Suffocation of pilchards (Sardinops sagax) by a green microalgal bloom in Wellington Harbour,New Zealand

A bloom of the green microalga Tetraselmis sp. in a small lagoon in Wellington Harbour, New Zealand, is considered to have caused a fish kill of pilchards (Sardinops sagax). The fish deaths are attributed to anoxia brought about by a combination of reduced dissolved oxygen levels and the microalgae sticking to and clogging the secondary gill lamellae of the fish.     

A new system for observing solar oscillations at the Mount Wilson Observatory

In this paper we describe a new observing system which is currently nearing completation at the Mount Wilson Observatory. This system has been designed to obtain daily measurements of solar photospheric and subphotospheric rotational velocities from the frequency splitting of non-radial solar p-mode oscillations of moderate to high degree (i.e. l > 150). The completed system will combine a 244 × 248 pixel CID camera with a high-speed floating point array processor, a 32-bit minicomputer, and a large-capacity disc storage system. We are integrating these components into the spectrograph of the 60-foot solar tower telescope at Mount Wilson in order to provide a facility which will be dedicated to the acquisition of oscillation data.     

Petrology of lavas from the Puu Oo eruption of Kilauea Volcano: III. The Kupaianaha episode (1986–1992)

 The Puu Oo eruption has been remarkable in the historical record of Kilauea Volcano for its duration (over 13 years), volume (>1 km³) and compositional variation (5.7–10 wt.% MgO). During the summer of 1986, the main vent for lava production moved 3 km down the east rift zone and the eruption style changed from episodic geyser-like fountaining at Puu Oo to virtually continuous, relatively quiescent effusion at the Kupaianaha vent. This paper examines this next chapter in the Puu Oo eruption, episodes 48 and 49, and presents new ICP-MS trace element and Pb-, Sr-, and Nd-isotope data for the entire eruption (1983–1994). Nearly aphyric to weakly olivine-phyric lavas were erupted during episodes 48 and 49. The variation in MgO content of Kupaianaha lavas erupted before 1990 correlates with changes in tilt at the summit of Kilauea, both of which probably were controlled by variations in Kilauea's magma supply rate. These lavas contain euhedral olivines which generally are in equilibrium with whole-rock compositions, although some of the more mafic lavas which erupted during 1990, a period of frequent pauses in the eruption, accumulated 2–4 vol.% olivine. The highest forsterite content of olivines (∼85%) in Kupaianaha lavas indicates that the parental magmas for these lavas had MgO contents of ∼10 wt.%, which equals the highest observed value for lavas during this eruption. The composition of the Puu Oo lavas has progressively changed during the eruption. Since early 1985 (episode 30), when mixing between an evolved rift zone magma and a more mafic summit reservoir-derived magma ended, the normalized (to 10 wt.% MgO) abundances of highly incompatible elements and CaO have systematically decreased with time, whereas ratios of these trace elements and Pb, Sr, and Nd isotopes, and the abundances of Y and Yb, have remained relatively unchanged. These results indicate that the Hawaiian plume source for Puu Oo magmas must be relatively homogeneous on a scale of 10–20 km³ (assuming 5–10% partial melting), and that localized melting within the plume has apparently progressively depleted its incompatible elements and clinopyroxene component as the eruption continued. The rate of variation of highly incompatible elements in Puu Oo lavas is much greater than that observed for Kilauea historical summit lavas (e.g., Ba/Y 0.09 a^–1 vs ∼0.03 a^–1). This rapid change indicates that Puu Oo magmas did not mix thoroughly with magma in the summit reservoir. Thus, except for variable amounts of olivine fractionation, the geochemical variation in these lavas is predominantly controlled by mantle processes. Received: 8 March 1996 / Accepted: 30 April 1996     

An annual survey ofHermesium adriaticum andEbria tripartita,two ebridian algae in the lower Chesapeake Bay

Two colorless flagellates,Hermesinum adriaticum andEbria tripartita, were found in the upper meter of water in Mobjack Bay and the York River.Hermesinum was abundant in the summer months when water temperatures were maximum for the area.Ebria was abundant at this and other times of the year. There was no correlation of temperature and abundance for the latter flagellate.     

Structural geometry of subvolcanic ring complexes as related to pre-Cenozoic motions of continental plates

Applications of plate tectonic concepts to problems of continental geology are hampered by the lack of direct evidence from the sea floor of pre-Cretaceous plate motions, since oceanic crust is continually destroyed by subduction in trenches. Studies on the structural geometry of Jurassic ring-dike provinces in Africa and North America, however, reveal patterns closely correlated with predicted plate motions. These ring complexes are commonly discordant to major crustal structures and show many features indicative of deep-seated origin. Ring-dike provinces probably form when continents drift over fixed plumes (hot-spots) in the asthenosphere and thereby provide unique tracks of pre-Cenozoic continental plate motions.     

