Lithothamnion Prolifer Foslie: A Common Non-Geniculate Coralline Alga (Rhodophyta: Corallinaceae) from the Tropical and Subtropical Indo-Pacific

A little-known, but ecologically important non-geniculate coralline, Lithothamnion prolifer, is recorded from a number of tropical Indo-Pacific sites, including Fiji, Australia, Kiribati and Indonesia. The species occurs primarily on vertical walls of caves and overhangs in Fiji and Australia, but was also found as rhodoliths in Kiribati. Lithothamnion prolifer is characterized by the combination of characters which follow. The thallus is extremely glossy, smooth, and rosy coloured. Thalli usually produce complanate protuberances, but protuberances become terete when growing on well lit, horizontal substrata, when unattached, or when growing on loose substrata. Conceptacles occur mainly on the tips of protuberances, and tetra/bisporangial conceptacles are large (to 1300 mu m external diameter, with chambers up to 1100 mu m diameter). The tetra/bisporangial conceptacles are flush or only slightly raised, and often extensive and irregularly shaped (resembling small sori). They lack a raised rim, and have flattened pore plates. The rosette cells surrounding the tetra/bisporangial pore appear somewhat sunken below the surrounding roof cells in SEM, and the cells of filaments lining the pore canals of tetra/bisporangial conceptacles do not differ from the cells of filaments making up the rest of the roof. Old conceptacles persist and become buried in the thallus, and are then usually completely filled in by irregularly arranged calcified cells.

Regulation of Phytoplankton Carbon to Chlorophyll Ratio By Light, Nutrients and Temperature in the Equatorial Pacific Ocean: A Basin-Scale Model

The complex effects of light, nutrients and temperature lead to a variable carbon to chlorophyll (C:Chl) ratio in phytoplankton cells. Using field data collected in the Equatorial Pacific, we derived a new dynamic model with a non-steady C:Chl ratio as a function of irradiance, nitrate, iron, and temperature. The dynamic model is implemented into a basin-scale ocean circulation-biogeochemistry model and tested in the Equatorial Pacific Ocean. The model reproduces well the general features of phytoplankton dynamics in this region. For instance, the simulated deep chlorophyll maximum (DCM) is much deeper in the western warm pool (similar to 100 m) than in the Eastern Equatorial Pacific (similar to 50 m). The model also shows the ability to reproduce chlorophyll, including not only the zonal, meridional and vertical variations, but also the interannual variability. This modeling study demonstrates that combination of nitrate and iron regulates the spatial and temporal variations in the phytoplankton C:Chl ratio in the Equatorial Pacific. Sensitivity simulations suggest that nitrate is mainly responsible for the high C:Chl ratio in the western warm pool while iron is responsible for the frontal features in the C:Chl ratio between the warm pool and the upwelling region. In addition, iron plays a dominant role in regulating the spatial and temporal variations of the C:Chl ratio in the Central and Eastern Equatorial Pacific. While temperature has a relatively small effect on the C:Chl ratio, light is primarily responsible for the vertical decrease of phytoplankton C:Chl ratio in the euphotic zone.

Twentieth Century Delta δC Variability in Surface Water Dissolved Inorganic Carbon Recorded by Coralline Algae in the Northern North Pacific Ocean and the Bering Sea

The oxygen isotopic composition and Mg/Ca ratios in the skeletons of long-lived coralline algae record ambient seawater temperature over time. Similarly, the carbon isotopic composition in the skeletons record delta(13)C values of ambient seawater dissolved inorganic carbon. Here, we measured delta(13)C in the coralline alga Clathromorphum nereostratum to test the feasibility of reconstructing the intrusion of anthropogenic CO(2) into the northern North Pacific Ocean and Bering Sea. The delta(13)C was measured in the high Mgcalcite skeleton of three C. nereostratum specimens from two islands 500 km apart in the Aleutian archipelago. In the records spanning 1887 to 2003, the average decadal rate of decline in delta(13)C values increased from 0.03% yr(-1) in the 1960s to 0.095% yr(-1) in the 1990s, which was higher than expected due to solely the delta(13)C-Suess effect. Deeper water in this region exhibits higher concentrations of CO(2) and low delta(13)C values. Transport of deeper water into surface water (i.e., upwelling) increases when the Aleutian Low is intensified. We hypothesized that the acceleration of the delta(13)C decline may result from increased upwelling from the 1960s to 1990s, which in turn was driven by increased intensity of the Aleutian Low. Detrended delta(13)C records also varied on 4-7 year and bidecadal timescales supporting an atmospheric teleconnection of tropical climate patterns to the northern North Pacific Ocean and Bering Sea manifested as changes in upwelling.