Seasonal succession and vertical distribution of phytoplankton in Lake Hayes and Lake Johnson,South Island,New Zealand

In two small monomictic lakes near Queenstown, South Island, New Zealand, algal associations characteristic of eutrophic waters were present throughout most of the period from December 1969 to February 1972.

In Lake Hayes, five of the six algal genera which were recorded in the plankton in 1948–50 were still present, but Anabaena appeared to have increased. Blooms of A. flos‐aquae which were not recorded 20 y ago (Jolly 1952) occurred in the lake in the three summers of this study and in winter of the second year. Melosira granulata dominated the plankton in winter; at other times of the year Closterium aciculare, Cyclotella kuetzingiana, and Staurastrum spp. were dominant.

In Lake Johnson the major algae differed from one year to another. Blooms of Anabaena flos‐aquae formed during the first two summers but were absent in the third, when Closterium aculum var. variabile was dominant. Peridinium cinctum was abundant throughout the first year, especially in December 1969 and October 1970, when concentrations of more than 1000 cells per ml occurred at the surface. During autumn and winter of the second year, Staurastrum bibrachiatum dominated the plankton.

In both lakes micro‐algae were abundant in late spring and early summer.

In winter when the lakes were isothermal, algae were distributed fairly uniformly with depth. During the period of thermal stratification, algae were mainly confined to the epilimnion. Although green algae and diatoms were usually dispersed fairly uniformly throughout this zone, Cryptomonas and Peridinium were often concentrated at a certain depth. In Lake Johnson in late summer 1971, a layer of purple photosynthetic bacteria, of which concentrations of 0.5–1.3 × 10° cells per ml were recorded, was present at a depth of 7–8 m.

Algae were more abundant in summer than in winter in both lakes. The mean standing crop of algae for the trophogenic zone of Lake Hayes was 6000 cells per ml, and a maximum crop of 65 000 cells per ml was recorded in December 1971 during an Anabaena bloom: the mean volume of phytoplankton was 1.93 mm³ per litre for the trophogenic zone with a maximum of 7.49 mm³per litre in January 1970 when Anabaena and Peridinium were abundant. In Lake Johnson the mean number of algae in the trophogenic zone was 11000 cells per ml and the mean volume of phytoplankton was 9.37 mm³ per litre: a maximum volume of 33.12mm³ per litre was recorded in October 1970 when Peridinium was abundant.     

Postulated responses of phytoplankton and bacteria to predicted increases of inorganic suspended sediments in oligotrophic lakes

We establish the relationships between concentrations of inorganic suspended sediments (ISS) on light, nutrients, phytoplankton, and bacteria in three oligotrophic lakes (four sites) and we use these relationships to predict the impacts of increasing concentrations of ISS on the biomass and productivity of phytoplankton and bacteria in the lakes. Increased concentrations of ISS contributed little available nutrient to the lakes. The relationships between ISS and underwater light attenuation differed among lakes because of variation in sediment size‐structure, and composition. Only at the site with the highest ISS concentrations and a relatively deep mixing depth, were phytoplankton apparently light‐limited and, thus, predicted to decline with increased ISS concentrations. In contrast to previously published studies, bacterial abundance and production were not highly correlated to suspended sediment concentrations in these lakes. However, bacterial biomass, productivity, and specific productivity were more strongly correlated to phytoplankton production. As a result of light limitation and stimulation of bacterial production, increases in ISS concentrations are not predicted to significantly shift the metabolic balance in the planktonic ecosystem of three of the sites towards greater heterotrophy. Where light limits phytoplankton production, increases in ISS are predicted to reduce the productivity of both phytoplankton and bacteria by direct inhibition of phytoplankton production, again without a large shift towards greater importance of the microbial loop. By reducing phytoplankton production and inhibiting larger cladoceran grazers, we predict that high concentrations of ISS will reduce available energy and its flow up the food chain.     

Conflicts at sea between artisanal and industrial fishers: Inter-sectoral interactions and dispute resolution in Senegal

Conflicts between artisanal and industrial fishermen—targeting increasingly scarce resources in Senegal—are posing a serious threat to human security and are only symbolically addressed by the country's fisheries governance regime. Severely outmatched in terms of political influence and size, artisanal fishermen are more vulnerable to the fallout of conflicts at sea. The loss of fishing materials threatens the livelihoods of fishermen and their families; collisions and violence between members of the two sectors often result in injury and death. This study examines at-sea interactions between Senegal's artisanal and industrial sectors and the formal and informal mechanisms in place for managing them. Conflictive interactions are found to co-exist alongside cooperative ones and both emerge in response to changes in marine resource abundance and management. Formal systems in place to mediate at-sea conflicts are ineffective and seldom used by artisanal fishermen, who either accept their losses, attempt to informally resolve conflicts with industrial actors or resort to violence.     

