(Table 1) Prey species identified from the scats of Antarctic fur seals (Arctocephalus gazella) on Bouvet Island

Intraspecific differences in the diets of many species of pinnipeds are to be expected in view of the great differences in morphology, life history and foraging behaviour between the sexes of many species. We examined the diet of the Antarctic fur seal population at Bouvetøya, Southern Ocean, to assess intersexual differences. This was made possible by the analysis of prey remains extracted from scats and regurgitations collected in areas used primarily by one or the other sex. The results indicate that both males and females feed primarily on Antarctic krill Euphausia superba with several species of fish and squid being taken, likely opportunistically given their prevalence. Significant differences were identified in the frequency of occurrence of otoliths in scats and the percentage numerical abundance of the major fish prey species in the diet. Adult males ate a smaller quantity of fish overall, but ate significantly more of the larger fish species. The greater diving capabilities of males and the fact that they are not limited in the extent of their foraging area by having to return regularly to feed dependant offspring may play a role in the differences found between the diets of males and females. Additionally, females might be more selective, favouring myctophids because they are richer in energy than krill. The absence of major differences in the diet between the sexes at this location is likely due to the high overall abundance of prey at Bouvetøya.

Distribution of biological, anthropogenic, and volcanic constituents in the San Francisco Bay Coastal System

Although conventional sediment parameters (mean grain size, sorting, and skewness) and provenance have typically been used to infer sediment transport pathways, most freshwater, brackish, and marine environments are also characterized by abundant sediment constituents of biological, and possibly anthropogenic and volcanic, origin that can provide additional insight into local sedimentary processes. The biota will be spatially distributed according to its response to environmental parameters such as water temperature, salinity, dissolved oxygen, organic carbon content, grain size, and intensity of currents and tidal flow, whereas the presence of anthropogenic and volcanic constituents will reflect proximity to source areas and whether they are fluvially- or aerially-transported. Because each of these constituents have a unique environmental signature, they are a more precise proxy for that source area than the conventional sedimentary process indicators. This San Francisco Bay Coastal System study demonstrates that by applying a multi-proxy approach, the primary sites of sediment transport can be identified. Many of these sites are far from where the constituents originated, showing that sediment transport is widespread in the region. Although not often used, identifying and interpreting the distribution of naturally-occurring and allochthonous biologic, anthropogenic, and volcanic sediment constituents is a powerful tool to aid in the investigation of sediment transport pathways in other coastal systems.

Seawater carbonate chemistry and Globigerinoides sacculifer biological processes during experiments, 2010

The effect of carbonate ion concentration ([CO3]) on calcification rates estimated from shell size and weight was investigated in the planktonic foraminifera Orbulina universa and Globigerinoides sacculifer. Experiments on G. sacculifer were conducted under two irradiance levels (35 and 335 µmol photons m-2 s-1). Calcification was ca. 30% lower under low light than under high light, irrespective of the [CO3]. Both O. universa and G. sacculifer exhibited reduced final shell weight and calcification rate under low [CO3]. For the [CO3] expected at the end of the century, the calcification rates of these two species are projected to be 6 to 13% lower than the present conditions, while the final shell weights are reduced by 20 to 27% for O. universa and by 4 to 6% for G. sacculifer. These results indicate that ocean acidification would impact on calcite production by foraminifera and may decrease the calcite flux contribution from these organisms.

Species-specific consequences of ocean acidification for the calcareous tropical green algae Halimeda, 2011

