Intrusiones de la corriente de Kuroshio en el mar de China oriental

[EN]The Kuroshio is known to intrude onto the continental shelf in the southern East China Sea northeast of Taiwan. Two types of intrusions are observed: large and small, depending on how far the Kuroshio penetrates onto the ECS continental shelf, and on the location where it crosses the shelf break. This study demonstrates that cyclonic eddies from the western Pacific induce some of these large Kuroshio intrusions. The large intrusions are identified from more than 20 years of drifter tracks archived in the Global Drifter Program historical database and from weekly and biweekly drifter deployments carried out between April 2008 and September 2009 west of the Green Island (Taiwan). Kuroshio intrusions are observed in all seasons. Cyclonic mesoscale eddies, generated in the Subtropical Countercurrent and North Equatorial Current regions of the northwest Pacific Ocean, propagate westward into the Kuroshio and are well correlated with the observed intrusions. During the intrusions, the mean sea level anomaly computed from AVISO gridded maps shows a well defined cyclonic circulation southeast of the I-Lan ridge. The mean sea level anomaly also shows the meandering pattern of the Kuroshio when it intrudes onto the continental shelf of the southern East China Sea. The high correlation between the Kuroshio volume transport in the East Taiwan Channel (observed with moorings) and the satellite sea level anomaly permits us to use sea level anomaly as a proxy for the Kuroshio volume transport. When direct transport measurements are not available, this proxy is used to verify that intrusions due to the westward propagating eddies occur when the Kuroshio transport is low. An analytical reduced gravity model of an incident baroclinic current upon a step shelf is used to explain the difference between the large and small intrusions.

Decadal changes in the structure of Cymodocea nodosa seagrass meadows: natural vs. human influences

[EN] Seagrass meadows are deteriorating worldwide. However, numerous declines are still unreported, which avoid accurate evaluations of seagrass global trends. This is particularly relevant for the western African coast and nearby oceanic archipelagos in the eastern Atlantic. The seagrass Cymodocea nodosa is an ecological engineer on shallow soft bottoms of the Canary Islands. A comparative decadal study was conducted in 21 C. nodosa seagrass meadows at Gran Canaria Island to compare the structure (shoot density, leaf length and cover) between 2003 and 2012. Overall, 11 meadows exhibited a severe regression, while 10 remained relatively stable. During this period, natural influences (sea surface temperature, Chlorophyll-a concentration and PAR light, as well as the number of storm episodes detaching seagrasses) had a low predictive power on temporal patterns in seagrass structure. In contrast, proximity from a range of human-mediated influences (e.g. the number of outfalls and ports) seem to be related to the loss of seagrass; the rate of seagrass erosion between 2003 and 2012 was significantly predicted by the number of human-mediated impacts around each meadow. This result highlights promoting management actions to conserve meadows of C. nodosa at the study region through efficient management of local impacts