Exposure of spectrally distinct material by impact craters on Mercury: Implications for global stratigraphy

MESSENGER’s Mercury Dual Imaging System (MDIS) obtained multispectral images for more than 80% of the surface of Mercury during its first two flybys. Those images have confirmed that the surface of Mercury exhibits subtle color variations, some of which can be attributed to compositional differences. In many areas, impact craters are associated with material that is spectrally distinct from the surrounding surface. These deposits can be located on the crater floor, rim, wall, or central peak or in the ejecta deposit, and represent material that originally resided at depth and was subsequently excavated during the cratering process. The resulting craters make it possible to investigate the stratigraphy of Mercury’s upper crust. Studies of laboratory, terrestrial, and lunar craters provide a means to bound the depth of origin of spectrally distinct ejecta and central peak structures. Excavated red material (RM), with comparatively steep (red) spectral slope, and low-reflectance material (LRM) stand out prominently from the surrounding terrain in enhanced-color images because they are spectral end-members in Mercury’s compositional continuum. Newly imaged examples of RM were found to be spectrally similar to the relatively red, high-reflectance plains (HRP), suggesting that they may represent deposits of HRP-like material that were subsequently covered by a thin layer (∼1 km thick) of intermediate plains. In one area, craters with diameters ranging from 30 km to 130 km have excavated and incorporated RM into their rims, suggesting that the underlying RM layer may be several kilometers thick. LRM deposits are useful as stratigraphic markers, due to their unique spectral properties. Some RM and LRM were excavated by pre-Tolstojan basins, indicating a relatively old age (>4.0 Ga) for the original emplacement of these deposits. Detailed examination of several small areas on Mercury reveals the complex nature of the local stratigraphy, including the possible presence of buried volcanic plains, and supports sequential buildup of most of the upper ∼5 km of crust by volcanic flows with compositions spanning the range of material now visible on the surface, distributed heterogeneously across the planet. This emerging picture strongly suggests that the crust of Mercury is characterized by a much more substantial component of early volcanism than represented by the phase of mare emplacement on Earth’s Moon.     

Exchange dynamics of a shallow contaminated wetland

Flux pathways are investigated for a wetland system comprised of a river flowing through two shallow forebays and then entering the main basin of a lake. The hydrodynamic exchanges between these three components influence the fate and transport of heavy metals in the system. During non-storm summer flows the river plume, comprised of river water and entrained forebay water, was cooler than the lake surface water and so plunged as it entered the main basin and inserted near the seasonal thermocline. Because the river plume plunged, only a fraction of its metals flux was available to the epilimnion. A return flow into the forebay was always observed immediately above the river inflow, ensuring a predominantly two-layer exchange system. However during days of negative heat flux (surface heating), an additional exchange mechanism existed when the surface waters from the forebay formed a buoyant plume, flowing out into the main basin. This heated outflow produced a significant, but short-lived, arsenic flux from the forebay into the surface waters of the lake.     

Facies and allostratigraphy of high-latitude, glacially influenced marine strata of the Early Permian southern Sydney Basin, Australia

The Sydney Basin of New South Wales, Australia is a foreland basin containing a thick (up to 10 km) Permo-Triassic succession. The southern margin of the basin exposes strata deposited during Late Palaeozoic glaciation of south-eastern Gondwana. The Early Permian Wasp Head, Pebbley Beach, Snapper Point Formations and Wandrawandian Siltstone were deposited between 277 and 258 Ma on a polar, glacially influenced continental margin adjacent to ice sheets located over East Antarctica and eastern Australia. Sedimentary facies, together with related ichnofacies and fauna, can be grouped into six facies associations that record marine sub-environments ranging from high energy, storm-dominated inner shelf to turbidite-dominated upper slope settings. Cold marine conditions, with near-freezing bottom water temperatures, are recorded by glendonites. Ice-rafted debris, most likely deposited by icebergs, occurs in almost all facies associations. An allostratigraphic approach, emphasizing the recognition of bounding discontinuities (i.e. erosion surfaces and marine flooding surfaces), is used to subdivide the Early Permian stratigraphy into facies successions. Three types of succession can be identified and record changes in the relative influence of allocyclic controls such as basin tectonics, sediment supply and glacio-eustatic sea level variation. Together, sedimentological and allostratigraphic data allow reconstruction of the depositional history of the south-western margin of the Sydney Basin. Initial marine sedimentation, characterized by sediment gravity flows and storm-deposited sandstones of the lower Wasp Head Formation, occurred adjacent to a faulted basin margin. Overlying successions within the upper Wasp Head, Pebbley Beach and Snapper Point Formations, record aggradation in inner to outer shelf settings along a storm- and glacially influenced continental margin. Tectonic subsidence and basin flooding is recorded by deeper water turbidites of the Wandrawandian Siltstone.     

