Abstract. By recreating a range of geologically relevant concentrations of dissolved inorganic carbon (DIC) in the laboratory, we demonstrate that the magnitude of the vital effects in both carbon and oxygen isotopes of coccolith calcite of multiple species relates to ambient DIC concentration. Under high DIC levels, all the examined coccoliths exhibit significantly reduced isotopic offsets from inorganic calcite compared to the substantial vital effects expressed at low (preindustrial and present-day) DIC concentrations. The supply of carbon to the cell exerts a primary control on biological fractionation in coccolith calcite via the modulation of coccolithophore growth rate, cell size and carbon utilisation by photosynthesis and calcification, altogether accounting for the observed interspecific differences between coccolith species. These laboratory observations support the recent hypothesis from field observations that the appearance of interspecific vital effect in coccolithophores coincides with the long-term Neogene decline of atmospheric CO 2 concentrations and bring further valuable constraints by demonstrating a convergence of all examined species towards inorganic values at high pCO 2 regimes. This study provides palaeoceanographers with a biogeochemical framework that can be utilised to further develop the use of calcareous nannofossils in palaeoceanography to derive sea surface temperature and pCO 2 levels, especially during periods of relatively elevated pCO 2 concentrations, as they prevailed during most of the Meso-Cenozoic.

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Abstract. By recreating a range of geologically relevant concentrations of dissolved inorganic carbon (DIC) in the laboratory, we demonstrate that the magnitude of the vital effects in both carbon and oxygen isotopes of coccolith calcite of multiple species relates to ambient DIC concentration. Under high DIC levels, all the examined coccoliths lacked any offset from inorganic calcite, whereas in low (present-day) DIC concentrations, these vital effects and interspecies differences become substantial. These laboratory observations support the recent hypothesis from field observations that the appearance of interspecific vital effect in coccolithophores coincides with the long-term Neogene decline of atmospheric CO2 concentrations. The present study brings further valuable constraints on coccolith isotopic compositions by demonstrating the threshold for the absence of vital effects under high DIC regimes. From a mechanistic viewpoint, we show that the vital effect is determined by physiology; growth rate, cell size and relative rates of photosynthesis and calcification, and a modulation of these parameters with ambient carbon availability. This study provides palaeoceanographers with a biogeochemical framework that can be utilised to further develop the use of calcareous nannofossils in palaeoceanography to derive sea surface temperature and pCO2 levels.

Background: The conservation effectiveness of marine protected areas is of substantial dispute. In the Belize Barrier Reef, there are several zones with increasing human activity and harvesting of overexploited species. Marine protected areas are designed to protect endangered species and increase the population size of exploited species. The present study investigated the population and morphological characteristics of Lobatus gigas (Linnaeus, 1758) in the Sapodilla Cayes Marine Reserve (SCMR) at the southernmost tip of the Belize Barrier Reef to estimate the effectiveness of the marine protected area. Results: A total of 693 L. gigas conches were counted over the 7,200 m 2 from 36 transect lines. The densities of juveniles and adult conches in the conservation zone were substantially higher (20.13 and 2.88 individuals/100 m 2 , respectively) than in the general use zone (5.29 juveniles and 0.58 adults individuals/100 m 2). The shell length of adult individuals ranged from 14.4 to 18.5 cm in the conservation zone and from 14.6 to 18.1 cm in the general use zone. A comparison of shell length of juveniles and adults showed no significant differences between the conservation zone (11.39 ± 1.46 cm) and general use zone (11.62 ± 1.24 cm). There was a significant positive correlation for shell length with lip thickness in the conservation zone (Pearson's correlation, r = 0.729, p < 0.001) and general use zone (Pearson's correlation, r = 0.613, p = 0.02). Conclusions: The function and effectiveness of marine protected areas are discussed using the results of the present study that identifies the primary objective which is to ensure a continuous recruitment of valuable targeted species by the protection of spawning stock biomass that is important for the management of marine protected areas in an environmentally sensitive ecosystem.