Abundance, Biomass, Production and Trophic Roles of Micro- and Net-Zooplankton in Ise Bay, Central Japan, in Winter

We investigated the geographical variations in abundance and biomass of the major taxonomic groups of micro- and net-zooplankton along a transect through Ise Bay, central Japan, and neighboring Pacific Ocean in February 1995. The results were used to estimate their secondary and tertiary production rates and assess their trophic roles in this eutrophic embayment in winter. Ise Bay nourished a much higher biomass of both micro- and net-zooplankton (mean: 3.79 and 13.9 mg C m^–3, respectively) than the offshore area (mean: 0.76 and 4.47 mg C m^–3, respectively). In the bay, tintinnid ciliates, naked ciliates and copepod nauplii accounted for, on average, 69, 18 and 13% of the microzooplankton biomass, respectively. Of net-zooplankton biomass, copepods (i.e. Acartia, Calanus, Centropages, Microsetella and Paracalanus) formed the majority (mean: 63%). Average secondary production rates of micro- and net-zooplankton in the bay were 1.19 and 1.87 mg C m^–3d^–1 (or 23.1 and 36.4 mg C m^–2d^–1), respectively, and average tertiary production rate of net-zooplankton was 0.75 mg C m^–3d^–1 (or 14.6 mg C m^–2d^–1). Available data approximated average phytoplankton primary production rate as 1000 mg C m^–2d^–1 during our study period. The transfer efficiency from primary production to zooplankton secondary production was 6.0%, and the efficiency from secondary production to tertiary production was 25%. The amount of food required to support the zooplankton secondary production corresponded to 18% of the phytoplankton primary production or only 1.7% of the phytoplankton biomass, demonstrating that the grazing impact of herbivorous zooplankton was minor in Ise Bay in winter.     

Distribution, abundance, and growth of larval tautog, Tautoga onitis, in Buzzards Bay, Massachusetts, USA

Tautog, Tautoga onitis, is an abundant species of fish in estuaries of the northeastern United States. Planktonic tautog larvae are abundant in summer in these estuaries, but there is little information on rates of growth of tautog larvae feeding on natural assemblages of food in the plankton. We examined abundance and growth of larval tautog and environmental factors during weekly sampling at three sites along a nearshore‐to‐offshore transect in Buzzards Bay, Massachusetts, USA during summer 1994. This is the first study of a robust sample size (336 larvae) to estimate growth rates of field‐caught planktonic tautog larvae feeding on natural diets, using the otolith daily‐growth‐increment method. The study was over the entire summer period when tautog larvae were in the plankton. The sampling sites contrasted in several environmental variables including temperature, dissolved oxygen (DO), and chlorophyll a concentration. There was a temporal progression in the abundance of tautog larvae over the summer, in relation to location and temperature. Tautog larvae were first present nearshore, with a pronounced peak in abundance occurring at the nearshore sites during the last 2 weeks in June. Larvae were absent at this time further offshore. From late June through August, larval abundance progressively decreased nearshore, but increased offshore although never approaching the abundance levels observed at the nearshore sites. The distribution and abundance of tautog larvae appeared to be related to a nearshore‐to‐offshore seasonal warming trend and a nearshore decrease in DO. Otoliths from 336 larvae ranging from 2.3 to 7.7 mm standard length had otolith increment counts ranging from 0 to 19 increments. Growth of larval tautog was estimated at 0.23 mm·day^?1, and length of larvae prior to first increment formation was estimated at 2.8 mm indicating that first increment formation occurs 3–4 days after hatching at 2.2 mm. Despite spatial and temporal differences in environmental factors, there were no significant differences in growth rates at any of three given sites over time, or between sites. Because larval presence only occurred at a narrow range of temperature (17–23.5 °C) and DO (6.5–9.3 mg·l^?1), in situ differences in growth did not appear to be because of differences in larval distribution and abundance patterns relative to these parameters.     

Land use,associated eel production,and abundance of fish and crayfish in streams in Waikato,New Zealand

Abstract

The density and biomass of fish and crayfish, and the production of eels, was compared among streams in native forest, exotic forest, and pasture. Populations were estimated by multiple‐pass electroshocking at 11 sites in hill‐country streams in the Waikato region, North Island. Three sites were in native forest, four in exotic forest, and four in pasture. Length of stream sampled at each site was 46–94 m (41–246 m² in area), and catchment areas up stream of the sites ranged from 0.44 to 2.01 km².