Recreating Ocean Space: Recreational Consumption and Representation of the Caribbean Marine Environment

This paper investigates the historical relationship between the development of marine-based tourism and representations of marine space. Over the past 100 years, the Caribbean Sea has been transformed from a transportation surface connecting exotic ports of call into a commodity itself. Imagined by early travelers as a two-dimensional space to be crossed, the Caribbean has became part of a new tropical marine aesthetic, a three-dimensional spectacle to be actively consumed and conserved. These changing representations of the marine environment as a space of consumption have been paralleled by changes in the relationships between marine and terrestrial political economies. As marine-based tourism has intensified, the balance of power among coastal resource users has shifted. The increasingly conflictive consequences of this shift are illustrated by the case of Soufrière in St. Lucia where new uses of marine space have re-configured social and economic relationships. Soufrière's coastal economy has been transformed and its marine space increasingly politicized as competing representations of the sea have been used to assert conflicting claims to resource access. This paper attempts to elucidate the power of these representations by investigating their historical relationship to the changing role of the Caribbean Sea in the international tourism industry.     

Geochemical controls on sediment reactivity and buffering processes in a heterogeneous aquifer

The injection and recovery of oxic water into deep anoxic aquifers may help to alleviate short- and long-term imbalance between freshwater supply and demand. The extent and structure of physical and geochemical heterogeneity of the aquifer will impact the water quality evolution during injection, storage and recovery. Water–sediment interactions within the most permeable parts of the aquifer, where the bulk of the injectant will penetrate, may dominate, however, water quality may also be impacted by interactions within the finer-grained, less permeable but potentially highly reactive media. In this study, the heterogeneity of the reductive capacity of an aquifer selected for water reuse projects was characterised, the amount, type and reactivity of the sedimentary reductants present determined, and the relationship between reductive capacity and sedimentary lithologies quantified. The average potential reductive capacities (PRC_TOT), based on total organic C and pyrite concentrations of the sediment, were quantified for sands (382 μmol O₂ g⁻¹), clays (1522 μmol O₂ g⁻¹), and silts (1957 μmol O₂ g⁻¹). Twenty-seven samples, spanning the three different lithologies, were then incubated for 50 days and the measured reductive capacities (MRC) determined for the sands (29.2 μmol O₂ g⁻¹), silts (136 μmol O₂ g⁻¹), and clays (143 μmol O₂ g⁻¹). On average, the MRC were 10% of the PRC_TOT. The main consumers of O₂ were pyrite (20–100%), sedimentary organic matter (SOM; 3–56%), siderite (3–28%) and Fe(II)-aluminosilicates (8–55%). The incubation data plus hydrogeochemical modelling, indicated that pH-buffering was controlled firstly by dissolution of trace level carbonates, followed by dissolution of feldspars. Zinc, Co, Ni, Cd and Pb were readily mobilized during incubation.     

Morphometric analysis of liver in rainbow trout: Quantitatively defining an organ of xenobiotic metabolism

The process of uptake, metabolism and eventual biliary excretion of xenobiotics by the teleost liver affords an opportunity for alteration within at least the following cells: sinusoidal endothelial, perisinoidal fat-storing (vitamin A-containing),¹ hepatocytes and biliary epithelial (of preductules, ductules and intrahepatic ducts). Our understanding of the existence and role(s) in physiologic and pathobiologic phenomena of non-hepatocytic populations of cells in teleost liver has been hampered by the use of immersion fixation procedures obviating resolution and analysis of sinusoidal lining cells and by the subjective nature of light and electron micrographs. The purpose of this study was to quantitatively define the rainbow trout (Salmo gairdneri, Richardson) liver. Computer-assisted morphometry² was conducted on livers of actively spawning 5 year old male and female trout (Wytheville strain).