Carbonate content and d13C record of a Jordan Cretaceous outcrop (Section GM3 (Ghawr Al Mazar (Ghor al Mazrar))

An evaluation of the global synchronicity and duration of "3rd-order" sea-level fluctuations during the Cretaceous greenhouse has been hampered by poor constraints on potential climatic and tectonic drivers, and limitations of geochronology and chronostratigraphic correlation. To provide insight into the nature of such sea-level fluctuations, here we present a new Late Cretaceous record from the Jordanian Levant Platform, comprising a detailed physical-, bio-, chemo- and sequence stratigraphy. Carbonate content of these strata reflects overall sequence stratigraphic development, and demonstrates a dramatic 3rd-order-scale cycle that is also apparent in the d°C record. Updated radioisotopic constraints and astrochronologic testing provide support for the inference of an ~1 million year long sea-level oscillation associated with this 3rd-order cycle, which likely reflects a long-period obliquity (1.2 Myr) control on eustasy and stratigraphic sequence development, linked to the global carbon cycle. The observation of cyclic sea-level fluctuations on this time scale suggests sustained global modulation of continental fresh-water-storage. The hypothesized link between astronomical forcing and sea-level forms a baseline approach in the global correlation of sequence boundaries.

(Table 1) Chlorophyll a content and microalgae abundance and biovolume in pack ice in the Bellingshausen Sea

Pack ice in the Bellingshausen Sea contained moderate to high stocks of microalgal biomass (3-10 mg Chl a/m**2) spanning the range of general sea-ice microalgal microhabitats (e.g., bottom, interior and surface) during the International Polar Year (IPY) Sea Ice Mass Balance in the Antarctic (SIMBA) studies. Measurements of irradiance above and beneath the ice as well as optical properties of the microalgae therein demonstrated that absorption of photosynthetically active radiation (PAR) by particulates (microalgae and detritus) had a substantial influence on attenuation of PAR and irradiance transmission in areas with moderate snow covers (0.2-0.3 m) and more moderate effects in areas with low snow cover. Particulates contributed an estimated 25 to 90% of the attenuation coefficients for the first-year sea ice at wavelengths less than 500 nm. Strong ultraviolet radiation (UVR) absorption by particulates was prevalent in the ice habitats where solar radiation was highest - with absorption coefficients by ice algae often being as large as that of the sea ice. Strong UVR-absorption features were associated with an abundance of dinoflagellates and a general lack of diatoms - perhaps suggesting UVR may be influencing the structure of some parts of the sea-ice microbial communities in the pack ice during spring. We also evaluated the time-varying changes in the spectra of under-ice irradiances in the austral spring and showed dynamics associated with changes that could be attributed to coupled changes in the ice thickness (mass balance) and microalgal biomass. All results are indicative of radiation-induced changes in the absorption properties of the pack ice and highlight the non-linear, time-varying, biophysical interactions operating within the Antarctic pack ice ecosystem.

Stomach content and parasite characteristics of M. scorpius from Frobisher Bay, Baffin Island

Shorthorn sculpin (Myoxocephalus scorpius) from Frobisher Bay, Baffin Island, is a slow growing long-lived species. A wide range of diet items were present in the stomachs of the shorthorn sculpins sampled but 2-3 diet items (amphipod species) comprised 99.5 % of total food consumed. These amphipods were present in the stomachs in similar proportions among all age classes of shorthorn sculpin. Several new host records for parasites were reported and mean numbers of parasite species increased with shorthorn sculpin age. The increased diversity of parasite species and higher d15N values in older/larger individuals suggest that their diets were more diverse and the prey items consumed had higher d15N values. By contrast, the value of d13C in dominant diet items masked the d13C values of minor diet items. We conclude that parasites and stable isotope values provide complementary data on feeding patterns of the shorthorn sculpin. The ubiquitous marine acanthocephalan, Echinorhynchus gadi, was found at high prevalences (87-100 %) and mean intensities (28-35), and were localized in the midgut. In contrast to other studies on acanthocephalans, E. gadi did not influence fish condition as measured by condition factor, liver somatic and gonado-somatic indices.