A total of 487 fish were caught. The species were longfinned and shortfinned eels, banded kokopu, Cran's and redfinned bullies, and common smelt. Eels were the most abundant fish in all three land‐use types, and shortfinned eels were more abundant at pastoral sites (mean density 1.11 fish m^?2) than longfinned eels (mean density 0.129 fish m^?2). Banded kokopu were present only at forested sites. Mean fish densities were greater at pastoral sites (1.55 fish m^?2) than under either native forest (0.130 fish m^?2) or exotic forest (0.229 fish m^?2). Mean fish biomass was also greater at pastoral sites (89.7 g m^?2) than under native forest (12.8 g m^?2) or exotic forest (19.3 g m^?2). Longfinned eels made a greater contribution to the fish biomass at all sites than did shortfinned eels. Densities of crayfish were high (0.46–5.40 crayfish m^?2), but were not significantly different between land‐use types. Crayfish biomass ranged from 1.79 to 11.2 g m^?2. Total eel production was greater at pastoral sites (mean 17.9 g m^?2 year¹) than at forest sites (mean 2.39 gm^?2 year^?1).     

Enrichments in Hg,Cd, As,and Sb in recent sediments of Azores-Iceland Ridge

Mercury, cadmium, arsenic, and antimony were analyzed in cores sampled on the Azores-Iceland Ridge. High values of 780 g · kg^–1 for Hg, 1.7 g · g^–1 for Cd, 87 g · g^–1 for As, and 8.1 g · g^–1 for Sb occur in the rift valley and transform faults. These enrichments, strictly linked to the ridge, could not have an allochtonous origin. A local hydrogenous flux may explain this phenomenon. These metallic enrichments may be connected to a hydrothermal activity extended between 43° N and 47° N.     

The distributions of, and relationship between, He and nitrate in eddies

We present and discuss the distribution of ³He and its relationship to nutrients in two eddies (cyclone C1 and anticyclone A4) with a view towards examining eddy-related mechanisms whereby nutrients are transported from the upper 200–300 m into the euphotic zone of the Sargasso Sea. The different behavior of these tracers in the euphotic zone results in changes in their distributions and relationships that may provide important clues as to the nature of physical and biological processes involved.The cyclonic eddy (C1) is characterized by substantial ³He excesses within the euphotic zone. The distribution of this excess ³He is strongly suggestive of both past and recent ongoing deep-water injection into the euphotic zone. Crude mass balance calculations suggest that an average of approximately 1.4±0.7 mol m⁻² of nitrate has been introduced into the euphotic zone of eddy C1, consistent with the integrated apparent oxygen utilization anomaly in the aphotic zone below. The ³He–NO₃ relationship within the eddy deviates substantially from the linear thermocline trend, suggestive of incomplete drawdown of nutrients and/or substantial mixing between euphotic and aphotic zone waters.Anticyclone (A4) displays a simpler ³He–NO₃ relationship, but is relatively impoverished in euphotic zone excess ³He. We suggest that because of the relatively strong upwelling and lateral divergence of water the residence time of upwelled ³He is relatively short within the euphotic zone of this eddy. An estimate of the recently upwelled nutrient inventory, based on the excess ³He observed in A4's lower euphotic zone, is stoichiometrically consistent with the oxygen maximum observed in the euphotic zone.     

Submerged vegetation of Lakes Sumner,Marion, Katrine,Taylor, and Sheppard in Canterbury,New Zealand

The submerged vegetation of Lakes Sumner, Marion, Katrine, Taylor, and Sheppard was surveyed in May 1987. These high‐altitude lakes lie at c. 600 m a.s.l., within the largely unmodified upper Hurunui catchment. Submerged vegetation was diverse and included numerous short shallow‐water species, dense swards of Isoetes alpinus, low covers of taller native vascular plants, and charophyte meadows beyond the depth limit of vascular plants to a maximum of 15 m. A sparse deepwater bryophyte community was observed from 11 to 32 m depth in Lake Sumner. Displacement of native vegetation by dense growths of the adventive oxygen weed Elodea canadensis over mid‐depths of 3–6 m was noted in all lakes, except Lake Marion.     

Natural and anthropogenic sources of Hg,Cd, Pb,Cu and Zn in seawater and sediment of Mljet National Park,Croatia

Distributions of Hg, Cd, Pb, Cu and Zn in seawater and sediment from Mljet National Park, Adriatic Sea are presented for the first time. Natural and anthropogenic factors play an important role in determining resultant trace metals' concentrations in the region. We place particular emphasis on the saline “lakes” of Malo Jezero and Veliko Jezero, which have restricted flows of seawater. In Malo Jezero lake, fresh karstic spring water generated by flooding, and weathering of dolomites are the main sources of naturally elevated Cd, Pb and Zn concentrations (20.7 ± 1.6, 289 ± 19, 1260 ± 0.08 ng L^?1, respectively); anthropogenic input is negligible. In Veliko Jezero lake enhanced Cu and Zn contents originate from anthropogenic input (tourism and agriculture). Distributions of the Pb and Zn in the water columns of both lakes are influenced by natural aragonite precipitation and sedimentation. Exceptionally high total Hg concentrations of 24.2 and 33.7 ng L^?1 in the water column of Malo Jezero, sampled during periods of high rainfall associated with strong eastern winds, suggest an airborne input. Total Hg concentrations in waters of both lakes are elevated because of inefficient mixing. Two different metal distribution patterns exist in the sediment columns. First, Hg, Pb, Cu and Zn show elevated concentrations in recent sediments due to anthropogenic input. Second, Cd content increases with depth due to reprecipitation via a downward redox boundary shift.Described natural processes, as well as anthropogenic influence, enhance levels of trace metals. Careful study followed by suitable interpretation based on geochemical data were necessary to distinguish natural from anthropogenic sources.     

