Large-Scale and Mesoscale Distribution of Plankton Biomass and Metabolic Activity in the Northeastern Central Atlantic

Plankton biomass and indices of metabolism and growth [electron transport system (ETS), glutamate dehydrogenase (GDH) and aspartate transcarbamylase (ATC) activities] were studied over a 2,800 km east-west section of the tropical North Atlantic Ocean (21°N) in <200, 200–500 and >;500 µm size classes. On the large-scale, zooplankton (>;200 µm) enzymatic activities increased westward in the study section, where large cyanobacteria chains (Trichodesmium spp.) were observed. Parallel to it, an increase in medium calanoids (1–2 mm length) was observed towards the western part of the transect, whereas small calanoids (<1 mm) were dominant throughout the boundary area of the subtropical gyre. Microplankton ETS and mesoplankton ETS and ATC activities seemed to match the wave length of low frequency waves. Our results suggest that such waves are related to the observed enhancement of metabolic activity of micro- and mesoplankton. The large-scale and mesoscale variability observed give evidence of the inadequacy of assuming a steady-state picture of the euphotic zone of tropical and subtropical waters.     

Induction of heat shock protein (hsp)60 in Isochrysis galbana exposed to sublethal preparations of dispersant and Prudhoe Bay crude oil

Adaptation to sublethal exposure to crude oil by phytoplankton is poorly understood. Use of chemical dispersants for oil spill remediation increases petroleum hydrocarbon concentrations in water, while exposing marine organisms to potentially toxic concentrations of dispersant. Heat shock proteins (hsps) have been found to serve as an adaptive and protective mechanism against environmental stresses. The objective of this project was to examine the induction of hsps in Isochrysis galbana, a golden-brown algae, following exposure to the water-accommodated fraction (WAF) of Prudhoe Bay crude oil (PBCO) and PBCO chemically dispersed with Corexit 9527® (dispersed oil: DO). Initial experiments using ³⁵S-labeled amino acids and 2-dimensional electrophoresis with subsequent western blotting identified and confirmed hsp60, a member of the chaperonin family of stress proteins, as being efficiently induced by heat shock in this species. One-dimensional SDS PAGE and western blotting, with hsp60 antibodies and chemiluminesence detection, were used to quantitate hsp60 following exposure to a range of environmental temperatures and concentrations of WAF and DO preparations. I. galbana cultured in 22 parts per thousand (‰) salinity showed a statistically significant increase (p<0.05) in hsp60 after exposure to 25, 30, and 35°C for 1 h compared to controls (20°C), while 34‰ cultures showed no significant increase in hsp60 with increasing temperature. Cultures (22 and 34‰) exposed to varying doses of WAF and DO exhibited statistically significant (p<0.05) increases in levels of hsp60 in all cases. A dose-related response was observed in all exposures (r²≥0.90) with the exception of 34‰ WAF. In independent exposures, a dose-related hsp60 response to naphthalene, a relatively abundant water-soluble aromatic hydrocarbon, was observed in both 22 and 34‰ cultures. Results of this study are consistent with previous studies in other species documenting increases in hsp60 levels with exposure to xenobiotics. Further studies are investigating the protective function of hsp60 against the toxic effects of exposure to WAF and DO preparations.     

Structure and Distribution of Autumn Zooplankton in the Southeastern Baltic Sea in 2015

Oceanology - Specific features of the structure and distribution of autumn zooplankton in the southeastern Baltic Sea (SEB) in October 2015 have been found taking into account the hydrological and...     

Analysis of EMD algorithm for identification and extraction of an acoustic signal in underwater channel against wind driven ambient noise

Sonar generated acoustic signals transmitted in underwater channel for distant communications are affected by numerous factors like ambient noise, making them nonlinear and non-stationary in nature. In recent years, the application of Empirical Mode Decomposition （EMD） technique to analyze nonlinear and non-stationary signals has gained much attention. It is an empirical approach to decompose a signal into a set of oscillatory modes known as intrinsic mode functions （IMFs）. In general, Hilbert transform is used in EMD for the identification of oscillatory signals. In this paper anew EMD algorithm is proposed using FFT to identify and extract the acoustic signals available in the underwater channel that are corrupted due to various ambient noises over a range of 100 Hz to 10 kHz in a shallow water region.Data for analysis are collected at a depth of 5 m and 10 m offshore Chennai at the Bay of Bengal. The algorithm is validated for different sets of known and unknown reference signals. It is observed that the proposed EMD algorithmidentifies and extracts the reference signals against various ambient noises. Significant SNR improvement is alsoachieved for underwater acoustic signals.     

