Age determination of Antarctic marine sediments

We present the first circum-East Antarctic chronology for the Holocene, based on 17 radiocarbon dates generated by the accelerator method. Marine sediments from around East Antarctica contain a consistent, high-resolution record of terrigenous (ice-proximal) and biogenic (open-marine) sedimentation during Holocene time. This record demonstrates that biogenic sedimentation beneath the open-marine environment on the continental shelf has been restricted to approximately the past 4 ka, whereas a period of terrigenous sedimentation related to grounding line advance of ice tongues and ice shelves took place between 7 and 4 ka. An earlier period of open-marine (biogenic sedimentation) conditions following the late Pleistocene glacial maximum is recognized from the Prydz Bay (Ocean Drilling Program) record between 10.7 and 7.3 ka. Clearly, the response of outlet systems along the periphery of the East Antarctic ice sheet during the mid-Holocene was expansion. This may have been a direct consequence of climate warming during an Antarctic 'Hypsithermal'. Temperature-accumulation relations for the Antarctic indicate that warming will cause a significant increase in accumulation rather than in ablation. Models that predict a positive mass balance (growth) of the Antarctic ice sheet under global warming are supported by the mid-Holocene data presented herein.

Marine ice-rafted debris records and age determinations along the northern Eurasian margin

Ice-rafted debris (IRD) (>2 mm), input in eight sediment cores along the Eurasian continental margin (Arctic Ocean), have been studied over the last two glacial/interglacial cycles. Together with the revised chronologies and new micropaleontological data of two cores from the northern Barents Sea (PS2138) and northeastern Kara Sea (PS2741) spanning Marine Isotope Stages (MIS) 6 to 1, the IRD data give new insights into the glacial history of northern Eurasian ice-sheets over the last 150 ka. The chronologies of the cores are based on stable isotope records, AMS 14C datings, paleomagnetic and biostratigraphic data. Extensive episodes of northern Barents Sea ice-sheet growth, probably to the shelf edge, occurred during the late Weichselian (MIS 2) and the Saalian (MIS 6). Major IRD discharge at the MIS 4/3-transition hints to another severe glaciation, probably onto the outer shelf, during MIS 4. IRD-based instabilities of the marine-based ice margin along the northern Barents Sea between MIS 4 and 2 are similar in timing with North Atlantic Heinrich events and Nordic Seas IRD events, suggesting similar atmospheric cooling over a broad region or linkage of ice-sheet fluctuations through small sea-level events. In the relatively low-precipitation areas of eastern Eurasia, IRD peak values during Termination II and MIS 4/3-transition suggest a Kara Sea ice-sheet advance onto the outer shelf, probably to the shelf edge, during glacial MIS 6 and 4. This suggests that during the initial cooling following the interglacials MIS 5, and possibly MIS 7, the combined effect of sustained inflow of Atlantic water into the Arctic Ocean and penetration of moisture-bearing cyclones into easterly direction supported major ice build-up during Saalian (MIS 6) and Mid-Weichselian (MIS 4) glaciation. IRD peak values in MIS 5 indicate at least two advances of the Severnaya Semlya ice-sheet to the coast line during the Early Weichselian. In contrast, a distinct Kara Sea ice advance during the Late Weichselian (MIS 2) is not documented by the IRD records along the northeastern Kara Sea margin.

Age determination of Holozene marine deposites from the western Mauritania (Table 1)

In an area regarded to be very favourable for the study of Holocene sea level changes one or several eustatic (?) oscillations of sea have been found using sedimentological and ecological methods. After a maximum of +3 m during the Nouakchottian stage (= Middle Flandrian or Late Atlantic) about 5500 YBP a drop of sea to -3.5 ± 0.5 m about 4100 YBP is testified by stromatolitic algae indicating the former sea level within the tidal zone with high accuracy. This evidence is supported by the observation of post-Nouakchottian regressive and transgressive geologic sequences, by buried beach deposits and flooded hardgrounds, post-Nouakchottian marine terraces of different height and age, the cutting off of one large and several small bays from the open sea etc. Possibly, one or two smaller oscillations followed between 4000 and 1500 years B. P. The radiocarbon age of the marine shells dated may be partly somewhat too old or too young.

Marine engineering & shipping age.

Title from caption.

An evaluation of home range models for marine fish tracking and fine scale habitat use and movement patterns of age 1 Greenland cod (Gadus macrocephalus ogac)

My thesis examines fine-scale habitat use and movement patterns of age 1 Greenland cod (Gadus macrocephalus ogac) tracked using acoustic telemetry. Recent advances in tracking technologies such as GPS and acoustic telemetry have led to increasingly large and detailed datasets that present new opportunities for researchers to address fine-scale ecological questions regarding animal movement and spatial distribution. There is a growing demand for home range models that will not only work with massive quantities of autocorrelated data, but that can also exploit the added detail inherent in these high-resolution datasets. Most published home range studies use radio-telemetry or satellite data from terrestrial mammals or avian species, and most studies that evaluate the relative performance of home range models use simulated data. In Chapter 2, I used actual field-collected data from age-1 Greenland cod tracked with acoustic telemetry to evaluate the accuracy and precision of six home range models: minimum convex polygons, kernel densities with plug-in bandwidth selection and the reference bandwidth, adaptive local convex hulls, Brownian bridges, and dynamic Brownian bridges. I then applied the most appropriate model to two years (2010-2012) of tracking data collected from 82 tagged Greenland cod tracked in Newman Sound, Newfoundland, Canada, to determine diel and seasonal differences in habitat use and movement patterns (Chapter 3). Little is known of juvenile cod ecology, so resolving these relationships will provide valuable insight into activity patterns, habitat use, and predator-prey dynamics, while filling a knowledge gap regarding the use of space by age 1 Greenland cod in a coastal nursery habitat. By doing so, my thesis demonstrates an appropriate technique for modelling the spatial use of fish from acoustic telemetry data that can be applied to high-resolution, high-frequency tracking datasets collected from mobile organisms in any environment.