Climatology of a glacial cycle

A “glacial cycle” is defined as a major global climatic oscillation of the order of 10⁵ yr, developed within an “ice age” sensu lato which may last 10⁶–10⁷ yr and which recurs at widely spaced intervals in geologic time (ca. 2 × 10⁸ yr). The ice age situation thus only persists during 5–10% of all geologic time and is preconditioned by geotectonics and not by extraterrestrial controls.     

Sedimentary architecture and genesis of Holocene shallow-water mud-mounds, northern Belize

Abstract Cangrejo and Bulkhead Shoals are areally extensive, Holocene biodetrital mud‐mounds in northern Belize. They encompass areas of 20 km² and 35 km² in distal and proximal positions, respectively, on a wide and shallow‐water, microtidal carbonate shelf where storms are the major process affecting sediment dynamics. Sediments at each mound are primarily biodetrital and comprise part of a eustatically forced, dominantly subtidal cycle with a recognizable deepening‐upward transgressive systems tract, condensed section and shallowing‐upward highstand systems tract. Antecedent topographic relief on Pleistocene limestone bedrock also provided marine accommodation space for deposition of sediments that are a maximum of 7·6 m thick at Cangrejo and 4·5 m thick at Bulkhead. Despite differences in energy levels and location, facies and internal sedimentological architectures of the mud‐mounds are similar. On top of Pleistocene limestone or buried soil developed on it are mangrove peat and overlying to laterally correlative shelly gravels. Deposition of these basal transgressive, premound facies tracked the rapid rate of sea‐level rise from about 6400–6500 years BP to 4500 years BP, and the thin basal sedimentation unit of the overlying mound‐core appears to be a condensed section. Following this, the thick and complex facies mosaic comprising mound‐cores represents highstand systems tract sediments deposited in the last ≈ 4500 years during slow and decelerating sea‐level rise. Within these sections, there is an early phase of progradationally offlapping catch‐up deposition and a later (and current) phase of aggradational keep‐up deposition. The mound‐cores comprise stacked storm‐deposited autogenic sedimentation units, the upper bounding surfaces of which are mostly eroded former sediment–water interfaces below which depositional textures have largely been overprinted by biogenic processes associated with Thalassia‐colonized surfaces. Vertical stacking of these units imparts a quasi‐cyclic architecture to the section that superficially mimics metre‐scale parasequences in ancient rocks. The locations of the mud‐mounds and the tidal channels transecting them have apparently been stable over the last 50 years. Characteristics that might distinguish these mud‐mounds and those mudbanks deposited in more restricted settings such as Florida Bay are their broad areal extent, high proportion of sand‐size sediment fractions and relatively abundant biotic particles derived from adjoining open shelf areas.     

Production patterns in Massachusetts Bay with outfall relocation

On September 6, 2000, the sewage outfall at the mouth of Boston Harbor was relocated 15 km offshore to alleviate pollution in Boston Harbor. The expected responses for nutrients and water column productivity parameters were for values to decrease at Boston Harbor, to increase at the outfall location, and to remain unchanged at the boundary of the near field region within 5 km of the outfall. Average values ofr water column measurements from 1992 to 2004 indicated these general responses with some exceptions. At the Harbor, nutrients decreased and chlorophyll increased but¹⁴C primary productivity remained statistically unchanged. At the new outfall location and at the boundary of the near field, nutrients increased and chlorophyll increased but primary productivity remained unchanged. Physical factors affecting primary production, such as pring water temperature, stratification, and wind, had more affects on productivity patters than nutrients from outfall relocation in the near field. A decrease in summer zooplankton after outfall relocation appeared to be due to a region-wide rather than outfall effluents.     

Lacustrine evidence for moisture changes in the Nebraska Sand Hills during Marine Isotope Stage 3

In the central Great Plains of North America, loess stratigraphy suggests that climate during the late Pleistocene was cold and dry. However, this record is discontinuous, and there are few other records of late-Pleistocene conditions. Cobb Basin, located on the northern edge of the Nebraska Sand Hills, contains lacustrine sediments deposited during Marine Isotope Stage 3, beginning approximately 45,000 cal yr BP and continuing for at least 10,000 yr. The lake was formed by a dune dam blockage on the ancient Niobrara River, and its deposits contain a diatom record that indicates changes through time in lake depth driven by changes in effective moisture. During the earliest stages of lake formation, the climate was arid enough to mobilize dunes and emplace dune sand into a blocking position within the Niobrara streambed. Diatom assemblages suggest that lake-level was shallow at formation, increased substantially during a wet interval, and then became shallow again, as arid conditions resumed. By about 27,000 cal yr BP the lake was filled, and a shallow ephemeral river occupied the basin.