Sub‐meter acoustic surveying

Abstract

During May 1985, a comprehensive GPS and acoustic navigation data set was collected off the Monterey, California coast. Three types of GPS units, a LORAN‐C, and a Miniranger operated concurrently with an OCEANO acoustic system to resolve state‐of‐the‐art accuracies for at‐sea geodetic positioning. This report details the acoustic system which displayed baseline errors of only ±0.25 m over distances to 2600 m. Unfiltered point‐to‐point acoustic navigation errors had a standard deviation of ± 1.25 m, which included ship motion errors in addition to surveying errors. Ninety percent of the stations had navigation standard deviations below ±0.75 m The experiment showed that sub‐meter acoustic surveying is the state‐of‐the‐art.     

Fishing rights and small communities: Alaska halibut IFQ transfer patterns

In the Alaska halibut individual fishing quota (IFQ) fishery, small remote fishing communities (SRFCs) have disproportionately lost fishing rights. Our analysis of quota market participation from 1995 to 1999 confirms that SRFC residents are more likely to sell than buy quota. Alaska Native heritage is another important predictor of quota market behavior. Residents of Alaska Native villages have an increased likelihood of selling quota. Loss of fisheries participation in small indigenous communities can be an unintended consequence of quota systems. Mitigation measures should take into account the social factors that can lead to such a redistribution of fishing rights in privatized access fisheries.     

Seasonality of particle-associated trace element fluxes in the deep northeast Atlantic Ocean

In the framework of the German contribution to the Joint Global Ocean Flux Study (JGOFS), deep-water fluxes of particle-associated trace elements were measured in the northeast Atlantic Ocean. The sinking particles were collected almost continuously from 1992 to 1996 at three time-series stations, L1 (33°N/22°W), L2 (47°N/20°W), and L3 (54°N/21°W), using sediment traps. The focus of the present study is the temporal variability of the particle-associated elemental fluxes of Al, Ca, Cd, Co, Cu, Fe, Mn, Ni, P, Pb, Ti, V, and Zn at a depth of 2000 m.A clear seasonality of the fluxes that persisted for several years was documented for the southernmost station (L1) at stable oligotrophic conditions in the area of the North Atlantic Subtropical Gyre East (NASTE). At L2 and L3, an episodic nature of the elemental fluxes was determined. Mesoscale eddies are known to frequently cause temporal and spatial variability in the flux of biogenic components in that area. These events modified the simple seasonal pattern controlled by the annual cycle at L2, in the North Atlantic Drift Region (NADR), and at L3, which was influenced by the Atlantic Arctic province (ARCT). All stations were characterized by an additional episodic lithogenic atmospheric supply reaching the deep sea.The integrated annual fluxes during the multi-year study revealed similar flux magnitudes for lithogenic elements (Al, Co, Fe, Ti, and V) at L2 and L3 and roughly twofold fluxes at L1. Biogenic elements (Cd, P, and Zn) showed the opposite trend, i.e., two to fourfold higher values at L2 and L3 than at L1. For Mn, Ni, and Cu, the spatial differences were smaller, perhaps because of the intermediate behavior, between lithogenic and biogenic, of these elements. Similarly, among the three study sites, there were no noticeable differences in the total annual flux of Pb.The respective lithogenic fractions of the deep-sea fluxes of Cd, Co, Cu, Mn, Ni, V, and Zn were subtracted based on the amount of Al, with the average composition of the continental crust as reference. This procedure allowed estimation of the labile trace element fraction (TE_exc) of the particles, i.e., TE taken up or scavenged during particle production and sedimentation. The ratios of TE_exc/P clearly demonstrated an enrichment of TE over labile P from biogenic surface material to the deep sea for Zn (factor 4–6), Mn (12–27), Ni (3–5), and Cu (9–25); an intermediate status for Co (0.5–2.2); and depletion for Cd vs. P (0.2–0.4). Surprisingly, the recycling behavior of excess Co was found to be similar to that of P. Hence, Co_exc behaved like a biogenic element; this is in contrast to total Co, which is dominated by the refractory lithogenic fraction.Moreover, it is argued that these excess elemental fluxes caused a loss of the dissolved elements in upper waters, since their transport reaches the deep-sea waters at 2000 m, a depth far below of deep-winter mixing and upwelling. The annual amount of excess TE exported from surface waters was estimated to be 1.3×10⁹ mol Zn y^?1, 4.4×10⁹ mol Mn y^?1, 4.9×10⁸ mol Ni y^?1, 2.2×10⁷ mol Cd y^?1, 7.4×10⁸ mol Cu y^?1, and 2.7×10⁷ mol Co y^?1 for the whole North Atlantic Ocean. Important primary sources that could replenish these losses are the aeolian and fluvial supply processes.     

