Stable water isotopes of precipitation and firn cores from the northern Antarctic Peninsula region as a proxy for climate reconstruction

In order to investigate the climate variability in the northern Antarctic Peninsula region, this paper focuses on the relationship between stable isotope content of precipitation and firn, and main meteorological variables (air temperature, relative humidity, sea surface temperature, and sea ice extent). Between 2008 and 2010, we collected precipitation samples and retrieved firn cores from several key sites in this region. We conclude that the deuterium excess oscillation represents a robust indicator of the meteorological variability on a seasonal to sub-seasonal scale. Low absolute deuterium excess values and the synchronous variation of both deuterium excess and air temperature imply that the evaporation of moisture occurs in the adjacent Southern Ocean. The delta O-18-air temperature relationship is complicated and significant only at a (multi)seasonal scale. Backward trajectory calculations show that air-parcels arriving at the region during precipitation events predominantly originate at the South Pacific Ocean and Bellingshausen Sea. These investigations will be used as a calibration for ongoing and future research in the area, suggesting that appropriate locations for future ice core research are located above 600 m a.s.l. We selected the Plateau Laclavere, Antarctic Peninsula as the most promising site for a deeper drilling campaign.

Reproductive biology of the ghost shrimp Lepidophthalmus bocourti (A. Milne-Edwards, 1870) (Decapoda: Axiidea: Callianassidae): A tropical species with a seasonal reproduction

Based on the hypothesis that reproduction is a continuous process in tropical habitats, we analysed reproductive periodicity and egg production in the callianassid ghost shrimp Lepidophthalmus bocourti, one of the most common species in mangrove systems along the Pacific coast of Central America. During one year (May 2008 to April 2009), individuals of L. bocourti (N = 499) were collected nearshore Gulf of Nicoya, Pacific coast of Costa Rica. Observations were made on presence or absence of incubated embryos, and gonad activity of females was analysed as gonadosomatic index (GSI). Our results revealed that L. bocourti has a marked seasonal breeding period, which contradicts previous reports regarding coastal marine decapods from the tropics. Ovigerous females were found only from June to August, while high GSI values were obtained from March to July. The increase of GSI and appearance of ovigerous females were associated with a concomitant decrease of salinity, but not with temperature. We assume that reproduction of L. bocourti is adapted to local changes of environmental conditions, and that a decrease in salinity during rainy season may serve as a triggering factor for ovarian development. Compared to other ghost shrimps, L. bocourti produced on average more (2002 +/- 1365) and smaller (0.87 +/- 0.109 mm) eggs, which seems to suggest that this species does not have an abbreviated larval development as reported for other species of genus. The deviation from the generalization of constant reproduction in the tropics for shallow water marine invertebrates and its probable cause are adequately discussed.