Spatial behavior of two coral reef fishes within a Caribbean Marine Protected Area

A better understanding of the key ecological processes of marine organisms is fundamental to improving design and effective implementation of marine protected areas (MPAs) and marine biodiversity. The movement behavior of coral reef fish is a complex mechanism that is highly linked to species life-history traits, predation risk and food resources. We used passive acoustic telemetry to study monthly, daily and hourly movement patterns and space use in two species, Schoolmaster snapper (Lutjanus apodus) and Stoplight parrotfish (Sparisoma viride). We investigated the spatial overlap between the two species and compared intra-specific spatial overlap between day and night. Presence-absence models showed different diel presence and habitat use patterns between the two species. We constructed a spatial network of the movement patterns, which showed that for both species when fish were detected by the array of receivers most movements were made around the coral reef habitat while occasionally moving to silt habitats. Our results show that most individuals made predictable daily crepuscular migrations between different locations and habitat types, although individual behavioral changes were observed for some individuals across time. Our study also highlights the necessity to consider multiple species during MPA implementation and to take into account the specific biological and ecological traits of each species. The low number of fish detected within the receiver array, as well as the intraspecific variability observed in this study, highlight the need to compare results across species and individuals to be used for MPA management.

Chronostratigraphy and radiocarbon age inversion in the Holocene regressive barrier of Parana, southern Brazil

Twenty-two (14)C datings were performed at the central sector of the Parana coast to define Holocene regressive barrier evolution. The barrier Pleistocene substratum was ascribed an age between 40400 and 30000 yr BP, but it can also represent the penultimate sea level highstand during marine isotope stage 5e. The Holocene barrier samples provided ages between 8542-8279 and 2987-2751 cal yr BP, and showed at least six age inversions that were related to age differences between in situ or low-distance transported shells or trunk fragments, and high-distance transported vegetal debris, wood fragments and organic matter samples. The regressive Holocene barrier age was 4402-4135 cal yr BP near the base, and 2987-2751 cal yr BP near the top. Most of the vegetal remains were transported by ebb tidal currents from the estuaries to the inner shelf below wave base level during the mid-Holocene highstand; they were transported onshore by storm waves and littoral currents during the sea level lowering after the sea level maximum, and were deposited mainly as middle shoreface swaley cross-stratification facies. (C) 2008 Published by Elsevier B.V.

Cryptic vicariance in Gulf of California fishes parallels vicariant patterns found in Baja, California mammals and reptiles

Comparisons across multiple taxa can often clarify the histories of biogeographic regions. In particular, historic barriers to movement should affect multiple species and, thus, result in a pattern of concordant intraspecific genetic divisions among species. A striking example of such comparative phylogeography is the recent observation that populations of many small mammals and reptiles living on the Baja, California peninsula have a large genetic break between northern and southern peninsular populations. In the present study, I demonstrate that five species of near-shore fishes living on the Baja coastline of the Gulf of California share this genetic pattern. The simplest explanation for this concordant genetic division within both terrestrial and marine vertebrates is that the Baja peninsula was fragmented by a Plio-Pleistocene marine seaway and that this seaway posed a substantial barrier to movement for near-shore fishes. The genetic divisions within Gulf of California fishes also coincide with recognized biogeographic regions based on fish community composition and several environmental factors. It is likely that adaptation to regional environments and present-day oceanographic circulation limits gene exchange between biogeographic regions and helps maintain evidence of past vicariance.

Use of otoliths and eye lenses for measuring trace-metal incorporation in fishes: a biogeographic study

The otoliths and lenses of the temperate damselfish Parma microlepis (Gunther) (Pomacentridae) showed similar differences in trace-metal profile for selected locations along the coast of New South Wales, Australia. Otoliths and lenses displayed a differential ability to accumulate metals. Metal concentrations were ranked differently in the two structures (e.g. Sr > Ba > Pb > Rb > Hg in otoliths, and Hg > Sr similar or equal to Rb > Pb > Ba in lenses), and where similar metals were accumulated, they were accumulated at vastly different concentrations (e.g. Ba concentrations in otoliths are a thousand-fold greater than in lenses). Analyses of the otoliths and lenses of P. microlepis from locations close to Sydney and up to 100 kill from the city were able to distinguish amongst these locations with respect to a number of metals, namely Ba, Mn and Hg. Multivariate analyses of otolith and lens data gave similar results among locations (agreement was obtained for Ii out of 15 pair-wise comparisons), and differences were attributable to the differential ability of the two structures to accumulate metals such as Mn and Hg. Trace-metal differences between locations were found to coincide with the proximity of sewage (including industrial waste) and petroleum storage facilities to the different locations.