Sediment bioavailable organic matter,deposition rates and mixing intensity in the Setúbal–Lisbon canyon and adjacent slope (Western Iberian Margin)

The role of the Setúbal–Lisbon canyon in accumulation and transport of labile organic matter from the coastal sea and ocean surface water towards the deep sea was assessed by investigating the distribution of organic matter of different quality in sedimentary aggregates and surface sediments of the canyon and adjacent slopes. Total hydrolysable amino acids (THAA) and organic carbon (Corg) were measured from aggregates, and contents of Corg, chlorophyll a (chl a), phaeopigments (phaeo), chloroplastic pigment equivalents (CPE) from sediments. As indices of organic matter (OM) quality THAA:Corg, degradation index (DI), chl a:phaeo, chl a:Corg and C:N ratio were determined. Sediment profiles of chl a and the isotope 210 of lead (²¹⁰Pb) were used as tracers in a transport model to estimate deposition rates and background levels of the tracers, and sediment mixing rates (Db). Whereas bulk Corg contents of canyon and slope sediments were practically similar at all depths, higher contents of THAA, chl a and CPE, as well as higher THAA:Corg, DI and chl a:Corg, in aggregates and sediments from the upper reaches of the canyon indicate that labile organic matter accumulates in the upper canyon. This is confirmed by higher chl a and ²¹⁰Pb deposition and Db calculated from the model. Hence, the Setúbal–Lisbon canyon, specially the upper region, acts as a natural trap of organic matter that is transported to the region via lateral transport and vertical settling from primary productivity. Organic matter might be further transported in downward canyon direction via rebound processes. The chl a and ²¹⁰Pb profiles reveal active sediment mixing by physical processes and/or animal reworking.     

Terminal velocities of pure and hydrate coated CO2 droplets and CH4 bubbles rising in a simulated oceanic environment

Understanding the upward motion of CO₂ droplets or CH₄ bubbles in oceanic waters is prerequisite to predict the vertical distribution of the two most important greenhouse gases in the water column after these have been released from the seabed. One of the key parameters governing the fate of droplets or bubbles dissolving into the surrounding seawater as they rise, is the terminal velocity, u_T. The latter is strongly influenced by the ability of both compounds to form skins of gas hydrate, if pressure and temperature satisfy thermodynamic framework conditions. Experimental efforts aiming to elucidate the rise properties of CO₂ droplets and CH₄ bubbles and specifically the influence of hydrate skins open the possibility to obtain a parameterization of u_T applicable to both hydrate-coated and pure fluid particles of CH₄ and CO₂. With the present study, we report on experimentally determined terminal velocities of single CH₄ bubbles released to pressurized and temperature-regulated seawater. Hydrate skins were identified by high bubble sphericities and changed motion characteristics. Based on these experiments as well as published data on the rise of hydrate-coated and pure liquid CO₂ droplets and physical principles previously successfully used for clean bubbles near atmospheric pressures, a new parameterization of u_T is proposed. Model predictions show a good agreement with the data base established from the laboratory-based measurements.