± 2 km. The excess mass of the seamount is 100% locally isostatically compensated by the mass deficit below; this compensation may result from flexural loading and voluminous sill injection near a former ridge-crest transform fault system trending roughly ENE and NNW.     

Thermodynamic characterization of the partitioning of iron between soluble and colloidal species in the Atlantic Ocean

Recent electrochemical measurements have shown that iron (Fe) speciation in seawater is dominated by complexation with strong organic ligands throughout the water column and have provided important thermodynamic information about these compounds. Independent work has shown that iron exists in both soluble and colloidal fractions in the Atlantic Ocean. Here we have combined these approaches in samples collected from a variety of regimes within the Atlantic Ocean. We measured the partitioning of Fe between soluble (< 0.02 μm) and colloidal (0.02 to 0.4 μm) size classes and characterized the concentrations and conditional stability constants of Fe ligands within these size classes. Results suggest that equilibrium partitioning of Fe between soluble and colloidal ligands is partially responsible for the distribution of Fe between soluble and colloidal size classes. However, a significant fraction of the colloidal Fe was inert to ligand exchange as soluble Fe concentrations were generally lower than values predicted by a simple equilibrium partitioning model.In surface waters, strong ligands with conditional stability constants of 10¹³ relative to total inorganic Fe appeared to dominate speciation in both the soluble and colloidal fractions. In deep waters these ligands were absent, and instead we found ligands with stability constants 12–15 fold smaller that were predominantly in the soluble pool. Nevertheless, significant levels of colloidal Fe were found in these samples, which we inferred must be inert to coordination exchange.