Determination of Na,K, Mg,Ca, Fe,and Mn in organic particulate matter in seawater by atomic absorption

A method for the determination by atomic absorption spectrophotometry of six major inorganic components of the organic particulate matter in seawater is described. Particles were formed by shaking aliquots of filtered seawater. The yield of aggregates varied greatly in replicate samples. The major factors in the variability of the analyses are the high and variable filter blank values for the elements of interest.     

Lead, cadmium, copper, nickel and iron in limpets, mussels and snails from the coast of ras Beirut, Lebanon

Samples of Patella coerulea (Linnaeus), Brachydontes variabilis (Krauss), Monodonta turbinata (Born) and surface seawater were collected at eight locations along the coast of Ras Beirut, Lebanon, and analysed for lead, cadmium, copper, nickel and iron. With the exception of cadmium, the metal levels found in the three molluscs appear to be high in relation to levels reported by investigators from other coastal areas. The average values for lead, cadmium and nickel within these animals were quite similar. Concentrations of copper in P. coerulea were lower, but concentrations of iron were much higher than those found in both B. variabilis and M. turbinata. Further studies of metal levels in various other intertidal organisms from Ras Beirut, together with investigations into the possible effects of seasonal changes on metal concentration and distribution, are currently under way.     

Concentrations of zinc,manganese, copper,cadmium, magnesium and iron in ten species of algae and sea water from Aqaba,Jordan

Concentrations of zinc, manganese, copper, cadmium, magnesium and iron in three species of red, four species of brown and three species of green macroalgae, and also in sea water have been determined at two localities along the coast of Aqaba. Significant differences in metal concentrations were found between the various species (P<0·01). Similar significant differences were found with regard to different metals (P<0·001). Concentration factors ranged between 10² for Cd and 9·2 × 10⁴ for Fe. The difference in levels of metals between the two localities, however, was not significant (P > 0·05). Of the three groups of algae examined, rhodopytes exhibited the highest concentration power of metals.     

The behavior of Zn,Cd, Cu,Ni, Co,Fe, and Mn in anoxic baltic waters

In June 1981, dissolved Zn, Cd, Cu, Ni, Co, Fe, and Mn were determined from two detailed profiles in anoxic Baltic waters (with extra data for Fe and Mn from August 1979). Dramatic changes across the O₂H₂S interface occur in the abundances of Cu, Co, Fe, and Mn (by factors of ?100). The concentrations of Zn, Cd, and Ni at the redox front decrease by factors between 3 to 5.Equilibrium calculations are presented for varying concentrations of hydrogen sulfide and compared with the field data. The study strongly supports the assumption that the solubility of Zn, Cd, Cu, and Ni is greatly enhanced and controlled by the formation of bisulfide and(or) polysulfide complexes. Differences between predicted and measured concentrations of these elements are mainly evident at lower ΣH₂S concentrations.Cobalt proved to be very mobile in anoxic regions, and the results indicate that the concentrations are limited by CoS precipitation. The iron (Fe²⁺) and manganese (Mn²⁺) distribution in sulfide-containing waters is controlled by total flux from sediment-water interfaces rather than by equilibrium concentrations of their solid phases (FeS and MnCO₃). The concentrations of these metals are therefore expected to increase with prolonged stagnation periods in the basin.     

Seasonal and spatial variation in species diversity, abundance, and element accumulation capacities of macroalgae in mangrove forests of Zhanjiang, China

The objective of this study was to investigate whether there was distinctive seasonal and zonal variation in the species diversity, biomass, and element accumulation capacities of macroalgae in two major intertidal mangrove stand types （Avicennia marina assemblage andSonneratia apetala assemblage） in the Zhanjiang region of southern China. Over a year, 31 species in 15 genera were identified in both mangrove assem-blages, of which the dominant species wereCladophoropsis zollingeriand Enteromorpha clathrat.Macroal-gal species were significantly most abundant in spring （p〈0.05）, followed by summer, winter, and autumn. Variation in the zonal distribution of macroalgal species was conspicuous in both intertidal mangrove as-semblages, with the greatest abundance in the middle zone, and the least in the front zone. Patterns in the seasonal and zonal variation in macroalgal biomass in theS. apetalaassemblage were similar to those of macroalgal species diversity in both mangrove assemblages. The seasonal patterns in tissue concentrations of 15 analyzed elements were not uniform among the macroalgaeC. zollingeri,E. clathrata, andGracilaria salicornia in theA. marina assemblage. All three species exhibited variation in their responses to ambient concentrations of different elements, implying their differential ability to absorb and selectively accumulate certain elements.     

