Spatial demography of Calanus finmarchicus in the Irminger Sea

Continuous Plankton Recorder data suggest that the Irminger Sea supports a major proportion of the surface-living population of the copepod Calanus finmarchicus in the northern North Atlantic, but there have been few studies of its population dynamics in the region. In this paper, we document the seasonal changes in the demographic structure of C finmarchicus in the Irminger Sea from a field programme during 2001/2002, and the associations between its developmental stages and various apparent bio-physical zones. Overwintering stages were found widely at depth (>500 m) across the Irminger Sea, and surviving females were widely distributed in the surface waters the following spring. However, recruitment of the subsequent generation was concentrated around the fringes of the Irminger Sea basin, along the edges of the Irminger and East Greenland Currents, and not in the central basin. In late summer animals were found descending back to overwintering depths in the Central Irminger Sea. The key factors dictating this pattern of recruitment appear to be (a) the general circulation regime, (b) predation on eggs in the spring, possibly by the surviving GO stock, and (c) mortality of first feeding naupliar stages in the central basin where food concentrations appear to be low throughout the year. We compared the demographic patterns in 2001/2002 with observations from the only previous major survey in 1963 and with data from the Continuous Plankton Recorder (CPR) surveys. In both previous data sets, the basic structure of GO ascent from the central basin and G1 recruitment around the fringes was a robust feature, suggesting that it is a recurrent phenomenon. The Irminger Sea is a complex mixing zone between polar and Atlantic water masses, and it has also been identified as a site of sporadic deep convection. The physical oceanographic characteristics of the region are therefore potentially sensitive to climate fluctuations. Despite this, the abundance of C finmarchicus in the region, as measured by the CPR surveys, appears not to have responded to climate factors linked to the North Atlantic Oscillation Index, in contrast with the stocks in eastern Atlantic areas. We speculate that this may because biological factors (production and mortality), rather than transport processes are the key factors affecting the population dynamics in the Irminger Sea. (c) 2007 Elsevier Ltd. All rights reserved.

Coccolithophore biomineralization: New questions, new answers.

Coccolithophores are unicellular phytoplankton that are characterized by the presence intricately formed calcite scales (coccoliths) on their surfaces. In most cases coccolith formation is an entirely intracellular process - crystal growth is confined within a Golgi-derived vesicle. A wide range of coccolith morphologies can be found amongst the different coccolithophore groups. This review discusses the cellular factors that regulate coccolith production, from the roles of organic components, endomembrane organization and cytoskeleton to the mechanisms of delivery of substrates to the calcifying compartment. New findings are also providing important information on how the delivery of substrates to the calcification site is co-ordinated with the removal of H(+) that are a bi-product of the calcification reaction. While there appear to be a number of species-specific features of the structural and biochemical components underlying coccolith formation, the fluxes of Ca(2+) and a HCO3(-) required to support coccolith formation appear to involve spatially organized recruitment of conserved transport processes.

Coccolithophore biomineralization: New questions, new answers.

Coccolithophores are unicellular phytoplankton that are characterized by the presence intricately formed calcite scales (coccoliths) on their surfaces. In most cases coccolith formation is an entirely intracellular process - crystal growth is confined within a Golgi-derived vesicle. A wide range of coccolith morphologies can be found amongst the different coccolithophore groups. This review discusses the cellular factors that regulate coccolith production, from the roles of organic components, endomembrane organization and cytoskeleton to the mechanisms of delivery of substrates to the calcifying compartment. New findings are also providing important information on how the delivery of substrates to the calcification site is co-ordinated with the removal of H(+) that are a bi-product of the calcification reaction. While there appear to be a number of species-specific features of the structural and biochemical components underlying coccolith formation, the fluxes of Ca(2+) and a HCO3(-) required to support coccolith formation appear to involve spatially organized recruitment of conserved transport processes.

Heavy metal accumulation reflecting natural sedimentary processes and anthropogenic activities in two contrasting coastal wetland ecosystems, eastern China

Due to the impacts of natural processes and anthropogenic activities, different coastal wetlands are faced with variable patterns of heavy metal contamination. It is important to quantify the contributions of pollutant sources, in order to adopt appropriate protection measures for local ecosystems. The aim of this research was to compare the heavy metal contamination patterns of two contrasting coastal wetlands in eastern China. In addition, the contributions from various metal sources were identified and quantified, and influencing factors, such as the role of the plant Spartina alterniflora, were evaluated. Materials and methods Sediment samples were taken from two coastal wetlands (plain-type tidal flat at the Rudong (RD) wetland vs embayment-type tidal flat at Luoyuan Bay (LY)) to measure the content of Al, Fe, Co, Cr, Cu, Mn, Mo, Ni, Sr, Zn, Pb, Cd, and As. Inductively coupled plasma atomic emission spectrometry, flame atomic absorption spectrometry, and atomic fluorescence spectrometry methods were used for metal detection. Meanwhile, the enrichment factor and geoaccumulation index were applied to assess the pollution level. Principle component analysis and receptor modeling were used to quantify the sources of heavy metals. Results and discussion Marked differences in metal distribution patterns between the two systems were present. Metal contents in LY were higher than those in RD, except for Sr and Mo. The growth status of S. alterniflora influenced metal accumulations in RD, i.e., heavy metals were more easily adsorbed in the sediment in the following sequence: Cu > Cd > Zn > Cr > Al > Pb ≥ Ni ≥ Co > Fe > Sr ≥ Mn > As > Mo as a result of the presence and size of the vegetation. However, this phenomenon was not observed in LY. A higher potential ecological risk was associated with LY, compared with RD, except for Mo. Based on a receptor model output, sedimentary heavy metal contents at RD were jointly influenced by natural sedimentary processes and anthropogenic activities, whereas they were dominated by anthropogenic activities at LY. Conclusions A combination of geochemical analysis and modeling approaches was used to quantify the different types of natural and anthropogenic contributions to heavy metal contamination, which is useful for pollution assessments. The application of this approach reveals that natural and anthropogenic processes have different influences on the delivery and retention of metals at the two contrasting coastal wetlands. In addition, the presence and size of S. alterniflora can influence the level of metal contamination in sedimentary environments.