Determining spatial changes in the diet of nearshore suspension-feeders along the South African coastline: Stable isotope and fatty acid signatures     

E. Louise Allan  Shan T. AmbroseNicole B. Richoux  P. William Froneman 《Estuarine, Coastal and Shelf Science》2010

Mesoscale oceanographic features, such as upwellings, are known to play an important role in regulating the structure and productivity of nearshore marine communities. Stable isotope (δ¹³C and δ¹⁵N) and fatty acid analyses were employed to assess the influence of an upwelling cell along the south-eastern coastline of southern Africa on the diet of the mussel, Perna perna. Eight sites were sampled: two upstream, three in the vicinity and three downstream of the upwelling cell. Stable isotope and fatty acid signatures indicated that the mussels consumed a diet of detritus derived mainly from macroalgae, diatoms and dinoflagellates. One-way ANOVA on the δ¹³C and δ¹⁵N signatures and the principal component analysis of the fatty acid profiles of the mussels identified distinct groups corresponding to the above mentioned regions. The proportion of diatom biomarkers in the fatty acid profiles decreased downstream of the upwelling region while the proportion of dinoflagellate biomarkers increased. Upwelling regions are typically associated with elevated levels of productivity; however, these systems usually become silicon depleted and result in the replacement of diatoms with dinoflagellates. The highest proportions of the dinoflagellate markers were recorded in the two furthest sites downstream of the upwelling cell. The spatial variation in the diet of the mussels, therefore, appears to reflect the presence of the upwelling cell in the nearshore biology of the region.  相似文献   

Local and regional constraints on relative sea-level changes in southern Isle of Skye,Scotland, since the Last Glacial Maximum     

Louise Best  Alexander R. Simms  Martin Brader  Jerry Lloyd  Juliet Sefton  Ian Shennan 《第四纪科学杂志》2022,37(1):59-70

New relative sea-level (RSL) data constrain the timing and magnitude of RSL changes in the southern Isle of Skye following the Last Glacial Maximum (LGM). We identify a marine limit at ~23 m OD, indicating RSL ~20 m above present c. 15.1 ka. Isolation basin data, supported by terrestrial and marine limiting dates, record an RSL fall to 11.59 m above present by c. 14.2 ka. This RSL fall occurs across the time of global Meltwater Pulse 1A, supporting recent research on the sources of ice melting. Our new data also help to resolve some of the chronological issues within the existing Isle of Skye RSL record and provide details of the sub-Arctic marine environment associated with the transition into Devensian Lateglacial climate at c. 14.5 k cal a bp , and the timing of changes in response to the Loch Lomond Stadial climate. Glacio-isostatic adjustment (GIA) model predictions of RSL deviate from the RSL constraints and reflect uncertainties in local and global ice models used within the GIA models. An empirical RSL curve provides a target for future research.  相似文献