De lederschildpad: spectaculaire nieuwe waarnemingen in Nederland en een statusoverzicht

De lederschildpad is een zeeschildpad die in alle wereldzeeën thuis is en de soort is een frequente bezoeker van Noordwest-Europa. Een enkele keer wordt de soort in Nederlandse wateren waargenomen en in 2009 zijn er in drie weken tijd drie meldingen binnen gekomen. Dit artikel gaat over de Nederlandse vondsten, ingeleid door een algemeen deel over de soort dat is toegespitst op de situatie in de Atlantische Oceaan. Ook wordt het verschil tussen de populatiestatus in de Atlantische Oceaan, waar de soort stabiel voorkomt en de Grote Oceaan, waar de soort binnen twee decennia met 90% is afgenomen, verklaard

Gas and gas hydrate distribution around seafloor seeps in Mississippi Canyon, Northern Gulf of Mexico, using multi-resolution seismic imagery

This paper is not subject to U.S. copyright. The definitive version was published in Marine and Petroleum Geology 25 (2008): 952-959, doi:10.1016/j.marpetgeo.2008.01.015.To determine the impact of seeps and focused flow on the occurrence of shallow gas hydrates, several seafloor mounds in the Atwater Valley lease area of the Gulf of Mexico were surveyed with a wide range of seismic frequencies. Seismic data were acquired with a deep-towed, Helmholz resonator source (220–820 Hz); a high-resolution, Generator-Injector air-gun (30–300 Hz); and an industrial air-gun array (10–130 Hz). Each showed a significantly different response in this weakly reflective, highly faulted area. Seismic modeling and observations of reversed-polarity reflections and small scale diffractions are consistent with a model of methane transport dominated regionally by diffusion but punctuated by intense upward advection responsible for the bathymetric mounds, as well as likely advection along pervasive filamentous fractures away from the mounds.This work was funded through ONR program element 61153N, and U.S. Department of Energy Grant DE-A126-97FT3423

Embryonic Death Is Linked to Maternal Identity in the Leatherback Turtle (Dermochelys coriacea)

Leatherback turtles have an average global hatching success rate of ∼50%, lower than other marine turtle species. Embryonic death has been linked to environmental factors such as precipitation and temperature, although, there is still a lot of variability that remains to be explained. We examined how nesting season, the time of nesting each season, the relative position of each clutch laid by each female each season, maternal identity and associated factors such as reproductive experience of the female (new nester versus remigrant) and period of egg retention between clutches (interclutch interval) affected hatching success and stage of embryonic death in failed eggs of leatherback turtles nesting at Playa Grande, Costa Rica. Data were collected during five nesting seasons from 2004/05 to 2008/09. Mean hatching success was 50.4%. Nesting season significantly influenced hatching success in addition to early and late stage embryonic death. Neither clutch position nor nesting time during the season had a significant affect on hatching success or the stage of embryonic death. Some leatherback females consistently produced nests with higher hatching success rates than others. Remigrant females arrived earlier to nest, produced more clutches and had higher rates of hatching success than new nesters. Reproductive experience did not affect stage of death or the duration of the interclutch interval. The length of interclutch interval had a significant affect on the proportion of eggs that failed in each clutch and the developmental stage they died at. Intrinsic factors such as maternal identity are playing a role in affecting embryonic death in the leatherback turtle