Destruction of Atmospheric Ozone in Ox,HOx, NOx,ClOx, BrOx,and IOx Catalytic Cycles

Izvestiya, Atmospheric and Oceanic Physics - Data on the relative contribution of the Ox, HOx, NOx, ClOx, BrOx, and IOx catalytic cycles to atmospheric ozone destruction are given for June and...     

Distribution and stoichiometry of Al,Mn, Fe,Co, Ni,Cu, Zn,Cd, and Pb in seawater around the Juan de Fuca Ridge

A central theme of the ongoing GEOTRACES program is to improve the understanding of processes occurring at ocean interfaces with continents, sediments, and ocean crust. In this context, we studied the distributions of Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb around the Juan de Fuca Ridge (JdFR) in total dissolvable (td), dissolved (d), and labile particulate (lp) fractions, which represent a fraction in unfiltered samples, filtered samples through an AcroPak capsule filter, and the difference between td and d, respectively. Al and Fe were dominated by lp-species, while Ni, Zn, and Cd were dominated by d-species with undetectable amounts of lp-species. Major findings in this study are as follows: (1) The continental margin (CM) provided large sources of Al, Mn, Fe, and Co from the surface to ~2000 m in depth. The supply from CM caused high surface concentrations of dMn and dCo, a subsurface (100–300 m depth) maximum of dCo, and intermediate (500–2000 m depth) maxima of lpAl and lpFe. The supply of dFe from CM was ~10 times that from the high-temperature hydrothermal activity at station BD21, which is located at ~3 km from the Middle Valley venting site and ~ 200 km from Vancouver Island. (2) DPb was maximum at the top layer of North Pacific Intermediate Water, probably owing to isopycnal transport of anthropogenic Pb via advection of subducted surface waters. Although dCo and dPb had different sources in the upper water, they showed a strong linearity below 300 m (r ² = 0.95, n = 38), indicating concurrent scavenging. (3) A high-temperature hydrothermal plume occurred at a depth of 2300 m at BD21, accounting for maxima of dAl, dMn, dFe, lpCu, and lpPb and a minimum of dCu. (4) Strong bottom maxima of lpAl, lpMn, lpFe, lpCo, and lpPb occurred above the abyssal plain at the western foot of the JdFR, indicating resuspension of sediments. However, bottom maxima of d-species were apparent only for dAl and dCu.     

Fisheries privatization,social transitions,and well-being in Kodiak,Alaska

Scholars and fishermen alike view the privatization of fishing rights as a fundamental driver of social change in fishing communities. This article presents the results of a mixed-methods ethnographic study in Kodiak, Alaska, exploring how fisheries privatization processes remake fishery systems. Findings from this study suggest that a diverse range of fishery participants share core values about the social dimensions of fishery systems. Support or opposition to past privatization processes tended to be articulated in reference to how these core values (e.g., hard work, opportunity, and fairness) were perceived to have been strengthened or eroded by such processes. Data from this study suggest that while still widespread in the Kodiak fishing community, core social values in fishing may be changing as a result of privatization processes. Although ethnographic and survey data showed a range of perspectives on the effects of privatization on fishing and the Kodiak community, study participants tended to talk about privatization as a significant change that had divisive, negative impacts in the community. Crew members and the next generation of fishermen were identified as disproportionately affected by privatization processes. Ethnographic data detail important shifts in the power, status, and livelihoods of crew members. Nearly all Kodiak fishery participants interviewed expressed concern about the future of fisheries access in the community for the next generation, in large part because of the substantial financial barriers to entry generated by privatization of fisheries access. Many discussed the need for more entry-level opportunities necessary for access in all fisheries.     

Category, narrative, and value in the governance of small-scale fisheries

Since the 1970s, small-scale fisheries have had an important place in fisheries social science and in fisheries management. While there has been substantial discussion of what constitutes the category of small-scale fisheries, its considerable ambiguity is nevertheless often passed over. This paper argues that while the category of scale fisheries can be best understood in terms of scale, the underlying reason for the power of the category lies in the values of social justice and ecological sustainability that it has come to represent in response to dominant high modern narratives of change. Fisheries governance may better be served by prioritising these values rather than by making a fetish out of small-scale fisheries.