Ocean acidification (OA), resulting from increasing dissolved carbon dioxide (CO2) in surface waters, is likely to affect many marine organisms, particularly those that calcify. Recent OA studies have demonstrated negative and/or differential effects of reduced pH on growth, development, calcification and physiology, but most of these have focused on taxa other than calcareous benthic macroalgae. Here we investigate the potential effects of OA on one of the most common coral reef macroalgal genera,Halimeda. Species of Halimeda produce a large proportion of the sand in the tropics and are a major contributor to framework development on reefs because of their rapid calcium carbonate production and high turnover rates. On Palmyra Atoll in the central Pacific, we conducted a manipulative bubbling experiment to investigate the potential effects of OA on growth, calcification and photophysiology of 2 species of Halimeda. Our results suggest that Halimeda is highly susceptible to reduced pH and aragonite saturation state but the magnitude of these effects is species specific. H. opuntiasuffered net dissolution and 15% reduction in photosynthetic capacity, while H. taenicola did not calcify but did not alter photophysiology in experimental treatments. The disparate responses of these species to elevated CO2 partial -pressure (pCO2) may be due to anatomical and physiological differences and could represent a shift in their relative dominance in the face of OA. The ability for a species to exert biological control over calcification and the species specific role of the carbonate skeleton may have important implications for the potential effects of OA on ecological function in the future.

Effects of seawater acidification on early development of the intertidal sea urchin Paracentrotus lividus, seawater carbonate chemistry and biological processes

The effect of pH ranging from 8.0 to 6.8 (total scale - pHT) on fertilization, cleavage and larval development until pluteus stage was assessed in an intertidal temperate sea urchin. Gametes were obtained from adults collected in two contrasting tide pools, one showing a significant nocturnal pH decrease (lowest pHT = 7.4) and another where pH was more stable (lowest pHT = 7.8). The highest pHT at which significant effects on fertilization and cleavage were recorded was 7.6. On the contrary, larval development was only affected below pHT 7.4, a value equal or lower than that reported for several subtidal species. This suggests that sea urchins inhabiting stressful intertidal environments produce offspring that may better resist future ocean acidification. Moreover, at pHT 7.4, the fertilization rate of gametes whose progenitors came from the tide pool with higher pH decrease was significantly higher, indicating a possible acclimatization or adaptation of gametes to pH stress.

Seawater carbonate chemistry and biological processes of foraminifera, Globigerinoides ruber and Globigerinella siphonifera during experiments, 2011

Specimens of two species of planktic foraminifera, Globigerinoides ruber and Globigerinella siphonifera, were grown under controlled laboratory conditions at a range of temperatures (18-31 °C), salinities (32-44 psu) and pH levels (7.9-8.4). The shells were examined for their calcium isotope compositions (d44/40Ca) and strontium to calcium ratios (Sr/Ca) using Thermal Ionization Mass Spectrometry and Inductively Coupled Plasma Mass Spectrometry. Although the total variation in d44/40Ca (~0.3 per mill) in the studied species is on the same order as the external reproducibility, the data set reveals some apparent trends that are controlled by more than one environmental parameter. There is a well-defined inverse linear relationship between d44/40Ca and Sr/Ca in all experiments, suggesting similar controls on these proxies in foraminiferal calcite independent of species. Analogous to recent results from inorganically precipitated calcite, we suggest that Ca isotope fractionation and Sr partitioning in planktic foraminifera are mainly controlled by precipitation kinetics. This postulation provides us with a unique tool to calculate precipitation rates and draws support from the observation that Sr/Ca ratios are positively correlated with average growth rates. At 25 °C water temperature, precipitation rates in G. siphonifera and G. ruber are calculated to be on the order of 2000 and 3000 µmol/m**2/h, respectively. The lower d44/40Ca observed at 29 °C in both species is consistent with increased precipitation rates at high water temperatures. Salinity response of d44/40Ca (and Sr/Ca) in G. siphonifera implies that this species has the highest precipitation rates at the salinity of its natural habitat, whereas increasing salinities appear to trigger higher precipitation rates in G. ruber. Isotope effects that cannot be explained by precipitation rate in planktic foraminifera can be explained by a biological control, related to a vacuolar pathway for supply of ions during biomineralization and a pH regulation mechanism in these vacuoles. In case of an additional pathway via cross-membrane transport, supplying light Ca for calcification, the d44/40Ca of the reservoir is constrained as -0.2 per mill relative to seawater. Using a Rayleigh distillation model, we calculate that calcification occurs in a semi-open system, where less than half of the Ca supplied by vacuolization is utilized for calcite precipitation. Our findings are relevant for interpreting paleo-proxy data on d44/40Ca and Sr/Ca in foraminifera as well as understanding their biomineralization processes.